GB570202A - Improvements in hydraulic control mechanism - Google Patents

Abstract

570,202. Hydraulic control mechanism. PRATT, J. H., and GIRLING, A. H. G. Jan. 20, 1942, No. 799. [Class 69 (ii)] [Also in Group XXXI] A hydraulic control mechanism which is especially applicable for the steering of track-laying vehicles is constructed with a number of hydraulic actuating mechanisms 10, 11, 12 controlled by a common distributing device A which can be set so that either of the mechanisms 10, 11, 12 are in operation, and the control of one of the mechanisms is effected in such a manner that there is a sense of " feel " on the control means which is proportionate to the extent of the operation performed. As shown the device A comprises a piston valve 26 moving in a casing connected by a pipe 20b to a pressure reservoir 21 supplied by a plunp 23 from a reservoir 22 under control of a byepass valve 24. A pipe 25 returns the liquid to exhaust. Each track is similarly controlled and with each control lever 16 in the position shown in Fig. 1 engaging a stop 16b the vehicle moves straight ahead. In this position, the mechanisms 10, 11, 12 are all connected to exhaust and a band brake 13 is moved by a control spring 17 to control an epicyclic changespeed gear-box so that each track moves forward and at the same speed. To enable the vehicle to move in a curve of controlled radius, one of the levers 16 is moved counter-clockwise to the position shown in Fig. 2, which moves the valve 26 to the position shown-in which the mechanism 10 is connected to the pressure pipe 20b so that the band 13 is relaxed and the pressure is connected to mechanism 11 which controls a band 14 so as to operate the track at a'speed dependent upon the pressure applied to the mechanism 11 and this is. dependent upon the position of lever 16. The operator thus has a sense of feel related to the extent of turn of the vehicle. The movement of the lever 16 to the left is opposed by a spring plunger 29, and by pressure upon the valve due to admission of fluid to a balance chamber 19a between the end of the valve and the end of the valve casing. A plug 27 controls the motion of the tubular end 26d of the valve. This tubular end 26d serves to produce a constant pressure on the valve owing to its connection with a pressure pipe 20a offset from the pipe 20b. On further movement of the lever 16 to the left, pressure is connected to mechanism 12 and a brake 15 is applied to stop the movement of the track, so that the vehicle advances with a skidding motion.