CA2016271A1 - Method and apparatus for repaving asphaltic pavement - Google Patents
Method and apparatus for repaving asphaltic pavementInfo
- Publication number
- CA2016271A1 CA2016271A1 CA 2016271 CA2016271A CA2016271A1 CA 2016271 A1 CA2016271 A1 CA 2016271A1 CA 2016271 CA2016271 CA 2016271 CA 2016271 A CA2016271 A CA 2016271A CA 2016271 A1 CA2016271 A1 CA 2016271A1
- Authority
- CA
- Canada
- Prior art keywords
- asphalt
- grinding
- strip
- ground
- strip portion
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C23/00—Auxiliary devices or arrangements for constructing, repairing, reconditioning, or taking-up road or like surfaces
- E01C23/06—Devices or arrangements for working the finished surface; Devices for repairing or reconditioning the surface of damaged paving; Recycling in place or on the road
- E01C23/065—Recycling in place or on the road, i.e. hot or cold reprocessing of paving in situ or on the traffic surface, with or without adding virgin material or lifting of salvaged material; Repairs or resurfacing involving at least partial reprocessing of the existing paving
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- Engineering & Computer Science (AREA)
- Mining & Mineral Resources (AREA)
- Architecture (AREA)
- Civil Engineering (AREA)
- Structural Engineering (AREA)
- Road Paving Machines (AREA)
Abstract
ABSTRACT
An asphaltic pavement preconditioning machine to remove and grind up old asphalt so that it can be rejuvenated. The method and apparatus heats a strip of asphalt, grinds a first strip portion and moves the ground asphalt to a second strip portion leaving behind an exposed unsoftened layer. Both the ground material and the previously heated unground asphalt in the second strip are then ground. The exposed hard asphalt in the first strip is heated, softened and then ground and moved onto the first strip portion. The heat from the ground asphalt lying over the center strip portion softens the unground asphalt there which is subsequently ground together with the ground material and left for further processing. At least three heating and grinding steps are effected so that the depth of asphalt requiring softening by heat is approximately 1/2 to 5/8 inches and smoke emission is substantially lower than prior methods.
An asphaltic pavement preconditioning machine to remove and grind up old asphalt so that it can be rejuvenated. The method and apparatus heats a strip of asphalt, grinds a first strip portion and moves the ground asphalt to a second strip portion leaving behind an exposed unsoftened layer. Both the ground material and the previously heated unground asphalt in the second strip are then ground. The exposed hard asphalt in the first strip is heated, softened and then ground and moved onto the first strip portion. The heat from the ground asphalt lying over the center strip portion softens the unground asphalt there which is subsequently ground together with the ground material and left for further processing. At least three heating and grinding steps are effected so that the depth of asphalt requiring softening by heat is approximately 1/2 to 5/8 inches and smoke emission is substantially lower than prior methods.
Description
:-`` 20162~1 METHOD AND APPARATU~ FOR REPAVING A~PHALTIC PAVEMENT
BACKGROUND
The present application relates to a multi-stage apparatus and process for in-place recycling of asphaltic pavement without the need to remove the asphalt to a remote reconditioning plant and then return it for use in repaving.
Single stage units which heat asphaltic pavement, rupture an upper layer of the surface, remove it from the road surface, pulverize it and then place it back on the road surface are known.
Such units, however, can not recycle more than approximately the top inch of asphalt because of the difficulty in heating the asphalt to a greater depth. The time to heat asphalt to a given temperature at a given depth depends on the square of the depth.
Thus, it takes four times as long to heat a 1/2 inch layer of asphalt to a given average temperature than it does to so heat a one inch layer.
One early solution offered by U. S. Patent Number 4,545,700 issued October 8, 1985 to Yates was to employ a plurality of stages of heating and milling or grinding the heated asphalt.
After each stage of heating and milling the ground asphalt is removed from the road surface either by windrowing the ground asphalt off to the sides of that portion of the road surface being processed or by windrowing it up onto spaced apart collection chutes~along which the asphalt moves until it reaches the next milling st~age. Windrowing the ground asphalt to the side tends to contaminate the asphalt with dirt as well as getting in the way of oncoming traffic depending on which side the asphalt is windrowed.
Lifting the material onto chutes is purely schematic as there is no practical way of holding the asphalt from spilling off of the sides or moving it along the surface of each of the chutes. In practice Yates Corp. used a conveyor to pick up the material from the road surface and carry it over the next stage of heaters. It is the latter conveyor which creates significant problems due not ~ ~ , , " ~
`'.,!: ' i :
~16271 only to its cost and high maintenance requirements but also by the amount of space it takes up. Due to the conveyors, Yates was able to include only a limited length of heaters for each stage, otherwise his vehicle would have been excessively long. Thus, he was able to heat and remove only about 1~4 inch of asphalt per stage for a total of one inch for his four stage machine. It is normally desirable to remove and recondition at least the top two inches of asphalt.
Canadian Patent Number 1,264,422 issued to Wiley and Rorison discloses a two stage process very similar to Yates which also uses a conveyor. The latter machine removes one inch per stage by employing banks of infra red heaters on each of two separate vehicles, one vehicle being used for each stage of heating and milling. Even then in order to heat the asphalt sufficiently to soften it down to a depth of one inch and still be able to travel at about 20 feet per minute, the practical minimum, it is necessary to raise the temperature at the top surface of the asphalt to 600 to 700 degrees Fahrenheit. Such high temperatures burn the asphalt at the surface and create significant amounts of smoke. An additional problem in the Wiley et al. method is the requirement of a conveyor in the second stage to carry the first stage ground material over the second stage heaters. It is the latter conveyor which limits the length of heaters possible in the second stage without the second stage vehicle being excessively long. Thus, even though the first inch of asphalt is heated sufficiently, heating of the lower second inch by the second stage heaters is marginal.
