US2971218A - Machine for continuously curing elastomeric material in sheet form - Google Patents

Description

Feb. 14, 1961 J. M. BIERER 2,971,218 MACHINE FOR CONTINUOUSLY ING ELASTOMERIC FORM MATERIAL IN SH Filed Nov. 14, 1957 3 Sheets-Sheet 1 J. M. BIERER ON Feb. 14, 1961 2,971,218 MACHINE FOR c TINUOUSLY CURING ELASTONERIC MATERIAL IN SHEET FORM 5 Sheets-Sheet 2 Filed Nov. 14, '195'7 1961 J. M. BIERER ,97

MACHINE FOR CONTINUOUSLY CURING ELASTOMERIC MATERIAL IN SHEET FORM Filed Nov. 14, 3.957 3 Sheets-Sheet 3 Fig. 4

INVENTOR'.

United States Patent ice MACHINE FOR CONTINUOUSLY CURING ELAS TOMERIC MATERIAL IN SHEET FORM John M. Bierer, Newton, Mass, assignor toAmerican Biltrite Rubber Co., Inc., Chelsea, Mass., a corporation of Delaware Filed Nov. 14, 1957, Ser. No. 696,438

8 Claims. (Cl. 18-6) This invention comprises a new and improved machine for curing or vulcanizing elastomeric strips or sheets of resinous, plastic or rubber compounds. The invention includes within its scope the continuous process of treating such materials as carried out with the assistance of the improved machine.

The invention is herein disclosed as embodied in a vulcanizing machine of the well-known Rotocure type having a heated drum, a cooperating pressure band and guide rolls which lead the band in a generally triangular path including the partial encirclement of the drum.

In such machines as heretofore constructed the sheet material has been introduced at the bite of the pressure band and drum as determined by one of the guide rolls. In dealing with material of certain compositions it has been found that if the sheet or strip is subjected to substantial pressure at the bite there is a tendency of the material to roll back and form a more or less permanent wave at the entering point. This is objectionable as causing a product of uneven thickness. Furthermore, there occurs a marked loss in molding pressure which results in poorly molded, blistered or otherwise defective sheet material. I have discovered that these defects may be remedied by reducing the pressure of the band at the point of introduction and providing an intermediate pres sure roll operating to apply full pressure to the material only after it has been confined between the drum and the band for a sufficient distance to eliminate all tendency to roll back the stock. In a machine so organized the stock is introduced between the pressure band and the drum and advanced a sufficient distance to confine a substantial length of the strip between the drum and the band, and then increasing and applying full pressure to the stock only after creating a confined area of suflicient extent to resist the phenomenon of roll back.

As herein shown the full pressure is applied to the stock by an intermediate pressure roll located beneath the heated drum, while the point of introduction of the stock and bite of the drum and band is determined by a guide roll located approximately 45 from the intermediate pressure roll in respect to the circumference of the drum.

A characteristic feature of the machine of this invention as that the intermediate pressure roll is so located as to deflect the pressure band and to be biased by the band itself toward the drum for applying the desired full pressure of the stock. The pressure band is herein shown as maintained under severe tension by hydraulic means and the tension thus developed is adequate to advance the intermediate pressure roll with suflicient pressure to reduce and mold the stock to the desired thickness of the finished product and preparatory to the curing or vulcanizing operation which occurs in the further passage of the stock about the drum after leaving the pressure roll. j l

The machine is further characterized by the provision of means for moving the pressure roll toward and from the drum to vary and regulate its effective pressure upon 2,971,218 Patented Feb. 14, 1961 the pressure band at this point in the treatment of the stock.

Still another feature consists in the provision of means for adjusting the pressure roll circumferentially with respect to the drum so that both the length of the confined area of the stock may be governed as well as the precise circumferential point of application of molding pressure to the stock.

The mechanism herein shown for carrying out these functions and the mechanical structure involved constitute further features of the invention. These and other characteristics will be best understood and appreciated from the following description of preferred embodiments thereof selected for purposes of illustration and shown in the accompanying drawings in which:

Fig. 1 is a view in side elevation of the complete machine shown somewhat diagrammatically.

