US3713315A

US3713315A - Cold rolling profiles on cylindrical workpieces

Info

Publication number: US3713315A
Application number: US00070377A
Authority: US
Inventors: A Meyer; O Wenger; O Maag
Original assignee: Maag Zahnrader und Maschinen AG
Current assignee: Maag Gear Wheel and Machine Co Ltd; Maag Zahnrader und Maschinen AG
Priority date: 1969-09-16
Filing date: 1970-09-08
Publication date: 1973-01-30
Anticipated expiration: 1990-01-30
Also published as: DE1946870A1; JPS5021155B1; DE1946870B2; GB1293412A; FR2061481A5; CH531386A

Abstract

In a method for cold rolling profiles on the circumference of a rotating cylindrical workpiece, using tool worms of appropriate profile, the worms performing generating motions corresponding to the profile required in successive part-rolling operations by being moved relative to the workpiece in a closed-circuit locus path having one axis which is in the direction of and smaller than the tooth depth, and which substantially smaller than another axis of said locus which is in the direction of tooth length or thickness, with each part-rolling operation being performed over the entire tooth facewidth while the tools are retained, over the workpiece width, in their dead center position which is a position on said locus innermost relative to the axis of the workpiece, the profile being preformed by progressive radial feed of the operating stroke of the tools and with a number of enveloping planes, and the profile being subsequently, finish-formed with a larger number of enveloping planes and with an unchanged inner dead center position of the tool worms.

Description

United States Patent [1 1 Meyer et a].

[111 3,713,315 Jan. 30, 1973 [541 COLD ROLLING PROFILES 0N CYLINDRICAL WORKPIECES [75] Inventors: Albert Meyer, Thalwil; Otto Wenger; Oskar Maag, both of Zurich, all of Switzerland [52] U.S. Cl. ..72/l00, 72/95, 72/104 [51] Int. Cl. ..B2lh 5/02 [58] Field of Search ..72/95, 100, 101, 102, 103,

[56] References Cited UNITED STATES PATENTS 2,991,672 7/l96l Meyer et al. ..72/l00 3,032,871 5/1962 Meyer et al.

3,159,062 l2/l964 Goodwill Inn/103 Primary Examiner-Lowell A. Larson Attorney-McGlew and Toren [57] ABSTRACT In a method for cold rolling profiles on the circumference of a rotating cylindrical workpiece, using too] worms of appropriate profile, the worms performing generating motions corresponding to the profile required in successive part-rolling operations by being moved relative to the workpiece in a closed-circuit locus path having one axis which is in the direction of and smaller than the tooth depth, and which substantially smaller than another axis of said locus which is in the direction of tooth length or thickness, with each part-rolling operation being performed over the entire tooth facewidth while the tools are retained, over the workpiece width, in their dead center position which is a position on said locus innermost relative to the axis of the workpiece, the profile being preformed by progressive radial feed of the operating stroke of the tools and with a number of enveloping planes, and the profile being subsequently, finish-formed with a larger number of enveloping planes and with an unchanged inner dead center position of the tool worms.

14 Claims, 13 Drawing Figures r Anzmmmaoms 3.113.315 gnininfi g3 R a INVENTORS I ALBERT MEYER 0170 w es:

OSKA

TTORNEYS PATENTEDMMOIBH 3.713.315

' sum 2 nr 7 1 FIG; 2'

INVENTORS ALBERT MEYER (m0 weueeR OSRAR MAM:

Pmmmmaman 3.713.315 sum 3 or? I INVENTORS ALBERT MEYER OTTO WENGER OSKAR M v I Waffle! 76m:

ATTORNEYS PATENTEDJM 30 I975 saw u or? INVENTORSI ALBERT mama OTTO WENGER OSJKA'R NAAG m wamom ATTORNEYS PAIENTEnmao me.

p 3.713.315 I SHEETBUF7 JNVE NTo RS ALBERT MEYER orro wauesa osxm HMS ATTORNEYS COLD ROLLING PROFILES ON CYLINDRICAL WORKPIECES The invention relates to a method for the cold rolling of a gear tooth profile on the circumference of a cylindrical work piece, and to a machine for performing the said method.

A known machine for the cold rolling of gearwheel teeth employs worm-shaped profiling tools having the reference profile, and being adapted to perform generating motions relative to the rotationally driven workpiece and in accordance with the profile to be generated, and performing successive part-rolling operations on the workpiece by being moved relative to the workpiece on a closed-circuit locus having one axis which is in the direction of and smaller than the tooth depth and which is substantially smaller than another axis of said locus which is in the direction of the tooth length or thickness. The tools move in an elliptiform path (the said closed-circuit locus) which has a minor axis and a major axis, the extremities of the minor axis being dead center positions, the inner dead center position being that which is nearer the axis of the workpiece. The inner dead center position is defined by the tooth root of the gear which is to be generated. During each part rolling operation the tool is first moved relative to the workpiece in the position which is radially the lowest with respect to the workpiece, and at the end of its stroke, which is axial relative to the workpiece the tool is lifted from the rolled gap, to continue in the closed-circuit locus, the said tool being gradually fed axially forward, between successive locus circuits, during the continuous part-rolling operations of tools. In each part-rolling the profiling tools will first finishform the profile already prerolled and at the end of their motion, while the tools are radially retracted, an axially adjoining part of the profile will be preformed. In order to obtain the desired quality of gearing, finish-forming of the tooth with the reference profile must be performed with a plurality of; enveloping planes, that is, the imaginary planes swept by the flanks of the tool worm teeth, producing (in the preforming stage) visible flats on the gear teeth; however,-a smaller number of enveloping planes would be sufficient for the preforming of the tooth. However, since preforming of one portion of the profile and finish-forming of another portion of the profile have to be performed in one and the same operation, it follows that the speed at which the profile is produced is defined by the part rolling operations required for finish forming.

