Patent GB-721431-A (GB)
Title: Improvements in hydraulic control systems
IPC: F15B11/08
Filed: 1948-01-21
Abstract: 721,431. Fluid-pressure servomotor control systems. OLAER MARINE. Jan. 21, 1948. Jan. 22, 1947], No. 1884/48. Class 135. A hydraulic servomotor control system for training and elevating heavy guns comprises an auxiliary system operable in response to positional and speed disagreement between the control and controlled members to increase the flow rate through a control device supplying the servomotor with pressure liquid so that on continuous movement of the control member, the speed of the controlled member is adjusted and maintained to correspond to that of the control member. As shown in Fig. 4, a rotatable control member 1 mounted on a shaft 1ahaving a worm 2 engageable with a toothed wheel 3 secured to the controlled member constituted by the rotor of a hydraulic servomotor M actuates a member 4 controlling a valve 10 supplying pressure liquid to a force multiplying piston 8. The piston-rod is connected at its end 7 to a lever 6 operating through a rod 5, the control device constituted by a main distributer D and to links 21, 22 operating through a rod 20, the auxiliary system constituted by a pilot distributer d and a jack V. The jack is connected by its rod 24 to the upper end of the lever 6. The left-hand side of the jack is constantly open to pressure liquid from a source P through a pipe 25 having a throttle 28, whilst its right-hand side may be connected either to the source P or exhaust E by the distributer d. The valve 10 and distributers D, d are of similar construction each comprising a spring-loaded valve head and stem having an axial hole therethrough and a cap member engageable with an enlarged portion of the stem. The enlarged stem portion slides in the casing and the cap members of the distributers D, d are formed integral with the rods 5, 20 respectively whilst that of the distributer 10 abuts the member 4. The left-hand side of the motor M is constantly connected to a pressure source P/2 supplying liquid at half the pressure of that from the source P, whilst its right-hand side may be connected to the source P through a pressure regulator R and the distributer D or to exhaust E through the distributer D and a pressure regulator R1. With the motor M initially at rest rotation of the member 1 will cause axial movement of the worm 2 and member 4 to operate the valve 10. If, eg., the valve 10 moves leftwards its cap 10a will be unseated by liquid pressure and pressure liquid to the left of the piston 8 will be exhausted through passages 54, 55 and the cap 10a. The piston 8 then moves to the left to rotate the lever 6 clockwise about its initially fixed end 15 to unseat the head 11 of the distributer D and so supply pressure liquid to the motor M which rotates clockwise and in so doing returns the worm 2 and member 4 towards their original positions and so tend to seat the head 11 and stop the motor M. At the same time the head 29 of the distributer d is unseated by the links 21, 22 to slowly supply the right-hand side of the jack V with pressure liquid to move it to the left to rotate the lever 6 anticlockwise about its now fixed end 7 and with some delay open the head 11 of the distributer D beyond its original opening so that on the return of the worm 2 and the member 4 to their original positions with the head 29 of the distributer dl seated, the head 11 of the distributer D remains unseated sufficiently so that when the member 1 is continuously rotated at constant speed the motor M will continuously rotate at the same speed. The purpose of the regulators R, R1 is to eliminate hunting and allow the distributer D to settle down quickly. Should, e.g., the flow rate through the distributer D increase due to decreased load on the motor M, the pressure on the downstream side of the distributer will decrease resulting in the raising of the regulator piston 36 and a reduction in the flow therethrough to correspond to the new motor load to restore the speed of the motor to its constant value. Similarly, the regulator R1 controls the flow rate between the motor M and the outlet E to operate the regulator piston 42. As shown in Fig. 5, the control member is constituted by a rod 62, the servomotor by a jack VI, the controlled member by the piston and rod of the jack VI, the control device by a main distributer D1 and the auxiliary system by a pilot distributer dl, auxiliary jack v1 and springs 81, 82. The main distributer D1 comprises valve members 60, 61, operable through plungers 98, 97 by a lever 74 fixedly pivoted at 95 and connected to the rod 72 of a piston 73 of the jack v1. The piston 73 is formed with an oil-filled chamber 75 slidably mounting a smaller piston 76 whose rod 70 is secured to an arm 80 interposed between the springs 81, 82 and connected to a floating lever 69. The lever 69 is connected at one end to a plunger 83 operating the valve of the pilot distributer d1 and at its other end to a link 67 which