GB775731A - Improvements relating to control apparatus for electrically operated equipment - Google Patents

Abstract

775,731. Thermal switches; time switches. RANCO, Inc. July 26, 1955 [Aug. 6, 1954], No. 21571/55. Class 38(5) An electric switch), suitable for refrigerator defrosting control in which defrosting is initiated periodically and terminated. either in response to temperature or after a fixed time, functions similarly to that in Specification 709,771 and comprises a cam 25 rotating once per day and having two cam surfaces 26, 27; the surface 26 moving. a spring blade contact 30 to engage a sec- ond spring blade contact 31 and to move it to a position where it is engageable by a latch 54, and the surface 27 controlling the latch through a follower 55. The latch 54, follower 55 and U-shaped member 50 to form a unit pivoted at 51 and biased clockwise by a spring 57. The latch may also be realeased by the expansion of a temperature sensitive capsule 70 which tilts an arm 60 and hence the U-shaped member 50. A third contact blade 32 is provided also to co-operate with blade 31, blades 30 and 32 being connected by a link 38 to move together. Contacts 30, 31 control the refrigerator motor and contacts 31, 32 con- trol a heater. The cam surfaces are so shaped that the following sequence of events occurs. With contacts 30, 31 in engagement the latch is raised by cam rise 62, contacts are moved to the left by cam rise 45, latch is lowered into position from cam rise 62, contact 30 falls off cam step 46 weheupon contact 31 is held and the heater circuit is closed. After a predetermined time if the capsule 70 should have failed to release latch this is released by cam rise 63 and the motor circuit is again closed. The arm 55 is capable of being bent to adjust the time at which cam rise 63 operates the latch.