GB2193270A - Shaft seal - Google Patents

Abstract

An end plate assembly comprises a main body 20 having an aperture 21 into which a sealing element 24 is disposed. The sealing element 24 is formed integrally of the main body 20, and may be housed in a slot 23 defined in surface which defines the aperture 21 and may be secured in place by clamping a portion 25 to bite into the element 24, or alternatively by a moulding or casting operation. <IMAGE>

Description

SPECIFICATION Shaft seals The invention relates to seals for shafts and in particular to an end plate assembly construction for use with apparatus in which a moveable cylindrical shaft is disposed within a housing and extends through an orifice of a fluidtight seal in an end plate assembly mounted on the housing.

The invention relates, but not exclusively, to end plate assemblies for use with internal combustion engines. Normally, the end plate is bolted to the engine casing and provides a fluid-tight seal around a shaft which emerges from within the casing. In a more general sense the invention is capable of application in end plate assemblies which require a seal around a reciprocating shaft and/or rotating shafts to be provided.

The general type of end plate assembly to which the invention may be applied comprises a main body having means for attachment to a housing, an aperture in the main body, and an annular seal mounted within the aperture which includes a sealing element which in use, provides a fluid-tight seal around a shaft which projects there through.

End plate assemblies of this kind are in common use in the automotive industry where they are used on internal combustion engines.

The common practice has been to form the seal as a separate sub-assembly so that this can be mounted in an end plate, usually by press fitting, before the end plate is fitted to the engine. The seal subassembly would normally comprise an annular metal case having a generally L-shaped section, -and an annular sealing element mounted within the annular metal case. The sealing element would normally be made of PTFE or other suitable elastomer and is held in place by being clamped between a metal inner shell and an annular gasket bearing against the radial flange of the annular metal case.

With such assemblies, the end plate and the seal sub-assembly are normally supplied as separate units to a motor manufacturer, who would then press fit the seal into the end plate before it is assembled onto the engine.

It would normally also be necessary for the motor manufacturer to provide a seal, usually of mastic, between the end plate and the engine casing.

The time taken to order to perform these operations adds to the total cost, and there is also a risk that the seal sub-assembly will not be properly fitted to the end plate. Furthermore, should the seal fail during the subsequent life of the vehicle it is necessary to remove the seal sub-assembly and press fit a new one into the end plate, this operation again involves significant cost and carries the risk of incorrect fitting.

The present invention sets out to provide an improved form of end plate assembly which may be simpler and less costly to manufacture, fit or replace. The invention also provides a method of manufacture of such an assembly.

According to the invention, an end plate assembly comprises a main body having means for attachment to the housing of an apparatus, an aperture formed in the main body, and an annular seal mounted within the aperture and including an annular resilient sealing element, wherein the annular resilient sealing element is mounted directly on or adjacent to the portion of the main body which defines the aperture.

Thus, according to the invention, the seal is integral of the end plate assembly and does not comprise a separate sub-assembly which is mounted in the end plate. This has the advantage that an end plate assembly in accordance with the invention is simply supplied to the motor manufacturer as a unit and may thus be simply assembled onto the engine casing. The time taken in the assembly operation is, therefore, reduced and the risk of the seal being incorrectly fitted in the end plate is significantly reduced if not removed.

The peripheral portion of the annular resilient sealing element may be fitted into a recess in the main body of the end plate. The recess may circumferentially extend around the aperture and be provided with means to allow the sealing element to be secured in the recess in fluid-tight manner.

The means for securing the sealing element in the recess may, for example, comprise an annular member which is used to clamp the peripheral portion of the sealing element against a surface of the recess.

Preferably the annular member is formed integrally with- the main body, the member and surface of the recess defining an annular slot in which the peripheral portion of the sealing element is received. In this case the sealing element is secured in the main body by deformation of the annular member towards the surface of the recess.

Alternatively or additionally to being clamped within the annular slot, the peripheral portion of the sealing element is bonded to a surface or surfaces within the slot. The bonding may be effected by means of an adhesive, or by means of the material of the main body being moulded or cast around the sealing element.

