Patent GB-1449734-A (GB)
Title: Apparatus for grinding workpieces
IPC: B24B5/02
Filed: 1974-03-11
Abstract: 1449734 Grinding OLIN ENERGY SYSTEMS Ltd 10 March 1975 [11 March 1974] 10804/74 Heading B3D [Also in Division B8] A method of grinding workpieces, such as alumina spark plug insulators formed by isostatic pressing, comprises loading blank workpieces 20 on to respective ones of a plurality of mandrels 18 provided on a rotatable member 6, the mandrels being parallel to and equi-spaced from the axis of rotation 6a of the member, rotating the blanks on the mandrels, rotating a profiled grinding wheel 9, effecting rotary indexing of the members such that each of the blanks thereon successively moves relatively rapidly from a position spaced from the grinding wheel to a position immediately adjacent the wheel, moves relatively slowly from said immediately adjacent position into the path of the grinding wheel to a position of maximum intersection with the wheel and stops at such position for a grinding operation to be completed, and moves rapidly away from the position of maximum intersection, and ejecting the ground workpieces from the rotary member. The workpieces are initially formed in an isostatic pressing apparatus having a head 3 which moulds six alumina spark plug blanks that are delivered to a conveyer 5 having cups 4 for delivering the blanks to the rotary member 6 to the grinding apparatus 1 which has a loading mechanism 7, a drive wheel 8, a grinding wheel 9, and a mechanism 10 for ejecting ground workpieces on to a discharge conveyer 11. The member 6 has ten heads each of which has a mandrel 18 held in a chuck 19. The blanks 20 are supported in the cups 4 of the conveyer by a cover 22, the conveyer being advanced in steps by a Geneva Mechanism, until they reach a position A at which a plunger 23 is axially moved to load a blank on to a mandrel 18 of the member 6, the plunger being secured to a rod 25 connected to one arm 26 of a bell crank lever movable about a pivot 27 by a roller 28 on the other arm engaging a cam track 29 in a cam secured to the output shaft 30 of a gear-box 16 driven by a variable speed electric motor 17. During one rotation of the shaft 30, the member 6 is indexed 36 degrees, the movement is initially effected at a relatively high speed to move a blank from a position B and then decelerated to a position of about 26 degrees of the movement, the blank at about 20 degrees of movement engaging the drive wheel 8 so as to be rapidly rotated as the blank engages the grinding wheel, the remaining indexing movement being at a constant velocity until the blank is in position C where it remains for a dwell period. The blank is then rapidly moved from position C and a ground blank at a position D is ejected by the mechanism 10 having a member 42 formed with a slot 43 which is engaged by the mandrel 18. The member 42 is secured to a rod 44 slidable by the action of a bell crank 45 also movable about the pivot 27 by the roller 28 engaging the cam track 29. The drive wheel 8 is mounted on a shaft rotatable by a belt drive from a shaft located above the rotary member 6. The axes of the drive wheel 8 and member 6 are slightly angled so as to cause the blank being driven to be used axially against a shoulder on its spindle. While the blank is being rotated during the grinding operation, a tip-cutting tool 34 may be advanced by a spring and under the control of a cam 39 to engage the tip of the blank to convert a blind bore in which the mandrel is engaged into a through bore and forms a chamfer thereon. If the spacing of the cups 4 of the conveyer differs from the pitch of the mould hands of the press 2, the blanks may be delivered by shoots to inverted cups 64a... 64f fixed by rods to the pistons of cylinders 69 which when actuated move the cups so that the blanks can fall through openings 70a... 70f in a plate 65 into the cups 4 of the conveyer 5.