CA1312301C - Low tension plastic conveyor belt system - Google Patents
Low tension plastic conveyor belt systemInfo
- Publication number
- CA1312301C CA1312301C CA000614315A CA614315A CA1312301C CA 1312301 C CA1312301 C CA 1312301C CA 000614315 A CA000614315 A CA 000614315A CA 614315 A CA614315 A CA 614315A CA 1312301 C CA1312301 C CA 1312301C
- Authority
- CA
- Canada
- Prior art keywords
- belt
- driving
- conveyor belt
- tower
- plastic
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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- Structure Of Belt Conveyors (AREA)
Abstract
LOW TENSION PLASTIC CONVEYOR BELT SYSTEM
Abstract of the Disclosure An all-plastic conveyor belt of the type that is collapsible on curves is used in a low tension system, progressing in a helical path around a drive cage or tower.
The modules making up the belt have end members with recesses for receiving the heads of plastic rods which hold the modules together. The heads are thus recessed and will not wear against bars or other components of the drive cage or tower of the low tension system. The end members of the belt modules in one embodiment are slightly concave for better conforming to the surfaces of the driving tower or cage.
Abstract of the Disclosure An all-plastic conveyor belt of the type that is collapsible on curves is used in a low tension system, progressing in a helical path around a drive cage or tower.
The modules making up the belt have end members with recesses for receiving the heads of plastic rods which hold the modules together. The heads are thus recessed and will not wear against bars or other components of the drive cage or tower of the low tension system. The end members of the belt modules in one embodiment are slightly concave for better conforming to the surfaces of the driving tower or cage.
Description
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4 Background of the Invention The invention relates to conveyor belt systems, and more 6 particularly to a low tension system wherein a plastic 7 conveyor belt is used, in such a way as to eliminate most 8 wear problems.
9 Plastic conveyor belts have been in increasing use, particularly in the food industry where dwell time in an 11 oven, a freezer or other food treating environment is needed, 12 for a maximum amount of product and with minimum space 13 requirement. These belts are also used in the electronics 14 and computer industries. See, for example, U.S. Patent No. 4,742,907 directed to a plastic conveyor belt formed of a 16 series of modules, assigned to the same assignee as the 17 present invention. Such a plastic conveyor belt is designed 18 to travel in straight paths and around curves, and may make 19 both left and right curves. The belt collapses on the inside of curves, having rods connecting adjacent belt seg~ents 21 through slotted holes.
22 Some plastic conveyor belts have had end members or end 23 plates which are thickened and have recesses at their outer 24 surfaces, for recessing the head of a rod SQ that the rod head does not protrude out from the end member or end plate.
26 This prevents snagging of the heads on components of the belt 27 driving or guidance system.
28 In low tension spiral conveyor belt systems (such as 29 Ashworth Low Tension Spiral System) a belt, generally of metal, travels in a helical path around a rotating driving 31 tower or cage or drum. The belt passes over a driven 32 sprocket at a take-up drive location separate from the 33 driving tower. In passing around and in contact with the 34 driving tower, the belt is friction driven, assisted in its movement generally throughout the length of the belt's path 36 on the tower, greatly reducing tension in the belt as 37 compared to tension which would occur if the belt were only 38 driven from one point. The belt is actually driven at a ~^j.
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great number of points of conkact with the cage or drum.
In sueh low tension systems, ~he edges of the belts have been engaged generally by bars or vertical members or rods of the driving cage or tower. The edges of the belts have generally been irregular, with end structure of the component belt modules exposed and irregular and not smooth. This is often due to exposed and protruding heads of transverse module connecting rods, and results in snagging of the rod heads against the driving cage and in excessive wear of the rod heads or other protruding components or surfaces of the belt as well as of the cage members.
The problem is particularly accentuated by the fact that the tower or cage must be driven at a speed somewhat ~aster than that of the belt in an overdrive condition, inasmuch as the belt is moving both horizontally and vertically along the cage. A slipping condition therefore exists between the edge surfaces of the belt and the external surfaces of the driving tower or caye. This condition must exist whether the belt starts from the bottom and ends up at the top or starts from the top and ends up at the bottom in relation to the moving cage. (The cage is actually driving the belt supported by spiral support strips around the drum or the cage, up or down, as shown in the drawings and discussed further below).
