US3096669A

US3096669A - Metal forming machine and method

Info

Publication number: US3096669A
Application number: US761148A
Authority: US
Inventors: Albert F Tremblay
Original assignee: KENT OWENS MACHINE CO
Current assignee: KENT OWENS MACHINE CO
Priority date: 1958-09-15
Filing date: 1958-09-15
Publication date: 1963-07-09
Anticipated expiration: 1980-07-09

Description

July 9, 1963 A. F. TREMBLAY 3,096,659

METAL FORMING MACHINE AND METHOD Filed Sept. 15, 1958 v SheetsSheet 1 INVENTOR.

ALBERT F. TREMBLAY QMLQW A TTORNE Y5 July 9, 1963 A. F. TREMBLAY METAL FORMING MACHINE AND METHOD 7 Sheets-Sheet 2 Filed Sept. 15, 1958 INVENTOR.

ALBERT F; TREMBLAY QMLQQ'QW A TTBRNEYS July 9, 1963 A. F. TREMBLAY 3,096,659

v METAL FORMING MACHINE AND METHOD Filed Sept. 15, 1958 '7 Sheets-Sheet 4 IN VEN TOR.

ALBERT F TREMBLA Y BY @mww A TTORNEYS y 1963 A. F. TREMBLAY 3,096,669

METAL FORMING MACHINE AND METHOD Filed Sept. 15, 1958 '7 Sheets-Sheet 5 INVENTOR. AL B527 E TREMBLAY QMMM H T ORNEYS .July 9', 1963 -A. F. TREMBLAY METAL FORMING MACHINE AND METHOD '7 Sheets-Sheet 6 Filed Sept. 15, 1958 INVENTOR. ALBERT F. TREMBLAY ATTORNEYS July v9, 1963 A. F. TREMBLAY METAL FORMING MACHINE AND METHOD Filed Sept. 15, 1958 7 Sheets-Sheet 7 INVENTOR. ALBERT F. TREMBLAY ATTORNEYS United States Patent Office 3,096,669 Patented. July 9, 1963 3,096,669 METAL FORMING MACHINE AND METHOD Albert F. Tremblay, Toledo, Ohio, assignor to Kent- Owens Machine Company, Toledo, Ohio, a corporation of Ohio Filed Sept. 15, 1958, Ser. No. 761,148 9 Claims. (Cl. 80-16) This invention relates to metal forming methods and apparatus and is particularly directed to a method and apparatus for rolling teeth on gears or the like.

This application is a continuation in part of my copending application, Serial No. 654,697, filed April 24, 1957, which was in turn, a continuation in part of my earlier application Serial No. 524,344, filed July 26, 1955 (both applications being now abandoned).

The primary object of the invention is to provide a machine for forming metal parts such as the teeth of gears or the like which will complete a workpiece in a very small fraction of the time required to complete the same piece by the usual methods, whereby cutting tools are used to remove the metal.

Another object of the invention is to provide a method and apparatus for rolling metal to forms such as the teeth of gears or the like in which the forming elements are given a planetary motion and roll across the face of the workpiece.

Other objects and advantages of the invention will become apparent from the following detailed specification, reference being had to the accompanying drawings, in which-- FIG. 1 is a front elevational view, with parts in section and parts broken away, of a machine embodying the present invention for carrying out my novel method;

FIG. 2 is a section on line 2-2 of FIG. 1;

FIG. 3 is an enlarged side elevational view, partly in section, of the forming head portion of the machine;

FIG. 4 is a section on line 4-4 of FIG. 3;

FIGS. 5, 6 and 7 are diagrammatic views showing the rolling action of the tool on the work;

FIG. 8 is a somewhat diagrammatic view in front elevation, with parts in section and parts broken away of a somewhat modified apparatus for carrying out my novel method;

FIG. 9 is a front, elevational view, with parts in section and parts broken away, of a modified machine embodying the present invention; and

FIG. 10 is an enlarged side elevational view, with parts broken away and parts in section, of the machine shown in FIG. 9.

