Illinois Tool Works Inc.

Dennis D Smith

Larry L Sharp

A thermal cut-off device is disclosed in which a first axial lead extends through an insulating member at one end of the device and a second axial lead contacts and extends through a conductive cylindrical housing at the other end of the device. A domed electrical contact cup is used in one embodiment to make electrical connection between the insulated lead and the outer metallic housing, and this electrical connection is maintained by a coiled helical spring. One end of the coiled spring is larger in diameter than the other end. The large diameter end is in engagement with the end of the conductive housing through which the second axial lead projects, while the smaller end of the conductive spring is in engagement with the insulated first axial lead, either directly or through the domed contact cup. The spring is held in a prestressed condition by a solid thermally fusible or meltable pellet which surrounds the spring, and which holds it in its stressed condition until the predetermined melting, or fusible, temperature of the pellet is reached at which time the stress is relieved in the spring and it contracts away from the insulated first axial lead, so as to break electrical connection between the leads of the device.

Thermal cut-off device with an activating spring that is held in a

A temperature-sensitive switching device is provided in a casing having a pair of leads that extend therefrom, by a spiral spring which forms a first electrical contact and a curved conducting member which forms a second electrical contact. The spiral spring is connected to one of the leads and is expanded and fitted over a thermally-fusible pellet which melts at a predetermined temperature. The outer diameter of the pellet is larger than the inner diameter of the spiral spring contact before it is expanded. The end of the spiral spring contact contains a curved connecting projection, which preferably forms a circular arc, that serves as a sliding contact. The other contact element is provided by a matching fixed curved conducting projection which is connected to the other lead. When the thermally-fusible pellet melts, the tension in the spring is released and it relaxes to its unexpanded size causing the conducting projection on the end of the spring to spiral either into, or out of, contact with the conducting projection on the fixed position lead thereby making, or breaking, the circuit.

Temperature-sensitive spiral spring sliding contact device

A thermal switch device is constructed with an electrical conductive spring cup contact that fits over a ceramic insulator which surrounds one lead of the device. The center of the spring cup contact has a pattern cut in it so that it is flexible, and a metallic, thin flat disc which is placed against the surface of the spring cup contact which forces the flexible portions of the spring cup contact into contact with the head of the lead that supports the ceramic insulator. A conductive cup-shaped housing that is open at one end encloses the entire structure and is in contact with the spring cup contact. The outer ends of the housing being pinched over the ceramic insulator at the open end. A second conductive lead is attached to the outer surface of the conductive housing. A pellet made of a thermally-fusible material is inserted between the housing and the metallic disc so that when it melts the disc moves away from the spring cup contact, thereby breaking the circuit between the spring cup contact and the second lead.

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Bartlett, IL, United States of America

Dennis D Smith