U. S. Patent Number 4,850,740 issued on July 25, 1989 to Wiley discloses a method which allows the conveyor to be eliminated altogether and to use a longer bank of heaters in the second stage machine. Wiley '740 utilizes the heated windrowed material to heat a central unground lower layer of asphalt without the need for infra red heaters to heat that portion. Such heaters are only .
"`` 2~1~271 required for the side strips from which the milled asphalt is windrowed. Both Wiley'740 and the Canadian Patent issued to Wiley disclose removing one inch per stage for a total of two inches.
However, heating down to one inch requires either long heaters or relatively slow operation or both. Attempts to run the machines faster results in insufficient heating and a greater number of rock fractures which degrades the quality of the repaving.
Raising the temperature of the heaters causes burning of surface asphalt and results'~in the creation of unacceptably large amounts of smoke. There is at the present time considerable concern that such smoke is carcinogenic. There is, therefore, a need for a method and apparatus for repaving which produces substantially less smoke than known methods and machines and which can recondition down to at least two inches of depth while maintaining a speed of operation of twenty feet per minute or more.
Accordingly, it is an object of the invention to provide an improved method and apparatus for recycling and repaving asphaltic pavement. It is a further object of the invention to provide a method and apparatus for repaving asphaltic pavement which produces less smoke than known machines and, at the same time, is capable of operating as fast or faster than known methods and machines.
SUMMARY OF THE INVENTION
The present invention provides an asphaltic road surface repaving machine of a type that removes asphalt from the surface of the road, reconditions it and reapplies it to the road surface as the machine progresses along the road. The machine includes first means for heating a first layer of the road surface pavement such that the temperature of the top surface of the asphalt is maintained at less than 500 degrees F., means for rupturing asphalt in the first heated lay ~ and windrowing the ruptured heated ~ 3 ~. .. . . .
asphalt onto a selected strip of the road surface. Next an exposed portion or portions of the road surface are heated by radiant heat while that portion below the windrowed material is heated by conduction from the heated windrowed material. The heating, rupturing and windrowing steps are repeated at least twice more until at least two inches of road surface have been removed.
Finally the removed material is mixed together, distributed and pressed back onto the road surface.
By simply windrow~ng ground material from one stage onto a selected strip of the road surface being processed and using the heat from the windrow to conductively heat the underlying unground road surface rather than picking up the windrow in a conveyor and radiantly heating the whole road surface being processed, the need to incorporate a conveyor at each stage is avoided. Moreover, by multiplying the number of stages to at least three, it is possible to reduce the thickness of road surface layer heated, ruptured and windrowed in each stage and therefore to reduce the temperature to which the surface of the road is raised to less than 500 degrees F.
Preferably the method includes heating the entire road surface being processed until a preselected depth is softened, rupturing and windrowing the ground asphalt onto a center strip portion. Heating until softened and rupturing two side strip portions of the strip and moving the ground asphalt onto the center strip portion which separates the two side strip portions. The unground asphalt in the center strip portion is ground and the two side ~strip portions again heated to soften the asphalt therein.
The softened asphalt is again ground in the two side strip portions and moved onto the center strip portion. Finally the unground asphalt in the center strip portion is ground and left for further processing. The foregoing heating, rupturing and windrowing steps is repeated at least one more time until a depth of at least two inches has been removed from the road surface.
The further processing preferably includes mixing the ground asphalt in the center strip portion with rejuvenant, heating it, pulverizing it and then applying it to the pavement. Typically the time between moving ground asphalt onto thé center strip portion and grinding it together with underlying unground asphalt is 3 to 5 minutes.
BRIEF DESCRIPTION OF THE DRAWINGS
The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as other features and advantages thereof, will be best understood by reference to the detailed description which follows, read in conjunction with the accompanying drawings, wherein:
Figure 1 is a perspective view of a four stage process implementing a preferred embodiment of the invention;
Figure 2 is a plan view of a four stage apparatus for carrying out the method which shows banks of heating elements and grinders in relationship to the ve~i~les used to support them;
Figure 3 is a side elevation view of the equipment shown in Figure 2;
Figure 4 is a plan view identical to Figure 2 except for the~spacing between tbe h-aters which extends longitudinally; and Figure 5 is a side elevation view of the vehicles shown in Figure 4; and Figure 6 is a rear elevation view showing the grinders at the rear of the apparatus.
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DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS
Referring to Figure 1 there is shown in perspective a four stage embodiment of the invention for processing asphaltic pavement. In the Figure, the direction of travel is shown by the large arrow pointing generally to the bottom left hand corner.
First the entire road surface being processed, which is typically one lane of travel, is heated as shown at location 72 until the asphalt down to approximately 1/2 inches of depth is softened. The first 1/2 inch layer of asphalt is then milled or ground by grinders 36 and 37 immediately behind heated area 72 with grinders 36 simultaneously windrowing ground asphalt into the center as shown by the arrows. The grinders may rotate either against the direction of travel or with the direction of travel.
