US 3549004 A
Description (OCR text may contain errors)
United States Patent  Inventor Benjamin Zysman  References Cited lg gg Conn. UNITED STATES PATENTS 1 Appl- 68 r 256 047 4/1882 Randall 271/74x [221 Filed 11,1967 7 7 2 1968 11 277 451 Patented Dec. 22, 1970 3 *i A /237  Assignee American Machine & Foundry Company Prv rmry Examiner-Even C. Blunk a corporation of New Jersey Assistant ExammerDouglas D. Watts Attorneys-George W. Price and Murray Schaffer ABSTRACT: This disclosure contains drawings and a descrip-  BELT FLATTENING DEVICE tion of an improved belt flattening device of the type in which a vacuum source is employed to draw a linear run portion of 12 Claims, 5 Drawing Figs.
an impervious conveyor belt against a planar support surface.  U.S.Cl. 198/184, The surface is established at least in part by a pair of rollers 226/95 having sealing means between the periphery of the rollers and ] Int. Cl. B65g 15/42 the vacuum box assembly, as well as by additional sealing  Field of Search 198/ l 84; means in the form of rails extending between the rollers and at the ends thereof.
PATENTED UEC22 197G SHEET 1 OF 2 INVENTOR 562747722) Z j/sman BY M TTORNEY PATENTED [1EE22 I970 SHEET 2 BF 2 I NVENTOR fiezy'a mz'ia Z ysmmz W WSRNEY VACUUM BELT FLA'ITENING DEVICE This invention concerns improvements in belt flattening devices and particularly a device for preventing buckling and distortion of relatively wide impervious conveyor belts of the type used, for example, in the production of thin sheets of material in the food or the tobacco industries.
In the tobacco industry, various uses have been found for reconstituted tobacco products formed by comminuting or pulverizing various waste portions of tobacco leaves and the like, providing a liquid slurry of the comrriinuted material and depositing the slurry on a smooth surfaced belt for subsequent drying to form a thin sheet of the reconstituted tobacco product. The .sheets are then used in'the manufacture of various tobacco products such as for example, to provide a wrapper for cigars and the like. Also, various dehydrated food products are formed in a similar fashion by. further processing the sheet formed on the smooth surfaced impervious belt to provide a dehydrated food product in the'form of very thin flakes; Regardless of the particular product formed in this manner, it is essential in the interestof'providing a uniform product that the deposition of the slurry onto the belt be very precisely controlled. To this end, various types of gaging or sensing devices are used to sense the physical characteristics of the web or sheet on the belt and provide a control signal by which the deposition of slurry is controlled automatically.
One of the problems presented inthe production of sheet materials of the type referred to, particularly from the standpoint of effectively measuring and thus controlling the characteristics of the sheet as it is formed, i's'that of maintaining the belt in a truly flat or planar condition. To illustrate, belts commonly used for this purpose are formed from thin gage stainless steel and often exceed two feet in width. Such belts not only have an inherent tendency to buckle or to become distorted out of a true plane, but moreover, the differential temperatures to which the belt is exposed during drying augments this deleterious effect.
In accordance with this invention, the problems caused as a result of belt buckling in the production of sheet materials of the type referred to above are substantially overcome by positioning a vacuum box assembly under a linear run portion of the belt and extending substantially across the width of the belt. The upper surface of the vacuum box assembly is formed to establish a flat or planar supporting surface against which the back surface of the belt is drawnby the pressure differential effected by the vacuum box. Also, a plurality of transverse rollers are journaled in the vacuum box along an axis positioned to present a tangent to the roller circumference in the plane'of the supporting surface and arranged with sealing means to avoid a vacuum break between the rollers and the box. In this manner, friction between the belt and the vacuum box is'reduced to a minimum.
Among the objects of the present invention are therefore:
the provision of an improved flattening device for impervious conveyor belts of the type used to form thin sheets of materials deposited on the belt in slurry forrn;the provision of a flattening device of the type referred to which'minimizes frictional drag on the belt and yet which is effective to develop a suffrcient pressure differential to retain the belt against a flat surface; and, the provision of a belt flattening device which is simple in construction and readily adapted to existing machinery.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description to follow, taken in conjunction-with the accompanying drawings in which:
FIG. 1 is a perspective view of a preferred form of the belt flattener of this invention;
FIG. 2 is a fragmentary plan view showing the belt flattening device of this invention;
FIG. 3 is a side elevation of the device in accordance with this invention;
FIG. 4 is an enlarged fragmentary cross section taken line 4-4 ofFIG. 2; and
FIG. 5 is an enlarged fragmentary cross section taken on line 5-5 of FIG. 3.
