US3379593A - Lubrication method and apparatus for paperboard machine - Google Patents

Description

April 23, 1968 G. w. MAZE ET AL 3,379,593

LUBRIGATION METHOD AND APPARATUS FOR PAPERBOARD MACHINE Filed Feb. 5, 1964 [:HII

ATTORNEYS United States Patent 3,379,593 LUBRICATION METHOD AND APPARATUS FOR PAPERBOARD MACHINE Glenn W. Maze and Alvin B. Walker, Toledo, Ohio, assignors to Owens-Illinois, Inc., a corporation of Ohio Filed Feb. 3, 1964, Ser. No. 342,169 Claims. (Cl. 156-278) This invention relates generally to the manufacture of corrugated paperboard and more particularly to the improvement in strength and appearance of paperboard cartens or blanks from which cartons are made. More particularly, the invention relates to improved method and apparatus for laminating double backed paperboard by use of emulsified lubricants in minute quantities on the end portions of fibers of the paperboard, the lubricant quality depending on the state of a material which is liquid at processing temperatures and solid at normal temperatures of use in the finished product.

Paperboard cartons are normally constructed of one or more paper thicknesses forming one face or liner to which is secured a corrugated inner web member and a second liner is glued on the opposite side to complete a double backed paperboard. Backings and web are assembled or laminated by automatic machinery, and conventionally glued together with adhesives containing water. Normally, lamination is by continuous line assembly wherein the web and backing sheet elements are unrolled from supply rolls and brought together in a continuous process. Application of the adhesive may be on the inner surface of the two liners but preferably on the inner web member after shaping it into a fluted or corrugated form before contacting the inner liners in order to minimize glue used and avoid excessive moisture. Usually the web and one liner, herein referred to as the inner liner or the upper liner, are first assembled and glued to form a single backed board and the outer or bottom liner is thereafter glued in place. In manufacturing such double faced board it is desired to print labels or descriptive material directly on the bottom liner after lamination and cutting to size. The outer bottom face is therefore normally left uncoated as the exposed surface later to be processed through a print ing machine.

During the lamination process in which single faced board is given its lower liner or facing sheet, the single faced board is conveniently brought in from above to the gluing machine where glue is placed on the lower end portions of the corrugated flutings, as by means of a kiss roll. Paper in roll form is brought into bottom contact with the glued portions of the single faced board while passing along a horizontal machine to the bottom liner of the double faced board. It then passes to curing ovens which dry or cure the glue to complete the assembly. A substantial pressure is required to maintain the final facing material in contact with the corrugated web during the curing process in order to secure a good bond. Good thermal contact is required between the bottom liner and the ovens to effect a rapid drying of the glue. The ovens are generally steam heated to a suitable curing temperature such as 350 F. Curing ovens usually have a polished upper surface on which the double backed board is urged along by a moving belt contacting the upper face or liner. Driving means between the oven surface and the bottom liner is ordinarily precluded by the thermal transfer requirements. However, the weight of the paperboard and the bonding pressure provide a high frictional force as the assembled paperboard is slid along the upper surface of the heating ovens. In prior practice this has resulted in serious difficulties due to slippage between the glued flutings of the corrugated web and the lower liner while the glue is still soft and possesses little 3,379,593 Patented Apr. 23, 1968 tenacity. This has resulted in poor bonding and in blistered board. To avoid this fault, excessive amounts of glue have been applied but this becomes too expensive and adds too much moisture, resulting in warped board.

Previous efforts to overcome these difficulties have included efforts to coat the lower face of the sheet with a lubricant of some type or to spray thereon an oil or other lubricating material. Such efforts have not solved the problem, and have frequently resulted in inferior paperboard products which were difficult to print and had less pleasing surface appearance. Oil on the lower surface has proven ineffective for sufficiently reducing the friction and has had other disadvantages such as contamination of the product by oil below the exposed surface. These problems have resulted in the necessity to discard some hundreds of thousands of cartons annually at a single plant with the best previously known lubricating techniques. Furthermore, excessive glue requirements have made the product more subject to small slippage errors which cause inexact cut sizes when the continuous sheet material is blanked into carton form. Also the power consumed in the double backing machine has been a considerable factor.

It is accordingly an object of this invention to provide improved lubricity for paperboard during the final lamination process.

Another object is to provide an improved means of applying a lubricant to a fibrous material.

