GB535424A - Improvements relating to pneumatic control mechanisms - Google Patents

Abstract

535,424. Valves. PRATT, J. H., MANLEY, G. E., and GIRLING, A. H. G. Oct. 6, 1939, No. 27318. [Class 135] A rotary valve device particularly adapted for use as a steering control unit for use in conjunction with a vehicle employing endless tracks and utilizing a combination of selfchanging gear boxes and brakes for performing the several steering operations has means secured to and turning with the actuating spindle or spindles for relieving the valve or valves of part of the fluid pressure tending to press the valve member against its seat. As shown in the Figs., two coaxial and separately actuated valves are employed interlocked by a pair of slidable rods 27, 28 having conical heads, 27a, 28a co-operating with mating recesses 24a, 25a in the two operating handles 24, 25. The valve discs 16, of synthetic resin have exhaust passages 16a connecting ports on the face of the disc with a central exhaust passage 13b in the valve spindle and with pressure inlet passages connecting ports in the face of the disc with through ports in its outer periphery with the chamber 10 supplied with pressure through a connection 26. The valve seat member 18 of gun-metal or bronze is clamped to an aluminium casing 10 by a cap 10a and has passages 18 leading to the power devices. A spring-pressed ball catch 14 cooperates with hemi-spherical recesses in the actuating spindle 13 to hold the valve in its adjusted position. The pressure in the valve member is relieved by a cup-leather 19 clamped between washers 20a, 20b to the end of the actuating spindle 13 'by a screwed plug 21 and slidably engaging an annular wall on the back of the valve member. Springs 22 housed in pockets in the valve member bear on the washer 20b to hold the valve member in engagement with its seat. The cap houses a ball bearing 23 for the spindle and is provided with a lubricating nipple 27. In a modification in which a single valve replaces the two valves the cup leather is secured to a flange on the inner end of the spindle by a series of bolts, some of which have extensions to locate the springs 22 while others have ball-ends engaging operating sockets in the valve member. In this form two ball catches co-operate with two series of recesses in one of the cup-leather clamping plates. According to the Provisional Specification the valve member may be of conical shape and locking means of the plunger and tooth type employed.