GB2261266A - Packing - Google Patents

Abstract

A tank lid packing consists of a hollow body 1 of thermoplastic elastomer, an impervious PTFE cover 2, and a protective PTFE outer braid 3. Ends of the body can be welded together to form a completely impervious loop. The hollow in the body allows the behaviour of the body under compression to be controlled. <IMAGE>

Description

PACKING This invention relates to packings for sealing openings, for example for use between the lid and body of a tank, to seal the lid.

A wide variety of packings are used for sealing tank lids, doors, hatches and the like. One such packing is described in GB 1567199 and is particularly suitable for sealing containers containing solvents and other liquid chemicals. This packing incorporates a braided body for example polypropylene, which can be welded to form a closed loop. However, the packing described in GB 1567199 does not provide a perfect seal against gases, or liquids of low boiling point; it can permit very slight leakage of such materials through the braided body. In general this is not acceptable, as a lid packing should provide a perfect seal at required elevated pressures, eg up to 1 bar.

Another known form of packing has a body of solid vulcanised rubber. These cannot easily be formed into completely closed loops and the solid body does not allow easy control of deformation under pressure.

An object of the present invention is to provide a packing capable of perfect sealing against gases or liquids of low boiling point.

According to the present invention a packing comprises a body of a resilient weldable thermoplastic elastomer, and a protective covering.

The covering may give protection against physical damage and/or it may prevent contact between the body of the packing, and chemicals or gases contained in the ves-el to be sealed.

Preferably, the body is enclosed in at least one layer of flexible impervious material, which in turn is enclosed within a physically protective layer.

Preferably, the body itself is chemically and physically inert or resistant, relative to the gases or liquids to be sealed.

The body is preferably hollow and the profile of the internal hollow void is preferably so selected that the packing will undergo controlled deformation when compressed in use and in particular will give maximum lateral deformation or bulging to improve the seal.

The use of a hollow body for the packing enables the manufacturer to control the deformation of the packing under pressure, by suitably selected the shape and size of the internal hollow or void, without changing the external shape or dimensions, or material, of the elastomer body.

Because the entire body of the packing is made of a thermoplastic elastomer, the ends of a length of lengths of packing can be welded together to form an endless loop of any required size with no discontinuity that would impair the seal. The elastomer itself is solid and provides no leakage path through its volume.

The accompanying drawings show, by way of example only, a cross section of one form of packing embodying the invention.

The illustrated packing consist of three components.

The innermost component is a resilient chemically resistant thermoplastic elastomer body 1. This is of extruded thermoplastic/EPDM material. It preferably has a central longitudinal hollow or void 4.

The thermoplastic elastomer body 1 is wrapped with one or more layers of impervious PTFE tape 2. This wrapping prevents contact between the thermoplastic elastomer body, and liquids, gases or vapours to be sealed.

Outside the PTFE wrapping is one or more layers of fine outer braid 3 providing protection against physical damage. The outer braid is made of mechanically and chemically resistant yarn, preferably PTFE; other materials such as aromatic polyamide, polypropylene etc may be used.

The elastomer body 1 provides the resilience required in the packing. Its shape, and in particular the shape of the void 4, are designed to provide predetermined controlled deformation of the packing when it is compressed between a tank lid and body in use, to give maximum deflection or bulging on the sides. It will be understood that the packing is normally located in a groove, and that lateral deformation, causing it to contact the sides of the groove under pressure, provides greatly enhanced, substantially perfect, sealing.

Although the drawing shows a void of simple substantially circular outline, voids of other outline, for example with two or three lobes, may be provided.

The external cross sectional shape of the packing can be square, rectangular, circular or any other shape required for a particular application.

In use, the packing is fitted into a groove of a lid or cover, or a groove surrounding an opening to be sealed.

One or more lengths of packing are cut to the correct length to fit the groove. The ends of the length or lengths of packing can be welded together to form an endless seal, which is as fluid-tight at the join between the ends as it is elsewhere. The welding can be performed for example by placing the end faces of the packing against a hot plate at a suitable temperature, to soften or melt the thermoplastic elastomer body, and then forcing the two heated end faces together to form a weld.

To protect the join or weld, the outside of the packing at this position is wrapped with one or more layers of impervious tape or film, eg unsintered PTFE tape, over which is placed one or more windings of PTFE yarn.

The described packing can form an efficient seal between the lids and bodies of chemical, solvent, liquid or gas tanks, for marine or industrial applications, using conventional chemical carrier hatches and lids without modification. It can provide a substantially perfect seal against gases and low-boiling point chemicals. It will recover fully when the sealing pressure is released and does not acquire a permanent set. Furthermore it is chemically resistant and will not soften in contact with commonly encountered liquids and gases, nor will it contaminate such materials.

Claims (8)

CLAIMS:

1. A resilient packing comprising a resilient body made of a weldable thermoplastic elastomer, and a protective cover enclosing the body.

2. A packing as claimed in claim 1 in which the cover is substantially impervious.

3. A packing as claimed in claim 1 or 2 in which the cover is mechanically protective.

4. A packing as claimed in claim 1 in which the cover comprises an inner layer or layers of substantially impervious flexible material, and a physically protective outer layer.

5. A packing as claimed in claim 4 in which the outer layer is a braid

6. A packing as claimed in any of the preceding claims in which the body is hollow.

7. A packing as claimed in any of the preceding claims, in the form of an endless loop formed by welding together the thermoplastic elastomer material of the body of the packing at the ends of a length or lengths of the packing.

8. A resilient packing substantially as herein described with reference to the accompanying drawing.