GB501621A - Improvements in and relating to the control of electrically driven reciprocating machines - Google Patents

Abstract

501,621. Control of motors. BRITISH THOMSON-HOUSTON CO., Ltd. Nov. 8, 1937, No. 30613. Convention date, Nov. 10, 1936. [Class 38 (iii)] Continuous reversal.-In a system for controlling a reciprocating machine driven by a reversible electric motor M and comprising a pair of relay operated switches F, Fs, B, Bs which are operated alternately to connect the motor for different directions of rotation these switches are each provided with a holding circuit adapted to be completed through a different one of a pair of mechanically separate drum switches St1, St2 biassed to their off positions. Motion of the machine in one direction causes one of a pair of adjustably spaced cams 1 or 2 to engage a lever arm 11 or 21 attached to the appropriate drum switch St1 or St2 and turn this switch through stepped positions in the first of which a reduction of the motor speed is effected and in the second of which the holding circuit for the relay F8 or Be of the closed relay operated switch F or B is broken and the energizing circuit for the relay Be or Fa of the other relay operated switch is closed to effect closure of this switch and reversal of the motor. A holding circuit for this closed relay operated switch is made through the other drum switch which is then similarly operated by the other cam 2 or 1 on reverse movement of the machine to reduce the motor speed and subsequently again reverse the motor. An emergency switch is operated to stop the motor if either of the switch drums is moved to a third position. The cams 1, 2 may be adjusted to lie so close together that the respective lever arms 1<1>, 21 are always in contact with them and the drum switches are never allowed to return to their off positions whereby a short reciprocating motion of the machine may be obtained with the motor running at its reduced speed in alternate directions.