Metal working – Method of mechanical manufacture – With testing or indicating
Patent
1994-01-21
1996-01-23
Rosenbaum, Mark
Metal working
Method of mechanical manufacture
With testing or indicating
72146, 2424131, 2424132, F16J 1512, B21C 4706
Patent
active
054856655
DESCRIPTION:
BRIEF SUMMARY
This invention is concerned with gasket size control for spiral wound gaskets.
Spiral wound gaskets are well known and are formed by winding a sealing strip, usually of steel, and a compressible filler strip around a mandrel so that the filler strip is interposed between turns of the sealing strip. In the process of forming such a gasket, the sealing strip is passed between embossing rollers to give it a V-shaped cross-section and an end of the sealing strip is connected to the mandrel. The end of the sealing strip is usually manually fed into a radial slot formed in the mandrel, the cross-sectional shape of the slot may match that of the strip. The mandrel is then rotated through more than one turn drawing strip on to the periphery of the mandrel. Next, a closed loop of the sealing strip is formed around the mandrel by welding overlying parts of the sealing strip on the mandrel together. Next, an end of the filler strip is manually-fed into the nip between the sealing strip already on the mandrel and the sealing strip waiting to be wound onto the mandrel. The mandrel is then rotated so that both the filler strip and the sealing strip are drawn onto the mandrel and a spiral gasket is formed with the compressible filler strip interposed between turns of the sealing strip. To terminate the gasket, the supply of filler strip to the mandrel is terminated and at least one further turn of the sealing strip is applied to the mandrel by rotation thereof and overlying turns of the sealing strip are again welded together to form a complete loop of the sealing strip around the outside of the gasket. During the formation of a gasket a compression roller runs on the edge of the gasket and controls the degree of compression which the filler strip experiences. The compression roller is withdrawn from the mandrel at a predetermined rate so that the filler is compressed by an amount which is dependent upon the rate at which the compression roller is moved in relation to the turning of the mandrel. Alternatively, the compression roller may be subjected to a constant pressure throughout winding of the gasket.
To control the size of such spiral wound gaskets, i.e., the length of the outer diameter thereof, the number of turns of the mandrel is controlled. In such a process, the mandrel is rotated for a pre-determined number of turns with both filler and sealing strips being supplied to the mandrel. However, this process results in a considerable variation in the diameters of the gaskets formed. These variations are caused by variations in the thickness and in the compressibility of the compressible filler strip and by variations in the pick-up point of the filler strip. It is, therefore, common practice to provide one or more extra turns of the sealing strip which can be broken off to different lengths to adjust the diameter of the gasket. However, the provision of such extra turns is wasteful in material, requires a skilled sizing operation and requires an extra welding operation to secure the final end of the sealing strip.
It has been proposed that the size of a spiral gasket should be controlled by measuring its radius continuously as it is formed by running a pointer on the periphery of the gasket and detecting the radius from the movement of the pointer. However, it is found that the radius at a given point is not a good measure of the overall size of the gasket because during its formation the gasket is subject to distortion caused by the pressure applied thereto by a pressure roller which presses the sealing strip against the compressible filler. The pressure roller also guides the sealing and filler strips onto the periphery of the mandrel and ensures that the successive turns lie on top of one another.
It is an object of the present invention to provide an improved method for controlling the size of spiral gaskets.
The invention provides a method of controlling the size of spiral gaskets which are formed by winding a sealing strip and a compressible filler strip around a mandrel so that the filler strip is interpose
REFERENCES:
patent: 3898436 (1975-08-01), Pottebaum et al.
patent: 3905090 (1975-09-01), Painter
patent: 3926445 (1975-12-01), Farnam
patent: 4048829 (1977-09-01), Thomas
patent: 4781048 (1988-11-01), Richardson
Marks Kevin T.
Remedios Rosario
Salter Nigel D.
Waddington Peter
Hansen Kenneth J.
Rosenbaum Mark
T&N Technology Limited
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