GB2256181A

GB2256181A - Belt joint.

Info

Publication number: GB2256181A
Application number: GB9209816A
Authority: GB
Inventors: Peter Law
Original assignee: Courtaulds Aerospace Ltd
Current assignee: Courtaulds Aerospace Ltd
Priority date: 1991-05-07
Filing date: 1992-05-07
Publication date: 1992-12-02
Also published as: GB9109827D0; GB9209816D0; DE9206110U1

Abstract

A joint in conveyor belting (10) comprises an adhesive (18) bonding together first and second regions of reduced thickness forming, respectively, leading edge (16) and trailing edge (14) regions of the bolt, the first region being cut away on its side which is the underside (12) of the bolt in use and the second region being cut away on its side which is the uppermost surface (13) of the belt in use, the overlapped butt joint so formed being underlain by a backing strip (17) secured to the underside (12). <IMAGE>

Description

BELT JOINT This invention relates to a method of joining together ends of a length of conveyor belting and to a joint in a conveyor belt made by the method.

The present invention is mainly concerned with conveyor belts which comprise a reinforcement fabric, or substrate, usually made from a woven glass fibre fabric or a polyaramid fibre fabric which is coated on both sides with a fluoroplastic layer such as, for example, polytetrafluoroethylene (PTFE).

One of the requirements of belt joints is that the region where the belt is joined should be of similar thickness to the rest of the belt. Furthermore, the surface of the belt should ideally be smooth and have similar characteristics as the rest of the belt.

Many joints have been proposed in the past in an attempt to meet these requirements. Some such proposals have suggested removing the outer layers to expose the fabric reinforcement and interleaving additional fabrics or threads to form a patch which is then recoated with a fresh outer layer. Other proposals have used multi-layered fabrics as the reinforcement and have removed the outer layers to expose the reinforcement and then removed some of the threads of the different layers of the fabric over different longitudinal extents of the belt. In this way the two ends of the belt are effectively spliced together and a fresh outer coating reapplied to the exposed fabric. All of these earlier proposals are difficult to do at the workstation where the belt is used. Furthermore, they are very time consuming and often make joints of different thickness to the rest of the belt.

There is therefore a need for an improved belt joint made by a much simpler method of joining the ends of a length of conveyor belting.

An object of the present invention is to provide a join in a conveyor belt which is strong, does not add too much thickness to the belt in the region of the join, and presents a relatively smooth surface on the side of the conveyor belt which is in contact with the product to be conveyed by the belt.

According to one aspect of the present invention there is provided a method of joining a belt comprising the steps of producing a length of belt material with a first end that forms a leading edge of a joint when the belt is in use and a second end which forms a trailing edge of the joint when the belt is in use, cutting away that part of the underside surface of the first end to form a first region of reduced thickness of belt, cutting away that part of the outermost surface of the second end of the belt to form a second region of reduced thickness of belt, the combined thickness of the first and second regions of reduced thickness being no more than the thickness of the rest of the belt, forming the belt into an endless loop to bring a surface of each region of reduced thickness into mutual confrontation, and form an overlapping butt joint, applying an adhesive to one or both of the mutually confronting surfaces, bonding the mutually confronting surfaces together, and providing a backing strip of material on the underside of the belt in the vicinity of the joint.

According to a further aspect of the invention there is provided a belt joint comprising a length of belt material with a first end that forms a leading edge of a joint when the belt is in use and a second end which forms a trailing edge of the joint when the belt is in use, a part of the underside surface of the first end being cut away to form a first region of reduced thickness of belt, a part of the outermost surface of the second end of the belt being cut away to form a second region of reduced thickness of belt, the combined thickness of the first and second regions of reduced thickness being no more than the thickness of the rest of the belt, and the belt being formed into an endless loop to bring a surface of each region of reduced thickness into mutual confrontation, and form an overlapping butt joint, an adhesive having been applied to one or both of the mutually confronting surfaces to bond the mutually confronting surfaces together, a backing strip of material being further provided on the underside of the belt in the vicinity of the joint.

In a still further aspect of the present invention there is provided a belt having an overlapping butt joint formed in accordance with the method of the present invention.

The invention will now be described by way of an example with reference to the accompanying drawing, which shows a cross-sectional view through a belt joint constructed in accordance with the present invention.

Referring to the drawing, the belt 10 is made from a closed woven glass fibre fabric 11 overcoated on each side with a layer 12 of a fluoroplastic such as, for example, polytetrafluoroethylene (PTFE) to make a belt which is approximately 0.25 mm (0.010 inch) to 1.0 mm (0.040 inch) thick. In the drawing the uppermost surface 13 of the belt 10 is the surface on which a product or products is to be conveyed. In use the belt travels in the direction of arrow A.

