US 3146563 A
Description (OCR text may contain errors)
Sept. 1, 1964 E. L. WALTERS 3,146,563
PLASTER ROLL-OUT Filed Aug- 20, 1962 4 Sheets-Sheet l INVENTOR.
2066c fidlfdpe ATTORNEYS Sept. 1, 1964 E. L. WALTERS 3,146,563
PLASTER ROLL-OUT Filed Aug. 20, 1962 4 Sheets-Sheet 2 INVENTOR. 16 fim maz ZUaZfWL ATTORNEYS Sept. 1, 19-64 E. L. WALTERS 3,146,563
PLASTER ROLL-OUT Filed Aug. 20, 1962 4 Sheets-Sheet 3 A TTORN E "S United States Patent 3,146,563 PLASTER ROLL-OUT Emmett L. Walters, Toledo, Ghio, assignor to Libbey- Gwens-Ford Glass Company, Toledo, Ohio, a corporation of Ghio Filed Aug. 20, 1962, Ser. No. 217,968 12 Claims. ((Il. l277) The present invention relates broadly to the surfacing of glass sheets or plates by the so-called continuous grinding and polishing system. More particularly, the invention is concerned with an improved apparatus for mounting the sheets or plates upon the work cars or tables of such a system.
The primary object of this invention resides in the pro vision of an improved roll-out apparatus for embedding glass sheets in a layer of plaster of Paris, or other cement used, in such a manner that the glass sheets are secured to the work tables in an efficient and practical manner to facilitate the succeeding treatment of the sheets.
Another object of the invention is to provide roll-out apparatus of the above character including a support frame and a plurality of pressing elements and in which the pressing elements resiliently force the glass sheets downwardly into the laying plaster with substantially uniform pressure to effect the embedding of the sheets on the work tables evenly and uniformly throughout their entire areas.
Another object of the invention is to provide a roll-out apparatus of the above character including novel means for adjusting the amount of pressure that the pressing elements are caused to exert upon the glass sheets.
Another object of the invention is to provide a roll-out apparatus of the above character in which the pressing elements are arranged in axial spaced relation to one another and means is provided for continuously removing accumulations of plaster from the elements thereby obtaining cleaner operating conditions.
A further object of the invention is to provide a rotatable pressing element of glass sheet roll-out apparatus, said element being adapted to rotate about an adjustably mounted axial member and to be movable relative thereto, in common with like elements of the plurality of pressing elements, to rapidly adjust the working pressure of the said elements in a novel, simple and convenient manner.
Other objects and advantages of the invention will become more apparent during the course of the following description when read in connection with the accompanying drawings.
In the drawings, wherein like numerals are employed to designate like parts throughout the same:
FIG. 1 is a plan view of a roll-out apparatus for glass sheets as constructed in accordance with the invention;
FIG. 2 is a longitudinal vertical sectional view of the apparatus taken on line 22 of FIG. 1;
FIG. 3 is a detail sectional view of the pressing elements of the apparatus;
FIG. 4 is a transverse, vertical sectional view taken on line 44 of FIG. 3;
FIG. 5 is a horizontal sectional view taken on line 5-5 of FIG. 4;
FIG. 6 is a perspective view of a component part of the pressing elements;
FIG. 7 is an enlarged detail view;
FIG. 8 is a transverse, vertical sectional view taken on line 88 of FIG. 3;
FIG. 9 is a horizontal sectional view taken on line 99 of FIG. 8; and
P16. 10 is a diagrammatic view of a control system.
