US3448526A - Apparatus for and method of drying ink and other materials on a carrier - Google Patents

Description

June 10, 1969 H. L. SMITH, JR

APPARATUS FOR AND METHOD OF DRYING INK AND OTHER Sheet MATERIALS ON A CARRIER Filed July 20, 1967 21 mm 13 8 w? @m QNM 8 ll lll llrllll4 mvnww MMH I I I l w A! u t on I $9 E R &= 6m E w.w\ F E ow d mm mm INVENTOR Horace L. Smi/h, Jr MW/M 7% W ATTORNEYS June 10, 1969 H. L. SMITH, JR 3,448,526

APPARATUS FOR AND METHOD OF DRYING INK AND OTHER MATERIALS ON A CARRIER 2 Filed July 20, 1967 Sheet of 5 Horace L. Sm/fh, Jr

b 3M4 /mww ATTORNEY June 10, 1969 H. L. SMITH, JR 3,448,526

APPARATUS FOR AND METHOD OF DRYING INK AND OTHER MATERIALS ON A CARRIER Filed July 20, 1967 Sheet 3 of s INVENIOR Horace L. Sm/l/z, Jx:

ATTORNEYS United States Patent 3,448,526 APPARATUS FOR AND METHOD OF DRYING INK AND OTHER MATERIALS ON A CARRIER Horace L. Smith, Jr., 301 Lock Lane, Richmond, Va. Filed July 20, 1967, Ser. No. 654,838 Int. Cl. F2611 3/28 US. Cl. 34-4 16 Claims ABSTRACT OF THE DISCLOSURE Drying apparatus including a support for a carrier having at least one material to be dried thereon; one 7 or more radiant heating units disposed adjacent said support for evolving at least one volatile substance from the material to be dried; and an arrangement associated with each radiant heater for directing a fluid at high velocity against the carrier to prevent it from being overheated and to increase the rate of drying. Methods of drying materials on carriers by a combination of radiant heat and fluid impingement.

BACKGROUND, SUMMARY, AND OBJECTS OF THE INVENTION 3,448,526 Patented June 10, 1969 printed or coated areas may be heated at relatively high rates to evaporate the volatile materials rapidly. Yet, at the same time, the application of heat to the uncoated portions of the carriers may in many applications be limited to a sufliciently low rate to prevent substantial heat damage to the carriers.

While the techniques disclosed in the foregoing patent are satisfactory in many instances, it has been found that there are applications in which the materials involved cannot be satisfactorily dried at a practical rate by'such techniques without damaging the carrier. Such applications include, for example, the drying of inks on paper or other carriers which are comparatively heat sensitive. In such cases there may not be a sufficiently different absorption rate between the carrier and the material being dried'to completely dry the ink without scorching the carrier.

An attendant disadvantage of my earlier disclosed technique in many applications is that drying rates, while improved, are still not capable of matching the speed of modern high-speed presses except by extending the dryer to a length which is not compatible with the limited to limit the scope of the invention as defined in the appended claims.

In recent years developments in high speed presses and printing techniques have outstripped developments in the drying art to the point that present day drying equipment is not capable of operating with suflicient speed to prevent smearing or smudging when the presses are operated at full speed. As a result, modern high speed presses are usually operated at speeds well below their design limits, thus substantially reducing production rates and keeping printing costs high. Many devices have been proposed and used to accelerate the drying of ink and other materials printed on and impregnated in paper, textiles, and other carriers. For example, it has been proposed to pass the carriers over open gas flames, to blow hot air across the printed areas, and to employ steam heated radiators, electric strip heaters and gas burning infrared heaters for this purpose. At best, such methods only partially solve the problem. All fail to provide drying speeds commensurate with the printing capabilities of modern printing equipment and in general require cumbersome, bulky, and expensive equipment.

To overcome the foregoing and other disadvantages of available drying techniques, I invented and disclosed in my US. Patent No. 3,237,314 issued Mar. 1, 1966, novel apparatus and methods utilizing as a heat source short wave length radiant energy which is absorbed at different rates by inks (or other printing materials) and the materials of which the carriers are fabricated. By employing radiant energy of the proper wave length, the

As used herein reference to materials on a carrier is in tended to embrace both the case of materials deposited on the surface of a carrier and that of materials impregnated in the carrier. Furthermore the term material is sometimes used genergically to cover mixtures of substances which are to be tlrie space available in press rooms and similar confined areas.

Yet another disadvantage of the drying technique described above is that the wavelength of the radiant energy employed must be closely regulated since the success of the method in part depends on the ditferences in absorptivity of the carrier and the material on it for radiant energy of specific wavelengths. Since the intensity of the radiant output must on the other hand be varied as the velocity of the carrier through the dryer changes to keep the application of energy uniform, a relatively complicated control system for the radiant heaters is required.