Previous to the present invention, there has been no suggestion for solving this problem by eliminating snagging, tearing and catching and thereby improving the performance, wearability and life of a low tension conveyor belt system utilizing a plastic conveyor belt, as in the present invention described below.
.
~3~23~1 2a 7171~-~0 Summarv of the Invention In accordance with the present invention there is provided a low tension conveyor belt system with a plastic conveyor belt, comprising, a driving tower or drum on a substantially vertical axis, with a wearstrip belt support platform arranged in a helical path around the driving tower, an endless plastic conveyor belt positioned on a wearstrip belt support and extending tangentially off the wearstrip belt support and away from the driving tower, with means separate from the driving tower for engaging the driving belt and feeding it in a return path back to the driving tower and onto the wearstrip belt support at an opposite axia]. end of the dxiving tower from the position at which the belt exited the driving tower, and said plastic conveyor belt being assembled from a series of plastic belt modules each having end members at its ends, and the adjacent belt modules heing interconnected by rods passing through openings in the modules in interdigited projections of the adjacent modules, said end members having a substantially smooth æurface which engages against the exterior surfaces of the driving : tower, whereby the plastic conveyor belt operates smoothly around the driving tower, without snagging and without excessive wear of exposed co~ponents on the edge o~ the belt engaged by the drivlng tower.
In accordance with the present .invention ~here is provided, a low tension spiral conveyor belt system includes an :
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2b 71714-10 endless conveyor belt of all plastic or substantially all plastic components. The belt is made up of a series of elongated plastic modules with interdigited projections held together by plas~ic rods passing transversely through bores in the overlapping projections. At the ends of the plastic rods are heads or : ~ :
:
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.
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1 other end members holding the rods in the plastic modules, 2 and these heads are recessed into end members of the plastic 3 modules, each of which has, at least on one side of the belt, 4 a recessed or enlarged outer bore portion in the end m~mber, for receiving the rod head.
6 In this way, the plastic conveyor belt of the low 7 tension system of the invention presents relatively smooth 8 surfaces to the driving cage or drum which engages the edge 9 of the belt at the inside of its curvature. The belt is more efficiently driven by the drum, wear to the edges of the belt 11 and to the driving drum or cage is minimized, and the 12 overdriving or higher speed of rotation of the drum in order 13 to move the belt both horizontally and vertically is more 14 readily accomplished.
The plastic conveyor belt system of the invention 16 efficiently travels around the curves in a way not possible 17 with previously available belts. It is therefore efficiently 18 used in the described low tension system, spiraling around 19 the driving cage.
In a speci~ic embodiment, the end plates or members at 21 the ends of the belt modules, which form the exposed surfaces 22 of the inside edge of the belt, are slightly curved to match 23 the curvature of the driving drum. This further reduces wear 24 and adds to the frictional engagement of the driving drum against the belt edges, tending to further reduce tension in 26 the conveyor belt by evenly applying driving power to the 27 belt as it rides on wear strip surfaces in its helical path 28 around the drum.
29 In another specific embodiment, the belt segments or modules include side plates at the inside of the curve which 31 may be of a different material than the rest of the belt~ In 32 this way a plastic material of higher friction coefficient 33 can be used for the side plates, where friction with the 34 driving tower should be relatively high. This is different from the belt's horizontal surface engagement with the 36 helical wear strip on which it rides, where friction must be 37 minimized. Friction with the driving tower, however, should 38 not be so high that the lifting of the belt along the tower, :: ~
~3~3~
1 which requires vertical sliding along the tower's bars, is 2 interfered with significantly.
3 Another embodiment of the invention, which can be 4 combined with either or both of the above embodiments, includes raised outer plates on one or preferably both sides 6 of the belt. The raised plates ~eep products from falling 7 off the belt or running into the cage.
8 It is therefore among the objects of the present 9 invention to improve over prior low tension spiral conveyor belt systems with driving towers or drums, by incorporating 11 in such a system a substantially all plastic conveyor which 12 is free of rod heads or other protrusions on the belt's edge 13 at the inside of the curve where the belt progresses 14 helically around the drum. These and other objects, advantages and features of the invention will be apparent 16 from the following description of a preferred embodiment, 17 considered along with the accompanying drawings.
19 Description of the Drawings Figure 1 is a perspective view generally illustrating a 21 low tension spiral conveyor belt system in accordance with 22 the invention.
