CA1117339A - Microwave method and apparatus for reprocessing pavements - Google Patents

Abstract

Abstract of the Disclosure Asphalt roads or the like are repaved by heating and decomposing existing pavement with microwave energy and then remixing and recompacting the constituents of the pave-ment, the operations being performed at the original location of the old pavement and in some cases without removing the pavement constituents from the roadbed itself. A microwave energy applicator may be traveled along the pavement in front of remixing, grading and compacting equipment or some or all of the equipment may be integrated into a self-propelled vehi-cle. The vehicle may carry a microwave applicator followed remixed means such as rotary tillers or the like and grading and compaction devices, and may travel continuously down a road which is reconditioned as the vehicle progresses.
Motor generator sets on the vehicle power the microwave sources and the hot exhaust from the motors may be directed to the pavement to supplement the microwave heating and to maintain high temperatures during the additional operations. Appa-ratus is provided for efficiently coupling microwave energy into underlying pavement and for inhibiting the escape of useful for heat treating concrete or the like as well as asphaltic pavement.

Description

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~ack,77-oun~ o the Illv2ntion .
This invention relates to the processln~ of pave-ments at roadways or the like and n~ore particularly to a n~ethod and apparatus for more efficiently and econo~ically repaving, repairing or heat treating pave~ents. In one fo~n, the inventi~n enables the recycling of existing asphalt roads at the roadbed using little or no ne~ paving materials.
The introduction of the auto~,obile as a major means of mass transportation and of autom~tive trucks as an itnpor-tan~ means of reigllt transpoxt has been accompanied ~y a vast expansion of paved highway systems, roads, city streets and the like, Much oi this road syste~ is paved in whole or- -in part with asphaltic compositions and ~uch of it is of ~ly recent origin, Because of this historical situation~
advances in asphalt paving technology have tended to be c~n-L5 centrated on techniques and equipment for new construction rather than on the repaving or repair of existing roads.
Asphalt pavement deterioates with age and as a result of heavy use, A variety of causes ranging from ~he concentrated localized ~tresses imposed on such p~vement b~
heavy veh~les to ground settlem~nt and ground ~ater effects causes the pavement surface to ~ecome meven~ ~ crack a~d to exhibit so-called potholes in small localized areas ~7here the pavement has for practical purposes decomposed. Repair ~-or repaving efforts as hereto~ore practiced have tended to a be essentially adaptations of new construction techniques.
Initial repair steps typically consist of filling crac~s~
surface depressions and potholes withfresh new asphalt mix at the speciic s~all areas in the pavement where this is needed. Patched areas of this kind often do not exhibit the stabili~y an~ durebility o:E the origi.nal pavement and thus rcpeated and usually more widespread patching becornes neces-sary in time. Eventually, when deteriora~ion has progresse~
to a certain stage at least portions of the entire roadway may be repaved.
A typical road repaving operation of this kind has involved ripping up the old asphalt pavement ~hich must then be loaded into trucks and transported to a dump site which is often a considerabl.e distance away. New asphalt hot-mix is then brough~ in, laid in place and compacted in what is essentially a new paving operation with new ~aterial~
. The fact that ~ch of the vast existing asphalt roadway system is just now approaching a stag~ at which sub-stantial repair or repaving will be needed, coupled ~ith certain recent economic developments, is creating a poten~
tial crisis situation which has not been ~idely recogni~ed until very recently.
A gro~ing worldwide scarcity of petroleum deriva-tive products, which includes asphalt, has very recently developed al~d has given rise to a subs~antial escalation o ~.
cost and perhaps a need to allocate the available resources o this kind between various co~eting needs such as energy-production as opposed to road repair. When the high cost of .~ new aspbalt is combined with the labor, equipment and energy costs invol~ed in repaving using known techniques, the re-- s~lting total cost figure appears to rule out any practical possibility of maintaining the vast highway system in the United States of America in a state approaching its present condition. I~no~ geable opinions havc been e~pressed that deterioration of e~isting hight~ay systems is, as a practical matter, almost a certainty. This situation ~Jill of course be further aggravated i~ the num~er of auto~obiles and trucks in use should be further increased as appears entirely lilcely.
To alleviate this situation by bringin~ the cost of highway repair down to a figure within the bounds oE eco-nomic practicality, it has heretofore been proposed to re-cycle existing asphalt pavementO As heretofore conten~lated and as has been carried out to a very limited extent, ~his involves ripping up tlle existing asphalt pave~ent on a road and transporting the chunks of old pavement to a distant processing plant where the pavemen~ is heated to soften the asphalt~ The constituents of the old pave~ent are then re-mixed. The remixed asphalt composition is then transportedbak to the roadway in a heated condi~ion and utilized to repave the road~ay in essentially the conventional manner.
This recycling of existing pavement realizes a ; substantial economy in that lit~le or no new asphal~ and aggregates is needed An additional economic and ecological benefit arises from the fac~ that no dump site for old pave-ment may be required. Because of increasing ecologicaL eon-ce~ns and more intensive land use, suitable du~p sites of this kind are becoming very dificult to find and if suc-cessfully located may be at great distances from the road-paving site thereby further aggravating costs.
The economic savings of recycling asphalt paving ; in the kno~n manner, as briefly discussed above, are largely confined to the savings realized by reducing or eliminating 3~

the n~.ed ~or ne~ asphalL an~ ag~rcgates. ~nder most cir-cumstances at least, no substantial saving is ~ade i~ tlle cos~ of transportation of materials nor in labor or equip-ment costs. ~quipment costs at the processing plant m~y in fact increase some~hat as the type of appar~tus used for heating ne~ asphalt cannot usually be employed to heat re-covered asphalt chunks, portions of which tend to igni~e and to generate large quantities of s~oke pollution if processed in the same apparatus used to prepare fresh hot-mix. In one known recycling plant a specialized hea~ ex-changer resembli.ng a drum mixer is utilized in an arrange-ment which enables isolation of an external combustion chamber from the ~ix.
Partly to reduce ignition and pollution problems o~ the kind discussed above, it has very recently been pro-posed to use microwave energy for heating old asphalt pave-ment chunks at a recycling ylant. Microwa~e energy is a flameless heating medium and is much more rapid than conven~ ~.
: tional techniques as it does not depend on conduction of heat inward from the surace of a pav~ment chunk but instead ~en-erates hea~ internally throughout ~he volume of the substance bei.ng heated. Use of microwave heatin~ for such purposes is itsel~ subject to nany specialized technical problems ~hich must be solved before such a procedure becomes practical~
25 . As one example, microwave tends to be a costly heating tech-: - nique and therefore provisions must be made to assure that a high proportion of the generated microwave energy is con~
verted into heat within the asphalt mix. As anothex example, it is essential that no sizable amount of microwave energy be radiated from the heating zone to the surrounding environ-~ent both for safety reasons and to avoid interference ~it~

~73;~9 other forms of electronic equipment such as radar systems, microwave communication links and the like. Techniques and equipment for utilizing microwave energy to heat other kinds of substance Oll a high-volume, continuous-process basis have here-tofore been worked out, most notably in connection with the large-scale industrial processin~ of food products, and at least to some e~tent these known systems and procedures may be adaptable to reheating of used asphalt pavement in a fixed recyciing plant of the 10 kind discussed above. -~
Reference has been made above to the fact that the conventional repaving processes generally involve ripping up old asphalt pavement and transporting it to a dump site. ~eretofore, this old asphalt pavement has not only been unutilized but has itself added substantially to t:he cost of a repaving operation because of the need to xip up the old pavement and the need for lrucks to transport it to an often distant dump site and further because the dump site may then be rendered useless for other purposes. It has ]ust recently been recognized that recycling of ol~
asphalt pavement need not be confined to road or highway pavements. If practical and economic processes and equipment are available, the vast quantities of old asphalt ; presently occupying old dump si-tes can be converted to an asset. Such dump sites are essentially asphalt mines awaiting practical recovery techniques.
In general it may be said that it has just recently come to be recognized that the reuse of old : asphalt pavement may not only offer sizable economies ., . . ~

: ~ ' 1~3L73;~9 but may in fact be a practical necessity if the quality of existing road systems is to be maintained. At the same time, techniques and specialized equipment for accomplishing such recycling in a desirably efficient and economic manner have not heretofore been developed to an appreciable extent.
The foregoing discussion has dealt primarily with the economic disadvantages of prior techniques and systems for repaving or repairing asphaltic pavement. There are also other problems which are more technological than economic. One is that the bonding between new asphalt put down in cracks, low areas, potholes and the like and the older adjacent pavement tends to be relatively weak due to the fact that heating of the older pavement duriny the patching operations tends to be lirnited to just the exposed surfaces of the old pavement. A similar weak bond is likely to exist where a repaved section of road adjoins old ; pavement.
Still another problem is that hot-mix prepared at

2~ a plant for transport to a paving site must be overheated as some coolin~ during transit may occur. Further, such cooling tends to be uneven throughout the volume of hot-mix and serious temperature differentials may remain even if supplemental heating is provided en route to the paving site or at the site. Consequentlyr adjacent areas of pavement are put down and worked at signiEicantly different temperatures with adverse effects on pavement quality~
Still another problem with conventional repaving and repair techniques results from the need to maintain hot-mix at high temperatures for long periods during

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transport and laying operations and in some cases to heat adjacent surfaces to which the asphalt is to be bcnded. The practical problems of accomplishing -this heating tend to rule out paving operations and all but the most serious repairs during periods of cold or wet weather. In many regions ~uch activities must virtually stop during -the winter The foregoing disGussion has also dealt primarily with roads or other areas formed of asphaltic pavement.
There are related serious problems with surfaces paved wholly or in part with other material. Much o~ the extensive free~
way or throughway systems in the United States of America and elsewhere are basically concrete but very commonly these have sho-ulder strips paved with asphalt and which are subject to `~
the problems discussed above~ Moreover, concrete pavemen-t itself deteriorates with use and age and may require an overlay or application of any of various materials accompanied by a heat treatment, which operations are also subject to very serious economic and technical problems of the general kind discussed above.
Summary of the Inven-tion ~ ccording to one aspect of the invention there is provided a method for recycling existing asphalt pavement comprising the steps of: establishing a microwave energy ~ containment region above said pavement incl~lding positioning ~-; microwave eneryy emitting waveguide means in spaced apart relationship from said pavemen-t -to provide a gap enabling -travelling of said waveguide means without direct contact with said pavement, travelling said containment region along said existing asphalt pavemen-t while concurrently generating heat within the interior of said pavement, to soften the asphalt content -thereof, by directing microwave energy into ~- - 8 said pavement from said containment region while travelling therealong, including distributing said microwave energy substantially uniformly across the width of a strip of said pavement over which said containment region is travelled, suppressing outward propagation of mi.crowave energy rom said containment region through said gap while travelling along said pàvement, subsequently remixing the constituents of said pavement while said pavement is in the softened state, and recompacting the remixed pavement constituents substantially at the original. location thereof to provide renewed pavement therea-t.
According to another aspect of the invention there is provided apparatus for heating pavement in place at a paved surface while travelling -therealong comprising: a vehicle with support means for enabling travel along said pavement, :
rnicrowave applicator means supported on said vehicle for travel along said pavement therewith while applying micro-~` wave energy thereto, said applicator means including a microwave containment structure havin~ an electrically ` 20 conductive top portion spac~d above the underlying surface along which said vehicle travels and having electrically conductive side por-tions extending from said top portion downward toward said underlying surface to define the upp~r portion of a travelling microwave region which is bounded by sai.d top portion and said side portions and ; the underlying area of pavement and by a gap between said side portions and said underlying pavement, said applicator means further including a plurality of waveguides positioned to distribute microwave energy substantially uniformly across said underlying area of said pavement and to generate heat within said pavement substantially uniformly thereacross as 9 _ said vehicle travels along said pavement, means carried on said vehicle for releasing microwave energy into said micro-wave region through said plurality oE waveguides to heat said pavement within said underlying area tnereof while travelling along said pavemen-t, and microwave energy-trapping means for suppressing the release of microwave energy through said gap as said vehicle travels along said pavement, said microwave energy-trapping means being disposed on said vehicle adjacent to said gap in position to receive microwave energy which would .0 escape from said microwave region through said gap beneath said containment structure in the absence of said trapping means.
`~ According to another aspect of the invention there is provided a method for heating pavement at a paved surface comprising: positioning microwave energy emitting means ahove said surface in spaced relationship therefrom to provide a gap -therebetween which enables travel of said means without direct contact with said surface, generatiny heat within said pavement below the surface thereof by directing microwave energy down-; ~0 wardly from said microwave energy emit-ting means into said pavement while tra~elling therealong, includin~ dispersing said microwave energy substantially uniformly across a zone . o said pavement which extends transversely with respect to ~ the direc-tion of travel therealong to cause a substantially - uniform temperature rise across said zone of pavement, and blocking the sideward and forward and backward escape of microwave energy through the gap between said microwave energy reyion emitting means and said pavemen-t while travelllng tl~erealong, at least in part by reflecting the upwardly directed component of outwardly propagating microwave energy in a downward direction to cause absorption of the reflected energy within -the underlying surface thereby causing a progressive attenuation of microwave energy intensi-ty in the outward direction within said gap.
According to yet another aspect of the invention there is provided in a method for heating pavement wherein microwave energy produced by a first source of heating energy is direc-ted downward into said pavement to generate heat internally and instantaneously within the subsurface intexior region of said pavement, and wherein said microwave energy heats a deeper region of said pavement more strongly than the uppermost region thereof -thereby tending to produce an inver-; ted temperature gradient in said uppermost regicn the further steps comprising operating a fuel consuming motor to drive a ~enerator to produce electrical energy for conversion to said microwave energy, and counteracting said inverted temperature gradient while reducing nonproductive energy dissipation by transmitting thermal energy from the exhaust gases of said motor to the surface of said pavement to supplement the microwave heat.in~ of said uppermost region of said pavement.
~ccording to yet another aspect of the invention ; there is provided in a pavemen-t heating apparatus having energy applicator means for generating heat within the interior of pavement over which said applicator means is disposed by microwave irradiation of said pavement, -the improvement comprising: surface heating means -for applying additional heat clirectly to the surface of said pavement over which said energy applicator means is disposed, wherein said energy applicator means includes a housing having a top and downwardly extending sides formed of electrically conductive ~0 material fox defining a microwave and ho-t gas containment region adjacent said surface o said pavement~ at least one ~ 11- ' ' 733~

waveguide for releasing microwave energy into said containment region, and at least one condui-t or transmittiny hot gas into said housing, and microwave energy trapping means secured to the lower portions of said side walls of said housing for suppressing the outward emission of microwave energy from under said side walls when said housing is spaced above said surface of said pavement by a gap which would otherwise allow the outward release of microwave energy.
This invention provides, at least in preEerred forms, methods and apparatus for recycling pre-existiny asphalt pavement in a highly economical and efficient manner, basically by performing the recycling operations at the site of the existing pavement and in many cases without removing the pavement from the roadbed or other paved surface. Certain preferred forms of the invention are also applicable to the maintenance of concrete highways or the like and to the ; recovery of discarded asphalt from dump sites.
~ In the prac-tice of one preferred form of the ; invention, successive increments of the old asphalt pavement .
2U are rapidly decomposed in place by heating with microwave energy and the constituents are then remixed at the site, in place on the roadbed in some cases. The hot remixed ;~
constituents are ~hen graded and recompacted. It is thus possible to progress continuously down a deterioriated high-way leaving behind a repaved high-quality surEace with characteristics similar to those of a newly constructed highway. Little or no new asphalt and aggregates are needed al~d very substantial additional cost reductions are realized as the transporting of materials between the work site and a dump and ~etween a mixing plant and the work site is greatly reduced or eliminated. The related need -Eor fleets of trucks, lla -31L9 ~L733~3 rippers, loader vehicles and the like is correspondinglyreduced or eliminated. The need fcr dump sites for old paving is eliminated and the invention may in fact be adaptecl to recover asphalt mix from old sites of this kind.
In one preferred form of the invention where fuel~
consuming engines are used to drive electrical generators to power the microwave sources at the wor~c site, still further cost and energy economies are accomplished by utilizing the hot exhaust of the engines to supplement or to maintain the 1~ heating effects of the microwave energy.
The invention, in preferred form~, may be utilized to repair and restore asphalt shoulder strips of primarily concrete roads and may also be adapted to salvage road surfaces or the like formed of concrete which has deteriorated.
An overlay of asphalt or various sealants may be applled to -the concrete and may be heated in place by the apparatus of the present invention and the surface may then be periodically reworked as necessary in accordance with the invention to maintain a high-quality surface for a very extended period of time.
Apparatus in accordance with the invention includes applicator devices for efficiently coupling microwave energy into pre-existing underlying pavement to heat the pavement - extremely rapidly and uniformly and further includes struc-tures for preventing the escape of microwave energy Erom the heating region at the pavement.
One preferred form of the apparatus for recycling asphalt pavement includes a preferab]y self-propelled vehicle assembly which may be articulated into sections and which carries an applicator for directing microwave energy downward to decompose the underlying pavement and which fur-ther carries remixing mechanism exkendiny downward into the decomposed ~ - llb -.

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pavement and which may also carry one or more grader bladesfollowed by recompaction devices. Such a vehicle assembly may be traveled down an e~isting road a-t a slow rate of speed to repave successive portions of the road as the vehicle progresses.
One or more engine-driven generators carried on the vehicle assembly supply electrical power to operate the microwave source or sources and in a preferred form, the hot exhaust from the engine may varicusly be utilized to supplement the microwave heating action at the underlying pavement, to continue to heat the pavement constituents ; during the subsequent remixing operations, to maintain a supply of supplemental constituents carried on the vehicle at an elevated temperature, to heat compactor surfaces to ~ avoid adhesion of asphalt thereto, or to accomplish any ; combina-tion of ~hese results.
Accordingly it is an advantage of this invention, at least in preferred forms, that it can provide more efficient and economical methods and equipment for recycliny asphalt pavement.
It is an advantage of the invention, at least in preferred forms, that it can reduce materials and hauling costs in connection with -the repaving of roadbeds and other - surfaces with asphaltic compositions.
It is ano-ther advantage of the invention, at least in preferred forms, that it can provide methods and apparatus for repaving or repairing asphalt roads and the like with less consumption of costly matexials and energy and to reduce pollution and other adverse ecological effects in connection with such operations.
It is another advantage of the invention, at least ~- llc -. .

