GB1420337A - Defrosting control devices - Google Patents

Abstract

1420337 Defrosting AMF Inc 18 Oct 1973 [15 Dec 1972] 58141/72 Heading F4H A defrosting control device comprises an ice sensing device including a series of elements on which frost is to accumulate and which are moved towards each other periodically. When a predetermined amount of ice has formed on the elements, this movement is restricted and causes actuation of a defrost control switch. As shown, a switch-actuating lever 16 is supported on rods 11, 20 and is engaged by a spring 22, a weak, frost-collecting spring 18 and a cam 24 driven by a motor 25. If no defrosting is necessary, on rotation of the cam, the spring 18 collapses and the lever 16 pivots, using the spring 22 as a fulcrum. If frost builds up on the spring 18 to a predetermined thickness, the spring compresses the frost into solid ice and will not collapse, whereupon the cam 24 causes the lever to compress the spring 22 and the lower end of the lever moves a pivoted' arm 26 to actuate a switch 36 controlling the compressor, fan and heater of a refrigerating chamber. The arm 26 is locked in the switch actuating position by a pivoted lever 27 connected to the arm 26 by a spring 32. The lever 27 is released from its locking position by movement of the lever 16 when the frost is removed from the spring 18. In a second embodiment, Fig. 2 (not shown), two members are mounted for linear axial movement on a rod and have interengaging cam faces. The members are urged towards each other by a strong spring and a weak, frostcollecting, spring. One of the members is rotated and, when the frost-collecting spring is coated with ice, is moved axially against the action of the strong spring by relative rotation of the cam faces to actuate the defrost switch. A time-delay may be incorporated to delay switching-on of the fan for a period after the compressor is re-started. The coil spring for frost-collecting may be replaced by discs separated by resilient pads.