It is the object of the invention to provide an improved method and apparatus by means of which the manufacturing speed in cold rolling of gearwheel profiles on the circumference of a cylindrical workpiece can be substantially increased.

According to the invention, the rolling is effected in a plurality of part-rolling operations, each part-rolling operation, is performed over theentire tooth facewidth with the tool worms being retained, at least over the tooth facewidth, in an inner dead center position, as hereinbefore defined,'in said locus, said plurality of operations including preforming the tooth profilein a number of enveloping planes by progressive feed toward the workpiece of the operating stroke of the tool worms in the radial direction of the tool worm and workpiece between successive complete movements in said closed-circuit locus, and finish-forming said profile in a larger number of enveloping planes, each envelop- -ing plane being accomplished with the tool worms retained in a said inner dead center position.

Since preforming and finish-forming take place successively it is possible for the feed motion for preforming to be executed without reference to the finish-forming of the profile. In selecting the material volume to be deformed in each rolling stroke during the preforming operation it is merely necessary for the appropriate choice to be made in accordance with the material to be deformed. A small number of enveloping planes are sufficient for rough preforming while the required accuracy of gearing is obtained in finish-forming with a larger number of enveloping planes.

it is particularly advantageous if each part-rolling operation is always performed with the same position of the profile of the tool worms relative to the workpiece so that the tooth profile is formed over its entire length with the same enveloping planes, each enveloping plane having the same position relative to the tooth gap being formed.

In an appropriate embodiment, preforming is performed with'between 1.5 and 2.5, but preferably with 2, part-rolling operations for each rotation of the tool worms while the ratio of part-rolling operations for each tool worm rotation selected for finish-forming is smaller or larger by a small amount, said ratio being exactly a figure no smaller than a high multiple of the number of teeth on the workpiece. If the profile is produced by means of two part-rolling operations for each rotation of the tool worms, the tooth profile will be preformed with three enveloping planes which are generally sufficient to closely approach the involute tooth profile. Finish-forming is then performed with a larger number of enveloping planes.

A machine for carrying out the said method, provided with tool worms which are adjustable at an angle and are supported in tool supports which are radially movable and axially reciprocable relative to the workpiece, and having a rotary drive for the tool worm and for the workpiece to impart to both the tool worms and the workpiece a relative generating motion which corresponds to the profile to be generated, is characterized in that the tool supports can be reciprocated exclusively in the direction which is radial relative to the workpiece axis and that the workpiece is supported in a work slide which can be reciprocated in parallel to the workpiece axis over more than the facewidth of thegear tooth being formed on the workpiece and that the rotational drive of the workpiece spindle is provided through an interchangeable lead bush to produce the desired rotation of the workpiece.

To ensure that the tool worm and the workpiece retain their relative position to each other when each part-rolling operation is performed, a first angularly adjustable slotted link is preferably mounted on the work slide and ,is adapted, duringeach stroke of the work slide, to axially displace a driving wormfor imparting rotation to the workpiece in order to counteract the inherent generating action of the workpiece during each part-rolling motion, a second angularly-adjustable slotted link being provided to axially displace the tool worms during each stroke of the work slide in order to worms during each part-rolling motion.

During the part-rolling motion, the axial stroke of the workpiece should be performed at a constant velocity which should correspond to the rolling velocity of the tool worms so that wear thereof is minimized. In the machine according ,to the invention this problem is solved in that a crank with a crank rocker, a connecting rod and a two-armed lever are provided for. reciprocating the work slide and are so disposed that the sinusoidal oscillation of the rocker crank is converted into an axial reciprocation of the work slide so that the work slide moves at constant velocity.

The method according to the invention, and a machine-for performing the method, are disclosed in the following description of an embodiment of a machine for the cold rolling of gear profiles, and shown in the accompanying drawings, wherein:

FIG. 1 is a vertical section along the workpiece axis and on the line 1--1 of FIG. 2;

FIG. 2 is a vertical section on the line 11-11 of FIG. 1, only one tool support with its drive being shown;

FIG. 3 is a part end elevation, looking in the direction of arrow 111 of FIG. 2;

FIG. 4 is a horizontal section along the line of IV-IV of FIG. 5, through a workpiece and tool worms during the; finish-forming of the profile in a cold rolling of a straight-tooth spur gear;

FIG. 5 is a vertical. section along the line Y-Y of FIG. 4 during the finish forming of a workpiece having an even number of teeth;

FIG. 6 is a vertical section similar to FIG. 5 during the finish-forming of a workpiece having an odd number of teeth;

FIG. 7 shows the path of a tool worm in relation to a workpiece assumed to be stationary when the tool worm forms the tooth root;

FIGS. 8 and 9 show the conditions of the tool worm relative to the workpiece, the ratio of the number of strokes of the workpiece for each tool worm rotation being K 2;

FIG. 10 shows an enlarged cross-section through a tooth of the workpiece; I

FIG. 11 is a plan view of the workpiece and tool worms during the cold rolling of a helical gear;

FIG. l2-is a view corresponding to FIG. 7 but showing the cold rolling of teeth with longitudinal crowning; and

FIG. 13 is a view corresponding to FIG. 12, showing the simultaneouscold rolling of two gearwheels with longitudinally-crowned teeth.

In the machine illustrated in FIG. 1 to 3 for cold rolling helical gear on the circumference of a cylindrical workpiece, the said cylindrical workpiece 1 is retained, as shown in FIG. 1, atone of its ends by means of a clamping device 2 of a work spindle 3 journaled in a spindle-bearing pedestal 4 at the end, the left-hand end in FIG. 1, of a yoke-shaped work slide 5. At its other end the workpiece 1 is supported in the work slide 5 by means ofa work holder 6 having a mandrel 7. The work slide 5 is slidably guided by V-shaped guide surfaces 8 thereon sliding in corresponding guide surfaces 9 in a machine frame 10, said guide surfaces 8 being disposed on both sides of the workpiece and extending in parallel to the axis X thereof.