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in preferred forms, that it can provide methods and apparatusfor improving the quality of bonding of newly mixed or remixed asphalt with adjacent areas of old pavement in the repair and reconditioning of roadbeds or other paved surfaces.
It is still another advantage of the invention, at least in preferred forms, that it can provide for efficient utilization of microwave energy in the repaving or repairing of roadways and other paved surfaces while avoiding the broadcasting of microwave frequencies from the work site.
It is another advantage of the invention, at least in preferred forms, that it can provide methods and apparatus for restoring and maintaining concrete highways and the like.
The invention, together with further objects and advantages thereof, will best be understood by reference to .
the following description of preferred embodiments taken in con)unction with the accompanying drawlngs.

~ ~ ' ;~ , `` 3L~a3~33~9 ; _rief De_c iption of _he rawings In the accompanying drawings:
Figure l is a graphical depiction of temperatures reached by sa.nples of certain materials as a function of time upon similar exposures to microwave energy, Figure 2 is a graphical depiction of temperatures ~i reached by a diverse variety of road-paving materials upon being heated in a 500-watt microwave oven, operating at 2450 megahertz, for periods of two minutes, 10Figure 3 is a block diagram illustrating successive steps utilized in the recycling of deteriorated asphaltic pavement in accordance with the method of this invention, 1 Figure 4 is a block diagram illustrating additional `;l; steps which may be employed in t.he practice of the invention, 15Figure 5 illustrates the practice of the method of this invention utilizing largely known forms of equipment, ~`
;. Figure 6 depicts the practice of this invention util.izing a paver apparatus of known construction, `;
i Figure 7 is a broken-out side elevation view of a ;
first form of microwave applicator vehicle for heating and decomposing asphalt pavement in place, Figure 8 is a view of the underside of the vehicle of Figure 7 taken along line 8--8 thereof, ;
Figure 9 is a broken-out frontal view of a second ...
form of mi.crowave applicator vehicle for heating and decomposing old asphalt pavement, Figure lO is a view of the underside of a corner portion of the vehicle of F`igure 9 taken along line lO-10 thereof, ' -`, 33~

Figure 11 is a view taken along line 11-11 of ~igure 10 illustrating details of a micro~ave energy barrier, Figure ~ is a broken--out perspec~i~e view of a front corner portion of a third form of microwave applicator vehicle having a modified form of ~icrowave energy-trapping means, Figure 13 is a partial cross-section vlew ~aken along line 13-13 o Figure 12, Figure 14 is a section view taken along line 14-14 of Figure 13, Figure 15 is a broken~out perspecti~e view of the le~t rear corner of still another form of microwave energy applicator vehicle, Figure 16 is a side elevation view of a tiller compactor vehicle for use in the practice of the invention, . Figure 17 is an elevation section view of the tiller compactor vehicle o~ Figure 16, Figure 18 is a cross-section view o a portion of the vehicle of Figure 17 ~aken along line 18 1~ the~eo~
F~gure 19 is a side eleva~ion view of a ~arge road paving re~ycli.ng system utilizing certain component vehicles similar to those depicted in preceding ~igures, Figure 2~ is a side elevation ~iew of a modified form of large road paving recycling sy~tem, Figure 21 is a plan view of the syste~ of Figure 20 Figure 22 is a side elevation view of a pavement surface resetting vehicle, 13a -~ 33~

Figure 23 is a plan vie~ of the vehicle of ~ig-ure 22, Figure 24 is a side elevation view of an asphalt patching and resetting vehicle, Figure 25 is a side elevation view of the vehicle of Figure ~4 Figure 26 is a side elevatiQn view of sti.ll another large road repaving system, and Figure 27 i.s a plan Yi.eW o tl~e system o ~igure 1~ 260 - - 13b ~

Description of the Preferred Embodiments In accordance with the present invention, deteriorated asphalt pavement is decomposecl by being heated in place at its original location and is then remixed and relaid also at the original location. Compared with repaving in the conventional manner by mechanically breaking up old pavement, trucking it to a dump site and then trucking in and re]aying new paving mix, very pronounced cost reductions and savings in energy consumption, labor, land and equipment needs are effected for the reasons previously discussed.
To fully reali~e these objectives, on-site pavement recycling in accordance with the invention re~uires that the heating and decomposing of the old pavement in place be accolnplished at least in part with a heating medium which has not heretofore been used -for such purposes, specifically by directing microwave energy into the existing pavement at the roadbed or the like. Other heating techniques are comparatively very slow and uneven in efEect as heat, produced - outside the pavement by burning a Euel for example, can be applied only to the sur~ace of the pavement and must then be transferred inward to the interior oE the old pavement by conduction. Heat transfer by conduction is a relatively slow process and inherently gives rise to pronounced temperature gradients within a solid substance such as old pavement. In `~
25 contrast, microwave energy penetrates virtually instantaneously into old pavement and very rapidly generates heat not just at the surface but throughout the interior voluMe of the pavemellt.
For the present purposes, microwave energy may be defined as radiant electromagnetic energy having a ~requency ., I

within the range from about 400 megahertz (M~iZ) to about 300,000 MEI~. As a practical matter, governmental authorities I ;
in any given region usually allocate certain specific frequencies within the total mi~rowave band for various types of usage, such as communications links, radar systems, industrial processing and others. Thus the references herein ~ ;
made to the specific ~requencles of 915 MHZ and 2450 MHZ, which are the two frequencies currently assigned to industrial microwave equipment in the United States of America, should not be construed as necessarily meaning that these are the best or only suitable frequencies from the strictly technical standpoint nor should they be considered as limitative oE the scope of the invention.
Microwave sources, such as magnetron tùbes or the like, suitable for producing microwave frequencies at high power outputs are known to the art and have been widely used for such purposes as communications systems, radar systems and for heating of substances ranging from food products to the curillg of plastics.
At first conslderation, microwave energy migh~ ;
appear to be ill-suited to the heatlng of asphalt pavement Aside from the difficulties of efficiently coupling such energy into an exposed roadway or the l1ke while preventing broadcastlng of such energy outward from the work site, testing has shown that microwave energy couples to pure asphalt so weakly that it mlyht be consldered to be almost transparent to radiant mlcrowave energyO
Dlfferent substances dlffer strongly ln their capaclty to absorb mlcrowave energy and to thereby convert such eneryy lnto lnternal heat. The extent to which microwave -l5 J

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energy is absorbed or coupled into a substance is dependent on certain atomic or molecular properties of the substance in relation to the microwave frequency or wavelength and as noted above the efficiency of the absorption process in pure asphalt is extremely poor. By way of contrast, the absorption of microwave energy by water molecules is a relatively effici~nt pl^OCeSS and ln many prior usages where substances have been heated with rnicrowave energy, such as in cooking food products for example, it is assumed for practical purposes that heating occurs primarily by interaction with the water content of the substance. Figure 1 is a graph illustrating the temperatures reached by a sample of pure asphalt and also by a sample of water during similar exposures to microwave ellergy for a period of several 15 rninutes. The relative inefficiency of heating of the asphalt lij as compared to the heating of water is readily evident.
Figure 1 also illustrates the temperatures reached by microwave heating a sample of old asphalt pavement under essentially the same conditions. Surprisingly, there is not only a highly efficient production of heat in such pavement but it is in fact markedly more efficient than the heating of water by microwave. As pure asphalt is very unresponsive to microwave energy, it may be inferred that microwave is coupling strongly to the other constituents of the pavement which are rock and sand particles of various sizes collectively known as aggregates. This is ln itself of considerable interest since the elements silicon and oxygen constitute almost three-fourths of the cornposition of rocks in the earth's crust and a well-known rock constituent formed of these elements is the mineral quar~z. ~uartz couples so poorly ~o microwave energy that it is often us ed to form energy transparent wi~dows in microwave syste~s. Never theless, experiments have shown that microwave energy couples extremely strongly to rock partlcles of any of a variety of types th~t are commonly used in pavement. For com~arison purposes, Figure 1 also illustrates the heating.
effect on a typical sample of 1/2 inch (1.3 em~) diameter rock gravel of a microwave exposuxe s;milar to that used.
to obtain the data for pure asphalt and or water.
Figuxe 2 illustrates the heating e~fect o~
microwa~e energy exposure on a diverse group of different road repair rock san~les obtained from various di:~ferent loca~ions in the geologically diversified state of Cali~or-nia and in Nevada and further illustrates the compara~ive ~ degree of heatirlg oE pure asphaltS quar~z and water under ; the same condition~. It may be seen that the efficiency of microwave heating is exceedingly high ~or all thes~ varyin~
types of aggregate and for a typical sample of old asphalt 20 paving and for a sam~?l.e of concret:e a~ well.
The reason for the demonstrated high efficieucy ofmicrowave heatirlg o a varie.ty o roc~ types is belie~ed to bc that the el~ments silicnn and oxygeu, in addition to comr bining to fonm quartz (SiO2~ also combine with other element~
to form the group of mirlerals kno~n collectively as s;licates which constitute over ninety percent of the earth's crust~
It may be inferred from the data o ~igure 2 that microwave couples strongly to silicates as opposed to quartz~ The fundamental molecular structure of all silicates includes a tetrahedron made up of a silicon atom at the center and oxygen atoms at each of the four corners. The silicate crystal structures are apparently polar dielectrics with fairly high values of dielectric permittivity (k). A high value of dielectric permittivity indicates that a large displacement of polarizing charges occurs in a crystal ;~ structure in the presence of the voltage stresses imposed by microwave fields and this is the process by which microwave energy is transformed into heat in a dielectric substance.
If a sample of old pavemen-t formed only of asphalt and extremely pure quartz aggregates could be located and tested, it is possible that less efficient heating would be observed but the data of Fiyure 2 indicates that such ` pavement, if it exists at all, must be uncommon.

The Eact that microwave energy heats rocks faster than it heats water as depicted in Figure 1 does not mean that rock materials absorb more energy than water in a microwave field. This seeming contradiction may be explained by the ~act that the specific heat of water, which by definition is (1.0), is much higher than that of rocks. Most rocks have a - specific heat of around (0.2) and this means that a yiven microwave input will heat about five times more rock aggregate than water to a given temperature.
Considering now the steps involved in the practice of the invention as applied to the repaving of a deteriorated ; asphalt road, with reference to Figure 3, the existing pavement 11 is heated by directing microwave energy into the pavement at the roadbed 12 to the extent necessary to heat the composition to the point where the asphalt becomes liquid or T-`,' . ., semiliquid. As discussed above, such heating probably occurs initially within the aggregate component of the paving, but heat is rapidly transferred to the asphalt, Heating to temperatures at or above about 170F. (77c.) is in most cases S suEficient for this purpose although there is some variation depending on the exact composition of the old pavement. When heated to the point where the asphalt binder becomes at least semiliquid, the o]d pavement loses cohesion and may readily be crumbled.
ln ~fter the decomposition of the old pavement by heating, the original constituents are then remixed to ~, redistribute the asphalt and to reduce the constituents to a loose mass which can be reworked. At this stage some supplementary new asphalt, aggregates or pavin~ oils may be added in if desired although this is by no means always necessary. In many cases, it is Eound that the lower portions of old pavement contain relatively morle asphalt than the upper portions and remixing redistributes the asphalt to produce a desirable composition throuyhout.
As will hereinafter be described ln more detail, this remixing can be accomplished by stirring, tilling/ raking ;
or other operations right at the roadbed so that the pavement constituents remain substantially at their original location ~` on the roadbed. Alternately, the decomposed pavement may be briefly lifted from the actual roadbed 12 by a conveyor or the like, as will hereina~Eter be described in more detail, for remixing and may then be returned to the roadbed but in either case the remixin~ operations are preferably conducted at the work site and without transporting material any substantial , ~`
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distance in trucks or the like.
Subsequent to the remixing operations and while the pavement constituents remain decomposed and at an elevated temperature, the material is then graded. Subsequent to the grading operation the mix is recompacted on the roadbed. The result, upon cooling and hardening of the pavement constituents, is a high-quality, smooth repaved roaclway 11'.
While the above-descxibed process may be accomplished by performing the several steps in sequence at a given selected small area of the deteriorated road 11, there are advantages in many cases to performing each of the steps concurrently while slowly progressing continuously down~ the deteriorated road 11 as indicated by arrow 15. If the microwave heating step is performed while traveling in this manner~ sucessive increments of the deteriorated pavement are decomposed while successive increments of the previously decornposed pavement are being remixed~ The grading and compacting operations may then be progressed clown the roadway in an essentially similar manner. Examples of apparatus for accomplishing the several operations on a simultaneous and continuous basis wi~l hereina~ter be described.
It has been pointed out that one of the advantages of the process i~ a marked reduction in energy consumption relative to conventional repaving techniques. One major way by which the process of Figure 3 accomplishes such a reduction is by cJreatly reducing or eliminating fuel requirements for transporting materials back and forth between the work site and a dump and between the work site and remo~e aggrec~ate sources and asphalt plants. Figure 4 ' schematically illustrates a further refinement of the process in which still greater -~uel usaye eEficiency and certain other advantageous results are realiæed.
Referring now to Figure 4, there is usually no pre-existing source oE electrical power available at the work ~ site to operate the microwave source or sources 13.
'i Consequently one or more electrical generators 14 are provlded and these are in turn driven by one or more fuel-consuming engines 16. Engines 16 may variously be piston engines of the form which operate on diesel fuel, liquefied natural gas or gasoline for example or may be turbine engines which also operate from similar Euels but in any case it is characteristic oE such engines that much of the energy content of the consumed fuel is normally wasted in the ~orm of heat discharged in the exhaust of the engine.
In the process as depicted in Figure 4 much of this discharge heat is recovered and utilized for productive purposes.
In particular, at least a portion of the hot , 20 exhaust from engines 16 may be directed to the und~rlying asphalt pavement 17 to supplement the heating effect of the microwave energy thereon. The hot e~haust may be directed at the pavement for this purpose in the same region where the microwave is being applied and it may also be directed at the decomposed pavement constituents during the remixiny stcl(-1e to maintain a desirably high temperature duriny remixing. Portions of the exhaust heat may also be used to maintain the surfaces of compaction devices at an elevated temperature to inhibit the adhesion of pavement constituents ~3L7331,~

to such surfaces during compaction operations. As illustrated in Fiyure 4, the hot exhaust may be utilized for any one of these purposes or for any combination of such purposes. As fuel-consuminy engines ordinarily discharge and waste, in the form of heat, as much as 80% of the energy content of the Euel~ the savings of fuel resources and consequent repaving cost reductions which may be realized by utilizing discharge heat from the engines are substantial.
In the specific form of the process illustrated in Figure 4, a first remixing step is followed by the application of supplemental asphalt to the pavement constituents and then additional remixing is performed.
Where such supplemental paving constituents are present, another portion of the hot exhaust from the engine 16 may be used to maintain the supply of supplemental asphalt or the like in a heated condition as illustr~ted in E`igure 4.
To facilitate any or all of the exhaust heat utilization steps described above, a valve 19 may be present in the exhaust line o~ engine 16 and a series of subsidiary ~alves 21 may also connect to the exhaust line to enable selective control of the direction of hot exhaust to any of the work zones described above.
rn many situations it is preferable to use ; integrated equipmel-t systems specifically designed to perform the above-described method and examples of such systems will be described. However/ for small projects or where an integrated equipment system is not available, it is also possible to realize much of the advantages of the process by using known forms of construction equipment for ;

;33~

performing certain of the steps. In particular, the remixing, grading and compacting operations may, iE desired, be performed with existing equipment available to the construction industry. Suitable apparatus Eor heating and -~
decomposing pavement with microwave energy while traveling down a roadbed or the like is an exception as no device suited for this purpose has been heretofore known to the art.
Where existing construction equipment is to be used to the extent possible, as illustrated in Figure 5, a rnicrowave applicator 22 may be traveled slowly down a deteriorated asphalt road 23 either by self-propulsion means on the microwave applicator vehicle or, as in this example, by being towed by some other available powered vehicle such 15 as a tractor 24. Suitable detailed constructions for the ;
microwave applicator 22 will hereinafter be described, The -~
remixing operation may then be performed by means such as one or more powered rotary tillers 26 which follow along behind the microwave applicator although certain forms of plows, rakes and the like may also be adapted for this purpose. Regrading may then be accomplished by a motor grader 27 following the tiller. Finally, recompaction may be accomplished by a roller 28 or other known compaction devices traveling along behind the grader.
The utili~ation of a series of self-propelled exis-ting .ypes of construction vehicle as depicted in Figure 5, is not necessarily the most efEicient technique for practice of the invention although it has pronounced advantages over conventional repaving operations Eor the reasons hereinbefore discussed. Where the repaving 3~ ;

operations are to be continued over a long period of time -to recondition a large amount of pavement, it may be preferable to utilize one of the known forms of selE-propelled integrated pavers to perform the remixing, grading and compaction steps. A paver 26 of this kind as depicted in Figure 6 may contain and carry the necessary mechanism for mixing, laying, grading and compacting asphalt pavement, suitable detailed constructions for such apparatus being known to the art. In one known form these large pavers 29 include scoops 31 on an endless conveyor cr elevator 32 at !
the front of the vehicle which carries material up into the paverO The elevator 32 has heretofore been used for picking up fresh asphalt mix which has been deposited from trucks in a windrow on the roadbed along which the paver travels but may be used to lift old pavement which has been decomposed by the techniques of the present invelltion.
In the practlce oE the present invention as illustrated in Figure 6, the microwave applicator vehicle 22 may again be traveled continuously along a deteriorated road 23 to heat and decompose the old pavement and may be followed by the paver 29 with the conveyor 32 of the paver being utilized to pick up the hot decomposed old pavement behind the microwave applicator for remixing, relaying, regrading and recompaction.
In rnany cases, the method may be most efficiently practiced by making use of highly specialized new forms of integrate~ road-paviny recycling systems and examples c~E
such apparatus will hereillafter be des~-ibed in detail.

