Abstract: A refrigeration system is disclosed having a compressor, a condenser, an evaporator, a refrigerant expansion device, a control for cycling the compressor on and off according to a sensed condition, and a refrigerant flow controlling valve. The flow controlling valve blocks the flow of refrigerant between the condenser and the evaporator when the compressor is cycled off and enables refrigerant flow between the condenser and the evaporator when the compressor is cycled on. The flow control valve includes a refrigerant pressure responsive member movable to condition the valve to block refrigerant flow in response to changes in refrigerant pressure caused by the compressor cycling off and movable to condition the valve to enable refrigerant flow in response to changes in refrigerant pressure caused by the compressor cycling on.

Abstract: A pressure responsive control device including a housing, a control switch unit and switch operating actuator, and a controller unit is disclosed for controlling operation of a refrigeration defrosting device. The actuator includes a bladder formed of thin film material which changes volume when a differential fluid pressure exists across the bladder. The bladder and switch unit are such that bladder volume changes are accompanied by minimal losses thus enabling the controller unit to be enabled in response to extremely slight differential pressures.