WO1982000267A1

WO1982000267A1 - Improvements in or relating to conveyor belts

Info

Publication number: WO1982000267A1
Application number: PCT/GB1981/000140
Authority: WO
Inventors: Belt Ltd Cable
Original assignee: Thomson I
Priority date: 1980-07-16
Filing date: 1981-07-15
Publication date: 1982-02-04
Also published as: GB2082116A; BE889649A; EP0056035A1; PL232206A1

Abstract

A conveyor belt is constructed by forming at least one elongate mat in which a plurality of reinforcing elements are held in a fixed side-by-side but spaced relationship by an elastomeric material. The reinforcing elements extend transversely to the width of the associated mat. The or each mat is then bonded to a further layer or layers of material to form the conveyor belt with the mat extending along the length of the conveyor belt. The elongate mat may be formed by an extrusion process.

Description

IMPROVEMENTS IN OR RELATING TO CONVEYOR BELTS

The invention relates to methods of manufacture of conveyor belts of the kind comprising forming the belt from a plurality of layers of material bonded together, at least one of which includes reinforcing elements which extend transversely of the length of the belt.

A previously proposed conveyor belt of this kind comprises layers of elastomeric material with layers of a fabric sandwiched therebetween; the weft of the fabric being reinforced with metallic rods to provide lateral strength. It is a disadvantage of such a conveyor belt that accurate location of the reinforcements in the fabric is difficult and that the incorporation of the fabric into the conveyor belt cannot be easily achieved because the reinforced fabric is not readily handled.

According to a first aspect of the invention there is provided a method of manufacturing a conveyor belt of the kind comprising forming the belt from a plurality of layers of material bonded together, at least one of which includes reinforcing elements which extend transversely of the length of the belt characterised by the step of forming at least one layer as an elongate mat of elastomeric material in which a plurality of reinforcing elements are held in a fixed side-by-side relationship by the elastomeric material, each reinforcing element extending transversely to the length of the elongate mat, and then bonding the or each elongate mat to at least one further layer of material for form the conveyor belt, the elongate mat, in the conveyor belt, extending along the length of the conveyor belt so that the reinforcing elements extend transversely to the length of the conveyor belt.

According to a second aspect of the invention, there is provided a conveyor belt of the kind comprising a plurality of layers of material bonded together, at least one of which includes reinforcing elements extending transversely of the length of the belt, characterised in that at least one of the layers comprises an elongate mat (13 or 21) of elastomeric material in which a plurality of reinforcing elements (19 or 24) are held in side-by-side but spaced relationship by the elastomeric material, the or each elongate mat extending along the length of the conveyor belt and each reinforcing element extending transversely to the length of the conveyor belt.

The following is a more detailed description of two embodiments of the invention, by way of example, reference being made to the accompanying drawings in which:-

Figure 1 is a diagrammatic cross-section of a conveyor belt;

Figure 2 is an exploded longitudinal cross-section of a part of a first form of the conveyor belt of Figure 1;

Figure3 is a diagrammatic view of an extruder for producing a layer for incorporation into the conveyor belt of Figures 1 and 2; and

Figure 4 is an exploded longitudinal cross-section of a part of a second form of the conveyor belt of Figure 1.

Referring first to Figure 1, the conveyor belt forms a continuous loop and is supported and driven by two rope circuits, one running along each lateral edge of the belt. The ropes, which may be steel ropes, are in turn supported by pulleys and stand assemblies at intervals along the conveyor system formed thereby.

The conveyor belt is provided with a pair of grooves 10, 11 running along each lateral edge thereof; one groove 10 of each pair running along the upper surface of the conveyor belt and the other groove 11 of each pair running along the under surface of each belt. In a load-conveying run of the conveyor belt, the two grooves 11 on the under, surface of the conveyor belt engage with the rope to provide support and drive for the conveyor belt. At the end of the load-conveying run of the conveyor belt, the ropes are led out of their respective grooves 11 and the direction of the travel of the conveyor belt is reversed in a return run during which the ropes engage the grooves 10, which were on the upper surface of the conveyor belt in the load bearing run, but which, in the return run, are on the under surface of the conveyor belt. Thus, the conveyor belt is also supported and driven by the ropes in the return run. The ropes are driven by any suitable drive means (not shown) arid, in the load bearing run of the conveyor belt, the conveyor belt troughs between the ropes under the weight of the load to contain the load. The degree to which the belt troughs for a particular load is determined by the lateral bending characteristics of the conveyor belt.