Regardless of whether older types of e~uipment or a new road~
paving recycling system is used, it is necessary to have apparatus suitab.Le for directing large amounts of microwave power into underlying pavement, preferably while traveling along the pavement, and this presents several serious -technological problems.
Prior microwave heating devices or microwave ovens were designed to heat substances whlch can be physically moved into an internal region which is either fully surrounded by electrically conductive material in operation or which is traversed by a conveyor travellng through microwave trapping devices at each end of the internal heating chamber. This assures efficient use of m.icrowave cnergy and avoids the broadcasting or release of any significarlt amount of microwave energy out into the surrounding environment. Escapin~ microwave energy can constitute a safety hazard and can interfere with varlous , ;
forms o.E distant electronic equipment by creating interfererlce effects. An efficient transfer of energy from the microwave generator or source into the substance to be heated is much more easily arranged for in these conventional forms o:E microwave heating systems. The substance to be heated may either be situated at a specific optimum geometrical location relative to the microwave-transmitting means such that close coupling in the electrical sense occurs or, as in the case of home microwave ovens for example, the substance to be heated may be essentially surrounded by electrical conductive material so that microwave energy which initially passes through the substance without being transformed into heat or which is initially directed away from the substance will be repeatedly reflected back and forth and by the conductive chamber walls and will make many passages through the 733~ `~

substance until it is eventually absorbed and converted to heat. These known forms of microwave heating device having internal heating chambers are unsuited for heating old road pavement in place on a roadbed. For that purpose, a specialized applicator must be provided which effieiently couples microwave energy into an underlying surface, preferably while txaveling therealong and while preventing escape of any significant amount of mircowave power.
fi~st example of a suitable microwave applieator 33 of this kind is depicted in Figures 7 and 8 of which Figure 8 constitutes a view of the underside of the applicator structure shown in side elevation in Figure 7.
Applieator 33 may have a high-strength rectangular frame 34 formed of steel channel members or the like and which is supported above the old pavement 36 hy road wheels 37 at each corner. The road wheels 37 may be pivotable about vertieal axes with the front road wheels being eoupled to a swingable towing hiteh 39, situatèd at the eenter of the front end of the vehicle, through conventional wagon steer linkage 38 in order to enable the applieator to accura-tely track the vehicle which tows the applicator. If the applicator 33 is designed to be a self-propelled vehicle, powered and steerable road wheels may be provided.
Microwave energy will not pass through an electrically conductive wall. Except under specialized circumstances, it will not propagate through an opening in such a wall which is substantially smaller in all transverse dimensions than the wavelength of the microwave energy.
Wilile some microwave energy may be transmitted through an opening in a conductive wall if the opening has a maximum ''~.',''i~

33~
, transverse dimension approaching the wavelength of the microwave energy, the extent to which thls occurs decreases as the length of -the opening in the direct on of microwave propagation increases. There exists a configuration for openings of this kind which constitutes what is known as a cut-off ~aveguide and which effectively blocks release of microwave energy. In general, a cut-off opening must be longer in the direction of energy propagation as the largest transverse dimension of the opening becomes closer to the Io wavelength of the microwave energy.
; Still another means of blocking the propagation of microwave energy involves disposing a volume of electrically nonconductive material of certain so-called lossy types in the path of the snicrowave energy. Such materials do not reflect microwave back towards the region from which it arrived, as in the case of electrical conductor containment structures, but act instead to absorb the microwave energy by converting it to heat. Not all nonconductive materials are suitable for this purpose as microwave energy couples strongly to certain nonconductors and very weakly to others.
As previously discussed, nonconductive materials which are efficient microwave absorbers are in general those which have a relatively high dielectric permittivity factor (k).
Water is osle such substance. It is of particular interest to the present invention that asphalt pavement is a highly lossy material although pure asphalt is a very poor absorber as previously discussed.
These various means of preventing the spread of microwave energy from a predetermined region have been briefly reviewed above inasmuch as the applicator 33 of .

~igures 7 and 8, as well as certain other applicators to be hereinafter described, makes use of e~ch of these techniques for defining a microwave containment reO;on 41 w.i~hin the applicator vehlcle 33 and which extends fo. several inch~s downward through the underlying pave~ent 36.
To block upward propagation of microwave energy from region 41~ rectangular plat~orm panel 42 having a~
least a lower surface formed o electrically conductive mA-terial is secured to ~xame 34. A side panel h3, also formed 10 at least in part of electrically conductive mate~ial, extend~
downwardly along each side o fra~e 34 and platform pancl 4 to block the propagation of microwave energy from region 41 in lateral directions. As the deteri~rated pavemEnt 36 over which t'ne ve~icle travels m~y exhibit som~ surEace irregu~
larities, side panels 43 cannot usually extend all the way to the underlying pavement 36 but mstead a small gap 44, suficient to accommodate to such iirregularities, must be provided bet~ecn the side panels and the pave~ent. This gap is preferably kept as small as is consis~e~t with enabling travel of the vehicle over the pavement and may typically be as small as 1/4 inch (0.6 cm~) in some instances as road sur~
~aees, even in deteri~rated conditlon~ are often highly flat.
If necessary ~o accomm~date ~o pavemen~s of di~erent rough-ness, the pivot ~upports 40 of road wheels 37 may be of the vertically adiustable form in order to raise and lower the frame and side panels of the vehicle as necessary.
The presence o~ even a small gap 44 betwee~ the side panels ~3 and pavement 36 would, in the absence o~ urther structures~ tend to allow the sideward release of nucxowave energy from reglon 41~ Microwave trap structures s~itable for blocking such release of energy will be hereinafter - described.
Outward propagation of microwave energy frorn region 41 in the forward and backward directions, with respect to the direction of travel oE the vehicle, is bloc~ed in part by transverse channel members 46 secured to the underside of the front and back ends of frame 34~ the channel members beiny formed of electrically conductive material. Secured below transverse members 46 are transverse electrically conductive trap housing members 47, of inverted U-shaped cross section, which extend still further downward towards the underlying pavement 36. Thus frame 34, together with channel members 46 and trap housings L5 47 collectively form electrically conductive front and back walls of micxowave region 41 for block.ing release of microwave energy in the forward and backward directions except at the small gap 44 between the lower end of housings 47 and the underlying pavement 36.
~ flat rectangular open-centered base panel 43 formed of electrically conductive material is secured at the underside oE the vehicle, the outermost side edges of the ;:~ base panel being secured to the lower edges of side panels . ;~
43 and the forward and rearward edges of the base panel being secured to the lower edge of the innermost portions 49 of trap housings 47. The rectangular central opening 51 of base panel 48 defines a microwave application area at the underlying pavement 36 while the xegion directly beneath the base panel 48 constitutes a microwave energy-trapping region as wlll hereinafter be discussed in more detail.
.

-29- .

To couple microwave energy into pavement 36, a plurality of waveguides 52, of the type known as leaky waveguides, are disposed within region 41. The waveguides 52 are oriented -transversely with respect to the path of travel of the vehicle in this e~ample of the invention and are disposed against each other in paraIlel relationship to form a waveguide assembly 53 which has a width and length slightly less than the width and length of the opening 51 of base panel 48 so that the ends and sides of the waveguide assembly in conjunction with opening 51 of the base panel define a rectangular gap. Waveguides 52 in this example are of the rectangular cross section form and a microwave enercJy emitting slot 54 extends lengthwise along the underside o~ each waveguide. Slots 54 are of progressively diminlshing width from one end of the associated waveguide 52 towards the other in order to ec~ualize the emission of energy at successive portions of the waveguide thereby accommodating to the fact that energy is coupled into one end of the waveguide. The slot is of 20 minimum width at the end closest to the energy source. As is known to those s~illed in the art, other slot configurations may also be used to achieve a similar result in a lea~y waveguide.
Adjacent ones of the waveguides 52 of assembly 53 are reversed end to end so that the ends of slots 54 of greatest width of alternate ones of the waveguides are closest to one side of the vehicle while the corresponding ends of the intervening waveguides are closest to the other side of the vehicle. Each waveguide 52 is excited by a magnetron tube 56 or other suitable microwave generating , -30-source of any of the several forms known to the art. The maynetron tube 56 at each waveguide is disposed above the end of the waveguide at which slot 54 is oE minimum width.
Thus, in this example, the magnetron tubes 56 are arranged in two parallel rows each row extending along an opposite side portion oE the waveguide assembly 53. The magnetron tubes 56 may be supported directly on the top surfaces of the associated waveguides 52 if desired and the waveguide assemhly 53 may be fastened to support members 57 which extend in the direction of travel of the vehicle and which have ends secured to transverse channel members 58 which are in turn fastened to the upper surEace of base panel 4~.
The above-described supporting structure for the waveguide assemb1y 53 is preferably proportioned -to situate the lower surfaces oE the waveguides as close as practical to the underlying pavement 36 taking into account the ; possibility of small irregularities in such pavement.
Thus, the lower surfaces of the waveguides may be spacecl above the roadbed a distance corresponding to that of the gap 44 as previously described. Close disposition of the waveguides 52 to the pavement 36 in this manner enables the waveguides to fullction largely as power couplers rather than as power radiators. In such an arrangement, the underlying highly lossy pavement 56 effectively functions as a dummy load for the magnetron tubes 56. This relationship may be unique in microwave heating systems in that the dummy load to which the microwave source is closely coupled for impedance matching purposes is itself the substance which is to be heated.

Electrical power or operating the magnetron tubes 56 may be transmitted to the applicator 33 through a cable , -31-connec.ing witll anot~er ve'nicle ~J~iCil ~0~`75 the applicator~
e~am~les of such systems being llereina,ter described. In the c~iamplc o,~ Figures 7 and ~, the ap21ica~or 33 carries its o~ power source suc~ as an engine 59 drivi~g an elec-trical generator 61 both of which may be disposed on the vehicle on top of frame 34 and platform panel 42. A power supply 62 of one of the suitable forms kno~n to the art is carried on platform panel 42 and is ~lectrically coupled to generator 61 through a cable 63 and to each magnetron tube : 10 56 tltrough a series of conductors 64 which transmit operating voltages to the magnetron tubes 56.
Engine 59 may variously be a piston engine or a turbine en~ine operating on a suitable fueL such as diesel oil, gasoline or liquefied natural gas. Engines of any o~
these types ordinarily waste a large portion of the energy content o consumed fuel as sizable quan~ities of heat are discharged to the surrounding environment largely through the discharge of ho~ exhaust gases, Fuel ma~ be conserved and operating costs may be significantly reduced in the present instance by utilizing this heat energy for produc-tive purposes, In the appli.cator vehicle 33, ducting 66 is provid-ed.to channel the ~ot exhaus~ gas of engi~e 5~-thrQug~ .
a series of small openings 67 in top panel 42 leading into ; the microwave region 41. To avoid release of micro~ave energy, openings 67 may each have dimensions substan~ially smaller ;~ than the microwave wavelength or the ducting 66 may be formed of electrical conductor and may have a cross-sectional area below cu~-of dimensions. T~e exhaus~ gases ~7ithin region 41 then flow do~ward through the opening 51 between the edges of waveguide assembly 53 and base panel 48 into the gap 44 7;~

immediately above the pavement 36 where much of the heat content of the exhaust gas transfers to the pavement itself to supplement the microwave heating. Still further utilization of the heat generated by engine 59 may be accomplished if the engine is enclosed by a gas-tight housing 68 except at the cooling radiator 69 through which cooling air is drawn by the engine fan and except for the air intake 71 of the engine~ Thus air which has been drawn into the housing 68 through radiator 69 and which has been heated in the process of cooling the radiator is intermixed with the hot exhaust gases and delivered to the surface of the pavement 36. The engine exhaus-t heat may be utilized for other purposes, if desired, as will hereinafter be described.
Considering now suitable trapping structures for preventing the escape of microwave energy at the gap 44 between the pavement 36 and the ùnderside o~ the above-described vehicle components, any of a variety oE different forms of trap may be employed Eor such purposes of which two are used in combination in the example depicted in Figures 7 and 8. A first such ~0 trapping device, which may be characterized as a gap trap 72, is defined simply by the electrically conductive undersurface of base panel 48 and the subjacent portions o~ pavement 36. Owiny to the above-des~ibed configuration of base panel 48, the gap trap 72 e~tends along both sides and across the front and back of the area at which microwave energy is applied to the pavement.
The gap trap 72 functions to suppress outward horizontal propagation of microwave energy at gap 44 owing to -the fact that the electrlcally conductive material of panel 43, which defines the upper boundary of gap 44 in the trapping region, acts to reflect microwave energy whereas the pavement 36 which defines the bottorn boundary oE gap 44 in the trapping region to absorb micro~Jave energy. 2Iicro~ave energy, such as the energy entering gap trap 7~ from the re~ion 41, d~es n~.t pxopaC~te in space by flowing in a sin~le coherent manner.
Instead such energy tends in eEfect to continually disperse in all ~lirections at rig'nt angles ~o the nominal pa~h of energy 10w. The sizable portion of such energy w'nich is directed do~n~ardly in passage along gap trap 72~ because of this effect, enters the lossy pavement 36 and is absorbed and converted to heat. That portion of microwave ener~y which tends to mo~e in an upward direction is reflected do~n-ward by the conducting undersurface of panel 48 and as a con-sequence also enters the pavemen~ wher.e it is absorbed. T~us micro~ave field intensity decreases sharply in the outward direc~ion within the gap trap 72. The de~ree ,o which micro-wave energy is attenuated in passing along the gap trap 72 is in part a ~unction of the lengt~l of the trap in the direc- ;
tion of microwave propagation. In theoryg the trap 72 could be made sufficiently long ~o diminish the microwave ield to any desired extent so that whatever amount.of microwave power is actually released from the outside edge of t'ne trap is within tolerable limits. In practice this would? at least in many cases, require an applica~or vehicle of undesirable length and breadtn. Accordingly, the gap trap 72 of appLi- :
cator 33 is supplemented by use of another iorm of mîcrowave ~.
2~ blocking means which m~y be termed a chain trap 73. The use of t~o different forms of trap is advan~ageous even where one trap may suffice in the~ry since unusual con~itions th~t te~-porarily detract from the effectiveness of one form of trap will not necessarily affect the other. For exa~ple, the ~3~

ina~erten~ presence oE a si~able flat slleet ol discarded conductive metal foil lying on the pavement 36 under the gap ~rap 72 mi~tlt cause the te~porary release of increased amoun,s o~ micro~Ja~e energy ~hrough the gap trap 72 in the i~ediate region of the foil. Such an occurrence would, i anything, enhance the trapping action of the chain trap 73.
The c~ain trap ;73 may consist of a mass of short lengths o chain 74 formed of links of electri.cally conduc-tive metal such as steel, the lengths of chain having upper 1~ ends secured to the upper inner surface of housing 47 by a suitable hanger element 76. Chains 74 extend do~ward within housing 47 and are of sufficient lengt~ that the lower ends of the chains drag along the surface of pavemen~ 36,-the chains preferably being of some~'nat greater length t'nan the spacing lS between hanger 76 and the pavement so that the chains r~y drop into and occlude any craclcs, declivities or other small sur-face irregularities which may be encountered in the pavement.
The cllains 74 are closely packed together and form a thick mass of condu~tive ~etal which is sufficiently flexible to n accommodate to variations in gap 44 but in whic~ such through passages or int.erstices as exist are convolu~ed and have maxi-mum dimensions well below cut-o~ ~imensions ~or the microwa~e requency which is utilized. ~he chain trap 73 extends along bot sides of the gap trap 72 and transversely across the front and back of the gap trap as well.
In some instances the microwave applicator 33 ve-hicle may llave an effective ~.7idth whic~ does not completely span the roadway or other paved area whic~ is being worked and under - 35 ~

33~

tllese circumstanc~s t~le repaving operaLions are performed by s~lccessively -traveling along parallel strip portions of ~he road~ay or the like. In other instances the applicator vehicle may have suf~icien~ idt'n LO completely span a road-S way and therefore to accomplis~ the repaving operation inone passage. Under either circumstance conditions ~xist at least par~ of ~he time in w'nicil one or both sides of the ve-hicle are situated at one side of the pavement 36 an~ over the road shoulder or other unpaved adjacent surface. Such road shoulders or the like may no~ be precisely at ~he same level as the pavement 36, road shoulders being more often slightly'depressed relative to ~he adjacent pavement surface.
As pointed out above, the chain traps ~3 have some a~ility to adjust to variations in distance of the subjacent surface from the undersurfaces of the vehicle. To further accommodate to elevational di~ferences along the edges of the old pavement, it may be desirable that the portions of the chain trap 73 which extend along the sides of the vehicle be capable o some vertical movement as a whole in order to accommodate bet-ter to sizable differences in the elevation of the pave~ent36 and adjacent unpaved areas.
For this purpose the chain trap housings 47' whic~
are situated along the sides o-E the applicator 33 have in-clined upper portions 77 w'nich extend outward and downward from the side panels 43 of the vehicle and which are coupled ' - to the side panels through hinges 78, Support wh-eels 79 are journaled on the side houslngs 471 to ride along the under-lying sur~ace thereby causing the housings 47' to swing out-ward and upward or in~ard and downward as necessary to 7 ~ 9 accommoda~e to diferences of the elevation of road shoul-ders and ~he like rela~.ive to the pave~ent 36. ~inges 78 are pref~rably of the disassemblable form so ~hat the side trap housings 47l and the associated portion of chain trap 73 may be removed fxom the vehicle to facilitate transpor-tation between work sites.
In operation, the applicator 33 is slowly towed along the pavement 36 wEIich is to be recycledr Microwave energy generated by magnetron tubes 56 is coupled into the underlying pavement 36 by waveguides 52 causin~ heating and consequent softening o~ the asphalt and decompositiQn o~ the pavement co~stituents which may then be re~ixed, regraded and recom~acted while in the heated state. The pavement heating action of the microwa~e energy is supplemented ln this par lS ticular microwave applicator 33 by heat transfer ~rom the hot exhaust gases of engine 59.
The degree o~ hea~ing o~ the pavement 36 which is : realized is a function of several variables including the ag-gregate mlcrowave power output of the m~gnetron tubes 56, the compositio~ and starting temper~ture of the paveme~t 36, the amount of heat transferred to the pave~ent by the engine and exhaust gases and the rate of ~ravel o~ the app~icator. Under most circumsta~ces, heating of th2 pavement 36 to tem~ra~ures within the range from abou~ 170 F. (77 c.) to about 250~ F.
~ 25 (121 c.) produces the desired decom~osition and enables the .~ subsequent remixing~ regrading and reco~pacting. Whil~ the de-gree of heating oE ~pav~ment can be controlled by regulating the power output of the magn~tron tubes 56 and to some extent by controlling the proportion of the engi~e exhaust which is ' 3~

directed to the pavement surEace, in most cases it is desirable to operate at maximum levels in both respects and -to control the te~perature to which the pavement 36 is heated by reyulating the speed of the applicator vehicle along the roadway or the like. To facilitate this form of control a pavement temperature sensor 80 of a suitable known form, such as an infrared radlation detector for example, may be carried on the rear of the vehicle slightly above the pavement 36. `
The applicator vehicle may be speeded up if the temperature sensor indicates that the pavement is being heated to a greater extent than is desired and the vehicle may be slowed under reverse circumstances.
It is also desirable in most instances to provide microwave energy detectors 81 of suitable known form at L5 several locations under the exterior of the vehicle to indicate if microwave leakage should oc~cur. If desired, such detectors may be interlocked with the microwave power supply system 62 to shut down magnetron tubes 56 upon detection of a microwave level above a predetermined minimum tolerable ~20 value. By mounting four such microwave detectors 81 on arms 82 each of which extends obliquely from a separate corner of the applicator vehicle, each such detector may efficiently monitor for possible leakage at two sides of the vehicle. i~
Modifications of various aspects of the applicator vehicles are readily possible. The waveguides, for example, may be aligned in the direction of travel instead of being transverse and may be arranged to act essentially as microwave radiators rather than as coupling devi~es. Other forms of trapping device for suppressing the release of microwave energy may also be employed. Figures 9, 10 and ll , ~ .