Fig. 2 is a view in perspective of the intermediate pressure roll,

Fig. 3 is a diagrammatic view on a larger scale'illustrating the initial treatment of the stock, and 1 Fig. 4 is a view in elevation similar to Fig. 1 but showing a modified construction of the machine.

The invention is herein shown as embodied in a machine of the type more fully disclosed in US. Letters Patent No. 2,656,565, Apel and Collins, employing an endless steel pressure band of the type which is the subject-matter of Patent No. 2,083,527, Bierer. The frame 10 is of massive construction having two side members in which is rotatably mounted a large drum 11 having steam connections, not shown, by which it may be maintained at the desired curing and vulcanizing temperature. Partially encircling the heated drum is the endless pressure band 12 which is guided in a generally triangular pathby passing over guide rolls 13, 14 and 15. The guide roll 13 is located in a substantially ten oclock position with respect to the drum and power is applied to this roll for driving the system. The roll 14 is located somewhat below the level of the drum 11 in approximately eight oclock position with respect thereto and acts to guide the pressure band 12 into contact with the drum and determine the location of the bite and point of introduction of the material being treated. The arrow in Fig. 1 indicates the direction of travel of the stock in approaching this point.

The roll 15 is journaled between a pair of arms 16 pivoted at their lower ends to the frame and forced continuously outwardly at their upper ends by hydraulic cylinders 17 which are pivotally connected to the side members of the frame and provided with pistons 18. The function of the roll 15 is to maintain the pressure band 12 under severe and continuous tension so that it will exert heavy pressure upon the elastomeric material passing beneath it upon the arcuate portion of the drum 11 which it encircles.

The guide roll 14 is journaled at opposite ends in crossheads 19 which are movable toward and from the drum 11 in guideways formed in the side members of the frame. The position of each crosshead is controlled by a shaft 20 connected to a motor 21 through a reducing gear 22. By operating these motors the position of the roll 14 with respect to the drum 11 may be adjusted and thereby the initial pressure upon the stock may be adjusted at the bite between the band 12 and the drum 11.

The elements of the machine described up to this point corresponds substantially to those of the machine more fully described in Patent No. 2,591,995. In order, however, that the stock may be confined under relatively light pressure over an area of sufficient length to eliminate roll back, the present machine is organized to apply full molding pressure to the stock at a distance from the bite herein shown by way of example as approximately 45 of the drum circumference. Accordingly, an intermediate pressure roll is mounted torotate on a horizontal axis located vertically beneath the drum 11 or substantially in the six oclock position. The roll 25 has a transverse shaft 26 which extends completely across the frame of the machine and out through apertures cut in its side menu bers; At its ends the shaft 26 is journaled in arms 2'7 pivotally mounted to swing about a transverse shaft 28. Each of these arms has a downwardly extending ear to which is connected the piston rod 31 of a hydraulic cylinder 29. The latter is pivotally mounted in a bracket 3% fast to the base of the frame and is double acting whereby the pressure roll 25 may be moved downwardly in opposition to'the tension of the band 12 or upwardly to supplement the action of the band in increasing its pressure on the stock in process of treatment. Each of the arms 27 has an outwardly projecting car 32 movable between adjustable stops 33 which may be set to limit the movement of the arms 27 and the pressure roll carried thereby. While the travel of the roll 25 is, strictly speaking, in an are described about the axis of the pivot shaft 28, its departure from straight line movement is very slight within the range of required adjustment. It will be noted that the side members of the frame are shaped, to permit endwise removal of the drum 11 and that the actual bearings for the drum are removably bolted to the side members of the frame. The arms 16 which carry the tensioning guide roll 15 are provided with upwardly extending brackets in which is journaled a stripper roll 35 operating to separate the cured stock from the pressure band 12 as the stock is advanced upon the band traveling from the driving guide roll 13. The heated drum may be provided with a segmental heater 23 so that stock is heated from both sides in its passage about the drum from the intermediate pressure roll 25 to the guide roll 13 at which point it leaves the drum 11. The guide roll 13 may be cooled and a supplementary cooler provided in position adjacent to the band 1.2 as it advances from the roll 13 to the tension roll 15.

