GB1285070A - Improvements in or relating to gear making - Google Patents

Abstract

1285070 Gear cutting; blanks transferring; indexing BIRD ISLAND Inc 17 Nov 1969 [25 Nov 1968 25 July 1969 28 July 1969 8 Aug 1969] 56159/69 Headings B3B and B3K Apparatus for cutting gear teeth comprises a rotary cutter with profile generating cutting edges lying along straight lines and a rotatable work support, both arranged to rotate at basic rates about their respective axes and being relatively movable along a given linear path, the basic rate of rotation of the cutter or of the work support being modified upon the occurrence of this relative movement, successive cutting edges operating on successive tooth flanks so that one or more complete revolutions of the workpiece intervene between successive cuts on the same tooth flank. A work blank 20 is mounted on a rotary spindle 25 on a slide 26 which is movable in a direction perpendicular to the axis of the blank and parallel to the axes of two contra-rotating cutters 36, 38. Drive is transmitted from a common motor 60 to the blank spindle 25 and to the cutters 36, 38 the latter being driven through oppositely handed worms 82, 84 mounted on a shaft 80 which can be controllably displaced to modify differentially the speeds of the cutters 36, 38 in dependence upon the traverse movement of the blank therebetween. Linear displacement of the shaft 80 is effected by means of a cranked lever 132 which is caused to pivot when feed of the blank between the cutters takes place by the engagement of a screw 154 forming part of a phase control unit 155, with a flat 152 on the lever. The feed of the slide 26 carrying the blank is effected by a power cylinder 180 having its rod 181 connected to the slide 26 and is initially rapid until a screw 192 of a feed control unit 182 contacts a fixed abutment 189; thereafter the feed speed is controlled by the speed of retraction of the screw, motion of which is derived from a variable speed hydraulic motor 212 and gearing 202, 204, 206, 198, 196, 197. The drive to the feed control unit is arranged to reverse the direction of movement of the screw 188 when the blank has been cut to full depth and the slide 26 then begins to retract against the action of cylinder 180. The final retractive movement of the slide 26 is rapid and is effected by the cylinder 180. The speed of the variable speed motor 212 is controlled by a control valve 194 regulated by a cam 214 itself driven by the motor 212. A further cam 216 driven by the motor 212 regulates the position of the screw 154 of the phase control unit 155 and the cam 216 can therefore be designed to alter the phase relationship of the cutters for the return cutting cycle thereby altering the tooth thickness or modifying the involute profile of the teeth; furthermore the cam 216 can be designed so that the generating edges of the cutters do not cut on the forward stroke during which only the roughing edges operate while the final desired profile is generated by the generating cutting edges on the return stroke, thereby lengthening cutter life. In an alternative embodiment of the machine (Figs. 31, 32, not shown) movement is imparted to the slide carrying the two drive worms for the cutter spindles and transmitted to the work slide by a pivotally mounted cranked lever. Cutter and cutter mounting (Figs. 8, 9 and 22). -Each rotary cutter 36 or 38 comprises a mutliplicity of (e.g. 90) cutting tools 226 mounted in V-shaped grooves 227 in a body 220 each tool having two cutting end portions 242 and 244 selectively used according to which cutter (36 or 38) it is to be mouunted in. The tools have straight profile generating edges 252 (or 268) which lie in a common plane (or, in a separate embodiment, Fig. 30 (not shown), in a wideangled cone by which crowned teeth may be produced), roughing edges 256 (284) and formed tips 254 (271) which are adapted to form the root fillets of the teeth. The tools are located against a ring 280 bolted to the body 220 and are clamped by screws 230 which pass through an annular slot 229 in a cover plate 228 bolted to the body 220. A ring 234 containing small spherules of e.g. tungsten alloy is bolted to the plate 228 and serves to absorb vibrations generated during cutting. The cutter 36 is bolted to its spindle 90 which is mounted to rotate in an eccentric sleeve 92 which can be adjusted in position to alter the distance between the cutter and workpiece axes. In an alternative embodiment of the cutter (Figs. 33, 34, not shown) each tool has on its upper surface a projection of wedge-shaped section which engages in a corresponding groove in the clamping portion of the cutter body and serves to locate the cutting tool. Blanks transferring (Figs. 1, 3, 18, 20).- Blanks 20 are supplied from a vertical tube 364 to a channel 362 and pushed therealong by a cylinder operated push rod 366, 368 to a spring loaded detaining block 372. Adapters 46, 48 are mounted on a spider 50 itself mounted on the slide 26 and adapted to be raised and lowered and, in the raised position rotated through 180 degrees to pick up blanks from the detaining block, transfer them to the work spindle 25 hold them on the spindle 25 during machining and finally deposit them in a discharge shoot 390, the sloping slotted upper surface of which strips the completed gear from the mandrel 300 of the adapter as the latter moves with the angularly swinging spider 50. Raising and lowering, and pivoting of the spider is effected by power cylinders 334, 340 respectively. Cylinder 340 has a rack on its outer surface adapted to mesh with a drive pinion secured to the spider. Each adapter has an expansible mandrel 300 arranged to be expanded by vertical movement of a rod 310 in the work spindle to grip both the blank and the wall 311 of the work spindle thereby providing a drive connection. The workpiece is held on the mandrel when it is not expanded by a rubber 0-ring 302. When the spider 50 is in its lowered position two pins 339 register in holes 337 in a mounting bracket 322 to locate the spider accurately. Motors 304, 306 may be used to accelerate the work blanks on the respective adapters up to the speed of the work support 25 and to brake them after removal therefrom.