The belt 10 is joined end to end to make an endless conveyor belt by forming a joint in the following way.

Firstly, the uppermost surface 13 of the belt on the trailing edge region 14 of the joint is ground away to about half of its thickness. Then the underside surface 15 of the belt is ground away to about half the thickness of the belt at the leading edge region 16 of the belt. The parts which are ground away are accurately ground so that when the two ends are put together, the total thickness of the overlap is approximately the same as the rest of the belt.

An adhesive, for example a hot melt adhesive, typically a thermoplastics fluoropolymer is applied to the confronting faces of the overlap and the two ends are brought together to form an overlapping butt joint. The adhesive is allowed to set or harden to effect bonding. A liquid dispersion such as for example, aqueous PTFE, is applied to the confronting surfaces 18 of the belt prior to effecting the bond between the two ends. The purpose of the liquid dispersion is to increase the bond strength of the joint.

A backing strip 17 made of a glass fibre fabric and/or a polyaramid fibre of typically 0.08 mm (0.003 inch) or 0.13 mm (0.005 inch) thickness is bonded to the underside surface of the belt. The backing strip is of the same width as the belt and extends for a length at least equal to the length of the overlap. Preferably, the backing strip is twice the length of the overlap and is symmetrically positioned relative to the overlap.

Preferably the backing strip is bonded to the belt by means of a layer of thermoplastics fluoropolymer such as that used to bond the overlapping portions.

The provision of a backing strip results in a slight increase in the thickness of the belt but the upper surface of the belt is still reasonably smooth with no leading edges or steps to snag and cause failure. We have found that joints with backing strips have a strength of around 70% of the rest of the belt material whereas the same joint without a backing strip has a strength of about 20% of the rest of the belt.

Claims

1. A method of joining a belt comprising the steps of producing a length of belt material with a first end that forms a leading edge of a joint when the belt is in use and a second end which forms a trailing edge of the joint when the belt is in use, cutting away that part of the underside surface of the first end to form a first region of reduced thickness of belt, cutting away that part of the outermost surface of the second end of the belt to form a second region of reduced thickness of belt, the combined thickness of the first and second regions of reduced thickness being no more than the thickness of the rest of the belt, forming the belt into an endless loop to bring a surface of each region of reduced thickness into mutual confrontation, and form an overlapping butt joint, applying an adhesive to one or both of the mutually confronting surfaces, bonding the mutually confronting surfaces together, and providing a backing strip of material on the underside of the belt in the vicinity of the joint.

2. A method as claimed in claim 1, in which the first and second regions of reduced thickness are of equal thickness.

3. A method as claimed in claim 1 or claim 2, in which the backing strip is twice the length of the overlap between first and second regions.

4. A method of joining together ends of a length of conveyor belting substantially as herein described with reference to the accompanying drawing.

5. A conveyor belt joint comprising a length of belt material with a first end that forms a leading edge of a joint when the belt is in use and a second end which forms a trailing edge of the joint when the belt is in use, a part of the underside surface of the first end being cut away to form a first region of reduced thickness of belt, a part of the outermost surface of the second end of the belt being cut away to form a second region of reduced thickness of belt, the combined thickness of the first and second regions of reduced thickness being no more than the thickness of the rest of the belt, and the belt being formed into an endless loop to bring a surface of each region of reduced thickness into mutual confrontation, and form an overlapping butt joint, an adhesive having been applied to one or both of the mutually confronting surfaces to bond the mutually confronting surfaces together, a backing strip of material being further provided on the underside of the belt in the vicinity of the joint.

6. A conveyor belt including a joint as claimed in claim 5 or as made by the method of any one of claims 1 to 4.

7. A conveyor belt which in operation has a top surface and an underside surface and comprises a first end of belt material joined by way of a joint to a second end, the first end forming a leading edge of the joint when the belt is in use and the second end forming a trailing edge of the joint, characterised in that part of the underside of the first end is cut away to form a first region of reduced thickness, a part of the top surface of the second end is cut away to form a second region of reduced thickness, the first and second ends are bonded together to form an overlapping butt joint where the combined thickness of the first and second regions is no more than the thickness of the rest of the belt, and a backing strip is bonded to the underside of the joint in the vicinity of the first and second regions.

8. A conveyor belt joint substantially as hereinbefore described with reference to the accompanying drawing.