Abstract: An adjustable fail-safe suction stop valve is provided for providing hot gas defrost in refrigeration applications. The dual position valve (10) utilizes a single solenoid (20) and a pair of check valves (60,62) in a configuration that allows the evaporator pressure to be internally equalized through the valve to an adjustable setting over the suction pressure after a defrost cycle has occurred. The intermediate stage allows for this equalization to occur in a controlled manner without the need for an equalization valve.

Abstract: A piezo-actuated pilot valve that takes advantage of the small compact size and low power requirement of piezo technology to control the pilot flow in a pilot-operated valve. Exemplary piezo-actuated valves can be operated using a relatively low voltage power supply, such as a battery or a solar cell. This enables usage of the valve in remote locations that do not have a ready source of utility-supplied electrical power. The piezo-actuated pilot valve also can have a programmable controller and/or can have an antenna that allows the valve to be controlled wirelessly.

Abstract: A pilot valve includes a first port in selective fluid communication with a second port by a passageway through the valve; a valve seat; a movable piston selectively engagable with the valve seat to close the valve when the valve member engages the valve seat and to open the valve when the valve member is spaced from the valve seat; a pilot passageway providing a pathway to a portion of the piston opposite the side that engages the valve seat, the pathway being opened and closed by a pilot plug; and a piezo unit operable to control movement of the pilot plug to control whether the pathway is opened or closed.

Abstract: An adjustable fail-safe suction stop valve is provided for provding hot gas defrost in refrigeration applications. The dual position valve (10) utilizes a single solenoid (20) and a pair of check valves (60,62) in a configuration that allows the evaporator pressure to be internally equalized through the valve to an adjustable setting over the suction pressure after a defrost cycle has occurred. The intermediate stage allows for this equalization to occur in a controlled manner without the need for an equalization valve.