GB1098176A - Improvements in control means for conveyor means - Google Patents

Abstract

1,098,176. Automatic control of conveyers. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Sept. 25, 1964 [Oct. 10, 1963], No. 40006/63. Heading G3R. A signal dependent on deviation of the loading of material on part of a conveyer from a datum value is multiplied by a signal dependent on conveyer speed, and the product utilized together with a rate component to control the supply of material to the conveyer. In Fig. 2, the belt 1 of a main conveyer for particulate material bears on a pivoted lever 17 influenced by a balance weight 19 and a centring spring 23. Variations in conveyer load cause, through a rack and pinion 27, rotation of an arm 41 to move a pick-up coil 43 relative to a fixed pick-up coil 45. A disc 35, carrying a permanent magnet 39 influencing coils 43 and 45 and peripheral teeth 37 influencing a further pick-up coil 51, is rotated by a selsyn system (not shown) in synchronism with a tachometer generator-controlled electric motor (not shown) driving the conveyer. The position of coil 43 relative to coil 45 corresponds in magnitude and sense to the deviation in conveyer load from a desired value chosen by weight 19. A gate 55 is opened during the passage of magnet 39 between coils 43 and 45 so that a number of pulses from coil 51, corresponding to the load error, is passed to cold cathode counters 57. The number of sets of these pulses in a given counting period is dependent on the speed of disc 35, and hence conveyer speed, so that an output from counters 57, corresponding to the load error multiplied by the conveyer speed to give a suitable gain, is obtained periodically and applied to an analogue to digital converter 59 which controls the speed of an electric motor driving an auxiliary conveyer (not shown) feeding the main conveyer or the depth of material on the auxiliary conveyer to correct the main conveyer load. Each output from counter 57 is compared with the previous output stored in a device 61 which derives the difference and thus adds a rate of change component to the control system. The electric motors driving the conveyers are supplied and controlled through silicon controlled rectifiers.