Referring next to Figure 2, one embodiment of the conveyor belt comprises a central core 12, two elongate mats 13 and two facing sheets 14, all bonded together' by a method to be described in more detail below. The central core is formed by two core fabric layers 15, 16 sandwiched between two core layers 17, 18 of elastomeric material. The core fabric layers 15, 16 may be of a woven material such as woven artificial fibres while the elastomeric core layers 17, 18 may be polychloroprene rubber.

Each elongate mat 13 comprises a plurality of parallel side-by-side but spaced reinforcing elements 19 fixed in position by an elastomeric material surrounding the reinforcing elements 19 and extending therebetween. The reinforcing elements 19 may be mecal cords or wires coated with brass or with a suitable bonding agent to ensure adhesion between the metal cords or wires and the elastomeric material. The elastomeric material may be polychloroprene rubber as are the facing sheets 12 which have the grooves 10, 11 formed on their surfaces.

The conveyor belt of Figure 2 is manufactured by the following method: first the elastomeric core layers 17, 18 and core fabric layers 15, 16 are prepared to the required length and width. The fabric layers 15, 16 are treated with adhesives or bonding agents to ensure their bonding in the completed structure. The facing sheets 14 are also prepared to the required length and width.

Each elongate mat 13 is formed as follows. A plurality of reinforcing metal wires or cords 19 are coated with brass to a thickness, for example, of 0.3 microns or are coated with a suitable bonding agent to allow adhesion. The reinforcing metal wires or cords 19 are then fed in the required side-by-side but spaced relationship through an extruder 30 (Fig.3) in which an elastomeric material is extruded around the reinforcing metal wires or cords 19 to hold the metal wires or cords in the required side-by-side but spaced relationship. Thus, an elongate strip 31 is formed which has the reinforcing metal rods or cords 19 extending along its length in the required relationship.

This elongate strip is then divided along lines transverse to the length thereof to form segments 20. The length of the segments is chosen to be the required width of the finished conveyor belt. The edges of the segments formed by this division are then connected in edga-to-edge relation to form an elongate mat. The connection may be by gluing or by heat sealing.

Two such elongate mats of required length are then arranged with the two elastomeric core strips 16, 17, the two fabric core strips 15, 16 and the facing sheets 14 as shown in Figure 2 and the layers of material are vulcanised under pressure to produce a completed conveyor belt. Referring next to Figure 4, a simplified construction of the conveyor belt of Figure 1 comprises top and bottom covers 21, 22 with a core structure 23 sandwiched therebetween. The top cover 21 is formed in the same way as an elongate mat 13 of the Figure 2 embodiment but is provided with a greater thickness of rubber to one side of the reinforcing metal cords or wires 24 to form an upper load carrying surface of the finished conveyor belt. The bottom cover 22 is constructed in the same way as an elongate mat 13 of the Figure 2 embodiment.

The core structure 23 comprises a fabric strip 25 which is of a similar type as the fabric core strips 15, 16 in the Figure 2 embodiment but having twice the tensile strength in the warp direction (i.e. in the longitudinal direction of the conveyor belt). The fabric strip 25 is calendered to a strip of elastomeric material such as polychloroprene rubber. After formation of the top and bottom covers 21, 22 and the core structure 23, these three layers are joined together by a vulcanising process to form the completed conveyor belt.

It will be appreciated that the conveyor belts of Figures 2 and 4 may be formed with more than two layers of reinforcing elements; any number of such layers can be provided and where an even number of layers are provided, the layers are arranged in equal number on either side of the core layer. In addition, the core layer may comprise more than two fabric core strips and more than two elastomeric core strips.

Where more than two layers of reinforcing elements are provided, some of the layers may not extend across the whole width of the conveyor belt and may, for example, extend across only a central section of the width of the conveyor belt. In addition, the spacing between correspondin layers on opposite sides of the central core may be arranged to decrease from a maximum at the centre of the conveyor belt to a minimum towards the edges of the conveyor belt.