A lead bush 11, having helical guide grooves 12 of a lead approximately equal to the leadof the gear tooth helix, is flange-mounted on the end of 'the work spindle 3 remote from the workpiece. Sliding blocks 13, disposed in the interior of a driver collar 14, co-operate with the guide grooves 12, the drive collar 14' being mounted on the end face of the hollow boss 15 of a wormwheel 16 which is immovable axially but is rotatably journalled in the machine frame 10. By virtue of this arrangement, a reciprocating motion of the work slide 5 imparts to the workpiece a rotating motion cor responding to the desired helix angle of the profile which is to be generated. The lead'bush 11 together with the associated driver collar 14 is interchangeable.

The work slide 5 is causedto move axially of the workpiece I by a crank rocker 20 through a doublearmed lever 18, hinged on said work slide by means of a bolt 17, and a connecting rod 19. The crank rocker 20 is caused to reciprocate, on an axle bolt 21 supported in theframe 10, by a crank 22 (FIG. 2) the crank pin 23 of which carries a sliding block 24 which is guided in a longitudinal guide 25 in the crank rocker 20. The crank 22 is disposed at one end of a shaft 26 which is driven from a main shaft 29 of the machine through a gearwheel pair 27, 28, the said main shaft in turn receiving its drive from a motor 31 through a belt 30. The sinusoidal oscillation of the crank rocker 20 obtained from the crank 22 is converted into an axial reciprocating motion of the work slide 5 by an appropriate choice of the dimensions of the doublearmed lever 18, the connecting rod 19 and the crank rocker 20 whereby the motion of the work slide 5 to the right'(FIG. l) is extended so as to be performed practically at constant velocity. Accordingly, the workpiece 1 is moved axially practically at constant velocity during its motion to the right during which, as will be described later, partial rolling operations are performed thereon.

The double-armed lever 18 contains a guide slot 32 in which a slotted link 34 is guided, said slotted link accommodating a pivot pin 33. The pivot pin 33 is mounted on a bracket 35 which slides in a guide 36 on the frame 10 in a direction which is radial relative to the workpiece axis X, said bracket being adjustable by means of a spindle 37 and a worm drive 38 so that displacement of the pivoting pin 33 of the double-armed lever 18 enables the length and therefore the velocity of the axial motion of the work slide to be adjusted.

The profiling tools 40 take the form of worms (hereinafter referred to as tool worms) of which the normal section through the threads has the basic rack profile of the gear being rolled. In the illustrated machine, and as shown inv FIG. 4, two tool worms are provided and are disposed diametrically opposite each other, FIG. -2 showing only one of the tool worms 40 together with its drive.

The trunnions 41 of a tool worm 40 are rotatably supported in a toolhead 42. The tool head is supported by means of ,a circular guide 43 on a tool carrier 44 so as to be angularly adjustable about an axis Y which in tersects the workpiece axis and the axis of the tool worm 40 at right angles. For'the sake of simplicity, the tool head 42 in FIG. 2 is shown so adjusted that the axis of the tool worm 40 is disposed in the plane of the drawing. When straight teeth are cold rolled, the axis of the tool worm 40 will of course be inclined relative to the said plane atan angle similar to the pitch angle of the screw thread of the tool worm.

The tool carrier 44 is guided in a guide 45 of the machine frame along the said axis Y. An annular piston 48, constantly biased, by means of one of the branches of an oil distribution network 49 from a pressure source 50, in the direction of lift-off of the tool worm from the workpiece 1, is provided on a rearward extension 46, of smaller diameter, of the tool carrier 44, the extension 46 being guided in a bore 47 in the machine frame.

The rearward extension 46 of the tool carrier 44 extends through an opening 51 in a wedge 52 whose rear inclined wedge surface 53 is supported on a correspondingly inclined guide surface 54 in the machine frame, and whose front surface 55 is disposed at right angles to the axis Y and bears on the end face of a nut 56 for the feed of the tool worm 40, the said nut cooperating with screwthreading 57 on the external surface of a shoulder 58 on the rearward extension 46 of the tool carrier 44. The external circumference of the feed nut 56 is provided with worm wheel gearing 59 and can be rotated by means of a worm 60 from a control drive 61 for controlling the feed motion of the tool worm.

The oil pressure acting on the annular piston 48 ensures that the tool support 44 is constantly thrust by the feed nut56 against the wedge 52.

A piston 62, slidable in a cylinder bore 63, which is biased by the oil pressure of the coil pressure supply network 49, thrusts on the broad end of the wedge 52. The piston 62 retains the narrow end of the wedge 52 constantly in physical contact with a tappet 64 which in turn bears on a tappet roller 65', supported on'one arm 66 of a rocker lever, the other arm 67 of which cooperates through a cam'follower' roller 68 with a disc cam 69 which is mounted on a shaft 70 driven through a

bevel gear pair

71, 72 from the shaft 26.

Rotation of the disc cam 69' is accompanied by reciprocation of the wedge 52 and therefore by reciprocation of the tool carrier 44 with the tool head 42 and the tool worm 40. A connecting rod 73, hinged on the end of the arm 67 of the rocker lever 66, 67, and connected with a corresponding rocker lever of the reciprocating drive of the second tool worm, not shown ensures that the latter performs the same reciprocating motions.

Reciprocation of the workpiece l in the direction of the axis X and of the tool slide 40 in the direction of the axis Y both derive from the same shaft 26 and therefore are in synchronism with each other, and a relative generating motion, corresponding to the profile to be generated, is imparted to both the tool worm and the workpiece.

