Patent GB-1070270-A (GB)
Abstract: 1,070,270. Grinding gears. MICHIGAN TOOL CO. Oct. 28, 1965 [Jan. 28, 1965], No. 45706/65. Heading B3D. A form-wheel grinder for grinding internal or external spur and helical gears comprises a sine bar 64 which is mounted at one end on a pivot and has its other end vertically adjustable to vary its inclination, a column 73 mounted on a reciprocable table 12 adjacent the sine bar and supporting a slide 76 for vertical movement, a cam follower 84 carried by the slide and resting on the sine bar, a work spindle 25. which is mounted in a head on the table and has an index plate 32, a pawl 55 in a pawl assembly selectively engageable with the index plate, means interconnecting the pawl assembly and slide so that movement of the slide causes the pawl assembly to rotate the plate, and hence the work spindle, and means to compensate for the variations in rotational forces acting on the work spindle upon rotation in opposite directions. The table 12 is reciprocable on a base (10, Fig. 1) having a column (18) supporting a wheel head (17) for vertical movement, the wheel head carrying a grinding wheel (19) at the end of an arm (21) and having means (22) for adjusting the head about a vertical axis to correspond to the helix angle of the gear to be ground. The work spindle 25 is mounted, at one end, in bearing (28, 29, Fig. 5) in the head (24), and, at the other end, in bearings (26, 27) in a sleeve (43), in turn, mounted in bearings. (44, 45) in the head. The index plate (32) is secured to one end of the spindle and carries one member (35) of an electromagnetic clutch (48) engageable with a second member (47) on the sleeve (43). The second member is connected to a gear (46) meshing with a gear (63) of a coarse locator for the index plate, the gear being mounted on a shaft (61) having a pinion engaged by a rack (57) movable by an hydraulic motor 56, Fig. 2, between positions determined by limit switches 64A, 65A. The index plate is accurately located by the pawl 55 which is movable out of engagement with the plate by a solenoid (53A, Fig. 5) acting against a spring (53), the solenoid being carried at the end of an arm (39) secured to a hub (41) in turn secured to the sleeve (43). Opposed pairs of tapes 96, 97 and 101, 102 are secured at one end by clamps 99, 104 to the hub 41 and at their other ends by tensioners 98, 103 to the upper and lower ends of the slide 76 which is movable on vertical ways 74, 75 on the column 73 which is mounted adjacent the spindle head 24 on the reciprocable table 12. A bracket 77 extends from the slide and rotatably supports a spindle 78 having a screw-thread engaging a nut 79 on a support 81 which is slidable in vertical dovetail ways 83 on the slide 26 and has a cam-follower in the form of a roller 84 engaging the sine bar 64, one end of which is mounted on a pivot (66, Fig. 3) and the other end of which is adjustable by gauge blocks (69) engaging a roller (68) on the bar to vary the inclination of the bar. Wipers (86, 87) on both sides of the roller (84) remove foreign matter from the surface of the sine bar. The spindle 78 can be rotated by a motor 93 to vary the position of the slide 76 relative to the follower 84 and hence adjust the rotational position of the work spindle relative to the follower. The weight of the slide 76 is partly compensated by a weight (92, Fig. 3), on a cable (91) running over pulleys (88, 89) and connected to the slide. In order to compensate for the different rotational forces when the roller is moving up as compared to down the sine bar, an hydraulic motor (106) is mounted on the column (73) and has its rod (107) connected to the slide (76). In operation, the movement of the table in one direction cause the cam follower to move down the slope of the sine bar and the slide 76 to move downward to rotate the pawl and hence the work spindle in one direction to cause the grinding wheel to grind the helical flanks of the workpiece. If one or other flank is not being properly engaged by the grinding wheel, the operator can jog motor 93 to adjust the slide, and consequently rotate the work spindle, relative to the cam follower. As the follower moves down the incline of the sine bar, the hydraulic motor 106 is actuated to urge the follower against the sine bar, but on the reverse movement as the follower ascends the incline, the motor is not retracted, the stresses on the parts being those necessary to raise the slide 76 and its connected parts. The motor simulates those stresses during the downward movement of the follower. After one space has been ground, the clutch coil (48) and solenoid (53A) are energized to engage the clutch (35, 37) and withdraw the pawl 55 so that when the motor 56 is energized, the movement of the rack 57 causes rotation of the index plate 32 with the workpiece spindle, the coil and solenoid then being de-energized to permit the pawl to engage the next space to accurately locate the workpiece spindle. In another embodiment, the compensating motor 106 between the column 73 and slide 76 is replaced by a device between the cam follower support 81 and slide 76. The device (Figs. 6 and 7) consists of a nut (202) which is rotatably mounted in a bracket (203) on the slide (76) and connected by a chain drive (206) to the motor (93). The nut is engaged by a lead screw (211), the head of which is disposed between spring washers (214) and a spring reed (217) in a bore (208) in the support (81). Normally the washers are stronger than the reed and in one direction of movement, the parts are in the position shown whereas, in the other direction of movement, a piston (219) is subjected to pressure in a bore (222) to move the reed an amount determined by an adjustable stop (224) against the force of the spring washers. A horizontal track (72, Fig. 1) is contiguous with the pivoted end of the sine bar and is used during the grinding of normal spur gears.