Patent GB-1171809-A (GB)
Title: Apparatus for Cutting Helical Grooves.
Inventor: AMELCHENKO ALEXEI SEMENOVICH
IPC: B24B19/02
Filed: 1967-10-26
Abstract: 1,171,809. Grinding. LENINGRADSKOE PROIZVODSTVENNOE OBIEDINENIE " RADIODETAL." 26 Oct., 1967, No. 48757/67. Heading B3D. Apparatus for cutting a groove in a workpiece, such as a metallized resistor to determine its resistance, comprises means 35, 36 for holding a workpiece a, means for rotating the workpiece, a cutting tool 37 reciprocable relative to the workpiece while in contact therewith to cut a helical groove in the workpiece, the tool being carried by a head 38 coupled to a lever 41 arranged to oscillate about a fulcrum 44 by means of a rotating cam 40 to reciprocate the head, the profile of the cam having two portions which are mirror images of each other, one portion controlling the movement of the tool in one direction and the other portion controlling the movement of the tool in the opposite direction, means 52, 54 for varying in discrete steps the speed of rotation of the workpiece to adjust the pitch of the helical groove to a selected discrete value, and means for steplessly varying the ratio of the lever arm 41<SP>1</SP> between the fulcrum 44 and the head to the lever arm 41<SP>11</SP> between the fulcrum and the cam to steplessly adjust the pitch between the limits of adjacent discrete values. The workpiece a is supplied to the holding means consisting of driving and driven collets 35, 36 from a loading mechanism 28, the collet 35 being driven from a motor 1, belts 2, and gears 49 . . . 54. Gear 52 is movable along gear 54 to adjust the rotation of the workpiece by the discrete steps. Gear 54 is on a shaft 3 coupled to a shaft 5 which is connected by worm gearing 6 . . . 9 to shafts 10. . . 13. Shaft 10 drives a series of cams 14. . . 19 controlling the operation of the machine and an instrument 26 for measuring the resistance of the workpiece, during grinding so as to terminate grinding when the workpiece has a desired resistance, and a cam 27 controlling the loading mechanism 28. Shafts 11 and 13 drive cams 29, 30 co-operating with levers 31, 32 for moving the collets to engage and eject the workpieces. Shaft 12 drives the cam 40 which moves lever 41 about fulcrum 44 to reciprocate the head 38 carrying the cutting tool such as a grinding wheel. The lever moves the head against the pressure of a spring 42 during movement of the head in one direction for grinding a workpiece, and after ejection and replacement by a new workpiece, the spring returns the head under control of the lever and cam in the opposite direction for grinding the new workpiece, the cam having portions which are the mirror image of one another. The fulcrum 44 is adjustable by a hand wheel 45 to vary the pitch of the grooving formed on the workpiece between the adjacent discrete values determined by the gearing 52, 54. The grinding wheel 37 is carried by a section 57 mounted on shaft carried by a section 56 fixed to the head 38. A spring 58 presses the sections together to a position determined by a screw 59 which is adjustable to move the grinding wheel to compensate for wear thereof. A spring 60 adjustable by a screw 62 presses the grinding wheel against the workpiece and the feed of the grinding wheel into the workpiece is controlled by a roller 63 engaging a follower 64. In another embodiment, the collets move the workpiece into engagement with the grinding wheel.