After milling or grinding by the central grinder 37, the two exposed side strip portions 74 and 76 are heated radia~tly down to approximately V2 inch while the center strip between is heated by windrow 77 of ground asphalt material. A second set of grinders 36 and 38 repeat the grinding processed as done by the first stage of grinders 36 and 37 and again windrow 79 heats the unground center strip while~side strips 91 and 93 are heated radiantly down to~approximatély 1/2 inch. The latter heating and milling steps are repeated twice more with windrows 81 and 84 again being used to heat unground center strips while side strips are heated radiantly down to 1/2 inch. Finally, rejuvenant and possibly virgin asphalt may be added if desired as shown by arrow 86 and the ground~asphalt and virgin asphalt, if any, mixed as shown by the arrows at 90 . The mixed material is then distributed evenly over the road by a screed 88 and then rolled.
Referring to Figures 2 and 3 there is shown in plan view a first stage self propelled vehicle 10 and a second stage self-propelled-vehicle 11 pivotally attached by pivotal joint 19 to the ? 2Q16271 first stage vehicle 10. Vehicle 10 consists of a platform 16 supported by wheels 18 and 20 at either end thereof. Heater banks 12, 13, 14 and 15 are each formed by rows 50 of propane fired elongated infra red heaters 54 are arranged in side by side relationship to extend across a strip of pavement to be heated.
Spaces 52 and 53 are located between the heater rows midway along a banks 12, 13, 14 and 15 although there are tunnels or gaps 21 and 23 extending longitudinal through the center of the banks 14 and 15 which intercept the spaces 52 and 56 of vehicle 11. Tunnels 21 and 23 overlap the central w~ndrow 77 and avoid heating the latter.
At either side of space 52 there are located 3 elongated radiant heaters 56 designed to compensate for the lower heating effect at the edges of the banks of heaters 54. Wheels 18 are coupled to the front of each vehicle 10 and 11 are remotely controlled through a micro processor unit (not shown) located at the rear of vehicle 11.
Thus, vehicle 10 and 11 are free to articulate about pivotal joint 19 so that the entire unit consisting of vehicles 10 and 11 may negotiate turns more easily.
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Vehicle 10 is made up of a frame or platform 25 supported by front wheels 24 and a rear pair of wheels 26. Rear wheels 26 and front wheels 24 can both be turned in response to remote control signals applied by an operator at the rear of vehicle 11.
The grinding units for both the first and second stage are located ;~ ~ on vehicle 11 with one set consisting of grinders 36 and 37 being i located at the front and the other consisting of grinders 36 and 38 being located at the rear of vehicle 11. Each of grinders 36, 37, 38, 39, and 41 are supported by means of a V brace member 32 supported at screw connections 30 from a front beam 31 affixed to the frame 22 of vehicles 10 or 11. Rear grinder units 37, 38, 39, and 41 overlap slightly the interior edges of side grinders 36.
At the back of grinders 36 and 38 there are vertically oriented blades 40 and 42 which extend down to the level of the cutting edges of grinders 36 and~38 and in operation exerts slight ',' '. ~ ', ~ ~', :
-.: . , .
pressure on the freshly ground pavement surface. As seen in Figure 6 there is an opening 37 in the center of plate 42 to permit windrowed ground material to pass therethrough.
The platforms 25 and 22 of vehicles 10 and 11 are each used to support a variety of different equipment required to operate the units such as a propane tanks 44, a container 46 to hold rejuvenant and pump unit 48. Banks of heaters 12 and 13 are suspended from platforms 16 and 19, respectively, while banks 14 and 15 are suspended from p~atforms 17 and 22, respectively.
A second unit as shown in Figures 4 and 5 consist of two self-propelled vehicles lOa and lla identical to those of vehicles 10 and 11 except for the front vehicle lOa having tunnels 43 and 45 extending longitudinally midway along the vehicle between the banks 12 and 13 of heaters. Again tunnels 43 and 45 accommodate windrows 81 and 84. Windrow 79 is accommodated by the space between the two units of articulating vehicles 10, ll and lOa, lla.
In operation vehicles 10 and 11 are followed closely behind by vehicles lOa and lla. A single operator operates vehicles 10 and 11 and another vehicles lOa and lla with both operators located at the rear of their respective units. The way in which these vehicles process and move the material has already been illustrated in Figure 1. It is to be understood that the areas~shown in Figure 1 are only a snapshot of an ongoing process whlch progresses forwardly as the vehicles move. The ground materiaI 84 is pulverized at step 90 by a pugmill mixer (not shown).~ The mix material can then be further processed either by levelling it out with a screed 88 and then compacting it or, by picking up the ground material and directing it to a bin in which the old material is heated, mixed and spread over the pavement surface by a repaving machine of conventional design (not shown).
The speed of the machines and spacing of the grinders 37, 38, 39 and 41 relative to the banks of heating elements is such that ground windrows 77, 79, 81 and 84 are left on the top of the surface of the center strip 77 where it is allowed to soak into the underlying unground material for a period of about one to one and one half minutes. This period has been found sufficient to soften approximately 1/2 inch to 5/8 inches of the unground underlying material sufficiently so that grinding of this material is facilitated. By only slightly increasing the depth of heating and grinding it is possible to remove an additional 1/8 inches of material in each stage leading to an increased depth of recycling of 1/2 inch in all.
By confining the windrow to as small a width as possible given the volume of material removed and applying a slight amount of pressure to it as it passes the hole in the central grinder back blade the heating effect on the unground center strip in each stage is maximized.
It has been found that using the four stage machine maximum surface temperatures of less than 500 degrees Fahrenheit are achieved with a corresponding substantial reduction in emissions.
