US2285575A - Bevel gear blank and the method and means for producing the same - Google Patents

Description

F. V. ELBERTZ June 9, 1942.

BEVEL GEAR BLANK AND THE METHOD AND MEANS FOR PRODUCING THE SAME -Filed Feb. 15, 1958 5 Sheets-Sheet 1 mVfNrore FY/(NK V ELBERTZ June 9, 1942. F. v. ELBERTZ 2,285,575

BEVEL GEAR BLANK AND THE METHOD AND MEANS FOR PRODUCING THE SAME- 5 SheetsSheet 3 Filed Feb. 15, 1938 gjwuc/wboa FRANK VELBE/PTZ BWJM fi Z Patented June 9, 1942 UNETED STATES PATENT GFFECE BEVEL GEAR BLANK AND THE METHOD AND MEANS FOR PRODUCING THE SAME 13 Claims.

This invention relates to improvements in bevel gear blanks and the method and means for producing the same.

Bevel gears are generally fashioned from blanks of forged origina suitable billet is subjected to a drop-forging action which has the effect of mushrooming an end of the billet into a head of oversize dimensions; after treatment the blank is finished by machining or grinding with the finishing operation including the fashioning and completion of the gear teeth. The drop-forging action serves to provide several advantages over attempting to fashion the gear from a block of metal, in that a considerable wastage of material is avoided, and the gear becomes stronger.

While these advantages are present, the gear itself has its limits as to strength so far as resistance to tooth stress is concerned, due to the fact that the fibre or grain of the mushroomed head tends to extend in directions corresponding to the length of the teeth; since this direction is transverse to the direction of pressure applied to the tooth in operation, the tooth formation must depend mainly upon the tempering,

etc., to provide the tooth strength, the fibrestress value-the value of the resistance set up by the fibres against breakage or separation-being low, due to the fact that the tooth pressure is applied equally along the length of the fibres so that the resistance against cleavage must be found in the connecting media for the fibres rather than in the fibres themselves; the distinction is apparent by considering the fact that a piece of wood can be readily split with the grain but is diflicult to fracture by pressure across the grain.

Efforts have been made to reduce wastage by attempting to fashion the blank with embryo teeth, but the efforts have been generally unsuccessful in practice. This has been due in part to the difiiculties set up by the flash which is inherently present in such attempts. The die structures must provide for the flash, and the efforts heretofore made have been unable to provide for the flash action and at the same time ensure the production of uniformity in the blank, since any attempt to control the flash form and amount have led to variations in pressure action within the die, thus affecting uniformity of product. Other difficulties arise such, for instance, as die stability, in addition. and because of these various conditions, previous attempts to provide a toothed blank acceptable to the trade have been unsuccessful.

The present invention is designed to produce a forged blank of the toothed type, thus reducing the volume of wastage, and, in addition, has as an important object the strengthening of the tooth formation itself by tending to present the tooth with a fibre formation in which the tooth pressure is exerted more across the grain than with the grain, thus increasing the fibre stress value of the gear teeth over the present gear structures.

This result is obtained through the respective die formations which, during the forging operation provide a succession of activities upon the metal of the stock such as to vary the fibre continuity along approximately predetermined lines and to set up pressure activities which ensure a complete shaping and texture arrangement of the body of the tooth zone of the blank so that not only is the homogeneity of the metal of the blank secured throughout, but is reproduced in a succession of blanks, with the result secured without materially affecting the dies, so that, under normal operation, the latter will be serviceable for extended runs of blanks. And in such shaping the trend of varying the continuity of fibres so as to tend in the direction of the depth of the tooth is established, to thereby increase the fibre-stress value of the tooth.

In securing these results, the flash conditions are met in such way as to maintain the characteristics set up by the blank-development action during forging. While certain resistances are present to ensure the development of pressure active during the formation period, the die arrangement permits the passage of the excess materialwhich forms the fiashoutwardly beyond the zone of the blank which provides the material for the finished gear, with the flash itself not offering a resistance pressure of a value such as to affect the shape and texture formation set up as the forging action proceeds. In other words, provision is made for accommodating the flash, but the presence of the latter is itself inactive to materially affect the development of that portion of the blank which forms the finished product. By rendering the flash ineffective in this way, the fact that variations in flash values may be present in successive operations, such variations are ineffective to materially vary the shape and texture characteristics of that portion of the blank which forms the finished gear.