through a lever 63 is connected to the control rod 62. In operation, upward movement of the rod 62 causes rotation of the lever 63 about its initially fixed fulcrum 64 to unseat the valve head 86 of the distributer d, to supply the underside of the piston 73 with pressure liquid from a source P which also constantly supplies the smaller upper surface thereof. The piston 73 rises to unseat the head 96 and cap 99 of the valves 61, 60 respectively to admit pressure liquid to the underside of the piston of the jack V1 and exhaust it from its upper side which then lifts and rotates the lever 63 clockwise about its now fixed fulcrum 105 tending to return the distributer d1 to its closed position. The piston 76 is also raised to compress the spring 81 which after a time slowly resets the piston 76 to increase the opening of the head 86 of the distributer d1 and thence the head 96 and cap 99 of the distributer D1, so that the piston of the jack V1 continues to move upwards at the same speed as that of the control rod 62. As shown in Fig. 6, the control member, the controlled member, and the servomotor are the same as in Fig. 4, the control device being the main distributer D2 and the auxiliary system the pilot distributer d2, piston and cylinder 136, 134 and springs 139. On rotation of the control member 1, e.g., to displace an operating member 110 upwards, a lever 114 rotates anticlockwise about its fixed fulcrum O and moves the body 111 of the distributer d2 downwards to permit pressure liquid from a source P to act on the left-hand face of a piston assembly 119 subjected on its smaller right-hand face to the same pressure through a pipe 120 and passages 121, 122. The piston is then moved to the right to uncover a passage 124 to pass pressure liquid to act on the left face of the piston 127 of a piston assembly 127, 128, 129, which is thereby moved to the left against its spring 130 to uncover a line 133 leading to the outlet E. The result of these movements is to supply pressure liquid to the lower side of the motor M and connect its upper side to the outlet E and so rotate the motor M to move the member 110 back towards its initial position. At the same time the cylinder 134 which is filled with oil and connected to the piston assembly 119 moves together with its piston 136 to the right to compress the right-hand spring 139 and through a rod 135 give a supplemental opening to the pilot valve d1. After some delay through the dashpot action of a passage 140 in the cylinder, the spring adjusts the piston 136 to rotate a rod 135 about the fixed fulcrum O to move the oparating member 110 back to its starting position, and thence on continuous rotation of the control member 1 at constant speed, the motor M continuously rotates at the same speed. The diameters of the pistons 127, 129 and the rate of the spring 130 are so calculated that the piston assembly 127, 128, 129 which is connected to source P, outlet E and both sides of the motor M takes the place of the pressure regulators R, R 1, Fig. 4. As shown in Fig. 7, an operating rod 230 assumed connected to a control member and a controlled member acts simultaneously on a main distributer D5, a first pilot distributer d5 and a second pilot distributer d6 to unseat their respective valve members. The distributer D5 supplies pressure liquid to the servomotor which moves to operate the controlled member and move the rod 230 towards its initial position. The distributer d5 supplies a jack 235 with pressure liquid which with some delay acts on the valve member of the D5 distributor to increase its opening to speed up the controlled member. The distributer d6 supplies a jack 240 which increases the opening of the d5 distributer and in turn with still further delay the opening of the D5 distributer to suppress the dephasing between the control and controlled member not only for any given constant speed but also for any given constant acceleration. As shown in Fig. 8, the device controlling the supply of pressure liquid to a hydraulic motor M is constituted by a variable delivery pump 275 having a spring-loaded piston 276 subjected to the pressure of liquid controlled by a pilot distributer 282 which also acts on the piston 280 of a jack 281. The piston 280 is connected to an operating lever 278 fulcrumed at its upper end to a fixed point 279 and connected at its lower end to the rotor of an electrical differential 272 in circuit with a Selsyn transmitter 271 and a Selsyn receiver 273, the transmitter 271 being connected by worm gearing 274 to the rotor of the motor M. Any difference between the impulses generated by the Selsyns is transmitted to the differential 272 to rotate the lever 278. On, e.g., the lever 278 rotating clockwise the piston 280 is moved to the left and the displaced pressure liquid moves the piston 276 to the left to determine the flow rate of the pump 275 supplying the motor M which is rotated in a direction tending to restore the differential towards its zero position. The lever 278 at the same t