Accordingly, while this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to this description. It is therefore contemplated that the appended claims will cover any such modifications or embodiments as fall with the true scope of the invention.
'`' ':: '. . ' ., ' ` , ~. . ', "`'' " ` ' ` '~ , ` ' ' .
BACKGROUND
The present application relates to a multi-stage apparatus and process for in-place recycling of asphaltic pavement without the need to remove the asphalt to a remote reconditioning plant and then return it for use in repaving.
Single stage units which heat asphaltic pavement, rupture an upper layer of the surface, remove it from the road surface, pulverize it and then place it back on the road surface are known.
Such units, however, can not recycle more than approximately the top inch of asphalt because of the difficulty in heating the asphalt to a greater depth. The time to heat asphalt to a given temperature at a given depth depends on the square of the depth.
Thus, it takes four times as long to heat a 1/2 inch layer of asphalt to a given average temperature than it does to so heat a one inch layer.
One early solution offered by U. S. Patent Number 4,545,700 issued October 8, 1985 to Yates was to employ a plurality of stages of heating and milling or grinding the heated asphalt.
After each stage of heating and milling the ground asphalt is removed from the road surface either by windrowing the ground asphalt off to the sides of that portion of the road surface being processed or by windrowing it up onto spaced apart collection chutes~along which the asphalt moves until it reaches the next milling st~age. Windrowing the ground asphalt to the side tends to contaminate the asphalt with dirt as well as getting in the way of oncoming traffic depending on which side the asphalt is windrowed.
Lifting the material onto chutes is purely schematic as there is no practical way of holding the asphalt from spilling off of the sides or moving it along the surface of each of the chutes. In practice Yates Corp. used a conveyor to pick up the material from the road surface and carry it over the next stage of heaters. It is the latter conveyor which creates significant problems due not ~ ~ , , " ~
`'.,!: ' i :
~16271 only to its cost and high maintenance requirements but also by the amount of space it takes up. Due to the conveyors, Yates was able to include only a limited length of heaters for each stage, otherwise his vehicle would have been excessively long. Thus, he was able to heat and remove only about 1~4 inch of asphalt per stage for a total of one inch for his four stage machine. It is normally desirable to remove and recondition at least the top two inches of asphalt.
Canadian Patent Number 1,264,422 issued to Wiley and Rorison discloses a two stage process very similar to Yates which also uses a conveyor. The latter machine removes one inch per stage by employing banks of infra red heaters on each of two separate vehicles, one vehicle being used for each stage of heating and milling. Even then in order to heat the asphalt sufficiently to soften it down to a depth of one inch and still be able to travel at about 20 feet per minute, the practical minimum, it is necessary to raise the temperature at the top surface of the asphalt to 600 to 700 degrees Fahrenheit. Such high temperatures burn the asphalt at the surface and create significant amounts of smoke. An additional problem in the Wiley et al. method is the requirement of a conveyor in the second stage to carry the first stage ground material over the second stage heaters. It is the latter conveyor which limits the length of heaters possible in the second stage without the second stage vehicle being excessively long. Thus, even though the first inch of asphalt is heated sufficiently, heating of the lower second inch by the second stage heaters is marginal.
U. S. Patent Number 4,850,740 issued on July 25, 1989 to Wiley discloses a method which allows the conveyor to be eliminated altogether and to use a longer bank of heaters in the second stage machine. Wiley '740 utilizes the heated windrowed material to heat a central unground lower layer of asphalt without the need for infra red heaters to heat that portion. Such heaters are only .
"`` 2~1~271 required for the side strips from which the milled asphalt is windrowed. Both Wiley'740 and the Canadian Patent issued to Wiley disclose removing one inch per stage for a total of two inches.
However, heating down to one inch requires either long heaters or relatively slow operation or both. Attempts to run the machines faster results in insufficient heating and a greater number of rock fractures which degrades the quality of the repaving.
Raising the temperature of the heaters causes burning of surface asphalt and results'~in the creation of unacceptably large amounts of smoke. There is at the present time considerable concern that such smoke is carcinogenic. There is, therefore, a need for a method and apparatus for repaving which produces substantially less smoke than known methods and machines and which can recondition down to at least two inches of depth while maintaining a speed of operation of twenty feet per minute or more.
Accordingly, it is an object of the invention to provide an improved method and apparatus for recycling and repaving asphaltic pavement. It is a further object of the invention to provide a method and apparatus for repaving asphaltic pavement which produces less smoke than known machines and, at the same time, is capable of operating as fast or faster than known methods and machines.
SUMMARY OF THE INVENTION
The present invention provides an asphaltic road surface repaving machine of a type that removes asphalt from the surface of the road, reconditions it and reapplies it to the road surface as the machine progresses along the road. The machine includes first means for heating a first layer of the road surface pavement such that the temperature of the top surface of the asphalt is maintained at less than 500 degrees F., means for rupturing asphalt in the first heated lay ~ and windrowing the ruptured heated ~ 3 ~. .. . . .
asphalt onto a selected strip of the road surface. Next an exposed portion or portions of the road surface are heated by radiant heat while that portion below the windrowed material is heated by conduction from the heated windrowed material. The heating, rupturing and windrowing steps are repeated at least twice more until at least two inches of road surface have been removed.
Finally the removed material is mixed together, distributed and pressed back onto the road surface.