In addition, the invention permits of the use of stock either in billet or tubular form, the latter form tending to still further reduce the amount of wastage. The two forms may slightly vary the action upon the metal during forging, but the distinction does not materially affect the characteristic above referred to of having the fibre continuity include portions extending in the direction of depth of the tooth instead of simply in the direction of length of the tooth. With the tubular form of stock the wastage is not only reduced by reason of the presence of the axial opening of the gear as a part of the stock itself, but it enables a closer approach to the actual metal requirements for the gear and thus tends to reduce the volume of flash.

As a result, the blank produced is not only in a form which can be readily fashioned into the finished gear with a minimum of finishing activities, but the product becomes of superior strength clue to the increase in the fibre-stress value of the tooth zone, with the result secured with a reduced amount of wastage as well as a smaller volume of stock as the source of the product, thus materially reducing the cost of productionsince the cost of production is decreased both in the blank forming operation and in the finishing operation; at the same time the fibre-stress value of the product is increased. Coupled with this is the fact that the result is obtained under conditions which are easy on the die formation so that the die structure is usable over extended runs before requiring re-conditioning.

To these and other ends, therefore, the nature of which will be made apparent as the invention is further disclosed, the invention consists in the improved construction and formation of the blank, the method of producing the same, and the combination and arrangement of the die structures constituting the means for producing the blank, all as hereinafter more clearly described in the following description, illustrated in the accompanying drawings, and more particularly pointed out in the appended claims.

In the accompanying drawings, in which similar reference characters indicate similar parts in each of the views:

Figure 1 is a top plan view of a preferred lower die formation used in the forging opera tion.

Figure 2 is a vertical cross sectional view taken diametrically of Figure 1.

Figure 3 is a bottom plan view of a preferred form of upper die structure employed in the invention and adapted to co-operate with the die of Fig. 1 in practicing the invention.

Figure 4 is a central vertical section of the die of Figure 3.

Figure 5 is an assemblage of the upper and lower die structures positioned at the beginning of the forging action, the view illustrating an alternative form of stock and the provisions made to permit of such stock use.

Figure 6 is a central vertical section taken through an assemblage of the dies of Figs. 1 to 4, the lower die being shown as an insertible die blank instead of a complete die, the two dies being shown in the positions reached when the forging operation is completed.

Figure '7 is a side elevation of the dies of Fig. 6 to illustrate the flash space contour.

Figures 8 to are views illustrating the blank produced by the forging operation, Fig, 8 being a bottom plan, Fig. 9 a side elevation, and Fig. 10 a top plan of the blank.

The bevel gear blank of the invention is produced by the forging action set up between two dies movable relatively to each other. These dies may be mounted in either of a number of different types of die presses, and hence it is unnecessary to present the details of such press. In practice the dies are arranged in superposed axial alinement, with the lower die generally fixed as to position, the upper die being movable vertically toward and from the positioned die; while, in practice, either of the two dies might serve as the lower die, and the press may be of the type in which both dies are movable; in the present disclosure, it is assumed that the lower die will remain stationary, and will therefore be referred to as the stationary die member, with the upper die movable and therefore referred to as the movable die member of the assembly; this permits simplicity of disclosure, but is used simply as illustrative, since the particular arrangement of the dies in the press or the manner in which the relative movement of the dies is obtained is variable and provided in accordance with the preferences of the user. Since the blank is the -re sult of the activity of the two die members, the'disclosure will first present the characteristics of the die members.

The stationary die is disclosed more particularly in Figures 1 and 2, and indicated generally by S. This die is formed with a central circular cavity l5 of suitable depth and preferably tapered downwardly. The cavity is dev signed to receive the lower end of the heated stock, in this instance in the form of a billet of suitable length and of uniform diameter, preferably the diameter of the bottom of the cavity so that the latter acts to center the billet during the operation. The tapered form of the cavity serves the double purpose of permitting proper mushrooming of the billet and of so shaping the portion within the cavity-and which forms the hub of the gear blankas to permit ready removal of the completed forging from the dies after the forging action is completed.

The upper limits of cavity I5 is provided by a plane surface 16 extending normal to the axis of the die and annular with respect to the cavity. The radial width of this surface is determined by the needs for the diameter of the finished gear, the outer contour of this surface providing an oversized dimension of the gear surface known as the back of the gear, and hence this surface may be termed the back surface of the die; a sufiicient oversize is provided to permit the proper finishing of the outer end of the gear teeth from the blank.

