US2119295A - Machine for generating gears - Google Patents

Description

May 31, 1938. H. SCHICHT 2,119,295

MACHINE FOR GENERATING GEARS Filed July 18, 1936 4 Sheets-Sheet 1 I m ha/ ,4fforneys M y 31,1938. H.sH|HT 2,119,295

MACHINE FOR GENERATING GEARS Filed July 18, 1936 4 Sheets-Sheet 2 m -m 3 IIIIIIII/ 2 I li s ts WWW Affarneys 4 Sheets-Sheet 3 H. SCHICHT MACHINE FOR GENERATING GEARS Filed July 18, 1936 llwenfor: Heinrich cscilz'cili AWW wgug May 31, 1938. H. sci-"cur 2,119,295

MACHINE FOR GENERATING GEARS Filed July 18, 1936 I 4 Sheets-Sheei 4 Afiorneys Patented May 31, 1938 PATENT OFFICE 2,119,295 MACHDIE FOR GENERATING GEARS Heinrich Schicht, Huckeswagen, Germany, assignor to firm: W. Ferd. Klingelnberg Siihne, Remscheid-Berghausen, Germany Application July 18, 1936, Serial No. 91,416

In Germany February 16, 1934 9 Claims.

This invention relates to a method of and a machine for generating gears, and more particularly gears having longitudinally curved teeth.

In certain known processes of manufacturing bevel gears, the teeth are cut by spiral or helicoidal cutters, as the tool and work are caused to roll upon each other, and the tool is swung about the center of the imaginary crown gear meshing with the gear being cut. In such processes, the number of tangential cuts which can be taken is limited to the cuttingteeth engaged in the milling process, and teeth having faces of excess width are generated by the tangential cuts, and must be polished in order that they may run smoothly. This excess width necessitates a prolonging of the lapping operation in the case of hardened gears.

The object of the present invention is to avoid the disadvantages of the prior processes and to materially reduce the manufacturing time. Briefly stated, the improved process consists in subjecting the cutting tool to an additional rectilinear displacement in the plane of the crown gear, without changing the inclination of the tool axis with respect to the crown gear plane, as the cutting tool and the work roll upon each other, and the tool is swung about the crown gear center. The cutting tool cuts a width of. tooth which is in excess of the distance corresponding to the length of the tooth, and prior art disadvantages of using helicoidal cutters are done away with.

In view of this action, the cutter can be greatly reduced in length, and hence disc-shaped cutters can be employed. .Use of a disc-shaped tool which is swung round the center of the crown gear permits simple and most exact positioning and guiding of the tool during its cutting motion. is in strong contrast to known processes in which disc-shaped tools must be actuated by steel bands or by tooth segments, and in which the machine elements must be changed for each new gear ratio or bone angle so that a very large stock of generating rolling cones must be kept available. The prior art devices also failed to offer sufficient resistance to cutting pressure to attain any high degree of efficiency.

All of the prior art disadvantages are overcomev by the present invention. This invention will be understood when the following description is read in conjunction with the accompanying drawings in which:

Fig. 1 is a diagram showing a short, spiral cutter or cone grinding worm in the process of.

cutting curved teeth on a bevel gear;

Fig. 6;

Fig. 2 is a view similar to Fig. 1, but showing the cutting tool as a cylindrical worm;

Fig. 3 is a diagram showing a short or discshaped cutter in the process of cutting curved teeth on a bevel gear, the tool displacement being coincident with the line of contact between the tool and the crown gear plane;

Fig. 4 is a fragmental section showing the shape of the teeth of the tool in Fig. 3;

Fig. 5 is a view similar to Fig. 3, but with the direction of tool displacement inclined with respect to the line of contact between the tool and the crown gear plane;.

Fig. 6 is a longitudinal section, partly diagram-. matic, through a milling machine suitable for use in producing gears according to the method of the present invention;

Fig. 7 is a fragmentary sectional view of the dividing head used with the machine shown in Fig. 8 is a fragmentary sectional view of the compensating mechanism employed in the machine ofv Fig. 6 for maintaining correct relation between the work and the tool;

Fig. 9 is a face view of the cutting tool face plate showing a cylindrical cutter in the process of cutting a spur gear;

Fig. 10 is a view similar to Fig. 9 showing a conical cutting tool in the process of cutting a bevel gear; and

Fig. 11 is a view similar to Figs. 9 and 10, but showing a cylindrical cutting tool in the process of cutting curved teeth on a stationary spur gear.

