Patent GB-190417809-A (GB)
Title: Improvements in Electric Controllers
Filed: 1904-08-16
Granted: 1905-07-20
Abstract: 17,809. British Thomson-Houston Co., [General Electric Co.]. Aug. 16. Motors, controlling.-A controller of the drum type comprises movable and fixed contacts which are arranged to connect the motor to a lowpotential circuit, to increase its speed, and, without breaking the circuit, to change the motor to a high-potential circuit and again increase its speed, a contact-finger being moved out of engagement to prevent a connection with the low-potential supply should the controller arm be moved backwards from the high-potential side. The fixed contactfingers are mounted upon an insulating-block, one portion of which 46<a>, Fig. 1, may be turned upon a pivot 47 to bring the contact-finger S, which it carries, out of contact with the segment S<1>, as indicated in Fig. 2. Mounted upon a horizontal insulating-disc 53 is a set of fixed contacts 54, with which engage the movable contacts 55, 55<a>, connected with the lowermost segment T'. The arrangement of the connections in the controller is shown for a three-wire system in Fig. 8, and Figs. 1 and 2 show the first starting position, when the field winding G<4> is connected to the high-potential source by way of the contact-finger T, segment T<1>, contact 55, elongated contact 54, lead 67, and lead 78, while the armature will be connected to the low-potential source from the positive wire to the neutral wire by way of the contact-finger T, the segments T<1>, F<1>, contactfinger F, lead 74, and back by the lead 72, starting- resistance R<1>, contact-finger A, segments A', S<1>, and the contact-finger S. In the movement of the controller through the first four positions, the contact 55 remains in engagement with the elongated contact 54, so that the field circuit remains unchanged, but the sections of the starting-resistance R' are gradually cut out by the engagement of the contact-fingers A, B, C, D with the segments A', B<1>, C<1>, D<1>. Further movement gradually cuts in the field resistance R<a>. Passing from the position 18 to 19 the armature connections are changed from the low-potential source to the high-potential source, the contact-fingers E, R engaging the contact-segments E<2>, R' before the contact-fingers S, D leave the con tact-segments S', D<1>. The position 19 corresponds with the position 1, and the positions 19-36 correspond with positions 1-18. To prevent connection between the low-potential mains upon a backward movement of the controller, the finger S, to which the neutral wire is connected, is moved out of contact when the controller is turned beyond the position 18, and it cannot again be brought into contact until after the controller has been moved to the ' off ' position. Figs. 1 to 4 show one method by which the pivoted contact-finger S is operated. The pivot 47 is provided with a crank 54 connected with a toggle composed of the links 55<x>, 56, the link 56 being connected to the back-plate 40 of the controller casing. The coiled spring 58 serves to carry the toggle to either limiting position when once carried in either direction beyond the centre line. The lower projection 60 of the cam 59 engages the roller 62 to move away the finger S, the cam being so arranged that the finger is withdrawn from the contact only after the connections with the low-potential source have been made. The finger S is moved back into contact by the overhanging projection 61 of the cam 59 engaging the roller 62. In the finger-operated mechanism for the same purpose, shown in Fig. 5, the pivoted piece 46<a> is provided with a laterally-projecting crank-arm 66, which is adapted to engage, at its outer end 70, with the elongated cam 67 on the disc 68 secured to the controller shaft. In the movement of the disc 68 in one direction, the end 70 of the arm 66 will be guided by the upturned lip 69 to engage the groove so as to keep the contact-finger S in contact with S', while, in the return movement of the disc, the arm 66 will pass over the upper surface of the cam 67 by reason of the inclined end 67<a>. If the controller be moved in the opposite direction, the motor will be reversed, and in this case, as shown in Fig. 8, the field excitation is always at a minimum, and variation of speed is brought about by cutting out the starting-resistance R' from the armature circuit in four steps.