Abstract: A safety valve designed for relieving pressure in a mine support jack. A washer and check valve are positioned in a counterbore located on the front surface of a resilient gasket member. A leg extends from the rear surface of the resilient gasket and extends through a rear chamber to support the check valve in a position sealing the outlet port. The rear chamber is filled with pressurized gas to form a gas cushion. The end of the leg is positioned to seal an inflation orifice.

Abstract: A slide valve especially designed for mining prop cylinders. The slide valve is durable and can be easily checked and adjusted. An inlet pressure line is separated from an outlet line by a diaphragm pressed against its seat by a spring. A thrust washer allows the diaphragm to remain flat, even when it is subjected to the pressure of the spring.

Abstract: A return device for a hydraulic steering mechanism of a vehicle includes an pparatus for automatically returning the wheels of the vehicle to a straight-ahead position after they are laterally pivoted by a steering wheel acting through a line of shafts. A hairpin spring is stressed by the rotation of a drum mounted on one of the shafts to create a resistance to further lateral pivoting of the vehicle wheels away from a straight-ahead position and a return force to return the vehicle wheels to a straight-ahead position. After the hairpin spring is stressed, a coil spring is tensioned by the rotation of the drum to create an additional resistance to further lateral pivoting of the vehicle wheels away from a straight-ahead position and an additional return force to return the vehicle wheels to a straight-ahead position.

Abstract: A control device for a steering mechanism of a vehicle includes hydraulic means for laterally pivoting a pair of independently suspended guide wheels in response to rotation of a steering wheel of the vehicle. The hydraulic means includes a pair of double-acting jacks attached to respective guide wheels in such a manner that the extension of each jack pivots a corresponding guide wheel, and a pair of valves mounted on respective jacks for controlling the extension thereof. The valves are controlled by a pair of linkages which are connected to the steering wheel by a coupling mechanism in such a manner that the valves are simultaneously controlled in response to rotation of the steering wheel so that both guide wheels are laterally pivoted in the same angular direction.