GB2234200A

GB2234200A - Injection moulding belting

Info

Publication number: GB2234200A
Application number: GB8916820A
Authority: GB
Inventors: Philip Ferdani
Original assignee: T&N Technology Ltd
Current assignee: Federal Mogul Technology Ltd
Priority date: 1989-07-22
Filing date: 1989-07-22
Publication date: 1991-01-30
Also published as: GB8916820D0

Abstract

An endless drive belt is made by injection moulding two elastomer components to produce a belt with a relatively hard core and a relatively soft working surface. Thermoplastic elastomers are preferred. The elastomer components are injected simultaneously or sequentially.

Description

Improvements in and relating to belting This invention relates to endless belting of the kind used to transmit power, for example between an electric motor and a pump.

Conventional belts comprising textile cords and vulcanised/cured rubber are relatively costly in respect of manufacturing time. Attempts to simplify the construction, for example by moulding belts directly from an elastomer material, have not been entirely successful, due, it is thought, to excessive slippage. One factor in this is lack of flexibility.

According to this invention, an endless drive belt is injection moulded from two elastomer components substantially simultaneously, or sequentially, to produce a belt with a relatively hard core and a relatively soft working surface.

Preferably the relative proportions and physical properties of the two components are selected such that the finished belt exhibits a tensile modulus similar to that of a homogeneous belt produced from a blend of said components. More preferably, the properties are selected such that the finished belt exhibits a better balance of flexural and tensile properties than those of a homogeneous belt produced from a blend of said components.

It has been found that a belt according to this invention has improved flexibility over a homogeneous belt of comparable tensile properties. In addition, there is improved abrasion resistance and a reduction in the rate of wear. Also, because the relatively soft material is on the surface of the belt, frictional properties are increased, leading to reduced slippage. It is also possible by selection of the components to adjust the belt properties for particular applications.

If desired, the relatively hard component can contain fillers and/or reinforcing fibres. These could be included during compounding/mixing.

The elastomer components are preferably thermoplastic.

Multi-component or sandwich moulding apparatus is known, particularly for the manufacture of structural articles having a core of a foamed rigid material. However, it was not previously thought useful to apply such a process to the manufacture of endless drive belts.

Particularly preferred elastomers are co-polyester thermoplastic elastomers, such as 'HYTREL' (trade mark), which can be manufactured to yield polymers having very different properties, for example, a relatively hard (high modulus) polymer and a relatively soft (low modulus) polymer. In this invention, the latter is used to form the relatively soft working surface of the belt and the former the relatively hard core.

In order that the invention be better understood, a preferred embodiment of it will now be described with reference to the following examples.

Example A: A homogeneous belt was made from a blend of 75% Shore D hardness 55 elastomer (HYTREL brand, grade 5526) and 25% Shore D hardness 40 elastomer (HYTREL brand, grade 4056). The belt had a tensile chord modulus (over the strain range 0-7%) of about 120 MPa.

Example B: The same materials were then processed into a belt according to the invention, with the relatively hard component forming the core and the relatively soft component forming the working surface of the belt. The product had approximately the same chord modulus over the strain range 0-7%, but had better flexibility. This was reflected in its improved running properties, i.e., reduced rate of wear, when tested under the same operating conditions as the homogeneous belt of Example A.

Claims

1. A process for the manufacture of an endless drive belt, characterised by the steps of injection moulding two elastomer components substantially simultaneously, or sequentially, to produce a belt with a relatively hard core and a relatively soft working surface.

2. A process according to claim 1, characterised in that the relative proportions and physical properties of the two components are selected such that the finished belt exhibits a tensile modulus similar to that of a homogeneous belt produced from a blend of said components

3. A process according to claim 1 or claim 2, characterised in that the elastomer components are thermoplastic.

4. A process according to any preceding claim including the step of compounding said elastomer components from a common thermoplastics elastomer material.

5. A process according to claim 3 or claim 4 characterised in that the elastomer is a thermoplastic co-polyester.

6. Endless belts made by the process of any preceding claim.