GB2115503A

GB2115503A - Improvements relating to corrugated gaskets

Info

Publication number: GB2115503A
Application number: GB08205119A
Authority: GB
Inventors: Terence Peter Nicholson
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-02-22
Filing date: 1982-02-22
Publication date: 1983-09-07
Also published as: SE443036B; GB2115503B; IT1172634B; IT8312440A0; SE8300938D0; FR2522104B1; SE8300938L; FR2522104A1; DE3305887A1

Abstract

The gasket comprises a metal plate (1) having a corrugation (3) formed therein. In order to prevent beating out of the corrugation during use, a support is provided for the corrugation, e.g. a shim (4) spot welded or glued in place. The corrugation may have a double wave form, and the shim (4) may support one or both wave forms. <IMAGE>

Description

SPECIFICATION Improvements relating to corrugated gaskets The present invention relates to gaskets for internal combustion engines, particularly but not exclusively, to the type of gaskets disclosed in our patent No. 1 583 322 and in our copending application No. 2 063 386.

In general the gaskets disclosed in the abovementioned publications have proved very successful. However, there have been two occasions when after running under heavy thermal cycling conditions for many hours gas leakage has developed.

On investigation it was discovered that this leakage developed when there was substantial flexibility/excessive springiness in the cylinder head.

When a corrugated gasket is compressed the embossed corrugations when properly designed should compress to within .001 "/.002" of the base thickness of the metal from which the gasket is produced.

Consequently when a cylinder head is extremely flexible or springy it has a beating effect on the gasket when operating at full load under extreme thermal cycling conditions.

A typical cycle is for the engine temperature to rise 900 Centigrade in one minute during the one and half minutes full power running cycle, the engine is then switched to idling under load and the temperature of the engine is reduced 900 Centigrade by flushing cold water through the engine for one and a half minutes, consequently it is being subjected to enormous thermal shocks.

This beating effect on the gasket results in the minute wave form of the compressed gasket being beaten completely out of existence whence gas leakage begins to occur.

It has been found by research and development that if the corrugation is supported after it has been compressed, the problem is completely eliminated.

Thus, the invention provides a gasket comprising a metal plate having a corrugation formed therein and means for supporting the corrugation during compression.

This support may take the form of a flat or preformed metal shim of approximately .002" thick being fitted under either one or both of the corrugations surrounding each cylinder bore.

Although it is always difficult to completely generalise, it has been found that on small/light engines it is necessary, usually because of the low clamping load available, only one corrugation requires support, whereas on larger engines it is better to support both corrugations.

This applies equally to the single piece gasket of Patent No. 1 583 322 and the three piece gasket of patent application No. 2 063 386.

Embodiments of the invention will now be described with reference to the accompanying drawing, wherein: Fig. 1 is a section of part of a gasket in accordance with a first embodiment of the invention; Fig. 2 is a section of part of a gasket in accordance with a second embodiment of the invention; Fig. 3 is a section of part of a gasket in accordance with a third embodiment of the invention; Figs. 4 and 5 show modifications to the embodiment of Fig. 3.

In the Figures, a gasket 1 is shown having a cylinder-bore aperture 2. A corrugation 3 has been formed around the aperture 2 and may have a single wave form or, as shown here, a double wave form as described in our U.K. Patent No.

1 583 322.

In Fig. 1, a flat or pre-formed metal shim 4 is fixed inside one wave form 5 of the corrugation 3, e.g. by spot welding or adhesive. The thickness of the shim 4 is approximately 0.002". The shim 4 provides sufficient support to prevent the corrugation from being beaten away during use.

The embodiment of Fig. 2 shows how the shim 4 can extend across both wave forms, e.g. in larger engines where more support is required.

Fig. 3 shows the shims of Fig. 2 mounted in a gasket as described in our U.K. patent application No. 2 063 386. Briefly, there are two outer metal plates 6, 6' and a central composite plate 7 arranged therebetween. The central plate 7 comprises a central soft metal layer and hard metal layer surfaces which are bonded or integral therewith. These hard surfaces are preferably hardened by rolling after a bright annealing operation. The shims 4 may be provided in either the upper or the lower corrugations, or in both corrugations, and may be in only one wave form as in Fig. 1, or in both wave forms as in Fig. 2.

The support for both wave forms of each corrugation can be by two separate shims 4', 4" (Fig. 4) or by a single formed shim 4"' (Fig. 5).

Instead of a flat metal shim, a metal wire can be used as support means, but this is not as effective.

A supported corrugation as described above may also be provided around the periphery of the gasket.

1. A gasket comprising a metal plate having a corrugation formed therein and means for supporting the corrugation during compression.

2. A gasket as claimed in claim 1, wherein the supporting means comprises a metal shim.

3. A gasket as claimed in claim 1, wherein the supporting means comprises a metal wire.

4. A gasket as claimed in any one of the preceding claims and comprising two said metal plates, the respective corrugations extending outwardly, and a central composite plate arranged between the two said metal plates the central composite plate comprising a central soft metal layer and hard metal surface layers which are bonded or integral therewith.