Surrounding the back surface I6 and rising thereabove are an annular series of teeth I1, corresponding in number to the number of teeth of the gear. These teeth do not extend to the plane of surface I6 but extend upwardly to a point approximating the height of the crown of the finished outer end of the gear teeth. These teeth l'i lie outside of the dimensions of the tooth zone of the finished gear, and serve the dual purpose of providing the outer end wall of the teeth of the finished gearthe inner face ll of teeth I! providing the oversized faces of the ends of the gear teethand for this reason the faces l! are inclined outwardly at an angle to the axis of the die, the particular angle being that which is selected for the outer end of the gear teeth. The teeth I! are preferably arouateconvexin opposite directions as at with a small plane surface I1 at the crown of each tooth; a similar small plane surface [1 is located at the root of the teeth.

Since the teeth I! lie outside of the actual tooth zone of the finished gear, the length of the teeth is important only in connection with the service the teeth are to perform. As pointed out, the face l'l is a definite wall for the outer end of the gear tooth, while the surface of the body of a tooth l1 forms a wall of the flash zone of the dies. Consequently, the length of the teeth I! is such as will permit reception of the excess metal forming the flash, with the length, however, such that the flash space will not become filled in producing the blank. This is provided for the purpose of preventing the development of back pressure upon the metal of the gear zone of the dies through an attempt to confine the flash space. As shown, the periphery of the teeth I! in the direction of length of the tooth does not extend normal to the plane of face H but tends to enlarge away from face Il the angularity of surfaces 11 to a plane normal to the plane of face I! being such as to provide a more or less of a general similarity I to and a continuation of the direction of flow of the metal within the flash zone as is present in the gear zone of the die. As presently pointed out, the face I! perform a service in controlling the fibre characteristics of the gear zone.

The upper or movable die, indicated generally as M, is shown in detail in Figures 3 and 4, and co-operates with die S in the production of the blank. The die is provided with a central circular plane face 18 corresponding in diameter to the diameter of the bottom Wall of cavity l5 of die S, the latter wall together with face l8 providing the points of initial contact upon the ends of the billet. The face l8 forms the top of a zone from which radiate walls [9 active in producing the teeth of the gear zone, and hence correspond in number to the number of teeth of the gear. Each wall H) has its top surface I9 leading from the plane of face I8 at the desired angle for the root of a tooth of the gear zone, so far as the radial length of such zone is concerned; the face l9 is also of suitable width increasing slightly away from the inner end, thus conforming to the characteristics of the root zone of the gear teeth. The depth of the wall l9 provides the tooth depth of the gear zone, and is therefore of relief characteristic with respect to face Ili the side faces of the wall, indicated at I9 diverging toward the bottom of the relief and being slightly concave, terminating in a face l9 which forms the bottom of the relief but which face is active in the production of the crown zone of the teeth of the gear blank. As indicated, the inner end of the relief portion is in the form of an angular face 19 which is The face I! of die S has a similar contour to the contour of the relief portions of walls l9, and approximates the dimensions at the outer end of such relief portion. However, the face I! lies slightly beyond the outer end of wall I9, so that wall. 20 extends radially inward a slight distance beyond face Il A a result, a lateral jog of small radial length connects the recessed zone of walls 20 with the relief of the gear zone. In other respects, walls 20 and the relief portions thereof are designed to overlie the teeth I! of die S butbe spaced therefrom in the final position of the dies, the space providing the flash zone of the dies, the relationship being indicated in Figs. 6 and '7. As pointed out above, the radial length of this flash zone is such as to accommodate the complete flash excess of metal without resistance, so that, in practice, the length of such space is greater than is required to receive the flash. Hence, the flash itself provides practically little if any resistance to flow of metal, the presence of the jog assuring that the cavities of the gear zone will be properly filled, but without placing any undue strain upon the die members, so that the latter are usable through extended runs without need of re-conditioning.

The die members of Figs. 1 to 4 are shown as usable with a billet form of stock. When tubular stock is used, the die S carries a central core member 2| having a diameter corresponding generally to that of the axial opening of the stock, die member M carrying an opening 22 to accommodate member 2|, this arrangement being indicated in Fig. 5, which figure will. also indicate the general conditions present at the time when the forging action is about to begin, the ends of the stock being in contact with the respective dies but before the forging pressure begins. By considering the tubular stock B and the member 2| of this figure as replaced by solid billet of uniform diameter, the view will also illustrate the conditions present when the stock is of billet form and operating in connection with the dies of Figs. 1 to 4.

