Patent GB-630522-A (GB)
Title: Improvements in or relating to an electric motor or like controller
IPC: H01H9/26
Filed: 1947-06-25
Abstract: 630,522. Controllers: switchesheld set and freed mechanically : switch contacts. FELT & TARRANT MANUFACTURING CO. June 25, 1947, No. 16747. Convention date, Feb. 23, 1945. [Classes 38(iii) and  38(v)]  A controller for a direct-current circuit including a pair of make-and-break contacts. comprises a switch operable to control the flow of current to said contacts, a polarity-changer interposed in said circuit between said switch and said contacts and operable to reverse the flow of current to said contacts, a manually reciprocable member for closing and opening said switch, and control mechanism interposed between said reciprocable member and said polarity-changer to cyclically operate said polarity-changer after a predetermined plurality of operations of. said switch by said reciprocable member. An electric motor is controlled by means of a main switch 23 and a reversing switch 24 having a common operating member 25 and handle 28, the reversing switch being operated after a pre-determined number of operations of the main switch. Movement of the handle 28 to the left-hand position causes a lever 91 to exert an upward pull, through an arm 89 and link 88, on the operating- member of the switch 23 and move it to the " on " position. Rotation of the lever 91 turns its depending arm 97 to move a lever 104 in a clockwise direction from the position shown through a pin-and-slot.connection 98-105. A pawl 108 engages a pair of aligned teeth in ratchets 81 and 112 to rotate these ratchets in a clockwise direction, return' movement of the ratchet 81 due to spring 86 being prevented by pawl 115. Rotation of the ratchet 81 turns the rotor of the reversing switch. Movement of the handle 28 back to its original position operates the switch 23 to the off " position. The arm 97 moves the lever 104 in the counter-clockwise direction. The pawl 108 engages the next tooth of the ratchet 112, whilst the pawl 115 releasably holds the ratchets 81 and 112 in position. Thereafter, a cam surface 107 engages pawl 115 and moves it out of latching engagement with ratchet 81. The ratchet 81 and the rotor of the reversing switch are then rotated by the spring 86. The pawl 108 is not engaged by any of the teeth of the ratchet 81 during such return movement or during the next ratchet-operating movement of the pawl. Thus, when the handle 28 is next moved to the " on " position and the switch 23 is closed, the pawl 108 indexes the ratchet 112 but does not move the ratchet 81, the reversing switch remaining in its last position. This cycle may be repeated, alternate operations of the member 25 to move switch 23 to the " on " position effecting reversal of the polarity of the motor circuit. An application of the invention is shown in Fig. 9, an electric motor 16, which, for example, drives a calculating-machine, having a governor 17 which makes and breaks contacts 19 in series with the motor for controlling the speed thereof. Despite the use of a condenser 21 sputtering of metal occurs between the make-and-break contacts and the reverser 24 is utilized to reverse periodically the polarity of the contacts so reducing the harmful effects of such transfer of metal. The reversing switch is described as comprising rotor and stator members of insulating material with the necessary contacts and conductors embedded therein. The rotor has limited angular movement with regard to the stator due to a pin-andslot coupling there between.