A further object is to provide a method of lubricating a fibrous sheet which affects only the exterior fiber ends in contact with a bearing surface.

Still another object is to assure good lubrication of a fibrous object at a processing temperature while improving the antislip properties thereof at normal temperatures.

It is also an object to provide means and method of applying minute quantities of lubricant to a paper product in controlled intermittent batches to minimize the lubricant adhering to the product.

Other objects and advantages of the invention will be apparent on further description of the invention in connection with the drawings in which:

FIG. 1 is a diagrammatic elevational showing of a double backing machine employing the present invention;

FIG. 2 is a diagrammatic showing of spray apparatus suitable for use in the apparatus of FIG. 1;

FIG. 3 is an enlarged view of a portion of the apparatus of FIG. 1 illustrating application of a lubricant to the bottom liner; and

FIG. 4 is an enlarged view of the product showing lubricant particles on the bottom liner passing the ovens in FIG. 1.

The objects and features of this invention are achieved through use of especially prepared dilute emulsions of selected wax-like materials in minute quantities on the outer surface of a liner. To obtain a sufiiciently sparse application of a lubricant material, the emulsion is made very dilute and is applied sparingly to the heated metal roll during a very small percentage of the operating time. Contact with the heated roll evaporates the water from the emulsion leaving a complete but extremely thin or microscopic coating which is transferred in the form of minute droplets to outermost fibers of the paper passing over the roll. These droplets are carried onto the heated surfaces of the treating ovens and redistributed as fine droplets over the whole surface area on which the paper product slides. The roll first receiving the emulsion is at a temperature considerably above the boiling point of the water and of the wax-like lubricant to effect a distribution of the lubricant in the liquid state so sparsely spread as to result in microscopic droplets being transferred by adhering to only the outermost fibers of the surface of the liner being lubricated. Lubrication is typi cally a characteristic of liquid droplets some of which later solidify on the outermost fibers. This solidified material, in some cases when the emulsion material is selected as herein noted, imparts to the finished product a degree of tackiness greater than that of the nonlubricated liner material under the same circumstances. By use of a highly dilute emulsion intermittently applied for a small fraction of the running time, the quantity of material employed is exceedingly small and has no effect on the appearance of the final product.

Double backing apparatus is well known in the paperboard industry but is illustrated in FIG. 1 for the purpose of description of the present improvement. Laminating machinery generally includes an overhead bridge such as 5 carried by support 6 above a floor 7 supporting the entire apparatus. Bridge 5 carries roll 8 on support 9 attached to the bridge. For the purpose of this description, a single backed board 10 passes over roll 8 and thence to the glue machine shown generally at 11. Board 10 normally comprises upper liner 12 to which is glued a corrugated web 13 having an exposed fluted lower face. Single backed board 10 is flexible in one direction and passes around tension roll 14 to preheater roll 15 and thence to glue machine 11 where rider roll 16 presses board 10 into contact with applicator roll 17. Roll 17 applies to the tips of flutes 18 a small quantity of glue as at 19 by rotation in a tray 20 of glue or like cementing compound, suitably supported within the gluing machine.

A double backer machine ordinarily includes a supply roll 21 carrying a bottom liner 22 over positioning roll 23 and tension roll 24 which is normally adjustable to maintain constant tension on the liner 22 as it passes into the bonding machine. Preheater rolls 25 and 26 serve to bring the bottom liner to a temperature at which the glue on the tips of the flutes 18 begins to harden upon contact with liner 22. Positioning rolls 27, 28 and 29 maintain thermal contact between the liner 22 and the rolls 25 and 26 throughout a substantial portion of the circumference thereof to effect a desired preconditioning of the bottom liner before lamination. Rolls 25 and 26 and the positioning rolls associated therewith are suitably supported on bases 30 and 31 above floor 7.

Bottom liner 22 proceeds into the curing oven shown generally at 32. Frame 33 supported by floor 7 normally carries a number of steam heated ovens 34 arranged transversely of the laminating assembly and have polished metal upper surfaces thereon over which the double backed board passes during curing of the glue. At the entrance of the oven assembly there is generally a beveled receiving plate or oven 35 which brings the lower liner 22 into contact with the glue coated flutings 18 of the single backed board 10. Belt 36 is driven by a drive roll (not shown) and suitably tensioned at the opposite end thereof by the idler roll 37 to provide conveying means for urging the combined paperboard along through the oven 32. Belt 36 is preferably of cotton or Dacron material to provide positive frictional drive for board 10. Weighted rolls 38 supply the bonding pressure by which the corrugated Web 13 is forced into contact with the upper surface of liner 22 to secure proper bonding be tween flutes 18 and liner 22 by means of the glue 19. The finished product is shown at 40 in FIG. 1 and in cross-section in FIG. 4.