5. A gasket as claimed in claim 4, wherein the surfaces of the central composite metal plate have been hardened by rolling the said surfaces after a

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements relating to corrugated gaskets The present invention relates to gaskets for internal combustion engines, particularly but not exclusively, to the type of gaskets disclosed in our patent No. 1 583 322 and in our copending application No. 2 063 386. In general the gaskets disclosed in the abovementioned publications have proved very successful. However, there have been two occasions when after running under heavy thermal cycling conditions for many hours gas leakage has developed. On investigation it was discovered that this leakage developed when there was substantial flexibility/excessive springiness in the cylinder head. When a corrugated gasket is compressed the embossed corrugations when properly designed should compress to within .001 "/.002" of the base thickness of the metal from which the gasket is produced. Consequently when a cylinder head is extremely flexible or springy it has a beating effect on the gasket when operating at full load under extreme thermal cycling conditions. A typical cycle is for the engine temperature to rise 900 Centigrade in one minute during the one and half minutes full power running cycle, the engine is then switched to idling under load and the temperature of the engine is reduced 900 Centigrade by flushing cold water through the engine for one and a half minutes, consequently it is being subjected to enormous thermal shocks. This beating effect on the gasket results in the minute wave form of the compressed gasket being beaten completely out of existence whence gas leakage begins to occur. It has been found by research and development that if the corrugation is supported after it has been compressed, the problem is completely eliminated. Thus, the invention provides a gasket comprising a metal plate having a corrugation formed therein and means for supporting the corrugation during compression. This support may take the form of a flat or preformed metal shim of approximately .002" thick being fitted under either one or both of the corrugations surrounding each cylinder bore. Although it is always difficult to completely generalise, it has been found that on small/light engines it is necessary, usually because of the low clamping load available, only one corrugation requires support, whereas on larger engines it is better to support both corrugations. This applies equally to the single piece gasket of Patent No. 1 583 322 and the three piece gasket of patent application No. 2 063 386. Embodiments of the invention will now be described with reference to the accompanying drawing, wherein: Fig. 1 is a section of part of a gasket in accordance with a first embodiment of the invention; Fig. 2 is a section of part of a gasket in accordance with a second embodiment of the invention; Fig. 3 is a section of part of a gasket in accordance with a third embodiment of the invention; Figs. 4 and 5 show modifications to the embodiment of Fig. 3. In the Figures, a gasket 1 is shown having a cylinder-bore aperture 2. A corrugation 3 has been formed around the aperture 2 and may have a single wave form or, as shown here, a double wave form as described in our U.K. Patent No. 1 583 322. In Fig. 1, a flat or pre-formed metal shim 4 is fixed inside one wave form 5 of the corrugation 3, e.g. by spot welding or adhesive. The thickness of the shim 4 is approximately 0.002". The shim 4 provides sufficient support to prevent the corrugation from being beaten away during use. The embodiment of Fig. 2 shows how the shim 4 can extend across both wave forms, e.g. in larger engines where more support is required. Fig. 3 shows the shims of Fig. 2 mounted in a gasket as described in our U.K. patent application No. 2 063 386. Briefly, there are two outer metal plates 6, 6' and a central composite plate 7 arranged therebetween. The central plate 7 comprises a central soft metal layer and hard metal layer surfaces which are bonded or integral therewith. These hard surfaces are preferably hardened by rolling after a bright annealing operation. The shims 4 may be provided in either the upper or the lower corrugations, or in both corrugations, and may be in only one wave form as in Fig. 1, or in both wave forms as in Fig. 2. The support for both wave forms of each corrugation can be by two separate shims 4', 4" (Fig. 4) or by a single formed shim 4"' (Fig. 5). Instead of a flat metal shim, a metal wire can be used as support means, but this is not as effective. A supported corrugation as described above may also be provided around the periphery of the gasket. CLAIMS

5. A gasket as claimed in claim 4, wherein the surfaces of the central composite metal plate have been hardened by rolling the said surfaces after a bright annealing operation.

6. A gasket as claimed in claim 4 or 5, wherein each outer plate has a double wave form sectional configuration in which the distance between a plane containing the apices of the two waves and a plane parallel thereto containing the base of the trough between the two waves is significantly less than the distance between the first plane and the base plane of the plate.

7. A gasket as claimed in claim 6, wherein the support means is arranged to support only one wave of the double wave form of one or both corrugations.

8. A gasket as claimed in claim 6, wherein the support means is arranged to support both waves of the double wave form of one or both corrugations.

9. A gasket as claimed in claim 8, wherein the support means comprises separate metal shims or wires for each wave of the said double wave form.

10. A gasket as claimed in claim 8, wherein the support means comprises a single metal shim formed to support both waves of the said double wave form.

11. A gasket as claimed in any one of the preceding claims, wherein the said corrugation/corrugations is/are formed round a cylinder-bore aperture.

1 2. A gasket substantially as herein described with reference to any one of the embodiments shown in the accompanying drawings.