Patent GB-1081561-A (GB)
Title: Improvements in or relating to machining apparatus for example for operating dressing tools for grinding wheels
IPC: B24B53/08
Filed: 1965-01-29
Abstract: 1,081,561. Truing grinding wheels. NEWALL ENGINEERING CO. Ltd., W. K. TEMPLE, and D. A. BAKER. Jan. 25, 1966 [Jan. 29, 1965], No. 4171/65. Heading B3D. Machining apparatus for traversing a tool, such as a diamond dressing tool along the periphery of a workpiece, e.g. a grinding wheel 10, and round a radius at one lateral edge of the surface comprises a tool-holder 21 rotatably mounted on a slide 17 which is mounted for rectilinear movement on a support structure 14, a rack 51 mounted on the slide for rectilinear movement relative to the slide and connected through a lost-motion mechanism to move the slide rectilinearly on the support structure, stop means for limiting movement of the slide, a gear 49 rotatably mounted on the slide and meshing with the rack to rotate the tool-holder, whereby movement of the rack relative to the slide to take up the lost-motion rotates the toolholder, a motor 60 for driving the rack relative to the support structure in such a manner that the linear speed of movement of the rack relative to the support structure bears a constant relationship to the motor speed over the full movement of the rack, and spring means for ensuring that the slide is stationary whilst the gear is driven by the rack and that the gear does not rotate when the slide is in motion. The support structure is adjustable perpendicularly to the axis of the grinding-wheel on a base part 13 by a screw-and-nut mechanism 15, 16. The slide 17 is supported for movement parallel to the axis of wheel in crossed roller bearings 18 in the support structure 14 and rotatably supports a first shaft 20 having a cranked portion 21 supporting the diamond dressing tool 12 which is adjustable lengthwise to position its tip at a distance from the axis of the shaft 20 equal to the radius to be formed on the corner of the grinding wheel. The toolholder is also indexable so as to rotate the tool through a small angle after each pass. The shaft 20 is connected by a pin 27 movable in an arcuate slot 28 with a gear segment 30 rotatably mounted on the shaft and meshing with a gear 31, Fig. 2, associated with a spiral spring 35 which urges the pin towards one end of the slot, the gear 31 and spring being mounted on a second shaft 32. A gear 65 on the first shaft meshes with a gear segment 46 on a third shaft 47 formed with a pinion 49 engaging the rack 51 which is mounted on needle bearings 52 and is also engaged by a pinion 57 on a shaft 58 having further pinion 59 engaging a rack in the piston 60 of an hydraulic motor. A hub 65 secured to the shaft 20 is connected to one end of a spiral spring 66, the other end of which is secured to an adjustable drum 67. Further tension springs 70, Fig. 3, urge the slide to one side, and the springs are adjusted so that the force of springs 70 is greater than the force of spring 66 acting on the rack, and the force of spring 35 acting on the rack is greater than the combined force of springs 66 and 70, the springs acting in the directions of the arrows in Fig. 3. The movement of the rack is limited by adjustable stops 54, 55 and the movement of the slide is limited by adjustable stops 75, 76 engaging fixed stops 73, 74. In operation, and with the parts as shown in Fig. 3, movement of the piston moves the rack 51, the spring 35 overcomes springs 66 and 70 and acts through the gear 31, segment 30 and pin 27 to rotate shaft 20 and tool 12 through 90 degrees to the position of Fig. 4 (not shown), in which a peg 41 engages a stop 42, the piston then moving the rack and slide, spring 20 overcoming spring 66 and spring 35 not being effective, wherein the slide abuts stop 75. Continued movement of the piston permits spring 66 to rotate shaft 20 and tool 12 to move to the position of Fig. 6 (not shown), springs 35 arid 20 not being effective. The gear ratios are such that the linear speed of the tool is constant over the arcuate and straight portions and the speed may be varied by rate valves in the supply of fluid to the motor.