I have now invented an improved technique for drying applications of the type described above. This process employs radiant energy to evolve volatile substances from the materials to be dried as in my earlier disclosed technique. However, I have now discovered that by directing a heated fluid such as air at high velocity against the carrier as it moves through the radiant heating zone the temperature of the carrier can be maintained sufliciently low to prevent it from being overheated for a much longer period of time than is the case when radiation alone is employed. This technique has been found to work well even in the most diflicult circumstances such as where a fast drying, highly absorptive ink and a slow drying ink are dried on the same carrier.

At the same time that it is aflording protection against overheating the impinging fluid scours evolved volatiles from adjacent the carrier. This increases the efliciency with which energy is transferred from the radiant energy source to the material being dried and, accordingly, the drying rate. For example, impingement at moderate rates is capable of doubling the drying rates attainable by even high intensity radiation alone.

Furthermore, the ease with which the temperature of the carrier may be controlled makes the differential between the absorptivities of the carrier and'the material being dried thereon considerably less important than when radiation alone is employed. Accordingly, the comparatively complicated radiant heater control system described in my earlier patent need not be employed when drying materials by the techniques described herein. Consequently, the apparatus of the present invention is less expensive to construct and maintain than that I disclosed earlier.

The specific areas of the carrier protected by the impinglng fluid are those on which there is no undried material. Those areas on which there is undried material will not exceed the boiling point temperature of the solvent (or solvents) in the material until the solvent or solvents have been substantially completely evaporated. The most critical areas are those on which black and other dark colored inks andother similar materials have been dried because of the high absorptivity in such areas.

The general concept of employing radiant energy in combination with impinging fluid to dry materials of the ---typejde'scribedabove is itself knownas shown'by U.S.

ate nt s Nos. 3,141,089, 3,257,542, and 3,254,422, fonex- 1 ample. However, it has not heretofore been known that -byemploying the fluid in the manner described above in more detailhereinafter, the fluid can be utilized to cool the carrier and thereby extend its scorch limit? QNOI has it been recognized that, by utilizing the fluid in r thisj manner, drying rates can at the same time be substantially increased andthe necessity of closely regulating-the wavelength of the radiant energy by which the, materials being dried are heated virtually eliminated. Furthermore, the, dryers shown in the foregoing patents would not be capable of applying radiant energy and impinging fluid in the specific relationship contemplated -by..the-presen t invention. Accordingly, drying by acornbination. of radiant energy and impinging fluid in the '.specific manner described herein not only differs materially rom, but represents a considerableimprovement over, he heretoforeknown techniques of using a combination ef radiant energy and heated fluid.

: From the.foregoing it will be apparent portant-and primary object of the present invention isthe provision of novel, improved methods of and apparatus for drying materials containing volatile constituents on i sheet, web, and similar carriers.

Other important but more specific objects of the present invention reside in the provision of drying methods and apparatus in accord with the preceding object:

(1) in which drying is accomplished by a combination of radiant energy and heated, high velocity impinging fluid.

(2) in which, in conjunction with the Preceding object,

- the temperature, velocity, and volume of the fluid impinging on the carrier are so regulated as to limit the FIGURE 3 is a longitudinal section through the installation of FIGURE 1;

FIGURE 4 is a view similar to FIGURE 2, but to an enlarged scale;

' FIGURE 5 is a section through the installation, taken substantially along line 5-5 of FIGURE 3;

FIGURE 6 is a longitudinal section through a second form of installation in accord with the principles of the present invention; and

FIGURE 7 is a section through an air bearing utilized in the embodiment of FIGURE 6.

DETAILED DESCRIPTION OF EXEMPLARY PREFERRED EMBODIMENTS As discussed above the present invention resides, in

' one aspect, in the provision of novel methods for drying materials containing volatile constituents on sheet, web, j and similar carriers by a combination of radiant energy that an imand heated fluid. One important application of this techvthe slow drying ink (or inks) is still wet and, furthermore, will absorb the radiant energy at a high rate.

. Therefore, the carrier will begin to scorch in these areas before the slow drying ink is dry if the carrier is dried in accord with the heretofore known techniques and' simultaneously and when they are dried successively.

:temperature rise of the carrier and thereby extend its 7 scorch limit.

' ('3) in which, in conjunction with the preceding object, the temperature, velocity, volume, and other factors relating to the impingement of the heated fluid on the carrier are so controlled as to materially increase the drying rates over those heretofore obtainable by using a combination a of radiation and fluid impingement.

(4) in which precise control of the wavelengths of the radiant energy employed is unnecessary.

(5 which are capable of drying combinations of materials that cannot satisfactorily be dried by previously known techniques employing a combination of radiant energy and'impinging fluid.

(6 which can be utilized for applications in which there are materials to be dried on both sides of the carrier. (7) in which the carrier is simultaneously contacted with radiant energy and heated fluid.