It has been noted that ovens 34 provide heat for curing the glue or bonding cement at flutes 18 to the liner 22, and for this purpose these ovens are normally supplied with steam at a temperature above 300 F., typically approximating 340 F. Preconditioning rolls 25 and 26 are normally held to a similar temperature so that the liner on first contacting glue 19 begins immediately to adhere to the fluted tips 18. Driven belt 36 accordingly carries along the double backed board during the curing process, and the board emerges in finished form at 40.

FIG. 3 illustrates in detail application of an emulsified wax-like lubricant to the roll 25. A pressurized tank 41, which may have a capacity such as 10 gallons and carries, according to one embodiment of the invention, a pressure approximating 40 pounds maintained by regulated air supply 42 at a pressure indicated by the gage 43. Tank 41 contains an emulsion illustrated at 44 of a specially prepared mixture of lubricant and water. A delivery line 45 extends to the lower portion of tank 41 and to spray nozzles 46, which are connected by manifold 47, adjustably mounted on a fixture 48 attached to tank 41. A valve 49 between the line 45 and the manifold 47 controls the intermittent application of spray from nozzles 46. The valve, in turn, is controlled by a timer 50 which may be a lock-controlled timing switch controlling a solenoid in the valve 49 for the actuation of the spraying operation. A bleeder valve 51 permits removing all air from the line 45 and the manifold 47 so that each actuation initiated by timer 5!! produces a spray for the full duration of a spraying interval. According to the circumstances and choice of materials for compounding the emulsion, timer 50 may have variable on and 01f" periods, but is found generally satisfactory when timed to produce a spray of a few seconds duration at intervals varying from one or two to four minutes. It will be appreciated that long lasting lubricant materials would require actuation of the timer 59 less often than the materials of less durability.

One of the features of this invention is the accurate control of the quantity of emulsified lubricant applied to liner 22 and for this reason it will be appreciated that roll 25 should not be coated with emulsion 44 more often nor for a longer interval than is actually required. The addition of further emulsion to the surface of roll 25 is harmful in that it provides too much of the lubricating material and results in irregular distribution thereof and in a different running speed for the material through the ovens 32. For this reason it is important to prevent operation of timer 50 except when roll 25 is in operation to pass liner 22 therealong. For this purpose a switch 52 is so located as to close for operating timer 50 only when the laminating machine is in operation. It is illustratively associated with a frictional actuator 53 on the axle of roll 25 according to well known principles for closing the switch only during the operation of the machine. Suitable connections 54 and 55 supply current from a source not shown to switch 52 and to timer 50, and further leads 56 connect the timer to the valve 49.

In FIG. 4 there is illustrated in cross-section a portion of the finished board 40 on the lower surface of which are minute droplets of lubricant 57 adhering to the outermost fibers extending below the main portion of the liner 22. Droplets 57 are generally microscopic in size and are sparsely distributed over the surface of liner 22, both because of the method of application to roll 25 and because of the spreading action inherent in processing the paperboard according to the illustrated procedure.

It will be appreciated that spray nozzle 46 may apply a substantially complete coating to roll or drum 25, and that this roll, perhaps of 36" diameter, rotates a number of times during a five second interval of spraying to provide a uniform covering of the surface by the emulsion. Running speeds of 300 to 600 feet per minute are to be expected. However, drum 25 is heated much in excess of the boiling point of water and the emulsion is quickly reduced to a thin coating of liquid lubricant material. To insure uniformity of coating nozzles 46 may be placed at separations of 8 to 10 inches and may be disposed 12 inches or more from the surface of the drum. The spray pattern preferably overlaps slightly between individual nozzles 46, and an invisibly thin coating of material on drum 25 is produced. Only the outermost fibers of liner 22 contact this film of lubricant each picking up minute droplets during rotation of roll 25. Liner 22 thus receives a continuing supply of tiny droplets which are carried along to rolls 28, 29, to oven 35, and thereafter to each of the ovens 34. As these liquid droplets contact the broad surfaces of the ovens they are further subdivided to ultimately form a finely dispersed covering on the ovens as well as on the outermost fibers of liner 22. The droplets are far too sparse and too minute to provide a coating or any penetration into the surface of liner 22. These droplets carried by the liner 22 are smeared across the faces of ovens 34 to provide a thin film of lubricant on the faces of the ovens. Depending of course on the amount of lubricant fed to the liner 22, during the travel of the liner over the oven faces there is a continuing exchange of lubricant between the paper and the oven face. Those droplets adhereing to fibers at the far end become solid particles upon cooling as the liner emerges from the curing ovens and serve as an antilubricant material desired to promote better palletizing of the finished cartons.

