Patent GB-190502190-A (GB)
Title: Improvements in Starting Switches for Electric Motors
Inventor: CLATWORTHY WALTER ANGOVE
Filed: 1905-02-03
Granted: 1905-09-28
Abstract: 2190. Clatworthy, W. A., Holmes, A., Holmes, J. H., Holmes, L. W., and Holmes, E., [trading as Holmes & Co., J. H.]. Feb. 3. Switches.-In a motor starter, especially for motors which require to be started frequently for a few revolutions only, a separate rapid-moving switch is first operated to prevent sparking at the rheostat contacts, and the forward or backward movement of the rheostat follows under the influence of an overbalanced lever. Fig. 3 shows the switch in the initial position before starting, and Fig. 5 is a diagram of the circuit connexions. The switch is turned on by moving the handle M, fixed to a wheel F with projecting or recessed edges f, which catch the end of a lever C pivoted at c and connected by a spring D to a lever B. The latter is thus thrown suddenly to the right, striking against one of the projections a<2> on the contactlever A and making contact between the terminals E, E, a projection on the lever C pushing the contacts home if the spring D has not done so. An electro-magnet N', preferably connected in series with the rheostat resistances in the manner shown in Fig. 5, when energized by the closing of the switch A draws up its armature n and unlatches the rheostat arm G. The turning of the handle M also causes a lever L, carrying adjustablyplaced weights l, to slide longitudinally through a hole in a rigid attachment H of the rheostat arm by means of a chain or cord Q passing round a drum J fastened to the handle. If necessary to prevent the return of the handle on accidentally releasing hold, a fixed " sustaining device " may be provided. Alternative methods of overbalancing the lever L, for example by a rack and pinion, crank, or cam, may be used. The descent of the arm G carried down by the tilting of the lever L is checked by a dashpot or like retarding-device P. Should the handle M during or after the downward movement of the arm G be turned back, the first result is that the notch f in the disc F catches and turns the lever C, which causes the lever B to be thrown suddenly to the left, striking the switch blade A and breaking circuit. The switch blade A then meets contacts n<2>, forming a short-circuit round the no-load release magnet N and allowing its armature k<1> carried by the lever K to be pulled off by the spring k<2>, so disconnecting the contacts k. Under the influence of the lever L, which has been overbalanced in the other direction by the backward movement of the handle M, the rheostat arm returns to its original position, a projection h pushing back the lever K and re-connecting the contacts k. In a slightlymodified form, the connexions of which are shown in Fig. 6, the magnet N<2> serves also as the no-load release, and the magnet N is dispensed with. The lever K is then held down by one end of the armature n, Fig. 3, pressing upon a lever x which bears upon an arm y fastened to the lever k. An additional winding in series with the motor armature may be placed on the magnet N<2>, which winding is short-circuited as the rheostat arm advances.