Patent GB-301473-A (GB)
Title: Improvements in or relating to control systems for elevators, hoists and the like
IPC: B66B1/44
Filed: 1928-11-30
Abstract: .301,473. Metropolitan-Vickers Electrical Co., Ltd., (Assignees of Eames, W. F.). Nov. 30, 1927, [Convention date]. Electric plant.-In lift. systems actuated by electric motors controlled on the Ward Leonard principle means are provided for varying the acceleration and deceleration which would normally be obtained in certain stages of the operation so that, e.g. the acceleration curve is of the shape 117, 119, Fig. 2, instead of the form 118, 120, 119. The invention also provides means whereby the lifts run at - constant speed under varying load conditions. The armature EM' of the hoisting motor EM is connected in loop circuit with the armature G' of a generator G which is of the cumulative compound wound type including a series field winding GSF and a separately excited field winding GF. The armature G<1> is coupled directly to the armature M<1> of a motor M which is of the shunt wound type and has its field winding MF connected in parallel with the armature M<1>. The direction and speed of the motor EM are controlled by an up direction switch 1, down direction switch 2, and speed relays 3, 5, 6. The accurate stopping of the cage C level with any of the floors is determined by the operation of inductor relays carried by the cage which co-operate with inductor plates mounted in the well adjacent to each floor. The inductor relays comprise a high speed up relay 10, a high speed down relay 9, an up intermediate speed relay 8, and a down intermediate speed relay 7. Stopping is caused by a mechanical switch 11 which is actuated by a retiring magnet 12 and cams 13, one of which is mounted on the well adjacent to each floor. The motor speed is maintained constant under varying loads at low speeds by so proportioning the series field winding GSF that cumulative compounding of the generator is achieved to increase the voltage supplied to the motor under an increase in load, and to decrease the voltage under light loads in such proportions as to counteract the normal characteristic of the hoisting motor to reduce its speed as the load thereon increases. Since the compounding of the generator is insufficient to maintain an accurate speed regulation at higher speeds, an additional means for regulating the speed is provided by varying the excitation current supplied to the separately excited generator field winding GF in some proportion to the load on the cage. Speed regulation is accomplished by a multiple finger relay 14 comprising an upper magnetic plate 15 and a lower magnetic plate 16 between which are mounted a series coil 17 and a shunt coil 18. The coil 17 is in series relation with the generator armature G<1> and motor armature EM<1>, and the shunt coil in parallel with the motor and generator armatures. Movable contact fingers 19 - - 22 are pivoted on the plate 16, and their tips are insulated at 23 from the main body of the relay, thereby forming contact members 24 - - 27 which may be moved into engagement with stationary contacts 28 - - 31. A locking bar 32 is disposed adjacent to the arms 19 - - 21 and is normally held in contact engaging position by a spring 33. This bar is moved to open contact position by a magnet 34 acting through a lever 35. In order to cause the cage to ascend from the bottom floor, the attendant moves the cage switch handle Cs to the left, thereby supplying current to the switch 1 through the engagement of contacts 40, 41, 42. Switch 1 completes a circuit for energizing the separately excited field winding GF with current in one direction. The generator G now supplies the motor armature EM<1>, and the cage starts upwards. The switch handle Cs is now moved further to the left to complete a circuit for the speed relay 5, which includes contact members 68 of up intermediate speed relay 8, coil of a holding relay 70, coil of speed relay 5, door switch devices 73, 74, and contact members of a gate switch 76. The speed relay 5 operates to short-circuit section 58 of resistance, and the cage runs at its lower intermediate speed. The operation of relay 5 completes a circuit for energizing the magnet 12 of switch 11 to move the switch contact member 90 to the position shown. In its retracted position the switch 11 engages its contact members 89, 90 to complete (1) a self-holding circuit for up direction switch 1, and (2) a circuit for energizing speed relay 3. The operation of relay 3 performs two functions, (1) that of short-circuiting section 59 of resistance, and (2) that of short-circuiting a portion of a discharge resistance 98 connected in parallel to the separately excited field winding GF. An increased amount of current is now supplied to the field winding GF, and the motor is accelerated to its next higher speed, i.e. its second intermediate speed. When the switch Cs is moved to its extreme position a circuit will be partially completed for energizing speed relay 6, which