Examples of materials suitable for use in the construction of the conveyor belts of Figures 2 and 3 are as follows:-

1. A rubber for the elastomeric core strips 17, 18 of elongate mats 13, the facing sheet 14, in Figure 2 and for the top and bottom covers 21, 22 and the core structure 23 in the Figure 3 embodiment;

Adhesion - 31.5 newtons/cm.

Electrical surface resistance - less than 3 x 10⁸ ohms

Fire resistance - Self-extinguishing to National Coal

Board specification 158/1971 part 4.

Hardness - 66 to 70 I.R.H.D.

Tensile strength - 12.1 MPa

Modulus at 200% elongation - 6.9 MPa

Elongation at break - 350% Tear - 29.8 newtons/mm²

2. Reinforcing elements 19,24 :-

A. Steel cored having a core strand of 0.30 mm in diameter around which are twisted six strands each of

0.25 mm in diameter so as to form a total diameter for each cord of 0 . 80 mm. Breaking s trength - 895 newtons /mm²

Linear density - 2. 9 grammes /metre

Ends per centimetre. - 7 . 4.

B . Monofilament oil-hardened and tempered s teel having a diameter of 1.22 mm.

Breaking strength - 1776 newtons/mm²

Ends per centimetre - 1.0

3. A fabric suitable for the core fabric strips 15, 16 of the Figure 2 embodiment and for the fabric 25 in the Figure 4 embodiment:- Material - ICl nylon 66 (Trade Mark) type 162. Warp tensile strength - 61.3 newtons/mm²

Weft tensile strength - 52.5 newtons/mm²

Warp thickness - 940.1 decitex

Ends per decimetre - 98.4

Pics per decimetre - 33.9

Weight - 196.7 grammes per m²

Force for 5% elongation both warp and weft -

17.5 newtons/mm ²

In use of the conveyor belt of Figures 2 and 3, the two spaced sets of reinforcing steel cords or wires 19 form a composite beam structure with sufficient flexural rigidity across the width of the belt to support the load yet allow troughing of the belt under load with transmission of the reaction forces produced by the load to the support ropes. The fabric core provides tensile strength in the direction of the length of the belt.

The embodiments described above with reference to the drawings are advantageous because the extrusion of the reinforcing elements with elastomeric material positions the reinforcing elements at a required spacing thus making the cords easily handled. This ensures accurate location of the reinforcing elements in the completed conveyor belt, thus preventing weaknesses.

Furthermore, the failure of one of the reinforcing elements in service has a much less critical effect and the structure is less susceptible to damage by accidental cutting. Additionally, the structures of the conveyor belts of Figures 2 and 4 have higher internal damping allowing higher speeds over pulleys without spill. This higher internal damping also reduces spill should belt bounce occur at leading points, thus reducing spill noise. The even surface of the belt prevents local damage by belt cleaners or scrapers and allows a wide variety of belt cleaning devices to be used. The all-bonded construction prevents protrusions of loose steel reinforcing strands or wear-through owing to internal friction of belt components.

Instead of polychloroprene rubber, other rubbers could be used such as Ethylene/propylene rubber (EPDM) Styrene butadiene rubber (SBR), natural rubber or thermoplastic rubbers. It is not essential, although desirable, that the compound be flame-resistant.

The central core 20 and the core structure 22 can be made from an elastomeric material which is different from that used for the facing sheets 14.

Claims

1. A method of manufacturing a conveyor belt of the kind comprising forming the belt from a plurality of layers of material bonded together, at least one of which includes reinforcing elements which extend transversely of the length of the belt, characterised by the step offørming at least one layer as an elongate mat of elastomeric material in which a plurality, of reinforcing elements are held in a fixed side-by-side but spaced relationship by the elastomeric material, each reinforcing element extending transversely to the length of the elongate mat, and then bonding the or each elongate mat to at least one further layer of material to form the conveyor belt, the elongate mat, in the conveyor belt, extending along the length of the conveyor belt so that the reinforcing elements extend transversely to the length of the conveyor belt.