'- ~

- :~73~

in conjunction depict a modified applicator 83 embodying each of -these modlfications, The microwave applicator ~3 of Figures 9, lO and ll may again have a horizontal rectangular frame 84 oE high-s ~ ength structural members supported above the pavement 86by road wheels 87 and provided with towing linkage 88. A
horizontal rectangular platform panel 89 is again carried on the frame 84 and a microwave power supply and control system cablnet 91 is sltuated above the panel. Where the applicator .
lO 83 vehlcle carries its own electrical power source as in this ~ :
example an engine 92 may be provided to drive an electrical :.
generator 93 with the engine and generator being disposed above panel 89. Ducting 94 may again be provided to direct the hot exhaust oE englne 92 downward into the reglon below panel 89 in order to supplement the efi-ect of microwave energy in heating the underlying pavement 86.
A plural.ity of magnetron tubes 96 or the like generate microwave energy and each is coupled to one end of an associated one of a series of waveguides 97. The waveguides 97 differ in several respects from the corresponding components of the previously described microwave applicator vehicle. Waveguides 97 in this instance are situated at a higher level above the pavement 86 and in ~;~
transferring microwave energy to the pavement such waveguides function more as radiators or antenna rather than as close couplers as in the previous example. Waveguides 97 are disposed in a parallel but spaced-apart relationship to each other and are allgned with the direction of travel o:E the applicator vehicle instead of having a transverse disposition as in the previous case.

`

33~

As is known in the artf a variety of different slot configurations may be used in waveguides to provide for radiation of microwave energy for successive portions of a surface extending along the waveguide. In this example, the underside of each waveguide 97 is provided with a series of spaced-apart short transverse non-resonant parallel slots 98 for this purpose. The waveguides 97 are thus slotted lossy waveguides of the general form described in prior United States Patent No. 3,263,052. Power radiating waveguides having resonant slot configurations may also be used.
Electrically conductive side panels 99 extend downward from frame 84 at each side of the vehicle with the lower ends being spaced above the pavement 86 to leave a small gap 101 which is preferably just sufEicient to accommodate to irregularities in the pavement surface over which the vehicle may be required to travel. A horizontal rectàngular sub-platform member 102 extends between side panels 99 at an interlnediate level between platform 8g and the pavement 86. The lower portion of each waveguide 97 fits into a separate one of a series of rectangular slots 103 in subplatform 102 so that the lower portions of the waveguides in effect constitute a continuation of the electrically conductive surface defined by the subplatform. Because of this arrangement, the upper boundary of the free microwave energy reyion 104 is not formed by the platform panel 89 as in the previous example but is defined instead by the subplatform 102 and contiguous undersurfaces of the waveguides 97. To enable hot exhaust gases from engirle 92 to flow downward to the pavement 86, subplatform 102 is transpierced by a large number of apertures 106, arranged in parallel rows along each side of each waveguides 97 in this ;, example, which have diameters substantially smaller than the wavelength of the microwave energy generated by magnetrons 96 so that microwave energy is confined to the region below the subplatform 102~
To inhibit sideward propagation of the microwave energy emitted by waveguides 97 and to provide for more individualized control of microwave field intensity at the region of the pavement beneath each waveguide if desired, one of a series of electrically conductive partitions 107 extends downward from subplatform 102 to gap 101 between each adjacent pair of waveguides 97, the partitions being aligned ;~
in parallel relationship with the waveguides. A similar partition 107' extends downward from subplatform 102 between each side panel 99 and the adjacent one of the waveguides 97, partitions 107' being spaced from the side panels to define a .
cavity trap 108 for suppressing microwave energy release as will hereinafter be discussed in more detail.
In operation, microwave energy generated by magnetrons 96 is emit-ted from slots 98 of waveguides 97 and 20 is channeled down towards pavement 86 by partitions 107. The microwave energy is then absorbed by the underlying pavement 86 in which process the energy is converted to heat. Thus as the applicator vehicle 83 is traveled along a strip of pavement 86 asphalt liquefaction i5 brought about in ~`
successive incremental areas of the pavement after which the constituents may readily be remixed, regraded and recompacted in the manner hereinbefore described.
The alignment of the waveguides 97 in the direction ~
of vehicle travel in this example, as opposed to the ~ `
transverse waveguide alignment in the previous example, has the advantage of enabling an op~imized non-uniform . . .

application of microwave eneryy to the pavement 86 from Eront to rear. As is known in the art, a variation ln the amount of microwave power emitted from successive portions of each waveguide 97 may be arranged for by providing slots 98 along successive portions of the waveguide which have configurations and locations selected for this purpose. For example if the slots 98 are made proyressively shorter from the front to the rear of the waveguides 97 the amount of power radiated from successive portions of the waveguides lQ will decrease from front to rear. This capability of being able to provide for a more intense microwave field at the front portion of the vehicle relative to the more rearward porti-on can speed the process of pavement decomposition, enabling faster vehicle travel. In parti~ular, the coupling efficiency of microwave energy to most asphalt pavements increases as a function of the temperature of the pavement.
Thus it may often be advantageous to proportlon the waveguide slots 98 so that power emlssion decreases towards the rear portions of the waveyuides and is relatively high towards the front portions. In such a constru~tion a proportionately larger amount of the generated microwave energy is applied to the colder area of the pavement which requires a larger power input in order to be heated at a given rate.
While alignment of the waveguides 97 with the direction of vehicle travel has the advantage discussed above, it also has a disadvantage in that uniform heating in the transverse direction across the pavement is more difficult to maintain and if an individual one of the magnetrons 96 should Malfunction then a largely unheated narrow strip of pavemen-t may result. ~his does not occur where the waveguides are oriented transversely as in the ~ ' ~

. .

previously described embodiment of the applicator. If one oE
a series of transverse waveguides should cease emittiny microwave energy or release energy at a decreased rate, there is simply a relatively small reduction in the heating of the entire strip of pavement being treated which can be quickly detected by temperature monitoring means and which condition can be immediately rectified if desired simply by slowing the rate of travel of the vehicle. Thus the matter of aligning the waveguides in the direction of vehicle travel or transversely to such travel is a question of evalwating the above-described advantages and disadvantages of each and the preferred arrangement may vary from job to job depending on specific conditions.
The modified applicator vehicle 83 of Figures 9 to 11 also differs from the example earlier described in that the waveguides 97 are situated a greater distance above the pavement 86 and are therefore not so closely coupled to the pavement in the electrical sense as in the previous embodiment. In the close-coupled arrangement of the previous embo~iment, the pavement 86, for practical purposes, functions in the manner of a terminator or dummy load for the wave~uides. This effect is not present to a very significant extent in the embodiment of Figures 9 to 11 whérein the waveguides function largely as radiators or antenna. The radiator arrangement is somewhat less efficient as an energy transfer means, relative to the close-coupled arrangement, but has the advantages of more uniform heating of the pavement and greater penetration into the pavement.
Considering now the trapping means which suppresses release of microwave energy outward from the vehicle at the gap 101 between the microwave applicator elements and the pavement, the embodiment of Figures 9 to 11 employs two forms of trapping means which differ somewhat in form and mode of operation from the corresponding components of the previously described embodiment. The first such trapping means is the cavity trap 108 which, as described above~ is defined by the outermost partitions 107', the lower portion of the adjacent side panel 99 and the portions of subplatform 102 situated therebetween. The cavity trap 108 extends along both sides of the vehicle and acxoss the front and back thereof outwardly from the assembly of waveyuides 97. To define the inner boundary of the cavity trap at the front and back of the vehicle electrically conductive cross panels 109 extend across the ends of the partitions 107 and 107' at the front and back of the waveguide assemblies.
Thus the cavity trap 108 constitutes an inverted boxlike structure Eormed of electrically conductive material which is open at the bottom and of which the lower edges are situated close to the underlyinc~ pavement 86. A microwave 20 energy-trapping effect is reali~ed inasmuch as energy which `
propagates outwardly under the lower ed~e of the conductive member, such as outer partition 107', that defines the inner boundary of the trap does not simply flow in a linear manner ~ ~`
under the corresponding outer boundary of the trap formed by j -~5 side panel 99. Instead, as previously described, such energy in effect attempts to spread outward in all directions from the nominal direction of travel. That portion of such energy passing under panel 107' which spreads downwardly into the pavement 86 is immediately absorbed and converted to heat.
The portion of the energy which spreads upwardly is reflected Z I

by the conducting walls of the cavity trap. ~ very large proportion of the various possible paths of such reflected energy eventually enter the pavement 86 after one or more reflections and energy traveling such paths is ultimately ~irected downwardly into the pavement 86 and is absorbed.
Thus the proportion of the energy which passes under partition 107' that can also progress out under side panel 99 is very small.
Additional cavity traps 108 may be provided to further suppress microwave release. In many cases it is desirable to supplement the cavity trap with a diEferent form ~ -of trapping means for back-up protection and to guard against specialized conditions which may adversely affect a specific type of trap. For these purposes a supplementary energy-trapping means which is termed a brush trap 111 is provided in the applicator 83 of Figures 9 to 11. A first such bruch trap 111 is disposed at the outer side of each side panel 99 and also extends across the front and back of the microwave region along the outer side of cross panels 110 which extend between the front and bac~ ends of partitions 107'. The brush trap 111 may consist of angle members 112 which, in conjunction with the lower portion of side panels 99 and the lower portions of front and rear cross panels 110, forms an !:
electrically conductive housing of interted U-shaped cross section. Within the housing deined by such members, a mass of flexible electrically conductive resilient small wires 113 are disposed with the upper ends of the wires being attached to angle member 112. The individual wires, which may be of resilient steel for example, have a length slightly greater than that needed to reach the underlying pavement 86 or - ~ ~

~ 7339 adjacent yround surface so that as best seen in Figure 11 the lower ends of the wires are deflected by contact with the pavement or other surface and ride along such surface as the vehicle travels. As the interstices between the individual wires in the mass of such wires are far below cut-off dimensions for the microwave frequency used in the applicator, the volumes of wire form a microwave barrier which can extend and contract to accommodate to small surface irregularities in the underlying pavement.
Although the trapping means of applicator 83 as described to this point are operative under virtually all ordinary circumstances to prevent the escape of any significant amount of microwave energy, the importance of assuring this result is such that it is often desirable to 15 provide what might appear to be highly redundant trapping j arrangements. To provide still further assurance against the release of microwave energy, the applicator 83 of Figures 9 to 11 carries still another brush trap 111' which extends along~-both sides oE the vehicle laterally outwardly from the first brush trap 111 and which also extends across the front and the rear of the vehicle. The basic construction o~ brush trap 111' may be similar to that of trap 111 as previously described except that the portions which extend along the sides of the vehicle are secured to the lower edges of electrically conductive supplemental side panels 116. Each supplemental side panel 116 is spaced outward from the panel 99 at the same side of the vehicle. The upper portion oE ~ ;
; each supplemental panel is angled towards the adjacent side panel 99 and is coupled thereto through hinges 117. Thus brush trap 111' may swing upwardly and outwardly and ' ' ,, ' ,., ~ : ` `

.........

downwardly and inwardly relative to the main body of the vehicle as may be necessary to accommodate ~o localized elevational variations in the surface along which the vehicle travels. These are particularly likely to be encountered along the edges of pavement 86 where the side portions of the vehicle may travel at times since, as indicated by dash line 118 in Figure 9, the shoulders of roadbeds are often at a ~-slightly different elevation than the adjoining pavement surface 86. To maintain the brush traps 111' at the proper level relative to road shoulder 118 or the like, support wheels 119 may be journaled to the supplemental side panels 116 to ride along such shoulders.
As best seen in Figure 10 in particular, the ends 121 of brush trap 111' including the ends 122 of hinged supplemental side panels 116 are angled to extend a distance into the space between the fixedly mounted portions of brush j traps 111 and 111' that extend transversely across the front and back portions of the vehicle. This maintains efficient microwave containment at the corners of the vehicle at such ~`
''~ times as the hinged outer brush trap 111' may swing outwardly or inwardly in response to variations in the elevation of the underlying surface. l~ `
It should be observed that the hinged supplemental side panels 116 in conjunction with the fixed side panels 99 function as a supplementary cavity trap as well as being a support means for the outer brush trap 111'.
It should be understood that the specific forms of microwave energy trapping means as used on the above-described two examples of a microwave applicator vehicle can be interchanged or used in varying combinations and larger ' numbers of such traps may be provided on a given applicator vehicle where extremely rough pavement or other conditions malce it desirable. Other forms of trapping means for suppressing the release of microwave energy at the gap between the vehicle structure and the underlying surface are also possible, one example of which i5 depicted in Figures 12, 13 and 14 in con~unction.
Referring initially to Figure 12, the microwave applicator vehicle 123 itself, apar-t from the trapping means, may be of one of the forms hereinbefore described and thus may include a rectangular platform 124 and side panel members 126 and front and back cross panel members 127 which extend clownward from the edges of the platform towards the underlying pavement 127 and which members collectively form an inverted rectangular boxlike structure of electrically conductive material. The above-described structure may be supported by road wheels 128 which enable travel along pavement 127 in the manner previously described. ~n inner electrically conductive inverted boxlike enclosure 129 of less length and width than platform 124 may contain microwave generation and emission structure of one o the forms previously described. Side panels 126 and cross panels 127 do not extend completely down to the surface of pavement 127 in order that the vehicle may I
override irregularities in the pavement and thus a small gap 131 is present between the above-described structure and the pavement. Release of significant amounts of microwave energy through this yap must be prevented.
For this purpose a flat rectangular open-frame trap panel 132 of electrically conductive material, such as dimpled s-teel sheet metal, is disposed in the space between microwave . ~ .

enclosure 129 and side panels 12~ and between the microwave enclosure and the cross panels 127 at the front and back of the vehicle, the trap panel 132 having dimensions conforming to such space in order to close the lower boundary of this region. Trap panel 132 has an upturned inner edge portion 133 abutted against the side surfaces and front and back surfaces of microwave enclosure 129 and also has an upturned outer edge portion 134 abutted against the inner surEaces of side panels 126 and front and back cross panels 127. While trap panel 132 effectively defines an elec~ically conductive surface spanning the space between the microwave enclosure 129 and the panels 126 and 127 of the vehicle it is also capable of limited independent vertical movement relative to such c:omponents. To deEine limits to the extent of such movement, a series of spaced-apart vertically oriented slots 136 are provided along the lower portion of side panels 126 and cross panels 127. One of a series of bolts 137 extends outwardly frorn each upturned edge 134 of panel 132 through each of the slots 136. Similarly, a series of spaced-apart vertical slots 20 138 are provided along the inner upturned edge 133 of the trap panel and bolts 139 extend outwardly from microwave enclosure 129 through such slots.
In the absence of further arrangements, trap panel 132 would drop down into contact with the pavement 127 and ride along the surface of the pavement, a condition which could cause rapid wearing of the panel. Panel 132 is supported a small distance above the pavement by a series of wheels 141 mounted along the side portions of -the panel and by a series of rollers 142 mounted along the front and back portions oE the panel~ In this example, there are two 33~

longitudinal rows of wheels 141 along each side portion of the panel 132. IndividuaL wheels 141 of the two rows have parallel but spaced-apart rotary axes so that, viewed from the side of the vehicle, the wheels of one column are centered in -the spaces between adjacent wheels of the other column.
The rollers 142 are also disposed in two columns along both the front and back portions of trap panel 132 in a staggered relationship so that when viewed from the front or back of the vehicle, the rollers of one column overlap two adjacent ones of the rollers of the o-ther column. As will hereinafter be discussed in more detail, the wheels 141 and rollers 142 have an electrical function in suppressing the emission of microwave energy as well as serving to support the panel 132 and the reasons for the above-described placements of the wheels and rollers will be discussed in connection with the electrical operation of the trap.
Considering now means for supporting the individual wheels 141 and rollers 142, with reference to Figures 13 and 14 in particular, the lower portion of each such wheel extends downward through a conforming slot 143 in panel 132. At each side of each wheel a support bracket 144 is secured on panel ¦-132 and each such bracket has a vertical slot 146 into which a short axle 147 extends from the adjacent side of the associated wheel 141. Each bracket 144 has a vertical passage ¦~

148 extending upward from the top end of slot 146 and a rod 149 extends down through the passage and bears downwardly i .
against the wheel axle 147 within the slot~ A pair of tension sprlngs 151 are connected between the base of each bracket 144 ;~
1:
i -50- i ~;~

