Patent GB-414653-A (GB)
Title: Improvements in the manufacture of spur and bevel wheels
IPC: B23F5/12
Filed: 1933-02-03
Abstract: 414,653. Gear cutting. SAMEK, F. K., Miedzylesie, near Warsaw. Feb. 3, 1933, No. 3417. [Class 83 (iii).] A universal gear cutting machine for generating straight helical or curved teeth on spur or bevel gears comprises a rotatable blank holder 6 associated with lever mechanism for controlling the rolling generating movement of the blank and the blank holder is mounted on a swivel carriage 3 which may swing about a vertical axis OO, passing through the cone apex of a bevel gear blank and is mounted on a transverse carriage 2 which is operated to give the tangential generating movement when cutting spur gears, the lever mechanism being so arranged that when the transverse carriage is fixed, actuation of the lever turns the swivel carriage, and when the swivel carriage is fixed to the transverse carriage, the said actuation operates the transverse carriage without turning the blank holder. The cutting slide support is angularly adjustable so that the pivot of the roller may be arranged to travel in a plane tangential to the root cone or root cylinder of the blank. As shown in Fig. 4, the cutting edge S may be arranged at right angles to an imaginary surface T which rolls on the base circle K to generate an involute (describing generating) or the cutting edge S may, as shown on the right of the figure, be arranged at an angle of 15‹ to a surface T, which rolls on the pitch circle Kt (moulding generating). Either process is applicable for cutting spur gears either straight or curved, but for cutting double helical bevel gears only the first process produces accurate teeth. In Fig. 5 a bevel gear blank K is mounted on a spindle driven by worm gearing 7 and is carried in a cradle 5 which may be adjusted so that the generator OB of the blank pitch cone is parallel to the surface of the carriage 3 or may be set as shown in Fig. 11 for cutting spur gears. The cradle support 4 moves longitudinally on the slide 3 to bring the blank cone apex into the axis OO, this setting being determined by a gauge point T carried by a rod 23. The transverse slide 2 is itself mounted on a swivelling carriage 1. The cutter slide support p is adjusted to the dedendum angle alpha of the blank. After adjustment of a bevel gear the carriages 1, 2 are secured together and to the frame and the members 3, 4, and 5 are secured together. The gear is then generated by the rotation of the blank on its axis in unison with the swinging movement of the blank by rotation around the axis OO. In cutting straight teeth, a cutter N, Fig. 7, may be arranged so that it cuts one side of the tooth a, Fig. 8, on the forward stroke and the other side a', on the return stroke, being rotated through 180‹ at each reversal. This rotation is effected by a cam 28, Fig. 7, which acts through a rack 26 on a spur wheel 25 keyed to the cutter spindle. For cutting double helical teeth, the cam 28 may be arranged to maintain the tool at the correct clearance angle throughout the stroke. The cutter slide 39 is driven from a belt pulley 35 through gears 36, 37 and crank 38 and the cam 28 is also driven from this belt pulley through gears 33, 34 and spur gearing 30. The rotational axis of the cutter passes through the point X so that the blank must be rotated alternately through the distances t1, t2 between successive cuts where t1+t2 is the pitch. For this purpose a bevel wheel 43 driven from the pulley 35, Fig. 5, drives a shaft 45 carrying a splined friction clutch member 46 coacting with a clutch member 47 keyed on a shaft 53 and provided with fixed and adjustable lugs 50, 51, respectively, the spacing being proportional, Fig. 9, to the magnitudes t1, t2. A loose worm wheel 54 is bored to receive slidably a pin 55 secured to a yoke 58. On reversal of the stroke of the cutter a cam 57 on a crank shaft 56 compresses the spring 58a and actuates yoke 58 to withdraw the pin 55, thus engaging the clutch and causing member 47 to rotate by the amount permitted by the lugs 50, 51. The rotation of the shaft 53 is transmitted to the blank by gears 59, 60, shaft 61, bevel gears 20, 21 and worm gearing 7. In order to impart the generating feed to the blank, the crankshaft 56 actuates ratchet mechanism 65 to rotate the worm wheel 54 and superpose the generating feed on the above described spacing movement. The worm shaft 66 is connected to a screw 11 which, through a nut 12 operates a lever D pivoted at 71 and operating a block 14 secured to a strip ledge 15 connected by flexible band mechanism to the carriage 3 which is thus rotated around the axis OO to impart the required crownwheel movement to the blank in unison with the rotation thereof. The setting 'distance g1 of the block 14 from the pivot 71 is calculated from the dimensions of the blank and the change gearing 59, 60. For cutting helicoidal bevel gears, the blank is displaced so that the cutter describes the path A1, Fig. 6a, instead of AA. For cutting teeth of the double helical type, as shown in Fig. 10, the cutter may be moved transversely during its cut by a crank 73 connected by a rod 74 to the transverse cutter carriage 72. The crank 73 rotates four times as fast as the crank 38 so that it makes a complete revolution while the cutter moves through the effective central part of its travel (corresponding to a crank rotation of 90‹). The cutter is set to the correct depth by means of the carriage 76. For cutting helical teeth on spur gears, the carriage 1 is turned on its pivot to the desired helical angle. When rotary cutters are used for cutting curved teeth, such cutters operate on the describing generating principle and are maintained perpendicular to the imaginary surface rolling on the base cylinder or basic cone. The continuous indexing process is employed, the cutter N rotating through 120‹, Fig. 13, while the blank rotates through one pitch to produce the resultant curve NN4. Three cutters arranged at 120‹ around the head will thus cut all the teeth on the blank on one side, while three other cutters arranged at 120‹ and spaced from the first cutters by an amount dependent on the relative dimensions p, p 1 and p 1, p2 will cut the other side of the teeth. The usual generating motions are superposed on the above described rotary motions. A similar method, Fig. 15, may be used for cutting bevel gears, six cutters for the opposite tooth faces. For cutting teeth of the double helical type, the blank or cutters being in this case given an additional oscillating movement by means of a crank such as 73, Fig. 7. In this case the cutters must be equispaced around the head, but alternate cutters are arranged at different distances from the axis in order to produce teeth of the required thickness at the base circle. In one form of cutter head alternate cutters N, N1, Fig. 19, are arranged on concentric discs 1, 2 which are relatively adjustable to vary the tooth thickness produced, the head being driven by worm gearing 8. In a modified form of cutter head, Fig. 21, for cutting double helical type teeth on spurs or bevels, the cutters are radially adjustable according to the face width of the gear to be cut. The cutters have their effective edges N, located in the axes of spindles 1 which are mounted in square bearing members radially adjustable by means of packing means 4 in recesses 2 of the main spindle 3. A central key 6 having three parallel alternating with three wedge faces may be moved axially to adjust alternate cutters for the tooth thickness p, P1 required on the work. The ends of the cutter spindle bear on a cam disc 9 which retracts the cutters during the idle part of their travel. A stationary drum 11 has a cam slot 12 engaged by crank arms connected through bevel gears 15, 16, to the cutter spindles so as to maintain the cutters at the correct cutting angle. The head is driven by worm gearing 18. The cam surface 9 is adjusted through 180‹ for cutting the mating gear by means of a crank arm 19 and pin 20. Fig. 22 shows the machine adapted for use with a rotary cutter head. In this case the shaft 45 transmits continuous motion to the blank through differential gearing, the additional generating movement being derived from a ratchet wheel 65. For cutting double helical type gears the cutter head is mounted on a slide which is reciprocated by a crank in a similar way to that shown in Fig. 5.