Patent GB-503952-A (GB)
Title: An improved method of and apparatus for finishing gears
IPC: B23F23/12
Filed: 1937-07-12
Abstract: 503,952. Gear - cutting. NATIONAL BROACH & MACHINE CO. July 12, 1937, No. 19304. Convention date, July 13, 1936. [Class 83 (iii)] Gears are finished by running the gear in mesh with a rotary gear-form cutter arranged on a non-parallel axis and having cutting edges formed in the sides of the teeth, feeding either the gear or the cutter in a plane parallel to the axis of the other and automatically inclining the axis of the gear or cutter with respect to the other in timed relation to the feed movement. The frame carries a swivel head 26 carrying a cutter 28 driven by a motor 29. The table 31 carrying the work-gear is movable vertically by a screw 32 operated either automatically or manually from a hand wheel 35. The worktable also carries a reversible electric motor which drives a screw 37 for reciprocating the work-gear carriage 38. The reversing-switch is actuated by lever mechanism 40, 44 from adjustable stops 42, 43 on the carriage. The carriage is provided with a platform which is pivoted on central trunnions 47 and is fitted with head and tail stocks between which the work arbor 53 is mounted. A roller 56 on the carriage engages in an adjustably inclined slot 57 in a member secured to the work table. Thus as the work carriage reciprocates, the inclined slot causes the work platform to rock on its trunnions and produces a crowning effect on the work-gear teeth as shown in Fig. 6 the crowning action being variable according to tho angular setting of the slot. The work-gear and tool-gear axes are mutually inclined at an angle between 3 and 30 by swivelling the head 26. At the end of each reciprocation or after a predetermined interval the table 31 is automatically elevated to feed the work to the cutter. In place of a standard involute tool gear indicated in dotted lines in Fig. 8 the profile of the tool gear may be modified as shown in full lines. In this way the work teeth are relieved at the top and the root in addition to having a crowned formation. In' a modification, in place of the oscillating platform, the carriage 65, Fig. 5, carries the head and tail socks and has a concave lower surface moving on a corresponding convex surface on the table. The preferred angular settings of the tool and gear axes for gears of various helical angles are given in the Specification. The motions for producing the tooth crowning may also be given to the tool-head instead of to the work-gear. Specification 415,875 is referred to. The Specification as open to inspection under Sect. 91 describes also a modification, Fig. 5 (Cancelled), in which the table is moved vertically at the ends of the carriage movement so as to remove more metal at'the tooth ends and give a crowning effect. In this form, dogs on the carriage actuate a switch lever 71 controlling a motor 70 driving the feed screw 32 so that the carriage is moved up near one end of its stroke. 'The reversing mechanism of the main motor then reverses the motor 70 which returns the table to normal position when the motor is stopped by a stop on the wheel 68. At the opposite end of the stroke the same cycle takes place. In another modification the raising and lowering of the table at the ends of the stroke may be effected mechanically. In a further modification a similar table movement is effected by gearing driven from the table feed screw which drives a cam acting through a lever to raise the entire table mechanism. In some cases the crowning effect may be obtained by modifying the tool gears without any other movement of the work-table than its rectilinear reciprocation. For this purpose the normal grooved cutter 101, Fig. 8 (Cancelled), is flanked by two other cutters 102, 103 of bevelled formation which engage the ends of the workgbar as it reciprocates and take an additional cut at the tooth ends to produce a crowning effect. In a modification, the side cutter portions 113, 114, Fig. 10 (Cancelled), may have the same diameter but different helical angle from the central portion. This produces relieved toothed portions which are on opposite sides at opposite ends of the work teeth. In a similar modification the outside cutting tools may be provided with cutting teeth on one side only, the opposite sides being plain and serving as guides. This subject-matter does' not appear in the Specification as accepted.