GB2101239A

GB2101239A - Gasket assembly and method of making same

Info

Publication number: GB2101239A
Application number: GB08220022A
Authority: GB
Inventors: Robert S Pearlstein
Original assignee: Felt Products Mfg Co LLC
Current assignee: Felt Products Mfg Co LLC
Priority date: 1981-07-10
Filing date: 1982-07-09
Publication date: 1983-01-12
Also published as: SE450730B; GB2101239B; FR2509414B1; SE8204206D0; DE3225420A1; JPS5817258A; MX154072A; SE8204206L; FR2509414A1; JPH041232B2

Abstract

A cylinder head gasket assembly for an internal combustion engine has at least one combustion opening and a plurality of other apertures, and comprises an expansive metallic core (14) and an expansive, substantially coextensive facing layer (16) secured to each face of the core. A deformable sealing pattern is provided comprising one or more beads (30) confronting the core face and lies intermediate the core face and the facing layer, so that the core (14) and facing layer (16) envelope the beads. The sealing pattern surrounds the combustion opening and some of the apertures. The sealing pattern is adhered to the core (14), and the facing layer (16) is adhered to the core by adhesive under pressure in a zone closely surrounding the sealing pattern and bead to restrict lateral movement of the sealing pattern and to compress and densify the facing layer in the zones overlying the sealing pattern to enhance the sealing characteristics of the gasket assembly. <IMAGE>

Description

SPECIFICATION Gasket assembly and method of making same The present invention relates to gaskets for example cylinder head gaskets for internal combustion engines.

Laminated head gaskets having a central metallic core and one or two facing sheets with sealing patterns applied to the facing sheets have become increasingly important in the sealing of internal combustion engines. Most frequently the sealing patterns are applied by a silk screening process.

For a number of reasons, the facing sheets usually require the application of coatings or surfacings in addition to the sealing patterns, thereby to enable the gasket to resist fretting corrosion, abrasion and disturbance or destruction of the sealing pattern. Because the sealing patterns are frequently difficult to adhere to pretreated facing sheets, i.e. surface treatments which may be beneficial for the facing but which may impede curing or adherence, it is frequently necessary to apply the sealing patterns, and thereafter apply a coating or surfacing to the gasket facing sheet, sometimes without coating the sealing pattern. That is considerably more difficult and more expensive and sometimes less effective, than if the coating, surfacing or treatment were applied first and the sealing pattern was thereafter applied.

It is an object of the present invention to eliminate such impediments to the inexpensive and more effective manufacture of gaskets bearing sealing patterns.

According to the invention, there is provided a gasket assembly for location between a pair of surfaces to be sealed comprising a metallic core, a sealing pattern adhered to the core, a facing layer secured to the core and overlying the sealing pattern so that said sealing pattern is enveloped between said core and said facing layer, whereby in use the sealing pattern of the gasket is protected from direct contact with the surfaces to be sealed and at least one opening in the gasket assembly about which the sealing pattern is disposed.

When such a head gasket assembly is placed in compression between a head and a block, the sealing pattern is protected from direct contact with a head and block, hence from abrasion, heat and extrusion.

A gasket assembly of this invention may thus comprise a head gasket assembly for an internal combustion engine. The gasket assembly is adapted to be disposed between the head and the block of the engine. The gasket assembly defines at least one combustion opening and preferably also a plurality of apertures for oil and water.

The metallic core is preferably expansive. The facing layer secured to a face of the core is preferably substantially coextensive with the core and preferably there is a facing layer secured to each face of the core.

The sealing pattern may comprise one or more beads confronting the core face lying intermediate the core face and the facing layer so that the core and facing layer envelop the beads.

Preferably the sealing pattern is elastomeric and surrounds the combustion openings and one or more of the apertures enhancing the sealing effect of the gasket assembly in the zone of the beads of sealing pattern.

The sealing pattern is adhered to the core, and the facing layer is adhered to the core preferably by adhesive under pressure in a zone closely surrounding the sealing pattern and bead. This may restrict lateral movement of the sealing pattern and may stiffen the sealing pattern when the gasket assembly is placed in compression.

Further it may compress and densify the facing layer.