circuit extends from line conductor L' through conductors 43, 44, contact members 41, 40, 101, conductors 102, 103, contact members 104, high-speed up inductor relay 10, conductor 105, coil of a holding relay 106, and conductor relay 6, conductor 110, contact members a of a counter electromotive force relay 111, and conductors 112, 72, door switches 73, 74, contacts of gate switch 76 to line conductor L<2>, and the other branch extends by way of conductor 113, coil of motor field relay 114, conductor 115, contact members a of a second counter-electromotive force relay 116, conductor 117, contact members of counter-electromotive force relay 111 to conductors 112 and 72. The relay 111 delays the operation of the high-speed relay 6, thereby delaying the time in the acceleration period when full voltage will be supplied to the field winding GF. The relays 111, 116 produce the substantially smooth acceleration curve 117, Fig. 2. The relay 111 is selected so that it will operate upon receiving a counter-electromotive force of a predetermined value, e.g. 100 volts, and is adjusted so that it will be energized at the point 121 in the acceleration curve. This relay completes the partially closed circuit for speed relay 6, which on coming into operation further reduces the resistance in circuit with the field winding GF by short-circuiting the resistance section 56. The relay 116 operates at a higher value of counterelectromotive force, e.g. 200 volts, and is energized at the point 127. This relay completes the partially closed circuit for the motor field relay 114, the contact members of which normally short-circuit the resistance 125, thereby ensuring full field strength in the hoisting motor field. When the relay 114 is energized, the resistance 125 is inserted in the circuit of the hoisting motor field winding EMF causing a weakening of the field strength and a consequent speeding- up of the motor EM. If the attendant moves the switch Cs to full-speed position and then returns it to neutral position the relay 6 will not be energized, and the cage will accelerate only to. the intermediate speed preparatory to deceleration to stop at the next floor. The closing of relay 6 will energize relay 4 and the opening of the contact members b of the latter will permit the former to control the exclusion of the resistance sections 56, 57. The sections 60 - - 63 of the resistance in circuit with the winding GF are connected to be short-circuited by the operation of the contact members 24 - - 27. The bar 32 holds the members in closed circuit position, thereby excluding sections 60 - - 63 from the generator field circuit and permitting full field excitation during the acceleration period. As the voltage supplied to the armature EM<1> increases, the bar 32 will be released from the magnet 34, but since the acceleration current is of such high value at this time, the coil 17 will exert such a magnetizing influence on the plates 15, 16 that the arms 19 - - 22 will remain in circuit closing position. This magnetic influence will decrease as the speed of the cage increases. Air gaps between the arms 19 - - 22 and adjustable projections 130 - - 133 on the plate 15 are adjusted so that different values of current in the coil 17 will cause certain of the arms 19 - - 22 to remain in circuit closing position while the others. will be dropped out. If the load in the cage is heavy, e.g. the current in the coil 17 at the end of the acceleration period will be such that all the arms will be in circuit-closing position, and a high voltage will be supplied to the motor EM. If the load is light, the current will not be sufficient to hold the arm 19 and this arm will drop out to insert section 60 in the field circuit, thus reducing the voltage supplied to the motor EM so that the cage will travel at the same speed as when it was heavily loaded. If the weight of the loaded cage equals the counterweight, the current in coil 17 will only be of such value as is required to overcome friction losses in the apparatus, and the arm 20 will be dropped out to insert sections 60, 61 to cause a proportionate reduction in the voltage. If the cage is travelling down with a light load, i.e. one just exceeding the counterweight, the current in the coil 17 will be a regenerative one, and under these conditions, arm 21 will drop out as well as arms 19, 20 to insert sections 60 - - 62. The flux through the plates 15, 16 is maintained in the same direction for all conditions of loading by the coil 18, the ampere turns of which exceed the ampere turns of the coil 17. With extreme over-hauling loads the flux value in the plates will be further reduced and all the arms will drop to insert the resistance sections 60 - - 63 in circuit. When it is desired to stop the cage at a given floor, the switch Cs is centred, thereby energizing the coils of the inductor relays 7 - - 10, and breaking the original circuit for relays 6, 114, which relays remain energized since a holding circuit was completed through relay 106