Other important objects, further novel features, and other significant advantages of the present invention will become fully apparent from the appended claims and as the ensuing detailed description and discussion proceeds in conjunction with the accompanying drawing.

f BRIEF DESCRIPTION OF THE DRAWING In the drawing: 'FIGURE 1 is a side view of an installation equipped with drying apparatus embodying the principles of the 3 By scorch limit is meant the period for which a carrier can be subjected to radiant energy of a given wavelength and intensity without scorching. From this definition it will be apparent that the scorch limit of a carrier will be different in .a'reas on which there is no material to be dried and in areas on which there is dried material because of the different ahsorptlvitles in these areas. Also, if there are two .or more dried materials on the carrier, the scorch limits in the respective areas may ditfer because of the different absorptivities of the dried materials.

1 heat sensitive. In this case it may not be possible to subject the carrier to radiant energy of the intensity required to dry the ink at a commercially practical rate without causing the carrier to become scorched before the ink is dry.

'I have discovered that the rate of temperature increase in the carrier can be substantially decreased and the scorch limit of the carrier correspondingly increased by directing a heated fluid at high velocity against the carrier subjected to radiant energy to dry the material or materials thereon.

To effectively perform this function without otherwise adversely effecting the drying process or increasing power requirements to an impractical level the fluid (typically air) must be heated to a temperature in the range of I against the carrier or may be directed against the carrier at an angle which deviates slightly from the normal in the direction of movement of the web or in the opposite direction. This will give the fluid a small velocity component along the web which will tend to sweep fluid already impinged on the carrier and its burden of evolved volatiles into exhausts ducts or plenums extending across and spaced along the path of the carrier.

A further and extremely important requiremenfis that the impinging air be directed against the carrier as the latter travels through the radiant energy zone as contrasted to being employed after the carrier is subjected to the radiant energy (i.e., concurrently with as opposed subsequent to the application of the radiant energy). This has been found to produce greatly increased performance as shown by the following example in which yellow and black inks were dried on coated paper.

(I) Subsequent jet impingementc0nfiguration #1 (A) In this test, the carrier was passed through a radi- (11) Subsequent jet impingement-configuration #2 (A) In this test the carrier was passed through a radiant section of six lamps before application of impinging air. Air was applied concurrently with radiation from six additional lamps.

(B) Operating conditions-12 lamps as above. Flux density as above.

(C) Dryer performance-Black ink was dried in 0.44 sec.; yellow ink was dried in 1.30 sec.; scorch occurred beneath the black ink in 1.22 sec.

(III) Concurrent jet impingement (A) In this test, radiant energy and impinging air were applied concurrently to the carrier.

,(B) Operating conditions-12 lamps as above; flux density as above; nozzles as above. The impinging air was distributed over the entire radiant section.

(C) Dryer performance-Black ink was dried in 0.32 sec.; yellow ink was dried in 0.95 sec.; scorch occurred beneath the black ink in 1.29 see.

As shown by the foregoing, the application of impinging air concurrently with radiant energy reduces on the order of 50% the drying time required when the im pinging air is applied subsequent to the radiant energy. At the same time, in contrast to the use of subsequent impinging air as in test II where scorching occurred before the yellow ink dried, a comfortable safety margin is obtained even in the difiicult task of drying both black and yellow ink on the same carrier. Specifically, as shown by test HI, the scorch limit of the area of the carrier covered by black ink and therefore most prone to heat damage will typically still exceed the time required to dry yellow ink (which is the slowest to dry) by a considerable margin.

In another test operating conditions similar to those in test 111 above were employed except that a lower flux density was used, and red and black inks were simultaneou sly dried. Both inks dried in 2.08 seconds, and the coated paper on which the inks were printed Went 3.50 seconds without scorching.

The test was then repeated with the black being applied to the paper and dried and the red ink subsequently being applied so that it partially overlapped the dry black ink and then dried. The black ink dried in 1.41 seconds and the red ink in 2.43 seconds while the paper was undamaged.

This series of tests demonstrate the capability of the present invention for handling extraordinarily difiicult drying assignments. Specifically, in those tests the highly absorptive black ink was subjected to the infrared radiation for the entire period in which the slow drying red ink was dried. Yet there was no scorching of the paper to which the inks were applied.

To further demonstrate the increases in drying rates produced by the present invention the tests just described were followed by one in which the red and black inks were dried separately with impinging air by itself. Both inks required approximately 35 seconds to dry, demon- Percent O.A. is the percentage of the total cross sec tlonal area of the nozzles supplying the impinging fluid to the carrier based on the area of the radiant energy zone prO ected on the carrier.

strating that heated impinging air alone, like radiant energy alone, is considerably inferior to the balanced combination of radiant energy and heated fluid contemplated by the present invention.

