Patent GB-1403948-A (GB)
Title: Apparatus for grinding stepped workpieces
IPC: B24B51/00
Filed: 1973-05-25
Abstract: 1403948 Grinding; honing grinding wheels N M A LASSERRE 25 May 1973 [1 June 1972 4 Jan 1973] 25306/73 Heading B3D  Apparatus for grinding a stepped workpiece comprises a translatable table T for carrying a workpiece and a member P for carrying a grinding wheel M being relatively movable in two orthogonal directions, a device for removing a worn surface from the grinding wheel, and mechanical and electrical means to control movement and actuation of the table, member and device in accordance with a predetermined cycle to grind a workpiece having stepped cylindrical surfaces. The member P carrying the grinding wheel is in the form of a slide secured to the cylinder of a jack 1 having a piston 2, the rod 3 of which is connected by a coupling 4 to a screw-threaded member 5. The end of member 5 is rotatable in a bearing 6 and connected by gears 11, ... 15 to a stepping motor 12. The threaded part of the screw engages a block 9 which has two prestressed nuts to prevent backlash and is secured to the slide P, the block being slidable along the non- threaded part of the member 5. The table T is displaceable by a piston 17 in a cylinder 16 to which hydraulic pressure is supplied through valves 19, ... 22 controlled by a manipulator 23 having five positions. In position D, valve 22 is closed and the other valves open so that the table can be adjusted manually. In position D, valve 22 is open and valves 20, 21 and 19 are controlled by proximity detectors so that the fluid first flows in direction f and then in direction f 1 . The table can be locked with the manipulator in position B, and in positions A and C the table is moved in stages. At each reversal, the motor M causes a predetermined movement of the grinding wheel. To eliminate uneven wear of the grinding wheel, a trueing device is provided having a diamond 24, Fig. 6, carried by the rod of a jack 25 movable along a slide 26 by a stepping motor 27. Alternatively, the diamond 39, Fig. 10, is mounted on a support 40 carried by an hydraulic jack 38 for rapid advance of the diamond, the jack being fast with a block 41 advanced at a slow rate by a screw 42 driven by a stepping motor 43. In the automatic operation of grinding a number of steps on a cylindrical workpiece, the programme is displayed on an electronic display panel and the slide P is initially held in a retracted position. A pulse actuates the valves so that the hydraulic pressure causes the slide to advance at 20 mm./sec. until the piston 2 abuts a stop 1a and the wheel is almost contacting the workpiece. The stop 1a actuates the motor 12 to advance the wheel at a slow speed, 0À002 to 0À1 mm.sec., to effect grinding to within a small distance of the finish size: as the wheel contacts the workpiece, the motor 12 is stopped and the table T is adjusted, if necessary, to effect grinding of the shoulder of the surface. Thereafter, the grinding wheel is advanced at an even slower speed of 0À01 to 0À001 mm/5 sees. Finally, the grinding wheel is rapidly retracted and the table positioned for grinding the next surface, the process being repeated for each of the surfaces to be ground. In another embodiment, the grinding wheel is on a carrier fast with a block 28, Fig. 9, having two half nuts 30, 31 engaging a screw 29 rotatable in a bearing 34 by gearing from a stepping motor 36, a similar arrangement being provided for moving the workpiece table. The embodiment may be used to grind a stepped bore in a workpiece. When the grinding wheel is trued, it is automatically advanced a distance to compensate for its reduction in size.