~. :

and a cross member 152 at the top of the rod 149 of that bracket to urge the rod downward.
The rollers 142 at the front and back por tions of trap panel 132 have lower portions which extend downward 5 throuyh conforming openings 153 in the trap panel to contact the underlying pavement 127 and are retained in place and urged downwardly by bracket assemblies 154 similar to those described above in connection with the wheel 141 support means.
Accordingly, the trap panel 132 is supported by the wheels 1~1 and rollers 142 and rides along the pavement on such elements while being constrained to travel with the rest of the applicator vehicle. As the trap panel 132 is capab:Le of a limited amount oE independent vertical movement 15 as determined by slots 157, it may sel-E adjust as necessary to maintain a predetermined small vertical spacing from the pavement including at times when the other components of the vehicle may rise slightly due to a road ~heel passing over an elevated portion of the surface.
Considering now the microwave energy-trapping 1, action of the above-described structure, it may be seen , ;
that the trap panel 132 in conjunction with the underlyin~ 1 electrically lossy pavement 127 is basically a gap trap of the general type previously described. Moreover, it is a 25 highly efficient one as a very close spacing of the under-side of panel 132 from the pavement 127 may be established and maintained since the panel rides on its own wheels 141 and rollers 142 rather than being supported by the main . ,~

`' road wheels of ~he vehicle and is capable of limited in-dependen. vertical moveme~t relative to the res~ of the vehicle. Further, there is still anot~er trapping e~fect additional to Lhe basic gap trap mode of operation~
In particular, the wheels 141 and ro]lers 142 may be formed at least in part of electrically conductive material and may be spaced apart a distance s~ller than the cut-off dimensions for the particular microwave fre-quency employed in the applicator vehicle. The lower por-tions of the ~heels 141 and rollers 142 which extend below the trap panel 132 are then, in effect, spaced-apar~ con-ductive elements that break up the gap 131 between the pancl 132 and pavement 127 into a network o intersecting passages no one of which has horizontal or ver~ical dimen-sions suEficiently large to allow outward propagation of a sizable amount of microwave energy, Further, this con-dition is m~intained when an individual wheel 141 or roller 142 passes over a locali~ed crack~ depression or other de-clivity in the pavement. Çravity, rei.nforced by springs ~0 151 in this example, then causes that ~7heel or roller to move downwardly in~o the crack or the like to prevent any openin~ through the trap, of greater than cut-off dimen-sions, from being established. Similarly, if a wheel 141 or roller 142 should override a localized raised area such as a small stone lying on the pavement, i~ does not result - in the entire panel 132 being lifted. Instead, only the particular affected wheel 141 or roller 142 rises.
Figure 15, depicting the left rear corner of still another microwave applicator vehicle 156~ illustrates still _ 5~ _ other forms ~f microwave energy trapping structure for ~;
inhibiting the release of microwave energy at the gap 157 be~ween the underside of the vehicle and the underlying pavement 158 or bet~een the underside of the vehicle and the underlying earth in instances where the side of the vehicle is riding along a road shoulder.
Applicator vehicle 156 may have a rectangular body lS9 containing microwave generation and application components of the form hereinbefore described wit~ refer-ence to preceding embodiments. The following description will therefore be confined to the modified micro~ave energy `~
trapping means and a modified disposition of road wheels on -~
the vehicle which enables the road wheels .o be utilized as a component of the trapping means i~ desired and ~hich may also enable a shortening o~ the transverse di~ension of the vehicle in some circumstances.
In particular, applicator vehicle 156 carries transverse trapping structures across the front and back which are of a form termed skirt traps 161, t~e rear skirt trap being depicted in Figure 15. The rear skirt trap 161 may include a transverse member 162 fQrmed of electrically conductive material which extends along the back surface 163 of the b~dy 159 of the vehicie at a level a small dis-tance above the gap 157. Member 162 includes a flat shelf 164 which extends a distance outwardly rom the back sur- t face 163 of the vehicle and has spaced-apart parallel slcirt carrier elements 166 and 167 which extend downward from the underside of shelf 164 to gay 158. Member 162, shelf 164 and skirt carriers 166 and 167 are each formed of steel 7;3351~

or other electrically conductive mateL-i21 and if desired may be a sin~le integral element.
Propagation o micro~7ave energy i~ the back~ard direction from the vehicle through gap 158 is blocked by S flexible slcirts 168 and 169 ~hich extend do~nward from carriers 167 and lG6 respectively to contact the pavement 158 and which are preferably of sufficient length to cause the lower por~ions of the skirts to deflect and drag alonO
the surface o~ the pavement as the vehicle travels in the for~ard direction as indicated by arrow 171. The rearmost skirt 163 may, i desired be lengthier than the forward skirt 169. In additîon to being flexible, the skirts 168 and 1~9 are formed at least in part of a material which is electrically conductive so that microwave energy is not lS transmitted through the skirts but is înstead reflected.
~hile the skirts 168 and 169 may si~ply be formed of flex-ible resilient metal sheeting, other constructions ~ay also be used such as laminations of wire screen or mesh embedded in rubber or other flexible m~ter:ial~ As the rear skirt trap 161 must travel over the heated pavement, heat-resis-tant materials should be employed in forming the skirts.
As the skirts 168 and 169 reflect microwave energy, any such energy at~empting ~o propagate backwardly through the trap 161 is redirected back towards the body of the vehicle or else downward into the highly lossy pave-ment 158 where it is absorbed.
As will be apparent, an essentially similar skirt trap may be utilized across the fron~ of the applicator vehicle 156 although in that case the travel o the vehic7 2 causes the rear portions of the sl;irts 168 and 169 to ben~ baclc to~7ards the vellicle rather ~han a~ay from the vehicle as in the case of the rear trap 161.
Considering now the trapping means 172 disposed along the sides of the applicator 156 of Figure 15, an electrically conductive shelf 173 extends a distance out-wardly from the side panel 174 of the applicator vehicle at a level sufficiently high, in this example, to extend over the road wheels 176 which support the vehicle for travel along the pavement, the road wheels being journaled to the vehicle body 15g on suitable axles 177, An elec-trically conductive adjustable panel.l78 extends out~ardly and downwardly from the outer edge of shel 173 w.ith the two members being linked together by hinge means 179 tha, enables the panel 178 to swing up~ardly and downwardly rel.ative to the shelf. Disposed along the lower edge of side panel. 178 is an electrically conductive member 181 having spaced-apart parallel skirt carrier portions 182 and 183 extending downward to gap 157. The upper inner edge of a first side skirt 184 is secured to the outermost carriex 183 and the lower portion of the skirt 184 bends outwardly from the vehicle and extends or a distance out-wardly to drag along the underlying p~vement 158 or along the underlying earth or gravel in the case of a road shoul-der. Skirt 184 is flexible and formed at least in part ofelectrically conductive material as previously described in connection with the rear trap 161 and ~hus functions to suppress t~e release of rnicrowave energy from the vehicle in the sideward direction.

~7~

The s~irts utilized in the above-described skirt traps need not necessarily be oE ~he form, described above, in wllicll tLle skirts are hi~hly fLexihle and in which a sizable portion of the skirts lie flat agains~ the under-lying pavemen~. The inner skirt 186 of the side trappingmeans 172 in this example, is a rigid me~allic strip which extends downward from carrier 182 in a vertical direction to the underlying pavement or earthO Inner skirt 186, which is replaceable upon wearing of the lower edge, is par~icularly useful in a side trap designed to travel along the relatively so~t earth or gravel of a road shoulder as the lower portion of such a skirt may readily be caused to cut a sm~ll ctistance do~n into the soft underlying surface and thereby provide a highly effective microwave trapping barrier. To enhance this mode of trapping and to enable the accot~odation of the side krapping means 172 in general to situations where a road shoulder may not be precisely at the same level as the adjacent pavement, means 187 for con-trolling the vertical spacing of the side skirt trap 172 relative to the underlying surface may be provided. In this example such means 187 includes an arm 188 extending up-wardly from the outside of hinged panel 178 and a hydraulic actuator 189. Actuator 189 has a retractable and extend-.
- ~ble rod 191 coupled to the upper end of arm 188 throu2h a pivot joint 192 and has a head end coupled to the vehicle -~body 156 through another pivot connec~ion 193. Thus con-~rac~ion of actuator 189 s~ings hinged panel 178 outwardly and upwardly to raise the side skirt trap 172 while exten-sion of the actuator lo~ers the trap, -It h~s been pointed out in connection with previously descri~ecl embodiments~ that the electrically conductive members such as 173, 178 and 182 in this ex-ample which support the outennost trapping means 172 may also, in effect, constitute a cavity trap o~ the kind previously described. Thus microwave trapping ac~ion in the side trap 172 of Figure 15 is not limited to the s~irts 184 and 186 but is supplemented by the fact that ~embers 173, 178 and 182 in effect define a cavity trap of the ~ype hereinbefore discussed. The ability of a cavity txap to suppress the release of microwave energy lnay be enhanced by lining at least portions of the inner surface o the cavity with a layer of lossy or microwave absorbent mater-ial ~hich in this example is an iron oxide slab 194 disposed against the inside surface of hinged panel 178 Other known electrically lossy materials, such as rub~er, various ceram-ics or containers of wa~er formed of non-conductive material, for exam~le, may also be disposed in a cavity trap to func-tion as a mi~rowave absorber Still fur~her, the disposi-20 tion of the road wheels 176 of the vehicle within the cavity trap defined by members 173, 178 and 182 stiLL urther en-hances the suppression of microwave energy release i por-tions of the wheel itself are formed of electrica~ly lossy material as is often the case. Rubber, for example, is a lossy substance. `~
It has been pointed out how microwave applicator vehicles of the general kind described above may ~e used with additional conventional forms of construction equip-ment to accomplish the on-site recycling and repaving of an existing asphalt road or other paved area. Under many 7;~

con~itions, great~r efficiency may be realized by using one of several ~orms of integrated road-paving recycIing system in which mechanisms and components for accomplish-ing the microwave heatinO, remixing, grading and compact-ing s~eps are par~ially or wholly combined into ~ special-ized vehicle assembly. Figures 16 and 17 in conjunction depict one example of a tiller-compactor vehicle 196 which may be utilized to follow a micro~ave applicator vehicle in order to perform the mixing, grading and at leas~ a por-tion of the compacting steps o the method.
The tiller-compactor vehicle 196 may have front and rear transverse frame members 197 and 198 respectively, side frame members 199 and a rectangular platform 201 dis-posed above the frame members ~hich in conjunction Form an lS inverted rectangular boxlike vehicle body 202 adapted to travel along the pave~ent 203 which is to be relaid~ The vehicle body may be supported on a pair of rear road wheels 204 and a pair o~ front road wheels 206 which are pre~erably steerable through conventional wagon s~e r linkage 207 2n coupled to a pivotable towing tongue 208 mounted at the center o the front of the ~ehicle. I~ the vehicle is not designed to be towed, it may be provided with an engine, drive system and control means of suitable kno~ forms.
The tiller-compactor 19S follows behind a microwave 25- applicator vehicle which has heated the pavement 203 to a temperature at which it is readily crumbled and at which it may easily be remixed by stirring, raking, tilling, plow-ing or other similar operations. This remixing is effected in the present example by three rotary tillers 209A, 209B

and 20'j~v carried ~it~in the body 20~ of ~he vehicle w~th tiller 209A being situated near the front of the vehicle and bein~ follo~ed at intervals by till~rs 209B and 20gC.
Each such rotary tiller ~09 is supported by a pair of pivoLable arms 211 situated one at each side of the ve-hicle and each tiller has radially exLending blades 2 carrying pavement cutting, mashing and stirring heads ~13 The tillers preferably tu~ counterclockwi.se as viewed in Figure 17 and the h~ads 213 have a sharp le~ding or cutting edge 214 ~ollo~ed by a rounded heel 216. This head con-struction causes the tillers to shave off successive in-crements of the heated pavement and to exhibit a lump-mashing effec~ as well as accompli.shing a general stirring ox remixing of the pavement constituents.
lS To provide for selective adjust~ent of the ver-tical level oE each tiller 209 relative to pavement 203 in nrder ~o control khe cutting and ~ixing depth, the upper ends of the tiller supporting arms 211 are coupled to axles 217 which extend through side fra~e members 199, as best seen in Figure 16, and a crank arm 218 extends radially from each such axle at the outside of the side rame members.
A hydraulic actuator 219 is coupled between each such crank - arm and the side frame ~ember lg9 enabling each tiller to be raised or lowered by extension or contraction of the assoc;ated actuators ~19. Although hydraulic actuators or `~
cylinders~ such as actuator ~19, are used to accomplish a controlled movement of various elements in the embodiments of the invention ~hich are described herein, it will be apparent that electrically operated actuators may be substi-tuted or such devices if desired~

_ 59 _ 3~1~

~ acll tiller 209A~ 20gB and 209C is driven by an associa~ed one of thrce electrical motors 221~, 221B
and 221C respectively throu~h an associated one o~ threz speed reduction gear units 2~2A, 222B and 222C respec-tively. Referring momentarily to Figur~ 18, drive may betransmitted to each tiller, such as the front tiller 209A
through a compound gear 223 having a large-diameter gear portion 224 the upper end of which extends through a slot in platorm 201 to engage the-output gear 226 of speed reduction unît 222A. To support compound gear 223, axle 217 may extend inwardly to a bearing 227 which is secured to a gas manifold sidewall 228 that extends downward from the underside of platform 201. Com~ound gear 223 is ro-tatable xelative to the supporting axle 217 and has a smaller-dimeter gear portion 229 which is coupled, by means of a chain 231, with a drive gear 232 which is mounted on the end of the tiller blade support and drive shaft 233.
To protect the abo~e-described drive and vertical adjust-ment mechanisms from pavement constituents which m~y be impelled upwardly and outwardly by the tiller heads 213 and to provide some shielding of such components from the hot gas which is dixected to the pavement constituents during the remixing operation, a panel 234 preferably ormed o~
`~ thermally insulative material extends do~nward from gas manifold side ~ember 228 between chain 231 and the adjacent~l `
end of the tillers. ;~
Referring again to Figures 16 and 17 in combina-tion, the remi~ing operation is enhanced by three drag blades 236A, 236B and 236C situated behind tillers 209A, 209B and 209C respectively. Each such drag blade may be o~ flat rec-tangular configuration and has an upper end coupled to a --', ~ ' pair of sup~ort a~ls 237 through pivot couplings 23~.
Drag blade support arms 237 are situated adjacent ~he inner surfaces of side frame mernbers 199 of t'ne vehicle and slots Z39 are provided in panel 234 to enable the 5 pivot couplings 238 to extend through such panels to con-nect with the support arms 237 and to allow pivoting of the support ar~s for the purpose of adjusting the level of the lower ends of the drag blades, T'ne support arms 237 are in turn secured to axles 241 which are journaled in the side frame members 199 and which extend to the outer surface of the vehicle body where~ as ~est seen in Figure 16, a crank arm 242 extends radially from each axle and a hydraulic actuator 243 is coupled between the end of the crank ar~ and the lower portion of side frame member 199 to enable contxolled raising and lowering of the drag blades. Reerring again to Figure 17 in particular, the drag blades 236 are proportioned in the vertical direction to enable each drag blade t~ ~xtend downward and bac~ard into the decomposed pavemen~ so that the blade tends to be inclin~d. The drag blades 236 in~ercept pavement constit-uents which may be impelled backward by the action of the tillers 209, act to mash lumps which m~y be present in the paving material and act to grade the material following , .. . .
each remixing stage.
To perform a final grading and to compact the remixed pavement constituents, a screed 244 rides along the surface underlying the vehicle behind the rear~ost drag blade 236C. Screed 244 ~ay consist o a transverse mem~er 246 having a flat undersurface wllic~ curves up-wardly at the fo~ard edge to receive and co~press ~he remi~ed pa~7e~ent constituents~ -These operations are bes~ accomplished if the screed me~ber 246 is supported in such a manner that itmay be controllably raised and lowered relative to the vehicle body so that the do~nward pressure which the mem- ~.
ber exerts on the remLxed pavement constituents may be adjusted. It is oft~n preerable that the undersurface.
of the screed member 246 be slightly inclined with the more forward portion being slightly elevated relative to the trailing edge and it is also preferable tha~ this in-clination or angle o attack be adjustable~ In order to support the screed m~mber 246 while providing for these lS ad~ us tments, brackets 247 extend upward rom the top sur-face of the screed member to connect with a transverse support shaft 248 which has ends e~tending through slots 249 in the side paneling o~ the vehicle body. As best seen in F.igure 16, the opposite ends of the support sha~t 248 pro~rud~ a short distance from each side of the ve-hicle body and extend through the back ends of a drag arm :
251 at ea h side of the vehi~le. The fo~ard ends of drag ~rms 741 are coupled to the forward part of the vehicle .
through pivot couplings 252 ~hich connect with brackets 253 situated on platform 201. To provide for con~rolled raising and lowering of the level of the screed 244 a hy-draulic cylinder 254 is connected between each drag arm and the body of the vehicle through a pivot coupling 256, on the drag arm, and another more elevated pivot coupling ~ 62 -3~

