Thermal responsive power element

Claim 1

A thermal responsive power element comprising a thermal conductive chamber, a metallic guide spool having a straight axial bore passing therethrough, said metallic guide spool being fixedly mounted in said chamber and defining an annular space therebetween, an actuating rod slidably mounted in said bore, a rubber or rubber-like sealing plug mounted in said bore with one end in contact with one end of said actuating rod, said sealing plug being convex at both its ends to form an obtuse contact angle between said sealing plug and the inner wall of the guide member, whereby the sealing plug will move smoothly in said metallic guide spool and the durability of said sealing plug will be increased and a fluid-tight seal is formed between said plug and said guide member; a second miniaturized sealing means in the opposite end of said spool, said second means having an upper and a lower annular lip, said lips projecting generally inwardly in the direction of said bore and defining an intervening annular cavity, said seal being clamped into sealing position by the outer walls of said spool being overturned inwardly thereupon; a thermally responsive expansible substance sealed within said annular space in communication with said plug whereby, upon application of heat to said thermally responsive power element, said expansible substance expands to exert a force on the lower end of said sealing plug to thus push said actuating rod from the bore in said guide means.