To perform the generatingmotion, the workpiece 1 is rotated by the main shaft 29. As can be seen in FIG. 1, the main shaft 29 drives, through a bevel drive 74, a

on a shaft 91. The control member of a dog clutch 92 is slidably mounted on the shaft 91 and can be optionally engaged with the dogs of a wormwheel 94, rotatable in the machine frame 10 by an adjusting worm 93, in order to couple the shaft 91 to the wormwheel 94, or may be engaged with dogs on the gearwheel in order to couple the shaft 91 to the gearwheel 90. In the latter case, a supplementary rotating motion is imparted to the planet gear cage 97 of the differential transmission 77, and therefore to the output shaft 98 of the said differential transmission, through the toothed belt drive 89, 90, the shaft 91, a change gear set and a pinion '96, while in the former case the planet gear cage 97 is retained motionless by means of the dog clutch 92. The partial change gear set 83 is defined by the desired number of teeth of the gearing to be produced on the circumference of the workpiece 1. The purpose of the two change gear sets 78 and 95 will be described subsequently.

To rotate the tool worms 40, a shaft 99, disposed in the drive line for the workpiece 1 and having mounted thereon the last wheel of the change gear transmission 78 and the gearwheel 79, is extended and drives, through a bevel drive 100, a shaft 101(FIG. 2) from which rotation of both tools is derived.

At each end the shaft 101 is provided with one pinion 102 of an axially slidable toothed belt drive 103 which in turn drives a shaft 104, journaled on the geometrical reduction shaft 75, a gear wheel pair 76, a differential transmission 77, a change gear set 78, gearwheels 79,

8 0, 81, a partial change gear set 83, a bevel drive 84 and a gearwheel pair 85, 86, a worm 87 which meshes with the wormwheel 16 which in turn drives the'work' axis Y in the tool support 44. The aforementioned shaft 104 in turn drives," through a bevel drive 105, a gearwheel 106 which meshes, by way of an intermediate wheel 107, with a gearwheel 108 provided on the lower trunnion 41 of a tool worm 40.

The reciprocating-drive for the work slide 5 and the reciprocating drive for the tool support 44'are matched to each other so that the tool worms 40 assume their inner dead center position relative to the workpiece axis X (FIGS. 1 and 2) when the work slide 5 is moved to the right in FIG. 1. This motion is therefore accompanied bythe part rolling motions of the tool 'worms 40 on the workpiece. It is desirable that the profile of the worm thread of each tool worm 40 retains its position unchanged during each part rolling operation relative to the tooth gap-to be rolled into the workpiece 1. To

this end the tendency, because of the rotation each tool worm 40, ofthe points of contact between the worm tooth flanks and the workpiece tooth flanks to wander off-center towards the left or right (FIGS. 5,6,8 and 9) and, as'a result, up or down between tooth tip and tooth root (which produces the action known as inherent generating action) is counteracted by axialdisplacement'of the tool worm and by movement of the workpiece slide 5'to the right.

Means for obtaining compensation of the tool worm rotation during the motion of the work slide 5 to the right will now be described.

The trunion 41 of the tool worm 40, at the top in FIG. 2, is journaled ina cylindrical bore 109, closed at one end, into which a branch of the oil pressure distribution network 49'extends, so that the end'face of the aforementioned trunnion 41' is constantly biased with oil pressure. Accordingly, the tool worm 40 is retained by means of a thrustbearing 110 in contact with a tappet l 11 whose rear end bears by way of a needle bearing 112, on a wedge 113 which'is adapted to reciprocated in the tool head 42.

The reciprocating motion of the wedge 113 of each of the two tool worms 40 is directly derived from the motion of the workslidc 5.To this end, the underside of the work slide is provided with an angularly-adjustable slotted link 114 with a slotted link guide 115 (FIG. 1). The slotted link114 may be adjusted angularly by an adjusting worm 116 and may be retained in the selected position by means of a locking nut 117. A sliding block 118 slides in the slotted link guide 115 and is supported on a pin 120 which extends upwardly from a slide 119. Theslide 119 is supported in a guide 121 in the machine frame 10 and extends at right angles to the workpiece axis X. Each end of the slide 119 has joined to it one end of a connecting rod 122 for the reciprocating drive of the wedges 113 of both tool worms 40. At its other end, each connecting rod 122 is hinged to one end of a double-armed lever 123, the other end of which lever is connected by a connecting rod 124 to one end of a double-armed lever 125 supported in the tool head 42, the connecting rod 124 extending along the axis Y of the tool carrier 144 and through a longitudinal bore in the shaft 104, the other end of the double-armed lever 125 being adapted to move the wedge 113. To prevent the reciprocating motion of the tool carrier 44 from affecting the reciprocating motion of the wedge 113,the double-armed lever 123 is supported, as shown in FIG. 3, on a pivoting pin 126 the ends of which are supported in double-armed levers 127 which are always of the same length as the lever 123, one of the ends of each lever 127 being pivotally mounted in bosses 128 on the rearward end of the tool carrier extension 46, while the other end of each double-lever 127 is guided, by a pivot pin having a head 129 providing a sliding block, in a slotted link guide 130 in the machine frame 10.

The apparatus by means of which the inherent generating action on the workpiece l is counteracted during the motion of the work slide 5 to the right, is disclosed in FIG. 1.

A slotted link 131, angularly adjustable by means of an adjusting screw 132 around a horizontal axis and at an angle relative to the workpiece axis X, is supported on a bracket n the spindle-bearing pedestal 4. A block 134, in which a pin on one end ofa double-armed lever 135 is journaled, slides in a guide 133 in the slotted link 131. The double-armed lever 135 pivots about an eccentric bearing pin 136 on a shaft 137 which is supported in a bracket 138 of the machine frame. The other end of the double-armed lever 135 is formed into a clevis 139 from which two trunnions extend inwardly into an annular groove 140 between two collars on the shaft of the worm 87 which is adapted to rotate the work spindle 3.

