GB611387A - Linear actuator - Google Patents

Abstract

611,387. Electric motor control systems. CHICAGO PNEUMATIC TOOL CO. April 30, 1946, No. 13022. Convention date, July 17, 1945. [Class 38 (iii)] [Also in Group XXX] In a reversible motordriven screw-and-nut actuator for aircraft controls and the like, having a main housing adapted for attachment to a first body, a connecting head adapted for attachment to the bodies to relative movement in either direction for stopping the motor, the stopping means includes a lever interposed between the housing and the first body. In Fig. 1, the motor 16, in a housing 61 drives the separately housed gearing 15 which rotates the screw 14 in the axially movable, internally-threaded sleeve 21 so that the head 23 attached thereto is extended or withdrawn from the main casing 27 according to the direction of rotation of the motor, and pivoted to the casing 27 by means of a pin 118 is a bellcrank lever 19 having two arms, the shorter of which is pivoted at its free end to anchor bracket 11, the free end of the other being pivoted to a switch actuating rod 81 extending through helical spring 17 which normally prevents any pivotal movement between the lever and the casing, but permits such pivotal movement upon development of a predetermined force between the housing and the anchor bracket which is set up by the arm 12 being forced against one of stops 116, 121. Spring 17 contained in housing 78 is maintained in a preloaded condition by washers 93, 94, normally seating against the ends of housing 78, one of which can be unseated by shoulders 92 or 97 on rod 81, upon the development of a predetermined pulling or pushing force between casing 27 and anchor bracket 11. Movement of rod 81 in either direction away from an intermediate normal position actuates switch 18, in housing 64, which operates either of relays 111 or 114, Fig. 5, which actuates switches 112 or 115 connecting the stator to a three-phase A.C. supply, these switches being arranged to provide opposite phase rotation, thereby rotating the motor in opposite directions. Lever 19, rod 81 and switch 18 remain in an off-normal position after the motor stops, the circuit being arranged to prevent connection of the motor to the supply until after the reversing switch 106 has been moved to its opposite position. A sleeve guide 25 anchored to the main housing has a wiper 29 attached to its outer end for cleaning the external surface of sleeve 21 as it slides in and out of said guide.