Method of making positive drive conveyor belt

Abstract

A manufacturing process converts a standard flat belt conveyor belt into a new, positively driven, pitch differential belt. A strip of thermoplastic material having a physical characteristic, such as melting temperature, that differs from the physical characteristic of the thermoplastic material comprising the conveyor belt, is applied to the drive side of a commercially available conveyor belt and machined to create a plurality of teeth, or drive bars, of any desired geometry that is configured to engage with the with sprockets or drums of the drive mechanism on the conveyor. The strip and/or drive bars can also be made by additive manufacturing, such as by 3D printing. Two ends of the resulting belt segment are cut to length and spliced, preferably with finger joints, to make a continuous loop using an industry standard hot-plate vulcanizer with a custom fitting called an alignment mold. The melting temperature of the belt and the strip/teeth are chosen to be far enough apart so that the belt may be spliced without melting the teeth. The alignment mold is a silicon pad that has recesses shaped to conform to the geometry/pitch of teeth so that the teeth retain their integrity and shape during the splicing process.

Claims

1. A method of making an endless positively driven, pitch differential conveyor belt of the type used in a conveyor wherein an endless conveyor belt has drive bars or teeth on the inner drive surface of the conveyor belt that are configured to engage with drive elements of the conveyor such as grooves in a drive sprocket, the method comprising the steps of: cutting a conveyor belt having an outer surface and an inner drive surface to length to form a belt segment having two ends, the conveyor belt being formed from a first polymeric material; forming at least one drive bar mounted to the inner drive surface of the conveyor belt, the at least one drive bar being formed from a second polymeric material having a melting temperature that is at least about 15 C. higher than the first polymeric material; cutting the two ends of the belt segment to have fingers that are configured to intermesh with each other; placing the two ends of the belt segment together so that the fingers intermesh on a standard hot-plate vulcanizer that has been fitted with an alignment mold to contact the inner drive surface of the conveyor belt, the alignment mold having a plurality of recesses shaped to conform to the geometry and pitch of the at least one drive bar on the belt segments so that the at least one drive bar is received in a recess of the alignment mold; heating the two ends of the belt segment to a temperature greater than the melting temperature of the first polymeric material and less than the melting temperature of the second polymeric material while the alignment mold cradles the at least one drive bar to maintain its geometry and pitch; and cooling the two ends to form an endless conveyor belt.

2. The method of claim 1 wherein the alignment mold comprises a silicon pad that is substantially the inverse of the inner drive surface of the belt bearing the at least one drive bar so as to have a plurality of recesses.

3. The method of claim 1 wherein the geometry of the fingers is varied across the width of the belt.

4. The method of claim 3 wherein the geometry of the fingers varies from large to small and back to large so that the fingers are smaller in the vicinity of the at least one drive bar while retaining the same aspect ratio of length to width.

5. The method of claim 4 wherein the length of the fingers range from about 0 to 5 inches.

6. The method of claim 1 wherein the melting temperature of the first polymeric material is between 20 C. and 40 C. lower than the second polymeric material.

7. The method of claim 1 wherein the first polymeric material has a physical characteristic which is different from a physical characteristic of the second polymeric material.

8. The method of claim 7 wherein the physical characteristic is hardness and the first polymeric material has a higher hardness value than the second polymeric material.

9. The method of claim 7 wherein the physical characteristic is coefficient of friction and the first polymeric material has a higher coefficient of friction than the second polymeric material so that the outer surface has a higher coefficient of friction than the inner drive surface.

10. The method of claim 1 wherein the first polymeric material is a thermoplastic material.

11. The method of claim 10 wherein the second polymeric material is a thermoplastic material.

12. The method of claim 1 wherein the step of forming the at least one drive bar comprises securing the first side of at least one strip of the second polymeric material to the drive surface of the conveyor belt by adhesive, heat welding or solvent welding.

13. The method of claim 12 wherein the step of forming further comprises configuring the second side of the at least one strip of the second polymeric material to form teeth for engagement with a drive element of the conveyor by machining.

14. The method of claim 1 wherein the step of forming the at least one drive bar comprises applying at least one strip of the second polymeric material to the drive surface of the conveyor belt by additive manufacturing.

15. The method of claim 14 wherein the step of forming the at least one drive bar includes configuring teeth on the second side of the at least one strip of the second polymeric material for engagement with a drive element of the conveyor.