The invention may be carried into practice in various ways and one embodiment will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a top plan view of a gasket assembly incorporating the principles of the present invention; Figure 2 is a fragmentary, cross-sectional view of a diesel engine employing the gasket assembly shown in Figure 1; Figure 3 is a fragmentary plan view of the core of the gasket assembly of Figure 1 with a sealing pattern applied thereto; Figure 4 is a fragmentary plan view, similar to Figure 3, of the gasket assembly of Figure 1; Figure 5 is an enlarged cross-sectional view taken substantially along the line 5-5 of Figure 4; and Figure 6 is an enlarged fragmentary view of a portion of Figure 5 after it is pre-compressed.

Referring to the drawings, a diesel engine 1 having a head 2 and a block 3 is illustrated employing a gasket assembly 10. Block 3 is seen to include a cylinder opening 4, a cylinder sleeve 5 and a piston 6. Engine 1 has a plurality of combustion cylinders 4 only one of which is shown in Figure 2. Although gasket assemblies made in accordance with this invention can be employed with an engine having only one combustion opening, the invention will be illustrated by a multi-combustion opening gasket assembly and engine.

Gasket assembly 10 is a laminate, and is seen to comprise a generally flat, solid expansive metal core 14 and a pair of generally flat expansive facing sheets 1 6. Core 14 comprises upper and lower flat or planar faces, such as surfaces 1 8, to which facing sheets 1 6 are laminated. The core may also be coined, embossed, or may be otherwise surface modified, as by etching, in desired locations.

Facing sheets 1 6 are formed of a composite compressible gasket facing material and may be fiber reinforced. They are laminated mechanically or adhesively to the surfaces 18, as by a suitable heat-activated adhesive. Suitable heat activatable adhesives include phenolic-nitrile rubber and polybutyral rubber which is desirable initially applied to the facing sheet surfaces. The facing sheets may incorporate asbestos, glass fibers, or other suitable fibrous materials, and may utilize nitrile, neoprene or polyacrylic elastomers as a binder. Frequently the binder comprises from about 15 to about 25% of the facing sheet, whether asbestos fibers, or whether other organic or inorganic fibers, fillers or the like are used.In the embodiment illustrated, the facing sheets 1 6 have a thickness of about 0.025 inch (0.635 mm), although, of course this may vary with the application. Facing sheets 1 6 generally resist degradation by oils and coolants, retain torque, minimize extrusion, and exhibit heat resistance.

The gasket assembly 10 is die-cut or blanked out, such as with a stamping machine, punch press or other suitable form of equipment to provide combustion openings, 20, and apertures, such as bolt holes 22, and a plurality of fluid flow passageways, such as oil and water passageways 24. The core may be of cold, rolled steel and its thickness may vary with the application.

Thicknesses of about 0.006 to 0.050 inch (0.15 to 1.3 mm) are typical. To enhance adherence, the core surfaces 1 8 may be phosphatized, i.e., coated with a phosphate coating, in a conventional manner, or may be otherwise surface treated to improve adhesion.

In the embodiment illustrated, core 10 defines an embossment 21 surrounding combustion opening 20. Gasket assembly 10 may then be provided with annular armouring 25 secured about embossment 21 in a known manner to help seal the combustion opening.

In the present embodiment, the desired sealing pattern 26 is disposed on and secured to one or both surfaces of the core. The sealing pattern 26 may comprise a series of sealing beads 28, 30 applied to those zones in which increased or augmented sealing forces are required in the application for which the gasket assembly 10 is to be used. Typically the beads 28 are formed substantially to surround the combustion opening, and beads 30 are formed substantially to surround water and oil passages between the associated head and block. At times, because of the configuration of the head and block, and the location of the bolt holes, or for other design reasons, less than a circular or completely encircling bead configuration is required, as is illustrated by Figures 1 and 3.

In the embodiment illustrated the sealing pattern 26 forming beads 28 and 30 may be formed of a silicone sealant which is preferably deposited by a silk-screening process, typically as described in United States Patent 3,477,867, with a height at the high point of the bead of about 0.006 to 0.008 inch (0.15-0.2 mm). The silicone may be a two-component, heat curable liquid silicone. When the sealing beads are deposited and adhered to the dimensionally stable, highly adherent core, they may be precisely, accurately and consistently located from gasket to gasket.

