GB2411195A

GB2411195A - A resilient pad for absorbing vibrations in machinery, construction and rail applications.

Info

Publication number: GB2411195A
Application number: GB0403729A
Authority: GB
Inventors: Hugh Rogers
Original assignee: TIFLEX Ltd
Current assignee: TIFLEX Ltd
Priority date: 2004-02-19
Filing date: 2004-02-19
Publication date: 2005-08-24
Also published as: GB0403729D0

Abstract

A pad or mat 2 for absorbing vibration and/or impact absorption, for example for use in connection with heavy machinery or in construction and rail applications, the pad or mat 2 comprising: a plurality of tubular, compressible, gas-filled cells 14 arranged in layers 12 such that the pad or mat 2 absorbs impacts and/or attenuates vibration. The layers may be enclosed in outer protection layers 5, 6, 8, 10, and reinforcing/stiffening layers 16 may be provided between each layer 12 of cells 14. Stiffness and other characteristics of the pad or mat 2 may be varied by varying the dimensions of the cells and/or materials of components of the pad or mat 2. A method of manufacturing such a pad or mat 2 is also disclosed.

Description

24t1195

PAD

The present invention relates to a vibration- or impact-absorbing pad.

Embodiments of the invention find particular application in (although the invention is not limited to) the rail industry. The invention generally is intended for application in connection with impact absorption, vibration reduction, equipment protection, acoustic applications, etc. Pads and mats, such as rail pads, baseplate pads, undersleeper pads, and ballast mats, are known in the rail industry, where they are used to attenuate noise and vibration transmitted through the ground to adjacent buildings, and to reduce the severity of impacts in order to protect sleepers and ballast, for example. The physical dimensions of the pad or mat used in a particular application may be dictated by the application. However, the performance characteristics of the pad or mat (i.e. impact attenuation, stiffness, etc) are to an extent dependent upon its physical dimensions and characteristics (e.g. thickness, configuration and materials), and wide ranges of performance characteristics are required for the fields of application of the pads and mats.

The uses of pads and mats overlap and, and the invention is equally applicable to both. Therefore, in the present description and the claims the word pad only will be used. However, this is to be taken also to mean mat.

It is an aim of the invention to provide pads of varying dimensions and having varying characteristics, and a method of producing the same.

Therefore, in accordance with a first aspect of the present invention, there is provided a vibration- or impact-absorbing pad for absorbing impact or vibration in connection with heavy machinery, construction and rail applications, comprising a defined layer of closed, compressible, gas-filled cells arranged such that an impact upon or vibration at a surface of the pad is absorbed by - 2 compression of at least some of the cells.

Such a pad may be advantageous in that the performance characteristics of the pad are more predictable and in that it may be tailored in size. It may therefore be possible to tailor a pad to a particular application by selection of the number of layers and/or the size or number of spacers, etc. Preferably, the cells are elongate and have a longitudinal axis substantially within the plane of the layer. Such an arrangement may provide greater case of manufacture and greater facility for controlling the response to vibration or impact.

Preferably, the pad comprises a plurality of layers. In this way, the manufacture of pads may more easily be tailored to desired physical dimensions and performance characteristics (e.g. stiffness).

Preferably, the pad further comprises a stiffening layer disposed between two layers of cells. The provision of a stiffening layer (or a plurality of stiffening layers) may confer the advantage of allowing further variation in the performance characteristics of the pad.

Preferably, at least one surface of the pad is covered by a protective layer. The provision of such a layer (for example, of rubber, thermoplastic elastomer or other thermoplastics material) may act as a barrier between the cells and the outside environment (e.g. ballast) helping to protect the cells and reducing the likelihood of premature failure.

A further aspect of the invention provides a method of manufacturing a pad for absorbing impact or vibration in connection with heavy machinery or rail applications, comprising forming a layer of closed, compressible, gas-filled cells. - 3

Particular embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a schematic cross-section through an embodiment of a pad in accordance with invention; Figure 2 shows a schematic plan view of a layer of cells of the embodiment shown in Figure 1; and Figure 3 is a perspective view in part section of a single layer of cells in accordance with a preferred embodiment.

Figure 1 shows a schematic cross-section through a pad 2 having first and second opposing surfaces 3, 4 bearing upper and lower protection layers 5, 6 formed of rubber, a thermoplastics material (e.g. a thermoplastic elastomer) or a thermoses elastomer. Edges 8, 10 are also covered with protection layers such that the whole surface of the pad is protected from the outside environment. A plurality of layers 12 (see figure 2), each comprising a plurality of compressible cells14 filled with air or other gas, is provided between the upper and lower surfaces 3, 4 of the pad.