23 Figure lA is a schematic elevational view of the system 24 shown in Figure 1.
Figure 2 is a plan view showing details of construction 26 of a plastic conveyor belt incorporated in the system 27 illustrated in Figure 1.
28 Figure 3 is a plan view showing another embodiment 29 wherein each belt module has attached to it a separate, non-integral end plate.
31 Figure 4 is a partial plan view showing the belt curving 32 around a driving tower or drum of the low tension system, 33 illustrating the contact between the driving tower and the 34 edges of the conveyor belt, and including a variation of the construction shown in Figure 3.
36 Figure 5 and 6 are plan and side elevation views showing 37 another modification of the plastic conveyor belt.
, .
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1 Description_of Preferred Embodiments 2 In the drawings, Figures 1 and lA show a low tension 3 conveyor belt system 10 in accordance with the principles of 4 the invention. The system 10 includes a plastic conveyor belt 12, preferably with all plastic or substantially a~l 6 plastic components~ a take-up belt drive or sprocket drive 7 which may be at a sprocket 14 driven by a motor (not 8 specifically shown), additional feed sprockets 15, 16 and 17, 9 a take-up sprocket 18, and additional sprockets 20 and 22, all defining a path through which the conveyor belt 12 is 11 fed. The system includes a helical wearstrip belt support or 12 ramp 24 and a driving tower or cage or drum 26 about which 13 the wearstrip ramp is positioned and against which the belt 14 12 engages at its inside edge as it travels helically around the drum 26.
16 As is known in the prior art, the driving cage 26 is 17 intended to drive the conveyor belt (which has generally been 18 a steel conveyor in the prior art) by engaging against the 19 inner edge of the belt with vertical bars or spindles 28 or other exterior drum structure, thereby providing driving 21 force to tha belt at many points (or substantially 22 continuously) along its movement and accordingly greatly 23 reducing tension in the belt as compared to a belt driven 24 from a single location.
The driving cage, as in prior systems, is rotated at a 26 speed slightly higher than that of the moving belt 12, 27 providing a positive driving assistance to the belt, and a 28 constant slipping of the driving cage over the edge surfaces 29 of the belt occurs. This is an "overdrive" condition. There must be sufficient overdrive to lift the belt and load along 31 the inclined ramp 24 while also moving it generally 32 horizontally. The take-up drive 14 acts as an assist and 33 tension drive, and moves the belt only horizontally in 34 relation to the cage.
However, in prior systems having a driving cage or drum 36 for belt driving and lowering of tension, there has been 37 present a series of protrusions at the edge surfaces of the 38 belt enga~ing the driving drum. Primarily these have ' 2 ~
1 comprised heads or ends on connecting rods which secure 2 successive belt modules together. Although such systems have 3 functioned satisfactorily, they have produced excessive wear 4 on the protrusions, such as the rod head, and distortion of the belt as well as the sur4ace of the driving drum itself 6 (occasionally the vertical bars of the driving cage have been 7 of plastic to reduce this wear problem). The protrusions 8 have also interfered with the smooth engagement of the belt 9 by the driving drum, reducing the effective frictional engagement between the belt edges and the surfaces of ~he 11 driving drum. This has resulted in reduced efficiency of the 12 low tension system and in relatively severe variations in the 13 degree of tension of the belt and surges of the belt as it 14 passed around the drum.
In the system of the present invention, these problems 16 are eliminated by the use of the plastic conveyor belt 12 in 17 the structure as illustrated particularly in Figures 2, 3 and 18 4. As shown, plastic connecting rods 32 which serve to 19 connect adjacent belt modules 34 have heads 36 on each end which are protected from interference or engagement with 21 driving surfaces of the driving drum 26. The rods 32 connect 22 interdigited projections 38 of each belt module as depicted 23 in the drawing. Their heads 36 lie in recesses 40 formed in 24 end members 42 of the belt modules. The recesses 40 comprise enlarged bores on the axis of smaller bores 44 which extend 26 through the end members and all pro~ections of the 27 interdigited structure.
28 As illustrated in Figure 2, the rod heads 36 do not 29 protrude beyond the outer surface of the end members 42 of the belt modules. As discussed above, this avoids excessive 31 wear of the belt module, of the rod and of the driving cage 32 as the belt is "overdriven" by the cage.