When the slotted link 131 is adjusted as illustrated in FIG. 1, a motion of the work slide to theright causes the double-armed lever 135 to be pivoted in the anticlockwise direction and the worm 87, constantly It is however not necessary for a separate lead bush 11 to be provided for any helix angle that may be encountered. A few lead bushes with graded pitch angles of the guide groove 12 are sufficient; for a desired and defined helix angle the lead bush 11 with the associated driver collar is fitted into the machine, the guide groove 12 having the pitch angle nearest to the desired helix angle. The desired helix angle may then be obtained by corresponding additional adjustment on the slotted link 131 which is set up so that the worm wheel 16 does not remain stationary when the work slide 5 moves to the right but experiences the required small supplementary rotation or reverse rotation which is necessary to obtain for the. gear tooth system of the workpiece l the helix angle which is slightly larger or smaller relative to the pitch of the guide grooves 12 of the lead bush 11.

It is of course also necessary for the crossing angle of the axis of the tool worm 40 relative to the workpiece axis X to be adjusted in accordance with the helix angle of the gear tooth system of be generated. This setting is obtained in that the tool head 42 is adjusted by its circular guide 43 to the corresponding angle relative to the workpiece axis X by means of a control drive 141 through a worm 142 which meshes with worm gearing 143 formed on the circumference of the tool head.

It may be assumed that a straight-tooth spur gear is to be produced with the machine described hereinabove. To this end, a cylindrical member, the external diameter corresponding approximately to the pitch circle diameter of the gearwheel to be generated, is connected to the work spindle 3 by means of the clamping device 2 into which the said workpiece is thrust by the work holder 6. Since straight-tooth gearing is to be obtained, the tool head 42 isadjusted, by the control drive 141,'relative to the tool support 44 so that the axis of the tool worm 40 intersects with the workpiece Axis X at the pitch angle of the tool worm. When the tool carrier 44 assumes its inner dead center position the feed of the tool worms 40 relative to the workpiece is obtained by virtue of the fact that the feed nut 56 is rotated by the control drive 61, by way of the worm drive 60, 59, until the external diameter of the tool worm 40 is just clear of the workpiece I.

Also, when the tool support 44 is in the inner dead center position, the tool worms 40 have their screw threads adjusted symmetrically relative to the workpiece axis X, namely by rotation of the worm 93 when the dog clutch 92 is coupled to the wormwheel 94. Since the input shaft 88 of the differential transmission 77 is stationary when the motor is switched off, rotation of the adjusting screw 93 of the planet wheel cage 97,

and therefore the output shaft 98 0f the differential transmission, causes the tool worms 40 to be rotated through the earlier-described supplementary rotation until the desired symmetrical position relative to the workpiece is obtained.

The position of symmetry of the tool worms 40 relative to the workpiece axis X for a workpiece wheel 1 with an even number of teeth is shown in FIG. 5 in which, in the interests of simplification, the axes of the tool worms are shown tipped into the plane of the drawing. In actual fact, however, in the case of a workpiece wheel 1 with straight teeth, the axes would pass through the plane of the drawing at an angle equal to the pitch angle of the worm thread. In this position of symmetry, the center lines of the two diametrically opposed sections through the worm threads of thetwo tool worms coincide in a section extending along the plane which is normal to the workpiece axis X and with the shortest connecting line between the said axes which intersect the workpiece axis and the-axes of the tool worms at right angles.

FIG. 6 shows the position of symmetry of the tool worms with an odd number of teeth of the workpiece wheel 1. In this case, one tool worm is rotated through 180 relative to its position in FIG. so that in the normal section to the workpiece axis X described herein, the'worm thread of one tool worm is disposed diametrically opposite to the gap between two adjacent turns of the worm thread of the other tool worm.

When the tool worms act on the workpiece in the position of symmetry, the pressures exerted by each tool worm on the workpiece are already automatically compensated on each tool worm with respect to the tangential components and the radial pressures are. eliminated by virtue of the fact that the tool worms are disposed diametrically opposite each other.

The motor 31 is started after the pivot pin 33 of the double-armed lever 18 is adjusted by the worm drive 38 and the spindle 37 so that the axial motion of'the work slide 5 is greater than the tooth width of the workpiece 1 and after the work slide velocity during the righthand motion is set, in accordance with calculations, to correspond to therolling speed of the tool worms. Accordingly, and by means of the crank 22, the work slide 5 is axially reciprocated in the direction of the workpiece axis X and, by means of the disc cam 69, the tool 4 supports 44 are reciprocated by the wedges 52 in synchronism and in the direction of the axis Y. The disc cam 69 is so constructed that the tool worms 40 obtain and retain their inner dead center position when the work slide in FIG. 1 moves to the right. The path traversed by the tool worms 40 relative to the workpiece 1 (a closed-circuit locus), designated with the numeral 144 in FIG. 7, results from the synchronized reciprocating motion between the workpiece and the tool worms.

During the reciprocating motion of the workpiece and the tool worm, both are rotated by the abovedescribed rotary drive so that an inherent generating action, corresponding to the profile to be generated, is obtained between the tool worms and the workpiece, but this inherent generating action is counteracted by the above-described counter-generating apparatus, operating in synchronism with the work slide motion, namely the apparatus for the axial displacement of the tool worms 40 and the apparatus for the axial displacement of the driving worm 87, such compensation taking place during the time in which the tool worms 40 are disposed in their inner dead-center position and when the work slide acts to the right upon the workpiece 1.

For preforming, the tool worms 40 are gradually, or in steps, advanced by means of their associated control drive 61 towards the workpiece axis X until the tooth profile is rolled from the workpiece over its full height. 7

approximately the same workpiece volume is displaced with each part-rolling operation.

