Gasket

Abstract: The gasket comprises a peripheral loop of sheet metal encased in an elastomeric material, the core being locally thickened, preferably in the vicinity of fixing screws by lateral projections(14) from the stamping which are folded over to double the thickness, and the double thickness is then joggled to distribute the thicker portions (10) symmetrically of the single sheet portion (12), the thickened portion (10) then being coined to control the dimensions more accurately and tend to lock the edges together.

Description: This invention relates to gaskets for use in making fluid tight seals between two components. The gasket material is selected for its suitability in view of the location. For example, a gasket for an I.C. engine will at different locations be exposed to coolant fluid which may be a water/anti-freeze/anti-oxidant mixture, lubricating oil, fuel/air mixtures, and/or products of combustion, and in any of these instances at high or low temperatures. The gasketted joint is often required to be clamped tight under specific designed loading. This clamping pressure is applied at (often) a number of specific points. For example a crank case may be bolted to the cylinder block at perhaps 10 or 20 points, being held by screws passing through apertures in the gasket. Certain elastomers are found to be very suitable for gasket use in terms of being unaffected by the ambient conditions, but are overly ductile, and liable to be extruded out of the joint if the same is over tightened. The available tolerance may not be sufficient for practical purposes, in view of the required clamping pressures for other reasons. This is true of certain silicon rubbers for example. Known solutions to this problem have involved making a series of inserts which are turned parts or sintered powder metal compacts of precise dimensions, which are then attached to for example a sheet metal pressing which forms a reinforcing core extending around the periphery of the gasket, and this core is encased with the elastomer. When clamped tight, the elastomer is compressed sufficiently to form a fluid-tight seal between the two clamped parts. The inserts act as spacers between the clamped parts and maintain the integrity of the elastomer between the spacers. But this is an expensive solution. Another known solution is disclosed in DE-A-38 31 414, on which the two-part form of independent claim 1 is based. Clamping pressure limiters consisting of sleeve-shaped spacers extending normal to the plane of the sheet metal core and having a length greater than the core thickness are formed around screw receiving apertures by cold flow working of the core. In accordance with the invention there is provided a gasket comprising a reinforcing core which is encased over a substantial portion of the peripheral length of the gasket by an elastomeric material and said core having locally thickened portions at a plurality of points along said length by portions made integrally and unitarily from the reinforcing material, the locally thickened portions having apertures for receiving clamping screws, the core made of a sheet metal stamping of uniform thickness, characterized by the locally thickened portions having a double or treble thickness with respect to the uniform thickness of the core, said double or treble thickness being obtained by the folding onto said core of lugs made integral with the core and projecting laterally thereof before the folding operation. In the case of double thickness it is preferred to joggle the doubled thickness so as to distribute the material symmetrically about a plane containing the periphery of the gasket. With a treble thickness, the folded lugs may lie on opposite faces of the original material and hence be symmetrically distributed without requiring joggling. Preferably also the thicker part is coined so as to have the effect of closely controlling the dimensions and this will also, so it is believed, tend to lock the edges of the laminae together and unify them. The double portions may correspond with the locations of clamping screws. Precise gasket location with respect to all of the screws may be afforded by making recesses or open ended slots in the doubled portions, with the recess or slot edge coined to precise dimensional tolerances with respect to the complete gasket. The holes may be pierced after the folding. A further contribution towards precision and accuracy is provided, according to an advantageous feature of the invention, by punching generally circular holes in the original sheet material from which the reinforcing core is made, at positions corresponding to the end of each line where a fold is required. Gaskets are of this kind are most usually made as a continuous peripheral loop formation. According to a further aspect of the invention, the reinforcement is made in two parts meeting end to end. Thus the two parts may be L shaped or U shaped for example. The free ends of the two components which are to be subsequently joined together are made of a reduced thickness and width, and then welded together, and the weld is subsequently flattened so as to maintain the overall dimensions of the welds joint within the dimensions of the pressing at other locations. One embodiment of the invention is now more particularly described with reference to the accompanying drawings wherein:- Figure 1 is a fragmentary end view of a reinforcement for a gasket; Figure 2 is an even more fragmentary view of the same at an earlier stage of manufacture; and Figures 3 end 4 are sections on the line 3.3 and 4.4 but through the complete gasket on an enlarged scale. Turning now to the drawings, the gasket comprises a (usually) loop-like member having a reinforcing core encased in elastomer. In order to minimise wastage of sheet material in forming the core, it is made of two or more parts joined together. Each of the parts is generally strip like. The strip is of uniform width and in this example is locally thickened at the position of fixing screws. In Figure 1 the local thickened areas 10 comprise two thicknesses of the sheet material and hence these areas are twice the thickness of the intervening strip portions 12 which extend between the locally thickened zones. The thickened portions are joggled so as to be symmetrically distributed about the plane P, Figures 3 and 4. Figure 2 shows the metal gasket reinforcement at an earlier stage of manufacture when lugs 14 extend laterally of the portions 12, before they are folded over to form the thickened portions. The lugs may extend inwardly or outwardly of the loop. A substantially circular hole 16 is punched at a position which will lie at each end of each fold line 18 to facilitate the folding operation and provide a more accurate location for the fold. The arcuate recesses 20, Figure 1, which are to locate on the fixing screws, may be punched at the Figure 2 stage, or at the Figure 1 stage after folding, or a combination of the two meaning that one of the recesses eg 24 Figure 2 may be pierced at the Figure 2 stage and the other of the recesses 26 may be pierced at the Figure 1 stage and possibly to closer dimensions so that the recess 24 has a greater clearance about the screw and the recess 26 locates with greater precision on the screw. In any event the thickened portion is preferably coined as a final operation to control the dimensions and location more precisely. The coining may have the effect of merging the edges of the recesses which may prevent any possible separation of the part 14 in the event of inaccurate location for example by a mechanic in subsequent maintenance of an engine fitted with such a gasket. The joint between a pair of the reinforcing components is provided by the weld 30 provided on butt ends 32, 34 which, as shown, are narrower than the portions 12 and may also be of reduced thickness. The weld may be subject to a press blow or even a coining operation to ensure that the area of the weld lies within the dimensions of the strip portions 12. Holes 36 are provided to jig the component for the welding operation. Further holes 38 are provided so that the encasing elastomer 40 extends through the strip for additional security. The ends to be welded together are reduced in width as at 32,34, and possibly also in thickness, so as to accommodate weld flash within the dimensions of the strip 12. The casing elastomer is of a total thickness 42 greater than the thickened portions 10 in order to create a good gasketting seal over the whole periphery of the gasket, with controlled claming between arrows A to the thickness of the portion 10.

