Patent GB-663886-A (GB)
Title: Speed control of conveyor drives
IPC: B65G23/00
Filed: 1949-05-04
Abstract: 663,886. Change-speed control. WEBB CO., J. B. May 4, 1949 [May 14, 1948], No. 11878/49. .Class 80 (ii) [Also in Group XXX] A speed controlling device for use with a conveyer drive unit of the type which incorporates means for varying the speed of its output member and means for sensing the tractive effort between the conveyer - drive unit and the conveyer member propelled thereby which device includes an output member and mechanism for varying the speed of the conveyer drive unit in response to movement of this output member, comprises mechanism for producing movement of this output member in response to the application of motive power from an external source and/ or a change in the tractive effort between the conveyer drive unit and conveyer propelled thereby. The endless chain 9 is driven by motors 16 through a transmission 17 .and reduction gearing 18. Two driving units, a master and follower are at spaced intervals on a, supporting frame 10 which rests on rollers 11 on a fixed frame 12, the movement between the two frames being limited by a spring 13 joining the two. The speed control unit comprises a gear box, a motor 25 and a shaft 22 to which is secured a gear 29 and a gear 28 which meshes with a gear 26 driven from the gear head 27. A gear 40 is mounted to rotate with a sleeve 38 loose on the shaft 22. A planetary arm 37 is secured to the sleeve 38 and is secured to a stub shaft 36 supporting on bushes gears 30, 31 which mesh with gears 29, 32. The gear 32 and a gear 41 are mounted to rotate with a sleeve loose on the main shaft. The gear 41 transmits the drive to a speed adjusting screw 19 by means of a chain 55 which passes round the sprocket 41 and sprocket 56 mounted on the screw 19 of the transmission 17. When the frame 10 moves with respect to the frame 12, the gear 40 rotates through a chain 46 which passes over idler sprockets 44, 45 and under sprocket 40. One end of the chain is secured to a bracket 48, connected to the frame 12 and the other end is resiliently mounted by bracket 49. Rotation of the gear 40 rotates the planetary arm 37 and through the gearing rotates sprocket 41. The motor 25 drives the shaft 22, the planetary arm remains stationary and the gear 29 effects rotation of the sprocket 41 for an overall speed change. An electric circuit controls the speed change and speed control operation by using a potentiometer 68 which records changes in positions of the frames and a tachometer on the output shaft 66. A potentiometer 61 shows the relative position of the frames by the amount of rotation of the shaft 22. The potentiometers 68M, 68F, tachometers 65M, 65F are in circuit with a transformer 73 and two thyratrons 74, 75; any changes in the circuit operate the motors 25M, 25F. A time delay relay 76 with contact 77 is connected to a 115 volt line 70. Contacts 81, 82 are closed by motors 16. Push buttons 86, 87 manually control the motor 25M through relay 88 controlling motor contacts 89, 90 and relay 92 controlling motor contacts 93, 94. Relays 95, 96 actuated by the thyratrons operate contacts 97, 98 and 100, 101 of motor 25F. The thyratrons are controlled by the tachometers and potentiometers. A rectifier tube 104 connected to the secondary of transformer 73 provides power through a bleeding resistor 108 subdivided for connection with an amplifier tube 105 and with potentiometers 68M, 68F. The tachometers 65M, 65F are connected with the potentiometer 68M and to the amplifier tube 105 so that a difference in potential between the two affects the potential of the line 110. The potentiometer 68F is also connected to the amplifier tube. With the control circuit in balance, the potential at point 117 is zero, when the balance is disturbed current flows through a thyratron. A negative voltage is applied to the grids of the thyratrons through a rectifier 121 in circuit with the secondary of transformer 73, this is opposed by the unbalanced condition which if great enough for the thyratron closing the relay and actuating the motor 25F. The control circuit is operated only when changing the overall speed of the systems. Switch 71 is closed, push button 86 or 87 is operated to bring the motor 25M to the required speed. The tachometers 65M, 65F will vary operating the thyratrons to control the motor 25F. When the circuit has returned to the inbalance, condition meter 128 is zero and the switch 71 may be opened. The same control circuit may be used if the position of the screw 19 is used as a reference factor, the potentiometers 61M, 61F being substituted for potentiometers 68M, 68F and tachometers 65M, 65F can be eliminated. If potentiometers 68M, 68F are used as the reference factor the tachometers can be eliminated or the potentiometers can be dispensed with and the tachometers used as the reference factor.