.
257 at~ached to a bracket 258 ~7hich is secured to the platform 201. To enable control of the inclination or angle of attack of the screed 24~, a crank arm 259 extends radially from each end of screed support shaft 2~8 and one 5 of another pair of hydraulic actuators 261 is connected bet~een ~he ~nd of each crank arm and each pivot coupling 256.
~ eerring to Figures 17 and 18 in combination, arrangements for directing hot gas into the pavement con stituents and to structural com~onents which contact the hot decomposed pavement include a rectangular gas manifold chamber 262 situated below platorm 201~ The top of mani-fold chamber 262 is defined by the u~dersurface o platform 201 including a layer of thermal insulation 263 which is preferably disposed against the undersurface of the pla~-form. The side portions of the manifold chamber 262 may - be defined by the previously described man-ifold n~embers 228 ~`
which may also have a layer 264 o~ thermally insulative ma-terial against the inner surfacec ~hile the front and back of the chamber may be defined by ~ront and back transverse frame members 197 and 198 respectively with layers of thermal ~ insulation material 266 again being disposed along the inner surfaces o such membersr The bottom surface of the mani old chamber 262 is formed by a flat panel 267 situated a su~ficient distarl~e above the ~illers 209 and drag blades 236 to provide for the previously described vertical adjust-ment of such components.
A series of transverse slots 268 in panel 267 pro-vide or the release of hot exhaust gas downwardly into the region of each tiller 209 and clrag blade 23G and a ina~
slot 269 directs suc~ gas to a linear nozzle 271 ~7hich applies a stream of the llot gas along ~he upper surface of screed member 246. Maintaining T he screed member 246 at a high temperature in this manner improves ~he ac~ion of the screed in that pavement constituents including asphalt do no~ tend to adhere to a metallic surface which is heated to a te~perature sufficient to cause asphalt to act more or less in the manner of a lubricant. The com-monly observed tendency o an asphaltic composition toadhere,or stick to certain surfaces is an efect which occurs at lower temperatures at which the asphalt is în the process of so lid.ify ing.
In instances such as this example where the tiller~
cor~actor structure is not sel~-propelled and is not an inC ~`
tegral part of a larger vehicle containing other com~onents for practicing the inven~ion, ~he hot exhaust gas is ~e- ' ceived from another vehicle which tows the tiller-compactor.
For thispurpose a gas receiver chamber 272 may be mounted on the front of the tiller-compactor vehicle and is communi- ~' cated with m~nifold chamber 262 by a passage 273 ~hrough the front frame members 197 of the vehicle. ~eceiver cham~
:- ber 272 Tnay contain valving means 274 for adjusting flow rate. A conduit 2 76, preerably formed of thermally insu-~5 lative material, extends forward from receiver chamber 272 -to transmit hot exhaust gases to the tiller-compactor ve~
hicle in a T~nner which will hereinater be described in more detail. To enable the tiller~compactor vehicle to angle relative TO the kowing vehicie while traveling' aroun~l culves and to accomlnoclate to cliffercnces in vehicle inclination in traveling variably sloped road~Jays, the conduit 276 may be of a flexible plea-ted or bello~Js :forrn so that it m~y extend, contract and b~nd.
S Under some circumstances the tiller compactor vehicle may itself tow another vehicle of the same kind or o:i~ ano"~er kind~ such as a roller compactor for example, that may also require hot exhaust gas. For this purpose an outlet fi~ting 277, co~mltunicated with manifold 262 but normally closed by a cover 278, may be provided at the back end of the vehic le .
To provide :Eor the addition of supplementary asphalt, paving oils, or liquid conditioners to the decom-pos ed pavement cons tituent:s prior to or during remixing, a tank 279 is carried on platfontt 201 and may have a lining ~`
281 of thermally insulative materi.al~ ~xcept along the bot-tom surface, and may also have a filler spou~ 282. Heated asphalt or other liquid from the tank may be withdrawn and applied to the pavement constituents by a pump 283 having an intake pipe extending into the 1O~7er region of t~e tank and having an outlet pipe communicating with a flo~ manifold .
~84 which extends transversely across the front portion of - ~ platfoxm 201. A series of spray nozzles 286 extend down- ;.
ward from manifold 284 to apply the hot asphalt or the like -25 to the heated pavem2nt in front of the initial tiller 209A
in this exa~aple. The supplementary asphalt or the like, ~here needed, may also be applied in front of any or all of the additional tillers 209B and 209C if desired by re-arranging the position of nozzles 286 to such locations or - 65 ~

3~

by providing addi~ional no~zles.
~ sphalt pump 283 ~y be driven by an electrical motor 287 through a speed reduction clevice 2~8 and the electrical motor may also drive another pump 2S9 which pressurizes hydraulic fluid from a ~anlc 291 to operate the several previously described hydraulLc actuators on the vehicle.
Supplementary asphalt as well as other condi-tioners or the like which may be carried -ln tank 279 should in most cases be maintained in a heated condition. The in-sulation layer 281 in tank 27g may in some cases be suffi-cient for this purpose, particularly if suc~ insulation is absent from the ~loor of the tank and i~ the insulation 263 below platform 201 is also absent from an area below the tank. Heat is then read;ly conducted upward to the liquid in the tank through the suhjacent area oE platform 201.
However, in some circumstances it ~kay be desirable to pro-vide for a supple~entary heat input to the asphalt tank 279.
This m~y be accomplished by disposing a heat exchanger 292 ~ -wi~hin tank 279 which has opposite. ends comnunicated with the exhaust gas manifold 262. As exhaust gas within the heat ~xchanger 292 cools through hcat con~uction to the contents o tank 279, convection effects cause the rela-tively cool gas to descend back into manifold 262 while being replaced with hotter gas from the manifold~ By pro- .
viding a valve 293 at one or both ends of the heat exchanger, controllable by a handle 294 situated outside of the tankg the extent of this convection interchange may be regulated to thereby regulate the temperature within the tank 279.

~`

In ins Lances wnere this does not provide a suflicient de-gree of regula~ion, valve 293 may be replaced by a powered blower for producing a precisely controllable flow of h~t gas through the heat exchanger 292.
Electrical power for operating the several elec-trical components of the tiller-compactor vehicle 196 is received from the towing vehicle through a flexible cable 296 which may connect with a power connector pedestal 297 mounted on the fron~ of the vehicle. To ~ransmit such power on to still an~ther vehicle which may be towed in some ~ir-cumstances, a similar electrical connector pedestal 298 may be mounted on the rear of the vehicle. ;-Considering now how con~onent vehicles which may be of the forms hereinbefore described may be linked together and integrated to form a road reeycling system that may be ~rav-eled alon~ a deteriorated road at a slow rate o~ speed while leaving a repaved and reconditioned road behind, reference should be made initially to Figure 19. The road repaving sys-tem 299 of ~igure 19 includes a propulsion unit 301 which is a large flat-bed automotive truck 302 in this example although other types of self-propelled vehicle may also be employedO
The truck 302 should preferably be of one or the ~no~n ~o~ms of substantial load-carrying capaoity and which has mult;ple dr~ve wheels 303 for providing high traction and which is ca pable of sustained travel at ve~y low speeds which may typi-cally be of the order of three to twenty eet (or about 1 to 6 meters) per minute for example. To pro~ide electrical power for operating the microwave generators and other elec- -trical components o~ the system 299, one or nore conventional ~3~

~otor generator sets 304 are carried on truck ~0~ and ~he ho~ exhaust from the driving en~ines of the motor generator sets is collected itl a gas housing 306 carried near the back of the truclc. In a typical example, two m~otor gener-ator sets 304 may be present, each being of ~e dieselengine-driven form and each of which produces ~hree-phase power at 480 volts. I~ necessary, the exhaus~ gas of the engine which drives the truck itself ~ay also be collected in gas housing 306.
Truck 302 is coupled to and tows at least one microwave applicator vehicle 307 which may be of one of the orms hereinbefore described ex~ept insofar as the ap-plicator vehicle need not carry its own ~otor generator set.
Applicator vehicle 307 is in turn coupled to and tows a tiller-compactor vehicle 308 which may be of the form here-inbefore described in detail.
A thermally insulated hot gas conduit 309 is car-ried on applicator vehicle 307 and the front end of the ~as conduit is coupled to gas housing 306 o~ the propulsion unit 301 through a flexible bellows pleated thermally insulative conduit 311 that enables angli~g of the applicator vehicle relative to the propulsion unit as the system travels around curves in the roadbed. A blower 312 ~ay be provided be~een housing 306 and flexible conduit 311 to enhance the 10w o 25 hot exhaust gas and i$ preferably of the form which allows a t controlled dilution of the exhaust gas with cool air LO bring the temperature of the gas flow down to the range, typically about 300 F. (150 c.), which is preferred for use in heat-ing the p~vementO The hot gas intake ductin~ 313 of the - ~8 -applicator vehicle is connected into conduit 309 pref~
erably throucrh a ~alve 314 for re~ula~ing the propoxtion of the hot exhaust 1OW WlliCIl iS admittecl into the appli-cator vellicl.e.
Hot exhaust gas is transmi~ted to the ~iller-compactor vehicle 308 through another 1exible bellows-pleated conduit 316 which connects the back end o conduit 309 with the gas-receiver chamber 317 of the tiller-compactor.
Si~ilarly, electrical powe-r generated by the motor generator sets 304 is transmitted from the propulsion unit 301 to the applicator vehicle 307 throug'n a flexible electrîcal cable 318 ~lich also e~tends further on to trans-mit electrical power to the tîller-compactc)r vehicle 308.
~n operation, the road repaving system 299 is.
traveled along the road 319 whic~ is to be repaved and preferably a small upr.ight guide rod 321 is carried on a support 322 that extends forward from ~ruck 302 to enable the operator to follow a guide li~e marked on road 31~. ~s the sys~em 299 progresses along the road~ the old asphalt pavement below applicator vehicle 307 is rapidly heated and decomposed by micro~ave energy in the malmer pxe~iously de-scribedc The heated pavement is then traversed by the tlller-compactor vehicle 308 which pulveri~es, remixes, regrades and recompacts the hot pavemen~ mi~ also in the manner previously described. In some cases the degree of co~paction provided by the tiller-compactor screed 323, which causes a controlled proportion of the weight of ve-hicle 308 to bear do~ against the pavement is suficient 313~

to provide the desired repaved road surface. I~ihere fur-ther co;npaction is needed, vehicle 30'3 may be eq~ippe~
with a roller which follows screed 323 or a separate roller co~pactor vehicle may ~ollow the-sys,e~ 299.
The rate at which the system described above can effect the repaving of an asphalt roadway is a func-tion of several factors among which is the microwa-ve po~er input to the underlyin~ pavement at applicator vehicle 307.
Under most circu~stances the system is traveled at the lO maximum speed that is consistent wi~h heating the pavement beneath applicator vehicle 307 to the temperature ranges hereinbefore discussed. This power input to the pavement at the applicator vehicle is ultimately limited by the power-generating capacity o~ the motor generator sets car-15 ried on the propulsion unit 301 but ~ithin that limitation the length of the applicator vehic:le 307 is also a factor in the po~er ir.put to the pavement. In general, achieving higher production rates may dic~ate longer ~icro~ave appli-- ca-~or portions of the system~ This is also true to some 20 extent o the tiller portion o~ the system as a series of several tillers or the like may ~e desired in order to .
enable faster travel of the system~ Ho~2ver, l~ngthening of the applicator vehicles or the tiller co~pactor vehicles for such purposes may itself have certain disadvantages a 25 under some working conditions~
Most notably, both t~e applicator vehicle and the tiller-compactor vehicle may often be formed to be very broad in order to span an ~tire roadway or a wide strip of r~ ~

road~ay so that the road may be repav~d ;n its entirety with one passa~e of tne system along the roadbecl or a small number of suc~ passages. If tLle applicator and tiller-compactor vehicles are t~en also made very lo~g ~o increase produc~ivity, the system is then composed of a series of vehicles whicll are very bulky and heavy. I~hile t~,~at is not necessarily a problem at any one specific job site, it may prove to be dif~icult to transport the apparatus to di~ferent remotely located j ob sites. A somewhat related factor is that there are a limited number of articulations in the total system as described above and these are separated to an in-creasing extent if the length of component vehicles is in-creased. This affects the abili.y of the successive syste~
co~ponents to track precisely behind the propulsion unit.
lS The latter problem may of course be eliminated by providing individualized steering systems at each component vehicle of the system but tha-t requires much of the attention of operators who could otherwise be employed in other capacities in the operation o~ the apparatusO Figures 20 and 21 illus-trate a modified form of road repaving system 324 havinglengthy microwave application and tiller sections but in which transportation of the equipment bet~een iob sites is ~ore easily accomplished, which IOllOWS along a preselected track more precisely and which can accommodate to curved roads and undulating roadbeds more readily.
Basically these objectives are realized in the system o~ Figures 20 and 21 by separating the microwave appli-cator portion of the system and t~e tillex-co~2actor portion o~ the system into a plurality of separate relatively short vehicle sections and, in tl-e process, increasing ~he number oE articulations in the system as a ~hole.
In particular, the system 324 ~y employ a pro-pulsion unit 301 which may be a truck 302 carrying a pair of motor generator sets 304 which eed e~haust to a gas housing 306, the propulsion unit being si~ilar to the corresponding portion o the previously described xoad-repaving system.
However, the microwave applicator section 326 of the system 324 and the tiller-compactor section 327 are of modified construction~
The microwave applicator section 326 is comprised of a plurality of co~ponent applicator vehicles o which two such applicator vehicles 328 and 329 are utilized in this example although additional ones may be present if desired.
Microwave applicator vehicles 328 and 329 may have a~y of the intexnal constructions hereinbefore described except in-sofar as each vehicle is relatively short in the direction of travel, preferably having a length which does not exceed the maximum legal width of loads which are to be ca~ried along public highways on the bacX of a truck. Although not limitative, vehicle lengths of about six to eight feet (1~8 m.
to 2.4 m.) may be most ~onvenient The towing and steering linkages 331 through which applicator vehicle 328 is coupled to the propulsion unit 301 and through which applicator ve-hicle 329 is coupled to vehicle 328 may be disassembled and removed during such transport of the equipment.
Each o the applicator v~hicles 328 and 329 cax-ries a gas conduit 332 on vertical supports 333 or supply-ing hot exhaust gas to the microwave heating region as previously described, and sections of flexible bellows pleated gas conduit 334 interconnect the gas housing 306 of the propulsion unit with the conduit 332 of the first applicator vehicle 328 and connect the adjacent ends oE
the cond~its 332 of the two applicator vehicles. Similarly, flexible electrical cables 336 transmit electrical power from the propulsion unit 301 to the first applicator vehicle 328 and then on to the second applicator vehicle 329.
While the repaving system 33~ of Figures 20 and 21 has the advantage of being disassemblable into relatively small units which may be more conveniently transported and has a large number of articulations to provide greater ~lexibility in -traveling along curves and along roadbeds of varyiny or undulating gradient, a further result oL this construction is that in the absence of counter-acting arrangements, the heated pavement would be exposedto the atmosphere and subject to some cooling during the several intervals which intervene between passage of successive components of the system over a given area oE
pavement. Although such heat loss is not overly severe under many conditions the process is more energy-efficient if cooling is inhibited at these times. For this purpose, a flexible pleated cover 337A, formed of thermal insulation, may be carried between the first applicator vehicle 328 and the following applicator 329. Cover 337A preferably extends downwardly at each side of the heated zone of pavement between the two vehicles as certain of the forms of microwave trapping structure ~ereinbefore described, such as the gap trap or chain trap for example, enable the hot exhaust gas which is present under the applicator vehicles to enter the ~t 733g re~ion ~Ji~hin Ele~i~le cover 337 and therel~y furthex in- ~ -hibit cooling of tl~c pavement.
Tlle tiller-cor~acto-f section 327 of the system is also o~ a sectionalized or modul2r col~figuration for reasons similar to those described above wi~h reference to the micro~ave applicator section. Tllus a first relatively short tiller vehicle 338 containing, for example, two of the tiller and drag blade assemblies hereinbefore described may be spaced ~rom the final microwave applicator 329 and may be to~ed and steered through linkage 339 o the fon~
previously described. Another flexible plea~ed cover 337B
may be carried bet~7een the t~o vehicles to inhibit cooling of the heated and decomposed pavement following passage o the final applicator vehicle and prior to arrival of the initial tiller vehicle. Another gas conduit 341 is carried above tiller vehicle 338 to supply hot gas to the underlying pavement constituents during remixing as previously described, the gas conduit being coupled to the coxresponding conduit 332 of the final microwave applicator ve~icle 329 through another flexible bellows pleated flexible conduit 334C.
The inal tiller vehicle 342 may be essentially similar to the initial tiller vetlicle 338 except that it carries the screed 343 for providing the ~inal grading and compaction operation. Screed 343 may be situated behind the body of the final tiller vehicle 342 and may be coupled to the vehicle through pivotable drag arms 344 essentially as previously described. Hydraulic cylinders 346 are coupled to the drag arms 346 to control the vertical level `~
of the screed 343 ~hile the externally mounted screed and 3~

su2porting ancl con~ro~ structures add to the lenOth of ~he f:Lnal tiller vehicle 3~2, such external elemen~s are roadily re~.ove~l ~hen ~.he appara~us is to be trucl;ed t:o a different worl; s te.
Ho~ e~haust gas is supplied to the final tiller unit 342 through a final section of insulated conduit 347 carried vn vertical supports 348 and coupled to ~he corre-sponding~ conduit 3~1 of the initial tiller section 338 through another section of bellows plea~ed flexible conduit : 10 334D Si~ilarly, electrical power is transmitted back to the final tiller ~7ehicle 342 through still another section of fle~ible electrical power cable 336D extending forward to the preceding tiller venicle 338.
The road repaving systems described above with reference to Figures 18 to 21 are primarily designed for large-scale operations Smaller systems havin~ considerably different vehicle configurations may also be utilized in :~
the practi~e of the invention, a first example of which is ~ depicted in Figures 22 and 23, . :
.~ 20 The vehicle depicted in Figures 2~ and 23 is .; termed a surface resettin~ vehicle 351 since in addition : to being sui~able for recycling existi~lg aspha~tic pavement in the manner previously described, it is also paxticularly well adapted to a variation of the process which is ~ermed 25 resetting as distinguished from repaving. Still -Eurther, -it is adapted for a variation of the process which is ~ppli-cable to the ~aintenance of higl~7ays formed primarily of . concrete.
,, :