Claims: Gasket comprising a reinforcing core (12) which is encased over a substantial portion of the peripheral length of the gasket by an elastomeric material (40) and said core having locally thickened portions (10) at a plurality of points along said length by portions made integrally and unitarily from the reinforcing material, the locally thickened portions (10) having apertures (20) for receiving clamping screws, the core (12) being made of a sheet metal stamping of uniform thickness, characterized by the locally thickened portions (10) having a double or treble thickness with respect to the uniform thickness of the core (12), said double or treble thickness being obtained by the folding onto said core of lugs (14) made integral with the core (12) and projecting laterally thereof before the folding operation. Gasket according to claim 1, characterized in that the doubled thickness of the thickened portions (10) of the core (12) is joggled to distribute the material symmetrically about a plane containing the periphery of the gasket. Gasket according to claim 2, characterized in that the trebled thickness of the core (12) includes folded lugs (14) lying on opposite faces of the material lying between said folded lugs. Gasket according to any one of claims 1 to 3, characterized in that the thicker part (10) is coined at least to control the dimensions. Gasket according to claim 1, characterized in that the apertures are open-ended slots (20) in the thickened portions (10) with the slot edges coined. Gasket according to any one of claims 1 to 5, characterized in that a sheet material from which the reinforcing core (12) is to be made by stamping has generally circular holes (16) punched in it at positions corresponding to the end of each line (18) where a fold is required to provide the local thickening (10). Gasket according to any preceding claim, characterized in that the reinforcing core (12) is a loop-like member consisting of two or more parts joined together end-to-end.

Inventors: ARBUTHNOT RICHARD E, BONELL GERARD, ARBUTHNOT, RICHARD E., BONELL, GERARD
Applicants: JAMAK FABRICATION EUROP LTD, METALRAX GROUP PLC, JAMAK FABRICATION EUROPE, LTD., METALRAX GROUP PLC.
Application year: 1991
Main classification: F16J15
IPC codes: F16J15