Referring to Fig. 1 of the drawings, the reference character a represents a bevel gear having curvedteeth in the process of being cut by a conical cutter I. This cutter, as shown, is of such a size that its cone or mantle extends over a portion of the tooth width on the gear being cut and performs three movements as follows: 1. A cutting movement designated by arrow c and consisting of rotation of the cutter on its own axis in engagement with the work.

2. A rolling movement indicated by the arrow g and caused by swinging the cutter about the point 0 designating the center of the imaginary crown gear.

3. A rectilinear movement, designated by the double arrow d, in the direction of the line of contact between the cutter and the crown gear 5 plane on a straight, line touching a circle concentric with the crown gear center 0.

As shown by the double arrow 11 (Figs. 1, 2 and 3) the supplementary tool movement may be performed by the tool once while it makes a'complete trip around the crown gear center in engagement with the work, or it may reciprocate several times. The three tool movements also regulate the rotation of the work.

Rotation of the work is caused by engagement with the tool and from the swing of the tool about the center of the crown gear, this latter movement always producing the same direction of work rotation. In addition, the supplementary tool displacement during a change in its direction produces its effect. If. this latter displacement is in such a direction as to supplement the first two movements, it speeds up the rotation of the work, but if this displacement opposes the other two movements then the speed of rotation of the work is reduced. In the exterior limit position the outside diameter of the cutter must at least touch the outside diameter of the gear, or preferably, project over it. In the interior limit position, the inner diameter of. the cutter must touch the inner diameter of the gear or project over it slightly.

The supplementary tool displacement above mentioned has a marked advantage, in that a greater number of tangential cuts may be obtained in the direction of the tooth length, and caused by the edges of the cutting teeth continuously taking up different positions in the direction of the double arrow (1. The more often this displacement occurs, the more perfect is the tooth formation. Consequently, when practicing this method, one is not dependent upon the number of cutting edges on the tool. If it is desired to use a shorter cutter, a disk-shaped cutter of the type shown in Figs. 3, 4 and 5 may be employed.

When a disk-shaped tool is employed, the cutting must be carried out as a single step process, although the supplementary tool movement characterizing the new process remains the same. This movement is, however, increased so that the disk-shaped tool covers the whole tooth width and travels in the direction indicated by the arrow d in Figs. 3 and 5, at least between the limits designated A and C in Fig. 3.

In Fig. 3 the supplementary displacement of the tool is in the direction of its line of contact with the crown gear plane. In Fig. 5 this displacement is at an angle to the line of contact with the crown gear plane. By varying this angle a change in tooth curvature may be obtained. For example, in a process according to Fig. 3, a large spiral angle with a sharp curvature is desirable, in order to obtain suflicient covering with a small number of teeth and tooth widths. However, for large tooth widths and great pitch pressures a smaller spiral angle with a decrease in axial pressure is desirable. An example of this latter is given in Fig. 5.

A machine for generating gears according to the method above described, is illustrated in Fig. 6 of the drawings. In Fig. 6 reference character I designates the cutter mounted on a tool spindle land adapted to be driven by a motor 3 through suitable gearing which will be described later. The work 4 is carried on a work spindle 5 also driven by motor 3 over a bevel gear drive 6, 1 connected to main shaft 9.

The drive for producing rolling and generating motion of the cutter I in the ideal crown gear is transmitted from shaft 9 through spur gearing to a worm wheel H] on face plate cylinder II. This cylinder turns on the horizontal axis 9.

On the front face of cylinder ll adjacent the work, is a slideway 12 which can be rotated on a journal l3, the axis of this journal being eccentric and lying parallel to the central axis of the face-plate cylinder ll. Mounted in slideway I2 and guided therein is a carriage 14 which can be moved by means of a threaded spindle l5 connected with the machine drive. A tool support I6 is mounted on the carriage l4. This carriage makes it possible for the tool to perform the supplementary movement indicated by the double arrows d in Figs. 1 and 2, and which is characteristic of this invention.

