GB1004999A - Improvements relating to the grinding or shaping of the teeth of multi-tooth cutters - Google Patents

Abstract

<PICT:1004999/C6-C7/1> <PICT:1004999/C6-C7/2> <PICT:1004999/C6-C7/3> A machine for electrolytically shaping the teeth of multi-toothed cutting tools comprises an indexable arbor 130, Fig. 19, for supporting the cutting tool and a rotatable electrode 585 carried by an hydraulically-reciprocated ram 401 mounted in a frame 36 which is movable relatively to a table 14 under the control of a cam 340 in order to vary the vertical position of the electrode as the latter is reciprocated with the ram. The machine is hydraulically operated in an automatic cycle in which at appropriate periods in the reciprocation of the ram the frame 36 is swung about its pivot shaft 34 on the table 14 by the cam 340 to give the electrode the necessary movements to shape the faces 67211, 67811, Fig. 33, of the cutter tooth T. The cutter is centred and clamped on a table 132 at the upper end of the arbor 130 which is journalled in a housing 124 arranged to be adjustable vertically by screw-and-nut means 148 on a slide 114 adjustable horizontally on the front of the main frame 10. The arbor is indexed to bring successive teeth into grinding position by arranging for either of two gears, according to the desired direction of indexing, to effect drive of a gear 160 at the lower end of the arbor. The two gears are selectively clutchable on a shaft driven from hydraulic drive means appropriately controlled from a reciprocating valve 500, Fig. 30, in the control circuit ; in one setting of this valve the arbor is indexed one tooth, and, in the other, is operated in reverse to force the indexed cutter against a stop. The electrode 585, which may comprise powdered metal and diamond particles sintered together, has its shaft 605 insulatedly journalled in the head 590 of the ram and rotated through a belt-and-pulley drive and connected shafts 612, 635 from a motor 461 carried by the inner end of the ram. Electrolyte, such as water fortified with sodium acetate, citrate or tartrate, is delivered in a stream over that portion of the cutter being shaped ; current is supplied to the electrode 585 through the shafts 605, 612 and a copper ring 639 on the shaft 635 contacted by brushes 650, the circuit being continued through the electrolyte, arbor and brushes 159 contacting a bronze ring on the latter. Reciprocation of the ram is effected by a hydraulically-operated <PICT:1004999/C6-C7/4> <PICT:1004999/C6-C7/5> <PICT:1004999/C6-C7/6> <PICT:1004999/C6-C7/7> piston 685, and in a cylinder 921, metering passages in both the cylinder and piston are so arranged that the forward stroke of the ram consists of successive fast, slow and fast stages, and the return stroke of successive slow and fast stages. To form the two faces 67211, 67811, Fig. 33, on each tooth the ram is provided on its underside with a follower 3271 arranged at the desired periods in the travel of the ram to coact with two inclined faces 672, 678, Fig. 15, on the cam plate 340 and so rock the ram about the shaft 34, and give the electrode the necessary components of vertical movement. Each operation upon a cutter tooth results in a corresponding reciprocation in its cylinder 710, Fig. 27, of a rack plunger 712 by fluid supplied under the control of the reciprocating valve 550 controlling the ram, each reciprocation of the plunger causing a corresponding angular movement of a gear 748 and, through a one-way clutch connection, the shaft 755 on which the gear is mounted. At the start of an operation, the shaft 755 is set to a predetermined angular position and it is arranged that, after a number of reciprocations of the plunger corresponding to the number of teeth to be operated upon, the shaft has been rotated to an extent sufficient to bring fluid supply and discharge passages into register for the purpose of actuating a piston in its cylinder 798, Fig. 30, to open a switch 794 in the circuit of the motor 461 and motor 198 driving the pump 196 of the hydraulic circuit. The number of reciprocations of the plunger before this happens is governed by the setting of a stop 729 which determines the stroke of the plunger and is carried by an adjustable screwthreaded sleeve 724 graduated in numbers of teeth to be shaped. The switch-actuating piston is advanced against a spring and contains a metering passage providing for retraction of the piston and closing of the swtch after a predetermined interval.