Patent GB-682923-A (GB)
Title: Improvements in or relating to hydraulic apparatus for preventing checking or controlling relative movement between associated bodies
Inventor: LOVE JOHN
IPC: F16H35/14
Filed: 1951-04-24
Abstract: 682,923. Dashpots. K.A.C., Ltd. Oct. 22, 1951 [April 24, 1951; Sept. 7, 1951], Nos. 9522/51 and 21165/51. Addition to 667,769. Class 108 (iii). [Also in Group XXXIII] The invention relates to an improvement in the means for automatically restricting the liquid flow in the hydraulic apparatus forming the subject of the parent Specification. According to the invention, a control unit for the apparatus comprises a push-rod 9 (Fig. 1) which co-operates with a check-valve 8, loading means 26 adapted to urge the push-rod in a valveopening direction, and a control shaft 13 connected by linkage means 22, 23 to the push-rod 9 in such a manner that rotation of the shaft 13 causes translational movement of the pushrod in a valve-opening or valve-closing direction with a degree of lost motion, whereby for a predetermined setting of the shaft 13 (shown), the valve 8 is free to (at least partially) close under liquid pressure against the action of the loading means 26, the linkage means 22, 23 being adapted to restrain the push-rod 9 from movement in a valve-opening direction subsequent to such closure of the valve. The valve 8 is disposed in a conduit 2, 2<1> which as in the parent Specification is connected to either side of the piston of an hydraulic cylinder or to the two respective chambers formed by a rotating vane in a liquid-filled casing. The piston or vane may be connected to the harness of a pilot (see Group XXXIII), the cylinder or casing being rigid with the airframe. The loading means 26 comprises a coiled spring, the precompression of which can be controlled by screw adjustment of an abutment 27. The push-rod 9 is of stepped tubular form and is slidable in the casing 10 of the control unit. The push-rod 9 is slotted at 12 so as to clear the shaft 13 which is journalled in the casing 10. A crank 22 is mounted with lostmotion on the shaft 13 by virtue of a Woodruff key 21 on the shaft which engages an elongated keyway 20 in the crank 22. A link 23 is connected between the crank 22 and the push-rod 9 at 32. In operation, with the shaft 13 in the position shown, normal forward movements by the pilot, result in liquid flow from right to left of the conduit 2, 2<1> which is insufficient to close the valve 8 against the resistance of the push-rod 9 acted on by the spring 26. This setting of the shaft 13 corresponds to the " Auto-Lock " setting of the apparatus in the parent Specification. If the liquid pressure is sufficient to close the valve 8, the resultant movement of the push-rod 9 draws the link 23 and crank 22 into the dead-centre position (the slot 20 moving over the stationary key 21). Springs 31 connected between push-rod at 32 and the crank 22, then draw the crank 22, two degrees past the dead centre to the position of Fig. 2 (not shown), in which the upper end of the keyway engages the key and a nub 34 on the link 23 engages a surface 35 of the crank 22. In this position, the push-rod 9 is locked against movement to the right and the valve 8 remains closed under liquid flow of the slightest pressure from right to left in the conduit 2, 2<1>. The valve is free to open under flow in the reverse direction. The linkage 22, 23 may be brought back into the position of Fig. 1 by clockwise rotation of the shaft 13. The key 21 then prevents movement of the linkage back to the dead-centre position and the valve 8 is unable to close, however great the pressure of flow. This corresponds to the " Forced Unlock " position of the parent Specification. The shaft 13 may then be moved back to the " Auto-Lock " position, or may be rotated further to a " Manually Locked " setting in which the key 21 travels to the lower end of the keyway 20 and draws the crank over the dead-centre position. The springs 31 may be dispensed with, or alternatively the spring 26 may be omitted, its function being fulfilled by the springs 31. In the construction shown in Fig. 4, the push-rod 9<1> is connected by a link 38 to a crank 37 mounted with lost-motion on a shaft 13<1> in a similar way to the crank 22 of Fig. 1. In this case a key 21<1> on the crank operates in a keyway 20<1> in the shaft. The crank 37 is connected by a spring link 41 to the casing 101. The link 41 comprises telescopic members 42, 43 surrounded by a compression spring 46 and has a ball-joint connection at 44, with a member 45 normally rigid with, but adjustable relative to, the casing 10. In the " Auto-Lock " setting (shown) of the shaft 131 the spring 46 acts via the crank 37 and link 38 on the push-rod 9<1> to maintain the valve open. Closure of the valves under sufficient liquid flow results in the crank and spring link 41 passing the dead-centre position, the movement being limited by the travel of the key 21<1> and the engagement of the top of the shaft 13<1> by the link 38, Fig. 5 (not shown). The shaft 131 may be rotated to " Forced Unlock " and " Manually Locked positions as before. In a further modification (not shown), the shaft 13 is disposed parallel to the axis of the casing 10 and carries a swash-plate which acts on the push-rod 9. Alternatively the shaft 13 may be disposed at an angle to the axis of the casing 10 and may carry an oblique crank. As in the parent Specification, the shaft 13 is rigid with a drum which is urged by a spiral spring into the " Manually Locked " position, the drum is connected by a flexible cable to a piston reciprocable within a tubular casing adjacent the pilot. The piston is slotted for pivotal connection with a lever, one end of which is pivoted to the casing the other end being formed with a handle. The casing may be slotted to form a gate for the lever.