The carriage I4 is displaced by a piston l1, operated by oil pressure from a pump of known type and controlled by a valve, also of known type. The number of up and down strokes of the piston I! can be regulated as desired, and is dependent upon the oil pressure and the cutting resistance oifered to the tool. As the reciprocating movement, already described, is controlling the rolling and generating movement, the piston l'l acts on a rack on the casing of a differential I8 on shaft I 9. Fixed on the casing of differential I8 is a spur gear 20 connected by change gears 2| and 22 with the rim, of gear wheel 23. Gear wheel 23 revolves around the face-plate cylinder II and transmits the turn of the differential over the spur gears 23-26, and bevel gears 21 and 28 to the threaded spindle l5. The supplementary turn of the work corresponding to this turn of the differential is transmitted along the parts of the drive 29, 30, 42, 43 and 45. If a short movement is desired when cutting, then the drive is transmitted from the differential worm shaft 3|, over change gears 32, 33, 34, 35, 36, bevel gears 31 and 38, spur gears 39 and 26 (Fig. 9) and bevel gears 22 to 28, to spindle l5. This spindle moves the carriage I4, on which the cutter revolving face-plate is'mounted.

When a disk-shaped cutter is used, any well known type of dividing head may be connected to the shaft 40 (Fig. 7) by a coupling 4|. This dividing head serves to index the work from tooth to tooth after each forward and return stroke of the cutter on the slideway I2.

The dividing head shown in Fig. '7 may be thrown into gear by disconnecting bevel gear 43 from shaft 42 and connecting gear 44 to shaft 40 by moving the coupling 4| from left to right in Fig. 7. In addition to this, the change gears 45, 46 and 41, Figs. 6 and '7, are dismounted, and

the dividing worm connected to shaft 40 by change gears 48 and 49, one only being shown in Fig. 8.

With the above substitutions made, rotation of shaft 5| caused by either differential 50 or l8 r is transmitted along the casing 52 (Fig. 7), pawl 53, dividing plate 54 to shaft 40, and then through change gears 48, 49 and worm gear 55, 56 (Fig. 8) to the work. With the supplementary reciprocating movement or displacement of the tool which is characteristic of this process, any twisting between the tool and work would make its appearance through the play of the gears. This twisting is equalized by means of the apparatus now to be described. maintain simultaneity of the reversing motion and of the play equalizing means, both motions are caused by hydraulic pistons acting simultaneously.

The mechanism for equalizing the gear play is illustrated in Fig. 8. The worm 55 of the dividing head worm gear 56 is mounted in bearings which are movable axially between adjustable limits. A casing 5'! serving as an oil cylinder encloses a piston 58. Piston 58 is rigidly con- In order to nected to the worm shaft and the piston is displaceable between one wall of easing as one limit, and the other cylinder wall 59 as the other limit. Wall 59 can be displaced by worms. The displacement limits are adjusted in such manner that when the turning is taken into account, the tool is again'in correct position with respect to the tooth spaces to be cut.

The slideway I2 is provided at one end with an oil cylinder 60 (Figs. 9, and 11) Piston 6|- riage I4 is at all times held tightly against the threads of the nut and it is impossible for play to be present in the threads.

The above-mentioned arrangement of the" face-plate cylinder, swinging table guide and rotating parts on the table for producing the movements of the tool and work which are characteristic of this process, make. it possible to give the tool any position desired for controlling its direction of movement in the crown gear plane, and to displace it forcibly in any desired direction over the face-plate. Therefore, not only is the machine suitable for practicing the method just described, but in addition, it can also be used as a universal machine for generating teeth on spur gears and bevel gears according to other known rolling generating processes.

To this end, two different changeable rotating parts 56 (Fig. 10) and l6a (Figs. 9 and 11) can be used as tool supports and fixed on carriage I4 for this purpose. The difference between these tool supports is that the one I6a is arranged for the reception of cylindrical cutters and the other l6 of cutters having conical or curved conical pitch surfaces.

