Patent GB-190417018-A (GB)
Title: Improvements in Electro-pneumatic Control Systems
Filed: 1904-08-03
Granted: 1905-07-27
Abstract: 17,018. British Thomson-Houston Co., [General Electric Co.]. Aug. 3. Motors, controlling. - Relates to an improvement upon the control system described in Specification No. 3886, A.D. 1904, and consists in using an electro-pneumatic controller for the automatic acceleration of motors in a series-parallel multiple-unit system of traction, in which a number of normally open switches, actuated pneutically, vary the motor circuits, and a corresponding series of cams upon a rotated shaft permit the switches to close in a predetermined order only. Fig. 1 shows the arrangement of a single unit of a train-control system. When the contact-segments f of the mastercontroller A take up their first position, a circuit is closed from the trolley T through the contacts a<1>, a<2>, 25, bridging-member d<2> on the arm d', coil C of the electromagnetically-operated valve V, contacts 30, and bridging-member n<1> to earth E. The valve V is moved to the left, thereby admitting the fluid pressure to the pneumatic devices v<1>-v<10>, one of which is shown in Fig. 2. Two spring-pressed pistons w, placed back to back on opposite sides of the pneumatic connection are moved outwards by the fluid pressure, so as to draw the contacts f, b<1> inwards against the contacts 5, 15, to close the switch, if the cam permits. The cams i<1> ...i<4> on the shaft I permit the switches f<1> ... f<4> to close, and the cams k<1>, k<2> on the sleeve K permit the switches s, p<1>, p, s<1> to close at once, thereby connecting the motors M<1>, M in series with the mains, all the resistance R being in circuit. When the controller is moved to the second position, the coil O is energized, and its core " notches up " the shaft J, the pawl h engaging with the toothed wheel H on the shaft. The movement of the core breaks the circuit of the coil O at the contacts 29. causing the core to fall and release the pawl h by the pin h<1>. It is then attracted again to notch up the toothed wheel ; at the first notch, the switches r', r<2> are allowed to close, the fluid pressure producing a snap action; at the second notch, the switches r<3>, r' are closed, each switch cutting out one section of the resistance R. The notching up, accompanied by the closing of the switches, continues until all the resistance is cut out, too rapid cutting out being prevented by the cut-out t. The last switch r<8> withdraws the switch r<9> from the contact 27, and breaks the circuit of the coil O, preventing further movement of the shaft J, which is kept in position against the wound spring S by the engagement of the switches r<7>, r<8> with the cam j<4>. In the third position, the circuit of the coil O is broken at the contact a<5>, and the circuit of the coil P is closed. The bridging- member n' is moved into engagement with contacts 31, closing a maintaining-circuit for the coil P, and in its movement breaking the circuit of the valve-controlling coil C. This connects the pneumatic devices to atmosphere, whereupon all the switches are restored to the open position. Immediately the sleeve K is released, the circuit of the coil C is closed by the bridging-member n<2> and contacts 30, and the switches f<1>-f<4> and p, p<1> close again, the motors now being connected in parallel with half the resistance sections R in series with each motor. In the fourth position, the coil 0 is again closed, and the shaft J again rotated stepby-step, the resistance sections being cut out gradually until the motors are connected in the full parallel position, when the switch r<9> opens the coil O. The reverse rotation of the controller gives reverse motion of the motors, the switches b<1>-b<4> being closed instead of the switches f<1>-f<4>. The motors may be made to run at an intermediate speed by leaving the controller at the position 1 or 3. A modification is shown in Fig. 3, where pneumatic relay devices v<11>-v<14> are provided which connect the attracting-devices for the switches to the pressure source only for the time that this pressure is actually required. In this way the shaft J is released from the frictional retardation due to the pressure on the cams j<1>-j<4>, the smaller friction due to the spring pressure of the valves v<11>-v<14> being substituted for it.