GB2364560A - Combination seal for a double valve - Google Patents

Abstract

A combination seal, fitted as part of a conventional double valve of the type often used in pressurised beverage containers, has a coloured outer 24 made from a thermoplastic elastomer and a harder insert 25 made from a thermoplastic polymer. The elastomer is chosen so as to use a carrier polymer so as to bond to the insert during manufacture, as if by welding. The coloured outer is to assist the owner of the valve to implement a planned replacement policy for the combination seal, so as to avoid unplanned failure in service. The insert may also be coloured, so as to provide additional flexibility in the coding system. The seal is incorporated in use into a valve which in the open condition has a gas passage around the seal and a liquid passage through a central opening through the seal.

Description

2364560 COMBINATION SEAL FOR A DOUBLE VALVE This invention relates to the

combination seal fitted as part of a double valve of the kind used in a portable pressure container for distributing a liquid, e.g. beer, under pressure of a gas, e.g. Co2 and which, in open condition, has a gas passage around the outside of the seal and a liquid passage through the central opening of the seal.

The double valve as described above is used in many applications, e.g. for beverage distribution, where it is commonly known as the "S - Type". Variants used. in other applications have different conunon nwnes, but follow the same basic principle.

In the example of the beverage industry, the valve seal is used in the filling process to allow the passage of cleaning fluid, gas and product, resulting in a pressurised container which is delivered to the customer (e.g. - public house). The valve is then used to allow gas in round the outer part of the combination seal, and product out through the inner part, so that the customer can dispense portions of the beverage. Both the filling and dispense process use adapters which connect to the valve for the relevant purpose. Neither the valve mechanism, nor the filling or dispense adapters are changed by this invention, which is concerned only with the combination seal fitted inside the valve.

The container needs to retain pressure in order to keep the contents fresh, so the combination seal is a critical component of the valve and is usually made of a black thermosetting elastomer, with stainless steel insert(s) for stiffness and protection from damage. The stiffness so provided has the dual purpose of preventing the elastomer from distorting too much as to cause a leak, and also to prevent the combination seal from being pushed out either by pressure or by the tampering of an unauthorised person.

On a conventional combination seal, the inserts(s) are fixed to the black thermosetting elastomer either by using a bonding agent prior to the moulding process, or by mechanically crimping, or by using an insert which simply clips onto the elastomer part, and which can be detached only when the combination seal is removed from the valve.

2 During the lifetime of the valve, the pressurised container is expected to be used many times, and the filling process uses high temperature steam, cold sterile gas and various aggressive cleaning chen-ficals. In addition, the container may be left outside in all climates for many weeks before being filled or after filling. The result of these hard conditions experienced by the valve is that in practice, the combination seal fails before the container has reached the end of its usefid life, which can be more than 20 years. This results in the need for the valve to be removed and refurbished with a new combination seal. The cost of such failure is not limited to that of replacing the combination seal, but also includes the possible cost of lost product, lost customer satisfaction and transport to a suitable maintenance location.

It would be advantageous for the owners of the containers to have some simple means of noticing when a combination seal was of a certain age, so that it could be scheduled for replacement before it fails in use. As the various designs of conventional combination seals all use a thermosetting elastomer which has to be black to ensure good properties, the scheduling of routine maintenance cannot at present be done by looking at the valve whilst it is still fitted in the container, as all the seals look ahnost the same when fitted.

The object of this invention is to provide a combination seal to fit a standard valve as described above, which fiff& all the normal requirements of performance and life expectancy, but which offers a simple means of visually coding the seal using different colours, so that the owners of the containers can implement a routine replacement policy.

Accordingly, this invention achieves the objective by replacing the conventional black thermosetting elastomer, with a coloured thermoplastic elastomer, and by replacing the stainless steel inserts with a hard thermoplastic materiaL Additionally, the two thermoplastic materials are carefully selected so as to achieve the required performance, and also so as to bond together as if by welding, during the moulding process, to eliminate the risk of the elastorner detaching from the insert when subjected to the aggressive temperatures and chemicals in service.