33 Figure 3 shows a portion of the belt 12, i.e. several 34 modules 34 connected by rods 32 which are also preferably of plastic. In this embodiment, the end members of the modules 36 34 comprise separate plates 46, non-integral with the body of 37 the module 34. The cage engaging plates 46 have bores 48 and 38 recesses 50, as in the end members 42 discussed above and ::
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1 shown in Figure 2. The use of separate plates enables the 2 cage-engaging members to be of a higher-friction material 3 than the body of the module 34. This is important in 4 controlling the friction between the driving drum or cage and the belt in rela~ion ~o the force required to lift the belt, 6 and it enables minimizing friction (with a different plastic 7 material) between the belt's lower surface and the wearstrip 8 24 on which it slides.
9 Figure 4 shows a portion of a belt 12a which is traveling in an arcuate path around the driving cage 26. In 11 the belt 12a, end plates 46a are slightly modified, arcuately 12 (concavely) shaped for a more complementary engagement 13 against the driving drum. An outer cage-engaging surface 52 14 of each end plate 46a is concave, with a radius generally matched to that of the driving drum or cage 26. This can 16 help promote still smoother frictional driving of the belt by 17 the drum.
18 Figures 5 and 6 show a further variation which can be 19 used in combination with what is shown in Figures 3 and 4.
In this embodiment the separate plates 46a are raised, 21 extending substantially higher than the top surface of the 22 belt 12a, to provide barriers at both left and right for 23 retention of product on the belt. In many uses of such 24 belts, products are loaded quite densely on the belt, and there often is low friction between the belt and the bottom 26 of the product. Thus, items can tend to slide o~f the belt 27 or into the driving cage, on a belt without edge barriers.
28 In the present invention the barriers are integral with the 29 separate end member plates 46a of each belt module, thus enabling the plate to cooperate in providing a higher 31 friction driving surface (as discussed above) while also 32 functioning to hold product on the belt.
34 I CLAIM:
~' ,
9 Plastic conveyor belts have been in increasing use, particularly in the food industry where dwell time in an 11 oven, a freezer or other food treating environment is needed, 12 for a maximum amount of product and with minimum space 13 requirement. These belts are also used in the electronics 14 and computer industries. See, for example, U.S. Patent No. 4,742,907 directed to a plastic conveyor belt formed of a 16 series of modules, assigned to the same assignee as the 17 present invention. Such a plastic conveyor belt is designed 18 to travel in straight paths and around curves, and may make 19 both left and right curves. The belt collapses on the inside of curves, having rods connecting adjacent belt seg~ents 21 through slotted holes.
22 Some plastic conveyor belts have had end members or end 23 plates which are thickened and have recesses at their outer 24 surfaces, for recessing the head of a rod SQ that the rod head does not protrude out from the end member or end plate.
26 This prevents snagging of the heads on components of the belt 27 driving or guidance system.
28 In low tension spiral conveyor belt systems (such as 29 Ashworth Low Tension Spiral System) a belt, generally of metal, travels in a helical path around a rotating driving 31 tower or cage or drum. The belt passes over a driven 32 sprocket at a take-up drive location separate from the 33 driving tower. In passing around and in contact with the 34 driving tower, the belt is friction driven, assisted in its movement generally throughout the length of the belt's path 36 on the tower, greatly reducing tension in the belt as 37 compared to tension which would occur if the belt were only 38 driven from one point. The belt is actually driven at a ~^j.
13~23~
great number of points of conkact with the cage or drum.
In sueh low tension systems, ~he edges of the belts have been engaged generally by bars or vertical members or rods of the driving cage or tower. The edges of the belts have generally been irregular, with end structure of the component belt modules exposed and irregular and not smooth. This is often due to exposed and protruding heads of transverse module connecting rods, and results in snagging of the rod heads against the driving cage and in excessive wear of the rod heads or other protruding components or surfaces of the belt as well as of the cage members.
The problem is particularly accentuated by the fact that the tower or cage must be driven at a speed somewhat ~aster than that of the belt in an overdrive condition, inasmuch as the belt is moving both horizontally and vertically along the cage. A slipping condition therefore exists between the edge surfaces of the belt and the external surfaces of the driving tower or caye. This condition must exist whether the belt starts from the bottom and ends up at the top or starts from the top and ends up at the bottom in relation to the moving cage. (The cage is actually driving the belt supported by spiral support strips around the drum or the cage, up or down, as shown in the drawings and discussed further below).