A preferred embodiment of the present invention is shown in the drawings in its'operative position relative to a linear run portion of an impervious conveying belt 10 formed of such materials as stainless steel, reinforced synthetic resinous materials or the like and movable in the direction of the arrow 12. It will be appreciated that when the flattening device of this invention is used in a conveying apparatus for carrying out the sheet forming processes described above, the section of the belt shown in FIG. 1 is downstream from a slurry spraying or depositing mechanism and at a point where the deposited slurry is being dried, usually at elevated temperatures.
The flattening device of this invention may be characterized as a vacuum box assembly illustrated in FIGS. 1-3 of the drawings and designated generally by the reference numeral 14. As shown, thedevice defines an open top vacuum chamber 16 defined by a boxlike structure including a bottom wall or plate 18, a pair of sidewalls 20, and a pair of end walls, specifically a front wall 22 and a rear wall 24. A pair of exhaust ports 26 are provided in the bottom plate 18 for connection to a suitable source of vacuum as. depicted schematically in FIG. 3. The entire vacuum box assembly 14, in the disclosed embodiment, is suitably supported on angle members 28 hav ing leveling screws 30 for proper adjustment ofthe vacuum box assembly 14 relative to the conveyor belt 10 though it is contemplated that other suitable means of support might be employed.
Extending transversely of the vacuum box 14, and normal to the direction of belt travel as depicted by the arrow 12, are three cylindrical rollers 32, 34 and 36, respectively. Each of the rollers is identical in size and shape and includes a trunnion 37 on each end journaled in a sealed bearing 38 press fit within a counterbore 40 formed in the outside of the side walls 20. Also, it will be noted that the ends of each roll are received in shallow counterbores 42 on the inside of the end walls 20.
As shown most clearly in FIG. 3 of the drawings, the axes of the rollers 32, 34 and 36 are displaced from the upper surface of the sidewalls 20 sufficiently so that a tangent to the circumference of the rollers lies approximately in the plane of th upper surfaces of the front, rear and end walls.
The manner in which a seal is effected between the front and rear rollers 32 and 36 and the front and rear end walls 22 and 24 respectively, is shown most clearlyin FIG. 4 of the drawings. Since the construction of this feature in the front and rear walls is identical, only the front wall 22 will be described in detail. As shown, the front wall 22 is formed with a ledge 44 having a semicircular trough 46 formed therein to receive a circular sealing rod 48 formed preferably from high density polyethylene. The trough 46 and thus the rod 42 lie in a vertical plane passing through the axis of the roller 32 and spaced in that plane so that the uppersurface of the rod 48 engages the lower circumference of the roller 32. The relative diameter of the rod 48 and the trough 46 is selected to permit free rotation of the rod 48 in thetroughand preferably, a suitable sealing liquid, such as water, is provided in the trough to complete the seal between the roller 32 and the front end wall 22. l 4
To effect a seal between the lower surface of the belt I0 and the sidewalls 20, the sidewalls are formed with a upwardly opening groove 50 for receiving a sealing rail 52 preferably formed of a self-lubricating material such as nylon, graphite, or the like. A pair of leaf or how springs 54 underlie the sealing rails 52 in the groove 50 causing the rails to be biased lightly in an upward direction toward the belt 10. The sealing rails 52 are anchored against longitudinal movement by end plate clips 56 secured to the respective ends of the side walls 20 by suitable means such as screw-bolts 58. As shown in FIG. 5, the shallow counterbores 42 on the inside of the sidewalls 20 extend to the groove 50 and thus permit a relatively airtight running seal between the ends of therollers and the rails 52.
The front and rear rollers 36, therefore, together with the rails 52 presented in the upper surfaces of the sidewalls 20 define a bearing frame for the belt with low friction surfaces for contacting or supporting the belt and which lie in a single plane. Moreover, an effective seal is provided between the lower surface of the belt 10 and the vacuum chamber 16 by virtue of the sealing rails 52 on the sidewalls and the circular rods 48 disposed between the end walls 22 and 24 and the front and rear rollers 32 and 36. Also, it willbe noted that the transverse dimension of the vacuum box 14 is selected so that the sealing rails 52 are spaced by a distance less than the width of the belt 10, thereby insuring complete coverage of the vacuum box opening and thus of the chamber 16 by the belt. Accordingly, the development of a negative pressure or vacuum in the chamber 16 will draw the belt 10 toward the rollers 32, 34 and 36 and the upper surfaces of the sidewalls against the light biasing effect of the bow springs 54 underlying the sealing rails 52. In this manner, any buckling or distortion in the belt 10 out of a single plane will be corrected as it passes over the vacuum box assembly 14. Furthermore, any tendency for the vacuum box assembly to impose a significant drag on the moving belt 10 is reduced to a minimum by the rollers 32, 34 and 36 which establish the principal supporting contact for the belt against the vacuum in the chamber 16, as well as the self-lubricating sealing rails 52.