As indicated above it is important that the impinging air be distributed over the entire radiant heating zone. The percent O.A. factor is also of considerable importance. For the optimum extension of scorch limit consistent with otherwise satisfactory drying and economically practical power requirements the percent O.A. should be in the range of approximately 1-5% and preferably in the range of 2-2%%.

To further demonstrate the synergistic effects of radiant energy and concurrent impinging air in accord with the present invention tests were conducted using radiant energy alone. In one such test the radiant energy source was 12 T-3 quartz tube lamps operating at 230 v. and located 3% inches centerline to carrier as in the tests described above. Under these conditions black ink dried in 0.46 second and yellow ink in 1.42 seconds. Scorch occurred beneath the black ink in 0.96 second.

A comparison of the results obtained in the preceding test with those obtained in test III above in which radiant energy was employed in combination with concurrent impinging air in accord with the present invention shows that the latter produces substantially higher drying rates for slow drying and fast drying inks than radiant energy alone. In addition, a material longer scorch limit is obtained by this novel combination of drying media.

The following table shows typical times for drying a variety of inks of different types in accord with the present invention. In such tests the carrier was coated publica tion paper, the radiant energy was supplied by twelve T-3 lamps, and the impinging fluid was air heated to 210 F. and delivered at a velocity of 4500 f.p.m. through nozzles having 1.41% O.A.

Identification code Drying time (sec.)

Light blue B1 Referring now to the drawing, FIGURES 1-3 depict a typical printing installation 20 equipped with a dryer 22 in accord with the principles of the present invention for drying ink on a web-type carrier 24 in the manner described above.

In addition to drying unit 22, installation 20 includes a stand 25 from which carrier 24 is guided over a roll 26 to a printing station 27 including a plate cylinder 28, a blanket cylinder 30, and an impression cylinder 32, all of conventional construction, which transfer the ink to carrier 24 in the-desired pattern. From the printing station, the inked web 24 travels across rollers 36 past the dryer and then around chill rolls 38, which cool the dried web, to a rewind stand 40 or other processing station.

The unit 22 for drying the printed web includes one or more radiant heating-fluid impingement units 42 (two such units are shown in the embodiment of the invention illustrated in FIGURES 1-3, but this number may of course be varied as desired), a cooling section 44, a fluid handling system 46 for supplying fluid to and exhausting it from units 42, and a second fluid handling system 48 for supplying fluid to the cooling section 44.

Each of the novel radiant heating-fluid impingement units 42 in dryer 22 includes an open-bottomed casing 50 having end walls 52, side walls 54, and a top wall 56. Housed in casing 50 are a plurality (seven in the illustrated embodiment) of tungsten filament, quartz envelope lamps 58, which are disposed in parallel, spaced apart relationship with their centerlines in a plane parallel to the path of web 24 and extending transversely across and spanning the web. Typically, the distance between the web and the centerlines of the lamps will be 3% inches although this distance may be varied as desired for particular applications of the invention.

Lamps 58 may be the T-3 model produced by General Electric Company, which is designed to operate at temperatures ranging from about 2000 F. to 5000 F. to produce radiant energy having a wavelength ranging from 2.0 microns to 0.3 micron. Such lamps may be operated at higher and lower temperatures, if desired, to produce radiant energy of other wavelengths and may be replaced by other radiant energy sources if desired since the specific type of energy source is not critical in the practice of the present invention.

Lamps 58 may be mounted in casing 50 in any desired fashion. For example, as shown in FIGURE 5, they may be supported from bus bars 60 which, in turn, are mounted on horizontally extending sheet metal supports 62 fastened between the side walls 54 of casing 50 and side reflectors 64 disposed in parallel, spaced relationship to the side walls. Bus bars '60 are also connected to a source of operating voltage (not shown) for the lamps.

To prevent dissipation of the radiant energy emitted by lamps 58 and to concentrate the energy emitted from them uniformly on the carrier below casing 50, the side reflectors 64 just mentioned are employed together with end reflectors 66 and a top reflector 68 disposed below and in parallel, spaced relationship to the top wall 56 of casing 50. The end and side reflectors will typically be gold plated and the top reflector fabricated of polished aluminum although reflectors of other materials may be employed, if desired.

To protect the ends of lamps 58 against damage, horizontal flanges 70 integral with casing side walls 54 are extended from the latter to side reflectors 64. Slots 72 in the side reflectors, through which the lamps extend, and cooperating slots 74 in flanges 70 to permit air to flow around the end terminals of the lamps. This prevents them from overheating and shorting out.