By simply windrow~ng ground material from one stage onto a selected strip of the road surface being processed and using the heat from the windrow to conductively heat the underlying unground road surface rather than picking up the windrow in a conveyor and radiantly heating the whole road surface being processed, the need to incorporate a conveyor at each stage is avoided. Moreover, by multiplying the number of stages to at least three, it is possible to reduce the thickness of road surface layer heated, ruptured and windrowed in each stage and therefore to reduce the temperature to which the surface of the road is raised to less than 500 degrees F.
Preferably the method includes heating the entire road surface being processed until a preselected depth is softened, rupturing and windrowing the ground asphalt onto a center strip portion. Heating until softened and rupturing two side strip portions of the strip and moving the ground asphalt onto the center strip portion which separates the two side strip portions. The unground asphalt in the center strip portion is ground and the two side ~strip portions again heated to soften the asphalt therein.
The softened asphalt is again ground in the two side strip portions and moved onto the center strip portion. Finally the unground asphalt in the center strip portion is ground and left for further processing. The foregoing heating, rupturing and windrowing steps is repeated at least one more time until a depth of at least two inches has been removed from the road surface.
The further processing preferably includes mixing the ground asphalt in the center strip portion with rejuvenant, heating it, pulverizing it and then applying it to the pavement. Typically the time between moving ground asphalt onto thé center strip portion and grinding it together with underlying unground asphalt is 3 to 5 minutes.
BRIEF DESCRIPTION OF THE DRAWINGS
The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as other features and advantages thereof, will be best understood by reference to the detailed description which follows, read in conjunction with the accompanying drawings, wherein:
Figure 1 is a perspective view of a four stage process implementing a preferred embodiment of the invention;
Figure 2 is a plan view of a four stage apparatus for carrying out the method which shows banks of heating elements and grinders in relationship to the ve~i~les used to support them;
Figure 3 is a side elevation view of the equipment shown in Figure 2;
Figure 4 is a plan view identical to Figure 2 except for the~spacing between tbe h-aters which extends longitudinally; and Figure 5 is a side elevation view of the vehicles shown in Figure 4; and Figure 6 is a rear elevation view showing the grinders at the rear of the apparatus.
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DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS
Referring to Figure 1 there is shown in perspective a four stage embodiment of the invention for processing asphaltic pavement. In the Figure, the direction of travel is shown by the large arrow pointing generally to the bottom left hand corner.
First the entire road surface being processed, which is typically one lane of travel, is heated as shown at location 72 until the asphalt down to approximately 1/2 inches of depth is softened. The first 1/2 inch layer of asphalt is then milled or ground by grinders 36 and 37 immediately behind heated area 72 with grinders 36 simultaneously windrowing ground asphalt into the center as shown by the arrows. The grinders may rotate either against the direction of travel or with the direction of travel.
After milling or grinding by the central grinder 37, the two exposed side strip portions 74 and 76 are heated radia~tly down to approximately V2 inch while the center strip between is heated by windrow 77 of ground asphalt material. A second set of grinders 36 and 38 repeat the grinding processed as done by the first stage of grinders 36 and 37 and again windrow 79 heats the unground center strip while~side strips 91 and 93 are heated radiantly down to~approximatély 1/2 inch. The latter heating and milling steps are repeated twice more with windrows 81 and 84 again being used to heat unground center strips while side strips are heated radiantly down to 1/2 inch. Finally, rejuvenant and possibly virgin asphalt may be added if desired as shown by arrow 86 and the ground~asphalt and virgin asphalt, if any, mixed as shown by the arrows at 90 . The mixed material is then distributed evenly over the road by a screed 88 and then rolled.
Referring to Figures 2 and 3 there is shown in plan view a first stage self propelled vehicle 10 and a second stage self-propelled-vehicle 11 pivotally attached by pivotal joint 19 to the ? 2Q16271 first stage vehicle 10. Vehicle 10 consists of a platform 16 supported by wheels 18 and 20 at either end thereof. Heater banks 12, 13, 14 and 15 are each formed by rows 50 of propane fired elongated infra red heaters 54 are arranged in side by side relationship to extend across a strip of pavement to be heated.
Spaces 52 and 53 are located between the heater rows midway along a banks 12, 13, 14 and 15 although there are tunnels or gaps 21 and 23 extending longitudinal through the center of the banks 14 and 15 which intercept the spaces 52 and 56 of vehicle 11. Tunnels 21 and 23 overlap the central w~ndrow 77 and avoid heating the latter.
At either side of space 52 there are located 3 elongated radiant heaters 56 designed to compensate for the lower heating effect at the edges of the banks of heaters 54. Wheels 18 are coupled to the front of each vehicle 10 and 11 are remotely controlled through a micro processor unit (not shown) located at the rear of vehicle 11.
Thus, vehicle 10 and 11 are free to articulate about pivotal joint 19 so that the entire unit consisting of vehicles 10 and 11 may negotiate turns more easily.
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Vehicle 10 is made up of a frame or platform 25 supported by front wheels 24 and a rear pair of wheels 26. Rear wheels 26 and front wheels 24 can both be turned in response to remote control signals applied by an operator at the rear of vehicle 11.
The grinding units for both the first and second stage are located ;~ ~ on vehicle 11 with one set consisting of grinders 36 and 37 being i located at the front and the other consisting of grinders 36 and 38 being located at the rear of vehicle 11. Each of grinders 36, 37, 38, 39, and 41 are supported by means of a V brace member 32 supported at screw connections 30 from a front beam 31 affixed to the frame 22 of vehicles 10 or 11. Rear grinder units 37, 38, 39, and 41 overlap slightly the interior edges of side grinders 36.