Additional flexibility in the coding system can be achieved by making the outer elastomer in one colour, and the inner insert in a different colour.

The invention will be explained in greater detail below, with reference to the accompanying drawings, in which:

Figure 1 shows a complete valve assembly of the "S Type" commonly used in the beverage industry, in the closed position.

Figure 2 shows a complete valve assembly as in figure 1, but in the open position.

Figure 3 shows a conventional combination seal with a stainless insert, black outer elastorner and chemical bonding between the two.

Figure 4 shows a conventional combination seal with a detachable stainless insert which clips into a black elastomer outer.

Figure 5 shows a conventional combination seal with two stainless inserts and a black elastorner outer, where the elastomer is clamped by one insert and chemically bonded to the other.

Figure 6 shows an embodiment of this invention, with a solid thermoplastic insert, and a coloured thermoplastic elastomer moulded round the outside.

The valve can be of the type shown in figures I and 2, commonly called an "S-Type", but there are other variants of such a valve, and so the "SType" is used only to explain the invention.

In figures I and 2 are seen the complete valve in cross-section, where the combination valve (6) which is the subject of this invention, is shown as a simple shaded shape. The container body (5) is shown only in fragments, being welded to a connection piece (4), into which is fitted, by threads (10) or other means, the valve body (1), which contains the assembly of a downtube(2),shown in part only, an inner valve spring (9), an inner valve (7), an outer valve spring (8), a spring retainer (3) and the combination seal itself (6). The body is sealed to the connection. piece by means of a seal (11).

4 Figure I shows the valve in the closed position, and figure 2 shows the valve open with a dispense connector (12) shown in part. When open (figure 2), gas can flow through the dispense connector, through an annular aperture (13) around the combination seal (6), through holes in the body (1) and into the container, thus forcing liquid up the inside of the downtube (2), through the imer spring (9) and inner valve (7) and up through the centre (14) of the dispense connector (12).

When closed (figure 1), the pressure of the outer spring (8) closes the outer edge of the combination seal (6) against a special machined area of the body (1). Also, the inner spring (9) closes the machined sealing area of the inner valve (7) against the inner edge of the combination seal (6). Thus both the gas and liquid passages are closed.

Portable containers of this kind are often used for distributing beverages, when the gas may be Co2 and / or nitrogen and the liquid may be beer or soft drinks, however the containers can be used for many other purposes, both static and portable.

The valve undergoes repeated filling, dispensing and cleaning cycles during its life, and so is exposed to strong cleaning chemicals, high temperatures (e.g. - 130 degrees C), cold temperatures (e.g. minus 25 degrees C) and prolonged storage outdoors in extreme climates. In addition, thermal and mechanical shock forces are exerted when the valve is suddenly used after perhaps several weeks or months lying idle in the closed position.

The combination seal (6) has a triple role, firstly to seal, which requires the use of a soft material in parts, secondly to provide strength to resist the mechanical forces of spring pressure, gas pressure from the container and unauthorised tampering, and thirdly to provide wear resistance against the action of the chemicals, temperatures, environment and mechanical action of the filling and dispensing connectors.

To withstand these mechanical forces, the combination seal (6) requires a strong, hard insert, along with the softer material required for sealing purposes. Conventionally, the insert is made of stainless steel. The softer material required to make the sealing contact against the inside of the body (1) and the face of the inner valve (7) is conventionally made of thermosetting elastomer (e.g. - rubber, nitrile or EPDN1).

Three conventional combination seals are shown in figures 3,4 and 5. They all consist of stainless steel inserts for strength and black thermosetting elastomers for sealing.

With conventional thermosetting elastomers, the black colour is caused by carbon, which contributes greatly to the properties of the material, thus rendering the use of a coloured elastomer very difficult if the required durability is to be achieved.

