GB852762A - Improvements in electrical switching unit - Google Patents

Abstract

852,762. Thermal switches; snap-action switches. WILCOLATOR CO. June 5, 1958 [Aug. 19, 1957], No. 18007/58. Class 38 (5). A double-pole switch comprises two substantially similar units mounted in a common block 1 of insulating material, and having a common snap-acting actuator 13. An upper terminal member 3 has a connection screw 5 for a domed contact 9 carried on a sheet metal spring 10 so as to be adjustable by a screw 11. A lower terminal member 2 carries a connection screw 4 and a contact 8 having a flat lower surface. A bridging member 12 of silver, for example, is urged by a spring 14 against contacts 8 and 9 and has two axially aligned semi-cylindrical projections 16 pressed up to make line contact with the contact 8. When the snap-action element (not shown), for example a thermal element, causes actuator 13 to snap downwardly it engages the end of member 12 causing this member to pivot on contact 8 and break connection with contact 9. To prevent translatory movement the member 12 has two laterally extending ears which loosely engage in slots 18 in the block 1 at each side of contact 8. A stop 23 for member 12 is formed in the block 1 and a screw is provided (Figs. 1, 3 and 4, not shown) to act as an adjustable back stop for actuator 13, this being set so that about half of the travel of the actuator 13 occurs before it engages member 12, giving an impact action at the switch opening. A modification (Fig. 6, not shown) comprises a double-pole double-throw switch by providing back contacts on stops 23, provision also being made for swivelling or the like of actuator 13 to ensure proper contacting of these lower contacts.