It will be readily understood by those versed in the art that, in the so-called continuous system of grinding and 3,145,563 Fatented Sept. 1, 1964 polishing glass, a plurality of glass sheets or plates are mounted upon a series of work tables which are arranged end-to-end and movable continuously in a substantially horizontal path to carry the glass sheets first beneath and in engagement with the tools of a series of grinding units. The partially surfaced sheets are then carried forwardly beneath the tools or runners of a series of polishing units. While the grinding and polishing phases of a continuous glass surfacing system may, and usually do, follow in regular order, it will be also appreciated that glass sheets or plates previously ground on each of their surfaces can be brought to the desired final surface and optical finish in continuous systems wherein only the polishing operation is exercised. In any event, it is customary to secure the glass sheets to the tops or decks of the work tables by embedding them within or on a relatively thin layer of plaster of Paris or some other suitable cementing material. This is, of course, achieved by distributing a thin layer of wet plaster to the decks of the tables, placing a glass sheet or plate thereupon and, before the plaster sets up or hardens, applying substantially uniform pressure over the entire area of the glass sheet to force the same downwardly into the plaster while simultaneously pressing air and surplus plaster from between the glass and the table. The quality of the resultant finish on the glass and the amount of loss by breakage during the grinding and polishing operations is therefore largely dependent upon the proper and level securement of the glass sheets to the supporting work tables.
Referring now particularly to FIGS. 1 and 2 of the drawings, there is shown a roll-out apparatus constructed in accordance with the present invention and designated in its entirety by the numeral 15. As herein illustrated the apparatus 15 is conventionally located in superimposed relation to a series of work tables 16 which are continuously moved forwardly to carry glass sheets 17 therebeneath in the well-known manner. Preparatory to engagement of the glass sheets by the apparatus, the well-cleaned decks of the tables 15 are covered with a layer 13 of plaster of Paris and the sheets or plates are lightly laid thereon in successive, end-to-end relation. Thus, as the tables are moved forwardly the glass sheets in succession are engaged by the pressing elements, generally designated by the numeral 19, of the roll-out apparatus 15, which are adapted to engage the entire area of each sheet and thereby press the same evenly and uniformly into its secured relation in the plaster layer 18.
Generally speaking, the apparatus 15 includes a substantially rectangular frame 25 formed with side structural channel members 26 and 2'7 and transversely disposed structural members 28 secured therebetween. The frame 25 is herein, although not necessarily, provided with a mobile type of support as by the pairs of wheels 29 and 3-0. The pair of wheels 29 are supported by suitable axles journaled in bearings 31 mounted on the channels 26 and 27 while the pair of wheels 30, connected to the opposite ends of jack shafting 33, are likewise journaled in bearings 31.
The pairs of wheels 29 and 30 are adapted to be supported on tracks 34 arranged along and parallel to the path of movement of the tables 16. The shafting 33 is connected through chain drive 35 to a source of power 36 whereby the pair of wheels iii? are power driven and the pair of wheels 29 through the sprocket chains 37; the chains 37 being entrained about sprockets 38 attached to the wheels 29 and 30. During operation of the source of power 36, the apparatus can be propelled forward and back over the sheets to be uniformly embedded in the layer of plaster. Since the novel aspects of the present invention reside essentially in the pressing elements 19 and the structures thereof, the frame 25 can alternatively remain stationary or can be mounted on pedestals fixedly installed on opposed sides of the series of work tables.
As viewed in FIG. 1, the pressing elements 19 are arranged tandem-wise in three axially parallel rows in the frame and each consists of a plurality of rollers arranged in regularly spaced relation to one another. As herein disclosed, the rollers of the first and third or last rows are aligned with one another to traverse identical paths across the glass sheets or plates moving therebeneath while the rollers 4d of the second or intermediate row are arranged in offset or staggered relation to overlap the paths of pressure of the rollers of the leading or following rows. This provides substantially complete, equally distributed pressure over the entire area of the glass sheets or plates and thus acts to embed the same in a plaster layer of uniform thickness.
Since the elevation at which the frame 25 is located and/or supported above the deck or top surface of the work tables 16 is nominally fixed at a predetermined height, the working pressure of the rollers 40 is established initially by the actual positioning of the pressing elements 19 in relation to the tables surface. This positioning or the height of the rollers peripheral surface is, of course, obtained by the combined thicknesses of the plaster layer and of the glass sheets to be surfaced. One of the novel aspects of this invention is to provide means for then establishing, and modifying when necessary, the specific degree of pressure with which the rollers 49 engages the glass sheets and press the same in the plaster layer thereby securing the sheets in uniformly level relation to the tables. Additionally, means is herein provided for continuously breaking up and preventing the accumulation of plaster which would otherwise adhere to the edges of rollers in the spaces therebetween and create objectionable interference to the otherwise satisfactory operation of the individual roller and its cooperative utility with adjoining rollers.