Referring to FIGURE 1, one form of a machine embodying the present invention includes a frame 10- on which a lower work driving and carrying sub-frame 12 is mounted for guided vertical movements in gibs 14. Also mounted in the frame is a main spindle 16 carrying a forming head 18 which will be subsequently described in detail. A drive motor 20 is carried by the frame 10 and is connected by belts 22 to a pulley 23 attached to the main spindle 16. Any suitable synchronous drive means such as a chain drive 24 extends from the spindle 16 to a work driving bevel gear set 26 the output shaft of which is designated 28. Shaft 28 thus rotates in a definite timed relationship with the rotation of spindle 16.

Shaft 28 carries a Geneva driver dog 30 which meshes with a star wheel 32 (FIG. 2) to provide intermittent motion to a back shaft 34. Back shaft 34 has two driving gears keyed thereto, one of which, designated 36, meshes with a sub-frame elevating feed gear 38 and the other of which is a bevel gear 40 meshing with a companion bevel gear 42. The bevel gear set 40, 42 is accessible beneath a cover plate 44 and can be changed to provide different speeds of operation for a shaft 46 on which gear 42 is mounted. Shaft 46 is journaled and rigidly supported against bending in a heavy part of the sub-frame 12 and carries a workpiece 50 at its end.

The sub-frame elevating feed gear 38 is mounted on a shaft 52 over which forward and

reverse bevel gears

54, 56 are mounted for free rotation and are in constant mesh with a bevel gear 58. A clutch 60 keyed to the shaft 52 and slidable thereon causes driving engagement between the shaft and either of the

bevel gears

54, 56 so that one or the other may be coupled to transmit power to the bevel gear 58 to cause elevation or depression of the workpiece 50 relative to the forming head.

Bevel gear 58 is keyed to or made a part of a feed nut 62 which receives a stationary feed screw 64 extending upwardly from the base of the main frame 10. As the feed nut 62 is rotated in one direction or the other the sub-frame 12 is raised or lowered, the thrust of the feed screw being taken by

shoulders

65 or 66 in a part of the sub-frame.

It will be seen from the structure so far described, which is illustrative only, that a workpiece 50 will be given an intermittent rotational movement in some predetermined timed relationship to the rotation of the main spindle 16. The drive to the workpiece originates in chain 24, bevel gear set 26, shaft 28-, Geneva

indexer

30, 32, shaft 34, change bevel gear set 40, 42 and shaft 46'.

At the same time that the work is intermittently rotated as above described it is raised or fed in the direction of the forming head 18 by an intermittent feed drive. The work is thus raised or lowered in predetermined increments by the feed drive which originates in shaft34, which is intermittently driven or indexed, and is taken through

change gears

36, 38 to shaft 52, through clutch 60 to one or the other of

bevel gears

54, 56, and the feed nut bevel gear 58. It will thus be seen that provision is made for indexing the Work about the axis of shaft 4-6 and for raising the work periodically during continuous rotation of the forming head 18. For example, a feeding movement may be imparted to the work at the end of each increment of movement of the shaft 46 on which the work is carried, the shaft 46 being indexed in its rotation at a known rate with respect to the rotation of the forming head 18. The rate of feed is determined by the

change gears

36, 38 and the extent of the feed is determined by the pitch of the feed nut 62 and its cooperating feed screw 64. Thus, as hereinafter described, if a gear is being formed from a workpiece 50*, shaft 46 is indexed a distance between teeth of the desired gear at each engagement of the Geneva drive, and each indexing movement is accompanied by a small vertical feeding movement of the work in the direction of the tool carrying head by the intermittent rotation of the feed nut 62.

As hereinafter described the vertical feeding movement of the work may be timed with relation to the workpiece, if desired, so that an incremental feeding movement takes place at the end of each rotation of the work. Thus, if a gear is being formed, all teeth will be formed to the same partial depth between each increment of vertical feed. A mechanism for carrying out such an operation is shown in FIG. 8 and will be described subsequently.