When the workpiece gearing is being preformed, the dog clutch 92 is engaged with the dogs of the worm wheel 94 which is retained in position by the adjusting worm 93. The dog clutch retains the shaft 91 and therefore the planet wheel cage 97 of the differential transmission through the change gear set 95 and the pinion 96. The gearing is preformed with a few enveloping planes. For example it may be assumed that the change gear set 78 is so selected that for each rotation ofv the tool worm 40, and therefore one tooth pitch on the gearing to be generated, the work slide 5 performs two strokes and the ratio of workpiece strokes per tool rotation is K 2. The two positions assumed by each tool worm in the two stokes and relative to the workpiece are illustrated in FIGS. 8 and 9 which represent the engagement of the tool worm and workpiece at the end of the preforming operation. In FIG. 8 in the middle of one tool tooth is opposite to the middle .of a tooth gap of the workpiece. One tool tooth forms the tooth root of the tooth gap while the two adjacent tool teeth form the tip of the tooth profile of the two workpiece teeth adjacent to the gap. In FIG. 9 a tooth gap on the tool is disposed opposite to a tooth on the workpiece. In this configuration the middle zones of the two flanks of the workpiece tooth are formed.FlG. 10 shows a cross-section through a tooth of the workpiece wheel 1 in greatly enlarged form. The line 145 indicates the profile of the tooth which is not yet preformed over its entire height while the line 146 represents the profile of the finishformed tooth 147. The'profile of the tooth, preformed to its full height, was not shown because on the drawing this could not be clearly distinguished from the tooth profile 146. FIGS. 8 to 10 therefore disclose that, given a ratio of workpiece stroke to workpiece rotation of K 2, the teeth are preformed with three enveloping planes to a tooth profile which is a good approximation to the tooth profile of the finished tooth form.

If preforming is to be preformed with more than three enveloping planes, the change gear set 78 is so selected that the number of workpiece strokes for each tool rotation differs from K 2 but remains between K 1.5 and K 2.5. The value of K is so selected that the same meshing position between toolworm and workpiece is periodically repeated after a few teeth, depending on the desired number of enveloping planes, the number of said teeth having to be so selected that a multiple thereof deviates by one tooth from the number of teeth of the workpiece wheel.

When gear-generating is performed over the entire height, the tool womis 40 are retracted by a small amount by operating the control drive 61 in order to reduce the pressure acting upon the workpiece. Furthermore, for finish-forming, the dog clutch 92 in FIG. I is moved to the right to engage with the dogs on the gearwheel so that the planet wheel cage 97 will then be rotated by the input shaft 88 of the differential transmission 77 via the gear drive 89, 90, the shaft 91, the change-gear setand the pinion 96 so that the output shaft 98 of the differential transmission is provided with a supplementary rotation. The change-gear set 95 is previously so selected that the supplementary rotation of the output shaft of the differential transmission causes the ration K of the number'of strokes of the planes than in the preforming operation.

A displacement of the pivoting pin 33 of the doublearmed lever 18 to adapt the reciprocating speed of the tool slide in its right-hand motion to the changed rolling speed of the tool worms is not generally necessary. The operating speed in preforming is so adjusted,

that the tip zone of the worm profile performs a pure rolling motion relative to the workpiece because the principal rolling work in preforming is performed by the tip zone of the worm thread of the tool worms. lf engagementof the additional rotation of the output shaft 98 of the differential transmission 77 increases the rotational speed of the tool worms while the tool slide 5 retains the same receiprocating speed, the zone of the worm thread profile in which a pure rolling motion is performed will be displaced further inwardly relative to the toolworms and into the pitch circle zone. However, this is desirable because in finish-forming the rolling work is distributed approximately unformly over the entire height of the profile.

To produce a helical gear, a lead bush 11 with the appropriate driver coller 14 is selected, the guide grooves 12 having a pitch angle .which is nearest to the desired helix angle [3, said lead bush being mounted in the machine. The difference between thehelix angle 8 and the pitch angle of the guide grooves 12 is then adjusted, as described above, by the adjusting worm 132 on the slotted link 131. The tool heads 42 with the two tool worms 40 are also adjusted by their control drive 41, as shown in FIG. 11, so that the axis of the tool worms intersects the workpiece axis X at an angle 7 which is obtained from the desired helix angle B of the gearing to be generated and the pitch angle of the tool worms.

Preforming and finish forming is then performed fundamentally in the same manner as in the production of straight-toothed gear wheels. However, since the helix angle of the gear tooth system is measured on the pitch circle and is greater on the tooth tip than on the pitch circle, the tool-worms are appropriately adjusted to a somewhat larger angle at the beginning of the preforming operation, said angle being progressively reduced with progressive feed of tool worms 40 by operating the coupled control drives 141 of the two tool heads 42 in steps of A-y until it corresponds tothe helix angle B of the geartooth system when the tool worms have fully penetrated.

lt isfound, particularly in the preformingot helical gearing and in particular helical gearing having a large helix angle, that the tool worms 40 are displaced from the tooth direction at the beginning and end of each part-rolling operation. This isdue to the fact that they enter into the workpiece andemerge therefrom at an angle and that, accordingly,at this-moment of time and tool worm can thrust on the workpiece only in a tangential direction. To compensate for thiseffect, a correcting template 145 may be mounted von-the bracket of the spindle-bearing pedestal 40f the work slide 5, said bracket supporting the slotted line 131. A follower dle of said lever being pivotably joined to the end of a lever 148 which in turn is mounted on the shaft 137 which carries the eccentric pin 136 which functions as the bearing journal for the double-armed lever 135. The piston rod of a piston 149 is hinged on the left hand end of the lever 147 and the piston rod of a pistonl50 is hinged on the right hand end of the said lever. in FIG. 1 it is assumed that a changeover valve 151 is so adjusted that the underside of the piston 149 and the top of the piston 150 are connected to the oil pressure distribution network 49, and the oppositely-disposed sides of the pistons are connected to a return line 152 which extends to an oil sump.

