GB1140242A - Improvements in or relating to control equipment - Google Patents

Abstract

1,140,242. Grinding. WILMOT-BREEDEN Ltd. 22 Aug., 1966 [22 May, 1965], No.37413/66 Heading B3D. A control means for selectively controlling the pressure between a polishing head 8 and a contoured object 7 in accordance with the surface zone thereof to be polished comprises position responsive means 27, . . . 32 which produces an electrical position signal as the head transverses each boundary between adjacent zones, a sequence control circuit to which the succession of position signals are fed and which delivers output signals in sequence as each position signal is received, and a pressure controlling device which acts to control the pressure selectively in accordance with the prevailing output signal. As described, the control means is applied to a machine which may have several polishing heads 2a.... 2d, for polishing bumper bars, each bar 7 being mounted on a jig 6 movable along a continuous track 4 to present the bars to the polishing heads. Each head consists of an abrasive belt 10 running over a pulley 11, a drive wheel, and a laminated felt jockey wheel 12 which is raised and lowered by a pneumatic double acting cylinder 17 under the control of its associated control means. The polishing heads are identical but may be of different grades and angled by various amounts for polishing different regions of the bumpers. Each control means consists of a plurality of detectors 27, ... 32 comprising yokes having spaced arms 34, 35, Fig. 4, arm 34 having an aperture for a reed switch 36, and arm 35 having a magnet 37 which normally maintains switch 36 closed. The detectors are positioned along the track at the boundaries of zones of the bars, and are actuated in sequence by a magnetic shield 38 fixed to each jig 6 and arranged to pass between the arms of the detectors so that the switches are opened in sequence. The switches are connected to a sequence control circuit consisting of " and " and " latch " stages as described in Specification 1,140,241, the output of which is connected to a pneumatic circuit having a plurality of solenoid operated valves and pressure regulators to control the associated pneumatic cylinder 17 so that the abrasion belt is engaged with the bumper at the predetermined pressure required to polish each zone. In an alternative embodiment, a single detector 80, Fig. 6, which is actuated by a magnetic shield 83 fixed to conveyer 82 and is provided with a shaft encoder driven from the conveyer, the encoder producing pulses proportional to the speed of the conveyer which are fed to a circuit having a ring counter and selector switches for producing the position signals for feeding to the sequence and control circuit controlling the associated polishing head.