CA2191068A1

CA2191068A1 - Laminated composite body, in particular conveyor belt

Info

Publication number: CA2191068A1
Application number: CA002191068A
Authority: CA
Inventors: Dana Schwambach; Hans Uwe Bender; Hans Joachim Koch
Original assignee: Individual
Current assignee: ContiTech Transportbandsysteme GmbH
Priority date: 1994-05-27
Filing date: 1995-05-19
Publication date: 1995-12-05
Also published as: ES2122604T3; US5958570A; DE4418590A1; JPH10504500A; WO1995032861A1; EP0760745A1; EP0760745B1; DE4418590C2; DE59503934D1

Abstract

A laminated composite body, in particular a conveyor belt, consists of a carcass (2,2',2") that essentially determines the mechanical stability of the laminated composite body, and at least one cover (1,1') made of rubber, thermoplastic elastomer (TPE) and/or plastics that are highly resistant to mechanical damages such as notches, cuts or the like. In order to improve the resistance of the laminated composite body, the cover (1) is made of at least two layers (10, 11, 12) with different properties that are interconnected so as to form a clear phase limit.

Description

Laminated composite body, in particular conveyor belt The invention relates to a laminated composite body, in particular conveyor belt, comprising a support which es6entially determines a mechanical stability of the laminated composite body and at least one cover plate made of rubber, thermoplastic elastomer and/or plastics, which has a high resistance to mechanical damage in the form of notches, cuts or the like.
A particularly important example of a laminated composite body according to the invention is a conveyor belt.
The conveyor belt, as an essential component of belt conveying systems, essentially has to fulfill two tasks. The first task consists in transmitting a belt tenæile force, in order to build up sufficient normal forces in the belt between the drive drums to be able to transmit the drive force by means of the friction on the belt. The tensile force for overcoming the kinetic resistance i8 taken up by the mechanical reinforcement arrangements situated in the belt. The conveyor belt furthermore has to transport material for conveying. The material for conveying is regularly thrown onto the conveyor belt, specifically from a height of up to 10 m.
Since the material for conveying may also be sharp-edged rock or the like, the conveyor belt has to be configured such that the impact of the material to be conveyed on the conveyor belt does not lead to any damage to the REPLACEMENT SHEET

- 2 - PCT/DE95/00686 belt. To this end, the conveyor belt is provided with a cover plate, which in particular has the function of protecting the mechanical reinforcement arrangement in the tension support layer, which serves as support, from damage, since damage of this kind impairs or destroys the operating capacity of the belt. Steel cable arrangements or arrangements of a plurality of layers of fabric are conventional for the reinforcement arrangement.
Due to continuous pelting from the particles of bulk material, the top layer of the cover plate of a conveyor belt becomes scarred during operation, sometimes forming relatively small notches. The notches or scars may become the starting point for slitting or hairline cracks, which propagate as a function of the operating conditions (belt speed, trough of the conveyor belt, spacing of the drive rollers), of the material being conveyed and of the belt properties, as a result of the continuously changing states and concentrations of stresses at the crack tip. This may result in penetration as far as the tension support layer, which places the operating capacity of the conveyor belt in doubt. In practice, therefore, a conveyor belt which is exposed to the bulk material over a relatively long period of time is replaced when the surface of the cover plate exhibits numerous scars and notches due to the continuous impact of the bulk material.
A known measure for increasing the service time consists in increasing the thickness of the cover plate.

REPLACEMENT SHEET

- 3 - PCT/DE95/00686 As a result, the energy required for penetration is increased. However, it is not possible to prevent notches and cuts leading to penetration through even the greater thickness of the cover plate. The effect achieved with the increased use of material is therefore limited.
A further known measure for increasing the service life consiæts in incorporating transverse rein-forcements made of textile or metal materials. The latter have to join to the rubber well and permit the required trough properties of the conveyor belt. The aim of the transverse reinforcement is to cushion high inputs of energy from the falling material in that it absorbs forces itself, distributes the stresses and thus prevents direct penetration onto the tension support layer. Above all, it prevents those longitudinal cuts which may lead to steel cables fanning out. However, this measure does not make it possible to exclude the risk of notches and cuts being formed.
It is furthermore known, in order to increase the service life of belt cover plates, to introduce fibers into the cover plate material. In order that differing properties of the cover plate in the longitudinal and transverse directions should not arise, the distribution of the fibers has to be unoriented. However, conventional processing (calendering) of the cover plate produces a preferred alignment of the fibers, which does not make it possible to construct a closed fiber network. Therefore, the introduction of fibers into the cover plate is also REPLACEMENT SHEET

