IE84545B1 - A gasket - Google Patents

Description

Introduction The present invention relates to gaskets, and in particular to gaskets for sealing between facing surfaces of two engaging flanged parts or ferrules for use in exacting environments such as in the pharmaceutical or food industries.

It has been known to provide solid gaskets of various fluoroplastics materials such as tetrafluoroethylene (TFE) in which the gasket is of a substantially disc-like shape having a peripheral slot forming an inner core which is filled with elastomeric material.

The elastomeric material gives resilience to the gasket. Such a gasket, for example, is described and claimed in US Patent Specification No. 3,775,832 (Werra). This gasket is relatively efficient and performs an adequate sealing function as it is possible to use materials which are unaffected by most gases or solvents and generally have useful physical properties.

However, in certain situations, such a gasket is not good enough. For example, very often what is required is a gasket or seal with greater resilience and deformability and elastic properties. Generally, elastomeric sealing rings or gaskets have a problem in that very often the gasket or seal extrudes from the joint when compressed or under pressure of conveyed fluid in, for example, high pressure pipelines. This causes problems in that there is now a constriction to the fluid flow which can cause considerable problems such as, for example, bacteria traps when conveying certain fluids.

GB Patent Specification No. 644,845 describes a seal or gasket for pipe joints which goes some way to overcoming these difficulties. This seal comprises an inner liner of steel on which is mounted a further seal of elastomeric material such as, for example, synthetic rubber or the like material. It is essentially a mechanical joint between the two parts of the seal. Unfortunately, these do not always work satisfactorily. The two parts of the seal tend to separate and there is not sufficient rigidity or support for the elastomeric portion of the seal. Very often, what is required is to have a considerable amount of the seal formed from this elastomeric material, however, such material, as explained in GB Patent Specification No. 644,845 distorts, bulges and generally does not retain its shape.

What is required is a seal, having the properties of an elastomeric material, which at the same time will have sufficient structural rigidity to retain its shape between the mating surfaces while its own outer surface will be sufficient as to accommodate irregularities in the mating surfaces.

The present invention is directed towards providing such a gasket.

Statements of Invention According to the invention, there is provided a composite gasket for sealing between facing surfaces of two engaging parts comprising a rigid annular disc-like inner member and an elastic annular disc-like outer member, the rigid annular disc-like inner member being of a tough substantially non-deformable material and comprising an inner portion having a bore and a pair of spaced-apart inner part contacting surfaces, and an outer portion projecting into and integral with the elastic disc-like outer member which is of an elastomeric material having spaced-apart outer part contacting surfaces. The advantage of this gasket is that the inner member gives structural rigidity to the whole gasket and ensures, for example, that there will be no bulging into the bore. It also gives general rigidity. At the same time, since the outer surface of the major portion of the seal is of elastomeric material, imperfections in the mating surfaces are easily accommodated.

Thus. effectively this present gasket provides all the advantages of the prior art gasket such as. for example, described and claimed in US Patent Specification No. 3775832 (Werra), without the problems that can arise with such a gasket.

Preferably, the outer portion of the inner member has keying means for reception of the outer member such as to prevent relative movement between the inner and outer members.

The keying means may comprise a keying notch in the outer periphery of the outer portion bounded by a chord connecting two spaced-apart points on the periphery of the disc, may comprise radially arranged slots, may be provided by through holes or the keying means may comprise a plurality of circumferentially spaced cut-out keying notches in the periphery of the outer portion.

In another embodiment of the invention, the outer portion of the inner member has keying protuberances for engagement with corresponding recesses in the outer member, which keying protuberances can comprise spaced-apart annular ribs.

Further, in one embodiment, there is a mounting protrusion on at least one face of the outer part contacting surface for engagement with one of the parts. Ideally, the mounting protrusion is configured to form a force fit with the part.

The mounting protrusion may be in the form of a lip for engagement across the part and its facing surface and indeed may be a continuous lip forming on its outer surface an extension of the outermost part of the outer member.

The thickness of the annular disc-like outer member adjacent the bore may be greater than adjacent its periphery.

In one embodiment, the thickness of the annular disc-like outer member reduces gradually from the bore to its periphery.

In another embodiment of the invention, each of the outer part contacting surfaces includes a protruding ring for engagement in a corresponding annular groove in a facing surface of one of the parts. The ring may be so configured as to form a force fit in the part so as to provide the mounting protrusion.

In these latter embodiments, the thickness of the disc may reduce gradually from the bore to the protruding ring and is of substantially the same thickness from the ring over the remainder of the outer member.