Referring now to FIGS. 3 to 7, the present invention is shown as applied to a machine for forming the teeth of a bevel gear. The gear blank is provided in an appropriate frusto-conical form and is designated 50 in FIGS. 1, 3 and 4. As in any bevel gear the tooth may be tapered from end to end but the root of the tooth is always a straight line.

The forming head 18 is carried over and driven by the main spindle 16 and is journaled in suitable anti-friction bearings 70, 71. As shown best in FIG. 3 the main spindle is journaled at one end in the frame and is supported in an overarm 72 at its outboard end, with the main drive pulley 23 keyed thereto.

A stationary internal ring gear 74 is fixed to the frame 10 and a plurality of planet gears 76 are meshed therewith. Each planet gear is carried at one end of a forming tool shaft 78 which is journaled for rotation in, and carried by the forming head 18 for revolution about the main spindle 16. Tool shaft 78 extends forwardly of the forming head and has a driving connection with a forming tool 80. An outboard bearing plate 82 may be mounted over the main spindle 16 to rotate therewith and to support what is in essence an extension 84 of the tool shaft 78. The tool 80 is thus firmly supported against deflection or displacement under load by the heavy shaft 78 which is mounted in spaced bearings 87 and 88 in the forming head 18. The tool is driven in a planetary manner, rotating on the axis of shaft 78, and revolving about the axis of the main spindle by the connection of planet gear 76 with the stationary ring gear 74.

It will be seen from FIG. 4 that the tools 80 are used in even-numbered sets, as for example four units spaced equally about the center of the main drive spindle 16. If desired, however, a single tool properly balanced may be used. The entire head is thus balanced, if the mass of each tool and its rotating shaft is the same, and care is taken to assure that both statically and dynamically the elements are matched for vibrationless revolution about the axis of spindle 16.

Each tool 80 comprises a roll body keyed to the respective spindle 78, and having a portion of its periphery formed as an arcuate, cam-shaped rolling surface 86, the cross section of which is the shape of the cross section of the gear to be formed taken from the center of the crest of one tooth to the center of the crest of the next adjacent tooth. Since the rolling surface 86, during its contact with the workpiece as hereinafter described, not only rotates about its own center but also revolves about the center of the main drive spindle 16, its contour is arcuate with the center of the are between the center of the spindle 16 and the center of the shaft or spindle 84. The contour is further complicated, in the case where the workpiece is a bevel gear, by the fact that the final depth of the teeth increases from one end of the gear to the other. In this instance rolling of the deep end of the tooth begins first and the machine proceeds through a great many complete cycles before the tool has entered suificiently far at the deep end that rolling of the entire tooth begins. Rolling, of course, takes place along a straight line extending from end to end of the tooth being formed, the line being parallel to the root line of the ultimate tooth.

In the past, planetary rolling mills have been known in which a plurality of rolls mounted on a rotating carrier have been used to reduce the thickness of metal by a succession of light passes. The present method, however,

differs in that the path taken by the roll surface along the work is linear rather than circular as in the case' of the planetary rolling mills. Thus, in my machine the roll contact can extend over a very long zone without increasing the radius of the roll carrying head. The advantages of pressure rolling are principally in the speed with which a part such as a gear may be formed, and secondly the benefits derived from cold working of the metal which produce much better characteristics in the finished part as compared to a method such as cutting in which the metal of the blank is removed to form the final piece.

The operation of the machine shown in FIGS. 1-4 and a description of the method involved is as follows: The gear blank or workpiece 50 is mounted on the end of shaft 46 and the main drive motor 26 is started. The workpiece is automatically rotated and fed upwardly until the first rolling tool head 80 contacts it. If the work is to be tapered as is the case of a bevel gear, the

first tool head will strike and roll over only the high end of the blank where the teeth will ultimately have their maximum depth. Since the spindle 16 which is is driving the tool head is connected by a synchronous drive mechanism to bevel gear set 26, drive shaft 28 is turning at a predetermined rate and constant phase relationship to the motion of the tool head. Thus the

Geneva motion

30, 32 is actuated periodically with respect to the tool head and the period of operation depends on the number of tools carried by the head. If four tools are used, as in the form shown in the drawings, the Geneva motion is so arranged as to cause four indexing movements of shaft 34 for each revolution of the tool head. The timing is so arranged that the indexing movement of shaft 34 takes place immediately after a tool 86 has passed over the workpiece. In this machine at the same time, a slight upward feeding movement is imparted to the work by rotation of shaft 52 and the feed nut 62.