In embodiments for use in environments where it is not required, the protection layers 5, 6 may be dispensed with.

Stiffening layers 16 are provided between the layers 12 of cells 14. The stiffening layers 16 serve for example to reduce flexing of the pad. Stiffening layers 16 may be provided between each pair of adjacent layers, as shown in figure 1.

However, in alternative embodiments, other arrangements may be provided; for example, a single stiffening layer 1 6A may be provided towards the middle of the pad or a single layer 1 6B may be provided beneath the first layer 1 2A of cells 14.

In a preferred embodiment, the stiffening layer or layers 16 is formed of the same material as the protective layer 5, 6. In alternative embodiments, however, the stiffening layer or layers 16 are formed of various materials of varying - 4 thicknesses.

Figure 2 shows a schematic plan view of a layer 12 of cells 14. The cells are formed in a cell membrane 18 and they may be arranged for example in a hexagonal arrangement A (in figure 2) or a square arrangement B. An arrangement may be selected in order to provide the desired cell density. In addition, the thickness (dimension perpendicular to the plane of figure 2) of the cells, their radius and their spacing may all be varied to achieve desired performance characteristics (e.g. stiffness).

The membrane 18 is formed of a thermoplastics material (e.g. a thermoplastic elastomer) or a thermoses elastomer.

In a particularly preferred embodiment, one of the layers 12' of which is shown in Figure 3, the cells 14 are tubular (e.g. elongate and substantially cylindrical), and have a longitudinal axis substantially within the plane of the layer 12'. The cells 14 are formed by forming (for example, by crimping) longitudinal bonds 20 between two layers of membrane, resulting in long parallel tubular cells. Further bonds 22, substantially parallel to the first 20 are then formed with a spacing equal to the intended length of the tubular cells. A plurality of such layers 12' are made in stacked to form the pad, which may further comprise one or more stiffening layers and/or protection layers as described above.

The dimensions, e.g. diameter, length and wall thickness, of the tubular cells depend upon the intended application of the pad. For many applications they will typically have a diameter of around 10mm to around 50mm, length of around 20mm to around 30mm and wall thickness of up to around 2mm. The stiffness of the pad may be tailored, for example by selecting cell length. The stiffening and/or protective layers may, for example, be formed of a hard rubber material and have a thickness of around 5mm to around 10mm.

When a surface of the pad is subjected to a force directed generally in the direction of the pad, the layers of the pad will Initially deflect, the cells compressing in the direction of the applied force (such that the contact area between the cells and the stiffening layers increases) until the force generated by cells counteracts the applied load. The maximum load under which the pad is able to perform is that load under which the pad will no longer distort further given a small increase in load.

The ranges of performance characteristics required in the fields of application of the pads may be achieved by varying one or more of: the materials of components (e.g. rubber, thermoplastics, thermoplastic elastomer, thermoses elastomer), the cells (e.g. dimensions, structure, arrangement, shape), and the layers (e.g. arrangements - stiffening layers, etc. number of layers). - 6

Claims

1. A vibration- or impact-absorbing pad for absorbing impact or vibration in connection with heavy machinery, construction and rail applications, comprising a defined layer of closed, compressible, gas-filled cells arranged such that an impact upon or vibration at a surface of the pad is absorbed by compression of at least some of the cells.

2. A pad according to claim 1, wherein the ceils are elongate, having a longitudinal axis substantially within the plane of the layer.

3. A pad according to claim 2, comprising a plurality of layers of cells.

4. A pad according to claim 3, further comprising a stiffening layer disposed between two layers of cells.

5. A pad according to any of the preceding claims, comprising a protective layer on a surface thereof.

6. A method of manufacturing a pad for absorbing impact or vibration in connection with heavy machinery or rail applications, comprising forming a layer of closed, compressible, gas-filled cells.

7. A method according to claim 6, comprising forming a plurality of. said layers in a stack.

8. A method according to claim 7, further comprising providing a stiffening layer between two of the layers.

9. A method according to any of claims, 6 to 8 comprising providing a protective layer on a surface of the pad. - 7

10. A pad substantially as hereinbefore described with reference to, and/or as illustrated in, the accompanying drawings.

1 1. A method of impact and/or vibration absorption comprising using a pad as claimed in any of claims 1 to 5 or claim 10.

12. A method of providing impact and/or vibration absorption in a railway track, comprising installing a pad as claimed in any of claims 1 to 5 or claim 10 as a rail pad, a baseplate pad, an undersleeper pad or a ballast mat.

13. A method substantially as hereinbefore described with reference to, and/or as illustrated in, the accompanying drawings.