Patent GB-192178-A (GB)
Title: Improvements in gear cutting machines
IPC: B23F1/04
Filed: 1921-10-31
Abstract: 192,178. Gwynne, N. G., and Rath, A. Oct. 31, 1921. Gear-cutting. -In a machine for cutting spiral bevel gears by means of templets, the blank is constantly rotated while the tool is reciprocated to and from the cone-apex of the blank, the cutting strokes of the tool. actuated by a spiral cam, being so timed with respect to the revolution of the blank that alternate teeth are engaged at each working stroke. On the return stroke the tool slide is actuated by a second cam, these cams being preferably designed so that the tool is cutting while the blank rotates through one and one third pitch intervals and is returned during two thirds of a pitch interval. In the form shown the blank b is secured to a spindle a mounted in an adjustable headstock and driven from a main driving shaft, f through a countershaft 113, bevel gearing 119, spindle 120, change-gearing 127, shaft 123 and worm gearing 133. A clutch 128 on the worm shaft may be disengaged to disconnect the power drive and permit indexing of the blank by manual operation of the squared end 132. The desired indexing movement of the blank is secured by means of a notched flange 141 coacting with a tooth on the spindle 120 forming one member of the driving train. A plurality of notches are provided in the flange 141 to allow for variations in the indexing so that in some cases teeth having longer or shorter addenda than standard may be cut. The tool c is secured to a holder g pivoted at h to a rest j adjustable in guides in a slide l. The latter is carried in a support m pivoted at o to a rotary head p, the arrangement being such that the centre lines of the pivot o and the vertical pivot of the rotary head both pass through the cone apex of the blank. As the tool c is fed into the work the member m is rocked to shape the teeth by means of an arm q coacting with templets s, s<1> carried on an adjustable disc u, one templet being provided for each side of the teeth. The tool slide l carries an extension plate l<2> carrying rollers 4, 5 coacting respectively with cams 6, 7 rigidly secured to the hub of a toothed ring 11 driven to reciprocate the tool in unison with the blank by a gear train from the main shaft f, the train comprising a bevel gear 23 coaxial with the pivot of the tool supporting member m. In order to compensate for the effects of the rotary movement of the head when cutting feed is applied and of the templetcontrolled rocking movement of the member m differential gears 29 and 41 are provided in the cam-driving gear train. As shown in Fig. 4, the cams 6, 7 are so arranged that a uniform cutting speed and quick return are imparted to the tool. The tools are relieved from the work on the return stroke by means of a face cam 14 on the wheel 11 which coacts with a lever 17 to rock a shaft 15 which operates to swing the toolholder About its pivot h against a spring 21. The rotary head p carries a toothed flanged ring 44, Fig. 4, engaging a pinion 48 on a spindle driven through worm gearing from a shaft z operated to apply intermittent cutting feed to the tools, from the driving shaft f through a clutch member y which is manually locked to engage a sleeve 72. The latter carries a ratchet ring 73 actuated through adjustable lever mechanism from a striker 79 fixed to a planet gear 80 running 'on a fixed gear 81 and mounted in a bearing carried by the indexing wheel on the work spindle. When a blank having an odd number of teeth is to be cut the gearing is so arranged that the striker operates to ieed the tools after two revolutions of the blank when all the teeth will have been partly cut on one side. For cutting an even number of teeth the feed may be actuated at every revolution of the blank by adding a second diametricaily opposed striker to the gear 80 or alternatively by altering the ratio between the gears 80, 81. In order to disengage the feed when the required tooth depth is attained a notched disc 100 driven from a pinion 109 on the feed shaft z co-operates at a predetermined point with an arm 99 on the' clutch-rod to disengage the clutch-looking means whereupon the clutch is automatically engaged with a sleeve 71 reversely driven from the countershaft 113 to effect a quick return of the rotary head. The clutch is then automaticallv shifted to a neutral position. At the commencement of the next cutting operation this clutch y is again set and locked by hand.