21910~8

- 4 - PCT/DE95/00686 only of limited use.
Another example of a laminated composite body mentioned at the outset is a roller having a cover layer applied on a metallic core, which cover layer is exposed to similar stresses, from granular and sharp-edged material being rolled, to the cover layer of a conveyor belt.
A laminated composite body of the type mentioned at the outset, designed as a conveyor belt, is disclosed by DE-A 17 50 410. In this case, a plurality of layers taking up the tension are provided, the cover plates which close off the layers taking up the tension to the outside being of single-layer construction.
EP O 431 907 A2 discloses a roller coated with rubber, on the metal core of which are applied two rubber layers, the two rubber layers being formed from essen-tially the same base material and the outer rubber layer merely having an additive increasing the abrasion resis-tance, for example in the form of a zinc salt.
A multilayer waterproof sheeting for roofs is known from DE 33 42 560 Al, in which sheeting an EPDM
rubber, which is per se advantageous, is provided with a glass fiber reinforcement, but on the outside is covered by an SEBS rubber layer which enhances the usual laying of the waterproof sheeting for roofs. The multilayer structure therefore stems from the usual laying technology for waterproof sheeting for roofs and is not intended to increase the resistance to mechanical damage REPLACEMENT SHEET

21910~8

- 5 - PCT/DE95/00686 in the form of notches, cuts or the like.
The same applies to the erosion-resistant and corrosion-resistant prOteGtive coating which is disclosed in DE 92 07 785 U1. The latter has an outer antiwear layer having a Shore A hardness of 45 to 75, a soft rubber layer beneath thi~ having a Shore A hardness of 45 to 55, a supporting layer and a fourth layer made of soft rubber having a Shore A hardness of 45 to 75. The sup-porting layer consists of a layer of steel, a layer of fabric or a layer of hard rubber having a Shore D hard-ness of about 70 to 80. The corresponding coating is intended to have a high resistance to chemically aggressive materials, which permit [sic] use in flue-gas desulfurization plants. Increasing the resistance to mechanical damage in the form of notches, cuts or the like was neither the desired object nor disclosed.
The object on which the invention is based consists in improving the cover plate of a laminated composite body of the type mentioned at the outset such that higher service times with respect to mechanical damage in the form of notches, cuts or the like become pos~ible.
In order to solve this problem, the laminated composite body of the type mentioned at the outset is characterized according to the invention in that the cover plate is formed from at least two layers which have different properties, are joined to one another and form between them a clear phase boundary which impedes the REPLACEMENT SHEET

2 1 9 1 ~68

- 6 - PCT/DE95/00686 propagation of cracks, by the fact that the outer first layer of the cover plate has a hardness which is at least 10% higher than a second layer, which adjoins the first cover layer on the inside, of the cover plate, the first layer having a Shore A hardness of between 50 and 80 and the second layer having a Shore A hardness of between 35 and 60, and the second layer, which adjoins the first layer, having an elasticity which is greater than 55% and at least 10% higher than the first layer.
The cover plate, which provides the protective function, of the laminated composite body according to the invention i8 of multilayer design, a clear phase boundary in the composite resulting from the formation of the plurality of layers having the differing hardness and elasticity properties. As a result, when a crack is formed in the outer layer of the cover plate, the propa-gation of the crack is stopped, or at least inhibited, at the phase boundary. The multilayer design having the layers formed according to the invention therefore makes it possible to achieve a significantly improved protec-tive function using the cover plate, for the same thick-ness of the cover plate.
In a preferred embodiment, the cover plate comprises three layers having two clear phase boundaries.
The material of the cover plate is preferably -as before - a rubber material based on natural and/or synthetic rubbers.
The first, outer layer of the cover plate prefer-REPLACEMENT SHEET

- 7 - PCT/DE95/00686 ably forms at least 30% of the thickness of the cover plate, if the overall thickness of the cover plate is, for example, 15 to 20 mm. If the overall thickness is significantly less, the outer layer should form a greater relative thickness of up to 50%. The first layer is expediently designed to have the greatest hardness and serves as an "armored layer".
The second layer is preferably designed to be more elastic than the first layer, in order to be able to absorb energy introduced via a crack tip or a notch elastically, i.e. without destruction of material.
The Shore A hardneæs of the first layer should preferably be 65 to 72 and the Shore A hardness of the second layer should preferably be 50 and [sic] 57.
The first and the second layers should have a strength of greater than 20 MPa and preferably greater than 25 MPa and an elongation of greater than 400%, preferably greater than 500%.
An important parameter for the first layer is a high abrasion resistance. The abrasion - measured in accordance with DIN - should be less than 120 mm3, preferably less than 100 mm3.
The elasticity which is essential for the second layer should preferably be greater than 60%.
The introduction and propagation of cracks in the cover plate can be reduced by filling at least the first layer with active filler, e.g. carbon black or silica.
The first layer is preferably formed with a REPLACEMENT SHEET

2 1 91 ~68

- 8 - PCT/DE95/00686 system crosslinked with little or no sulfur.
The differences producing the phase boundary between the first and the second layers may also include crosslinking with different systems.
Preferably, an inner third layer is present, which adjoins the second layer on the inside and has a Shore A hardness of 55 to 70, preferably a Shore A
hardness of 60 to 65, which value is between the hard-nesses of the first and the second layers.
The invention is explained in more detail below with reference to exemplary embodiments depicted in the drawing, in which:
igure 1 shows a section through a steel cable conveyor belt igure 2 shows a section through a multilayer rubber conveyor belt igure 3 shows a section through a cover plate structure having three layers Figure 4 shows a section through a roller structure.
According to Figure 1, a steel cable belt com-pri~es an outer, i.e. carrying-side, cover plate 1, a tension support layer 2 and a running-side cover plate 3.
The informer [sic] layer 3 has twisted steel cables 4 as mechanical reinforcement arrangement, which cables are embedded in a rubber material forming the tension support layer 2.
Transverse reinforcements 5, 6 may be introduced between the tension support layer 2 and the cover plates REPLACEMENT SHEET

