GB615418A - Control apparatus for controlling the operation of drive means for placing a useful load in a desired position - Google Patents

Abstract

615,418. Electric control apparatus. YAR. DENY, M. N. May 3, 1945, No. 11257. [Class 40 (i)] Apparatus for controlling a reversible motor so as to place a load in a selected position, includes a contact element which is driven by the motor to search for a gap between two conductors of a control element and is characterized by the provision of a switch which reduces the speed of the motor for a limited movement after reversal. In one arrangement, Fig. 1, contact arms 15 mounted on a shaft 83 engage conducting members 1, 2 of the control elements, any number of which may be provided. The shaft 83 carrying the contact members is driven by a series wound motor with an armature 20 and reversing windings 21, 22 normally relays 23, 24 are operated and the motor is disconnected from the supply terminals 26, 44. When a particular element is connected by a switch 31, the contact arm and a conducting member short-circuit the associated relay which falls back and completes a circuit for the corresponding winding 21 or 22, in series with the armature 20 to drive the motor and the contact arm towards the gap 3 between the conducting members 1, 2. When the contact element passes the gap, the relays change over, the motor reverses and the metal segment 59 of a rotary switch temporarily engages a brush 61 to shunt the armature by the idle field winding and the resistance 64 in series. When the contact arm bridges the conducting members, the motor is disconnected and stops. Supplementary means to prevent hunting are provided in the form of a frictional coupling 82 with stops to limit the displacement and tongues 81 of rubber which engage the disc 66 and which increase their normally small resistance during a reversal. The edges of the gap may be raised, Fig. 12. The rotary switch comprises a shaft 58 carrying the conducting segment 59 and an insulating segment 60 of larger diameter which frictionally engages the disc 66. A brush 61 engages the segments. The disc 66 does not engage the conducting segment 59 and the switch turns only whilst the insulating segment is engaged after reversal. A spring 54 holds the edge of the insulating segment against the disc. Modifications. The rotary switch may comprise a disc 90, Figs. 2 and 4, frictionally engaged by the disc 66 but limited in rotation by two stops 91. When either stop is engaged a contact is opened and the circuit including the contacts is closed only during the traverse of the switch between the stops during a reversal. The resistance 64 may be replaced by the coil of an electric bell vibrator, the arm of which may interrupt the main current supply to slow the motor down. Alternatively, the interruptions may be produced by a switch controlled by a governor geared to the shaft. The Specification includes a number of examples including series wound and shunt wound motors. The motors can be operated by either A.C. or D.C.