2. A method according to claim 1 and characterised by further comprising forming the or each elongate mat from a plurality of segments, each mat segment comprising a length of elastomeric material containing a number of said reinforcing elements in said fixed relationship and the segments being. connected in edge-to-edge relationship to form said elongate mat.

3. A method according to claim 2 characterised in that the segments are connected together in said edge-to-edge relationship by an adhesive.

4. A method according to any one of claims 1 to 3 and characterised by further comprising forming the segments from an elongate strip in which a number of reinforcing elements are located in said side-by-side but spaced relationship by elastomeric material, each reinforcing element extending along the length of the elongate strip and the elongate strip being divided along lines transverse to the length thereof to form said segments, the division lines forming the edges of the segments for connection together to form the or each elongate mat.

5. A method according to claim 4 and in which each reinforcing element is continuous along the length thereof, the method being further characterised by the step of extruding the elastomeric material around said number of reinforcing elements arranged in a required side-by-side but spaced relationship to form said elongate strip.

6. A method according to, claim 5 characterised in that the continuous reinforcing elements comprise metai wires or cords, the metal wires or cords being coated with brass or a bonding material before the extrusion steps.

7. A method according to any one of claims 1 to 6 in which there are an even number of elongate mats in the conveyor belt and in which the further layers of material include an elongate core, the metiiod being further characterised by arranging the elongate mats in equal numbers on either side of the elongate core and then bonding together the elongate mats and the elongate core to form the conveyor belt.

8. A method according to claim 7 and in which the elongate core includes at least one elongate core layer of elastomeric ^material and at least one fabric core layer, the method being further characterised by the step of treating the or each fabric core layer with an adhesive or a bonding agent before bonding together the elongate mats with the elongate core therebetween.

9. A method according to claim 7 or claim 8 and in which there are two elongate core layers of elastomeric material and two fabric core layers, the method being further characterised by the step of arranging the two fabric core layers between the two elongate core layers of elastomeric material before the bonding step.

10. A method according to any one of claims 7 to 9 in which there are provided four .or more elongate mats, the method being characterised by the step of arranging an elongate strip of elastomeric material between the or each adjacent pair of elongate mats on each side of the core layers before performing the bonding step.

11. A method according to any one of claims 1 to 10 and characterised by the step of arranging a facing strip of elastomeric material on the outer surface of the outermost elongate mat before performing the bonding step.

12. A conveyor belt when made by the method of any one of claims 1 to 11.

13. A conveyor belt of the kind comprising a plurality of layers of material bonded together, at least one of which includes reinforcing elements extending transversely of the length of the belt, characterised in that at least one of the layers comprises an elongate mat (13 or 21) of elastomeric material in which a plurality of reinforcing elements (19 or 24) are held in side-by-side but spaced relationship by the elastomeric material, the or each elongate mat extending along the length of the conveyor belt and each reinforcing element extending transversely to the length of the conveyor belt.

14. A conveyor belt according to claim 13 characterised by comprising an even number of elongate mats (13; 21, 22) with the further material including an elongate core (12, 23), the elongate mats being arranged in equal numbers on either side of the elongate core.

15. A conveyor belt according to claim 13 or claim 14 characterised in that the core (12) includes at least one elongate core layer of elastomeric material (17, 18) and at least one core fabric layer (15, 16).

16. A conveyor belt according to claim 15 and characterised by comprising two core layers of elastomeric material (17, 18) and two core fabric layers (15, 16), the two core fabric layers being sandwiched between the two core layers of elastomeric material.

17. A conveyor belt according to any one of claims 13 to 16 and characterised by comprising four or more elongate mats with an elongate strip of elastomeric material being arranged between the or each adjacent pair of elongate mats on each side of the core layer.

18. A conveyor belt according to any one of claims 13 to 17 and characterised by comprising a facing strip (14) of elastomeric material on the outer surface of each outermost elongate mat.

19. A conveyor belt according to claim 18 when dependent on claim 15 characterised in that a fabric layer is provided between each elongate mat and an associated facing sheet in addition to or as an alternative to the or each fabric layer .in the core.

20. A conveyor belt according to any one of claims 13 to 19 characterised in that the reinforcing elements (19; 24) comprise steel cords or steel wires.