For these purposes, the rollers 49 of each of the pressing elements 19 are generally supported on a tubular or hollow arbor 41 of square cross section which is carried at its opposite ends by arms 42. As shown in FIG. 2, one end of each arm 42 is pivotally mounted by a pintle pin 43 in bracket 44 on an adjoining transversely disposed channel 28 of the frame 25. The opposite or free end of each arm 42 is adapted to rest upon an adjusting screw 45 supported in a structural plate 46 of the frame 25 and equipped with lock nuts 47. Vertical adjustments of the screws 45 at the respective ends of each pressing element obtains the initial positioning of the rollers relative to the work tables. To bodily raise each of the pressing elements, the free end of each arm 42 is attached by clevis 48 to the piston rod 49 of a cylinder 50. As shown in FIGS. 1 and 2, the cylinders 50 are mounted on structural plates 51 of the frame and through piping 52 are connected to a suitable source of pressure (FIG. 10). Accordingly, the initial positioning of the pressing elements 19 is obtained by the adjusted height of the screws 45 while complete removal or raising of the elements from the surface of the glass sheets is effected by the application of pressure to the several hydraulic cylinders 50.
With more particular reference to the structure of the pressing elements 19, it will be seen in FIGS. 3 to 7 inclusive that each consists of a plurality of rollers 4-0 and end retaining members, generally designated by the numeral 55. Each roller 40 is formed by a peripheral rubber roll or tread 56 adapted to be freely rotatable on a supporting core member 57. To provide a wear-resistant outer surface and more resilient inner body portion, each tread 56 includes an outer rubber layer 58 having a hardness of approximately 35 to 40 Shore A durometer with the inner body portion 59 being of 15 to 20 Shore A durometer. In fabricating the tread 56, the body portion 59 is vulcanized to a mounting collar 60 having L-shaped flanged collars 61 secured to the marginal edges thereof. Each L-shaped collar defines an annular recess 62 between the rim 63 of the collar and the surface of the ring 60 (FIG. 7). Alternatively the treads 56 can be circularly recessed to receive the collars 61 and suitably adhered by cement to the outer surface of the collar 69. The inner surface of the collar 69 is recessed in each marginal edge portion to receive a bearing member 64, such as a socalled needle hearing, by which the ring is rotatably mounted on the core member 57. As viewed in FIG. 6, each core member 57 is formed with a central web or wall 65 bounded by an annular rim 66. As herein provided, the rim 66 is equipped with a hardened and ground sleeve 67.
The bearings 64 are maintained from endwise movement and in rolling contact with the surface of the sleeve 67 by means of ring plates 63 which are positioned against the casings of the bearings by means of snap-type locking rings 69; said rings being received in grooves 70 provided in the inner surface of the collar 60 for such purpose (FIG. 7). The core member is adapted to be mounted on the arbor 4-1 for reciprocal motion and also swinging motion within a slight degree of inclination. For this purpose, the wall 65 is axially formed with an oblong opening 7% having a substantially horizontal dimension finished so that the vertical surfaces '71 interfit with the vertical wall surfaces of the arbor, and a vertical dimension between the bottom surface 72 and top surface 73 is slightly greater than the outer dimension or thickness of the arbor, see FIG. 47 Additionally, the top surface 73 of opening 79 is notched or upwardly recessed as at '74 for purposes to be hereinafter more fully described. Integral flanges '75 project outwardly from the web 65 with the inher surfaces thereof being coplanular with the surfaces '71 of opening 76 Each flange 75 is provided with an arcuately shaped end surface '7", with the distance between the associated surfaces 76 being substantially equal to the width of the tread 55 plus the width of the spacing to be maintained between adjoining rollers 40.