Thus it will be appreciated that by this invention an extremely effective flattening device is provided and by which the above objects are completely fulfilled. Also it will be apparent to those skilled in the art that various modifications can be made in the belt flattening device of this invention. Accordingly, it is expressly intended that the foregoing description is illustrative of a preferred embodiment only.
1. 1n a flattening device for impervious conveyor belts, said device including a vacuum box as employed to provide a chamber opening engageable with an impervious belt while moving and thus retain a linear run portion of said belt within a single plane, the improvement comprising: a pair of rollers journaled in the assembly for rotation about axes extending transversely to the direction of belt travel, said rollers establishing part of said supporting surface and thus being tangential to a single plane, and means to provide an airtight seal between each of said rollers, and said vacuum box assembly, said means defining a trough in said vacuum box assembly for each of said rollers respectively, said trough extending in a line parallel to the axis and its respective roller and adapted to contain liquid, in a cylindrical rod floated in said trough and in engagement with said respective roller for rotation therewith, whereby the development of a vacuum in said chamber is effective to draw a buckled impervious belt supported on said rollers into linear contact therewith.
2. The apparatus recited in claim 1 including further seal means extending in the direction of belt travel at each end of said rollers, said further seal means being engageable with the belt and with the ends of said rollers to establish a sealing frame in said single plane.
3. The apparatus recited in claim 2 wherein said further seal means includes a pair of rails formedof low friction material and means to bias said rails resiliently toward the belt.
4. The apparatus recited in claim 1 including at least one further intermediate roller between the rollers of said pair.
5. The apparatus recited in claim 1 wherein said rail means are supported in grooves formed in the upper edges'of said sidewalls, and including spring means for biasing said rail means upwardly.
6. In a flattening device for an impervious conveyor belt, means including bottom, side and end walls to establish an up wardly opening vacuum chamber, and means establishing a low friction bearing frame about the. perimeter of said chamber, said frame defining a substantially planar supporting surface for a linear run portion of the belt to be flattened, such last mentioned means comprising a roller supported rotatably on an axis extending parallel to each of said end walls, the circumference of said rollers and said end walls, and rail means su ported in said side walls to effectthe seal between the ends 0 said rollers, said rail means being supported in grooves formed in the upper edges of said side walls and including spring means for biasing said rail means upwardly, said side walls having recesses on the inner surfaces thereof opening to said grooves and receiving the ends of said rollers, thereby effecting a running seal between the ends of said rollers and said rail means.
7. A flattening device for impervious conveyor belts, said device comprising: means defining a substantially planar supporting surface adapted to engage one side of the belt to be flattened and a central opening in said surface extending in a direction normal to belt movement for a distance less than the width of the belt; means to establish a vacuum chamber in fluid communication with said central opening; and at least two rollers joumaled on an axis extending in a direction normal to belt travel and displaced from said surface to locate a tangent on the roller circumference in the plane of said surface and at least one of said rollers being in contact with a circular sealing rod disposed below said roller and lying in a vertical plane passing through the axis of the roller.
8. The apparatus as recited in claim 7 wherein the means to establish said vacuum chamber includes a vacuum box assembly having bottom, end and sidewalls, means to connect one of said walls to a source of vacuum and at least one end wall of said vacuum box including a ledge having a semicircular trough therein for supporting said circular sealing rod.
9. The apparatus as recited in claim 7 wherein the means defining a substantially planar supporting surface includes a low friction bearing frame on the upper edges of said side and end walls. I
10. The apparatus as recited in claim 7 in which said roller is journaled on means supported in said sidewalls.
11. In combination: an impervious'conveyor belt having a linear run portion; and means to retain said linear run portion; and means to retain said linear run portion in a single plane, said means comprising a vacuum box having bottom, side and end walls, a low friction bearing frame on the upper edges of said side and end walls to establish a planar surface for engaging one side of said belt, the dimension of said frame in a direction normal to belt travel being less than the width of said belt; and at least two rollers supported for rotation on an axis normal to belt travel and displaced from said surface to locate a tangent on the roller circumference in the plane of said surface and at least one of said rollers being in contact with a circular sealing rod disposed below said roller and lying in a vertical plane passing through the axis of the roller.
12. The combination recited in claim 11 in which at least one of said rollers is a cylindrical sleeve joumaled on a concentric axle, said axle being supported in said sidewalls.