Further. the invention provides a method of making a gasket oomprising:- moulding the disc-like outer member on a metal former; and moulding the disc-like inner member separately before assembling the outer and inner members and then machining the inner part contacting surfaces of the inner member.

Alternatively, the method comprises moulding the disc-like outer member on a prior moulded disc-like inner member and then machining the inner part contacting surfaces of the inner member.

Detailed Description of the Invention The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which:- Fig. 1 is a sectional view of portion of a gasket according to the invention, Fig. 2 is a front view of the inner member of the gasket of Fig. 1, Fig. 3 is a vertical section along the lines III-Ill of Fig. 2, Fig. 4 is a sectional view of an alternative construction of inner part, Fig. 5 is a sectional view of a still further construction of inner part, Fig. 6 is a sectional view of another construction of inner part, Fig. 7 is a sectional view of an alternative construction of gasket according to the invention, and Fig. 8 is a sectional view of another gasket according to the invention.

Referring to the drawings and initially to Figs. 1 to 3, there is provided a gasket, indicated generally by the reference numeral 1, comprising an annular rigid disc- like inner member 2 and an annular elastic disc-like outer member 3. The inner member 2 has a pair of spaced—apart inner part contacting surfaces 5 and 6 and the outer member 3 has spaced-apart outer part contacting surfaces 7 and 8. The inner member 2 has an outer portion 2(a) which projects into and is integral with the outer member 3. The outer member 3 is moulded to accept the inner member 2 which has keying means formed by a cutting away part of the inner member 3 to form a keying flat or notch bounded by a chord connecting two spaced-apart points on the outer periphery of the outer portion 2(a) and indicated generally by the reference numeral 10. A protruding ring 11 is provided in the faces 7 and 8 for engagement in corresponding annular grooves in a facing surface of a part. A mounting protrusion formed by a continuous annular lip 15 is formed as an extension of the outer member 3. The gasket includes a bore 20 in the inner member 2. The inner member 2 projects into the outer member 3 to support the outer member 3, however. it does not form, over most of its length, a facing surface. The outer member 3 tapers from the inner member 2 to the annular lip 15.

The inner part will preferably be made from any suitable rigid engineering plastics material. Materials such as ethylene-propylene (EP) or similar materials may be used.

Various elastomers such as EPDM and fluoroelastomers such as that sold under the Trade Mark RETON may be used for the elastomeric material. The material sold under the Trade Mark PEEK, which is a combination of polytetrafluoroethylene and carbon fibres with additional graphite added, can be used for the inner member.

It will be appreciated that the lip ‘I5 will ensure that the seal bore 20 is concentric with, for example, a ferrule bore. The lip 15 effectively forms a mounting protrusion which sits on the outside diameter, for example, of a ferrule. This provides support for the assembly and also ensures that the seal is always retained in position. This can be essential where hygiene is of paramount importance as this will ensure that the seal cannot fall from the ferrule during assembly or indeed on disassembly.

Ideally, one or both of the protrusions 10 then form a force-fit in a corresponding groove in a mating part. It is also envisaged that depending on the nature of the seal required. the inner member will protrude greater or lesser distances into the outer member.

The gasket may be manufactured by moulding the inner member and then using a metal former of substantially the same size and shape as the inner member, moulding the outer member on it. Then, the outer member and inner member are assembled. Finally, the inner part contacting surfaces of the inner member are machined. Alternatively, the inner member is first moulded, the outer member moulded on it and then finally, the machining is carried out. This latter method ensures that the two parts can be securely keyed together. However, in practice, the former method is often preferred in that in some instances, due to the elastomer material thermally effecting the inner member, there is some damage of the inner member. It will be appreciated that the manner of manufacture will effect the way in which the parts are keyed together. For example, when keying through holes are provided in the inner member and the former moulding method is used, through holes will not be provided in the metal former.

The advantage of this construction over those heretofore used is that the inner member 2 being made of a suitable plastics material will have the capability of sustaining a good surface finish, can be formed and machined with precision, will have good structural ability, freedom from extractables, high thermal resistance combined with low thennal expansion. Further, the plastics material can be chosen to have good erosion and corrosion resistance and to be unaffected by chemical attack by most substances. Further, the outer member 3 avoids the need to provide a gasket with a very high surface finish because it is no longer necessary with the elastomeric material which will be able to accommodate imperfections and roughness in any mating surface. Further bulging is prevented. In summary, a strong and effective gasket is provided.

Referring now to Fig. 4, there is illustrated an alternative construction of inner member, again identified by the reference numeral 2, having a plurality of annular protrusions 25 forming the keying means which, will prevent the outer member from being withdrawn radially.