Previous to the present invention, there has been no suggestion for solving this problem by eliminating snagging, tearing and catching and thereby improving the performance, wearability and life of a low tension conveyor belt system utilizing a plastic conveyor belt, as in the present invention described below.
.
~3~23~1 2a 7171~-~0 Summarv of the Invention In accordance with the present invention there is provided a low tension conveyor belt system with a plastic conveyor belt, comprising, a driving tower or drum on a substantially vertical axis, with a wearstrip belt support platform arranged in a helical path around the driving tower, an endless plastic conveyor belt positioned on a wearstrip belt support and extending tangentially off the wearstrip belt support and away from the driving tower, with means separate from the driving tower for engaging the driving belt and feeding it in a return path back to the driving tower and onto the wearstrip belt support at an opposite axia]. end of the dxiving tower from the position at which the belt exited the driving tower, and said plastic conveyor belt being assembled from a series of plastic belt modules each having end members at its ends, and the adjacent belt modules heing interconnected by rods passing through openings in the modules in interdigited projections of the adjacent modules, said end members having a substantially smooth æurface which engages against the exterior surfaces of the driving : tower, whereby the plastic conveyor belt operates smoothly around the driving tower, without snagging and without excessive wear of exposed co~ponents on the edge o~ the belt engaged by the drivlng tower.
In accordance with the present .invention ~here is provided, a low tension spiral conveyor belt system includes an :
: - . - , .
~ .
13~23~
2b 71714-10 endless conveyor belt of all plastic or substantially all plastic components. The belt is made up of a series of elongated plastic modules with interdigited projections held together by plas~ic rods passing transversely through bores in the overlapping projections. At the ends of the plastic rods are heads or : ~ :
:
~ : : ' .
:: :
.
`` ~3~2:3~
1 other end members holding the rods in the plastic modules, 2 and these heads are recessed into end members of the plastic 3 modules, each of which has, at least on one side of the belt, 4 a recessed or enlarged outer bore portion in the end m~mber, for receiving the rod head.
6 In this way, the plastic conveyor belt of the low 7 tension system of the invention presents relatively smooth 8 surfaces to the driving cage or drum which engages the edge 9 of the belt at the inside of its curvature. The belt is more efficiently driven by the drum, wear to the edges of the belt 11 and to the driving drum or cage is minimized, and the 12 overdriving or higher speed of rotation of the drum in order 13 to move the belt both horizontally and vertically is more 14 readily accomplished.
The plastic conveyor belt system of the invention 16 efficiently travels around the curves in a way not possible 17 with previously available belts. It is therefore efficiently 18 used in the described low tension system, spiraling around 19 the driving cage.
In a speci~ic embodiment, the end plates or members at 21 the ends of the belt modules, which form the exposed surfaces 22 of the inside edge of the belt, are slightly curved to match 23 the curvature of the driving drum. This further reduces wear 24 and adds to the frictional engagement of the driving drum against the belt edges, tending to further reduce tension in 26 the conveyor belt by evenly applying driving power to the 27 belt as it rides on wear strip surfaces in its helical path 28 around the drum.
29 In another specific embodiment, the belt segments or modules include side plates at the inside of the curve which 31 may be of a different material than the rest of the belt~ In 32 this way a plastic material of higher friction coefficient 33 can be used for the side plates, where friction with the 34 driving tower should be relatively high. This is different from the belt's horizontal surface engagement with the 36 helical wear strip on which it rides, where friction must be 37 minimized. Friction with the driving tower, however, should 38 not be so high that the lifting of the belt along the tower, :: ~
~3~3~
1 which requires vertical sliding along the tower's bars, is 2 interfered with significantly.
3 Another embodiment of the invention, which can be 4 combined with either or both of the above embodiments, includes raised outer plates on one or preferably both sides 6 of the belt. The raised plates ~eep products from falling 7 off the belt or running into the cage.
8 It is therefore among the objects of the present 9 invention to improve over prior low tension spiral conveyor belt systems with driving towers or drums, by incorporating 11 in such a system a substantially all plastic conveyor which 12 is free of rod heads or other protrusions on the belt's edge 13 at the inside of the curve where the belt progresses 14 helically around the drum. These and other objects, advantages and features of the invention will be apparent 16 from the following description of a preferred embodiment, 17 considered along with the accompanying drawings.