16. The method of claim 14 wherein the additive manufacturing is 3D printing.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) Comprehension of the invention is facilitated by reading the following detailed description, in conjunction with the annexed drawing, in which:

(2) FIG. 1 is a perspective side view of an endless conveyor belt of the type used in positive drive arrangements wherein teeth on the underside, or inner surface, of a conveyor belt engage with sprockets;

(3) FIG. 2 is a perspective view of the inner, or drive, surface of a segment of and endless conveyor belt of the type shown in FIG. 1;

(4) FIG. 3 is an enlarged view of an individual tooth as viewed from arrow III on FIG. 2;

(5) FIG. 4 is an enlarged perspective view of an endless conveyor belt manufactured in accordance with the method of the present invention; and

(6) FIG. 5 is a perspective view of an alignment pad used to maintain pitch alignment during endlessing of a conveyor belt in accordance with the method of the present invention.

DETAILED DESCRIPTION

(7) FIG. 1 shows a conveyor belt 10 in a typical positive drive installation. In this case, conveyor belt 10 is an endless loop installed around two sprockets 12 and 14. The sprockets are conventional and can be of any size and configuration. Each sprocket 12, 14 has a number of transverse notches or grooves 16 spaced around its circumference. The sprockets 12, 14 can have any number of grooves 16, which may, in some embodiments, depend on the configuration of conveyor belt 10.

(8) Conveyor belt 10, as shown in FIG. 1, has a plurality of teeth 18 spaced from each other on an inner surface 20 of conveyor belt 10. Inner surface 20 is the underside, or drive side of conveyor belt 10. The plurality of teeth 18 are configured to engage with grooves 16 of each sprocket 12, 14. At least one sprocket, illustratively sprocket 12, is a drive sprocket, while the other sprocket 14 may be an idler or slave sprocket. It is to be understood, however, that in any given installation there may be a plurality of sprockets for a single endless belt, at least one of which is a drive sprocket. Referring to FIG. 1, conveyor belt 10 travels in the direction of arrow 24 during operation.

(9) The upper span 26 of conveyor belt 10 provides a carrying, or support, surface for the transport of items. Conveyor belt 10, therefore, has an outer surface 22 that is in contact with the goods being transported by the conveyor and an opposing inner surface 20. Outer surface 22 can be fairly smooth and free of discontinuities. In the alternative, outer surface 22 can be textured, or may have cleats, sidewalls, or other accessories not illustrated in FIG. 1, but known to those of skill in the art, depending on how conveyor belt 10 is to be used.

(10) FIG. 2 illustrates a conveyor belt segment 110 according to an aspect of the disclosure herein. Conveyor belt segment 110 of FIG. 2 is substantially similar to a portion of the conveyor belt 10 shown in FIG. 1. Therefore, like parts will be identified with like numerals increased by 100. It should be understood that the description of the like parts of conveyor belt 10 applies to conveyor belt segment 110 unless otherwise noted.

(11) Conveyor belt segment 110 is shown with the drive side, or inner surface 120, facing upwards. The conveyor belt segment 110, as shown in FIG. 2, has two main parts, a belt 130, which as discussed above, can be supplied by any manufacturer, and teeth 118 on the inner surface 120 of belt 130 that are configured to engage with a drive sprocket (not shown in this figure).

(12) In a preferred embodiment, as shown in FIG. 2, teeth 118 comprises a plurality of teeth spaced equidistant from each other on strips 132 that run across the width of belt segment 110. Of course, the teeth can be spaced apart in any manner provided that the teeth are configured to engage with the sprockets used in the implementation. Belt 130 has an inner surface 134 defining at least a portion of the drive side, or inner surface 120, of conveyor belt segment 110 and an outer surface 122 that is in contact with the goods being transported on the upper span 126 of conveyor belt segment 110.

(13) In accordance with the invention, belt 130 is formed of at least a first thermoplastic or thermoset material 136, which by way of a non-limiting example, is a urethane-based material. In a specific illustrative example, the first thermoplastic material is a polyvinyl chloride and urethane-based material. Other thermoplastic materials such as Pebax resin, polyester or polyurethane, or any combination of thermoplastic materials or flexible thermoset materials, including rubbers, are contemplated in the practice of the invention.

