Patent GB-666126-A (GB)
Title: Improvements in or relating to centreless grinding machines
IPC: B24B5/18
Filed: 1947-12-31
Abstract: 666,126. Centreless grinding. HATEBUR, F. B. Dec. 31, 1947 [March 3, 1944], No. 35227/47. Class 60. A centreless grinding machine in which the workpiece, when introduced to the grinding throat, is movable against the grinding wheel by means of a control wheel by which it is frictionally rotated during grinding is characterised in that driving means is provided for positively rotating the workpiece during its insertion longitudinally into the grinding throat, said driving means being rendered inoperative when the work is engaged by the control wheel. In one embodiment, Figs. 1, 4 and 5, a headstock 1 is adjustably secured to the work rest holder 3 which is adjustable relatively to the slide carrying the control wheel 2. Slidable on the headstock 1 in a direction parallel with the axis of the control wheel 2 and of the grinding wheel 5 is a spindle carrier 4 on which is mounted a hollow spindle 6 driven through worm gearing 7, 8, by a motor 9 secured to the carrier 4. The carrier 4 has a rack 10 meshing with a gear segment 11 on a shaft 12 journalled in the headstock 1 and having a handlever 13; the gear segment 11 is centralised by a spring 14. Slidably mounted within the spindle 6, which is formed at its forward end with a conical surface 15, is a sleeve 16 the forward end of which carries collet or chuck jaws 17 for holding a workpiece 18. In the inoperative normal position, the rear end of sleeve 16 projects beyond the spindle housing 19, and screwed into this end of the sleeve 16 is a bar 20 having a head which slides within a hollow sleeve 21 which also receives a screwthreaded rod 22 adjustably mounted in an arm 23 carried by the headstock 1. Sleeve 16 is urged by spring 24 towards one arm of a lever 25, pivotally supported by carrier 4, the other arm engaging a knife edge 26 on a rod 27 passing through a hole in the arm 23 and carrying adjustable nuts 28. An ejector 29 operated by a spring 30 is mounted within the sleeve 16. The headstock 1 carries fixed contacts 34 co-operating with a movable contact 35 actuated by a control surface 36 secured to the spindle carrier 4, the contacts controlling the spindle motor 9 and the slide on which the control wheel 2 is mounted. In operation, the spindle 6 is initially in retracted position with a workpiece 18 gripped by the jaws 17; by operating the handle 13 the spindle 6 is moved forward to a position wherein the workpiece 18 is supported on the work rest with the work in contact with the control wheel, the rod 27 pulling the lever 25 back so that the upper arm moves sleeve 16 forwardly to open the jaws 17 so that the workpiece is no longer rotated by the spindle 16. During the advance of the spindle 16 the contacts 34 are closed to start the spindle motor 9 and to advance the slide carrying the control wheel to carry the workpiece into contact with the grinding wheel. The carrier 4 is in two parts, the part 4a having the spindle housing 19 being connected to the slide part 4 by inclined guides 31, 32 and spring mounting 33. During grinding the axis of the workpiece 18 is displaced in an inclined direction corresponding to the inclined top surface of the work rest, this displacement being permitted by the inclined guides 31, 32, the rods 20, 27 being adapted in any suitable way to allow of the displacement. On completion of grinding, the handle 13 is operated to retract the carrier 4; the rod 27 and hence lever 25 are thereby released whereby sleeve 16 is returned by spring 24 to its original position and jaws 17 again grip the workpiece; during retraction the contacts 34 are actuated so that the control wheel 2 is withdrawn by a set amount and the spindle motor 9 is switched off. In the extreme rearward position of the spindle 6 rod 20 abuts the forward end of screw 22 so that sleeve 16 is pushed forward and jaws 17 opened; the spring 30 operates the ejector 29 to eject the workpiece. In a modification, the workpiece is gripped internally by a split chuck. In a modification for grinding tapered workpieces, the headstock 1 is connected by a vertical hinge 1b, Fig. 12c, to a plate 1a connected by a horizontal hinge 3c, Fig. 12b, to a member 3b fixed to the work rest holder 3; set screws 1c, 1d are provided for giving the desired settings. The control wheel 2 has a tapered periphery. In a modification, Fig. 13, the workpiece is driven from the control wheel drive, instead of by a separate motor. The work spindle has at its front end a slot to receive a coupling dog 48 mounted on a spindle 49 driven, through universal joints 46, from the control wheel drive; spring 50 presses the coupling dog into the slot. In a modification for cylindrical and end face grinding, the work 42, Fig. 16, is mounted on a chuck 41 provided with a stop ring 43 for correctly positioning the work; the stop ring may be a sleeve. In a modification, the work rest 3a, Fig. 15, has a flat supporting surface and the control wheel 2 is elevated relatively to the grinding wheel 5. In modifications, Figs. 21 and 23, for grinding relatively long workpieces, the workpiece is supported by opposed control wheels 2, 3. A control mechanism, Fig. 26, comprises a stop 54 on the control wheel slide co-operating with the tongue 56a of a rod 56 connected to a lever 57 pivoted to the frame at 57a, the lever having a forked end to engage a pin 57b projecting from a piston rod 60, the piston 60a of which moves in a cylinder 61. Pressure oil can leave the cylinder 61 through an adjustable needle valve 63. A micrometer screw 59 on an extension of the piston rod actuates a contact 65 controlling atime relay 55.