When shaft 34 is moved, bevel gear set 40, 42 turns shaft 46 a definite distance equal to one tooth of the gear being formed. If the blank is to be formed into a gear with twenty teeth, the indexing movement will equal 18. Thus the next tool 80 will strike the blank and roll the metal thereof at the location of the next tooth.

Gears

40, 42 are change gears and selection of the proper set will determine the number of indexing movements required for one revolution of shaft 46 and thus the number of teeth formed on the blank 50.

Shaft 34 drives the feed shaft 52 through the change gear set 36, 38 and if clutch 60 is engaged shaft 52 in turn drives the feed nut 62 over the stationary feed screw 64, so that the feed nut carries the frame 12 and all of the lower mechanism upward and thus feeds the blank 50 in the direction of the rotating tools. The feed increment is made small, so that at the end of one complete revolution of the blank (twenty indexing movements of shaft 46) the total upward feed will be small enough that rolling of the teeth can proceed without undue stress of any of the parts. For example a feed rate of about .020" per revolution is satisfactory. Thus the second pass over a given tooth is made .020" deeper than the pass on the previous revolution. Rolling continues until the proper tooth depth is reached on the first tooth, after which the clutch 60 is disengaged and the feeding movement stopped. As shaft 34 is still rotating the workpiece will continue to be indexed and rolling of all of the teeth will proceed to the same depth.

It will be seen that as feeding progresses, the tools 80 finally reach the point of entry where the respective teeth are nearly formed. At this time the rolling will be found to be proceeding in such a manner that the path of the periphery of the tool 80 is a straight line in contact with the entire face of the blank along the tooth. In the machine shown the tool turns in a counterclockwise direction for about 70 while its center moves clockwise about 20 during the rolling cycle. This is shown diagrammatically in FIGS. 5, 6 and 7. It will be seen from the diagrammatic disclosure of these figures that a very long line contact is obtained by reason of the contour of surface 86 and the fact that the planetary motion of the roll rotates the tool counterclockwise while its supporting body is rotating in the opposite direction.

A calculation of the time required to complete a common bevel gear will indicate the advantage of the present invention. If the gear is to have twenty teeth and the maximum depth of the teeth is .300, and a four tool head is used such as shown in the drawing, 600 roll passes per minute will be made with a spindle speed of only rpm. This gives 10 roll passes per second, or two seconds as the time required for each revolution of the blank 50 and shaft 46. If the increment of feed is set at .020" per revolution, 15 revolutions of the blank will be required to obtain the finished depth of tooth, so

that the entire operation takes only 15 times 2 seconds or 30 seconds to completely form a gear.

It will be apparent that the feeding motion imparted to the gear blank in the direction of the tool may be made only once per revolution of the blank if desired. The machine shown in FIG. 1 imparts an increment of feed to the blank each time the blank is indexed between teeth, while in FIG. 8 a machine is shown in which all teeth are formed to the same depth before the blank is given an increment of feeding movement. Thus provision is made for feeding the blank with each of its completed revolutions.

As shown in FIG. 8 the machine is essentially similar to the form previously described so far as the rotation of the blank is concerned. However, clutch 60 is shown disengaged from the

opposed bevel gears

54 and 56 so that no motion is imparted to the feed screw 64 by the shaft 52. Instead the feed nut 62 is, in this form, held against rotation in the housing or sub-frame 12 by any suitable releasable means such as a screw 90. In this form a rotatable feed screw 91 is substituted for the stationary feed screw 64 of FIG. 1, and provision is made for turning this screw periodically in timed relation to the rotation of the gear blank 50. It will be apparent that if screw 91 is turned, the housing and all of the mechanism and parts carried thereby will be elevated or 'fed in a direction towards the axis of the tool carrying head 18-.