While the lubricant material utilized according to this invention is a fundamental factor in its success, there is a choice of materials found satisfactory when applied in controlled amounts according to this procedure. Differing materials are applied at different frequency in accordance with the durability of the resulting lubricant coating on the face of the drum and ovens. Application according to this invention involves at processing temperatures a liquid coating so thinly applied to the drum as to permit only microscopic droplets to be picked up by individual fibers, and these droplets are further wiped over the heated oven surfaces to form further comminuted and dispersed particles. These are invisible but effective in friction reduction, and upon cooling become solid to impart an increased tackiness to the paperboard.

As a preferred example, applicants compounded an emulsion comprising an emulsifiable microcrystalline wax having a melting point of about 150 F., 3.5 parts by weight of triethanolamine were dissolved in 54 parts by weight of water heated to the temperature of 200210 F. In 30 parts by weight of microcrystalline wax 12.5 parts by weight of stearic acid were dissolved at a temperature of 200-210 F. The solution of stearic acid in microcrystalline wax was then slowly poured in and stirred until the emulsion was smooth and homogeneous. The resulting emulsion was in a form to be diluted by the addition of any desired amount of water at any time convenient. It is preferably diluted to provide a resultant emulsion in the range of 1% to 5% by weight of wax. Variations from this percentage from a fraction of 1% to may require adjustment in duration of spray interval or in other controllable factors in application to the drum 25, however, applying a minimum thicknes of liquid wax to the drum, thereby assuring that transfer of wax is in microscopic droplet form. According to the example cited, the liner 22 was passed over drum 25 at a rate from 300 to 600 feet per minute. An emulsion comprising 1%, or more in other examples, of wax was applied thereto for periods approximating 5 seconds during each interval of three and one-half minutes. Each spraying interval thus continued for several rotations of the drum and intervals between spray applications were approximately 100-200 drum rotations. An adequate supply of lubricant was obtained in this manner. This may be readily observed by measurement of power consumed by the drive motors operating belt 36, being reduced 25-40% with a very low consumption of lubricant material. This provides sufficient friction reduction as the liner passes over the ovens 34 to prevent slipped liners and blistered board formerly causing a large percentage of rejections. The cooled paperboard had increased antislip properties for improved handling ability of the blanks and finished cartons as compared to untreated paperboard,

Other materials were found satisfactory for lubrication in substitution for the microcrystalline wax, but provide less desirable antislip properties after cooling. One of these is a low melting point polyethylene, prepared in emulsion form generally in the same manner as prescribed for the microcrystalline wax. Two forms of such material are commercially supplied under the trade names Epolene E-14 from Eastman Chemicals Corporation, and AC 629 from Allied Chemical Corporation. These materials have melting points about 215 F. and are emulsifiable according to the cited example. Oven temperature is normally about 300 F. so that the wax-like lubricant is far above its melting point during use as a lubricant.

Polyoxethylene stearate manufactured by Atlas Powder Company and sold under the trade name of Mirj 45 is suitable for use as a solution in the practice of the invention and produces a satisfactory lubricant somewhat less durable and less satisfactory than the microcrystalline wax. Aqueous solutions of a material referred to by the trade name of Carbowax 400, a polyethylene glycol made by Union Carbide Corporation have also been found to be satisfactory but less desirable than the microcrystalline wax in respect to durability and economy. Other forms of Carbowax having higher melting points and higher molecular weight may also be satisfactory for the purpose. Microcrystalline wax is most satisfactory with respect to lubrication qualities at the running temperature and antislip properties at normal temperatures of use.

