Patent GB-873619-A (GB)
Title: Improvements in pressure fluid control units
IPC: G05B19/43
Filed: 1956-10-23
Abstract: 873,619. Change-speed control. ROXBURGH, A. G. Jan. 1, 1958 [Oct. 23, 1956], No. 32201/56. Class 80 (2). [Also in Group XXIX] The selective operation of pistons A, B, C, D, R, Fig. 1, in cylinders 2 e.g. for the control of a ship's steering gear or of gears in a four-speed and reverse gear-box, is effected by shuttle valves 4A- 4R, one for each cylinder, disposed in sleeves 5 located in a bore 3 beneath the cylinders. In one form for controlling gear selection each shuttle valve incorporates a diametrical exhaust passage 6, a rightangled inlet passage 7, and a lateral peg that engages a slot in the associated sleeve 5. Each sleeve 5 is sealed from and joined to its neighbour by a disc 12 with protruding ribs whereby the correct positioning of all the sleeves relative to ports in the piston-block 1 is ensured; the sleeves each embody working ports 13, 14 registering with cylinder inlet and exhaust ports 15, 16 in the block, a pressure port 17 opening via a duct 18, Fig. 2, in the block to a feedchannel 19 parallel to bore 3 and connected to a pump, and transfer ports 20, 21 leading to a bore 23 in the block 1 which is larger than bore 3 but is parallel thereto. In bore 23 is a hollow selector valve or cylinder 26 over which a ported sleeve 27 is pressed or shrunk; at one extremity is a groove 24 to which pressure fluid is supplied whilst the interior 28 of cylinder 26. is closed at one end, the other end being connected to exhaust. The sleeve 27 consists of six rows of ports, one each for reverse and neutral position of the gears and one for each of the four forward gear positions, each row comprising as many pairs of inlet and outlet ports 29, 30 respectively, as there are pistons; the cylinder 26 has a continuous tortuous groove 31 which interconnects all the inlet ports 29 and avoids the outlet ports 30, the groove 31 registering at one end with the feed groove 24. Where the core 26 coincides with outlet ports 30 radial openings into the interior 28 of the cylinder 26 are provided. The position of the cylinder 26 is set by a handle thereon which co-operates with a fixed scale indicating the six possible positions of the cylinder so that in any position other than neutral the cylinder directs fluid from groove 24 to move the shuttle valve of the selected piston to the right, thereby admitting fluid under the latter from channel 19, the other shuttle valves being maintained in the leftward positions whereby their associated cylinders are connected to exhaust via passages 6. If overlapping of the controlled actions is to be avoided then the time of rise of a piston is made slower than its return or the initial part of the upward stroke is made idle. If overlap is required then a dash-pot is incorporated in each port 15 to restrict the rate of exhaust from the cylinder. In a modification, the gear-box has six forward and six reverse gears, the mechanism being arranged as three gear-boxes in series, one being a three-speed main-ratio box, another a two- (high and low) speed box and the third a box for reversing the direction of the output shaft; the selector cylinder is therefore required to make three simultaneous selections for any one setting which necessitates the simultaneous elevation of three pistons which is brought about by altering the pattern of the ports 29, 30 in sleeve 27 and the groove 31 in cylinder 26. The pistons may be replaced by bellows or diaphragms (not shown) (see also Group XXIX). According to the Provisional Specification the selector cylinder may be governor-operated and only one piston and cylinder need be provided.