Tracking-guide bonder and method for bonding tracking guides to thermoplastic belts

Abstract

A bonder and a method for bonding linear tracking guides to a thermoplastic belt at a splice joint. A heater assembly with two heater halves receives a tracking guide in a trapezoidal channel formed between the two halves. Heat is applied to heater blocks in each heater half to melt a portion of the base of the tracking guide and the abutting outer surface of the belt to bond the tracking guide to the belt.

Description

[0001] TRACKING-GUIDE BONDER AND METHOD FOR BONDING TRACKING GUIDES TO THERMOPLASTIC BELTS

[0002] BACKGROUND

[0003] The invention relates to bonding tools and a method for bonding tracking guides to a thermoplastic belt.

[0004] Splicing presses are used to weld the butt ends of two thermoplastic conveyor belt sections together. Conventional presses include a pair of clamps, each of which holds one of the two belt sections. The clamps, which extend across the entire width of the belt sections, firmly hold the sections with the butt ends facing each other across a gap. A heating wand is moved into the gap, and the two clamps close until the butt ends of the belt sections contact opposite sides of the heating wand. As soon as the butt ends are softened or melted sufficiently by the wand's heat, the clamps are retracted so that the wand may be removed. Then the clamps are moved toward each other until the softened or melted butt ends meet. The clamps hold the butt ends together as the joint at their interface cools.

[0005] Tracking guides are raised ribs that run linearly along the length of the conveying surface of a conveyor belt at each side edge. Typically, a tracking guide has tapered sides forming a trapezoidal cross section. Its wider base is attached to the belt's conveying surface. Because the trapezoidal shape of the tracking guides is an inverted truncated V, the guides are often called V-guides. Complementary guide structure affixed to the conveyor frame receives the V-guides and prevents the belt from wandering laterally. In other words the V- guides and cooperating guide structure track the belt. One common form of guide structure is a pulley with a sheave shaped to receive the V-guide.

[0006] When a V-guide is damaged, the damaged section of V-guide has to be replaced. When a belt with a V-guide is spliced, the V-guide must also be spliced and reattached to the belt. The process of replacing a V-guide section or splicing a V-guide is a labor-intensive sequence of operations entailing the use of sharp knives, heat guns, sanders, soldering irons, and blowers or vacuums.

[0007] SUMMARY

[0008] One version of a bonder for bonding a tracking guide to a thermoplastic belt comprises a base and a heater assembly. The base has a top face configured to receive a length of a thermoplastic belt that has a linear tracking guide. An unbonded length of the tracking guide is unbonded to the thermoplastic belt's outer surface. The heater assembly is above the base and includes a channel that extends in length from a first end to a second end of the heater assembly and first and second heater blocks that form a bottom portion of first and second sides of the channel. The channel is complementary in shape to the linear tracking guide to mate with the guide's unbonded length. The first and second heater blocks apply heat to melt the bottom of the unbonded length of the tracking guide at the first and second sides of the channel to bond the unbonded length of the tracking guide to the outer surface of the thermoplastic belt.

[0009] A method for bonding a tracking guide to an outer surface of a thermoplastic belt comprises: (a) registering the bottom of a portion of a thermoplastic belt in the base of a bonding fixture; (b) positioning a first heater half against a first side of an unbonded portion of a tracking guide extending linearly along a length of the thermoplastic belt;

[0010] (c) positioning a second heater half against an opposite second side of the unbonded portion of the tracking guide; (d) drawing the first and second heater halves together to form a channel between a first heater block in the first heater half and a second heater block in the second heater half, wherein the channel is sized and shaped to receive the unbonded tracking guide; (e) tightening the first and second heater halves against the first and second sides of the unbonded portion of the tracking guide; (f) applying downward pressure against the first and second heater blocks to press the first and second heater blocks against the outer surface of the thermoplastic belt at the bottom of the tracking guide at the first and second sides; and (g) heating the first and second heater blocks to melt the bottom of the tracking guide at the first and second sides to bond the tracking guide to the outer surface of the thermoplastic belt.

