Abstract: A safety valve for use in a compressed air line having a supply valve and a control valve, to prevent inadvertent sudden shifting of the controlled part when the line is exhausted and later repressurized. The safety valve comprises a normally closed piston-operated poppet valve, the piston chamber and outlet port being connected to the supply port through a bypass with an adjustable restriction upstream of the valve member. In one embodiment, the adjustable restriction comprises a replaceable plug threaded in the valve body. In a second version, the adjustable restriction comprises a needle valve mounted in a housing cover.

Abstract: A four-way spool valve controls a double acting fluid motor for locking or unlocking a part such as a tailgate. The valve is spring-urged to a locking position and hand-operable to its unlocking position. A position at the end of the valve is pressurized when in the unlocking position to counteract the spring. This piston monitors supply pressure so that the valve will be automatically shifted to its locking position when pressure drops. This will insure a locked position of the part when pressure is reapplied.

Abstract: A system for disconnecting a compressed air control system from a main supply line if the system is not used with a predetermined frequency. A normally closed solenoid-operated three-way reset valve is controlled by a normally open hand-operated switch which simultaneously operates a control valve in the system for a working cylinder. When the working cylinder valve is actuated, the three-way valve charges the operating chamber of a normally closed three-way air saver valve in series with the main line, thus opening the air saver valve. The operating chamber of the air saver valve discharges at a controlled rate through the reset valve when the latter returns to its closed position by opening the switch. If the operator closes the switch again before the pressure in the operating chamber is depleted, the air-saver valve is held open.

Abstract: A safety valve for use in a compressed air line having a supply valve and a control valve, to prevent inadvertent sudden shifting of the controlled part when the line is exhausted and later repressurized. The safety valve comprises a normally closed piston-operated poppet valve, the piston chamber and outlet port being connected to the supply port through a bypass with an adjustable restriction upstream of the valve member. In one embodiment, the adjustable restriction comprises a replaceable plug threaded in the valve body. In a second version, the adjustable restriction comprises a needle valve mounted in a housing cover.