As seen in FIGS. 3 and 5, the rollers 40 of each row of pressing elements are thus maintained in spaced relation by the surface to surface contacting arrangement of the arcuate end surfaces '76 of the respective core members. This positioning of the arcuate surfaces 76 also permits free cooperative or individual rocking action therebetween and as occasioned by one or more of the rollers due to the presence of foreign particles, such as lumps of plaster, on the surface of a glass sheet without similar rocking action being necessarily experience by an adjoining roller. The end retaining members 55 are arranged at the opposite ends of each row of pressing elements 19 and are adapted to engage the surfaces 76 of the endmost flanges 75 thereby maintaining the rollers 40 in the above described cooperative relationship. And the space between each of the rollers 46 is closed by a flexible ring or diaphragm member 8i).
As shown in enlarged detail in FIGS. 3 and 7, the flexible ring or diaphragm member 30 is located between each of the adjoining rollers 40 and disposed inwardly from the outer active surfaces thereof to thus define a boundary surface of the spaces between the rollers. Essentially, the ring or diaphragm members function in two capacities, while serving to substantially close the defined spacing, in that they resiliently accommodate angular, or other, displacement of one roller relative to another while maintaining an effective tight seal therebetween. More especially, the diaphragm members are formed of a rubber material and are adapted to rotate with the treads S6 and to be continuously deformed in an outwardly directed action to break up accumulations of plaster from between the opposed end surfaces of adjoining rollers.
The members 80 are circular in outline and in cross section generally resemble a modified capital letter M in that they are produced with a concave or V-shaped center wall portion 31 and two inwardly directed flanged walls 82. Outwardly of the flanged walls 02 there are formed wedgeshaped marginal edge portions 83. Preparatory to the assembly of a diaphragm member in cooperative relation between two adjoining rollers 40, L- shaped retainer rings 34 are adhered to the outer surfaces of the flanges 82 at the inner marginal edge thereof around the circular wall 85 and with the flange or rim 05 projecting outwardly. The wedge-shaped edge portions 83 are then inserted into the recesses 62 with the outer surfaces thereof closely interfitting with the annular rim 63 of the respective collars 61. This positions the rim 86 of the retainer ring 84 in supported relation on the outer margin of the mounting collar 60. In this relationship, the wedge-shaped ends 83 and the rims 86 enclose the recess 62 to convert the same into a more or less sealed chamber which may be filled with a lubricant such as a silicone grease or like suitable material.
In use, the sectors 88 and 09 of the concave center wall 81 are adapted to be distorted or distended outwardly, as shown in FIGS. 4 and 5, thus operating to continuously prevent the drying of plaster in the space between the rollers and causing outward movement of the material onto the glass surface from which it is customarily removed by water sprays and brushing. This distending action is carried out in one area of the wall 81, as indicated by the reference letter A in FIG. 4, by a ball-bearing, or permanently lubricated bushing wheel 90. The wheel is journaled on a screw 91 threaded into the outer end of a bracket 92 mounted by screws 93 on a flanged portion 75 of the core member 57 of each roller 4-0. As best seen in FIGS. 4 and 5 and during rotation of the plurality of rollers, the inverted wall 81 of each diaphragm member 80 is deflected outwardly while moving in contact with the wheel 90 and then by its inherent elastic characteristic returns to the normal inverted or concave relation of the wall portions 83 and 09 which are thus swung outwardly and inwardly from the central crotch area 94 to the juncture of each portion 88 or 89 with the integral flanged walls 82.
As viewed in FIGS. 3 and 5, each of the end retaining members 55 includes means for engaging the arcuate surface 76 of the endmost flanges 75 as well as for sealing the endmost roller per se from the entry of foreign matter in substantially the same manner as the abovedescribed diaphragm members 80. For this purpose, a retention bar 100 is mounted on the vertical walls of the arbor 41 by means of screws 101 which are passed through notches or slots 102 in the bar 100 (see FIG. 9). This permits endwise adjustments to be made between the contacting surfaces 76 of the plurality of rollers 40 before the bars 100 at the opposite ends of the arbor are secured in like contacting relation to the endmost flange surfaces.