Fig. 3 depicts diagrammatically the treatment of the stock 37 as introduced at the bite between the pressure band 12 and the drum 11 and in its passage about a portion of the drum 11. The lower guide roll 14 deflects the pressure band 12 to form the bite between it and the drum 11 where the stock 37 is introduced into the ma- ;chine. If this bite is made too narrow and the initial pressure too severe for the stock in hand, it will cause a roll back of the material designated in Fig. 3 by reference character 38. It is this roll back which the machine and process of the present invention are designed to completely eliminate in actual practice. Accordingly, the guide roll 14 will be set so that the stock is engaged under relatively light pressure at the bite and there will be no suggestion of the roll back 38 shown in this figure. When the machine is set in operation accordingly, the stock is advanced under relatively light pressure from the bite from the roll 14 to the point at which the intermediate pressure roll 25 applies its severe molding pressure to the pressure band 12 and the stock beneath it. The initial movement of the stock, under relatively light pressure and heat from the drum 11, progresses through the arc 34 and at that point is indicated an inward deflection of the pressure band 12 in response to the application of full molding pressure by the roll 25. No roll back is caused at this point because a substantial area of the stock is firmly engaged throughout the are 34 between the band 12 and the rigid surface of the drum 11 which thus provides opposed cooperating surfaces, and such engagement of the extended area of the stock prevents the distortion thereof which might otherwise result in the objectionable roll-back phenomenon.

In Fig. 4 the machine is shown as equipped with an intermediate pressure roll 49 so mounted that it may be adjusted 'circumferentially with respect to the heated drum 11. As shown in this figure the roll 40 is carried by a transverse shaft 41 journaled at opposite sides of the frame 10 in rockers 42. Each of the rockers is connected by a pivot 43 to the lower end of an arm 44 which is pivotally mounted at its upper end upon a short shaft or stud 45 carried by an angle bracket 46 bolted to the side member of the frame. It will be understood that the elements shown in Fig. 4 are duplicated on the other side of the frame.

A hydraulic cylinder 47 is pivotally secured at its upper end to the arm 44 and is fitted with a piston and rod 48 pivotally connected with an arm of the rocker 42 extending toward the left from the axis. The cylinder 47 has flexible fluid pressure connections, not shown, and is double acting so that it may be used' to swing the rocker 42 about its pivot 43 and so adjust the pressure roll 40' toward or from the drum 11 to decrease or augment the molding pressure of the roll derived from the pressure band 12. In this respect the cylinder 47 has the function of the cylinder 29 already described in connection with the machine of Fig. 1.

In order to limit the extent of this adjustment each arm 44 is provided with an outwardly extending perforated lug 54 through which extends a rod 55 pivotally mounted upon a lug projecting upwardly from the rocker 42. A pair of adjustable stops 56 are carried by the rod 55 on a threaded portion thereof and these stops may be set to limit the in-and-out adjustment of the roll 40 and so predetermine its position and operating pressure in accordance with the stock to be treated.

It will be seen from the description thus far that the two rockers 42, the roll 40 journaled therein and the cylinder 47 are all carried by the arms 44 and may be bodily moved as a sub-assembly about the circumference of the drum 11 by oscillation of the arms 44 about the axis of the drum 11. In order to effect such adjusting movement each rocker is provided with a downwardly extending arm carrying a swivel block 50 through which extends a threaded screw 49. At its outer end the screw 49 is journaled in a swivel block 51 projecting outwardly from the frame 10. The screw is provided at its outer end with a sprocket wheel 52 and a hand crank 53. The corresponding screw at the other side of the machine frame is provided with a sprocket wheel and geared by a sprocket chain to the wheel 52. Accordingly, when the hand crank 53 is turned, both of the screws 49 are rotated and the roll 40 is moved along the circumference of the drum 11.