The piston 149 bears at its upper end against an abutment so that the left hand end of the lever 147 is able to pivot around a fixed point. The follower roller 146 disposed on the right nand end of the lever 147 is constantly maintained in contact with the template 145 by virtue of the oil pressure acting on the top of the piston 150. Accordingly, the template 145 ensures that during roller146 on one end of a lever 147 (the right hand end in FIG-1) co-operates with the temp'late 145, the midthe reciprocating motion of the work slide the eccentric pin.137 is moved up and down by means of the

levers

147 and 148, and the driving-worm 87, which rotates the work spindle 3, has an axial displacement imparted to it, said axial displacement being superimposed on the axial displacement provided by the slotted link 131 through the lever 135.The shape of the template 145 is so selected that the rotary motion superimposed and imparted on the workpiece during the run in and run out of the tool worms, rotates the workpiece opposite to the tool worms. The shape of the template is defined by virtue of trial gear-generating operations. If the action of the template 145 is to be discontinued, which may be desirable in cold rolling of straight gearing or in finish-forming or at the end of finish-forming of helical gearing, the changeover valve 151 is moved into a second position in which oil pressure is applied to the top of the piston 149 and the underside of the piston 150 and the oppositely-disposed sides of the pistons are connected to the return line 152. Accordingly, the left-hand piston 149 is moved into its lower limiting position and the right-hand piston 150 into its upper limiting position in the associated cylinders. Since the middle of the lever 147 is pivotably joined to the end of the lever 148, the aforementioned action does not vary the position of the lever 148 relative to its center position so that the eccentric pivoting pin 136 for the double-armed lever retains its position when the action of the template is discontinued.

If longitudinally-crowned gearing is to be produced, the disc cam 69, controlling the reciprocatingmotion of the wedge 52 for operating the tool slide 44 in the Y direction, is replaced by another disc cam which, as indicated by broken lines in FIG. 2, is slightly raised in the zone corresponding to the inner dead center position of the tool slides. Accordingly, the said tool slides are retracted during each part-rolling operation in the cetnral zone by an amount AY as indicated in FIG. 12 in which the path 153 of the tool worms relative tothe workpiece is shown with a disc cam-69 corrected in the manner described hereinbefore.

The machine described hereinabove is also suitable for simultaneously cold rolling more than one gearwheel. A disc cam 69, in which two raised position are provided in the zone corresponding to the inner dead centerposition of the tool worms is used if the aforementioned gearwheels. are to be provided with longitudinal crowning, so that the path 154, illustrated in FIG. 13, is obtained for the motion of the tool worms relative to the workpieces.

What we claim and desire to secure by Letters Patent is: t

1. in a method for cold rolling a gear tooth profile on the circumference of a rotationally-driven cylindrical workpiece by means of tool worms having a reference profile, said tool worms being adapted to perform generating motions corresponding to the gear tooth profile to be generated on the workpiece on a closedcircuit locus having locus having one axis which is in the direction of and smaller than the tooth depth and which is substantially. smaller than another axis of said locus which is in the direction of the tooth length or thickness, the improvement comprising the steps of effecting said rolling in a plurality of part-rolling operations, each part-rolling operation being performed over the entire workpiece width with the tool worms being retained, at least over the tooth facewidth, in an inner dead center position in said locus, including preforming said tooth profile in a number of enveloping planes by progressive feed toward the workpiece of the operating stroke of the tool worms in the radial direction of the tool worm and workpiece between successive complete movements in said closed-circuit locus, finish-forming said profile in a larger number of enveloping planes, each enveloping plane being accomplished with the tool worms retained in a said dead center position.

2. A method according to claim 1, wherein each part-rolling operation is performed with the profile of the tool worms in the same position relative to the workpiece so that the gear tooth profile is formed over its entire length in the same enveloping planes, each said enveloping plane having the same position relative to the tooth gaps being formed.

3. A method according to claim 2, wherein said preforming is perfonned with between 1.5 and 2.5 partrolling operations for each rotation of the tool worms, while finish-forming is performed with a ratio of partrolling operations for each rotation of the tool worms which differs from said preforming ratio by a small amount, said ratio being exactly divisible into a figure no smaller than a high multiple of the number of teeth of the workpiece.

4. A method according to claim 3, wherein when using two tool wor'ins diametrically opposed to each other relative to the workpiece, the worm threads thereof are caused to act symmetrically relative to the workpiece for eachpart-rolling operation, so that the torques acting on the workpiece and resulting from the rolling pressure of the tools substantially cancel each other.

5. A method according to claim 1, for the cold rolling of helical gear teeth on the workpiece, wherein in preforming said helical gear teeth, thesetting angle of the tool worms relative to the workpiece angle is first set to a value larger than that corresponding to the helix angle and is then reduced in accordance with the associated reduction of the actual helix angle.

6. A method according to claim 1, wherein after preforming of the gear tooth profile the feed of the radial stroke of the tool worms is reduced by a very small amount in order to reduce the rolling pressure for finish-forming.

7. A method according to claim -1, wherein during the axial stroke of the tool worms a correcting motion is superimposed on the radial feed of the tool worms in order to obtain a longitudinally crowned tooth form.

8. ln a machine for cold rolling a gear tooth profile on the circumference of a rotationally driven cylindri- I cal workpiece provided with tool worms which are adjustable at an angle and are supported in tool supports which are radially movable and axially reciprocable relative to the workpiece, and having a rotary drive for the tool worms and for the workpiece to impart to both the tool worms and the workpiece a relative generating motion which corresponds to the profile to be generated, the improvement comprising means for reciprocating the tool supports exclusively in the direction which is radial relative to the workpiece axis, means for supporting the workpiece in a work slide which can be reciprocated in parallel to the workpiece axis over more than the facewidth of the gear teeth being formed on the workpiece, and means for providing rotational drive of the workpiece spindle through an interchangeable lead bush to produce the desired rotation of the workpiece.

9. A machine according to claim 8, comprising a first, angularly-adjustable slotted link mounted on the work slide and adapted, during each stroke of the work slide, to axially displace a driving worm for imparting rotation to the work spindle in order to counteract inherent generating action of the workpiece during each part-rolling motion, and a second angularly-adjustable slotted link to axially displace the tool worms during each stroke of the work slide in order to counteract inherent generating action of the tool worms during each part-rolling motion.

