Patent GB-789727-A (GB)
Title: Method and machine for the production of helical teeth
IPC: B23F1/02
Filed: 1954-11-23
Abstract: 789,727. Grinding gears. MAAG GEARWHEEL & MACHINE CO., Ltd., and WILDHABER, E. Nov. 23, 1954 [Nov. 27, 1953], No. 33988/54. Class 60. [Also in Group XXII] A method of producing modified helical teeth on gears, including worms, by means of a formed totary tool, e.g., a grinding wheel, in which the tool and the work piece are fed relatively to each other in repeated helical passes or strokes about the axis of the work piece, is characterised in that an additional relative motion consisting of two components is effected between the tool and the work piece, one component affecting the tooth thickness and extending during a helical pass first in one direction and then in the opposite direction in the region of finishing contact between tool and work piece, the other component being without reversal during said pass and moving the tool axis and the work piece relatively to each other in a direction inclined to the axis of the work piece and approximately tangential to the produced tooth surfaces of said region. The two components of the additional relative motion at the end of a tooth space are (1) displacement of the axis of the tool from location 60, Fig. 12, to location 60a, i.e., depthwise feed to ease off the tooth, and (2) displacement of the axis of the tool from location 60a to location 60<SP>1</SP> by movement about axis 85 parallel to the tool axis, thus ensuring the correct pressure angle. These two components can be compounded into a movement of the axis of the tool from location 60 to location 60<SP>1</SP> by movement about axis 87 parallel to the tool axis. The grinding wheel W<SP>1</SP> Figs. 14 and 15 is secured to a shaft 95 driven by pulley 113 and mounted in a holder 96 radially adjustable in a pivot member 97 pivotally mounted about axis 87 in a wheel head 99 in two spaced bearings 100, 100<SP>1</SP> which may be antifriction bearings ; the pivot member 97 swings in time with the working stroke. To effect the adjustment of the holder 96, a shaft 104 carries bevel gears 103 meshing with bevel gears 102 integral with nuts engaging screws 101; the end screws 101 are rigid with holder 96 and the middle screw 101 bears against an elastic disc 105. The wheel head 99 is adjustable for helix angle on ways 110 curved about axis 111. In a modification, Figs. 16 and 17, the grinding wheel shaft 95 rotates in a holder 115 having spaced gears 116, 117 rigid with it coaxially with the shaft ; the teeth may be helical and are then of opposite hand on the two gears. Each gear meshes with a rack rigidly secured to a pivot member 118 mounted for oscillation about axis 130 in spaced bearings 131, 132 in the wheel head 133. Intermediate the gears the holder rotatably carries a block 120, comprising parts 1201, 12011 secured together, adjustable radially in a rectangular opening 121 in a part 122 which during grinding is fixed relative to the pivot member 118; the adjustment is effected by a screw 123, the gears 116, 117 rolling on their racks to maintain parallelism of the holder 115. Part 122 comprises parts 122<SP>1</SP>, 122<SP>11</SP> secured together, part 122<SP>1</SP> having a cylindrical outside surface 134 engaged by a stop 135 during the grinding passes. Part 122 is slidable in a transverse cylindrical hole 136 in pivot member 118. Periodic advance and withdrawal of the grinding wheel to and from working position is effected by a cam 140 on shaft 141 mounted in the wheel head 133 and driven by worm wheel 146 so as to perform one complete turn between successive grinding passes. A spring 142 acts on a lever 143 carrying a roller 144 bearing against a cylindrical surface 145 on part 12211. The required timed rocking motion on pivot axis 130 is effected by a cam 150 on shaft 141 engaging a roller on the pivot member 118, engagement between cam 150 and roller being maintained by spring 152. The plane of symmetry of the tool includes a larger angle with the direction of the blank axis than the helix angle at the pitch radius of the blank ; the grinding wheel is given the appropriate profile by dressing means described in 789,728.