The two changeable tool supports can, if desired; be equipped with grinding wheels instead of cutters, for carrying out the process above described.

The work support 62 (Fig. 6) on which the work 4 is fixed to shaft 5, can be displaced vertispur gears, worms and numerous other similar work.

When spiral bevel gears are to be cut by cutters of the type shown in Fig. 1, the bevel gear (Figs. 6 and 10) are each under continuous equal pressures during the working process. Piston 61 forces the cutter case against the block gauges 6B or against stop spindle 69. The piston 6! in slideway l2, presses the nut in carriage M against the guide spindle I5 in order to compensate or eliminate play. At each changein direction of tool movement the piston H in differential l8'is This The slideway I2 is adjusted on the reversed in order to give the cutter a movement inthe direction of the arrow (1. Piston 58 (Fig. 8) performs this same movement to correct the rotation of the dividing wheel.

When a cylindrical cutter is to be employed to form the teeth of bevel gears, as shown in Fig. 2. the hydraulic pistons are driven in the same manner as for the tooth formation disclosed in Fig. 1. The only change required between the two methods is that for cone cutters the head l6 takes the form of Fig. 10, while for cylindrical cutters the head I6a has the form shown in Figs. 9 and 11.

When teeth are being cutwith disk-shaped cutters, as shown in Figs. 3 and 5, the slideway I2 is fixed in position on the face-plate cylinder II and this position depends upon the curvature of the teeth which are being out. Cylinder H ondifferential l8, and cylinders 60 and 61 are connected together by means of the regulating valve referred to above. A continuouspressure is applied equally to both cylinders 66 and 67 during the whole tooth forming process. Oil pressure from pipe lll acts on cylinder 61 to forcethe tool spindle H and cam 12 continuously against worm spindle 69. This spindle can be adjusted by means of worm l3 and the block gauges 68 to regulate the depth of the teeth to be cut.

The oil pressure control valve is operated in accordance with the movement of carriage M. When the cutter has completed a tooth traverse in one direction, the 'oil supply to cylinder H is reversed and causes a reversal in the direction of cutter movement. The dividing device is also connected to the oil supply so that the hydraulic motor 14 is under continuouspressure in one direction Mechanism is also provided in connection with the regulating valve so as to control piston 58 and, at each stroke of the tool, correct any discrepancy in position between the tool and work and caused byplay in the gearing.

When a spiral cutter is to be used to generate spur gears, a cutter head of the type illustrated in Fig. 2 for use in forming bevel gears may be used, also the hydraulic pistons may be actuated in the same manner as when generating bevel gears. However, the work support 65 is swung about the axis 66 in such a way that the axis of the work and the spindle l5 both lie parallel to the plane of face-plate ll l.

In performing this adjustment, change gear 116 on spindle I5 at table 65 (Fig. 6) is brought into mesh with a change gear on shaft ll Spindle 75 then serves to generate the feed motion in the direction of the work axis, as is usual in processes of generating teeth on spur gears. With such a connection the shaft TI is driven through gearing connecting it to shaft 18. Fixed on this worm shaft '18 is a coupling so arranged that worm 19 can be coupled to actuate the face-plate cylinder H or tocause the gear 80 to drive the shaft 8|, together with spindle l5 and shaft 78. The work 4 can be driven and feeding movement imparted to the wheel in a direction along its axis by a connection which includes the differen-. tials which have already been described.

The forward and reverse strokes of piston H for displacing the tool on slideway l2 in the direction of double arrow at, is transmitted to the shaft 29 and then to the work through the second differential l8. The forward and reverse thrust of piston IT effects the rotation of the case, the differential l8 and the gear 20. Rotary motion of the gear 20 is transmitted to lead screw I! through gears2l, 22, 23 to 28, to move carriage I l on slideway I2 in direction of arrow d.

The machine is so designed that it is capable not only of generating spur gear teeth in the manner just described, in which the work is moved along its own axis-toward the tool, but it is also possible to guide the work tangentially to the tool. In this way, an additional advantage is obtained, namely, that each tooth on the tool takes up as many tangential positions as desired, as its tangential cutting edge moves in the direction of tool feed. Therefore, any desired number of tangential cuts can be made, with the resulting increase in the accuracy of the tooth flanks.

