This invention relates to a conventional radial type shaft seal with an elastomeric body which is supported by a rigid metallic case.
The metal case is a necessary part of the seal in that it stabilizes the diameter of the seal through repeated changes in operational temperature. Without the metal case, the elastomer, having a different coefficient of thermal expansion from the bore in which it fits, becomes loose and the assembly fails with repeated temperature cycling.
Heretofore the metal case has been one of the most expensive parts of a conventional shaft seal because of the large amount of waste material involved in the manufacture of this component. Present state of the art has been to form this part from a flat ring or washer which when upset by cold forming becomes generally cylindrical. Traditionally, however, the basic flat ring is cut from rectangular or strip sheet-stock so that geometrically speaking the outsides between the rings becomes scrap as well as the insides which must be removed by a piercing operation.
The present invention relates to the fabrication of the generally cylindrical metal cases from small rectangular blanks of sheet stock that in turn can be cut from large rectangular or strip stock with very little waste. The small rectangular blanks, then, are formed so that the narrow ends can be fastened together to produce the desired generally cylindrical seal cases. When this is done, the flat ring phase that produces the scrap in the present state of the art is deleted from the manufacturing process and scrap production is reduced from approximately 30% to less than 5% of the original sheet stock. Such a saving would allow four seals to be made from a piece of metal that formerly produced only three seals.