- 75 - ~

~ ' l`he surFace rese~ting vehic:le 351 has a fronL
section 352 ridi.ng on a pair of ro~d ~heels 353 and a longer rear sec~ion 354 suppor~ed a~ the back end by t~70 sets o~ powered road wheels 356 an~ 3~/. Thc surface resetting vehicle 351 of this exam?le is an artic~lated vehicle of the type in which the front section 352 and the rear section 354 are linked together at a high-strength pivot connection 358 situated centrally between the ~wo vehicle sections and whîch enables pivoting of one vehicle section rela~ive to ~he other about a vertical axis while being rigid against any pivoting movetnent abou~ any orthog-onal axes. As is customary in articulated vehicles of this general form, a pair of hydraulic steering cylinders 359A and 359B are coupled between the two vehicle sections with each cy~inder being situated at an oppos;te side of the pivot connection 358 so that lextension oE one cylinder accompanied by contraction of the other forcibly angles the front section 352 relative to the back section 354 to enable steering of the vehicle.
The fron~ section ~52 is a miGrowave applicator ~hich m~y have an internal construction similar to that of one of the microwave applicator vehicles hereinbefore described and whi.ch thus establishes a microwave heating and decomposing region 361 helow the body 362 of the ve-hicle with the microwave heating region being bounded by a trapping region 363 of one of the forms hereinbeore de scribed to prevent the escape of microwave energy from the gap between the underside of th~ vehicle and the pavement.
Electrical power for operating the microwave applicator co~?onents a~ tn~ f~ont section 352 is receive~ Lhrough a fleA~ible po~2r cable from. a g~nerator 356 carrie~ on the rea~ section oE the vehicle.
- The rear sec~ion 354 of tile surEacc resetting vehicle has an operator's compartment 367 carried on the for~ard porLion of a fra~e 368. ~n insulated tank 369 for supplementa~f asphalt, paving oil or conditioners is carried near the back of frame 368 pxeferably over the rearmost supporting road wheels 356. Genera~o~ 366 is driven by an engine 371 with the generator and driving engine being situated forward from the tank 369 and with the outpu~ ter~inals 373 of the genera~or being connected to an electrical power cabinet 372 situated i~mediately behind the cab to contain the rectifiers, voltage regu- ;
lators and the like for the microwave generators. Engine 371, which supplies all po~er for this exa~ple of the surface resetting ~ehicle 351,is preferably of the turbine for~ as turbine engines produce a relatively large amount of hot exhaust in comparison with piston engines and cer $ain operations for which the resetting vehicle 351 may be utilized preferably employ relatively large amounts oX
hot gas as will hereinater be discussed in more detail.
Although a separate driving engine can be pro-vided if desired, a more compact and less costly vehicle construction may be realized by utiliz.ing part of the power output of generator 366 as a source of motive energy for the vehicle. For this purpose, an electrical motor 374 having terminals 376 coupled to power cabinet 372 is carried on frame 368 adjacent generator 366, The output ` ~

shaft 377 of motor 37~ is drivingly coupled to road wheels 357 and 356 throuyh suitable speed reducti.on gearlng 378.
Still another electrical motor 379 may be carried on the ~rame 368 to drive a pump 381 for pressuri~ing hydraulic fluid froln a hydraulic tank 382 to operate the several actuators on the vehicle which will hereinafter be described.
Frame 36~ defines an inverted rectangular box-like structure beneath which tilling, scarifying, gradiny or other operations may be performed on heated decomposed pavement as will be discussed in more detail. Tc provide for a supplementary heat input into the underlying pavement durin~ such operations, ducting 382 transmits the exhaust gas o~ eng.ine 371 downward to the region within frame 368.
15 ~ro aid in retaining hot gas around the area of such operations and to prevent the impelling of pavement constituents outwardly from under the vehicle, flexible skirts 383 extend do~nward to the pavement from the front, back and side edges of frame 368. A valve 384 in ducting 382 provides for the selective diversion of a portion o~ the exhaust gas of engine 371 to a conduit 386 which delivers such heated gas to tank 369 when this is necessary to maintain the contents of the tank in a heated condition.
In order to per~orm any of several Eurther operations on pavement which has been heated and decomposed by microwave energy by the front section 352 of -the vehicle, one or more pavement-working mechanisms are carried within the frame 368 and in this example include a rotary tiller a 387, a rake or scarifier 388 and a grader blade 389. Rotary tiller 387, carrying cutting and mixing heads 391, may be of .

the form previously described and has a drive shaft 392 which is journaled in the lower ends of support arms 393 that have upper ends pivotably coupled to-the sides of frame 368 through axles 394. Hydraulic actuators 396 on frame 368 may be extensible and contractable rods 397 engaged in longitudinal slots 398 on arms 393 to provide for controlled raising and lowering of the tillers relative to the underlying pavement. The tiller may be driven by a drive chain 399 linking a gear 401 on drive shaEt 392 with another gear 402 disposed coa~ially on axle 394 and which is driven by an electrical motor 403 secured to frame 368.
Rake 388 may include a transverse member 404 haviny one or more rows of linear spaced-apart tines 406, of which there are three rows in this example, extending downward from the underside in order to rake or scarify the surface of the underlying heated pavement. Memher 404 may be secured to the lower ends of support arms 407 at each side of the vehicle with the upper ends of the support arms being pivotably coupled ~o ~rame 368 to enable selective raising and lowering of tines 406 by hydraulic actuators 408.
Blade 389 may be a transverse member carried within frame 368 behind rake 388 with the upper end of the drag blade being coupled to support arms 409 at each side of ~5 the vehicle that have upper ends pivoted to frame 368. A
hydraulic actuator 411 is carried on frame 368 at each side of the vehicle and is coupled to the blade support arm 409 L :
at that side to provide for selective raising and lowering of the blade 389 relative to the pavement to perform grading and smoothing operations.

'~' ' ' ` :`

The surface resetting vehicle 351 may, if desired, be utilized to perform the pavement-recycling process as hereinbefore des ~ ibed. The vehicle 351 may be driven along a strip of pavement at a rate at which the pavement underlying microwave application zone 361 is heated and decomposed. Tiller 387 may then be lowered to remix the decomposed pavement constituents and blade 389 may then be ; used to regrade the remixed pavement. The present example of the vehicle is followed by a separate compactor vehicle 10 although it will be apparent that a screed may be mounted on vehicle 351 for this purpose as previously described with respect to another embodiment of the invention.
The vehicle 351 may also be utilized in what is termed a pavement sur~ace resetting operatlon which differs 15 from the process previously described in that decomposition by microwave heating under the application zone 361 is limited to less than the full depth of the old asphaltic pavement.
Instead, only a surEace layer of the old pavement, typically of the order of one or two inches or three to five centimeters 2~ in depth, is decomposed~ While this decomposed surface layer of the old pavement may be remixed with tiller 387 and then graded with blade 389 and may then be recompac-ted, I
reconditioning oE the surface layer of the pavement may also be accomplished in many cases simply by raking or scarifying ~5 the heated decomposed surface layer wi`th rake 389. For this purpose, rake 389 is lowered to penetrate tines ~06 the appropriate depth into the surface layer of the pavement while the vehicle is traveled along the decomposed pavement. The pavement may be repetitively raked in this manner by 30 periodically reversing the direction of travel o~ surface resetting system 351 at successive areas of the pavement and, where necessary, supplemental asphalt from tank 369 may be released into the pavement prior to or between stages of raking. Subsequently the decomposed and raked or stirred surface layer of pavement may be smoothed and regraded by driving the vehicle to sweep the lower edge of blade 389 through the reworked area. ~, Hot exhaust gas from engine 371 is directed lnto the decomposed pavement constituents during the above-described raking or tilling operations through ducting 382to reduce the amount and time of microwave heating needed.
A surface heating action such as that provided by the hot exhaust gas is somewhat more eEficient in a surEace ~esetting operation of this kind than is the case where the pavement must be hea-ted and decomposed to greater depths.
For this reason and because a lesser amount of remixing may i be satisfactory in a surEace resetting process, the degree of microwave heating which is required may be somewhat less than in the case o~ full recycling of the old pavement, microwave heating to temperatures in the range from about 180F~ (80c.) to about 200F. (95c.) being satisfactory in the case of a surface resetting process.
Variations of the method of the present invention may be advantageously utilized in the repair and maintenance 2~ oE deteriorated concrete highways and may also be used to recover discarded asphalt from old dump sites. In particular, the practice of re~urbishing deteriorated concrete highway pavement 412 by overlaying a relatively narrow layer of asphalt pavement 413 has recently come into practice to a limited extent utilizing conventional asphalt paving techniques and apparatus. This application of an overlay of asphalt pavement 413 to a concrete highway 412 or the like can be accomplished very efficiently by using the method and apparatus of the present invention but unlike the pavement recycling operations previously described, it is necessary to truck in the asphalt pavement constituents when the overlay is first applied to the concrete. While new asphalt pavement constituents may be used to initially lay down the asphalt pavement overlay 413, the method and apparatus of the present invention enables a highly efficient use of old discarded asphalt pavement chunks, recovered from a dump site, for such purposes. In particular, a layer 413 of small chunks of old asphalt pavement recovered from a dump site may be spread out in a 15 layer 414 on the concrete pavement of the rod which is to be j~
reconditioned. The vehicle 351 of Figures 22 and 23 or any oE the other roadpaving vehicles or systems hereinbefore described may then pass over the layer 414 to successively heat~ decompose, remix and regrade the old asphalt pavement ~0 to form the desired asphaltic overlay 413 at the surface of concrete hi~hway 412. In this particular usage at least the front and rear microwave trapping structures 416 and 417 respectively on the microwave applicator portion of the systenl should be of a particular one of the previously ~ ;
~5 described forms that is capable of allowing passage of the loose chunks 414 under the trapping structures without ~ ¦~
substantial disturbance. Flexible skirt traps and gap traps of the previously described forms meet this requirement.
Following the initial overlay of a concrete highway 412 with a relatively thin asphalt layer 413, the surface I

resetting system 351 may then be perlodically utilized to repeatedly recondition the road surface at intervals, as previously described, without necessarily requiring new paving materials.
Techniques and apparatus in accordince with the invention are also applicable to the patching and repairing of scattered localized relatively small areas of deteriorated pavement under circumstances where it is not desired to repave a large continuous area of the pavement. While the previously described system may be utilized for such purposes, relatively small jobs and the patching of small localized areas such as scattered cracks, potholes and the like can be more economicaLly accomplished with a smaller vehicle carrying components suitable for performing certain steps of the process. Figures 24 and 25 in conjunction illustrate an exarnple of such a smaller vehicle which i5 termed an asphalt patching and resetting vehicle 418 as it is particularly well adapted for such operations although it may also be used to repave or reset a lengthy continuous strip of pavement in the ; 20 manner hereinbefore described.
; Patching vehicle 418 may have a frame 419 carrying an operator's cab 421 and riding on a pair of steerable front road wheels 422 and on a compactor roller 423 which is journaled to the back end of frame 419 by a cross axle 424.
To drive the vehicle in the forward and backward direction, a reversible electric motor 427 is mounted on a platform 428 above roller 423. ~ears 429 at each end of the output shaft of motor 427 drive larger gears 431 disposed coaxially on each end of roller axle 424 through a pair oE drive chains 432 which couple each year 429 with the gear 431 at the same side of the vehicle.
To provide power for the several electrical components of the vehicle 418, a motor generator set 433 including a yenerator 436 and driving engine 438 is carried ~bove frame 419 and an electrical power supply and control cabinet 437 is carried behind cab 421. The engine 438 of the motor generator set is a diesel engine 438 or other suitable fuel-burning engine of the form which produces hot exhaust.
A microwave applicator unit 439, contained within an inverted rectangular boxlike housing 441 formed of eLectrically conductive material, is disposed at the underside of the forward portion of the vehicle to heat and decompose asphalt pavement at localized areas which are to be repaired.
Applicator section 439 may have internal elements similar to that of the corresponding components oE the applicator vehicles hereinbefore described and may, for example, thus include transversely disposed lossy waveguides 442 each energized by a magnetron tube 443 or other suitable microwave genera`tor. Trapping reyions 444 are situated around the periphery of the region of waveguides 443 to block the release of microwave energy at the gap between the lower edge oE
housing 441 and the underlying pavement 426 and may be of any of the forms hereinbefore described. Preferably the microwave applicator unit housing 441, in which the waveguides 443 and other internal components are disposed, is suspended from frame 419 by actuators 446 for selectively raising and lowering the housing 441. In addition to providing for adjustment of the gap between the microwave applicator unit ~84-;3 3~

and the underlying pavement, this enables vertical retraction of the housing 441 and internal components when : the vehicle is to be traveled along the road or the like between areas which require patching~
~ 5 Also disposed at the underside of frame 419, : between the microwave applicator section 439 and roller 423, is a pavement reworking section 447. Reworking section 447 ~ may again be formed of an inverted rectangular boxlike body 1 448 ay~in preferably suspended from frame 419 through actuators 449 which enable raising and lowering of the section both to adjust reworking depth in the pavement and to enable vertical retraction of the section when the :
vehicle is to be traveled between work areas. Reworking section body 448 may contain any of the several remixing components hereinbefore described in connecticn with other embodiments of the invention and in tllis example includes a ~ :
rotary tiller 451 and a scarifier or rake having rows of tines 452. It should be understood that the pavement reworking implements useful in the present invention are not limited to the tillers and rakes heretofore described for purposes of example but may include other components which provide for cutting, stirring, mixing and the like of l~
decomposed pavement. For example, rows of plowing discs 453 of the form heretofore used for agricultrual operations, may ~ ~:
also be carried in the reworking section 447. To enable regrading, a final element carried at the back of the ~.
reworking section 447 is a grader blade 454.
A pavement temperature sensor probe 456 is carried ;~
below frame 419 between the microwave applicator section 439 -~5-,~`.!
i., ,'' ' . . ' '' ~ ~ .

~9L733~

and the reworking section 447 to enable the operator to determine when an area of pavement to be patched has been heated to the desired temperature. Similarly, microwave energy detectors 457 of suitable known forms may be mounted on frame 419 preferably above the four corners of the microwave applicator section 439 to detect any escape of microwave energy. In order to make most efficient use of the energy content of the fuel consumed by the vehicle engine 438 as well as to enhance the microwave heating operation and pavement reworking operations, ducting 458 may again be provided to transmit the hot exhaust gas from the engine to the pavement reworking section 447 and also to the microwave heating region below microwave applicator section 439.
~5 In operation for such purposes as patching small ; localized deteriorated areas in pavement 426, such as potholes or cracks, the vehicle 418 is initially driven to a position where the microwave ap~licator section 439 is situated over t~le area to be reworked and the pavement within and immediately surrounding the deteriorated area is then heated and decomposed. The vehicle is then traveled forwardly and, if necessary, is traveled in repetitive forward and backward motions to enable the remixing or scarifying mechanisms within the reworking section 447 to remi~ or stir the decomposed pavement area. Thereafter the vehicle is traveled forwardly to regarde the reconditioned area with grader blade 454 and then to compact the regarded area with roller 423.
In addition to facilitating the repair of small isolated deteriorated portions of the pavement 426 as -8~-~ .

_\ ' described above, the patching vehicle 418 is also highly suited to recycling of the asphaltic pavement which often forms a narrow shoulder strip along highways that are primarily formed of concrete. For such an operation the vehicle 418 may simply be traveled slowly and continuously along the asphalt shoulder to perform in sequence the several necessary operations as previously described with reference to larger vehicle systems.
ReEerring now to Figures 26 and 27, the invention may be prac-ticed on a large scale in a highly efficient manner without necessarily requiring use of the complex specialized vehicles previously described. Figures 26 and 27 illustrate still another large road repaving system 461 which, aside from a component microwave applicator vehicle 462 of the specialized for`m hereinbefore described, is composed of components which~ taken individually, are known commercially available devices having only some easily accomplished structural modifications.
The propulsion unit of the system 461 may again be a large flat-bed self-powered truc~ 463 carrying a pair of motor generator sets 464 with the exhaust gases of the diesel engines or the like which drive the generators being collected in a gas housing 466 also carried on the truck, the propulsion unit being similar to that previously described with respect to other embodiments oE the invention. Similarly the microwave applicator section 462 may be a microwave applicator vehicle 467 of any of the previously described forms that is towed by truck 463. As in certain o~ the previously described embodiments, ~.......... , . ,, , .. ~

L733g applicator vehicle 467 has an insulated hot gas conduit 468 receiving hot gas from housing 466 of the truck through a flexible, expandable and contractable bellows conduit 469 that connects with a blower 471 on the truck and draws gas from housing 466. Applicator vehicle 467 preferably includes a valve 472 through which an adjustable gas flow from conduit 468 may be directed to the microwave heatin~
region. Although a single such microwave applicator vehicle 467 is u-tilized in this example of the s~stem 461, additional microwave applicator vehicle may be connected into the system in tandem if desired.
Unlike the previously described embodiments, the remixing, grading and recompacting steps in the system 461 are per~ormed by a paving machine or paver 473 most portions 15 of which may be of conventional construction. `~
Salient elements of a paver 473 include a body 474 `` riding on support wheels 476 and on large drive wheels 477.
An engine 478 carried on body 474 powers the vehicle. A
paver also typically includes a hopper 479 for receiving hot mix. An endless belt conveyor 481 extends forwardly and downwardly from the front of the hopper, within a receiving chute 4B2, to pick up asphaltic hot mix and to lift and convey the mix into the top of hopper 479.

., , In the conventional usage of a paver, asphaltic hot mix is trucked to the work site and deposited in a windrow in front of the path of the paver where it is picked up by the conveyor 481 and deposited in hopper 479. The paver has another endless belt conveyor 483 which carries the hot mix from the lower end of hopper 479 backwardly to ``

the rear portion of the vehicle where it is discharged onto .