The outer surface of each endmost roller is also substantially sealed by the provision of wear rings 103 and 104 having suitably finished surfaces that are resiliently maintained in contact with one another; the ring 103 revolving with the roller while the ring 104 is maintained stationary with regard to the arbor 41. Thus, the peripheral edge of the related collar 60 is provided with substantially equally spaced tapped holes for receiving screws 105 by which a spacing ring 106 and the wear ring 103 are mounted to said collar. The ring 104, on the other hand, is supported by screws 107 on an annular plate 108 carried by the arbor 41 and provided with a substantially rectangular opening 108 through which the arbor is received. As viewed in FIGS. 3 and 8, the upper and lower surfaces of the opening are finished with arcuate surfaces 109 in order that the plate 108 can rock through a vertical plane in response to any rocking movement of the adjoining roller 40. This is, of course, transmitted to the said plate by the interaction of the rings 103 and 104 as the ring 103 is. deflected from the vertical plane with the roller 40 and the ring 104 angularly moves in agreement therewith. The ring 104 is adapted to be supported in surface bearing contact with the ring 103 by the plate 108 which is resiliently urged by a pair of coil springs 110, one end of which are received in sockets 111 provided in the oppositely disposed surface of the plate (FIG. 9). The opposite ends of the springs are similarly received in sockets 112 provided in an annular plate 113 fixed on the arbor 41 by screws 114. The springs are diametrically aligned in a substantially horizontal plane through the axis of the arbor 41. Consequently, during any rocking motion of the plate 108 as influenced by deflection of the associated roller 40 and as transmitted through the surface to surface relationship of the rings 103 and 104, the plate 108 will swing slightly on the arcuately formed edge surfaces 109 of the opening while urging the ring 104 against ring 103 by the action of the springs 110. As aforementioned, the rollers 40 are adapted to rise and fall with reference to the arbor 41, and in the instances of these endmost rollers 40 equipped with wear rings 103, the said rings will easily slide vertically while being maintained in bearing contact with ring 104.
To substantially house and enclose the rings 103 and 104 and the plates 108 and 113 and more particularly the adjoining ends of the endmost rollers 40, a flexible sleeve 115 is placed thereover. The sleeve 115 is formed with a hollow and square hub 115 for receiving the arbor 41; a substantially fiat wall 117 and tubular wall 13 including a corrugated or bellows-like portion 119. The free end of the tubular wall 110 is shaped to interfit with and be located on the annular edge of the plate 100 and outwardly is formed with an L-shaped flange 120 located in close proximity to and having a rim 121 disposed in spaced slightly overhanging relation to the adjacent annular edge of the ring 103. Since the ring 104 follows slight angular deflections of the ring 103, any temporary deformation of the tubular wall 118 will be absorbed in the bellows 119. Likewise in the event the roller 40 with the ring 103 is adjusted vertically relative to the arbor 41, the spaced relation between the ring and the rim 121 of flange 120 will accommodate such movement.
During positioning of the pressing elements 19 for most effective action upon the glass sheets to embed the same evenly and uniformly over their entire area in the plaster layer 10, each element 19 is initially located through the arms 42 and by adjustment of the screws 45 to produce a desired amount of pressure as, for example, a maximum working pressure of 75 lbs. This pressure is then, or eventually, modified by vertical dispdacement of the rollers 40 relative to their respective arbors 41. For this purpose, the arbors are sealed at their ends by plates 125 to create pressure chambers therein and at equally spaced points substantially centrally between the edges of the core members 57, the upper Wall of the arbor is provided with drilled and tapped passages 126 to receive pressure responsive expandable bellows members 127. The bellows 126 are equipped with threaded ends 120 by which they are located in the respective tapped openings. The bellows are thus located in the aforementioned notches 74 of the opening 70 of each core member. Now upon the application of a pressure medium, such as air under pressure, the several bellows will be distended, and, acting against the upper surface of the associated notch, raise the core member and, more especially, the rollers 40 relative to the arbor. In so doing, the core member 57 is slidably moved within the limits of the longer vertical dimension of the oblong opening 70 with the wall surfaces 71 moving relative to the vertical wall surfaces of the arbor.
