GB765610A - Improvements in electro-thermally actuated control devices - Google Patents

Abstract

765,610. Thermal switches. G-V. CONTROLS, Inc. Dec. 28, 1954, No. 37480/54. Class 38(5) [Also in Group XIII] A switch comprises a sealed casing containing the contacts, an elongated hollow operating member which is free from bending when heated by a heater in the operating member to cause elongation of the member, such movement causing a movable arm to operate the contacts. The operating member 20 comprises a channelsection member 22 containing metal strips 30 and an insulated heater 24, and is mounted by a spring strip 34 and a strip 32 on pins 1, 4 sealed in the base 8. The movable arm 42 is connected to the member 20 by a spring strip 50 forming a pivot point Q and to a rigid ambient-compensating member 36 by crossed springs 44, 4& forming a pivot point P. The member 36 is mounted by a spring strip 38 and a strip 40 on pins 6, 7. The arm 42 has a spring arm 52 carrying a contact 54 co-operating with a fixed contact 62 carried by a pin 5, the contacts being separated by a spring 56. A glass bead 58 carried by member 36 is held against a part of a lever 68 which sealingly passes through a flexible diaphragm 66, the lever being adjustable by a screw 70 to adjust the position of contact 54, by pivoting the member 36 and arm 42 about the lower end of member 36. Elongation of member 20 causes arm 42 to pivot about point P to close the contacts. In a modification, (Fig. 8, not shown), the bead engages the casing wall and is adjusted by deforming the casing at this point. In a further modification (Fig. 9, not shown), the contacts are normally closed and are opened by elongation of member 20.