For each of the materials which might be substituted for the microcrystalline wax a different time of application may be required according to its durability. It has been found that paraffin wax, for example, requires application much more often than microcrystalline wax. Emulsions of polyethylene of suitably low melting point are found to possess the necessary lubricity but impart to the finished product an increased slipperiness, whereas a decreased slipperiness is desired. Each of the other named wax-like materials may be handled within the limits of the temperatures indicated but have various disadvantages with respect to durability or lubricity and antislip qualities desired in the finished product.

It will be noted as an important feature of this invention that means have been devised for applying lubricant in an extremely uniform manner in a quantity several orders of magnitude too small to form a complete covering for the surface of the liner material. At the same time, the manner of application is such as to provide this minute quantity of lubricant material on only the exposed portions of those fibers of the liner sheet which extend from the surface. Accordingly, only those fibers in a position to bear the principal frictional stress in passing along the ovens 34 become lubricated. By first emulsifying the lubricant in a dilute form and applying this emulsion to a roll an extremely thin film of lubricant is formed on the drum 25 which only the outer surface fibers of liner 22 can reach to pick up droplets of the molten wax, limited in size by the thinness of the liquid coating on the drum. Droplets of molten wax are carried along to the ovens and there further distributed entirely across some 40 feet or more of running surface to form thereon a still more sparse dispersion which may be in the form of a thin partial film comprised of micro-droplets. The dispersion on the surfaces of ovens 34 is longlasting irrespective of the duration of the wax coating on drum 25.

This invention results in an improved method of lubrication as a paperboard double backer which uses a minimum of lubricant but is found to improve the final product and to greatly reduce warpage in the finished board as well as the amount of blistered board produced. Furthermore, the avoidance of slippage between the liner 22 and the web 13 permits a more accurate cutting of dimensions in the finished product when it is blanked or cut for carton formation. According to previous methods of lubricating paperboard passing through the finishing oven it was noted in one box plant that the rejects due to these causes often exceed a rate of 200,000 box blanks per year, most such rejects being eliminated by the procedure herein disclosed.

It will be appreciated that variations may be made in the number of nozzles and their disposition with regard to the drum 25, as well as the location of the spray nozzles with respect to the entrance to the bonding area. An emulsion of less than 1% Wax content may be desirable under certain circumstances with appropriate adjustment in application time to provide a micro-coating of liquid lubricant for transfer to the liner to reduce the drag forces as measured by the current drawn by the drive motors from 25% to 40%.

Variations may be practiced according to this invention illustratively described in terms of specific examples, but applicants intend to be limited only within the scope of the appended claims.

What is claimed is:

1. A laminating process including lubrication of the sliding surfaces in a double backer apparatus fed with a glue-treated web and a bottom liner which comprises the steps of passing said liner over a preheating roll prior to laminating,

intermittently spraying upon said roll with a water emulsion of a wax-like material, said emulsion comprising of the order of 1% to 10% of said material to provide upon evaporation of water therefrom a deposit too thin for coating for impregnating said liner,

transferring to only the outermost fibers of the lower side of said liner minute portions of said material, contacting the upper side of said liner with said gluetreated web to effect a preliminary bond,

passing said web and liner over heated curing ovens in contact therewith, and

continuously transferring some of said material to running surfaces of said ovens to effect a lubrication thereof. 2. A process according to claim 1 wherein said emulsion contains miorocrystalline Wax and stearic acid comprising less than 10 percent of the emulsion.

3. A process according to claim 1 wherein said emulsion comprises a mixture of microcrystalline wax, stearic acid and triethanolamine in proportions approximating 10, 4 and 1 parts, respectively, to at least 100 parts of Water.

4. A method of treating a bearing face of a paperboard to provide a lowered friction characteristic with respect to a supporting surface therefor at the temperature of processing and an increased tacky characteristic at normal temperatures of use which includes steps of passing said paperboard face in rolling contact with a roll surface,

partially spraying without completely coating said roll surface with a dilute water emulsion of a waxy material of the group, microcrystalline wax, polyethylene, polyethylene glycol and polyoxyethylene stearate,

evaporating the water from said emulsion and melting the residue thereof in contact with said roll before contact with said paperboard face to apply to protruding fibers minute bits of said residue in liquid form in an amount insufiicient to impregnate or coat said face,

spreading said bits evenly over said face by sliding the face along surfaces heated to a temperature in excess of the melting point of said material, and

cooling the paperboard to a temperature below the melting point of said material to solidify said bits and thereby provide said increased tacky characteristic.

