GB752612A - Improvements relating to fluid-pressure operated actuators - Google Patents

Abstract

752,612. Pneumatic single stroke apparatus. GENERAL MOTORS CORPORATION. Aug. 18, 1954 [Aug. 31, 1953], No. 24027/54. Class 8(2). [Also in Groups XXIX and XXX] A sell-locking, fluid-pressure operated actuator comprises a cylinder containing a piston and a screw shaft rotated by movement of the piston and associated with a pair of lock devices, either of which when released permits rotation of the shaft, and consequent linear movement of the piston, with the other device locked. One lock device is released by fluid-pressure operated means on applying fluid-pressure to either end of the cylinder, the other device is released when non-fluid-pressure operation of the actuator is desired. Two or more actuators may be coupled together and act in synchronism even if the fluidpressure releasable lock device of one of the actuators fails to release on the application of such pressure. An actuator comprises a cylinder 11 and a piston 26 co-operating with a screw shaft 38. One end of shaft 38 is formed as a cam 43 having flats 45 and forming part of a roller-brake 100 for locking the shaft against rotation. Brake 100 includes pairs of rollers 46, 47 disposed on the flats 45 and spring urged into wedging engagement with an annular member 55. A member 50 has fingers 49 coaxial with arcuate portions of the cam 43 and has a loose connection with the cam, permitting slight angular movement relative thereto. Member 50 carries a helical gear 86 meshing with a gear keyed to interconnecting means between adjacent actuators. A roller-brake 150 is also provided and is of similar construction to brake 100, having a cam 60 fixed relative to the cylinder 11, and a member 68 similar to member 50 but co-operating with pistons 73, 74 for actuation thereby and having fingers 67 encompassed by the annular member 55 which is common to both brakes. On the application of fluid pressure to either end of the cylinder 11, fluid is also admitted to either a chamber 83 or a chamber 84 to actuate the pistons 73, 74 and move the member 68 in either direction to displace one roller of each pair and thus permit rotation of the annular member 55 in the desired direction. Thus on applying pressure to, say, a chamber 28 of the cylinder 11, brake 150 is released, the piston 26 moves to the right, rotating the screw shaft 38, which rotation is transmitted through the locked roller-brake 100 to the member 50 which rotates'the helical gear 86, and synchronised movement of adjacent actuators is ensured by the interconnecting means. If the roller-brake 150 of one of the actuators fails to release, the helical gear 86 of this actuator is rotated by the other actuators and hence the member 50 is rotated. One roller of each pair of rollers 46, 47 is displaced by virtue of the limited movement, permitted between member 50 and the cam 43, and thus the roller brake 100 is released. Cam 43 is rotated by the member 50, the shaft 38 is consequently rotated and the piston 26 displaced. The actuators may be operated in synchronism by auxiliary means, such as an electric motor driving a shaft forming part of the interconnecting means between the actuators, should the fluid-pressure system fail. In this case the roller-brakes 100 are released on rotation of the helical gears 86 as described above. Specification 730,257 is referred to.