[0011] BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 is an isometric view of a tracking-guide bonder embodying features of the invention.

[0013] FIG. 2 is an isometric view as in FIG. 1, but with the heater assembly and the conveyor belt to be bonded shown separated for clarity.

[0014] FIG. 3 is an exploded view of the heater assembly of FIG. 1. FIGS. 4A and 4B are top and bottom isometric views of the heater assembly of FIG. 1 with the heater halved separated.

[0015] FIG. 5 is a bottom isometric view of the heater assembly of FIG. 1

[0016] DETAILED DESCRIPTION

[0017] A tracking-guide bonder bonding a section of a V-guide to a thermoplastic conveyor belt is shown in FIG. 1. The bonder 10 is shown bonding a length of a tracking guide— a V- guide 12— to the outer surface 14 of a thermoplastic conveyor belt 16 in the vicinity of a splice joint 18. The V-guide 12 is a raised rib that extends linearly along the length of the belt 16 indented slightly inward of the belt's side edge 20. But the V-guides could alternatively be positioned anywhere across the belt's width. The belt 16 shown in this example is a homogeneous, positively driven conveyor belt made of a thermoplastic material, such as polyurethane, with periodically spaced drive bars 22 on the inner side 24, of the belt.

[0018] The bonder 10 includes a heater assembly 26 and a fixture 28. The fixture 28 has a top deck 30 connected to a parallel lower base 32 by a pair of side frames 34, 35. Grooves 36 in the top face of the base 32 are sized to receive the belt's drive bars 22 to maintain the belt 16 in registration with the bonder 10. A threaded push rod 38 with an adjustment knob 40 extends through a quick-release nut 42 and the top deck 30 to a pressure plate 44. The end of the push rod 38 opposite the adjustment knob 40 has a pad 46 that pushes against the pressure plate 44 when the push rod is extended.

[0019] FIG. 2 shows a few more details of the bonder 10 with the heater assembly 26 and the belt 16 separated from the fixture 28 for clarity. A brass, bronze, or aluminum metal bedplate 48 is surrounded by an insulating PTFE (Teflon®) or nylon liner 50. Both the liner 50 and the bedplate 48 form a continuation of the top face, including the grooves 36 in the fixture's base 32. The bedplate 48 applies heat to the bottom of the belt 16 to aid the bonding process.

[0020] The bonding of the V-guide 12 proceeds as follows. First, two butt ends of the belt 16 are spliced together at a splice joint 18 in a separate operation, in which extended loose ends 52, 53 of the V-guide 12 on the two belt butt ends are separated from the belt's outer surface 14. The two separated V-guide ends 52, 53 are cut and aligned to meet at a V-guide joint. The cut ends are then spliced together in the separate operation. The V-guide splice can be at the position of the belt's splice joint 18 or can be offset from it. After the ends of the V-guide have been tacked together, the outside edge 20 of the belt 16 with the V-guide splice is inserted in the fixture 28. (In FIG. 2 the belt 16 is flipped from the orientation it would be in for insertion into the fixture 28, i.e., with the V-guide belt edge deeper into the fixture.) The belt's drive bars are registered in the grooves 36 in the top face of the base 32. The belt 16 is positioned with its V-guide 12 sitting above the conductive bedplate 48. In reference to FIGS. 2 and 4B, a first heater half 54 is inserted into the fixture 28 against one side of the V-guide 12. Then a second heater half 55 is inserted into the fixture against the other side of the V-guide 12. Thumbscrews 72 are turned to draw the heater halves 54, 55 toward each other to tighten the heater halves against the V-guide 12. The push rod 38 is tightened against the pressure plate 44, which, in turn, tightens the heater assembly 26 around the V-guide 12. The heater assembly heats the base of the V-guide and the outer surface 14 of the belt 16 to bond the V-guide to the belt. After the V-guide 12 is bonded to the belt 16, the push rod 38 is lifted out of contact with the pressure plate 44, and the pressure plate is removed from the top of the heater assembly 26. Then the thumbscrews 72 are unscrewed to separate the heater halves 54, 55 from the V-guide 12. The belt 16 with the bonded V-guide 12 is then removed from the fixture 28.