Referring now specifically to FIGURES 3 and 5, the interior of casing 50 provides a supply plenum 76 for the heated air or other fluid which is directed against web 24 as it moves through the zone of radiant energy generally coextensive with the open bottom end of casing 50. The heated fluid is directed from the supply plenum against web 24 by nozzles 78. As best shown in FIGURE 4, there is a row of nozzles between each pair of radiant heating elements 58 and a total of five nozzles in each row (the (L/D) of 3-4; and, as discussed above, the total cross sectional area of the nozzles will typically be in the range of approximately 1 to approximately 5 percent of the area of the zone of radiation projected on web 24.

As best shown in FIGURE 3, nozzles 78 may be fastened to and extend through top reflector 68. Three of the six rows of nozzles are inclined at an angle from the normal to web 24 in its direction of travel and the remaining three rows at a similar angle in the opposite direction. As explained above, this is to give the fluid exiting from the nozzles a velocity component such that it will aid in sweeping fluid into exhaust plenums 80 spanning web 24 on opposite sides of the radiant heating zone. This orientation is not critical, however; and the nozzles may be oriented normal to web 24, if desired.

As mentioned above, the impinging fluid will typically be heated air. In such a case, the air may be supplied to the supply plenums 76 of the radiant heating-fluid impingement units by a blower 82 connected through a duct 84 to a heater 86. The heater may, in turn, be connected to each radiant heating-fluid impingement unit 42 by ductwork identified generally by reference character 88 and communicating with the associated supply plenum 76 through an opening 90 in the top casing wall 56 of the associated radiant heating-fluid impingement unit.

As the fluid passes from ductwork 88 through plenum 76 and into nozzles 78, it flows in heat transfer relationship to the top reflector 68 of the unit. This serves two useful functions. First, the air or other fluid will generally be at a substantially lower temperature than the reflector and will accordingly cool the latter to prevent it from becoming overheated. At the same time, the fluid will pick up otherwise wasted heat from the reflector, reducing the heat which must be supplied by heater 86 or even altogether eliminating the need for the separate heater.

As discussed above, the heated fluid exiting from nozzles 78 and impinging on web 24 protects the latter against overheating and also scours from adjacent its surface the constituents evolved from the ink or other material being dried on carrier 24 by the radiant energy from lamps 58. 5

The reasons why the scouring effect of the impinging fluid are of such importance are discussed in detail in my earlier Patent No. 3,318,017 issued May 9, 1967.

Briefly, however, evolved volatiles form a boundary layer adjacent the surface of the carrier being dried. This stagnant layer impedes the transfer of energy from the radiant energy source to the material on the carrier. The high velocity impinging air, by securing away this layer, materially increases the efliciency with which energy is transferred from the radiant source to the material to be dried.

From the vicinity of web 24, the impinged treating fluid and its burden of evolved volatiles flows through inlet openings 91 into the exhaust plenums 80 mentioned above. These extend transversely across and span web 24 and are defined by a sheet metal casing identified generally by reference character 92, the details of which are unimportant in the practice of the present invention.

To conserve the sensible heat in the impinging fluid, the spent fluid and evolved volatiles are preferably recirculated through exhaust ductwork identified generally by reference character 94 to the inlet of blower 82. In many applications of the present invention, the percentage of volatiles in the impinging fluid must be closely controlled to prevent the formation of undesired characteristics in the product being dried. To permit such control, ductwork 94 is provided with a make-up duct 96; and a 'lhe heated fluid may also contribute to the evolution or evaporation of solvents from the materials being dried. However, as yet, there appears to be no practical way to measure the extent to which the heated fluid does contribute to such evaporation or evolution.

9 vent duct 98 is located in the duct 84 between blower 82 and heater 86. Valves 100 and 102 control the flow through make-up and vent ducts 96 and 98, respectively.

By adjusting valve v100 and 102, spent recirculated fluid can be discharged from the system and replaced with treating fluid having a lower content of volatiles to maintain the volatile content at the desired level. Valves 100 and 102 may be adjusted manually or, if desired, may be automatically regulated by a control system of the type disclosed in my U.S. Patent No. 3,208,158 issued Sept. 28, 1965.

If air is employed as the treating fluid, make-up duct 96 may be left open to the ambient atmosphere and vent duct 98 connected to a suitable stack or other vent system. In the event that another fluid is employed, make-up duct 96 will instead be connected to an appropriate source of this fluid.

As indicated previously, the dried web 24 moves from the last radiant heating'fluid impingement unit 42 past a cooling section 44 (see FIGURE 3). Cooling section 44, together with chili rolls 38, reduces the temperature of the dried web to approximately ambient temperatures before it is rewound (depending upon the type of ink employed, cooling of the dried web may be unnecessary or it may not be necessary to reduce the web temperature to ambient temperature).

The details of cooling section 44 are not critical and may be varied depending upon the application involved. One suitable type of cooling section, shown best in FIG- URE 3, includes a sheet metal casing 104 providing a plenum chamber 106 which spans web 24. Mounted in and spanning the open lower end of casing 104 and disposed in spaced, parallel relationship to the web is a plate 108 in which nozzles 110 are formed. This type of nozzle plate is described in detail in my copending application No. 615,966, filed Feb. 14, 1967 (now Patent No. 3,403,- 456), to which reference may be made if deemed necessary for a more complete understanding of the present invention.

