Patent GB-869225-A (GB)
Title: Improvements in and relating to electrical control systems for winders and other conveyances moving in predetermined paths
Inventor: LOWTHER ROY
IPC: B66B1/46
Filed: 1956-08-13
Abstract: 869,225. Electric programme control systems. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Aug. 7, 1957 [Aug. 13, 1956], No. 24704/56. Class 38 (6). [Also in Group XXXV] In a control system for a conveyance which is guided to move along a predetermined path, magnetic signals designed to control in a predetermined manner, or limit, the motion of the conveyance are impressed on a magnetic element which comprises part of the hauling, hoisting or guiding equipment and extends along the path, or is movable to extend along the path during motion, and pick-up means responsive during motion to the signal, or the motion and the signal, is or are arranged to control the motion or position of the conveyance. In a Koepe pulley-driven mine winder, Fig. 1, magnetic signals the wavelength of which are indicative of the desired speed are impressed on the cage cables RC1, RC2 by a 1 kc/s. oscillator during an ideal manually-controlled run and the signals picked up in reproducing heads SHF, SHR during subsequent forward or reverse operation respectively are applied to energize the control coil CA of an amplidyne or magnetic amplifier through an amplifier A and a discriminator which includes tuned circuits LC1, LC2 tuned respectively above and below 1 kc/s. The amplidyne output is applied to control the field GF of a Ward-Leonard set MA, GA. A switch SW is provided which may be changed over to energize the field from a fixed D.C. supply during signal recording, the desirable conveyance speed being obtained by a resistor VR. The signal may be amplitude modulated and alternatively the discriminator output can be used to control the rotor resistance and thus the torque of a D.C. motor in respect of driving or dynamic braking. In a loop control system described with reference to Figs. 3 and 4 the output of a tachometer generator TG which is compared with a direct voltage applied at terminals D1, D2 in a control coil CA is modified by a resistor R2 steps of which are put in or taken out by contactors OC1-4 to effect acceleration or retardation respectively in response to gaps in signals picked up by the heads SHF, SHR, which cause the stepping of a selector switch SS. The relays may alternatively be actuated by discrete changes in level in the impressed signal. Fall-safe arrangements are provided by a timing switch OCMT and a stop switch OCST. The element may carry two separate complete journey signals in which different heads or other discriminating means are selected by the forward or reverse contactors, or may carry retardation signals only, the pick-up being disconnected during acceleration by a cam arrangement. If two elements are used, one may be arranged to carry both acceleration signals and the other both retardation signals. In some instances a single signal may serve to produce the desired control in both directions. The signal of the embodiment described with reference to Fig. 1 may be applied during a slow constant speed run from a variable frequency source which may be obtained from a factory recorded magnetic tape. The signal output in further alternative embodiments may be proportional to speed. The control system may only provide an override to manual control.