Patent GB-226878-A (GB)
Title: Improvements in and connected with apparatus for machining spiral tooth gear wheels
IPC: B23F1/06
Filed: 1923-10-01
Abstract: 226,878. Rath, A. J. Oct. 1, 1923. Gear-cutting. - In a machine for cutting spiral gear wheels, particularly for roughing out the teeth of spiral bevels, a formed milling - cutter rotating in a plane inclined to the blank axis is moved rectilinearly past the rotating blank so as to cut a complete tooth space in one traverse, the blank being then withdrawn laterally and indexed, preferably through two pitches, and the tool returned for cutting the next tooth. The framing a, Fig. 1, is provided with a horizontally sliding saddle c carrying a revoluble work-table d pivotally adjustable about the axis of a shaft 34 bevel-geared to a shaft 32 which drives the table through worm-gearing 37. The framing is also provided with vertical guides for a saddle g counterbalanced by a weight 60 and carrying a cutter head h supporting the cutter-spindle j which is driven through bevel and spur gearing from a shaft 49. The cutter-head is adjustable about the axis of the shaft 49 and the cutter-spindle, which is inclined outwardly from the saddle g, is provided with a ball thrust bearing and is axially adjustable from a hand-wheel 59. The machine is operated from a main shaft n driven by a pulley o and carrying a wheel p which, through a change and reversing-gear q and bevel gearing 53a, drives a vertical shaft 53 which carries a splined bevel-wheel 52 from which the cutter-spindle is driven. The main shaft also carries a pinion r driving through change gears a low-speed worm spindle u, and a skew gear v driving a high-speed spindle x. The high and low speeds are controlled from a timing-shaft y which may he driven from the low-speed worm 1 through a worm-gear z or from a high-speed pinion 16 engaging a wheel 13<a> and engaged when required with a sliding clutch member 46 operated by a cam disc 17 on the timing shaft. The hub 2 of the wheel 3 is provided with a freewheel device to allow the shaft y to overrun the worm wheel when the high-speed clutch is engaged. The motion of the shaft y is transmitted to an operating-shaft 23 through an interrupted gear 13<a> engaging a wheel 22, accidental movement of this wheel when opposite the mutilated portions 14 and 15 of the gear 13<a> being prevented by means of a locking-lever 21 operated by a cam 20 on the timing-shaft. The operating-shaft 23 is connected through a. vertical shaft 26, gearing 44, shaft 43, and skew gears 42 with the shaft 34 from which the blank table is rotated while cams 27, 28 on the shaft 23 actuate a toothed rack 29 connected through gearing 31, shaft 31<a>, and rack-and-pinion gearing 31b to impart vertical reciprocating movements to the cutter saddle. The lateral movements of the blank saddle to withdraw the blank for indexing are effected from a cam drum 4 on the timing-shaft which actuates a rock-shaft 6 connected by a rod 8 and lever 9 to a second rockshaft carrying a quadrant 11 engaging a toothed rack-bar c secured to the blank saddle. A scale is provided along a slot in the lever 9 so that the extent of the blank withdrawal movement may be adjusted. In order to permit the complete withdrawal of the worktable from the cutter to remove a finished article and position a fresh blank the rack bar e is provided with a toothed portion 65 engaging a pinion 66 on a shaft 67 provided with a braking member 69 co-operating with a drum 68 and actuated by a handle 70. The brake is normally engaged as shown in Fig. 2 so that the pinion 66 serves to lock the work saddle to the rack-bar but by depressing the handle 70 the brake is released and the pinion 66 may then be rotated by means of the handle to withdraw the work saddle, the rack-bar being prevented from moving by the rod 8. A rod 71 secured to the work saddle moves through a guide 72 on the rack bar and carries an adjustable stop 73 and accurate positioning of the saddle is ensured by bringing the stop 73 against the guide 72, when a fresh blank is to be cut. The pivotal movement of the worktable about the axis of the shaft 34 is effected from a hand-wheel 79 through bevel gearing 77 and worm-and-sector gearing 74. In operation the cutter-spindle being in its raised position the timing-shaft is driven at the low speed and the operating-shaft, 23 is stationary owing to the gap 15 being opposite the wheel 22. The rod 8 is then actuated by its cam to feed the cutter to the full tooth depth the gears 13 and 22 at the same time coming into mesh to start the rotation and downward traverse of the cutter spindle and the rotation of the work piece. When the cutter completes its traverse the rotation of the shaft 23 is again interrupted and the worktable is withdrawn by the rod 8, the clutch 46 being engaged automatically so that this withdrawal is effected at high speed. The gears 13 and 22 then again engage to index the blank and return the cutter head to its raised position. Finally the work table is returned and the low speed is re-engaged for a fresh cycle of operations. Milling-cutters. - The cutter spindle is angularly disposed with respect to the blank as shown in Fig. 5, and in order to obtain clearance during the cut, the side k<1> of the cutter engaging the concave face of the tooth has a greater bevel than the side k<2> engaging the convex face.