19 Description of the Drawings Figure 1 is a perspective view generally illustrating a 21 low tension spiral conveyor belt system in accordance with 22 the invention.
23 Figure lA is a schematic elevational view of the system 24 shown in Figure 1.
Figure 2 is a plan view showing details of construction 26 of a plastic conveyor belt incorporated in the system 27 illustrated in Figure 1.
28 Figure 3 is a plan view showing another embodiment 29 wherein each belt module has attached to it a separate, non-integral end plate.
31 Figure 4 is a partial plan view showing the belt curving 32 around a driving tower or drum of the low tension system, 33 illustrating the contact between the driving tower and the 34 edges of the conveyor belt, and including a variation of the construction shown in Figure 3.
36 Figure 5 and 6 are plan and side elevation views showing 37 another modification of the plastic conveyor belt.
, .
~, .
, ~2~
1 Description_of Preferred Embodiments 2 In the drawings, Figures 1 and lA show a low tension 3 conveyor belt system 10 in accordance with the principles of 4 the invention. The system 10 includes a plastic conveyor belt 12, preferably with all plastic or substantially a~l 6 plastic components~ a take-up belt drive or sprocket drive 7 which may be at a sprocket 14 driven by a motor (not 8 specifically shown), additional feed sprockets 15, 16 and 17, 9 a take-up sprocket 18, and additional sprockets 20 and 22, all defining a path through which the conveyor belt 12 is 11 fed. The system includes a helical wearstrip belt support or 12 ramp 24 and a driving tower or cage or drum 26 about which 13 the wearstrip ramp is positioned and against which the belt 14 12 engages at its inside edge as it travels helically around the drum 26.
16 As is known in the prior art, the driving cage 26 is 17 intended to drive the conveyor belt (which has generally been 18 a steel conveyor in the prior art) by engaging against the 19 inner edge of the belt with vertical bars or spindles 28 or other exterior drum structure, thereby providing driving 21 force to tha belt at many points (or substantially 22 continuously) along its movement and accordingly greatly 23 reducing tension in the belt as compared to a belt driven 24 from a single location.
The driving cage, as in prior systems, is rotated at a 26 speed slightly higher than that of the moving belt 12, 27 providing a positive driving assistance to the belt, and a 28 constant slipping of the driving cage over the edge surfaces 29 of the belt occurs. This is an "overdrive" condition. There must be sufficient overdrive to lift the belt and load along 31 the inclined ramp 24 while also moving it generally 32 horizontally. The take-up drive 14 acts as an assist and 33 tension drive, and moves the belt only horizontally in 34 relation to the cage.
However, in prior systems having a driving cage or drum 36 for belt driving and lowering of tension, there has been 37 present a series of protrusions at the edge surfaces of the 38 belt enga~ing the driving drum. Primarily these have ' 2 ~
1 comprised heads or ends on connecting rods which secure 2 successive belt modules together. Although such systems have 3 functioned satisfactorily, they have produced excessive wear 4 on the protrusions, such as the rod head, and distortion of the belt as well as the sur4ace of the driving drum itself 6 (occasionally the vertical bars of the driving cage have been 7 of plastic to reduce this wear problem). The protrusions 8 have also interfered with the smooth engagement of the belt 9 by the driving drum, reducing the effective frictional engagement between the belt edges and the surfaces of ~he 11 driving drum. This has resulted in reduced efficiency of the 12 low tension system and in relatively severe variations in the 13 degree of tension of the belt and surges of the belt as it 14 passed around the drum.
In the system of the present invention, these problems 16 are eliminated by the use of the plastic conveyor belt 12 in 17 the structure as illustrated particularly in Figures 2, 3 and 18 4. As shown, plastic connecting rods 32 which serve to 19 connect adjacent belt modules 34 have heads 36 on each end which are protected from interference or engagement with 21 driving surfaces of the driving drum 26. The rods 32 connect 22 interdigited projections 38 of each belt module as depicted 23 in the drawing. Their heads 36 lie in recesses 40 formed in 24 end members 42 of the belt modules. The recesses 40 comprise enlarged bores on the axis of smaller bores 44 which extend 26 through the end members and all pro~ections of the 27 interdigited structure.
28 As illustrated in Figure 2, the rod heads 36 do not 29 protrude beyond the outer surface of the end members 42 of the belt modules. As discussed above, this avoids excessive 31 wear of the belt module, of the rod and of the driving cage 32 as the belt is "overdriven" by the cage.