Referring now to Fig. 5, there is illustrated again an alternative construction of inner member, again identified by the reference numeral 2. In this embodiment, there is provided a plurality of radially arranged slots 26 forming keying recesses for securing the outer member 3 onto the inner member 2. Keying holes 27 are also provided.

Referring now to Fig. 7, there is illustrated a still further construction of gasket, indicated generally by the reference numeral 30, in which parts similar to those described with reference to the previous drawings, are identified by the same reference numerals. In this embodiment, the inner member 2 is constructed in exactly the same way as in the embodiment of Figs. 1 to 3. However, the outer member, again identified by the reference numeral 3, is essentially a planar tapering annular disc-like seal.

Referring now to Fig. 8, there is illustrated a still further construction of gasket, indicated generally by the reference numeral 35 and the only difference between this gasket and the gasket of Fig. 1 is that the inner member, here identified again by the reference numeral 2, projects much further into the outer member, again identified by the reference numeral 3. This can clearly be seen. This would provide added rigidity and support for the gasket or seal.

The protruding ring, such as illustrated in Figs. 1 to 3, may, on its own, form the mounting protrusion.

Ideally, the thickness of the gasket reduces gradually from the bore to the protruding ring and then is of substantially constant thickness over the remainder of the outer member.

In the specification the terms “comprise, comprises, comprised and comprising" or any variation thereof and the terms “include, includes, included and including" or any variation thereof are considered to be totally interchangeable and they should all be afforded the widest possible interpretation.

The invention is not limited to the embodiments hereinbefore described but may be varied in both construction and detail within the scope of the claims.

Claims (1)

1. CLAIMS A composite gasket for sealing between facing surfaces of two contacting parts comprising a rigid annular disc—like inner member and an elastic annular disc-like outer member. the rigid annular disc-like inner member being of a tough substantially non-deformable material and comprising an inner portion having a bore and a pair of spaced-apart inner part contacting surfaces, and an outer portion projecting into and integral with the elastic disc-like outer member which is of an elastomeric material having spaced-apart outer part contacting surfaces. A gasket as claimed in claim 1, in which the outer portion of the inner member has keying means for reception of the outer member. A gasket as claimed in claim 2, in which the outer portion of the inner member is a circular disc and the keying means comprises a keying notch in the outer periphery of the outer portion bounded by a chord connecting two spaced-apart points on the periphery of the disc. A gasket as claimed in claim 2 or 3, in which the keying means comprises through holes. A gasket as claimed in any of claims 2 to 4, in which the keying means comprises a plurality of radially arranged slots. A gasket as claimed in any of claims 2 to 5, in which the keying means comprise a plurality of circumferentially spaced cut-out keying notches in the periphery of the outer portion. A gasket as claimed in any of claims 2 to 6, in which the keying means comprises keying protuberances for engagement with corresponding recesses in the outer member. A gasket as claimed in claim 7. in which the keying protuberances comprise spaced-apart annular ribs. A gasket as claimed in any preceding claim, in which there is a mounting protrusion on at least one face of the outer part contacting surface for engagement with one of the parts. A gasket as claimed in claim 9. in which the mounting protrusion is so configured as to form a force fit with the part. A gasket as claimed in claim 9 or 10, in which the mounting protrusion is in the form of a lip for engagement across the part and its facing surface. A gasket as claimed in claim 11, in which the lip is continuous forming on its outer surface an extension of the outermost part of the outer member. A gasket as claimed in any preceding claim, in which the thickness of the annular disc-like outer member adjacent the bore is greater than adjacent its periphery. A gasket as claimed in claim 13, in which the thickness of the annular disc-like outer member reduces gradually from the bore to its periphery. A gasket as claimed in any preceding claim, in which each of the outer part contacting surfaces includes a protruding ring for engagement in a corresponding annular groove in a facing surface of one of the parts. A gasket as claimed in claim 15 and any of claims 10 to 14, in which the ring is so configured as to form a force fit in the part so as to provide the mounting protrusion. A gasket as claimed in claim 15 or 16, in which the thickness of the disc reduces gradually from the bore to the protruding ring and is of substantially the same thickness from the ring over the remainder of the outer member. A method of making a gasket as claimed in any preceding claim, comprising:— moulding the disc—like outer member on a metal former; and moulding the disc-like inner member separately before assembling the outer and inner members and then machining the inner part contacting surfaces of the inner member. A method of making a gasket as claimed in any of claims 1 to 18, comprising moulding the disc-like outer member on a prior moulded disc-like inner member and then machining the inner part contacting surfaces of the inner member. A gasket substantially as described herein with reference to and as illustrated in the accompanying drawings.