Abstract Apparatus is disclosed for automatically defrosting a heat exchange surface of the type that incorporates an evaporator with cooling fins, a refrigerator motor, and a fan to circulate air around the cooling surface of the evaporator to the area to be refrigerated and back again. The defrosting cycle is initiated by pneumatically sensing the air flow restriction caused by frost build up on the evaporators cooling surfaces. The defrosting cycle starts at the optimum time by means of a weight adjustment on a louver device and/or associated part. Then by a novel means, the evaporator area is automatically sealed off from the refrigerated compartment. Simultaneously, warm ambient air, or the like, outside of the refrigerated compartment is introduced into the sealed off evaporator area. This is a definitive, highly efficient circulation path, formed for rapid defrosting purposes, which utilizes the warm ambient outside air, or the like. This air passes around the frosted cooling surfaces of the sealed off evaporator, and back to the outside again. Upon completion of the defrosting cycle normal operation is restored by automatically sealing the defrosting circulation path going to the outside, while simultaneously removing the sealed path between the evaporator and refrigerated compartment. Undesired heat transfer into the refrigerated area, before, during, and after the defrosting cycle is minimal.
In a defrosting system utilizing ambient air as the defrosting medium for refrigeration system having an air cooling evaporator, blower means operating in a normal cooling cycle to take air from a cooled compartment, pass it over the evaporator and thence back to the compartment, a defrosting means which changes the air flow in the defrost made by using the blower to take ambient air from outside the compartment, direct it past the evaporator to provide the desired defrosting action and direct the air back to the ambient: the improvement in the defrosting means comprising air director which simultaneously functions as a frost build-up sensor and an arrangement for directing air in the cooling cycle mode or in the defrost mode, said air director being movably mounted in the outlet air stream from the blower means and being so arranged as to sense reduced air flow over the evaporator due to frost build-up, said air director upon sensing the need for defrost automatically moving from the cooling mode position to a defrost position thereby providing ambient air flow over the evaporator to provide defrosting and means responsive to the position of the air director to disable the evaporator during defrosting and to restore the evaporator at the termination of the defrosting.
Claim 2
Dependent Claim
211 words
In a defrosting system utilizing ambient air as the defrosting medium for refrigeration system having an air cooling evaporator, blower means operating in a normal cooling cycle to take air from a cooled compartment, pass it over the evaporator and thence back to the compartment, a defrosting means which changes the air flow in the defrost made by using the blower to take ambient air from outside the compartment, direct it past the evaporator to provide the desired defrosting action and direct the air back to the ambient: the improvement in the defrosting means comprising air director which simultaneously functions as a frost build-up sensor and an arrangement for directing air in the cooling cycle mode or in the defrost mode, said air director being movably mounted in the outlet air stream from the blower means and being so arranged as to sense reduced air flow over the evaporator due to frost build-up, said air director upon sensing the need for defrost automatically moving from the cooling mode position to a defrost position thereby providing ambient air flow over the evaporator to provide defrosting and means responsive to the position of the air director to disable the evaporator during defrosting and to restore the evaporator at the termination of the defrosting.