Any suitable means may be used to cause the periodic timed movement of the feed screw 91. In the form shown, a gear 92 is keyed to the screw and is in mesh with a worm 93 which in turn is provided with a coaxial ratchet wheel 94. A pawl 95 is provided in association with the ratchet wheel 94 and is carried by a slide 96.

The slide 96 is mounted for reciprocation in the frame of the machine between gibs 97, and is operated by a piston 98 which is moved pneumatically in one direction and is spring pressed in the return direction, the piston 98 being disposed in a cylinder 99.

Air to the cylinder 99 is supplied from a line '100 (which may be the usual shop air line) and the cylinder is energized whenever a control'valve 102 is moved to such a position that a cylinder supply line 104 is connected to the line 100. The valve 102 may conveniently be of the spool-type with the spool normally closing oil? the supply line and adapted to be moved out of its normal position by air pressure acting against the end of the spool.

The gear 42 which rotates the blank during operation may be provided with a pin 106 which operates at each revolution to open a poppet type pilot valve 108 by which air is admitted from the supply line 100 to the end of the main spool type air valve 102 shifting the latter from its normally closed position to the position in which supply line 100 is connected to line 104. A brief charge of air is thus admitted to cylinder 99 against the piston 98 forcing the piston outwardly of the cylinder. The resulting excursion of the piston 98 and slide 96 to which it is attached operates the pawl 95 and ratchet wheel 94 indexes the feed screw 91 and through worm 93 and gear 92 causes the feed screw 91 to turn and the workpiece to be elevated a predetermined distance in a direction normal to the axis of the tool.

When the valve 108 seats again, the main valve is spring pressed to its normal position in which line 104 is vented, and piston 98 is returned by its spring to a position in which it is ready to make a new cycle for operation of the pawl 95 and ratchet wheel 94.

The mechanism above described thus imparts a feeding movement to the work only once at each rotation of the work so that all of the gear teeth are formed to the same I depth between feeding movements. Thus the engagemerit between a tool and any particular portion of the workpiece is at a slightly greater depth, asin the previous form shown in FIG; 1, but the feeding movement of the axis of the work in a direction normal to the axis of the tory rather than a rotary manner.

tool takes place only once per revolution. If it is desired to change to the operation in which a very small increment of feed occurs between each contact of a forming tool against the work, screw can be backed out and clutch 60 engaged with the proper bevel gear, and thereafter feeding of the workpiece will proceed under the control of shaft 52 as in the machine shown in FIG. 1.

When operating in such a manner that an increment of feed occurs only one for each revolution of the blank 50, the depth of the tool engagement is, of course, determined by the pitch of the feed screw 91 and the angular extent of its movement. The pawl and ratchet

mechanism

94, 95 can be adjusted to impart a greater or less movement to the feed screw 91 by changing the length of travel of the slide 96 on which the pawl is mounted so that the pawl will pick up one, two or three teeth of the ratchet. For this purpose adjustable stop mechanisms are used at each end of the slide and its associated piston to determine the held in adjusted position by appropriate lock nuts. When the screws are placed with their nose portions close together the excursion of the slide 96 in each direction is reduced and the motion imparted by the pawl to the ratchet wheel is also reduced. As the adjusting screws are moved away from each other the length of the movement of the slide 96 and piston 98 is increased. Obviously any other suitable mechanism may be used to vary the degree of turning movement imparted to the feed screw 91 and thus to the blank 50 at each rotation of the blank. In practice the blank is raised in the direction of the tool only a few thousandths of an inch at each revolution so that each successive tool engagement with any particular portion of the blank is at only a slightly greater depth than the preceding engagement.

The mechine shown in FIG. 8 also diifers rom the machine shown in FIG. 1 in that it illustrates the practice of the present invention by a single tool 80 mounted on the head 18. The tool is of the same character as that shown in FIGS. 3-7 and is moved in the same way by the same mechanism as previously described. The head may be counterbalanced in any suitable manner.

