GB1131521A - Improvements in and relating to machine tools such as grinding machines - Google Patents

Abstract

1,131,521. Grinding. LANDIS TOOL CO. 18 Jan., 1966 [21 Jan., 1965], No. 2213/66. Heading B3D. A machine tool comprises a work rest 10 for supporting a workpiece against a cutting tool 15 and having a plunger 25, a work rest shoe 26 on the plunger, and means for applying a force to the plunger to urge the shoe against the workpiece. As described, the machine tool is a grinder for the crank-pins W of a crank-shaft which is axially and angularly indexed for the grinding of the successive crank-pins, and the work rest shoe is urged against a crank-pin with a relatively low pressure after angular indexing to effect a precision location of the crank - pin and is then urged with a relatively high pressure against the crank-pin during the grinding operation. The work rest 10 is movable about a pivot 11 on the machine frame by a piston-and-cylinder device 20, 21 and has a lower supporting member 30 movable about a pivot 31 on the rest by an actuator 32 to support the crank-pin W from below during a grinding operation. The plunger 25 having the work rest shoe 26 is movable in the work rest against the force of a spring 27 by means of a cam 35 movable in opposite directions by fluid pressure supplied to opposite ends of a cylinder 38 urging pistons 37, 40 against the ends of the cam. The plunger is also movable against the spring by fluid pressure supplied to the space 28 between the pistons and acting directly on the plunger. In operation and following angular indexing of the crank-shaft, the frame 10 is moved to its operative position by piston 20 and a limit switch activates a relay and timer so that a solenoid 3 moves a valve 60 to supply fluid pressure from a pump and a pressure reducing valve 62 at a relatively low value to the space 28 whereby plunger 25 moves against the force of spring 27 to press shoe 26 against the crank-pin with sufficient force to rotate the crank-shaft if necessary and ensure that a locating pin 52 on the index plate of the machine is urged against one side of a hole 50 or notch in the flange 51 of the crank-shaft. When the timer relay times out, the solenoid 3 is de-energized and spring 27 retracts the plunger. After a predetermined grinding operation, a solenoid 12 is energized moving a valve 65 so that high pressure fluid from the pump causes piston 37 to move cam 35 downwardly so that the work rest shoe 26 on plunger 25 is urged with greater force than before against the crank-pin during the grinding operation. On completion of the grinding operation, solenoid 12 is de-energized and the valve 65 is moved by its spring to supply fluid pressure to the piston 40 moving cam 35 upwardly so that spring 27 can retract plunger 25.