GB1190101A - Grinding Machine Control Mechanism - Google Patents

Abstract

1,190,101. Grinding. COVENTRY GAUGE & TOOL CO. Ltd. 19 May, 1967 [23 Feb., 1966], No. 7871/66. Heading B3D. Grinding wheel feed control mechanism is characterized by cam means having a stepped profile and operable in timed relationship with the movement of a workpiece relative to the grinding wheel during grinding of the workpiece, said cam means being arranged to actuate a follower in turn arranged to actuate screw means for causing incremental feed of the grinding wheel to the workpiece as the grinding operation progresses. A workpiece 3, e.g. a gear, a series of gears or a splined shaft, is mounted between the centres of a head stock 4 and a tailstock 5 mounted on a slide 6 reciprocated on the machine bed 7; the head stock 4 carries means for angularly indexing the workpiece. A grinding wheel 1 is carried by a wheel head 2 engaged by a lead screw 14. For setting up, a worm 9 operated by a hand wheel drives the lead screw 14 through a worm wheel 10, a magnetic clutch 11, a shaft 12 and a gear train 13. The lead screw 14 is mounted by thrust bearings 17c in the screw 17a of a screw mechanism of the recirculating ball type, the nut 17b being fixed. For automatic feed a cam 16, which is preferably rotary but may be linear, rotated or indexed e.g. by an hydraulic rotary actuator operating in timed relationship with the reciprocation of the workpiece 3 has a stepped profile 16a engaging a follower 19 linked at 20 to the screw 17a. A disc 21 driven with the cam 16 carries pegs 22, 23, 24 selectively mounted in series 22a, 23a, 24a of holes. The pegs 22 successively operate a switch 25 usually for each step of the cam profile or selected range thereof for correlating the movement of the cam with the reciprocation of the workpiece 3. One or more pegs 23 operate a switch to control the dressing or dressings of the wheel 1 during a grinding cycle. A trip peg 24 operates a switch so that the required extent of the stepped profile of the cam can be selected according to the grinding cycle required, on completion of which the slide 6 moves to an unloading/reloading position clear of the wheel head 2. When a peg 23 operates its switch the slide 6 is moved to bring a dressing device into operative position relative to the grinding wheel. Simultaneously, the follower 19 is withdrawn, by an hydraulic ram 29, from the cam and brought against a datum stop 30 corresponding to the finished size of the workpiece 3. For setting the grinding wheel 1 for pressing an hydraulic ram 31 operates a pick feed mechanism 15 comprising a ratchet wheel 32 on the shaft 12 actuated by a pawl 33 carried by an arm 34 the movement of which is determined by an adjustable stepped stop 35. On completion of dressing, the hydrualic ram 29 is operated to return, or permit spring-loaded return, of the follower 19 into contact with the cam. Preferably the cam 16 effects feed for all the stages of the programmed stock removal from the workpiece except the last stage which is performed with the follower 19 against the stop 30. Preferably the wheel 1 is dressed for the penultimate pass of the workpiece. The workpiece 3 may be indexed so that each flute is passed in relation to the wheel before the latter is fed. Alternatively each flute may be finished almost to size by a number of passes before proceeding to the next flute. The disc 21 may serve as a code disc cooperating with a reader of code means, e.g. consisting of a peg board and comparator in which a desired code is set on the peg board and comparison thereof with the disc effected by the comparator for controlling rotation of the disc and cam. The code disc may co-operate with contact members of the reader or the latter may consist of a photo-electric cell arrangement co-operating with holes in the disc and a light source.