Patent GB-332792-A (GB)
Title: Improvements in method of and apparatus for generating helical gears
IPC: B23F5/02
Filed: 1929-08-29
Abstract: 332,792. Simmons, O. G. Aug. 29, 1929. Gear-cutting.-In a machine such as that de. scribed in Specification 268,802 for grinding involute gears of any required pressure angle, an adjustable head carrying the grinding-wheel is provided with a motor for driving the wheel and is angularly adjustable through a wide range about a, vertical axis in order to give the required inclination to the grinding-wheel for grinding helical gears. The base 1 carries a segmental bed 3 provided with a scale 5 which indicates the angular adjustment of a head 6 carrying- the grinding wheel. A slide 11, adjustable radially on the head 6 by means of a hand-wheel 12. carries a housing 13 for a motor which drives the grinding-spindle 16, the latter being carried on a vertically-adjustable slide 15 carried by the slide 11. A standard 19 attached to the head 6 carries a vertical slide 20 fitted with a barrel 22 in which moves a slide 23 carrying a dressing- tool 24 which may be reciprocated across the face of the wheel by means of a hand-wheel 25. The wheel may be adjusted towards the dressing- tool to compensate for wear by operation of the slide 11 and is preferably enclosed in a dust. guard 26 having a removable front face 27. In a modification, Fig. 8, the dressing-mechanism mav be mounted on the wheel dust, guard 61 which is provided with a guideway 62 for a slide 63 adjusted from a micrometer head 66. The slide 63 carries a swivelled head 68 angularly adjustable by means of a scale 69 and having a barrel portion in which the diamond-carrying slide 72 is reciprocated by gearing operated from a hand wheel 74. The front 75 of the dust guard is detachable and has a sight-opening which is normally covered by a pivoted plate 76. The work bed 29 is pivotally mounted on a bearing 28 whose axis intersects the vertical pivotal axis of the bed 6 and the work bed is angularly adjusted to the required pressure angle (indicated on a scale 32) by worm and segment gearing 30. The work-spindle 34 is mounted within concentric sleeves 35, 36 carried by a slide 33 which moves under the control of an involute cam 37 to give the required rolling movement to the work. The support 39 of the abutment roller 38 may be adjusted by a screw 42. The black is indexed while out of engagement with the ending-wheel by means of an index-head 43 operated by a flexible shaft 44 and' the oscillation of the work-spindle for the generating movement is effected by means of a connecting-rod 46 connected to a crank 48 mounted on a shaft 49 which is oscillated from the main driving mechanism. The cam 37 is held against its abutment roller by means of a counterweight, carried by a cable 50. The blank is mounted on an arbor 54 which is secured at 55 to the spindle 34 and is supported at the outer end on a dead centre 56 carried by a tail-stock mounted on a rigid arm 58. The grinding-wheel and workspindle are driven by independent motors controlled by switches 59, 60. When helical teeth are generated the angle to which the grinding- head 6 is turned is different from the helical angle required on the work on account of the inclination of the imaginary rack plane C, Fig. 6, in which the slide 33 moves, to the horizontal plane B in which the head 6 is rotated. The grinding face of the wheel always lies in a vertical plane A. The angle between the planes B, C. is the pressure angle Y. If X represents the helical angle measured in the plane C, required on the work and Z the angle, measured in the plane B, to which the wheel must be adjusted to generate teeth of helical angle X, then from Fig. 6, tan Z = ef/ea = eg/ea cos Y = tan X cos Y, this formula giving the required' angle of adjustment of the wheel.