In order to maintain the true running of the pressure band 12 throughout its path, it is contemplated that one of the arms 16 supporting one end of the tension roll 15 may be mounted for vertical adjustment by the employment of such mechanism as that described and claimed in the co-pending application of Knowland Ser. No. 630,586, filed December 25, 1956. This mechanism is not herein shown since it forms no part of the present invention though in practice it is an important element of the machine as a whole.

A continuous molding or curing machine organized and operating as above described has been found in practice to be fully elfective in eliminating the roll back phenomenon encountered in machines heretofore available. The elimination of this defect contributes to the production of a sheet product of even thickness well molded andfree of blisters and other defectsthat have heretofore caused impairment of the high quality that must be secured particularly in dealing with resinous compositions of relatively high cost.

Having thus disclosed my invention and described in detail an illustrative example thereof, I claim as new and desire to secure by Letters Patent:

-1. The process of continuously molding and curing elastomeric sheet material with the elimination of rollback, which is characterized by the steps of first confining between the surfaces of a heated rotating drum and an encircling pressure band a length of sheet material equal to approximately 45 of the circumference of the drum under comparatively light initial pressure sufficient to cause compression and heating of the confined area of the elastomeric material without roll-back, then causing the band to apply a severe molding pressure to the material beyond its area of initial compression thereby reducing the thickness of the material while rollback is prevented by an immediately following area of heated material compressed under the said light initial pressure.

2. A machine for continuously curing elastomeric sheet stock including in its structure a heated drum, a single steel cooperating pressure band partially encircling the drum, a pressure roll bearing against and exerting pressure toward the drum on an encircling portion of the band, and means for adjusting the operative position of said pressure roll circumferentially about the axis of the drum with respect to the encircling portion of the band.

3. A machine for continuously curing elastomeric stock comprising a frame, a heated drum rotatably mounted at its opposite ends in said frame and a pressure band partially encircling said drum within the frame, together with fixed brackets secured to the opposite sides of the frame, arms pivotally secured to the brackets for movement about the axis of the drum, and a pressure roll carried by said arms and extending transversely across the drum and in contact with a portion of the band encircling the drum.

4. A machine as described in claim 3 in which the arms carrying the pressure roll are mounted concentrical- 1y with respect to the heated drum, and means are provided for simultaneously swinging said arms to adjust circumferentially the relation of the roll and drum.

5. A machine as described in claim 3 in which the arms carrying the pressure roll are also provided with means for adjusting the said roll in a substantially radial direction with respect to the drum.

6. A machine for curing elastomeric stock in strip form, comprising a frame, a heated drum mounted to rotate within the frame, a single steel cooperating pressure band encircling an arcuate portion of the drum and maintained under tension and in direct contact with strip stock on the drum, a pressure roll rotatably supported at its opposite ends from the sides of the frame and extending across the drum and in contact with an encircling portion of the band, means for bodily moving said roll circumferentially about the drum, and means for bodily moving said roll toward or from the drum in all positions of circumferencial adjustment.

7. A machine as described in claim 6 in which the pressure roll is journalled at its opposite ends in rockers carried by arms mounted concentrically with respect to the drum.

8. A machine as described in claim 6 in which the pressure roll has a shaft extending transversely across the frame and out through cut out portions of side members thereof, bearing arms pivotally mounted outside said frame members and providing bearings for said shaft, and the pressure band being looped about the pressure roll and tending by its tension at all times to swing said roll and its bearing arm toward the drum.

References Cited in the file of this patent UNITED STATES PATENTS 2,656,565 Apel et a1. Oct. 27, 1953 2,663,052 Goulding Dec. 22, 1953 2,681,612 Reimann June 22, 1954 FOREIGN PATENTS 1,005,482 France Dec. 26, 1951 327,468 Germany Oct. 11, 1920 5,854 Great Britain Feb. 3, 1900 of 1899 490,498 Great Britain Aug. 16, 1938

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