33 Figure 3 shows a portion of the belt 12, i.e. several 34 modules 34 connected by rods 32 which are also preferably of plastic. In this embodiment, the end members of the modules 36 34 comprise separate plates 46, non-integral with the body of 37 the module 34. The cage engaging plates 46 have bores 48 and 38 recesses 50, as in the end members 42 discussed above and ::
~3~
1 shown in Figure 2. The use of separate plates enables the 2 cage-engaging members to be of a higher-friction material 3 than the body of the module 34. This is important in 4 controlling the friction between the driving drum or cage and the belt in rela~ion ~o the force required to lift the belt, 6 and it enables minimizing friction (with a different plastic 7 material) between the belt's lower surface and the wearstrip 8 24 on which it slides.
9 Figure 4 shows a portion of a belt 12a which is traveling in an arcuate path around the driving cage 26. In 11 the belt 12a, end plates 46a are slightly modified, arcuately 12 (concavely) shaped for a more complementary engagement 13 against the driving drum. An outer cage-engaging surface 52 14 of each end plate 46a is concave, with a radius generally matched to that of the driving drum or cage 26. This can 16 help promote still smoother frictional driving of the belt by 17 the drum.
18 Figures 5 and 6 show a further variation which can be 19 used in combination with what is shown in Figures 3 and 4.
In this embodiment the separate plates 46a are raised, 21 extending substantially higher than the top surface of the 22 belt 12a, to provide barriers at both left and right for 23 retention of product on the belt. In many uses of such 24 belts, products are loaded quite densely on the belt, and there often is low friction between the belt and the bottom 26 of the product. Thus, items can tend to slide o~f the belt 27 or into the driving cage, on a belt without edge barriers.
28 In the present invention the barriers are integral with the 29 separate end member plates 46a of each belt module, thus enabling the plate to cooperate in providing a higher 31 friction driving surface (as discussed above) while also 32 functioning to hold product on the belt.
34 I CLAIM:
~' ,
Claims (5)
1. A low tension conveyor belt system with a plastic conveyor belt, comprising, a driving tower or drum on a substantially vertical axis, with a wearstrip belt support platform arranged in a helical path around the driving tower, an endless plastic conveyor belt positioned on a wearstrip belt support and extending tangentially off the wearstrip belt support and away from the driving tower, with means separate from the driving tower for engaging and the driving belt and feeding it in a return path back to the driving tower and onto the wearstrip belt support at an opposite axial end of the driving tower from the position at which the belt exited the driving tower, and said plastic conveyor belt being assembled from a series of plastic belt modules each having end members at its ends, and the adjacent belt modules being interconnected by rods passing through openings in the modules in interdigited projections of the adjacent modules, said end members having a substantially smooth surface which engages against the exterior surfaces of the driving tower, whereby the plastic conveyor belt operates smoothly around the driving tower, without snagging and without excessive wear of exposed components on the edge of the belt engaged by the driving tower.
2. The plastic conveyor belt system of claim 1, wherein the end members of the belt modules, at least on said one side of the belt, are slightly concavely curved, generally with a curvature conforming to that of the exterior of the driving tower.
3. The plastic conveyor belt system of claim 1, wherein the end members of the belt modules comprise end plates of a different, higher-friction plastic material than that of the remainder of the module.
4. The plastic conveyor belt of claim 3, wherein the end plates are raised, extending substantially above the upper surface of the belt, for providing a barrier to prevent products from sliding off the edge of the belt.
5. The plastic conveyor belt of claim 1, wherein at least one of the end members on each belt module has a recess receiving a head at one end of the rod passing through the module, so that at least on one side of the belt, which engages against the driving tower, rod heads are recessed in said substantially smooth surface.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000614315A CA1312301C (en) | 1989-09-28 | 1989-09-28 | Low tension plastic conveyor belt system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000614315A CA1312301C (en) | 1989-09-28 | 1989-09-28 | Low tension plastic conveyor belt system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1312301C true CA1312301C (en) | 1993-01-05 |
Family
ID=4140777
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000614315A Expired - Lifetime CA1312301C (en) | 1989-09-28 | 1989-09-28 | Low tension plastic conveyor belt system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1312301C (en) |
-
1989
- 1989-09-28 CA CA000614315A patent/CA1312301C/en not_active Expired - Lifetime
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