[0021] Details of the heater assembly 26 are shown in FIG. 3. The left and right heater halves 54, 55 are almost identical. Each heater half 54, 55 has an aluminum heater block made of two heater-block halves 56, 57. Cavities 58 in confronting faces of the heater-block halves 56, 57 form a mounting cavity receiving a thermocouple and associated wires (not shown). The thermocouple measures the temperature of the heater block. The bottom of the inner heater-block half 56 extends down slightly lower than the outer heater-block half 57. A lower salient portion 60 is a heat applicator that contacts the V-guide and the adjoining outer surface of the belt to bond the V-guide in place on the belt's outer surface. A PTFE (Teflon®) tape over the applicator prevents melted plastic from flowing into the heater assembly 26 and also helps make a smoother weld line.

[0022] The heater-block halves 56, 57 in each heater half 54, 55 are sandwiched between inner and outer insulation blocks 62, 63. The heater-block halves 56, 57 reside in recesses 64, 65 in lower portions of the insulation blocks 62, 63. Screws 66 through aligned holes in the inner insulation block 62 and the heater-block halves 56, 57 are threaded into threaded inserts 68 in holes 70 in the outer insulation block 63 to hold each heater-block half 56, 57 together.

[0023] Two thumbscrews 72 extending through aligned holes in the right heater half 55 and through aligned holes in the left inner insulating block 62 and the left heater-block halves 56, 57 are threaded into threaded inserts 74 in holes 76 in the left outer insulating block 63. The thumbscrews 72 are used to close the two heater halves 54, 55 against the V-guide and to release them from the V-guide after bonding.

[0024] The heater assembly 26 has first and second endcaps 78, 79 at opposite ends. The first endcap 78 is affixed by screws (not shown) to the left heater half 54, and the second endcap 79 is similarly affixed to the right heater half 55. Dowels 81 align the endcaps 78, 79 with holes 83 in the heater halves 54, 55. Like the insulating blocks 62, 63, the endcaps 78, 79 are made of an insulating material. Each endcap 78, 79 has a channel 80 in its face 82 facing the heater halves 54, 55. The channel 80 is in communication with an inlet 84 into which an air fitting 86 is installed. An air hose (not shown) connected to the fittings 86 forces air through the channel 80 to cool the heater assembly 26 and the V-guide after bonding. A thermal fuse 88 in each endcap 78, 79 opens the heating circuit for the heater blocks if the temperature exceeds a maximum allowable temperature.

[0025] Wiring (not shown) to the heater-block halves 56, 57, the thermal fuses 88, and the thermocouples runs through openings 90, 91 in the endcaps 78, 79 from a wiring housing 92 attached to the endcaps by screws 94. A connector socket 96 attached to the wiring housing 92 receives a cable plug (not shown) with wires that power the heater-block halves 56, 57 and that send thermocouple signals to an external controller (not shown) that controls the heating power and the heating time.

[0026] FIGS. 4A and 4B show the heater assembly 26 with the two heater halves 54, 55 separated along with the pressure plate 44. As better shown in FIG. 4B, the bottoms of the endcaps 78, 79 have two legs 98, 99 spaced apart across a trapezoidal gap 100 with angled walls that diverge toward the bottom ends of the legs. The gaps 100 are sized and shaped to receive the V-guide. One of the legs 99 of each of the endcaps 78, 79 is continuous with the bottom of the outer insulation block 63. As shown in FIG. 5, the undersides of the heater halves 54, 55, when drawn together by the thumbscrews 72, form a trapezoidal channel 102 continuous with the gaps 100 in the bottoms of the endcaps 78, 79. As shown in FIGS. 4A and 4B, the bottom ends of the heater block halves 56, 57 form a portion of each side of the channel 102 to heat the base of the V-guide and the outer surface of the belt.