At the back of grinders 36 and 38 there are vertically oriented blades 40 and 42 which extend down to the level of the cutting edges of grinders 36 and~38 and in operation exerts slight ',' '. ~ ', ~ ~', :
-.: . , .
pressure on the freshly ground pavement surface. As seen in Figure 6 there is an opening 37 in the center of plate 42 to permit windrowed ground material to pass therethrough.
The platforms 25 and 22 of vehicles 10 and 11 are each used to support a variety of different equipment required to operate the units such as a propane tanks 44, a container 46 to hold rejuvenant and pump unit 48. Banks of heaters 12 and 13 are suspended from platforms 16 and 19, respectively, while banks 14 and 15 are suspended from p~atforms 17 and 22, respectively.
A second unit as shown in Figures 4 and 5 consist of two self-propelled vehicles lOa and lla identical to those of vehicles 10 and 11 except for the front vehicle lOa having tunnels 43 and 45 extending longitudinally midway along the vehicle between the banks 12 and 13 of heaters. Again tunnels 43 and 45 accommodate windrows 81 and 84. Windrow 79 is accommodated by the space between the two units of articulating vehicles 10, ll and lOa, lla.
In operation vehicles 10 and 11 are followed closely behind by vehicles lOa and lla. A single operator operates vehicles 10 and 11 and another vehicles lOa and lla with both operators located at the rear of their respective units. The way in which these vehicles process and move the material has already been illustrated in Figure 1. It is to be understood that the areas~shown in Figure 1 are only a snapshot of an ongoing process whlch progresses forwardly as the vehicles move. The ground materiaI 84 is pulverized at step 90 by a pugmill mixer (not shown).~ The mix material can then be further processed either by levelling it out with a screed 88 and then compacting it or, by picking up the ground material and directing it to a bin in which the old material is heated, mixed and spread over the pavement surface by a repaving machine of conventional design (not shown).
The speed of the machines and spacing of the grinders 37, 38, 39 and 41 relative to the banks of heating elements is such that ground windrows 77, 79, 81 and 84 are left on the top of the surface of the center strip 77 where it is allowed to soak into the underlying unground material for a period of about one to one and one half minutes. This period has been found sufficient to soften approximately 1/2 inch to 5/8 inches of the unground underlying material sufficiently so that grinding of this material is facilitated. By only slightly increasing the depth of heating and grinding it is possible to remove an additional 1/8 inches of material in each stage leading to an increased depth of recycling of 1/2 inch in all.
By confining the windrow to as small a width as possible given the volume of material removed and applying a slight amount of pressure to it as it passes the hole in the central grinder back blade the heating effect on the unground center strip in each stage is maximized.
It has been found that using the four stage machine maximum surface temperatures of less than 500 degrees Fahrenheit are achieved with a corresponding substantial reduction in emissions.
Accordingly, while this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to this description. It is therefore contemplated that the appended claims will cover any such modifications or embodiments as fall with the true scope of the invention.
'`' ':: '. . ' ., ' ` , ~. . ', "`'' " ` ' ` '~ , ` ' ' .
Claims (16)
1. An asphaltic pavement pre-conditioning machine for use in conditioning old asphaltic pavement and reapplying it to a surface to be repaved, comprising:
(a) first radiant heating means for heating an upper layer of a strip of asphalt down to a depth of approximately to a more softened condition;
(b) first rupturing means for rupturing a first strip portion of said heated asphalt and moving ruptured asphalt to an adjacent unground heated second strip portion of said asphalt to form a row thereon exposing unheated asphalt in said first strip portion;
(c) second rupturing means for rupturing said unground heated strip portion and said moved material;
(d) second radiant heating means for heating the exposed unheated asphalt in said first strip portion behind said first rupturing means to a more softened condition;
(e) third rupturing means for grinding softened asphalt in said first strip portion and transporting it on to said second strip portion; and (f) fourth rupturing means for grinding both loose and softened asphalt in said second strip portion;
(g) third radiant heating means for heating the exposed asphalt in said first strip portion behind said third rupturing means to a softened condition;
(h) fifth rupturing means for rupturing heated asphalt in a first strip portion and moving it to an adjacent unground heated second strip portion to form a row thereon exposing unheated asphalt in said first strip portion;
(i) sixth rupturing means for rupturing asphalt in said unground heated second strip portion and said moved material:
wherein the total depth of asphalt removed is at least
(a) first radiant heating means for heating an upper layer of a strip of asphalt down to a depth of approximately to a more softened condition;
(b) first rupturing means for rupturing a first strip portion of said heated asphalt and moving ruptured asphalt to an adjacent unground heated second strip portion of said asphalt to form a row thereon exposing unheated asphalt in said first strip portion;
(c) second rupturing means for rupturing said unground heated strip portion and said moved material;
(d) second radiant heating means for heating the exposed unheated asphalt in said first strip portion behind said first rupturing means to a more softened condition;
(e) third rupturing means for grinding softened asphalt in said first strip portion and transporting it on to said second strip portion; and (f) fourth rupturing means for grinding both loose and softened asphalt in said second strip portion;
(g) third radiant heating means for heating the exposed asphalt in said first strip portion behind said third rupturing means to a softened condition;
(h) fifth rupturing means for rupturing heated asphalt in a first strip portion and moving it to an adjacent unground heated second strip portion to form a row thereon exposing unheated asphalt in said first strip portion;
(i) sixth rupturing means for rupturing asphalt in said unground heated second strip portion and said moved material:
wherein the total depth of asphalt removed is at least
2 inches and the spacing between said first, fourth, and sixth rupturing means is such that the heat from the ruptured material soaks down into the underlying unground asphalt to soften the latter prior to being ruptured by subsequent rupturing means.
