Patent GB-973381-A (GB)
Title: Apparatus for machining a work piece
IPC: B24B49/00
Filed: 1962-12-18
Abstract: 973,381. Grinding. NORTON CO. Dec. 18, 1962 [Dec. 18, 19611, No. 47675/62. Heading B3D. A machine having a wheel 22 for grinding the opposed spaced surfaces ws of a workpiece w comprises a cam 98 which has symmetricallydisposed lobes and is supported for pivotal movement about a first axis 96 to engage the lobes with the surfaces ws, drive means 62 to axially move the workpiece and displace the cam about a second axis 78, and control means 8LS actuated by the movement of the cam about the second axis to a predetermined position to de-activate the drive means so that the workpiece is disposed with its surfaces ws in a predetermined position relative to the grinding wheel. The cam 98 is mounted on the shaft 96 of a pinion 100 rotatable in a probe head 74 by a rack on a piston 104 slidable in a cylinder 1B in the head. The probe head is pivoted at 78 to a slide 84 movable towards and from the workpiece by a piston-and-cylinder device 1 The slide actuates a limit switch 9LS in its rearmost position and an arm 76 of the probe head actuates the control means which is in the form of a switch 8LS having contacts 8LSa and 8LSb, one or other of which are closed depending upon the position of the arm; a lost-motion connection joins the arm to the switch and a spring 94 urges the arm to a position closing contacts 8LSa. The workpiece w is supported between head and foot stocks 14, 16 mounted on a slide 12 movable on a base 10 having slides 32, 34 for movement of the grinding wheel to and from the workpiece. The foot stock centre 36 is urged by a spring 40 into engagement with the workpiece which is thereby urged against the headstock centre 38. The centre 38 is axially slidable in a sleeve 54 by a screw 62 axially fixed but rotatable by a pinion 60 engaged by a rack 58 formed on a piston 56 slidable in a cylinder 2A, fluid pressure being supplied to the cylinders 1A, 1B, 2A under the control of solenoid-operated valves from a pump P. The workpiece is rotated during grinding by a dog on a chuck 68 driven by belts from a belt-driven shaft 20. Actuation of a start switch SW1 energizes a time-delay relay ITR which supplies current to the normally-open contacts of a limit switch 7LS and to a second time-delay relay 2TR, the contacts of which energize a relay 7CR to actuate a solenoid S4 of a valve V4. Movement of the valve permits fluid pressure to act in cylinder 1B and advance slide 86 to position the cam 98 between the surfaces ws and actuate limit switch 7LS to energize a relay 8CR controlling the solenoid S5 of a valve V5 which causes fluid to act in cylinder lA so that the cam is rotated to bring its lobes into contact with the surfaces ws. Current is supplied through the contacts of relay 2TR and contacts 8LSa to the solenoid S7 of the valve V7 and through the contacts of a relay 9CR to the solenoid S6 of a valve V6 so that fluid pressure is supplied to the upper end of cylinder 2A to rotate screw 62 and advance the headstock 38 and workpiece against the spring 40 at a rate determined by a throttle 124, the cam 98 and arm 76 moving about the pivot 78. When the work has reached a predetermined position relative to the grinding wheel, the arm 76 opens contacts 8LSa and closes contacts 8LSb to de-energize the solenoid of valve V7 to block exhaust flow from the cylinder 2A and lock the workpiece against further axial movement. The closing of contacts 8LSb also re-energizes the time delay relay 2TR which thereafter causes solenoid S5 to be de-energized so that the valve V5 connects cylinder 1A to exhaust, a spring 108 rotating cam 98 to move its lobes from contact with the surfaces ws, and also deenergizes the solenoid S4 of valve V4 which causes fluid pressure to be supplied to the opposite end of cylinder 1B so that the slide 84 is retracted opening limit switch 7LS and closing limit switch 9LS to initiate advance of the grinding wheel as described in U.S.A. Specification 2,522,485. After retraction of the grinding wheel, a switch 2LS resets the time-delay relay 2TR for the next operation and de-energizes solenoid S6 so that valve V6 shifts to permit fluid to enter the lower end of cylinder 2A to return the headstock centre to its initial position. The footstock centre 36 is retractable by a handle 50 to permit replacement of the workpiece and actuates a limit switch 4LS to reset the time-delay relay 1TR. U.S.A. Specifications 2,2.64,160, 2,313,482, 2,693,061, 2,723,504 and 2,955,391 also are referred to.