10. A machine according to claim 8 comprising a crank together with a crank rocker, a connecting rod and a two-armed lever for reciprocating the work slide and so disposed'that the sinusoidal oscillation of the crank rocker is converted into an axial reciprocation of the work slide so that the work slide moves ata constant velocity.

11. A machine according to claim l0, comprising a pin about which said double-armed lever pivots, said pin being slidable to vary the length of the lever arms of the lever and therefore the length of the stroke and velocity of the work slide.

12. A machine according to claim 8, comprising a interchangeablecorrecting template mounted on the work slide and adapted to impart, during each stroke of the work slide, an independent axial displacement to the driving worm for the rotational drive of the work spindle, said displacement being independent of the slotted link, in order to influence the tooth direction resulting from the rolling operation. 4 v

13. A machine according to claim 8, comprising a change gear set in the rotational drive of the tool worms and of the workpiece for adjusting the number of strokes of the work slide for each tool worm rotation.

14. A 'machine according to claim 8," wherein the rotational drive of thetool worms and of the workpiece is provided with a differential drive having a planet wheel cage which can, by means of a changeover clutch, be optionally retained or be coupled with ya supplementary drive having a change gear set.

Claims

1. In a method for cold rolling a gear tooth profile on the circumference of a rotationally-driven cylindrical workpiece by means of tool worms having a reference profile, said tool worms being adapted to perform generating motions corresponding to the gear tooth profile to be generated on the workpiece on a closedcircuit locus having locus having one axis which is in the direction of and smaller than the tooth depth and which is substantially smaller than another axis of said locus which is in the direction of the tooth length or thickness, the improvement comprising the steps of effecting said rolling in a plurality of part-rolling operations, each part-rolling operation being performed over the entire workpiece width with the tool worms being retained, at least over the tooth facewidth, in an inner dead center position in saId locus, including preforming said tooth profile in a number of enveloping planes by progressive feed toward the workpiece of the operating stroke of the tool worms in the radial direction of the tool worm and workpiece between successive complete movements in said closed-circuit locus, finish-forming said profile in a larger number of enveloping planes, each enveloping plane being accomplished with the tool worms retained in a said dead center position.

1. In a method for cold rolling a gear tooth profile on the circumference of a rotationally-driven cylindrical workpiece by means of tool worms having a reference profile, said tool worms being adapted to perform generating motions corresponding to the gear tooth profile to be generated on the workpiece on a closed-circuit locus having locus having one axis which is in the direction of and smaller than the tooth depth and which is substantially smaller than another axis of said locus which is in the direction of the tooth length or thickness, the improvement comprising the steps of effecting said rolling in a plurality of part-rolling operations, each part-rolling operation being performed over the entire workpiece width with the tool worms being retained, at least over the tooth facewidth, in an inner dead center position in saId locus, including preforming said tooth profile in a number of enveloping planes by progressive feed toward the workpiece of the operating stroke of the tool worms in the radial direction of the tool worm and workpiece between successive complete movements in said closed-circuit locus, finish-forming said profile in a larger number of enveloping planes, each enveloping plane being accomplished with the tool worms retained in a said dead center position.

3. A method according to claim 2, wherein said preforming is performed with between 1.5 and 2.5 part-rolling operations for each rotation of the tool worms, while finish-forming is performed with a ratio of part-rolling operations for each rotation of the tool worms which differs from said preforming ratio by a small amount, said ratio being exactly divisible into a figure no smaller than a high multiple of the number of teeth of the workpiece.

4. A method according to claim 3, wherein when using two tool worms diametrically opposed to each other relative to the workpiece, the worm threads thereof are caused to act symmetrically relative to the workpiece for each part-rolling operation, so that the torques acting on the workpiece and resulting from the rolling pressure of the tools substantially cancel each other.

5. A method according to claim 1, for the cold rolling of helical gear teeth on the workpiece, wherein in preforming said helical gear teeth, the setting angle of the tool worms relative to the workpiece angle is first set to a value larger than that corresponding to the helix angle and is then reduced in accordance with the associated reduction of the actual helix angle.

7. A method according to claim 1, wherein during the axial stroke of the tool worms a correcting motion is superimposed on the radial feed of the tool worms in order to obtain a longitudinally crowned tooth form.

8. In a machine for cold rolling a gear tooth profile on the circumference of a rotationally driven cylindrical workpiece provided with tool worms which are adjustable at an angle and are supported in tool supports which are radially movable and axially reciprocable relative to the workpiece, and having a rotary drive for the tool worms and for the workpiece to impart to both the tool worms and the workpiece a relative generating motion which corresponds to the profile to be generated, the improvement comprising means for reciprocating the tool supports exclusively in the direction which is radial relative to the workpiece axis, means for supporting the workpiece in a work slide which can be reciprocated in parallel to the workpiece axis over more than the facewidth of the gear teeth being formed on the workpiece, and means for providing rotational drive of the workpiece spindle through an interchangeable lead bush to produce the desired rotation of the workpiece.

10. A machine according to claim 8 comprising a crank together with a crank rocker, a connecting rod and a two-armed lever for reciprocating the work slide and so disposed that the sinusoidal oscillation of the crank rocker is converted into an axial reciprocation of the work slide so that the work slide moves at a constant velocity.

11. A machine according to claim 10, comprising a pin about which said double-armed lever pivots, said pin being slidable to vary the length of the lever arms of the lever and therefore the length of the stroke and velocity of the work slide.

12. A machine according to claim 8, comprising an interchangeable correcting template mounted on the work slide and adapted to impart, during each stroke of the work slide, an independent axial displacement to the driving worm for the rotational drive of the work spindle, said displacement being independent of the slotted link, in order to influence the tooth direction resulting from the rolling operation.