Patent GB-244896-A (GB)
Title: Improvements in or relating to the production of gear wheels
IPC: B23F5/20
Filed: 1924-11-27
Abstract: 244,896. Brown & Sons (Huddersfield), Ltd., D., and Brown, F. E. Nov. 27, 1924. Gear-cutting; milling-cutters.-In a gear-hobbing machine, a series of hobs are disposed ai intervals around a rotary carrier 1 provided with a series of work tables 3<a> - - 3<d> which are rotatable independently of the carrier. For cutting worm-wheels, the machine preferably has two diametrically opposed cutter' heads (one of which is shown at 4 in Fig. 1) carrying hobs 4<a>, 5<a>. The carrier is driven slowly while the blanks are passing the hobs and quickly past the intermediate positions. The hobs may both be finishing-cutters which complete the work in one traverse, and in this case, during the periods of slow movement of the blanks past the positions A, B between the cutter heads, the finished blanks are removed and fresh blanks positioned. Alternatively, one hob may be a roughing tool and the other a finishing tool. The carrier is driven from a main-shaft 6 through change gears 8, shaft 9, worm gearing 10, shaft 12, change gears 13, worm gear 16, reversing bevel gearing 19, worm gear 23, shaft 25, and worm gear 26. This mechanism imparts the slow movement to the carrier, and to produce the accelerated movements at the required times, a shaft 28, driven from the main shaft, is arranged to drive a gear carried by the bevel wheel 18, pawl mechanism in the worm gearing 16 permitting the slow drive to be overrun. The belt driving the shaft 28 may be shifted automatically between the fast and loose pulleys 31, 32 by means of dogs suitably arranged on the carrier. To provide for the rotation of individual work-holders, the shaft 9 drives through change gears 33, differential gear 36, shaft 37, and worm gearing 38, a wheel 39 carrying a wheel 39<1> which drives the work-tables through a series of pinions 40, 40<1>. The rotation of any particular worktable may be arrested either by hand clutches connected with the pinions 40<1> or automatically, when the table reaches a loading position, by mechanism actuated from the carrier. The differential gearing 36 is connected to the shaft 17 so that the speed changes of the latter shaft cause corresponding variations in the work-table speeds. The hob 4a is driven from the shaft 9 through bevel gears 49, shaft 50, bevel gears 51, 53, and worm gearing 55, the second hob being driven similarly from a bevel gear 56. To compensate for the circular movement of the carrier each cutter head is radially movable, and a bar 60, connected through a lever 61 to the head feed screw is adapted to engage a suitable cam on the carrier so as to move the hob forward as the blank commences to recede from the centreline of the hob, the movement being such as to render the blank movement relative to the hob equivalent to a tangential one. The compensating means may also move the cutter head outwards during the blank approach in addition to the inward movement as the blank recedes. In a modification for hobbing spur gears, three cutting-heads are provided and the slow movement past the position A permits of loading and unloading. One hob roughs out the teeth, a second hob finishes one side, and a third hob the other side of the teeth. The finishing hobs are ot taper form, their operative surfaces 69 being perpendicular to the hob axis as shown in Fig. 4. The hobs are of large diameter so that no relative movement axially of the work is necessary. By inclining the hob axes and modifying the driving gearing, helical gears may be cut.