1, 3.
Figure 2 ~hows a tension æupport layer 2', the mechanical reinforcement arrangement of which comprises three layers 7 of fabric. Binder layers 8 made of a rubber material based on natural or synthetic rubber are situated between the layers of fabric. Joining to the cover plates 1, 3 is effected by adhesive layers 9 applied to the respectively adjacent layers 7 of fabric.
Figure 3 illustrates that according to the invention the cover plates 1 compri~e a plurality of layers. In the exemplary embodiment depicted in Figure 3, a highly elastic ~econd layer 11 and a third layer 12, which if desired may be provided with a transverse reinforcement as protective layer, adjoins [sic] an outer first layer 10, which provides the function of an armored layer.
All three layers 10, 11, 12 are formed from rubber materials or thermoplastic elastomers. The first layer 10 has the greatest hardness, the second layer 11 the lowest hardness but the highest elasticity and the third layer 12 a medium hardness.
Clear phase boundaries, which at least inhibit propagation of cracks, are formed between the layers 10, 11, 12.
As a further example of the use of a laminated composite body according to the invention, Figure 4 shows a roller comprising a metal core as support 2'', on which are applied, over a binder layer 13, from the inside to REPLACEMENT SHEET

21 ~ 1~68 - the outside a third layer 12', a second layer 11' and a first, outer layer 10', which have the same features as the layers 10, 11, 12 of the conveyor belts described above.

REPLACEMENT SHEET

Claims

claims

1. Laminated composite body, in particular conveyor belt, comprising a support (2, 2', 2") which essentially determines a mechanical stability of the laminated composite body and at least one cover plate (1) made of rubber, thermoplastic elastomer (TPE) and/or plastics, which has a high resistance to mechanical damage in the form of notches, cuts or the like, characterized in that the cover plate (1) is formed from at least two layers (10, 11, 12) which have different properties, are joined to one another and form between them a clear phase boundary which impedes the propagation of cracks, by the fact that the outer first layer (10, 10') of the cover plate (1) has a hardness which is at least 10% higher than a second layer (11, 11'), which adjoins the first cover layer (10, 10') on the inside, of the cover plate (1), the first layer (10, 10') having a Shore A hardness of between 50 and 80 and the second layer (11, 11') having a Shore A hardness of between 35 and 60, and the second layer (11, 11'), which adjoins the first layer (10, 10'), having an elasticity which is greater than 55%
and at least 10% higher than the first layer (10, 10').

2. Laminated composite body according to claim 1, characterized in that the cover plate (1) comprises three layers (10, 11, 12) having two clear phase boundaries.

3. Laminated composite body according to claim 1 or 2, characterized in that the outer first layer (10) of the cover plate (1) forms 30 to 50% of the thickness of the cover plate (1).

4. Laminated composite body according to claim 1, 2 or 3, characterized by a Shore A hardness of the first layer (10) of between 65 and 72.

5. Laminated composite body according to one of claims 1 to 4, characterized by a Shore A hardness of the second layer (11) of between 50 and 57.

6. Laminated composite body according to one of claims 1 to 5, characterized in that the first and the second layers (10, 11) have a strength of greater than 20 MPa and an elongation of greater than 400%.

7. Laminated composite body according to claim 6, characterized in that the first and the second layers (10, 11) have a strength of greater than 25 MPa and an elongation of greater than 500%.

8. Laminated composite body according to one of claims 1 to 7, characterized in that the first layer (10) has an abrasion of less than 120 mm3.

9. Laminated composite body according to claim 8, characterized in that the first layer has an abrasion of less than 100 mm3.

10. Laminated composite body according to one of claims 1 to 9, characterized in that the second layer (11) has an elasticity of greater than 60%.

11. Laminated composite body according to one of claims 1 to 10, characterized in that the first and the second layers (10, 11) consist of a rubber material based on natural and/or synthetic rubber.

12. Laminated composite body according to one of claims 1 to 10, characterized in that at least the first layer (10) is filled with an active filler.

13. Laminated composite body according to one of claims 1 to 12, characterized in that the first layer (10) is formed with a system crosslinked with little or no sulfur.

14. Laminated composite body according to one of claims 1 to 13, characterized in that the first layer (10) and the second layer (11) are crosslinked with different systems.

15. Laminated composite body according to one of claims 2 to 14, characterized in that the third layer (12), which adjoins the second layer (11) on the inside, has a Shore A hardness of 55 to 70.

16. Laminated composite body according to claim 15, characterized by a Shore A hardness of the third layer (12) of between 60 and 65.

17. Laminated composite body according to claim 15 or 16, characterized by a design of the third layer having a high resistance to tear propagation.

18. Laminated composite body according to one of claims 2 to 17, characterized by a transverse reinforce-ment in the third layer (12).