Assuming that the stock is of billet form a brief description of the die action is now presented:

As with forging operations generally, pressure exerted in opposite directions upon the ends of the billet will begin a mushrooming or swelling active in producing the zone of the inner end of the gear teeth.

The description of the die M, thus far, pertains to the zone of the die which serves to shape the gear zone of the blank. In addition, however, the die carries supplemental walls lying beyond the gear zone and positioned to overlie the tooth zone of die S, these walls being indicated at 20. These walls are alined radially with walls l9 and have similar configurations thereto, butlie on a plane sufficiently below those of the planes of walls H] as to provide a recess effect to the walls 20 as compared to walls I9, the depth of the offset being such as to provide the space for the reception of the flash of the blank. The effect produced is indicated in Figure 7, in which the body of die S is shown as an insertible die member in order to permit a clear disclosure of the contour of the flash zone which is provided through the recessed characteristic of walls 20.

of the billet at an intermediate point, this generally being midway of the length of the billet; since, as indicated in Fig. 5, the side wall of cavity I5 is out of contact with the billet, the general location of the swelling zone is unchanged in the present arrangement although the lower end of the billet is itself located within cavity 15. Hence, the swelling action will take place in the zone slightly above face It of die 8. As the swelling takes place, the diameter thereof increases, the metal for the increase being supplied from the interior of the billet. Such swelling does not disrupt the fibres, the latter simply moving outward as the swelling develops. Continued pressure will tend to extend the swelling into the zone of cavity E5 to fill the latter, but inasmuch as the location of the swelling zone has been established, the fact that cavity l5 fills does not change the location of the swelling zone. As the swelling operation is continued by the downward movement of die member M, the walls I9 move downward with the die. But inasmuch as face 16 of die S is fixed, that face sets up a resistance to an increase in the dimensions of the mushroom downwardly, with the result that the tendency of the increasing volume of metal in the mushroom is to move upwardly and thus in the direction of walls I9. The faces l9 are thus brought into contact with the upper portion of the mushroom, and since these faces extend radially in correspondence with the direction of the fibres of the mushroom, the opposing pressures set up by face 16 and faces l9 cause the latter to penetrate the mushroom in such manner as to tend to split the fibres which lie in the path of such faces I9 This begins the fashioning of the gear zone of the blank.

With faces [9 entering the upper portion of the mushroom and continuing to move downward within the mushroom, the portion of the latter penetrated is divided into individual zones, each having the continuity of fibres as in the mushroom; but inasmuch as the space occupied by the mushroom is made less by the presence of walls l9, the metal within these zones tends to flow upwardly toward the bottom of the relief, thus carrying the fibre arrangement in this direction. The metal also continues to flow outward both within these individual zones and below such zones, so that the portion below the faces I9 tends to prevent an excessive outward radial flow of metal within the zones, thus tending to produce this flow upward in the direction of the bottom of the relief referred to.

The outward flow of metal continues until it reaches faces I! of die S, each of which faces tends to check the radial flow outward and sets up a resistance such as to cause the entire relief zones of walls [9 to become filled, the angularity of faces Il tending to increase this upward movement of fibres, those at the surface following the curvature of the side walls l9, with the result that there is a tendency of fibres from the side face of one wall H! to intermesh with those of the side face of the adjacent wall within the relief cavity with the intermeshing taking place at the bottom of the cavityand therefrom in the crown zone of the gear tooth.

When the relief cavities of walls H) are completely filled, the further descent of the die M to complete the forging operation and obtain the dimensions of the blank, rovides an excess of metal. Since this metal must move from the interior outwardly, the value of the absence of resistance from the flash zone becomes apparent. The flow to the flash zone is from the outer zone of the relief cavities laterally through the small jog and into the flash space, the flow taking place by displacement within the relief cavities, but with the displacement ineffective to change the conditions which had been set up, since the displacing metal is being subjected to the same action as had been had by the previous metal, so that the texture conditions within the gear zone remain unchanged, although there has been a displacing of metal from such zone.