After the sealing pattern is deposited and cured in a known manner on the faces 18 of core 14, compressible facing sheets 1 6 are positioned to overlie the core and sealing pattern are laminated to the core as by a conventional intervening adhesive layer. The adhesive adheres the facing layer to the core and when the core and layers are laminated under pressure, the facing layer is compressed and densified in the zone of the sealing pattern. When the core is phosphatized, or otherwise suitably treated to enhance bonding, the facing sheets 1 6 will adhere readily and securely to the core surfaces and, depending upon the sealant comprising the sealant pattern 26, may or may not adhere to the beads 28 and 30. In any event, the facing sheets and metal core envelop and surround the sealing beads.

Desirably the facing layer is secured to core surface 1 8 in a zone Z which closely surrounds the beads, thereby to confine the bead and to prevent substantial movement of the sealing pattern and beads laterally when the gasket assembly is placed in compression. The envelopment of the beads has a number of advantages. Among those are that movement or extrusion of the bead, when elastomeric, is restricted, thus enhancing the load bearing capacity of the bead. When the facing layer and core very closely surround the bead, not only is extrusion restricted, but the elastomeric beads tend to display a somewhat stiffer load deflection curve than would the same beads if they were exposed on the surface of the facing sheet, as is conventional.Thus, under compression, bead compression tends to be limited to some embedment in the lower, internal surface of the facing sheet, but without extrusion all so that a bead and the overlying facing can act as a seal under greater compression loads and more effectively than previously possible.

When gaskets employing sealing patterns on their surfaces are used, it is necessary initially to substantially fully embed the sealing pattern in the facing layer before any load is applied in other areas of the gasket. However, with the gasket of the present invention depending upon the precompression in the zones of the enveloped beads, the application of load in zones other than bead zones may take place substantially immediately. When the bead pattern is substantially incompressible, as for example are elastomers such as silicones and other rubbers, and when the gasket is compressed in the bead or sealing pattern zones, either in use or during the manufacturing process, the facing material overlying the sealing pattern becomes densified and, to the extent it was somewhat porous, tends to become even more impervious to the passage of fluids. Thus, the facing material in that zone has enhanced sealing properties and physical characteristics which are different from those in the areas immediately adjoining the bead and sealing pattern zones.

In Figure 5, the gasket is illustrated prior to compression in the sealing pattern and bead zones. However, during manufacture the gasket is preferably compressed in those zones, such that the facing layers are densified as illustrated in Figure 6. There the silicone bead 28 is shown to have been embedded in the facing layer 1 6 and the facing layer in the zone of the bead has been compressed. The height Y of the bead which was substantially equal in Figure 5 to the projection of the facing layer in the zone of the bead, in Figure 6 has become substantially diminished as shown by height X. Desirably the ratio of heights X to Y is no greater than about 1:2, i.e., about one-half, and preferably less.As such the surface of the gasket assembly is more nearly flat than one in which the bead is on the surface, enhancing sealing characteristics of the gasket over its entire surface.

Yet another advantage deriving from the gasket assembly of this invention is that the bead is protected, not only from extrusion, but from surface phenomena. Such phenomena comprise disruption or disturbance of the beads during shipping, handling and installation, as well as the tendency to disruption or destruction of the bead in use in the engine. Such disruption may be due to rough mating surfaces to be sealed wherein the tendency to split or fracture the bead due to the rough finish is high. Furthermore, it is known that excessive heat tends adversely to affect elastomeric sealing beads. By enveloping them, as described, the sealing pattern is insulated from the adverse aHects of heat much more than when the pattern is at the surface of the gasket assembly.

Additionally, in some environments fretting erosion of the beads occurs. Although facings may be treated to withstand fretting corrosion, it has been very difficult to treat sealing beads, such as silicone beads, with materials which will resist fretting, in part because of the difficulty of adhering a suitable protective layer to the beads.

Also, as has already been mentioned, when the sealing pattern is not on the surface, it becomes possible easily and inexpensively to apply antifretting coatings and other surface treatments to an entire facing surface, all without compensating for such treatments, or utilizing additional steps in the manufacture of the gasket assembly. And, by applying the sealing pattern to the core, rather than to the facing sheets, it becomes unnecessary to precoat the facing sheets with special barrier coat materials to facilitate the curing of bead materials, such as silicones, special materials which are now frequently necessary because of the tendency of the facing material itself to inhibit curing. The gaskets of this invention also make it possible to provide improved control of cylinder head distortion.