This type of arrangement would normally be used, for example, where the main body of the end plate is moulded fr6m a high temperature plastics material. However, conventionally, end plates have been pressure die-cast from steel or a suitable alloy, ip which case bonding would be achieved by use of an adhesive.

In order to improve the bonding of the sealing element to the main body, the peripheral portion of the sealing element may be formed with-spaced apertures into which the adhesive may flow or the material of the main body may flow during moulding or casting thereof.

In accordance with any of the above aspects of the invention the end plate assembly may be provided with two or more sealing elements which may be mounted directly onto the main body. In this case the sealing elements would be axially spaced apart within the aperture.

As previously mentioned, it is necessary to provide a fluid-tight seal between the end plate and the casing onto which it is mounted.

In-an end plate assembly according to the present invention, the assembly may be provided with a further sealing element on a face thereof. The further sealing element would normally surround and be spaced from the aperture and in use would provide the required fluid-tight seal between the end plate assembly and the housing on which it is mounted.

The incorporation of the further seal with in the end plate simplifies the assembly of the end plate assembly onto the engine casing since the end plate can be -applied to the casing as a unit and would not require the application of a mastic or other means-of sealing as a separate operation.

The further sealing element may comprise a gasket bonded to or formed on a surface of the main body of the end plate assembly. The gasket may for example be screen-printed onto the end plate by a system marketed under the Registered Trade Mark "DOWPRINT".

As previously mentioned, the invention relates to end plate assemblies for use with the main casing of an internal combustion engine.

In this type of arrangement-the shaft which would project through an aperture in the end plate and be surrounded by the sealing ele ment is the-crankshaft of the engine.

If this is the type of end user envisaged the means for mounting the end plate assembly on the casing may comprise holes in the main body part of the assembly to allow mounting bolts to pass there through and correctly lo cate the assembly ip position.

The invention also includes a method of manufacturing an end plate assembly which includes the- steps of: (a) forming a main body having an aperture, (b) forming- in a surface which defines the aperture annular slot, (c) locating in the slot a peripheral portion of a sealing element, and (d) deforrning the material of the main body, adjacent to the aperture so as to clarnp the peripheral portion of the seal ing element within the slot.

In an alternative method, an end plate as semb!y having an aperture, is manufactured by a method which includes the steps: (a) locat ing a sealing element in-a mould so that its periphqral portion projects into the portion of the mould which will define the aperture, and (b) moulding or casting the main body thereabouts, whereby, the peripheral portion of the sealing element becomes embedded in the material of the main body.

The invention will now be illustrated by way of example with reference to the accompanying drawings in which; Figure 1 is a diagrammatic front elevation of prior art end plate assembly, Figure 2 is a part-section showing the construction of the seal sub-assembly used in the end plate of Figure 1, Figure 3 is a diagrammatic section through an end plate assembly according to the invention, Figure 4 is a similar view through an alternative form of assembly according to the invention, and Figure 5 is a diagrammatic front elevation of an end plate assembly in accordance with the invention.

Referring to Figures 1 and 2, there is shown a typical prior art end plate assembly for providing a fluid-tight seal for the crankshaft of an internal combustion engine.

The assembly comprises a main body 10, which is made by a pressure die-cast method from steel, and an annular seal sub-assembly 11.

The main body 10 is provided with holes 12 around its outer edge which enable it to be bolted to the engine casing. Further it is formed with a large circular aperture 13 surrounded by a raised ridge 14.

The seal sub-assembly (see Figure 1) comprises an annular, generally L-sectioned metal case 15 within which is located an annular Lsectioned inner shell 16. An annular gasket 17 of compressed asbestos fibre or silicon overlies the inner radial surface of the metal case 15 and an annular resilient sealing element 18 of PTFE has its outer peripheral portion clamped between the radial flange of the inner shell 16 and the gasket 17. The seal subassembly 11 is press fitted within the circular aperture 13 of the end plate and, in use, the inner peripheral portion of the sealing element 18 embraces the outer surface of the engine crankshaft, indicated at 19.

The disadvantages of the prior art end plate assembly of the kind shown in Figures 1 and 2 have been discussed above.