A gear cutting machine according to the invention can be modified to roll gears with tools moving in a oscilla- A machine of this type, shown in FIGS. 9 and 10, has a modified forming head and drive mechanism, which includes a main spindle 1 14 carrying a tool shaft 116 mounted in suitable bearings. The shaft 116 has a sector-shaped tool 118 rotated by a planet gear 120 which meshes with a stationary ring gear 122, in a manner similar to the previous embodiments. The main spindle 114 is driven in an oscillating manner by suitable means such as a crank 124, a connecting rod 126, a crank pin 127, a drive pulley 128, and a motor 130. The distance between the crank pin 127 and the center of the pulley 128 is less than the length of the crank arm 124 so that when the drive pulley is rotated, the crank arm and, hence, the spindle 114 and the tool 116 are oscillated. The tool 118 is in contact with the gear blank '50 through only a small portion of an oscillatory stroke and the remainder of the stroke, with the tool 118 out of contact with the gear blank 50, is used to index the gear blank, also in the same manner as in the previous embodiments but by means of a belt 131 driven by the shaft of the drive pulley 128. The blank 50 also can be fed toward the tool 118 at this time, as with the machine shown in FIG. '1, or fed only after each complete revolution of the gear blank, as with the machine shown in FIG. 8.

The tool 118 is positioned relative to the motion of the connecting rod 126 so that the tool is near one end of an oscillatory stroke when in contact with the gear blank 50. This :occurs when the connecting rod 126 is near the dead center position (with the connecting rod in alignment with the crank pin 127 and the axis of the pulley 128). In this manner, the movement of the main spindle 114 and, hence, the tool 118 is slowest in relation to the rotational speed of the pulley 1 28; thus, the speed of the tool 118 is at a minimum when it contacts the gear blank 50. With the tool 118 traveling in a clockwise direction, it moves relatively slowly as it contacts the gear blank 50 and slows down still further until it reaches the end of its stroke just past the gear blank. Upon the return stroke in a counterclockwise direction, the tool 118 again contacts the gear blank 50 when moving relatively slowly and speeds up slightly as it moves away from that end of the oscillatory stroke. In this manner, the tool 118 moves relatively slowly when it contacts the gear blank 50 in either direction, in one direction slowing down further after it contacts the gear blank and in the other direction speeding up slightly after it contacts the blank.

It will readily be seen that the oscillatory method of forming gears has two principal advantages. First, the tool 118 makes two passes over the gear blank 50 during a single revolution of the sheave 128. Second, the tool 118 moves relatively slowly when it contacts the gear blank 50 which decreases the initial impact force exerted on the gear blank, reducing the noise associated with the machines operation and also reducing vibration transmitted to and through the machine.

It has been found that the metal in the gear blank 50 below the root of a tooth being formed increases in density after each pass of the

tool

80 or 118. This is true because the tool forces the metal downwardly which both compacts it and displaces (as by coining) a portion upwardly into the teeth. In this manner, the height of a tooth is increased during each rolling pass of the tool by both deepening the root and extending the height of the tooth by forcing metal upwardly. Thus, to form teeth having a total depth of 0.400" the total penetration below the surface which originally defined the gear blank is 0.300. The metal below the root of the gear teeth is not only compacted but is also work hardened by the action of the tool. For example, in one gear, the original gear blank had a Brinell hardness of 152 before the teeth were rolled and a Brinell hardness of 310 after rolling. The compaction of the metal and its increased hardness increase the strength of a gear at the roots of the teeth, exactly where most gear failures occur.

However, because of the increasing density of the metal and hardness thereof as the tool more deeply penetrates the gear blank, it has been found desirable to start with a given rate of feed of the gear blank toward the axis of the tool and decrease this rate of feed for subsequent rolling passes over the blank. This can be accomplished by various means, one of which is illustrated in FIG. 9. Accordingly, the manually operated screw 110 (FIG. 8) is replaced by a stop rod 132 slidably supported in a holder 134. The rod 132 has a roller 136 urged against a cam 13% by a spring 140 with the cam held by a suitable supporting arm 142 which is adjustably attached to that portion of the machine carrying the gear blank 20 upwardly.

