GB1583530A

GB1583530A - Method of producing an impregnated flat gasket such as a cylinder head gasket

Info

Publication number: GB1583530A
Application number: GB1009878A
Authority: GB
Original assignee: Goetze GmbH
Current assignee: Goetze GmbH
Priority date: 1977-03-14
Filing date: 1978-03-14
Publication date: 1981-01-28
Also published as: DE2711022B2; FR2383774A1; DE2711022A1; IT1113700B; DE2711022C3

Description

(5) METHOD OF PRODUCING AN IMPREGNATED FLAT GASKET, SUCH AS A CYLINDER HEAD GASKET (711) We, GOETZE A.G., formerly Goetzewerke Friedrich Goetze A.G., a body corporate organised and existing under the laws of the Federal Republic of Germany, of Burgermeister-Schmidt-Strasse 17, 5093 Burscheid 1, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the, method by which it is to be performed, to be particularly described in and by the following statement :: The present invention relates to the pro duction of an impregnated flat gasket such as a cylinder head gasket for an internal combustion engine, consisting of a sheet of compressible material, optionally with a metal reinforcing sheet, having a number of through openings, the regions around some of the openings being impregnated to improve the sealing efficiency or resistance to attack of the compressible material.

Cylinder head gaskets for internal combustion engines frequently consist of a fibrous material, such as an asbestos fibre sheet, which is reinforced if necessary with one or more embedded or superposed metal sheets. The asbestos fibres are moveover bonded to form a non-woven asbestos fibre fabric, generally by employing natural or synthetic rubber as a bonding agent.

In practice, such cylinder head gaskets are impregnated over their entire area or only partially, above all in order to increase their strength and sealing efficiency. Thus, for example, it is known from German Patent Specification 1,072,032 to carry out such an impregnation exclusively in the zone of one or more openings. According to the method indicated in German Patent Specification 1,072,032, this impregnation is so carried out by the method of local saturation with substances of the soft rubber type or the like that the pores of the compressible material are permeated or only enriched with these agents.In the case of enrichment, unfilled pores are left in the compressible material, so that media under pressure, such as hot combustible gases, cooling water or lubricating oil, acting precisely from the cut edges of the through openings, can penetrate into the compressible material and optimum cross-sectional fluid-tightness would no longer exist. On the other hand, according to German Laidopen Pending Patent Application 2,304,505, the edges of the combustion chamber openings in an impregnated flat gasket of compressible material are preferably protected by metal flanges and, precisely because of the increased stress occurring here due to increased pressure and hot combustion chamber gases, it is advantageous to keep the areas below these flanges free from impregnating agent.

In accordance with the present invention there is provided a method of producing an impregnated flat gasket comprising a sheet of compressible material with a number of through openings, the regions around some of the openings being impregnated to improve the sealing efficiency or resistance to attack of the compressible material wherein a stack comprising a single gasket to be impregnated or a number of such gaskets of the same dimensions is clamped between two masking plates having openings aligned with the through openings around which the gasket material is to be impregnated, the clamped stack is immersed in a bath of impregnating agent, the impregnating agent is hardened and at least one of the openings in each gasket which was masked against impregnation is fitted with a metal flange to protect the compressible material.

Preferably the masking plates have the outer contours of the gaskets and have openings of the same size and position as the through openings around which the gasket material is to be impregnated.

In the use of the method for producing cylinder head gaskets the combustion chamber openings are masked against impregnation and subsequently fitted with metal flanges. By tightly clamping the gaskets between the masking plates, the result is obtained that all the gaskets rest securely one on top of the other and no impregnating agent passes between the sealing surfaces in contact in the following immersion operation. In this ready clamped stack of gaskets, the through openings to be impregnated form a cylinder open on the outside, while all the other through openings are masked on the outside.

During the following immersion process, the impregnating agent therefore merely penetrates into the compressible material from the cut edges of the unmasked through openings. How far the agent pentrates into the areas surrounding these openings depends on the nature of the impregnating agent and of the compressible material and on the time of immersion. In order if necessary to accelerate the peneration of the medium from the cut edges and in order if necessary to cause the agent to penetrate further, a pessure may be applied to the impregnating agent during the immersion process. Generally, an impregnation of about 1 to 6, preferably 2 mm, starting from the cut edges is sufficient. However, the impregnation may penetrate further into the sealing surfaces.Preferably, only the zones around the openings for the lubricating oil and the coolant are impregnated, but the areas around the combustion chambers, which are flanged later on, remain free.

Moreover, during the immersion process, impregnating agent also penetrates into unprotected cut faces of the outer contours of the gaskets. If necessary, these faces may be sealed prior to immersion, for example by sheathing them with a coating of plastic. Enclosures, in particular flanges at the edges of the combustion chambers, would project above the sealing surfaces and gaps into which the impregnating agent could flow would be created in the stack of gaskets between the individual sealing surfaces. It is therefore expedient to apply these enclosures only after immersion.