Fig. 11 of the drawings illustrate the execution of the process just described. The work support 65 (see Fig. 6) is rotated about the axis'66 until the work axis is parallel to the plane of faceplate ll. However, the method of Fig. 11 differs from that in Fig. 9 in that no feeding motion is imparted to the work support in Fig. 11.

The slideway I2 can be adjusted so that the tool moves tangentially along the dividing cylinder of the work, by rotating the face-plate II. The angle of inclination of the teeth to be generated is adjusted by swinging the cutter head inward. As shown in Fig. 11, the cutter is adjusted to produce tangential cuts, and the length of the cutter is so chosen that it extends over the whole tooth width during the feeding movement, thus performing an additional back and forth movement. Thus it becomes possible to derive the tool movement for tool carriage l4 from a transmission operating solely on differential gear 50 and independently of differential gear [8. In Fig. 11, this tool movement is transmitted from differential worm shaft 3| over change gears 32 to 36, bevel gears 31, 38, spur gears 39, 24 to 26, bevel gears 21, 28 and along spindle l6 to the tool carriage l4.

It is obvious that the machine can be arranged to carry out the tangential process in which the tool is fixed and the work is moved along the tool.

When bevel gear teeth are to be produced with longitudinally crowned teeth in which the crown is obtained by altering the milling depth, use may be made of a revolving cam 12 which serves as an eccentric. This cam is fixed to the housing II and is revolved back and forth through a definite angle of oscillation through change gears which cause the tool to be displaced in the direction of arrow d (Figs. 1, 2, 3and 5). The entire housing H is, consequently, moved back and forth in the direction of tooth depth. The adjustment and motion of the oscillating cam 12 has the following effect:

In position A of Fig. 3, the tool I is slightly deeper than when at full tooth depth (full tool depth=2.16 modul). the tool is drawn out of the tooth space until it takes the position B at normal tooth depth. In traveling from B to C, the tool again penetrates deeper into the tooth space until it reaches the same depth as in position A. On the return travel from C to A, this same change in tooth depth occurs again.

The width between teeth changes with the change in tooth depth, sothat the tooth spaces become narrower in the center than at the ends. Consequently, when curved teeth are cut, the convex tooth flank has a sharper curvature than the concave tooth flank. The amount and rate of withdrawal and approach can be determined In traveling to position B, I

in accordance with the point at which it is desired to crown the tooth.

Use of the machine above described assures absolute identity between pieces of work being cut. The hydraulic arrangement 61 presses the work spindle housing ll against a stop which is adjustable by means of the block gauges 68 and the screw 69. This adjustment of the depth of cut by means of block gauges possesses marked advantages over prior art adjustments by threaded spindle and scale. The adjustment can now be carried out with accuracy by unskilled'workmen and once the gauges are set, no further attention need be given to the adjustment.

What is claimed is:

1. A milling machine comprising a bed; an adjustable work support on said bed; atool support on said bed; a main driving means for causing rotation of said work and tool supports; a first hydraulic means for imparting a supplementary rectilinear movement to said tool support; and a second hydraulic means connected to both said tool and work supports for eliminating lost motion therebetween.

2. A milling machine comprising a frame; an

adjustable work support-on said frame; means for rotating said support about the axis of the work gear; a face plate rotatable about the center of the imaginary face gear meshing with the gear being out, said face plate having a slide thereon; a carriage on said slide; a rotatable tool support on said carriage; a tool on said tool support; means for causing reciprocatory movement of said carriage in a direction parallel to the cut ting plane of the tool and in a direction substantially parallel to the axis of the tool; means for rotating the face plate and the tool thereon; and means for causing the reciprocatory movement of said carriage to take place in timed relation to the movement of the tool and work supports.

3, A milling machine comprising a frame; an adjustable work support on said frame; means for rotating said support about the axis of the work gear; a face plate rotatable about the axis of the imaginary face gear meshing'with the gear being cut; a rotatable tool support on said face plate, said support having a tool thereon; means for causing reciprocatory movement of said tool support in a direction parallel to the cutting plane of the tool and in a direction substantially parallel to the axis of the tool; means for rotating the face plate and the tool thereon; and means for causing the reciprocatory movement of the tool support to take place in timed relation to the movement of the tool and work supports.