.As shown in FIGURE 3, nozzles 110 are preferably inclined from the normal to web 24 in a direction opposite that to which the web moves through dryer 22. This increases the scouring eifect of the coolant on the web, which increases the'heat transfer rate from the web to the coolant, and also promotes the flow of the coolant into an exhaust plenum 112 disposed adjacent housing 104.

Air may also conveniently be employed to cool the dried web although other coolants may be employed, if desired. The air or other coolant may be supplied to plenum 106 by a blower 114 connected to a supply duct 116 which communicates with the plenum through an opening 118 in the top wall 120 of cooling section casing 104. If air is employed as a cooling fluid, the inlet of blower 114 may be connected to the ambient atmosphere or to a source of cooled air. If another coolant is employed, the blower inlet will be of course connected to an appropriate source of such coolant.

The exhaust plenum 112 into which the coolant flows after contacting web 24 may be connected through appropriate ducting 121 to the inlet of the blower 82 in the fluid circulation system for the radiant heating-fluid impingement units. This conserves the sensible heat in the cooling fluid, which would otherwise be wasted.

The embodiment of the invention described above is intended for applications where there is material to be dried on only one side of the carrier. The principles of the present invention are, however, equally adaptable to applications where there are such materials on both sides of the carrier. This occurs, for example, in the blanket-toblanket or perfecting method of printing in which both sides of the paper are simultaneously printed.

For drying carriers of the type just described, a dryer 122 of the type illustrated in FIGURE 6 may be employed.

Referring now to the latter figure, drying system 122 includes a first dryer 124 disposed above the path of a web 24 and a second dryer 125 disposed below this path and facing dryer 124. As shown in FIGURE 6, drying unit 124 may be identical to the dryer 22 described above. Drying unit 125 may also be identical to dryer 22 except for the addition of air bearings 126, which support web 24' as it moves through drying system 122. 6 To the extent that the components of dryers 124 and 125 are like those of dryer 22, they have accordingly been identified by the same reference characters primed.

Air bearings 126 may be of any desired construction but, as shown in FIGURE 7, will typically consist of an elongated casing 128 defining a plenum chamber 130 extending transversely of and spanning web 24' and supported in any desired fashion from other components of the drying system. Apentures 132 (two rows of such apertures are shown in FIGURE 7, but this number may be varied as desired for particular applications of the invention) are formed at equally spaced intervals (only one aperture in each row is shown) in the top wall 134 of casing 128. A blower (not shown) forces air at low pressure into plenum 130 and through nozzles 132, where the air forms a thin film spacing web 24' from the top wall 134 of the air bearing.

Nozzles 132 will preferably but not necessarily be of the construction described in my earlier Patent No. 3,- 313,462 issued Apr. 11, 1967, because of the advantages such perforations possess over straight-sided and other apertures in air bearing applications.

The operation of drying system 122 is identical to the operation of the dryer 22 described above except that, as mentioned earlier, web 24' is supported on a film of air as it moves through the system to prevent the material on its lower side from being transferred to the Web supports. a

From the foregoing, it will also be obvious to those skilled in the arts to which the present invention pertains that many other modifications may be made in the illustrated embodiments of the invention. For example, the radiant heating-fluid impingement units may be oriented vertically or at any angle between the horizontal and vertical or may be configured to fit around the periphery of an offset letterpress impression cylinder between the multiple printing stations positioned at intervals around such a press. It will also be obvious that many modifications may be made in the structural components of the exemplary embodiments described above in applying the principles of the present invention. Accordingly, to the extent that such modifications are not expressly excluded from the appended claims, they are fully intended to be covered therein.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

1. The method of drying materials on sheet, web, and similar carriers which are apt to suffer heat damage before the materials thereon are dry, comprising the step of moving the carrier through a zone of radiant energy and projecting radiant energy onto the carrier as it moves through said zone to evolve volatiles from the material to be dried at a rate such that the material on the carrier will be dry before the carrier exits from the 6 If rollers or similar supports of the type employed in the installation of FIGURES 13 were utilized in drying system 122, the wet material on the bottom side of web 24 would transfer to the rollers as it contacted them. This would be highly undesirable for obvious reasons. Air bearings 126, in contrast, support Web 24' on a thin film of air as it passes over them, thereby preventing offsetting of the material on the bottom side of the web.

radiant energy zone, said radiant energy being provided from an electrically operated source at a temperature such that the radiant energy has its peak at a wavelength in the range of about 2 to about 0.3 microns, and the step of both limiting the increase in the temperature of the carrier to an extent suflicient to permit the retention of the carrier in the radiant heating zone until the material thereon is substantially dry without damage to the carrier and increasing the rate of drying of the material thereon by directing a fluid heated to a temperature in the range of about 200 to about 300 F. at a high velocity in the range of about 4000 to about 9000 feet per minute into contact with the portion of the carrier against which the radiant energy is projected, said impinging fluid thereby preventing overheating of the carrier by limiting the temperature of those areas of the carrier which do not have undried material thereon and simultaneously removing evolved volatiles from adjacent said carrier to increase the rate of evolution of volatiles from the material being dried.

