Patent GB-235858-A (GB)
Title: Improvements in floor levelling devices for electric elevators
IPC: B66B1/08
Filed: 1925-05-25
Abstract: 235,858. Waygood-Otis, Ltd., (Assignees of Waite, R. A., and Lautrup, G. W.). June 18, 1924, [Convention date]. Systems for continuous-current motors only. - In lifts which are driven at various speeds by voltage variation of a generator driving the hoisting motor, the lift is levelled with a landing by variable speed of the motor which is less than its normal lowest hoisting speed and is controlled by a levelling switch within the levelling zone at each landing. Power is supplied at a variable voltage to the hoisting motor M by a generator GE which is driven by a motor E having a shunt field EF. The variation in voltage is obtained by controlling the separately excited generator field GF. The levelling switch L is mounted on top of the lift K and when actuated by cams 2, 3 at a landing inserts additional resistance in series with the field GF thus reducing the speed of the motor M. The switch comprises arms 86, 88 pivoted on a double arm 164 which is connected to a motor LM on top of the lift by an arm 85 and connection 84. The arms 86, 88 each have contacts 169, 171 co-operating with contacts on the arm 164, the contact 171 .being for fast speed and the other contact for slow speed. These contacts are opened successively as the roller 87 at the end of the arm 86 passes on to the surfaces 201, 202 of the cam 2 on an upward journey. When the segment 5 of the switch A on the lift has been moved by the attendant when starting the lift to bridge the switch fingers 6, 8, a circuit is completed for the motor LM and the arms 86, 88 are moved away from the cams 2, 3, and are kept away until the arm 4 of the switch is centred. If it is desired to move the lift from a stationary position at a landing to stop at the landing above, the arm 4 of the switch A is moved to the left and the segment 5 bridges in succession to switch fingers 6 - - 11. When the fingers 6, 7 are bridged, a circuit is completed for the actuating coils 19, 21 of the up reversing switch B and the auxiliary field switch H. The upper contacts 25, 26, 34 of switch H close and the common feed from the + supply line to the coils of the accelerating switches D, E, F, G is closed. The closing of contact 26 puts full field on the motor M by short circuiting the economizing resistance SR in series with field MF. The closing of contact 34 releases the brake BR and opens switch 37 thereby reducing heating of the magnet coil by inserting a resistance ABR in series with coil 40 and also placing the coil of an auxiliary accelerating switch O and its series resistance OR in parallel with a resistance ABR. The energization of coil 44 of switch 0 closes contact 45 for timing the accelerating switches E, F, G. By this means the acceleration of the lift above low speed is prevented until the brake has been released. The opening of contact 46 of switch H opens the circuit of resistance PRB1 which is in parallel with the resistances PBR and PBR2 and with the coil of the brake. The energization of the coil 19 closes the contacts 57, 58, 73 and opens the contacts 74, 75. The switches B, C are interlocked by a pivotally mounted walking beam 54 which engages catches on the cores 55, 56 so that while one is closed the other is held open. The closing of the contacts 57, 58 completes the circuit for the field GF of the generator GE through the coils 64, 66 of relays N, Q, but these relays do not operate as the current is weak owing to the resistance GFR being in series with these coils and the field GF. The generator GE will, however, generate sufficient voltage to start the motor M. The closing of contact 73 does not complete any circuit. When the fingers 6 - - 8 are bridged the actuating coil 77 of levelling switch relay T is put in circuit and this completes a circuit for the motor LM which moves the arms 86, 88 as before mentioned. When the switches B, H, T are closed as described, the motor M runs at a speed corresponding to the voltage of the generator GE. When the fingers 6 - - 9 are bridged, the coil 94 of the accelerating switch D is put in circuit and its top contacts close. The closing of contact 108 completes a circuit for holding the coils of the switches 13, H, T which is independent of the circuit originally completed. The closing of contact 118 short circuits part of resistance GFR and the speed of the motor is increased. The whole of this resistance is short circuited when the switches D, E, F, G have been energized and the fingers 6 - - 11 bridged. The action of all the switches D - G is delayed by the inductance 140. The opening of contact 28 of switch G inserts a resistance SFR in series with the field MF of motor M thus causing the motor to run faster. When the motor is running at full speed the switches B, D, E, F, G, H, N, 0, Q, T, Z are energized and the switches P, R, V, X, Y de-energized. A governor GOV driven by the motor M has a contact 161 which at normal speed is open. If the speed is too high the contact closes and effects the short circuiting of the coil 154 of switch Z, series resistance ZR and resistance SFR. This cuts out the resistance SFR from the circuit of the motor field MF and re-inserts the last part of the resistance GFR in the circuit of the generator field GF so that the speed of the motor is decreased. When the lift approaches the landing above, the attendant centres the arm 4 thus disconnecting the fingers 7 - - 11 from the finger 6. The resistance GFR is inserted in successive steps, the voltage of the generator is reduced, and the speed of the motor M is reduced gradually. A sudden change is prevented as each step of the resistance is inserted by the action of the resistance GFR in parallel with the field GF and coils of switches N, Q. The arms 86, 88 move back towards the cams 2, 3 when the motor LM is put out of circuit. When the roller 87 on arm 86 strikes against surface 163 of the cam 2, the upper contacts of the levelling switch are closed. The closing of the contact 169 completes a circuit for the actuating coils of up reversing switch B and switch H and either maintains or re-establishes the circuits to generator field GF. The closing of contact 171 establishes another short circuit round the resistance XFR, this resistance being also short circuited by the contact 122 of switch V. When the contact 169 closes, the coil 166 of switch P is energized and closes its contact thus completing the circuit for the coil of the switch R which closes its three upper contacts and opens its lower contact 71. The opening of the contact 71 removes the short circuit from the portion of the resistance GFR between the points 79, 205 and all the resistance is then in the field. The lift is then running at a speed slightly less than the lowest speed obtainable by the. switch A. The upper contact 177 of switch R is arranged to connect fingers 6, 180 in order that the attendant can take the control from the levelling switch and operate the lift up or down at any time during the levelling operation. The closing of contact 100 puts coil of switch X in circuit and its contact 194 is closed. An inductance 188 retards the closing. The closing of contact 198 puts coil 196 of switch Y in circuit and its contacts 49, 198 are opened. The opening of the contact 198 removes the short circuit round a part of the resistance FS which is in parallel with the series field GSF of the generator GE, thus in. creasing the strength of the series field for the levelling operation. The opening of contact 49 opens a parallel circuit around the brake magnet through the resistances PBR1, PBR2. The lift is now running at the highest speed of the levelling operation. As the lift nears the landing the roller 87 runs on to the surface 201 thereby opening contact 171 and weakening the generator field GF by inserting the resistance XFR in series with resistance GFR. The lift then travels at a lower speed. When the roller 87 passes on to the surface 202, the contact 169 is opened, the field GF and coil 40 of brake magnet BR are disconnected from the line, and the lift is stopped. The switches are now in position for the next operation. Should the lift overtravel, the low speed contact of the arm 88 is closed by the cam 3, and circuits are completed which reverse the motion of the lift and return it to the landing. The coil 40 of brake magnet BR has parallel resistances PBR, PBR1, PBR2, which permit variable speeds or intensities of brake application.