Although the sealing pattern and beads have been described as being of a silicone elastomer, other elastomers and resilient materials may be used as well, and these include nitrile (polybutadiene-nitrile rubber) or neoprene rubbers, epoxies, such as flexible and rubber modified epoxies, or combinations of them. Further, because the bead and facing sheet cooperate in the transmission of sealing forces in the zones of the bead it is possible to consider the use of somewhat stiffer materials which are not necessarily elastomeric to effect seals in some or all of the locations at which sealing is to be effected via the agency of the beads. The tendency towards embedment of the sealing bead in the facing sheet will also tend to promote sealing conformance of the facing sheet surfaces with the head and block in a manner in which they would not were the beads at the outer surfaces as is now conventional.

In the embodiment described the sealing pattern and beads are bonded to the core, and the facings to the core. Depending upon the materials involved, it may also be desirable to bond the beads to the facing as well during the lamination process.

Claims

1. A gasket assembly for location between a pair of surfaces to be sealed comprising a metallic core, a sealing pattern adhered to the core, a facing layer secured to the core and overlying the sealing pattern so that said sealing pattern is enveloped between said core and said facing layer, whereby in use the sealing pattern of the gasket is protected from direct contact with the surfaces to be sealed and at least one opening in the gasket assembly about which the sealing pattern is disposed.

2. A gasket assembly as claimed in Claim 1 in which the facing layer is secured to the core in a zone closely surrounding the sealing pattern to prevent substantial movement of the sealing pattern laterally when the gasket assembly is placed in compression.

3. A gasket assembly as claimed in Claim 2 in which the sealing pattern is of an elastomeric material which is deformable under compression and the facing layer restricts deformation of the sealing pattern.

4. A gasket assembly as claimed in any preceding claim in which the gasket assembly defined at least one opening which the sealing pattern entirely surrounds.

5. A head gasket assembly for an internal combustion engine adapted to be located between the head and the block of the engine, the gasket assembly defining at least one combustion opening and a plurality of apertures, the assembly comprising an expansive metallic core and an expansive, substantially coextensive facing layer secured to an expansive face of the core, a deformable sealing pattern confronting the core face and lying intermediate the core face and the facing layer, the sealing pattern surrounding at least one of the opening and the apertures for enhancing the sealing effect of the gasket assembly in the zone of the sealing pattern, whereby when the head gasket is placed in compression between a head and a block, the sealing pattern is protected from direct contact with the head and block.

6. A head gasket assembly as claimed in Claim 5, in which the sealing pattern is elastomeric and surrounds at least one of the apertures.

7. A head gasket assembly as claimed in Claim 5 or Claim 6 in which the sealing pattern surrounds a combustion opening.

8. A head gasket assembly as claimed in Claim 7 in which the sealing pattern is adhered to the core and the facing layer is adhered to the core in a zone closely surrounding the sealing pattern, thereby to prevent substantial movement of the sealing pattern laterally when the gasket assembly is placed in compression.

9. A head gasket assembly for an internal combustion engine constructed and arranged substantially as herein specifically described with reference to and as shown in the accompanying drawings.

10. A method of making a gasket assembly for location between a pair of surfaces to be sealed, the steps comprising disposing a sealing pattern on the surface of a metallic core; positioning a compressible facing layer over the core and the sealing pattern so that the sealing pattern is enveloped between the core and the facing layer, the gasket assembly defining at least one opening about which the sealing pattern is disposed, and adhering the facing layer to the core under pressure so that the facing layer is compressed and densified in the zone of the sealing pattern, whereby in use the sealing pattern of the gasket is protected from direct contact with the surfaces to be sealed.

11. A method as claimed in Claim 10 in which the facing layer is adjered to the core in a zone closely surrounding the sealing pattern to prevent substantial movement of the sealing pattern laterally when the gasket assembly is placed in compression, thereby to control compression of the facing layer when it is compressed under pressure.

1 2. A method as claimed in Claim 10 or Claim 11 in which the facing layer is compressed under pressure during adhering so that the height of the projection of the facing layer above the sealing pattern is no greater than about one-half of the height of the sealing pattern.

13. A method as claimed in any of Claim 10 to 12 in which the step of disposing the sealing pattern comprises adhering the sealing pattern to the surface of the metallic core.

1 4. A method of making a head gasket assembly for an internal combustion engine substantially as herein specifically described with reference to and as shown in the accompanying drawings.