GB774303A - Improvements in or relating to torque-actuated devices for use with electric motors - Google Patents

Abstract

774,303. Electric motor driving arrangements. ROTORK ENGINEERING CO., Ltd. Sept. ) 12. 1955 [July 5, 1954], No. 19655/54. Class 35. [Also in. Groups XXIX and XXXVII] When a gate valve reaches its closed position or meets an obstruction, a mounting member 18 for the electric driving motor of the valve is turned to a limited extent relative to the body 31, the said member being subjected to torque about the output shaft 22. The member 18 is supported on the body 31 by means of rubber or other resilient blocks 42 which are stressed in shear as a result of the rotary movement of the member 18, and, owing to the elasticity of the blocks, the amount of movement depends upon the torque applied. The member 18 carries a cam 44 which is adjustable circumferentially and engages a push rod 47 normally urged upwardly by a leaf spring 48. When the mounting member turns as a result of torque reaction, the push rod is moved downwardly to operate switch 52 and to de-energize the driving motor. A limit switch 67 is operated when the valve is fully opened by means of a non-rotatable nut 65 co-operating with a screwed bush 63 mounted on a rotatable sleeve 57. This sleeve is secured to a tubular nut 58 which is free to rotate but is located against axial displacement, the nut engaging a thread upon the valve spindle 14 whereby turning of the nut effects vertical movement of the spindle. A hand-wheel 24 is coupled to a bush within the sleeve 57 when clutch element 23 engages screws 68. The clutch element can be raised to disconnect the hand-wheel by means of shaft 70 which has a crank 73 engaging groove 74, a coiled spring acting upon the shaft 70-normally keeping the clutch element in its engaged position. The nut 65 may be used for indicating the position of the valve member. When the axis of the output shaft 22 is inclined to the vertical, the cam member 44 may be replaced by a pin which operates the push rod 47 through a bell crank lever, Fig. 5 (not shown). In a modification for valves of larger size, Figs. 6, 7 (not shown), the hand-wheel is connected permanently to the valve spindle which is rotated without axial movement for working the valve member. The member 18 is mounted on the body 31 by means of composite cushion members moulded from soft rubber but having metal washer inserts so as to be resistant to axial compression but to respond freely to angular movement of the mounting member. The valve spindle is coupled to the motor shaft by means of a slidable dog clutch, normally spring-urged into engagement but disengageable by means of a fork having pins co-operating with a groove in the clutch element. In addition to the torqueresponsive switch, limit switches for the opening and closing movements of the valve are provided. The torque-responsive switch is effective in either direction of movement and is actuated by means of an arm which is fixed to the member 18 and carries a partly spherical terminal member co-operating with a cam having a concave curved operative surface. The limit switches are operated by a rocking lever carrying a quadrant having teeth meshing with a pinion driven by the valve spindle.