In order to supply the pressure chamber within the arbor from a convenient source of control, a fitting 120 is attached to a wall of the arbor as in FIG. 5 and connected by piping 130 (FIG. 10) extended to a source of power, such as the pump 131, through the valve 132. Additionally, the arbor 41, adjacent its ends is provided with auxiliary conduits 133 (FIGS. 3 and 5) connecting the bellows 127, associated with the endmost rollers, designated by the numeral 134 of the first and last rows of pressing elements, with individual source of pressure such as at the fitting 135 located in tapped opening 136. The conduits 133 are formed by pieces of tubing bent U-shape and with the upwardly directed ends 137 thereof passed through the respective tapped openings 126 and 136 and placed in sealed relation as the bellows and/ or fitting is turned inwardly thereagainst. The reason for this separation of pressure control for the endmost rollers 134 is to provide a differential in the amount of pressure exerted along the marginal edges of the glass sheets or plates while maintaining a uniform amount and distribution of pressure over the remainder of the sheets and for all practical purposes the entire area thereof.
In actual practice in continuous systems for grinding and polishing the surfaces of glass sheets or plates, a series of work tables 16 are conveyed in a substantially endless horizontal path with the active cycle originating at an area wherein the top surfaces or decks of the tables are thoroughly cleaned and covered by a thin layer of wet plaster or like cementing material. Rough or partially finished glass sheets or plates 17 are then laid on and embedded in the plaster layer and, as the plaster sets up and hardens, are firmly adhered to the work table. In order to insure that the sheets or plates are uniformly level throughout the entire area of their surface, roll-out apparatus of the type herein disclosed is employed to press upon the upper surfaces of the sheets thereby locating the said surfaces at a substantially common height from the surface of the table, to obtain a uniform thickness of finished sheets and also to expel air and surplus plaster from beneath the glass. Accordingly, in positioning a roll-out apparatus above and across the path of movement of the work tables, an initial elevation of the pressing elements 19 is obtained by adjustment of the screws on which the free ends of arms 42 are supported. This determines the height of the rollers 40 and arbor 41 of each pressing element 19 above the deck of the work table or to produce the predetermined amount of pressure to be exerted on the surfaces of the glass sheets passed therebeneath. Now through the use of valves 132, a pressure medium, such as air, is directed from the pump 131 through piping 139 to each of the hollow arbors 411 to effect elongation of the plurality of associated bellows members $.27 thereby raising the rollers 40 relative to the respective arbor and thus modifying the amount of rolling pressure exerted on the sheets. In order that the amount of pressure applied along the opposite margins of the sheets can be varied from that applied over the remainder of the entire area, the valves 138 are employed to introduce air pressure through piping 139 into the conduits 133 and to the bellows associated with the endmost rollers designated by the numeral 134.
During such vertical adjustments of the rollers 40 and/or 134-, the same are guided upwardly or downwardly by the sliding relation of the surfaces 71 of each core member 57 with the vertical wall surfaces of the arbor 41 while the tread is freely rotating relative to said core member on the bearings 64. These bearings are protected against the entry of dirt, Water and more especially wet plaster by the diaphragm members arranged between each of the rollers and also by the sleeves of the retaining members 55 associated with the endmost rollers 134. As plaster accumulates between the rollers, the wheels 99 operate to progressively distort the wall 81 of the diaphragm members 89 to break up the plaster and force the same outwardly onto the glass surface from which it is washed. Since an adjacent diaphragm member 80 as well as the sleeve 115 associated with each retaining member 55 constitute flexible sealing means, the endrnost rollers 1 4- may be vertically displaced relative to the arbor and adjoining roller 40 and/or the retaining member 55 without interference to their utility. Also when one or more of the rollers are caused, for one reason or another, to rock relative to the arbor and/or an adjoining roller, such action is per- 8 mitted by the arcuate end surfaces 76 of the flanges 75 integral with the core members 57 and with the vertical surfaces 71 sliding relative to the vertical wall surfaces of the associated arbor.