Referring now to Figures 3 and 5, the main body 20 of the end plate assembly according to the invention is, in general similar to the corresponding prior art assembly so that it may simply replace the prior art type of assembly on an existing engine design. The main body 20 is formed with a central circular aperture 21 having a resilient sealing element directly mounted therein.

Referring to Figure 3, the inner surface 22 of the main body 20, which defines the aperture 21, is provided with a peripheral slot 23.

Received in the slot is the outer peripheral portion of an annular PTFE sealing element 24.

Initially, the slot 23 is parallel-sided. However, after introduction of the outer periphery of the sealing element 24, a portion 25 of the main body which defines one side of the slot 23 is deformed so as to bite into and clamp the sealing element 24 in place. The deformation of the portion 25 may be effected by a press operation, a spinning operation or by any other suitable method.

Figure 3 shows the end plate assembly in use, bolted onto a casing 26 of an engine by means of bolts 27. The inner periphery of the sealing element 24 engages the outer surface of engine crankshaft 28 to provide a sealing contact.

In order to ensure a fluid-tight seal between the end plate and the engine casing 26 is achieved, a gasket 33 is screen-printed onto the rear surface of the end plate by a system marketed under the Registered Trade Mark "DOWPRINT".

With the inner resilient sealing element 24 and the gasket 33 directly mounted on the end plate, the end plate assembly may be supplied to a motor manufacturer or repairer as a complete unit which may then be simply fitted or replaced.

Figure 4 shows an alternative arrangement where, the main body 29 of the end plate assembly is moulded from high temperature plastics and the peripheral portion of a PTFE sealing element 30 is bonded into the inner peripheral surface of the body- part at a position 31, during the moulding, as previously described. Spaced holes 32 may be formed around the outer periphery of the sealing element 30 so that, during the moulding process, the moulding material flows into the holes so as to more securely anchor the sealing element to the'end plate.

It will be appreciated that the invention is not limited to the particular configuration of the components described above, which are shown only diagrammatically in the drawings, nor is the invention limited to the particular materiais referred to. It will be apparent to those skilled in the art what other configurations and materials could be employed in the realisation of the invention.

Claims (11)

1. An end plate assembly comprises a main body having means for attachment to the housing of an apparatus, an aperture formed in the main body, and an annular seal mounted within the aperture and including an annular -resilient sealing eiement, wherein the annular resilient sealing element is mounted directly on or adjacent to the portion of the main body which defines the aperture.

2. An end plate assembly -as claimed in claim 1, which further includes an annular member which is formed integrally with the main body, the member and surface of the recess defining an annular slot in which the peripheral portion of the sealing element is received.

3. An end plate assembly as claimed in claim 2. in which the peripheral portion of the sealing element is bonded to a surface or surfaces within the slot.

4. An end plate assembly as claimed in any one of the preceding claims, in which two or more sealing elements are mounted directly on to the main body.

5. An end plate assembly as claimed in any one of the preceding claims, in which the assembly is provided with a further sealing element on a face thereof.

6. An end plate assembly as claimed in claim 5 wherein a further sealing element comprises a gasket bonded to or formed on a surface of the main body of the end plate assembly.

7. A method of manufacturing an end plate assembly which includes the steps of: (a) forming a main body having an aperture, (b) forming in a surface which defines the aperture annular slot around the peripheral thereof, (c) locating in the slot a peripheral portion of a sealing element, and (d) deforming the material of the main body adjacent to the aperture so as to clamp the peripheral portion of a sealing element within the slot.

8. A method of manufacturing an end plate assembly which includes the steps of: (a) locating a sealing element in a mould so that its peripheral portion projects into the portion of the mould which will define the aperture, and (b) moulding or casting the main body thereabouts whereby, the peripheral portion of the sealing element becomes embedded in the material of the main body.

9. An end plate assembly substantially as hereinbefore described with reference to Figure 3 of the drawings.

10. An end plate assembly substantially as hereinbefore described with reference to Figure 4 of the drawings.

11. An end plate assembly substantially as hereinbefore described with reference to Figure 5 of the drawings.