Metal working – Method of mechanical manufacture – Combined manufacture including applying or shaping of fluent...
Patent
1994-12-07
1996-11-05
Ball, Michael W.
Metal working
Method of mechanical manufacture
Combined manufacture including applying or shaping of fluent...
156219, 156279, 264112, 264113, F16J 1512
Patent
active
055705014
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention is concerned with a method of manufacturing an embossed metallic sheet coated at least partially with expanded graphite and suitable for use as a gasket or as a component layer of a gasket.
DESCRIPTION OF THE PRIOR ART
Many gaskets for use in industrial and automotive applications comprise a metallic sheet, often of steel, coated on one or more surfaces with a sealing material. The sealing material is, in some cases, expanded graphite which has been compacted. Expanded graphite is also called "exfoliated graphite".
The normal method of coating such a metallic sheet is to make a thin (0.2 to 1.5 mm thick) self-supporting foil of the expanded graphite and to attach the foil to a surface of the reinforcing sheet. This method, however, involves making and handling the thin foil which is easily damaged and so requires extreme care.
Instead of applying an already made foil to the reinforcing sheet, it is known to position a layer of particles of expanded graphite on a surface of the sheet which has been treated with a layer of adhesive, and to press the particles so that the coalesce and form a coating in situ on the reinforcing sheet.
It is known to provide rubber coated gaskets with embossed ridges, e.g. a generally semi-circular (in cross-section) ridge, around the hole in the gasket. These ridges are resilient and cause controlled stress concentrations during use of the gasket.
SUMMARY AND OBJECTS OF THE INVENTION
It is an object of the present invention to provide an efficient method of manufacturing an embossed metallic sheet coated at least partially with expanded graphite and suitable for use as a gasket or as a component layer of a gasket.
The invention provides a method of manufacturing an embossed metallic sheet coated at least partially with expanded graphite and suitable for use as a gasket or as a component layer of a gasket, characterised in that the method comprises positioning a substantially planar metallic sheet between an upper embossing die and a lower embossing die with a layer of particles of expanded graphite between one of said dies and a surface of the sheet, one of said dies having at least one protuberance arranged to emboss a ridge into the sheet, the method also comprising pressing said dies together thereby compressing the particles of expanded graphite, so that they coalesce and form a coating attached to said sheet, and simultaneously embossing the ridge into the sheet and the coating.
In a method in accordance with the invention, the expanded graphite is applied to the planar sheet and the ridge is embossed into the sheet in one operation so that an efficient method of manufacture is provided.
The other of said dies may have a complementary shape to the die which has the protuberance, e.g. it may have a recess to receive the ridge. In some sheets, a portion of the embossed sheet may be planar and parallel to other portions of the sheet and the ridge may connect said portions.
Preferably, said layer of particles is positioned by providing a particle retaining wall surrounding the lower embossing die and projecting upwardly therefrom to a substantially equal extent around the periphery of the wall, filling the space defined by the wall above the lower die with particles of expanded graphite, and skimming the particle layer level with the top of said wall, the planar sheet being positioned on top of the layer of particles. This method provides a convenient way in which the edges of the layer of particles can be confined and a substantially level layer can be formed across the sheet. The presence of the wall also assists in locating the sheet relative to the dies.
Where the sheet is to have expanded graphite coatings on both of the surfaces thereof, a further layer of particles may be positioned between said sheet and the other of said dies, and two layers are pressed into coatings simultaneously. Alternatively, however, the two coatings may be applied sequentially with the embossing taking place simultaneously with the formation of eithe
REFERENCES:
patent: 2444394 (1943-03-01), Arnold
patent: 3028667 (1958-04-01), Wintermute et al.
patent: 4876876 (1989-10-01), Ishida et al.
patent: 5226662 (1993-07-01), Justus
Atkinson Alan W.
Walsh Melanie J.
Ball Michael W.
T&N Technology Limited
Yao Sam Chuan
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