| 摘要 |
547,368. Electric motors. STANDARD TELEPHONES & CABLES, Ltd. April 11, 1941, No. 4848. Convention date, April 12, 1940. [Class 35] [Also in Groups XXXIX and XXXVII] In a continuously-driven rotary switch which may be used for connecting a number of subscribers' lines in rapid succession to a common circuit for the purpose of detecting a calling condition, as in Specification 541,768, [Group XXXIX], the connections are made through a free ball or other roller which is driven mechanically or electromagnetically around an annular track bounded on the outside by the contact bank. In Fig. 1, the ball 12 engages a bank formed with alternate active and spacer contacts 4, 5 and a feeder ring 6 to which the spacer contacts may be connected. The ball lies within the forked end of a driving arm 13 which is rotated by a motor 17, and is pressed against the contacts and the feeder ring by centrifugal force, if desired with the help of a spring. The switch may be duplicated as shown. In a modification, the arm 13 is replaced by a pair of resilient discs with dished edges forming a V- shaped peripheral groove in which the ball is wedged. In Fig. 3, the contacts 4, 5 are moulded in an insulating ring 23, preferably projecting slightly beyond it, and the ball 12, which is of steel, soft iron or high permeability alloy, runs on a track 6 under the influence of a variable magnetic field produced by an annular winding 24 lying within a magnetic structure 25 formed with two sets of poles 26, 27 on either side of the track. The track 6 may constitute a feeder ring connected or not to alternate spacer contacts, or the feed may be applied only to the latter. An electromagnetic striker may be provided for starting the ball, and the track may be inclined so that when the current is off, the ball comes to rest in a given position on the track or on another inner track. In a modification, each pole is replaced by a pair of poles one of which is shaded and the ball is made wholly or partially of non-magnetic material such as copper or bronze so that it is started by eddy current effects. In another driving arrangement, Fig. 5, the magnetic field is produced by an iron core 29 having a pair of straps 30, 31 extending diametrically and the circuit of the winding 28 includes two sets of contact springs 34 under the control of pivoted fingers which are engaged by the ball at suitable points of its travel between the poles. |