(14) The strip 132 of teeth 118 is mounted to belt 130 on inner surface 134. Strip 132 has a first side 137 (see, FIG. 3) in contact with the inner surface 134 of belt 130 and a second side 138 opposite to first side 137 that defines another portion of the drive side, or inner surface 120 of the conveyor belt segment 110. A plurality of teeth 118 extend from the second side 138. The strip may be mounted to the belt in any manner known to a person of skill in the art such as by the heating, gluing, or solvent welding. In a preferred method embodiment, an adhesive combined with a solvent is applied to the underside 137 of strip 132 which is then contacted with the belt surface 134. Heat is then applied to encourage the solvent to melt strip 132 to the belt. As illustrative examples, solvents such as cyclohexanone, toluene, acetone, tetrahydrofuran (THF) or methyl ethyl ketone (MEK) work well with polyurethanes.

(15) Multiple strips, such as strip 132, each having a plurality of teeth 118, are typically attached to the inner surface 134 of belt 130. It should be understood that any number of strips 132 including only one can be mounted to the belt 130. By way of non-limiting example, four strips 132 are show in FIG. 2. Strip 132, including a plurality of teeth 118, is formed from a second thermoplastic or thermoset material 140. The second thermoplastic or thermoset material 140 can be, by way of non-limiting example, a urethane-based material. Other thermoplastic material possibilities include Pebax resin, polyester or polyurethane, or any combination of thermoplastic or thermoset materials. However, the first and second thermoplastic or thermoset materials are chosen to have different physical characteristics as will be described hereinbelow.

(16) Melting temperature is a preferred physical characteristic that dictates the selection of the first and second thermoplastics 136, 140. For example, the second thermoplastic material 140 has a higher melting temperature (T2) than the first thermoplastic material 136 comprising the belt. The melting temperature (T1) of the first thermoplastic material 136 is illustratively between 20 C. and 40 C. lower than the second thermoplastic material 140. In a specific preferred example, the second thermoplastic material 140 has a melting temperature (T2) that is at least about 15 C. higher than the first thermoplastic material 136.

(17) Another differing physical characteristic is the hardness value. The second thermoplastic material 140 can have a higher hardness value than the first thermoplastic material 136. In other words, in this embodiment, the first thermoplastic material 136 is more flexible than the second thermoplastic material 140.

(18) Yet another differing physical characteristic is the coefficient of friction for each of the surfaces defined by the first and second thermoplastics 136, 140. In a preferred embodiment, the first thermoplastic material 136, defining the outer surface 122 of the belt, has a higher coefficient of friction than the inner surface 134 of the belt to assist in gripping.

(19) In a specific illustrative example, the first thermoplastic material 136 includes a fabric material 142 as a reinforcement in belt. The fabric material 142 can be, by way of non-limiting example, a polyester. The second thermoplastic material 140, which in some embodiments, defines the strip 132 with the second side 138 having a lower coefficient of friction than the outer surface 122. In other words, the inner surface 120 has an overall higher coefficient of friction than the outer surface 122 of the conveyor belt segment 110. It is further contemplated that the outer surface has a higher coefficient of friction than the first and second thermoplastic materials 136, 140. In other words, the outer surface 122 can include the fabric material 142 (FIG. 4) and have the highest coefficient of friction for the conveyor belt 110 ensuring a gripping surface.

(20) FIG. 3 is an enlarged view of an individual tooth 118 of the plurality of teeth 118 as viewed from arrow III on FIG. 2. This figure shows more clearly that the first side 137 of the strip 132 is mounted to the inner surface 134 of belt 130. Each tooth of the plurality of teeth 118 has a height (H) measured perpendicular to the inner surface 134 of the belt and a thickness (t) measured parallel to the inner surface 34 of the belt. The height (H) and thickness (t) can vary depending on the implementation for the conveyor belt segment 110. In one embodiment, the strip 132 and the plurality of teeth 118 are one unit integrally formed from the second thermoplastic material 140. In another embodiment, there is no strip and each individual tooth in the plurality of teeth 118 is formed from the second thermoplastic material 140 and attached directly to the inner surface 134 of belt 130.