In the event that the pressing elements must be bodily raised from the surfaces of the glass sheets therebeneath, pressure from the pump 131 through control valves is directed through piping 52 connected to the cylinders 50 thereby swinging the pivotally mounted arms 42 upwardly. Additionally, if it is found desirable to move the apparatus back and forward across the surfaces of the glass, the motor 36 will drive the pairs of wheels 29 and 30 to carry the frame 25 along the tracks 34. This Will operate to increase the duration and effect the rollout pressure by which the glass sheets are embedded in the layer of plaster although as previously mentioned the frame 25 can be fixedly mounted without departure from the spirit of the invention.
It is to be understood that the form of the invention herewith shown and described is to be taken as a preferred embodiment of the same, and that various changes in the shape, size and arrangement of parts may be resorted to without departing from the spirit of the invention.
1. Apparatus for embedding a glass sheet in a layer of plaster material on a worktable, comprising a plurality of pressing rollers arranged side by side in a row, an elongated arbor on which the rollers are mounted, a carriage, means for mounting the arbor at its opposite ends upon said carriage, each of said pressing rollers including a non-rotatable inner portion mounted for vertical movement upon said arbor and an outer portion rotatably carried by said inner portion, and pressure responsive means acting upon the non-rotatable portions of said pressing rollers for moving them vertically relative to the arbor to vary the pressure of said rollers on the glass sheet, said pressure responsive means including a bellows positioned between the arbor and the vertically movable inner portion of each pressing roller and communicating with a control source of pressure.
2. Apparatus as claimed in claim 1, in which said arbor is hollow and closed at its opposite ends to provide a pressure chamber therein, certain of said bellows communicating with the interior of said arbor, and means for supplying fluid under controlled pressure to the interior of said arbor.
3. Apparatus as claimed in claim 2, including means connecting the bellows acting between the arbor and the inner portion of the end rollers in said row to separately controlled sources of pressure whereby said end rollers are adapted for vertical movement independently of one another and independently of said certain rollers.
4. Apparatus as claimed in claim 1, in which the means for mounting the arbor includes an arm supporting each end of the arbor, means for pivotally mounting the arm at one end upon the carriage, and means for selectively applying downward pressure to the opposite end of said arm.
5. Apparatus as claimed in claim 4, in which the lastnamed means comprises hydraulic means for urging the arm downwardly, and including means carried by the carriage for limiting the downward movement of said arms.
6. Apparatus as claimed in claim 1, in which the nonrotatable inner portion of each pressing roller comprises an annular rim encircling the arbor and spaced therefrom, a web formed integral with said rim and provided with a rectangular opening for receiving the arbor therethrough, the side walls of said opening having a sliding fit with the adjacent side walls of the arbor and the vertical dimension of the opening being relatively greater than that of the arbor.
7. Apparatus as claimed in claim 6, in which said bellows are disposed between the arbor and the inner surface of the web.
8. Apparatus as claimed in claim 6, in which the pressing rollers are spaced from one another and the web is provided with oppositely disposed flanges projecting beyond the annular rim and having arcuately curved outer edges which engage complementary curved edges on the webs of adjacent pressing rollers to space said rollers from one another while permitting angular movement thereof relative to one another.
9. Apparatus as claimed in claim 8, including a flexible ring member encircling the arbor and closing the space between two adjacent pressing rollers.
10. Apparatus as claimed in claim 9, in which the flexible ring member is carried by the outer portions of the two adjacent pressing rollers for rotation therewith.
11. Apparatus as claimed in claim 10, including a tensioning roller carried by the non-rotating inner portion of each pressing roller and engaging the inner surface of :10 a flexible ring member to distort the periphery of the said flexible ring member progressively as the pressing roller rotates to remove plaster that may collect between adjacent pressing rollers.
12. Apparatus as claimed in claim 11, in which the periphery of the flexible ring member is concave, and in which the tensioning roller is positioned opposite said concave portion to force said concave portion outwardly as the pressing roller rotates to remove plaster collected between adjacent pressing rollers.
References Cited in the file of this patent UNITED STATES PATENTS 2,013,614 Lehrling Sept. 3, 1935 2,160,033 Rosin May 30, 1939 2,960,753 Robertson Nov. 22, 1960 3,050,829 Appenzeller Aug. 28, 1962