GB1093624A - Improvements in or relating to grinding machines - Google Patents

Abstract

1,093,624. Grinding. LUKE & SPENCER Ltd. Dec. 10, 1965 [Feb. 11, 1965], No. 5886/65. Heading B3D. A grinding machine includes a grinding wheel, means actuable to drive the grinding wheel at a variable speed of rotation and means including a sensing wave beam to sense the diameter of the grinding wheel and to control the grinding wheel driving means in such a way that the speed of the grinding wheel is inversely proportional to the diameter of the grinding wheel, so maintaining the peripheral speed constant. A grinding wheel 11 is driven by a motor 19 through pulley 20, belt 21 and divided pulley 13, 14. The axial spacing of the pulley parts 13, 14 is varied by a shaft 15 driven by a chain 23 and connected through gearing 16, 17 to a screw 18 for moving the motor 19 to maintain the belt 21 taut. A slide 30 is movable towards and away from the grinding wheel 11 by a screw 26 driven through a chain 27 by a motor 29. In the slide 30 are sensors mounted in sound insulating blocks 31 carrying sonic probes 32 comprising nylon tubes terminating in opposed nozzles. The probes act as sound guides for an ultrasonic sound beam generated between the sensors. The probes may be enclosed in steel tubes. The beam is normally interrupted by the grinding wheel. When the grinding wheel wears the beam is uninterrupted and the motor 29 is energized to advance the slide 30 until the beam is again interrupted; simultaneously with the advance, the pulley 13, 14 is opened so as to increase the rotational speed of the grinding wheel and the motor 19 is adjusted to maintain the driving belt taut. When the grinding wheel reaches its discarding diameter trip mechanism 35 operates a reversing switch 36 energizing the motor 29 to retract the slide to a position allowing for the mounting of a new grinding wheel. At this position the trip mechanism 35 makes ready the advance movement of the slide 30 but no movement ensues because the beam is interrupted by a baffle plate 37 mounted on the wheel guard. When the new wheel has been fitted, the baffle plate 37 is moved so that the beam is uninterrupted and the slide 30 advances until the probes register with the wheel. If, due to a fault in the control circuit, the slide 30 advances while the beam is interrupted by the grinding wheel, a wire 38 is cut by the grinding wheel and a switch 39 snaps open to break the circuit to the motor 29, so preventing further motion.