., 733~

a transversely disposed trough 484~ A layer of the hot mix is then deposited on the roadbed from the trough~ Where, as in this example, the extent of the trough 484 is greater than the width of the conveyor 483, a powered screw or auger type of conveyor 486 may be disposed transversely of the vehicle in trough 484 to carry a portion of the material in the conveyor sidewardly from the belt conveyor 453 so that it is deposited in a uniform layer across the roadbed. For this purpose the auger elements 487 of conveyor 486 spiral in opposite senses at each side of the center line of the vehicle.
To yrade and compact the deposited mix, a screed ~88 is disposed transversely beneath the back end of the paver 473 to ride against and compress the freshly deposited layer. Screed 488 may be pivotally coupled to one of a pair of drag arms 489 at each side oE the vehicle and the drag arms extend forwardly and upwardly from the screed and are coupled to the body of the vehicle at the forward ends by pivot means 491. One of a pair of hydraulic cyllnders 492 ~0 is connected between the back portion of each drag arm 489 and the body of the vehicle to provide for a controlled adjustment of the vertical level of the screed 488.
Considering now certain modifications which are preferably made to the paver 473 to enable it to function as a component of the repaving system 461 in the most efficient manner, the chute 482 at the Eorward end of the paver which receives hot mix is preferably formed to be sufficiently broad at the forward end to intercept the entire width of the strip of pavement 493 which is to be recycled. Where 33~

this requires a chute having sizably greater width than the assoclated conveyor 481, the transport of intercepted decomposed old pavement onto the conveyor and up into hopper 479 may be facilitated ~y disposing another powered screw-type conveyor 494 immedia~ely above the forward edge 496 of the chute which edge is shaped to form a scoop for picking up the decomposed old pavement. Screw conveyor 494 may be similar to the previo~sly described rear conveyor 486 except insofar as the auger elements spiral in a reversed clirection lQ in order to draw intercepted material towards the center line of the paver rather than to carry it outward towards ; the sides as in the case o~ the rear conveyorO
nother readily accomplished modification of the paver 473 which facilitates the present method, is to ~ ;
dispose a cover 497, preferably formed of thermally insulated material, across the top of receiving chute 482 and to dispose an essentially similar cover 498 above hopper 479. By this means hot exhaust gases may be retained around the path of the decomposed pavement mix as it passes through the paver. To receive the hot exhaust gas r an inlet fitting 499 may be provided at the top of cover 498 and another section 501 o~ Elexible pleated gas conduit connects the fitting 499 with the back end of the gas conduit 468 of the microwave applicator vehicle 467.
As many conventional pavers are designed to pick up premixed pavement constituents, mixing mechanisms may not be provided on such vehicles. In the system of Figures 26 and 27, a considerable amount of mixing of the intercepted decomposed old pavement occurs inherently through the 733~

actions of the several mechanisms descrlbed above. A mixing e~fect occurs initially at the forward screw conveyor 494 and to some extent through the action of the initial conveyor 481 and in the course of the dropping of the material into the hopper 479. Further mixing action occurs at the rear screw conveyor 484. In instances where the paver construction does not otherwise provide a sufficient degree of remixing, one or more powered rotary tiller mechanisms 502 of the previously described form may readily be installed in the paver, for example immediately above the ; rear conveyor 483. As pressurized hydraulic fluid is usual~y already present on a paver for the purpose of operating various hydraulic cylinders, a rotary fluid motor 503 may be used to drive the tiller mechanism 502 although other forms of drive motor may also be employed.
As indicated in Figure 27 in particular, the above-descr.ibed construction establishes a beneficial directi.on of hot exhaust gas into the decomposed pavement mix within the paver and against various components which come in contact with the mix. From fitting 499, hot gas flows between chute 482 and conveyor 481, into hopper 479, above conveyor 483 including through the mixing region at tiller 502, and to trough 484 and screed 488. Referring to Figure 26 in particular, if the hot gas flow produced by the motor generator sets 464 should not be adequate to meet the demand for both the microwave applicator vehicle 467 and the paver 473, the hot gas flow may be supplemented by providing ducting 504 to also transmit the exhaust from paver engine 478 down into the region below cover 479.

. ,...~
. ;, --91--In other instances, the gas conduit connection 501 between the paver 473 and the microwave applicator vehicle 467 may be eliminated and the exhaust gas of paver engine 478 may then be relied on, through ducting 504, to supply the needs of the paver. It is of interest in this connection that in conventional paver constructions, a butane burner or the like is often provided to maintain the contents of hopper 479 in a heated condition. It has apparently heretofore escaped notice that the paver engine `;
10 478 in these prior constructions may be discharging and i wasting around 70% of the energy content of consumed fuel in the form of exhaust gas having temperatures of several hundred degrees Fahrenheit or Celsius.
In operation, the system 473 is traveled slowly down a deteriorated road 506 which is to be repaved. The old pavement is rapidly heated and deconnposed below the microwave applicator vehicle 467 in the manner previously described. The decomposed pavement is subsequently intercepted by scoop 496 of the paver 473, carried towards the center of the paver by screw conveyor 494 and then channeled upwardly and backwardly into hopper 479 by chute 482 and conveyor 481 in conjunction. The recovered and heated pavement mix is then carried rearwardly from below hopper 479 by conveyor 483, undergoes further mixing by tiller mechanism 503 and is then redeposited on the roadbed in the form of a layer of hot remix which is then grated and recompacted by screed 488 to leave behind a repaved, recycled road surface. Little or no new asphalt is needed.
Materials need not be trucked back and forth between a l~`
.-.

.

distant mixing plant or dump site and a much more efficientusage of consumed fuels is realized than has heretofore been the case in paving operations.
The system of Figures 26 and 27 lends itself readily to still another highly advantageous variation of the process. Specifically, it may be desired to widen an existing road. In many cases, due to past resurfacing or overlaying operations or other causes, the depth of pavement ~;
on the existing road may be deeper than is actually needed.
10 Where that is not the case, a relatively small amount of new ~ ;~
paving mix may be brought in and deposited on the old `
roadbed in front o~ the system ~73.
If the rear screw conveyor 484 and screed 488 of the paver are then selected to have dimensions capable of spanning the desired widened surface, then it may be seen that the above-described system acts to provide the desired wider road by utilizing at least in part the materials of the older, narrower road. Thus as indicated diagrammatically in Figure 27, the system 473 may be -traveled down an old, narrow roadway 507 leaving behind the widened repaved road surface 508.
The invention was intially developed primarily for use at pavements which are asphaltic or where asphalt is overlaid on concrete. Certain aspects of the invention are also useful with non~asphaltic pavements. For example, it has been pointed out that microwave energy enables a very rapid and efficient heating of concrete. Certain known concrete maintenance operations re~uire the on-site heating of the pavement to dry the concrete and in some cases to aid _93--~7~3~

polymerization or other setting processes of sealants or the like which are applied to the pavement. Heretofore such heating has required long periods of time as it has been necessary to rely on the slow conduction of heat downward from the surface of the concrete which material inherently has a low coefficient of thermal conductivity. The microwave applicator devices hereinbefore described are a much more efficient and rapid concrete heating system for such purposes. In such usages of the microwave applicators~ the remixing components, compaction mechanisms and the like of the previously described road reapiring systems are not necessarily required.
While the invention has been described with ` respec~ to specific embodiments, it will be apparent that many modifications are possible and it is not intended to limit the invention except as defined in the following ` claims.

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~5

Claims (30)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method for recycling existing asphalt pavement comprising the steps of:
establishing a microwave energy containment region above said pavement including positioning microwave energy emitting waveguide means in spaced apart relationship from said pavement to provide a gap enabling travelling of said waveguide means without direct contact with said pavement, travelling said containment region along said existing asphalt pavement while concurrently generating heat with-in the interior of said pavement, to soften the asphalt content thereof, by directing microwave energy into said pavement from said containment region while travelling therealong, including distributing said microwave energy substantially uniformly across the width of a strip of said pavement over which said containment region is travelled, suppressing outward propagation of microwave energy from said containment region through said gap while travelling along said pavement, subsequently remixing the constituents of said pave-ment while said pavement is in the softened state, and recompacting the remixed pavement constituents sub-stantially at the original location thereof to provide renewed pavement thereat.

2. The method of claim 1 wherein said microwave energy propagataes outwardly from said containment region within said gap and wherein said step of suppressing outward propagation of microwave energy from said containment region is accomplished at least in part by reflecting the upwardly directed component of said outwardly pro-pagating microwave energy down into said pavement for absorption therein and thereby causing a progressive attenuation of microwave energy intensity in the outward direction within said gap.

3. A method for recycling existing asphalt pavement as set forth in claim 1 comprising the further steps of:
producing said microwave energy by operating a microwave source with electrical power from a generator driven by a fuel-consuming engine, and directing at least a portion of the hot exhaust of said engine to said pavement to supplement the microwave heating thereof.

4. The method of claim 3 wherein said hot exhaust is directed at said pavement in the same area thereof that receives said microwave energy.

5. The method of claim 3 wherein said hot exhaust is directed at said pavement constituents during said remixing thereof.

6. The method of claim 1 wherein said step of estab-lishing a microwave energy containment region above said pavement is accomplished by disposing electrically con-ductive material above said region and around the sides thereof and by releasing said microwave energy into the region bounded by said conductive material and the under-lying portion of said pavement while travelling said region including said conductive material along said pavement.

7. The method of claim 1 wherein said decomposing of said existing pavement by microwave energy and said remixing of the constituents thereof is confined to a surface layer of said existing pavement.

8. The method of claim 1 wherein said existing asphalt pavement is a layer of asphalt pavement overlaid on concrete pavement.

9. Apparatus for heating pavement in place at a paved surface while travelling therealong comprising;
a vehicle with support means for enabling travel along said pavement, microwave applicator means supported on said vehicle for travel along said pavement therewith while applying microwave energy thereto, said applicator means including a microwave containment structure having an electrically conductive top portion spaced above the underlying surface along which said vehicle travels and having electrically conductive side portions extending from said top portion downward toward said underlying surface to define the upper portion of a travelling microwave region which is bounded by said top portion and said side portions and the underlying area of pavement and by a gap between said side portions and said underlying pavement, said applicator means further including a plurality of waveguides positioned to distribute microwave energy substantially uniformly across said underlying area of said pavement and to generate heat within said pavement substantially uniformly thereacross as said vehicle travels along said pavement, means carried on said vehicle for releasing micro-wave energy into said microwave region through said plurality of waveguides to heat said pavement within said underlying area thereof while travelling along said pavement, and microwave energy-trapping means for suppressing the release of microwave energy through said gap as said vehicle travels along said pavement, said microwave energy-trapping means being disposed on said vehicle adjacent to said gap in position to receive microwave energy which would escape from said microwave region through said gap beneath said containment structure in the absence of said trapping means.

10. Apparatus for heating pavement in place at a paved surface as set forth in claim 9 further comprising:
at least one microwave source carried on said vehicle, at least one electrical generator coupled to said microwave source to supply electrical power thereto, at least one fuel-consuming engine mechanically coupled to said generator to drive said generator, and means carried on said vehicle for directing at least a portion of the hot exhaust of said engine to said pavement to supplement the heating effects of said microwave energy.

11. Apparatus for heating pavement in place at a paved surface as set forth in claim 9 wherein said means carried on said vehicle for releasing microwave energy into said microwave region includes at least one microwave source carried on said vehicle, and at least one electrical generator coupled to said microwave source to supply electrical power thereto, and at least one fuel-consuming engine mechanically coupled to said generator to drive said generator, and at least one receptacle supported on said vehicle for carrying a supply of fresh supplemental pavement constituent, means for selectively delivering said sup-plemental constituent to said pavement as said vehicle travels therealong, and means connected between said engine and said receptacle for directing at least a portion of the heat from the exhaust of said engine to said receptacle to maintain said supplemental constituent in a heated condition.

12. Apparatus for heating pavement in place at a paved surface as set forth in claim 9 further comprising:
means carried on said vehicle for remixing the constituents of said pavement following passage of said microwave enclosure thereover, a fuel-consuming engine disposed on said vehicle, a generator disposed on said vehicle and being mechanically coupled to said engine and driven thereby and being elec-trically coupled to said microwave source means to energize said source means, and means carried on said vehicle for directing at least a portion of the hot exhaust of said engine at said pavement constituents during said remixing thereof.

13. The apparatus of claim 9 wherein said microwave energy-trapping means comprises electrically conductive members carried on said vehicle above said pavement in spaced-apart relationship therefrom and extending outwardly from said microwave containment structure in position to reflect the upwardly directed component of microwave energy, that pro-pagates through said gap, downwardly into said underlying surface.

14. The apparatus of claim 9 wherein said microwave energy-trapping means comprises flexible electrically conductive elements disposed on said vehicle and extending downwardly to said underlying surface at said gap beneath said micro-wave containment structure in position to reflect microwave energy, that propagates into said gap, back towards said travelling microwave region.

15. The apparatus of claim 9 wherein said microwave energy-trapping means comprises a front microwave trap extending transversely across the front of said microwave region at said gap, a rear microwave trap extending transversely across the back of said microwave region at said gap and a pair of side microwave traps extending along a separate side of said microwave region at said gap, at least one of said side microwave traps being vertically movable relative to said microwave containment structure.

16. The apparatus of claim 15 further comprising a plur-ality of ground-engaging wheels journaled to said one side trap to maintain said one side trap at a predetermined elevational level relative to the underlying surface

17. The apparatus of claim 9 wherein said microwave energy-trapping means is a gap trap comprising a plate of electrically conductive material extending outwardly from said microwave enclosure above said gap and having at least an underside which is spaced above said underlying surface in at least substantially parallel relationship thereto.

18. Apparatus for heating pavement in place at a paved surface while travelling therealong as set forth in claim 9 wherein said microwave energy-trapping means comprises a plural layered mass of individually flexible electrically conductive elements attached to said microwave containment structure and extending downward to drag along said under-lying surface.

19. Apparatus for heating pavement in place at a paved surface while travelling therealong as set forth in claim 9 wherein said microwave energy-trapping means includes a skirt trap comprising a linear strip of electrically conductive material extending along a boundary of said microwave region at said gap, said strip having an upper edge fastened to said microwave applicator means and having a lower portion which extends downward to contact said underlying surface, and wherein said strip is formed of flexible material and is proportioned to extend down-ward to said underlying surface and to bend thereat enabling the lowermost portion to lie against said underlying surface and drag therealong.

20. Apparatus for heating pavement in place at a paved surface while travelling therealong as set forth in claim 9 wherein said microwave energy-trapping means includes a skirt trap comprising a linear strip of electrically conductive material extending along a boundary of said microwave region at said gap, said strip having an upper edge fastened to said microwave applicator means and having a lower portion which extends downward to contact said underlying surface, and wherein said strip is formed of substantially rigid material and wherein said lower portion of said strip extends downward a distance greater than the height of said gap enabling the lower edge of said strip to penetrate into said underlying surface.

21. The apparatus of claim 9 wherein each of said plur-ality of waveguides of said microwave applicator means is supported on said vehicle at said microwave region in spaced apart relationship from said underlying surface along which said vehicle travels and has at least one opening for transmitting microwave energy towards said underlying surface from a zone extending along the side of the waveguide, and said means for releasing microwave energy into said region comprises microwave energy-generating source means coupled to each of said waveguides for energizing said waveguides.

22. The apparatus of claim 21 having a plurality of said waveguides disposed in parallel relationship and having a plurality of said microwave-generating sources each coupled to a separate one of said waveguides.

23. The apparatus of claim 12 further comprising a first actuator for selectively raising and lowering said microwave enclosure, and a second actuator for selectively raising and lowering said remixing means.

24. A method for heating pavement at a paved surface com-prising:
positioning microwave energy emitting means above said surface in spaced relationship therefrom to provide a gap therebetween which enables travel of said means without direct contact with said surface, generating heat within said pavement below the surface thereof by directing microwave energy downwardly from said microwave energy emitting means into said pavement while travelling therealong, including dispersing said microwave energy substantially uniformly across a zone of said pavement which extends transversely with respect to the direction of travel therealong to cause a substantially uniform temperature rise across said zone of pavement, and blocking the sideward and forward and backward escape of microwave energy through the gap between said microwave energy region emitting means and said pavement while travelling therealong, at least in part by reflecting the upwardly directed component of outwardly propagating microwave energy in a downward direction to cause absorp-tion of the reflected energy within the underlying surface thereby causing a progressive attenuation of microwave energy intensity in the outward direction within said gap.

25. Apparatus for heating pavement in place on a paved surface while travelling along said surface according to the method of claim 24 comprising:
microwave applicator means for establishing an elec-trically conductive microwave energy barrier above an area of said pavement, said applicator means being saced apart from said pavement by a gap, means coupled to said applicator means for travelling said microwave applicator means along said surface without direct contact of said applicator means with said surface, means carried on said apparatus for generating microwave energy, means coupled to said generating means for releasing microwave energy from said generating means into said pavement within the region between the barrier and said area of pavement and for distributing said energy sub stantially uniformly across a zone of said pavement extending transversely with respect to the direction of travel of said apparatus, and microwave trapping means secured to said applicator means for blocking the forward, backward and sideward escape of microwave energy from said region through the gap between said applicator means and said pavement while travelling therealong, said trapping means including at least one electrically conductive microwave reflector element extending outward from said applicator means above said gap in position for reflecting the upwardly directed component of microwave energy, which is propagating through said gap, downwardly for absorption within the underlying surface.

26. The apparatus of claim 25 wherein said electrically conductive microwave reflector element is positioned to slant downward and outward from said applicator means at said gap to contact said surface and is flexible to accommodate to irregularities in said surface.

27. In a method for heating pavement wherein microwave energy produced by a first source of heating energy is directed downward into said pavement to generate heat internally and instantaneously within the subsurface interior region of said pavement, and wherein said microwave energy heats a deeper region of said pavement more strongly than the uppermost region thereof thereby tending to produce an inverted temperature gradient in said uppermost region the further steps comprising operating a fuel consuming motor to drive a generator to produce electrical energy for conversion to said microwave energy, and counteracting said inverted temperature gradient while reducing nonproductive energy dissipation by transmitting thermal energy from the exhaust gases of said motor to the surface of said pavement to supplement the microwave heating of said uppermost region of said pavement.

28. The method of claim 27 further including the steps of establishing a hot gas confinement region adjacent said surface of said pavement and transmitting said thermal energy from said exhaust gases of said motor to said confinement region.

29. The method of claim 27 wherein said step of transmitting thermal energy to said surface of said pavement is performed by transmitting at least a portion of said exhaust gases of said motor to said surface of said pavement.

30. In a pavement heating apparatus having energy appli-cator means for generating heat within the interior of pavement over which said applicator means is disposed by microwave irradiation of said pavement, the improvement comprising:
surface heating means for applying additional heat directly to the surface of said pavement over which said energy applicator means is disposed, wherein said energy applicator means includes a housing having a top and downwardly extending sides formed of electrically con-ductive material for defining a microwave and hot gas containment region adjacent said surface of said pave-ment, at least one waveguide for releasing microwave energy into said containment region, and at least one conduit for transmitting hot gas into said housing, and microwave energy trapping means secured to the lower portions of said side walls of said housing for sup-pressing the outward emission of microwave energy from under said side walls when said housing is spaced above said surface of said pavement by a gap which would otherwise allow the outward release of microwave energy.