In figure 3, the insert (15) is coated with a bonding agent before the elastomer (16) is moulded round it. Thus a chemical bond is formed between the insert (15) and the elastomer (16). Experience has shown that although performance and durability are good, the eventual failure is normally by detachment of the elastomer in the area (17) where the insert protrudes. Thus, the combination valve is unlikely to last as long as the valve body or container, which have a life expectancy greater than 20 years.

In figure 4, the insert (18) and the elastomer (19) are not bonded, but are clipped together using features moulded into the elastomere.g. - at region (20). The insert (18) is of sufficient diameter so as not to be pulled clear of the elastomer once the combination seal is assembled into the valve. In this design, the problems of bonding are eliminated, but the limitations in terms of life expectancy are now governed by the elastomer itself which is of conventional black thermosetting elastomer (e.g. rubber, nitrile or EPDM).

Figure 5 shows an alternative conventional design, with two inserts. One insert (23) is wholly embedded in the elastomer and is bonded to it with holes and chemical bonding. The second is fitted after the elastomer is moulded round the first insert, then it is crimped, so as to grip the elastomer and so eliminate the need for bonding. Again, although the seal is strong and doesn't have an exposed bonded joint, it's life is still governed by the conventional black thermosetting elastomer (e.g. - rubber, nitrile or EPDM).

The main disadvantage of the conventional combination seals as shown in figures 3, 4 and 5 is that neither the thermosetting elastomer nor the stainless steel insert lend themselves to colour coding, so as to allow preventive maintenance schemes to be developed by the owner of the 6 containers. This is eliminated by means of the specific structure of the combination seal as shown in figure 6.

This combination seal consists of a hard insert (25), made from a thermoplastic polymer, and a soft outer for sealing (24), made from a thermoplastic elastomer. The combination seal is made in the following way.

The insert is either moulded or machined from a suitable plastic polymer (e.g. - polypropylene). For additional strength, glass fibres may be added during the process. A typical process used would be conventional injection moulding into a specially shaped tool with cavity(s) of the required shape. Alternatively, the insert can be machined from solid polymer.

The insert (25) is then loaded to another specially shaped tool with cavity(s), and a thermoplastic elastomer is moulded so as to form the outer (24). The selection of materials is important, so that the elastorner uses a carrier polymer which melts into the surface of the insert (25) during the hot moulding process, thus forming a welded joint between the two. Aga4 a suitable process would be conventional injection moulding.

The colour(s) are created by using suitable additives when preparing either or both of the materials for the insert (25) or the outer (24), prior to moulding.

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Claims (3)

1. A combination seal as used in some valves fitted to portable pressure containers for filling and dispensing liquids (e.g. beer) under pressure of a gas (e.g. C02) and which in open condition has a gas passage around the seal and a liquid passage through the centre opening, characterised in that the seal comprises a solid insert made from a thermoplastic polymer and an outer made from a softer thermoplastic elastomer, which is coloured, so as to conform to a colour coding scheme.

2. A combination seal according to claim 1, characterised in that the thermoplastic elastomer used in the outer is chosen so as to use a carrier polymer which is compatible with and so welds into the solid insert during the manufacturing process.

3. A combination seal according to claims I or 2, characterised in that the solid insert may be coloured also, in a colour which contrasts With that of the outer, so as to give extra flexibility to the coding system.

Amendments to the claims have been filed as follows LA combination seal as used in some valves fitted to portable pressure containers for filling and dispensing liquids (e.g. Beer) under pressure of a gas (e.g. C02) and which in open condition has a gas passage around the seal and a liquid passage through the centre opening, characterised in that the seal comprises a solid insert made from a thermoplastic polymer and an outer made from a softer thermoplastic elastomer, chosen so as to use a carrier polymer which is compatible with and so welds into the solid insert during the manufacturing process.

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