Consequently, the development has been such as to first fill the gear zone of the blank with a metal having its fibres arranged in an advantageous manner, and then to complete the dimensions of the blank by displacing from the filled zone an amount equal to the excess of stock, with the excess forming the flash, the latter being ineffective to change the fibre arrangement of the gear zone while substituting the displacing metal within the filled zone. Hence, that portion of the blank which constitutes the gear zone will be uniform in successive operations, as to texture characteristics, dimensions, etc., and the effect set up on the dies themselves will be minimum to thereby permit a pair of dies to operate for extensive runs before re-conditioning is required.

While the development of the flash has a tendency to affect a continuity of the fibres, this condition is present only with respect to the flash metal. Since the jog connection lies outside of the actual tooth zone of the finished gear, the continuity would be broken at the outer end of the tooth when finishing the gear, so that the change in continuity conditions set up in producing the flash does not materially affect the teeth of the finished gear, the variations set up within the tooth itself during the forging action remaining; being variations which tend in the direction of depth of the teeth and of intermeshing characteristic at the crown and root of the tooth, the strength of the latter is increased since the connections between adjacent fibres no longer extend in a" straight line or along the line of pressure, but are varied from such line with the fibres extending angular to the line of tooth pressure.

When the stock is tubular, the trends referred to are slightly varied, due to the fact that the supply of metal is more limited. Hence, during the forging, the action under the opposing pressures is varied in some respects. The trends may be enhanced, since the available metal at any instant is less and therefore the effects set up may be slightly accentuated--for instance, the rolling effect set up by the side faces I 9 may be more pronounced. However, the distinction in product is not so material as to affect the general characteristics pointed out above. As is obvious, the use of the tubular stock tends to reduce the wastage and is therefore of advantage so far as the cost of the gear production is concerned.

As will be apparent, the two dies approach to the desired extent to provide the desired dimension effect. The stock carries an amount of metal sufficient to supply the gear zone plus an excessto assure a filled gear zonethe excess being found in the flash zone, the latter lying wholly outside of the gear zone and therefore readily removed. The various active faces of the dies are dimensioned so as to provide the general characteristics of the finished gear, but are dimensioned to set up a slightly oversize characteristic in order that the desired finishing operations may take place with a minimum amount of wastage.

The blank thus formed is shown in Figs. 8 to 10. It presents the hub 23 (produced from cavity l5) the back 24 (produced by face IS), the gear zone and the flash zone, the latter having its outer contour presented as uniformly regular but which, in practice may be irregular in outline so far as radius is concerned, since the outer edge is actually without restraint and may therefore vary, the contour depending more or less upon the value of the flash.

As indicated in Fig. 9 the flash zone is elevated above'the gear zone this result being due to the recessed configuration of walls 20, the shoulder presenting the effect of the presence of the jog" produced as the dies approach their final positions preparatory to the beginning of the flash development. The gear zone presents the general configuration of the teeth 25, the flash zone 26 presenting generally similar outlines but with enlarged overall dimensions, and having somewhat of the appearance of a heading or shell tooth formation due to the fact that the flash is of uniform thickness.

In practice, the flash zone of the blankls emcijred' during the finldhlilmgglilgll thus leav- Tfigtfiiifclinedfacs'fi (produced by faces Il as providing the angular portion of the back of the finished gear. The gear may be finished in any suitable manner, as by machining, grinding, or by a coining operation, as may be desired, the finishing operation giving to the teeth the desired profiles, etc., the blank presenting sufficient metal to permit the profile shape to present a desired contour.

The blank may be provided from any preferred metal. Through the forging action provided as above explained, the stock is transformed into the blank in a form which can be readily finished, and with an assurance that the portion from which the finished gear is evolved is homogeneous as to texture. In addition, however, due to the manipulation of the metal during the forging operation, the tooth zone of the blank carries the additional factor of increased strength against cleavage under pressure, set up by the fact that the fibre continuity has become varied from the line of pressure on the tooth, and therefore tends to require more of the characteristics of an actual fibre break instead of a split or cleavage in presence of the tooth pressure conditions, since the tooth pressure is exerted across the grain rather than with the grain thus largely increasing the fibre-stress value of each tooth and rendering the latter less likely to be stripped in service.

The blank thus provided not only forms the basis for a gear construction of superior strength and more uniform heat treating ability, but produces the result with decreased cost per unit, since the wastage is materially reduced in amount, the finishing operations are simplified and therefore less expensive, in addition to which the forging operation can be provided with a minimum effect on the dies themselves, so that re-conditioning of the latter need take place only after extended runs. In addition, the usual effect presented by all forging operations of toughening the surface or skin of the forging, becomes of especial importance with the blank of the present invention, since this effect is present with the exposed surfaces of the blank and therefore upon the individual tooth structures, rendering these more resistant and of longer Wear char- 5O acteristic, the finishing operations required being of such nature that all or at least a portion of this skin or surface remains as a part of the finished tooth.

