Patent GB-190503855-A (GB)
Title: Improvements in and connected with Apparatus for Automatically Accelerating Electric Motors.
Inventor: MOORE ERNEST SHERWOOD WOOLLARD
Filed: 1905-02-24
Granted: 1906-02-24
Abstract: 3855. Moore, E. S. W., and Bennitt, W. B. Feb. 24. Switches.-Regulating-switches for electric motors for lifts, capstans, hoists, and the like comprise a set of fixed contact-springs, a stepped cylindrical contact-plate fixed to the same spindle with a ratchet sector, and means for raising the spindle bearings so as to bring the ratchet into gear with a driving pawl constantly reciprocated by the motor and simultaneously to bring the contact-plate into line with the springs. Thus, the stepped plate is turned through part of a revolution, and the resi,tances are cut out automatically. The spindle can be made to drop at will or automatically when the speed of the motor becomes too great, and so reinsert the resistances. The fixed contacts m<1> &c., Figs. 2 and 3, are preferably arranged in two rows above the curved contact-plate A, which is shown separately in Fig. 4 and developed in Fig. 6. The spindle B, on the sleeve B<1> of which the plate A is mounted by means of arms A<1>, A' fixed to bosses b<1>, b<2>, is journalled in the ends of a pair of arms C. pivoted at D, is normally held down by gravity, and is capable of being raised by a lever E composed of a pair of arms e', Fig. 3, pivoted by studs f to fixed bearings F, a cross-bar e', and a straight part e linked to the core of the operating-solenoid G, Fig. 2, which may also have the function of holding off a brake. The arms e<1> embrace the levers C, and their pivoted ends, shaped as at g, g<1>, g<2>, Fig. 7, bear upon roller-covered studs c<2> fixed to the levers C. When the solenoid core is raised, the lever E is turned, and the studs c<2> are caused to roll up the inclined edges' g from the smaller circles g<2> to the larger g<1>, where they are retained till the core drops again. Alternatively, the cams for raising the levers C may be operated from the solenoid by a rack and pinion or other suitable means. The spindle B extends through holes in the studs f large enough to admit of its up-and-down motion, and to one of its outside ends is fixed the rack H, Figs. 2 and 3, which in the raised position is rotated step by step by means of a pawl j<1> carried by a pivoted arm J and oscillated by means of a pin j<2> and a cam-groove k on the motor-driven shaft K<1>. A fixed detent n retains the rack after each step. The rack sector terminates in a concentric plain rim, on reaching which the oscillations of the pawl J<1> cease to have any further effect. Should the plate A be allowed to fall at this point,-the-rackis released from the pawl j<1>, which is held up by a stop k<1>, and is turned back to starting position by a counterweight L or spring. When the series winding is to be cut out from a compound-wound motor, the last two steps a<6>, a<7> of the plate A, Fig. 5, co-operate with contact-springs m<13>, M<14>, Fig. 3, for this purpose. When the starting of the motor is performed through the agency of a current, a pair of spring contacts p, Fig. 3, bridged by a contact M attached to the plate A, establish the starting-current only when the plate is in its lower ' off ' position. When extra initial resistance is required, the coils are connected to the first few spring contacts, and are cut out simply through the raising of the solenoid core, or through a pawl q, Fig. 7, attached to the lever E. Again, the lever E may be operated and the starting-resistances reinserted, when the speed of the motor becomes excessive by means of a centrifugal arrangement, Fig. 8, consisting of a shaft N rotated by the motor, a heavy ring N<1>, a link r to a sliding block r<1>, and a double lever P, R which turns the lever E. The rear part of the circular cam edge g<1> is also cut away as shown at g<3>, on reaching which part the stud c' falls and allows the plate A to drop away from the fixed contacts.