Patent GB-554500-A (GB)
Title: Improvements in or relating to work holder for broaching machine
IPC: B23D37/16
Filed: 1941-11-26
Abstract: 554,500. Broaching-machines. LAPOINTE MACHINE TOOL CO., Ltd. (Lapointe Machine Tool Co.). Nov. 26, 1941, No. 15234. [Class 83 (iii)'] A work holder for a broaching machine, for broaching tubular work such as gun-barrels by successive operations with a number of broaches comprises a head portion H and a tail portion T connected together by a tube 60 each portion having a number of work-engaging devices rotatably mounted thereon and both positions being rotated step-by-step to alternate broaching and broach-returning positions. The head portion is fixed but the tail portion is adjusted according to the length of the work pieces W on guide bars 10. The head has five working positions and one loading position and six intermediate broachreturning positions. A notched indexing-ring 18 secured to the rotary part 12 of the head coacts with a locking-pawl 70 which is withdrawn against a spring 78 by a single-acting hydraulic cylinder and a feed pawl 71 pivoted on a plunger 89 actuated by a double-acting hydraulic cylinder 83. Each work-holding device comprises a hollow spindle 30 having an enlarged work-gripping head 31 and rotatable on ball bearings 32. Each spindle carries a gear 33 engaging through an idler with a central gear 37 which is grooved to coact with spiral splines on a shaft 41 which moves with the broaches during operation so that a timed rotation is imparted to the work pieces to produce the required rifling. The tail part T is keyed at 61 to the tube 60 and is fitted with ball bearing tail-centres 52 which are urged outwardly to engage the work pieces by springs 55. At the intermediate broach-return positions the heads are connected by broach-guiding tubes 67 and after completion of an operation the heads are indexed through 30 degrees to bring the heads to a broach-return position. The hollow spindles 30 are aligned with passages 90 in the fixed part of the head H and the tail part has an extension 92 provided with bores 94 in alignment with the tail-centres and bores 95 aligned with the broach-return passages 66. A fixed plate 98 is fitted with slidable bushings 97, coacting with spring-pressed caps 98a mounted on the ends of broach-gripping devices 100 on a puller head P. After the broaches have been drawn through the work, the heads are indexed and the broaches returned through the tubes 67 whereupon they are gripped by the puller-head and completely withdrawn from the tubes. The heads are then again indexed to bring each work-piece to its next broaching position and the puller-head actuated to return the broaches to the broaching-head. When the puller-head is thus returned the caps 98a move the bushings 97 so that they seal the openings 94, this position being maintained during broaching. Cutting oil is supplied by pipe 103, annular channel 104, and ports 105, 106 to the work pieces and thence through the spindles 30 to the bores 90. When a work piece is removed the centre 52 moves forward and shuts off the oil supply. The lubricant supply is also cut off when the puller head is moved away from the tail part T.