US 7,454,918 B2
Refrigeration and defrost control system
Thomas J. Davern, St. Charles, Ill. (US); Jack Devine, Carol Stream, Ill. (US); and William B. Bennett, Allegan, Mich. (US)
Assigned to Robertshaw Controls Company, Richmond, Va. (US)
Filed on Mar. 30, 2005, as Appl. No. 11/93,912.
Prior Publication US 2006/0218946 A1, Oct. 05, 2006
Int. Cl. F25D 21/06 (2006.01)
U.S. Cl. 62—155  [62/150; 62/151; 62/153; 62/154; 62/80; 62/275; 62/234] 14 Claims
OG exemplary drawing
 
1. In a freezer having a refrigeration system including a compressor, an evaporator coil, an evaporator fan to circulate air over the evaporator coil and into a compartment of the freezer, a defrost heater for periodically removing frost build-up from the evaporator coil, and a timer control system controlling the operation of the compressor, evaporator fan, and defrost heater, the timer control system comprising:
a switch arrangement including a compressor control blade, an evaporator fan control blade, a defrost heater control blade, and a common blade;
a rotatable cam having a profiled surface in operable communication with the switch arrangement controlling a relative positioning of the blades of the switch arrangement such that the compressor control blade and evaporator fan control blade contact the common blade in a first cycle, the defrost heater control blade connects with the common blade in a second cycle, and wherein the cam provides a third cycle between the first cycle and the second cycle delaying the defrost heater control blade from contacting the common blade for a period of time after the first cycle.