As will be understood, one of the controlling features of the present invention is that which sets up the condition of splitting the flash or excess metal formation to set up characteristics of controlled zonal flash conditions in the sense that the location of the flash is definitely controlled and is handled in such way as to not affect the development of the useful portion of the forging. In this way it is possible to control the building up of desired fibre stress values through manipulating the metal by pressures, etc., during forging, and to then take care of the excess metal without affecting the fibre arrangement which had been built up. In this respect the underlying features of the die formations may be found useful in forgings other than .those of the preferred embodiment of service in the bevel gear field, and such usage of the underlying features in other fields is contemplated within the purview of the present invention.

of forged bevel gear blank formation, together with one or more methods and means for producing the same, it will be understood that the disclosure is more or less illustrative, since the specific details of a blank and the die formations may differ rather widely to meet the various types, etc., of bevel gears placed in service. Betause of these variations, the specific form of the (116 faces may be varied to affect the pressure developments during the forging action, such variations being contemplated by the present invention, and I desire to be understood as reserving the right to make any and all such changes and modifications as may be found desirable or essential to meet the various exigencies arising in meeting individual developments, insofar as the same may fall within the spirit and scope of the invention as expressed in the accompanying claims when broadly construed.

Having thus described my invention, what is claimed as new is:

1. In the production of toothed bevel gear blanks, wherein the blank is formed by dropforging action of a pair of die members movable relative to each other to produce the forging action, and wherein the blank is formed from circular stock of uniform diameter, theme th gd formation radially external of the toothed zone by displacing of metal from the outer zones of the toothed zone under conditions substantially free from back pressure to preserve the fibre arrangement Within the toothed zone.

2. A die assembly for drop-forging operations comprising a pair of dies mounted for relative movement in the direction of a common axis, said dies having opposing configurations within a predetermined portion of the dies to produce a blank presenting an embryo formation for the finished product, said dies additionally having opposing configurations radially external of such predetermined portion and active to provide a controlled split fiash continuation of the blank with the fiash of a general shell formation.

3. A die assembly for drop-forging operations comprising a pair of dies mounted for relative movement in the direction of a common axis, said dies having opposing configurations within a predetermined portion of the dies to produce a blank presenting an embryo formation for the finished product, said dies additionally having opposing configurations radially external of such predetermined portion and active to provide a controlled split flash of a general shell formation, the fiash development being substantially ineffective to set up material back pressure upon the metal of the predetermined portion.

4. A die assembly for drop-forging operations comprising a pair of dies mounted for relative movement in the direction of a common axis, said dies having opposing configurations within a predetermined portion of the dies to produce a blank presenting an embryo formation for the finished product, said diesadditionally having,

While I have thuspresented a preferred form opposing configurations radially external of such predetermined portion and active to provide a controlled split flash continuation of the blank with the flash of a general shell formation, the flash metal being provided from the metal of the peripheral zone of the predetermined portion by continuing to develop the formation of the predetermined portion to thereby maintain the developing characteristics of such portion regardless of the flash volume.

5. In the production of toothed bevel gear blanks, a pair of dies mounted for relative movement in the direction of a common axis, said dies having opposing configurations effective to produce the toothed zone forming the embryo formation for the finished bevel gear, said dies additionally having opposing formations radially external of such toothed zone with such latter formations active to provide a controlled split flash continuation of the blank radially external of the toothed zone and of a general shell formation.

6. In the production of toothed bevel gear blanks, a pair of dies mounted for relative movement in the direction of a common axis, said dies having opposing configurations effective to produce the toothed zone forming the embryo formation for the finished bevel gear, said dies additionally having opposing formations radially external of such toothed zone with such latter formations active to provide a controlled split flash continuation of the blank radially external of the toothed zone and of a general shell formation, the flash space and toothed zone space being in open communication with the communication including a lateral jog of small dimensions, whereby the flash development will be substantially ineffective to disturb the developed characteristics of the toothed zone of the blank.