2. An asphaltic pavement pre-conditioning machine for use in conditioning old asphaltic pavement and reapplying it to a surface to be repaved, comprising:
(a) first infra red heaters for heating an upper layer of an asphaltic road surface to a more softened condition;
(b) first grinding means for grinding an upper layer of said heated road surface and moving ground asphalt to an unground heated center strip portion of said road surface to form a row thereon exposing unheated asphalt in two side strip portions;
(c) second grinding means for grinding said unground heated center strip portion and said moved material;
(d) second infra red heater means for heating the exposed unheated asphalt in said side strip portions behind said first grinding means to a more softened condition;
(e) third grinding means for grinding softened asphalt in said side strip portions and transporting it on to said center strip portion; and (f) fourth grinding means for grinding both loose and softened asphalt in said center strip portion;
(g) third infra red heater means for heating the exposed asphalt in said side strip portions behind said third grinding means to a softened condition;
(b) fifth grinding means for grinding heated asphalt in said side strip portions and moving it to an adjacent unground heated center strip portion to form a row thereon exposing unheated asphalt in said side strip portions;
(c) sixth grinding means for grinding asphalt in said unground heated center strip portion and said moved material;
(d) fourth infra red heater means for heating the exposed unheated asphalt in said side strip portions behind said fifth grinding means to a more softened condition;
(e) seventh grinding means for grinding softened asphalt in said side strip portions and transporting it on to said center strip portion; and (f) eighth grinding means for grinding both loose and softened asphalt in said second strip portion;
wherein the total depth of asphalt ground is at least 2 inches and the spacing between said first, fourth, sixth and eighth grinding means is such that the heat from the ground material soaks down into the underlying unground asphalt to soften the latter prior to being ground by subsequent grinding means.
2. An asphaltic pavement pre-conditioning machine for use in conditioning old asphaltic pavement and reapplying it to a surface to be repaved, comprising:
(a) first infra red heaters for heating an upper layer of an asphaltic road surface to a more softened condition;
(b) first grinding means for grinding an upper layer of said heated road surface and moving ground asphalt to an unground heated center strip portion of said road surface to form a row thereon exposing unheated asphalt in two side strip portions;
(c) second grinding means for grinding said unground heated center strip portion and said moved material;
(d) second infra red heater means for heating the exposed unheated asphalt in said side strip portions behind said first grinding means to a more softened condition;
(e) third grinding means for grinding softened asphalt in said side strip portions and transporting it on to said center strip portion; and (f) fourth grinding means for grinding both loose and softened asphalt in said center strip portion;
(g) third infra red heater means for heating the exposed asphalt in said side strip portions behind said third grinding means to a softened condition;
(b) fifth grinding means for grinding heated asphalt in said side strip portions and moving it to an adjacent unground heated center strip portion to form a row thereon exposing unheated asphalt in said side strip portions;
(c) sixth grinding means for grinding asphalt in said unground heated center strip portion and said moved material;
(d) fourth infra red heater means for heating the exposed unheated asphalt in said side strip portions behind said fifth grinding means to a more softened condition;
(e) seventh grinding means for grinding softened asphalt in said side strip portions and transporting it on to said center strip portion; and (f) eighth grinding means for grinding both loose and softened asphalt in said second strip portion;
wherein the total depth of asphalt ground is at least 2 inches and the spacing between said first, fourth, sixth and eighth grinding means is such that the heat from the ground material soaks down into the underlying unground asphalt to soften the latter prior to being ground by subsequent grinding means.
3. A machine according to claim 2, wherein each of said grinders includes a rotating portion with a plurality of protuberances spaced over the surface thereof and a vertical blade immediately behind said rotating portion and supported by a common frame with said rotating portion, said vertical blade normally contacting the pavement.
4. A machine according to claim 2, wherein said fourth sixth and eighth grinding means have a vertical blade with an opening centrally thereof sufficient to permit escape of the ground material in a row along said center strip portion.
5. A machine according to claim 2, wherein said first infra red heating means includes a plurality of spaced apart banks of heaters, with each bank extending across the width of said strip and the space between banks being great enough to allow the surface temperature of asphalt heated by a previous bank to drop sufficiently so that it avoids overheating upon being heated by a next bank of heaters.
6. A machine according to claim 2, wherein said second, fourth, sixth and eighth grinding means overlaps with ends of said first, third, fifth and seventh grinding means so as to cover, together the width of said strip.
7. A machine according to claim 5, including heating sections on either end of the space between banks to compensate for the reduced heating effect at the end of said banks of heaters.
8. A method of reconditioning asphaltic pavement, comprising:
(a) heating a strip of asphaltic pavement until it is softened;
(b) grinding a first strip portion of softened asphalt of said strip;
(c) moving the ground asphalt to an adjacent unground strip portion of said strip;
(d) grinding both ground asphalt and unground asphalt of said adjacent strip portion;
(e) heating exposed unheated asphalt in said first strip until it is softened;
(f) grinding softened asphalt in said first strip portion and moving it onto said adjacent strip portion;
(g) grinding both previously ground and unground asphalt in said adjacent strip portion at a time after the second grinding step sufficiently long so that heat from said ground, previously heated asphalt soaks into underlying unground asphalt and softens it sufficiently to be ground;
(h) repeating steps (e), (f) and (g) as often as necessary until a predetermined depth of asphalt has been removed;
(i) mixing said ground asphalt with rejuvenant and reapplying it to the pavement.
