GB844048A - Improvements in grinding machines - Google Patents

Abstract

844,048. Grinding. EDQUIST, F. E. April 7, 1959, No. 11703/59. Class 60. The wheel 4 of a grinding machine is movable towards and away from the work 1 by a pneumatic double-acting piston and cylinder 7, 8, a substantially constant pressure being maintained in a chamber 8a on one side of the piston while the chamber 8b on the other side of the piston is connected to an air tank 18 of considerable volume and is of adjustable pressure, for maintaining the required pressure between the wheel and work, by a variablereducing valve 14 located in compressed air supply lines 9, 13a, 13b ; a two-way valve 15 being inserted in the line 13b and operable by an air link 23 from a control valve 21 is arranged to open to exhaust the chamber 8b through an outlet 15a of the valve 15. A valve 17 connected between the chamber 8b and tank 18 is also operable by the control valve 21 so that the connection between the tank and cylinder is interrupted as the valve 15 opens the chamber 8b to exhaust. The workpiece 1 is clamped to a table 2 which is displaceable along a track in a plane parallel with the axis of the motor-driven grinding wheel 4. In addition to movement of the wheel about the pivotal point 5 of a lever 6, it may be displaced transversely of the work in a known manner. When the control valve 21, which may be operated by a pedal 21a, is open the valves 14, 15, 17 will be held open to admit compressed air to the cylinder chamber 8b and to the tank 18 ; the pressure in the cylinder chambers may be checked by gauges 25 and 26 and adjusted by reducing valves 11 and 20 to provide the desired pressure of the wheel on the workpiece. A spring-loaded relief valve 27 vents excess pressure from the chamber 8a. Because of the relatively large volume of the air tank 18 pressure variations in the chamber 8b will normally be small but if, due to irregularities in the surface of the workpiece, the piston 7 is moved upward to an extent that the pressure above the piston tends to increase, the reducing valve 14 is so adjusted that it will open under excess pressure and discharge through an outlet 14b, thus permitting the wheel to follow surface irregularities whilst under constant grinding pressure. When the control valve 21 is closed, valves 14, 15 and 17 will close and the chamber 8b is vented through the outlet 15a of the valve 15 so that the piston will be raised by the excess pressure in chamber 8a until a cam 28 at the end of the lever 6 remote from the grinding wheel closes a valve 12 in the air supply line to the chamber 8a. A similar automatic cut-off is operable by a vertically-adjustable cam 32 at the other end of the lever 6 when the wheel moves below a predetermined level.