The cam 133 is vertically positioned by means of the adjustable arm 142 so that the upper edge of the cam is in alignment with the roller 136 when the gear blank 50 is just out of contact with the tool 118. When a gear is formed, the earn 138 moves upwardly as the portion of the machine carrying the gear blank 50 moves upwardly and thereby forces the stop rod 132 inwardly toward the slide 06. As the rod 132 is moved inwardly, the movement of the slide 96 is decreased and, therefore, the movement of the pawl 95 and ratchet wheel 94 are also decreased. This, in turn, limits the rotation of the screw 91 and, hence, the upward movement of the gear blank 50.. The feed of the gear blank is thereby decreased and the tool penetrates the metal to a lesser extent with each subsequent pass.

The supporting arm 142 is slotted so as to be vertically adjustable to vary the rate of feed and the change in the rate of feed can be varied by substituting cams of different slopes or configurations. Many configurations are possible for many types of conditions. For example, the cam can have a surface generally of a semi-hyperbolic shape to more rapidly decrease the rate of feed as penetration increases.

The rolling edge of the tool 118, similar to the edge of the tool 80, is thicker in horizontal cross section at the portion which contacts the larger end of the gear blank 50 than at the portion which contacts the smaller end of the gear blank 50, thus forming a wedge shape tooth. The rolling edge of the tool, of course, is subjected to constant wear and must be reground to maintain the proper shape and surface finish. Each time the tool is ground, the thickness of the rolling edge is decreased although the angle and shape of the wedge remains the same. Because only a portion of the tool contacts the gear blank, the decrease in thickness in the rolling edge can be compensated for by causing a portion of the rolling edge toward the thicker end to contact the gear blank. By making the rolling edge of the tool long in relation to the width of the gear blank, a single tool can last for many extra hours of operation.

To adjust the portion of the tool 118 which contacts the gear blank 50, the tool 118 is moved about its axis 116 to move the rolling edge in relation to the blank. This can be accomplished by providing a gear rack 144 on the periphery of the ring gear 122, which rack is engaged by a worm 146 which can be turned by a crank 148. The ring gear 122 is attached to the body of the machine by bolts 150 extending through arcuate slots 152 which enable the ring gear 122 to be turned in relation to the gear blank 50 simply by releasing the bolts 150 and turning the crank 148 to turn the worm 146, and, hence, the ring gear, after which the bolts 150 are again tightened. During this movement of the ring gear 122, the axis 116 of the tool 118 remains in the same position, as determined by the main spindle 114, and the tool 118 is thereby slightly rotated on its shaft 116 due to the engagement of the planet gear and the ring gear 122. This changes the position of the tool 118 and changes the portion of the tool 118 which contacts the gear blank 50. Each time the tool 118 is ground, or after a predetermined length of operation, the crank 148 can be turned a given amount to enable the gear blank 50 to be contacted by the tool 118 toward its thicker end and thus compensate for the decreased thickness in the rolling edge of the tool.

While the invention has been disclosed in conjunction with a specific form and disposition of the parts, it should be expressly understood that it is capable of numerous modifications and changes without departing from the spirit of the appended claims.

What I claim is:

1. A method of forming a gear from a gear blank by rolling, which comprises supporting the gear blank, applying a plurality of successive forces to a surface of the gear blank in a direction toward the axis thereof and substantially at right angles to the root of a tooth to be formed therein, the forces being sutficient to substantially uniformly depress the metal of the blank over all portions of the blank to which the forces are applied, and the forces being applied along a line laterally to the width of the blank, subsequently moving the blank toward the direction from which the forces are applied, reapplying forces in the above described manner, and subsequently moving the blank a lesser amount toward the direction from which the forces are applied.