(a) heating a strip of asphaltic pavement until it is softened;
(b) grinding a first strip portion of softened asphalt of said strip;
(c) moving the ground asphalt to an adjacent unground strip portion of said strip;
(d) grinding both ground asphalt and unground asphalt of said adjacent strip portion;
(e) heating exposed unheated asphalt in said first strip until it is softened;
(f) grinding softened asphalt in said first strip portion and moving it onto said adjacent strip portion;
(g) grinding both previously ground and unground asphalt in said adjacent strip portion at a time after the second grinding step sufficiently long so that heat from said ground, previously heated asphalt soaks into underlying unground asphalt and softens it sufficiently to be ground;
(h) repeating steps (e), (f) and (g) as often as necessary until a predetermined depth of asphalt has been removed;
(i) mixing said ground asphalt with rejuvenant and reapplying it to the pavement.
9. A method according to claim 8, wherein said heating steps include exposing a section of said asphaltic strip to successive spaced apart banks of infra red heaters until it becomes softened.
10. A method of preparing asphaltic pavement for repaving, comprising:
(a) heating a strip of asphaltic pavement until it is softened;
(b) grinding two side strip portions of said strip and moving the ground asphalt onto an underground center strip portion separating said side strip portions;
(c) grinding previously ground and unground asphalt of said center strip portion;
(d) heating asphalt in said side strips exposed by said grinding step until it is softened;
(e) grinding softened asphalt in said two side strip portions and moving it onto said center strip portion;
(f) grinding previously ground and unground asphalt in said center strip at a time after the second grinding step sufficiently long so that heat from said ground previously heated asphalt soaks into underlying unground asphalt and softens it sufficiently to be ground;
(g) repeating steps (d), (e) and (f) until at least approximately 2 inches of asphaltic road surface have been removed;
and (h) mixing and reapplying the ground asphalt to the road surface.
(a) heating a strip of asphaltic pavement until it is softened;
(b) grinding two side strip portions of said strip and moving the ground asphalt onto an underground center strip portion separating said side strip portions;
(c) grinding previously ground and unground asphalt of said center strip portion;
(d) heating asphalt in said side strips exposed by said grinding step until it is softened;
(e) grinding softened asphalt in said two side strip portions and moving it onto said center strip portion;
(f) grinding previously ground and unground asphalt in said center strip at a time after the second grinding step sufficiently long so that heat from said ground previously heated asphalt soaks into underlying unground asphalt and softens it sufficiently to be ground;
(g) repeating steps (d), (e) and (f) until at least approximately 2 inches of asphaltic road surface have been removed;
and (h) mixing and reapplying the ground asphalt to the road surface.
11. A method according to claim 10, further including mixing said ground asphalt in said center strip with a reconditioning agent, heating it, pulverizing and spreading and compacting it over said strip.
12. A method according to claim 10, wherein said grinding and moving steps are done simultaneously.
13. A method according to claim 10 wherein the time between moving ground asphalt onto the center strip portion and grinding it together with underlying unground asphalt is 1 to 1 1/2 minutes.
14. A method according to claim 10, wherein said heating steps include providing a heat soaking in period between applications of radiant heating so that the asphalt surface does not overheat.
15. A method according to claim 10, including heating end sections of said strip between said heating step to compensate for reduced heating effect at the ends.
16
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2016271 CA2016271A1 (en) | 1990-05-08 | 1990-05-08 | Method and apparatus for repaving asphaltic pavement |
| AU77797/91A AU7779791A (en) | 1990-05-08 | 1991-05-08 | Method and apparatus for repaving asphaltic pavement |
| PCT/CA1991/000157 WO1991017315A1 (en) | 1990-05-08 | 1991-05-08 | Method and apparatus for repaving asphaltic pavement |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2016271 CA2016271A1 (en) | 1990-05-08 | 1990-05-08 | Method and apparatus for repaving asphaltic pavement |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2016271A1 true CA2016271A1 (en) | 1991-11-06 |
Family
ID=4144939
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2016271 Abandoned CA2016271A1 (en) | 1990-05-08 | 1990-05-08 | Method and apparatus for repaving asphaltic pavement |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AU7779791A (en) |
| CA (1) | CA2016271A1 (en) |
| WO (1) | WO1991017315A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8056549B1 (en) | 2011-03-04 | 2011-11-15 | Husqvarna Construction Products North America Inc. | Concrete pavement texturing head |
| CN102912709B (en) * | 2012-10-26 | 2015-05-27 | 长安大学 | Construction coating device and construction process for heat reflection type asphalt pavement coating |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4545700A (en) * | 1982-09-24 | 1985-10-08 | Yates Larry A | Process for recycling bituminous asphalt pavement |
| US4850740A (en) * | 1988-06-02 | 1989-07-25 | Wiley Patrick C | Method and apparatus for preparing asphaltic pavement for repaving |
-
1990
- 1990-05-08 CA CA 2016271 patent/CA2016271A1/en not_active Abandoned
-
1991
- 1991-05-08 AU AU77797/91A patent/AU7779791A/en not_active Abandoned
- 1991-05-08 WO PCT/CA1991/000157 patent/WO1991017315A1/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| WO1991017315A1 (en) | 1991-11-14 |
| AU7779791A (en) | 1991-11-27 |
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