5. A method of lubricating sliding surfaces of a double facer apparatus wherein a paper sheet is glued beneath another sheet and cured in position, which comprises steps of passing said sheet over a rotating drum,

intermittently applying to said drum a dilute emulsion comprising substantially 1% by weight of microcrystalline wax on a side rotationally removed from said sheet in an amount less than suificient to coat the drum on each rotation thereof.

heating said emulsion to evaporate water therefrom and melt said Wax prior to contact with said sheet, said wax being insufiicient to coat the outer fibers of said sheet,

passing said sheet into contact with a succession of smooth surfaces heated substantially above the melting point of said wax, thereby to distribute said Wax in microscopic quantities over said surfaces of the facer apparatus to be lubricated.

6. In the method of claim 5 said coating step including impinging said emulsion on said drum in a fine spray during a first interval, discontinuing said coating step during a subsequent interval while wax remains on said surfaces and applying further spray for a like interval thereafter, and controlling said intervals of spraying to avoid accumulating an amount of wax sufiicicnt to either coat or impregnate said fibers.

7. A process for providing temporary lubricity with a wax-like lubricant material in minute quantities at the outermost fibers of a paperboard liner in a manner to avoid impregnating said fibers or producing a continuous coating thereon during a double backing operation, comprising the steps of passing said liner in contacting relationship over a feed roll,

intermittently spraying a dispersion of said material on said roll in an amount insufficient to fully coate said roll with residue upon the vaporization of water therefrom,

maintaining the temperature of said roll sufficiently above the boiling point of the water and the melting temperature of said material to remove the water and melt the material upon contact with the roll,

passing said paperboard in sliding contact along a heated surface to distribute the molten residue in liquid droplet form along said paperboard fibers contacting said heated surface, and

cooling said paperboard to a temperature at which said mate-rial is solid.

8. In the process of claim 7 said lubricant material being applied as a deposit of polyethylene thinly dispersed in water to provide a molten film on said feed roll of microscopic thickness.

9. In a process of claim 7 said lubricant material being a dispersion of polyoxyethylene stearate in dilute form to provide a molten film on said feed roll of microscopic thickness.

10. in the process of claim 7 said lubricant material being an aqueous dispersion of polyethylene glycol forming a wax film on said feed roll.

References Cited UNITED STATES PATENTS 2,819,986 1/1958 Edwards et al 11792 2,908,578 10/1959 Barker 106-8 2,964,470 12/1960 Wentworth 117139.5 3,145,118 8/1964 Mahoney 117111 3,189,502 6/1965 Little 156-210 3,192,052 6/1965 Cunning et al 117105.4 3,243,310 3/1966 Hull et a1. 106-10 EARL M. BERGERT, Primary Examiner.

W. E. HOAG, Assistant Examiner.

Claims (1)

1. A LAMINATING PROCESS INCLUDING LUBRICATION OF THE SLIDING SURFACE IN A DOUBLE BACKER APPARATUS FED WITH A GLUE-TREATED WEB AND A BOTTOM LINER WHICH COMPRISES THE STEPS OF PASSING SAID LINER OVER A PREHEATING ROLL PRIOR TO LAMINATING, INTERMITTENLY SPRAYING UPON SAID ROLL WITH A WATER EMULSION OF A WAX-LIKE MATERIAL, SAID EMULSION COMPRISING OF THE ORDER OF 1% TO 10% OF SAID MATERIAL TO PROVIDE UPON EVAPORATION OF WATER THEREFROM A DEPOSIT TOO THIN FOR COATING FOR IMPREGNATING SAID LINER, TRANSFERRING TO ONLY THE OUTERMOST FIBERS OF THE LOWER SIDE OF SAID LINER MINUTE PORITIONS OF SAID MATERIAL, CONTACTING THE UPPER SIDE OF SAID LINER WITH SAID GLUETREATED WEB TO EFFECT A PRELIMINARY BOND, PRESSING SAID WEB AND LINER OVER HEATED CURING OVENS IN CONTACT THEREWITH, AND CONTINUOUSLY TRANSFERRNG SOME OF SAID MATERIAL TO RUNNING SURFACES OF SAID OVENS TO EFFECT A LUBRICATION THEREOF.

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