2. Apparatus for forming a metal piece which comprises the combination of means to support a metal blank for rotation about an axis, a rotatable tool carrying head, at least one cam-shaped tool carried by said head and mounted for planetary movement thereon, means to oscillate said head, to cause a planetary movement of said tool thereon and to cause the speed of said tool to vary, with the relative speed being slow when said tool is in engagement with the blank, said tool being shaped to provide rolling linear engagement with the entire width of said blank during combined rotation and translation of said tool, means to cause a step-by-step :feeding movement of said bi-ank about its axis, means to cause a second feeding movement of said blank in a direction towards the axis of said tool carrying head, whereby successive portions of the face of said blank are formed by successive engagements.

3. Apparatus for forming a metal work piece into a bevel gear or the like which comprises the combination of means to support a metal blank for rotation about an axis, a rotatable tool carrying head, at least one tool mounted for rotation on said head, said tool having an eccentric work penetrating portion, first drive means to rotate said head, second drive means to rotate said tool on said head to cause a planetary movement of said tool, means to correlate the movements of said first and second drive means to cause said eccentric tool portion to properly engage the work when the tool is brought into working engagement with said work piece, said eccentric portion of said tool being so related with respect to the movement thereof that one operation of said tool creates uniform penetration throughout the extent of its rolling engagement with the work, means to cause a step-by-step movement of said work piece about its own taxis, and means to cause a feeding movement of said work piece in a direction towards the axis of rotation of said tool carrying head.

4. Apparatus in accordance with claim 3 and means to correlate said feeding movement of said work piece with said step-by-step movement whereby said feeding movement takes place only after a complete step-by-step rotation of said blank.

5. Apparatus in accordance with claim 3 in which said first drive means to rotate said head includes a crank connection.

'6. Apparatus in accordance with claim 3 in which said first drive means includes means to impart an oscillatory movement to said head.

7. Apparatus in accordance with claim 3 and means for changing the portion of said work penetrating tool which engages said work piece.

8. Apparatus in accordance with claim 3 and means to vary the feeding movement of said work piece to cause a greater feeding movement of said work piece during one portion of an operating cycle of the machine and a lesser feeding movement of said work piece during another.

9. Apparatus for forming a metal workpiece into a bevel gear or the like which comprises the combination of means to support a metal blank for rotation about its axis, means to move said blank about its axis in a stepby-step movement, means to engage said blank at each step in its movement, said means including a rotating cam-shaped tool having a periphery shaped to provide substantially linear engagement with said blank during combined rotational and translational movements of said tool, means to positively rotate said tool, means to positively translate said tool during rotation, means to feed the axis of said blank toward said tool at a predetermined rate whereby each successive rolling engagement between said tool and a particular portion of said blank is at a slightly greater depth, and means to continue the rolling engagement of said tool for at least one revolution of said blank about its axis after the finished depth is reached.

References Cited in the file of this patent UNITED STATES PATENTS 563,301 OConnor July 7, 1896 989,643 Reinhard Apr. 18, 1911 1,029,513 Reinhard June 11, 1912 1,240,918 Anderson Sept. 25, 1917 2,350,882 Drummond June 6, 1944 2,435,405 Praeg Feb. 3, 1948 2,715,846 Grob et a1. Aug. 23, 1955 2,991,672 Meyer et a1. July 11, 1961 FOREIGN PATENTS 2,598 Great Britain Feb. 22, 1911 981,902 France June 1, 1951

Claims

1. A METHOD OF FORMING A GEAR FROM A GEAR BLANK BY ROLLING, WHICH COMPRISES SUPPORTING THE GEAR BLANK, APPLY ING A PLURALITY OF SUCCESSIVE FORCES TO A SURFACE OF THE GEAR BLANK IN A DIRECTION TOWARD THE AXIS THEREOF AND SUBSTANTIALLY AT RIGHT ANGLES TO THE ROOT OF A TOOTH TO BE FORMED THEREIN, THE FORCES BEING SUFFICIENT TO SUBSTANTIALLY UNIFORMLY DEPRESS THE METAL OF THE BLANK OVER ALL PORTIONS OF THE BLANK TO WHICH THE FORCES ARE APPLIED, AND THE FORCES BEING APPLIED ALONG A LINE LATERALLY TO THE WIDTH OF THE BLANK, SUBSEQUENTLY MOVING THE BLANK TOWARD