(21) FIG. 4 is an enlarged perspective view of an endless conveyor belt 130. The set of teeth 118 can extend to any width, including the entire extent of the width of the endless belt 130 (not clearly shown in this figure). In order to fabricate an endless belt, the two ends of a belt segment of the appropriate length must be joined together to form the endless loop. Referring to FIG. 4, belt 130 has a first end 144 and a second end 146. Instead of abutting two straight edges at ends 144, 146, it is advantageous to use a finger splice. This means that the first end 144 includes a first set of fingers 148 and the second end 146 includes a second set of fingers 150 that interlock. The fingers may be cut in any manner known in the practice of the art, illustratively the fingers are cut with a die by a hydraulic press punch or by computer numerical control (CNC) machine.

(22) The first and second sets of fingers 148, 150 mirror each other such that the second set of fingers 150 is received in the first set of fingers 148 when the ends of belt 130 are joined. Each of the first and second sets of fingers 148, 150 can have a varying lengths (l) and widths (w) as illustrated in FIG. 4. The length (l) can range from of equal to, or between 0 and 5 inches, and the width (w) can range from of equal to, or between 0 and 1 inch, in a typical arrangement. The varying lengths (l) and width (w) enable a strong splice during manufacturing when the first end 144 is spliced with the second end 146 to define an endless conveyor belt 152.

(23) Of course, the range of lengths and widths of the fingers can vary as is known to those of skill in the art. Moreover, the geometry of the fingers can vary. However, the pointed configuration shown in FIG. 4 is preferred. In a specific illustrative embodiment, the length (l) ranges from between 0 and 5 inches and the width (w) ranges from between 0 and 2 inches. In a particularly preferred embodiment, the lengths and/or widths of the fingers are greater in the vicinity of the belt where there are no teeth (see, FIG. 2, inner surface 134) and reduced in the vicinity of the belt where there are teeth (see, FIG. 2, strips 132) to fit within the pitch.

(24) In a specific illustrative embodiment, the two ends 144, 146 are abutted so that the fingers 146, 148 intermesh in a standard hot-plate vulcanizer that is fitted with an alignment pad 160 as shown in FIG. 5 to ensure that teeth retain the proper pitch during the vulcanization process. It is known to use silicone pads in a vulcanizer to maintain the texture of the belt, particularly on the top surface, so that when the belt polymer becomes molten the surface texture can be customized to the customer's specifications. In accordance with the present invention, an alignment pad 160 is used on the bottom or drive surface of the belt during vulcanization to maintain the pitch of the teeth when the belt is melted to bond the ends.

(25) Referring to FIG. 5, alignment pad 160, which preferably includes a block 166 of silicone, including at least one recess 164 which is configured to hold an individual tooth of the plurality of teeth 118 during the vulcanization process to splice the ends of the belt together. Recesses 164 are molded into the silicone or machined to conform to the geometry/pitch of teeth 118. As described herein, the plurality of teeth 118 can be part of a strip 132 illustrated in dashed lines on FIG. 5 (and as shown clearly in FIG. 2).

(26) While the foregoing has been directed to laterally-oriented teeth, the manufacturing techniques of the present invention can be used to apply longitudinally-oriented features, or attachments, such as cleats or flights, that would be useful for containment to guide the belt along a desired path. These longitudinally-oriented features could be placed on the belt along the edges of the rows of teeth or centered within the row. The fabrication processes of the present invention enables the ability to make containment geometries, which can be negative or positive, of any desired shape and size and to locate them wherever desired.

(27) As a specific example, a longitudinally-oriented feature can be made by reducing the height/removing the center of the row in order to capture a rail within the opening. Likewise, the outer edges of the row could be configured to be captured between two rails of the conveyor. In another example, the edges of the belt could contain an interlocking geometry that would allow positive engagement with the containment device. Such devices could be multi-purposed, that is, comprising support rails, sprockets, and frame members; or they could be dedicated instruments for the specific purpose of containment.

(28) Although the invention has been described in terms of specific embodiments and applications, persons skilled in the art can, in light of this teaching, generate additional embodiments without exceeding the scope or departing from the spirit of the invention herein described. Accordingly, it is to be understood that the drawing and description in this disclosure are proffered to facilitate comprehension of the invention, and should not be construed to limit the scope thereof. Moreover, the technical effects and technical problems in the specification are exemplary and are not limiting. The embodiments described in the specification may have other technical effects and can solve other technical problems.