Claims

What is claimed is: A bonder for bonding a tracking guide to a thermoplastic belt, comprising: a base having a top face configured to receive a length of a thermoplastic belt having a linear tracking guide with an unbonded length unbonded to the thermoplastic belt's outer surface; a heater assembly above the base and including: a channel extending in length from a first end to a second end of the heater assembly; and first and second heater blocks forming a bottom portion of first and second sides of the channel; wherein the channel is complementary in shape to the linear tracking guide to mate with the unbonded length of the tracking guide; wherein the first and second heater blocks apply heat to melt the bottom of the unbonded length of the tracking guide at the first and second sides of the channel to bond the unbonded length of the tracking guide to the outer surface of the thermoplastic belt. The bonder as claimed in claim 1 wherein the channel is trapezoidal in shape. The bonder as claimed in claim 1 wherein the top face of the base includes grooves sized to receive drive bars on the thermoplastic belt to maintain the thermoplastic belt in registration with the bonder. The bonder as claimed in claim 1 wherein the base is part of a fixture that further includes a top deck and a pair of side frames connecting the top deck to the base. The bonder as claimed in claim 4 comprising a push rod extending through the top deck adjustable to push the heater assembly against the linear tracking guide so that the bottom of the unbonded length is bonded to the outer surface of the thermoplastic belt. The bonder as claimed in claim 1 wherein each of the first and second heater blocks includes two heater-block halves and inner and outer insulation blocks sandwiching the two heater-block halves together to form a heat applicator that contacts the unbonded length of the linear tracking guide and the outer surface of the thermoplastic belt to bond the unbonded length of the linear tracking guide to the outer surface.The bonder as claimed in claim 6 comprising a PTFE tape on the heat applicator to prevent melted plastic from flowing into the heater assembly. The bonder as claimed in claim 6 wherein the heater assembly includes a first insulating endcap at the first end of the heater assembly and a second insulating endcap at the second end of the heater assembly, wherein the first and second endcaps include gaps that form continuations of the channel in the heater assembly. The bonder as claimed in claim 8 further comprising a thermal fuse in each of the first and second endcaps that disconnects power to each of the first and second heater blocks when the temperature exceeds a maximum allowable temperature. The bonder as claimed in claim 1 wherein the base includes a metal bedplate surrounded by an insulating liner that together form a continuation of the top face and wherein the metal bedplate applies heat to the thermoplastic belt to aid the bonding of the linear tracking guide to the thermoplastic belt. The bonder as claimed in claim 10 wherein the metal bedplate is made of brass, bronze, or aluminum. The bonder as claimed in claim 1 wherein the first and second heater blocks are separable. A method for bonding a tracking guide to an outer surface of a thermoplastic belt, the method comprising: registering the bottom of a portion of a thermoplastic belt in the base of a bonding fixture; positioning a first heater half against a first side of an unbonded length of a tracking guide extending linearly along a length of the thermoplastic belt; positioning a second heater half against an opposite second side of the unbonded length of the tracking guide; drawing the first and second heater halves together to form a channel between a first heater block in the first heater half and a second heater block in the second heater half, wherein the channel is sized and shaped to receive the unbonded length of the tracking guide; tightening the first and second heater halves against the first and second sides of the unbonded portion of the unbonded length of the tracking guide;applying downward pressure against the first and second heater blocks to press the first and second heater blocks against the outer surface of the thermoplastic belt at the bottom of the unbonded length of the tracking guide at the first and second sides; heating the first and second heater blocks to melt the bottom of the unbonded length of the tracking guide at the first and second sides to bond the unbonded length of the tracking guide to the outer surface of the thermoplastic belt. The method as claimed in claim 13 comprising, before registering the bottom of a portion of a thermoplastic belt in the base of a bonding fixture: splicing two butt ends of the thermoplastic belt at a splice joint, both butt ends having a length of unbonded tracking guide and at least one of the butt ends includes an extended length of unbonded tracking guide; cutting and aligning the two lengths of unbonded tracking guide to meet at a trackingguide joint; splicing the two lengths of unbonded tracking guide at the tracking-guide joint.

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