2. The method of claim 1, together with the step of cooling the carrier after the materials thereon have been dried by effecting a flow of unheated air into contact with said carrier.

3. The method of claim 1, together with the step of utilizing energy from the source furnishing the radiant energy projected against the carrier to heat the fluid directed thereagainst.

4. The method of claim 1, wherein there are materials to be dried on both sides of the carrier and wherein both sides of said carrier are concurrently radiantly heated and contacted with heated fluid to thereby simultaneously dry the material on both sides of the carrier, said method further including the step of supporting said carrier on an air cushion while the material thereon is being dried to prevent dislodgement of the undried material on the carrier.

5. The method of claim 1, together with the step of recirculating the heated fluid directed against and then removed from adjacent the carrier to conserve the sensible heat in said fluid.

6. The method of claim 1, together with the step of directing the heated fluid against the carrier at an angle from the normal and toward the location at which the impinged fluid is exhausted from adjacent the carrier to facilitate the removal of said fluid and evolved volatiles from adjacent said carrier.

7. The method of claim 1, wherein the portion of the carrier against which the heated fluid is directed is substantially coextensive with the portion of the carrier against which the radiant energy is directed.

8. The method of claim 1, wherein the heated fluid is directed onto the carrier in a series of jets located in a predetermined pattern substantially spanning the zone of radiant energy and wherein the total cross sectional area of the jets is in the range of about 1 to about 5% of the area of the carrier against which the radiant energy is projected.

9. Apparatus for drying materials on sheet, web, and similar carriers which are apt to suffer heat damage before the materials thereon are dry comprising a first, electrically operated radiant heating means for forming a. zone of radiant energy traversable by said carrier and means for moving the carrier in a path through said zone of radiant energy to evolve volatiles from the material to be dried at a rate such that the carrier is dry before the carrier leaves the radiant heating means, said radiant heating means including electrical heating elements extending transversely across said path, a casing, and means on opposite sides of said path supporting said heating elements from said casing in spaced relation to said path; means for limiting the increase in the temperature of the carrier to an extent suflicient to permit the retention of the carrier in the radiant energy zone until the material thereon is substantially dry without damage to the carrier and for increasing the rate at which the material on the carrier is dried, said last-named means including a second means for heating a fluid and means for directing said heated fluid at a high velocity into contact with the carrier to prevent overheating of the carrier by limiting the temperature of the areas of the carrier which do not have undried material thereon and to remove evolved volatiles from adjacent said carrier to increase the rate of the evolution of volatiles from adjacent the materials being dried, the means for directing said heated fluid against said carrier comprising means including said casing providing a suppl plenum on the side of the radiant heating means opposite the path of the carrier through the radiant heating zone, whereby said radiant heating means is disposed between said supply plenum and said path, means between said heating elements providing fluid communication between the supply plenum and the carrier, and a fluid circulator means for eflfecting a flow of said heated fluid into said supply plenum and from said fluid supply plenum through said fluid communication providing means into contact with the carrier, said first radiant heating means and said second fluid heating means being separate and independently operable, whereby said radiant heating means can be operated at a temperature substantially diiferent than that of said fluid heating means; and means for exhausting the heated fluid and evolved volatiles from adjacent said carrier.

10. Apparatus for drying materials on sheet, web, and similar carriers which are apt to suffer heat damage before the materials thereon are dry comprising a first, electrically operated radiant heating means for forming a Zone of radiant energy traversable by said carrier, said radiant heating means comprising at least one heating element and a reflector adjacent said element; means for moving the carrier through said zone of radiant energy to evolve volatiles from the material to be dried at a rate such that the carrier is dry before the carrier leaves the radiant heating means; and means for limiting the increase in the temperature of the carrier to an extent suflicient to permit the retention of the carrier in the radiant energy zone until the material thereon is substantially dry without damage to the carrier and for increasing the rate at which the material on the carrier is dried, said last-named means including a second, fluid heating means for heating a fluid to a temperature in the range of about 200 to about 300 F. and means for directing said heated fluid at a high velocity on the order of about 4000 to about 9000 feet per minute into contact with the carrier to prevent overheating of the carrier by limiting the temperature of the areas of the carrier which do not have undried material thereon and to remove evolved volatiles from adjacent said carrier to increase the rate of the evolution of volatiles from adjacent the materials being dried, said first radiant heating means and said second fluid heating means being separate and independently operable, whereby said radiant heating means can be operated at a temperature substantially different than that of said fluid heating means; means for exhausting the heated fluid and enolved volatiles from adjacent said carrier; and means for circulating the fluid which is to be directed against said web into heat transfer relationship with said reflector to cool and thereby prevent overheating of the reflector and to heat said fluid.

