Patent GB-418434-A (GB)
Title: Improved hydraulic control mechanism
IPC: B63H25/28
Filed: 1933-03-17
Abstract: 418,434. Hydraulic control mechanisms. CLARK, H. R., 645, Anlaby Road, Hull. March 17, 1933, Nos. 8085/33, 13229/33, and 9277 /34. [Class 114.] In hydraulic control mechanisms, such as ships' steering gears, including a continuously driven pump for actuating rams geared to the rudder head, a control reversing pump is employed for hydraulically setting the hunting valve. A rudder head 11 carries a pinion 10 geared to racks 12 upon the double set of rams 13, 14, 15, 16 arranged in opposed pairs. The control reversing pump 17 manually operated by the helm 18 is connected by conduits 19 and 20 through cocks 68, 69 to a hunting valve consisting of a displaceable sleeve valve 26 between a liner 24 and an inner cylinder 25. These parts are provided with ports which in the neutral position of the valve, Fig. 2, form a closed circuit connecting the delivery pipe 46 and return pipe 31 of the continuously running pump 32. The ram cylinders are connected by pipes 50, 51 with the cock 69 and by pipes 54, 55 with the cock 68. When the cocks are as in Fig. 3, the power pump is cut out and the circuits enable operation to be effected manually by the control pump 17. With the cocks as in Fig. 1, the circuit is set for power operation. When the control pump 17 is moved liquid is forced along one of the pipes 19 or 20, past a spring loaded valve 38 or 42 and thence to one or other end of the sleeve valve 26 to move it. Liquid displaced from the opposite end escapes through a second non- return valve back to the control pump. On displacement of the valve 26 to the right or left the power pump delivery is connected up to the rams 13, 15 or 14, 16 respectively. When set as in Fig. 1, the rams 14, 16 are given a power displacement which results in the rams 13, 15 discharging back to the pump. The hunting valve is maintained set as long as the control pump 17 is actuated but when it is stopped the returning liquid attains a pressure sufficient to open the valve controlling the passage to the other end of the sleeve valve which is thus returned to the neutral position. In a modified construction, a pair of auxiliary rams 82, 83 are connected by a bridge piece 84 directly with the rack 12 of the opposed power rams 80, 81 and are utilized to provide the follow-up motion of the valve. External to the casing of the hunting valve 89 there are provided valves 90, 91 which are displaceable from position in Fig. 4 to that in Fig. 5 by liquid from the control pump 94 through pipes 92, 93. These pipes have valves which are opened when it is desired to effect the change in position of the valves 90, 91, and are then closed. With the valves 90, 91 as in Fig. 5, a free circuit is provided for the auxiliary rams and the hand pump 94 is in direct communication with the main rams and actuates the rudder. With the valves positioned as in Fig. 4, the hand pump 94 functions only to set the hunting valve 89 and the continuously running pump 32 is used for actuating the rams. During continued operation of the helm, the auxiliary ram discharges past an end valve but on stoppage of the helm the valve closes and the delivery passes to the end of the hunting valve to bring it back to neutral. Closure of an end valve by contact of the ends 116 of the rams therewith results in the hunting valve being brought to neutral and so determines the maximum movement of the main rams. Specification 374,583 is referred to.