4; A milling machine comprising a frame; an adjustable work support on said frame; means for rotating said support about the axis of the work gear; a face plate rotatable about the center of the imaginary face gear meshing with the gear being cut, said face plate having a slide thereon; a carriage on said slide; a rotatable tool support on said carriage; a tool on said tool support; means comprising an hydraulic piston and transmission gearing for causing reciprocatory movement of said carriage in a direction parallel to the cutting plane of the tool and substantially parallel to the axis of the tool; means for rotating the face plate and the tool thereon; and

'means for causing the reciprocatory movement of said carriage to take place in timed relation to the movement of the tool and work supports.

5. A milling machine comprising a frame; an

adjustable work support on said frame;'means for rotating said support about the axis of the work gear; a face plate rotatable about the axis of the imaginary face gear meshing with the gear being cut; a rotatable tool support on said face plate, said support having a tool thereon; means for causing reciprocatory movement of said tool support in a direction parallel to the cutting plane of the tool and substantially parallel to the axis of the tool; means for rotating the face plate and the tool thereon; and means interconnected withi the means for rotating the face plate and work supports for causing the reciprocatory movement of the tool support to take place in timed relation to the movement of the tool and work supports.

6. A milling machine comprising a frame; an adjustable work support on said frame; means for rotating said support about the axis of the work gear; a face plate rotatable about the center of the imaginary face gear meshing with the gear being out, said face plate having a slide thereon; a carriage on said slide; a rotatable tool support on said carriage; a tool on said tool support; means for causing reciprocatory movement of said carriage in a direction parallel to the cuttingplane of the tool and in a direction substantially parallel to the axis of the tool; means for rotating the-face plate and the tool thereon; means for causing the reciprocatory movement of said carriage to take place in timed relation to the movement of the tool and work supports; a cam; and means for actuating said cam in accordance with said reciprocatory movement for controlling the depth of cut of said tool.

7. A milling machine comprising a frame; a Work support on said frame, said support being rotatable about the axis of the work gear; a face plate; means for rotating said face plate about the center of the imaginary face gear meshing with the gear being cut; a carriage on said face plate; a rotatable tool support on said carriage;

a tool on said support; means effective during a milling operation of the machine to impart reciprocatory movement to said carriage in a direction substantially parallel to the axis of the tool and parallel to the cutting plane of the tool in timed relation to the movement of said face plate to produce spiral bevel gears; and means for locking said face plate to cause tangential movement of the carriage and tool during a milling operation, whereby the machine may produce spur gears.

8. A milling machine comprising a frame; a work support on said frame; said support being rotatable about the axis of the work gear; a face plate; means for rotating said face plate about the center of the imaginary face gear meshing with the gear being cut; a carriage on said face plate; a rotatable tool support on said carriage; a tool on said support; means effective during a milling operation of the machine to impart reciprocatory movement to said carriage in timed relation to the movement of said face plate, said rmovement being 'in a. direction substantially parallel to the axis of the tool and parallel to its cutting plane; a dividing mechanism operatively connected with said tool support; and means for connecting and disconnecting said dividing mechanism and said tool support.

9. A milling machine comprising a frame; a work support on said frame; said support being rotatable about the axis of the work gear; a face plate; means for rotating said face plate about the center of the imaginary face gear meshing with the gear being cut; a carriage on said face plate; a rotatable tool support on said carriage; a tool on said support; means effective during a milling operation of the machine to impart reciprocatory movement to said carriage in a direction parallel to the cutting plane of the tool and substantially parallel to the axis of the tool in timed relation to the movement of said face plate; a housing for the tool support; hydraulic means for displacing said housing against said tool support; a rotatable cam between said housing and said displacing means, said cam being effective to change the depth of cut during a cutting operation without stopping the machine; and means comprising at least one block gauge for gauging the total depth of cut made by the machine.

HEINRICH SCHICHT.

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