Moreover, organic, synthetic, completely polymerisable liquids preferably serve as impregnating agents, so that during the following, preferably thermal, harding process no escaping vapours cause swelling of the compressible material. Curing agents may be added to the impregnating agent.

The method according to the invention and the cylinder head gasket produced thereby offer both economic and technical advantages. As a result of the stacking according to the invention, gaskets can be impregnated simultaneously in large numbers. Moreover, the impregnation according to the invention extends only to the partial areas of the gaskets of which a special sealing efficiency is demanded, so so that material is saved with a beneficial effect on cost.

Moreover, the impregnating agent penetrates uniformly into the compressible material solely from the cut edges. From this direction, however, the attack of the coolants and lubricating oils, which are generally under pressure, also takes place during operation, so that more effective sealing or cross-sectional fluid-tightness is available in the finished gasket. The impregnation starting from the cut edges of the outer contours of the cylinder head gasket is also a certain advantage. These zones open on the outside in the installed state of a gasket in the engine. Impregnation caried out thereat therefore produces increased strength and resistance and, consequently, special protection.

The method according to the invention will be described in detail with reference to an embodiment.

Ten finish-stamped cylinder head gaskets with the same dimensions, consisting of a 0 8 mm thick sheet of non-woven asbestos fibre fabric and a rough metal sheet as a reinforcing insert, are stacked congruently and tightly clamped between two sheet-steel plates. The plates have the form of a template or pattern of substantially the size of the cylinder head gaskets and have cutouts, so that after the clamping operation all the sealing surfaces except for the through openings for lubricating oil and cooling water which are to impregnated are covered.

The stack of gaskets is then immersed in a bath of viscous polybutadiene (Mg 1500) and 12 parts of mineral oil. After about 5 minutes, the impregnating agent has penetrated about 2 mm into the gaskets from the exposed cut edges thereof. The stack of gaskets is then removed and opened up and the impregnating agent is cross-linked thermally in an oven at about 1300C over a period of about 3 hours. The flanging of the combustion chamber openings is carried out following this or, if necessary, even before the heating of the impregnating agent.

The drawing shows in partial plan view an embodiment of a flat gasket produced by the method according to the invention.

The cylinder head gasket 1 consists of a metal-reinforced asbestos fibre sheet 2. It contains openings for the combustion chamber passages 3, the lubricating oil 4, the coolant 5 and the fixing bolts. The impregnating agent has penetrated about 2 mm into the soft material 7 around the coolant and lubricating oil openings 4 and 5, starting from the cut edges. The combustion-chamber and bolt openings 3 and 6 are free from impregnating agent in the areas surrounding them. The combustion chamber openings 3 are covered by an enclosing flange 8. Impregnating agent has also penetrated to a distance of about 2 mm starting from the cut edges 9 of the outer contours of the cylinder head gasket 1.

WHAT WE CLAIM IS:- 1. A method of producing an impregnated flat gasket comprising a sheet of compressible material with a number of through openings, the regions around some of the openings being impregnated to improve the sealing efficiency or resistance to attack of the compressible material wherein a stack comprising a single gasket to be impregnated or a number of such gaskets of the same dimensions is clamped between two masking plates having openings alinged with the through openings around which the gasket material is to be impregnated, the clamped stack is immersed in a bath of impregnating agent, the impregnating agent is hardened and at least one of the openings in each gasket which was masked against impregnation is fitted with a metal flange to protect the compressible material.

2. A method as claimed in claim 1 applied to the production of cylinder head gaskets, wherein the combustion chamber openings are masked against impregnation and subsequently fitted with metal flanges.

3. A method as claimed in claim 2 in which the impregnation is confined to through openings for lubricating oil and cooling water.

4. A method as claimed in claim 1, 2 or 3 in which the masking plates are steel sheets with the dimensions of one of the gaskets and having punched out openings corresponding in size and position to the through openings of the gasket around which the compressible material is to be impregnated.

5. A method as claimed in any of the preceding claims in which the impregnating agent is subjected to static pressure during the immersing of the stack.

6. A method as claimed in any of the preceding claims in which the impregnation is carried out with a fully polymerizable synthetic organic liquid, including curing agents of required.

7. A method as claimed in any of the preceding claims in which the impregnation extends to a distance of between 1 mm and 6 mm from the periphery of each of the through openings.

8. A cylinder head gasket produced by the method of any of the preceding claims.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. also penetrated to a distance of about 2 mm starting from the cut edges 9 of the outer contours of the cylinder head gasket 1. WHAT WE CLAIM IS:-

1. A method of producing an impregnated flat gasket comprising a sheet of compressible material with a number of through openings, the regions around some of the openings being impregnated to improve the sealing efficiency or resistance to attack of the compressible material wherein a stack comprising a single gasket to be impregnated or a number of such gaskets of the same dimensions is clamped between two masking plates having openings alinged with the through openings around which the gasket material is to be impregnated, the clamped stack is immersed in a bath of impregnating agent, the impregnating agent is hardened and at least one of the openings in each gasket which was masked against impregnation is fitted with a metal flange to protect the compressible material.