11. The apparatus of claim 9, together with means for recirculating the fluid from the exhaust plenum to the supply means to conserve the sensible heat in the fluid and means for exhausting a selectively variable portion of the recirculated fluid and replacing it with fresh fluid to thereby decrease the proportion of evolved volatiles in the fluid circulated to the supply plenum.

12. The apparatus of claim 9, together with air bearing means for supporting the carrier as it moves through the apparatus.

13. The apparatus of claim 9, wherein the fluid communication providing means for the heated fluid comprises a plurality of nozzles arranged in a predetermined pateern, at least part of said nozzles being inclined toward the exhaust means to thereby promote the flow of the fluid and its burden of evolved volatiles into said exhaust means.

14. The apparatus of claim 13, wherein the total cross sectional area of said nozzles is in the range of about 1 to about 5% of the area of the carrier against which the radiant energy is projected.

15. Apparatus for drying materials on sheet, web, and similar carriers comprising at least one radiant heatingfluid impingement unit for evolving volatiles from the material on the carrier and means for moving the carrier past said unit, said radiant heating-fluid impingement unit comprising means for forming a zone of radiant energy traversable by said carrier as it moves past the unit, impingement means for directing a heated fluid in a series of jets against the carrier as it moves through the zone of radiant energy to limit the temperature to which the carrier is heated by the radiant energy and to scour evolved volatiles from adjacent the carrier and thereby increase the rate at which the material thereon is dried, and a unit in series with the radiant heating-fluid impingement unit for cooling the carrier after the material thereon has been dried, the fluid impingement means comprising a fluid heater means, duct means connecting said fluid heater means to the means for directing said fluid against the carrier, and a first fluid circulator means for effecting a flow of the fluid to the fluid heater means and from said heater means through said duct means to said fluid directing means and into contact with the carrier, and said cooling means including means for directing a relatively cool fluid at relatively high velocity against the carrier, supply duct means connected to said flow directing means, and a second fluid circulator means for effecting a flow of the relatively cool fluid through said duct means to said flow directing means and said carrier; exhaust plenum means disposed between the radiant heating-fluid impingement unit and the cooling unit for removing evolved volatiles and fluid directed against the carrier in the radiant heating-fluid impingement and cooling units from adjacent said carrier, and duct means 14 connected between said exhaust plenum means and said first fluid circulator means for recirculating fluid from said exhaust plenum means to said fluid heater means to thereby conserve sensible heat in said fluid.

16. Apparatus for drying materials on sheet, web, and similar carriers comprising at least one radiant heatingfluid impingement unit for evolving volatiles from the material on the carrier and means for moving the carrier past said unit, said radiant heating-fluid impingement unit comprising radiant heater means for forming a zone of radiant energy traversable by said carrier as it moves past the unit and means for directing a heated fluid in a series of jets against the carrier a it moves through the zone of radiant energy to limit the temperature to which the carrier is heated by the radiant energy and to scour evolved volatiles from adjacent the carrier and thereby increase the rate at which the material thereon is dried, said unit including a casing having side walls on opposite sides of the path of the carrier through the drying apparatus, and said radiant heater means including an array of electric heating elements oriented transversely relative to the casing with their ends extending through the side walls thereof, said unit further including means co-operating with said side walls to form plenums, and means for circulating at least part of the fluid through said plenums to cool the end portions of said heater elements and to heat said fluid.

References Cited UNITED STATES PATENTS 2,186,032 1/1940 Mann 34-18 XR 2,389,586 11/1945 Andrews 34-68 2,526,189 10/ 1950 Atkinson et a1. 34-68 XR 2,884,705 5/1959 Flynn 34-68 XR 2,896,335 7/1959 Dungler 34-68 3,235,973 2/1966 Smith 34-68 XR 2,391,764 12/1945 Andrews 34-4 XR KENNETH W. SPRAGUE, Primary Examiner.

US. Cl. X.R. 34-68 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N0 3 ,448 ,526 June 10 1969 Horace L. Smith, Jr.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5, line 7, "10,880" should read 10,800 Column 6, line 48, "D6g" should read D6 Column 9, line 4, "valve should read valves line 22, "temperatures" should read temperature Column 12, line 59, "envolved" should read evolved Column 13, line 2, "pateern" should read pattern Signed and sealed this 17th day of March 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr. E. Attesting Officer Commissioner of Patents

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