7. A die assembly as in claim characterized in that the opposing configurations of the toothed zone include spaced walls on one of the dies extending radially with the walls presenting crosssectional contours effective to provide the root, sides and crown of the teeth of the toothed zone during relative movement of the dies by action of the walls upon the developing mushroom of the stock, and with the walls active to separate the mushroom formation into developing individual zones while maintaining fibre continuity and to manipulate the metal of the developing zones to vary the fibre continuity to extend angular to the line of service tooth pressure of the finished gear to thereby increase the fibre stress value of the teeth.

8. A die assembly as in claim 5 characterized in that the opposing configurations of the toothed zone include spaced walls on one of the dies extending radially with the walls presenting crosssectional contours effective to provide the root, sides and crown of the teeth of the toothed zone during relative movement of the dies by action of the walls upon the developing mushroom of the stock, and with the walls active to separate the mushroom formation into developing individual zones while maintaining fibre continuity and to manipulate the metal of the developing zones to vary the fibre continuity to extend angular to the line of service tooth pressure of the finished gear to thereby increase the fibre stress value of the teeth, said die having additional walls externally of the toothed zone Walls and radially alined therewith, said additional walls having generally similar cross-sectional contours to the toothed zone walls but depressed with respect thereto and operative in the formation of the flash zone of the blank.

9. A die assembly as in claim 5 characterized in that the opposing configurations of the toothed zone include spaced walls on one of the dies extending radially with the walls presenting crosssectional contours effective to provide the root, sides and crown of the teeth of the toothed zone during relative movement of the dies by action of the walls upon the developing mushroom of the stock, and with the walls active to separate the mushroom formation into developing individual zones While maintaining fibre continuity and to manipulate the metal of the developing zones to vary the fibre continuity to extend angular to the line of service tooth pressure of the finished gear to thereby increase the fibre stress value of the teeth, said die having additional walls externally of the toothed zone walls and radially alined therewith, said additional walls having generally similar cross-sectional contours to the toothed zone walls but depressed with respect thereto and operative in the formation of the flash zone of the blank, the configurations of the second die including radial teeth co-operative with the walls of the flash zone of the first die to provide the shell flash cavities of the die assembly.

10. A die assembly as in claim 5 characterized in that the opposing configurations of the toothed zone include spaced walls on one of the dies extending radially with the walls presenting crosssectional contours effective to provide the root, sides and crown of the teeth of the toothed zone during relative movement of the dies by action of the walls upon the developing mushroom of the stock, and with the walls active to separate the mushroom formation into developing individual zones while maintaining fibre continuity and to manipulate the metal of the developing zones to vary the fibre continuity to extend angular to the line of service tooth pressure of the finished gear to thereby increase the fibre stress value of the teeth, said die having additional walls externally of the toothed zone walls and radially alined therewith, said additional walls having generally similar cross-sectional contours to the toothed zone walls but depressed with respect thereto and operative in the formation of the flash zone of the blank, the configurations of the second die including radial teeth co-operative with the Walls of the flash zone of the first die to provide the shell flash cavities of the die assembly, the inner faces of the teeth of the second die being inclined to the die axis and serving as an outer defining wall of the toothed zone in completing the outer end zone of the teeth of the toothed zone of the blank.

11. A die assembly as in claim 5 characterized in that the opposing configurations of the toothed zone include spaced walls on one of the dies extending radially with the walls presenting crosssectional contours efiective to provide the root, sides and'crown of the teeth of the toothed zone during relative movement of the dies by action of the walls upon the developing mushroom of the stock, and with the walls active to separate the mushroom formation into developing individual zones while maintaining fibre continuity and to manipulate the metal of the developing zones to vary the fibre continuity to extend angular to the line of service tooth pressure of the finished gear to thereby increase the fibre stress value of the teeth, said die having additional walls externally of the toothed zone walls and radially alined therewith, said additional walls having generally similar cross-sectional contours to the toothed zone walls but depressed with respect thereto and operative in the formation of the flash zone of the blank, the configurations of the second die including radial teeth co-operative with the walls of the flash zone of the first die to provide the shell flash cavities of the die assembly, said die teeth and flash zone walls being relatively arranged to provide open communication between the flash and toothed zones by a small lateral jog.

12. A forged bevel gear blank having its fibre structure extending in generally radial direction of the blank to thereby present the fibre structure of each tooth zone as generally similar to that of the remaining tooth zones and with the fibre structure of 'each tooth zone having the general direction of length of its fibres within the zone as extending substantially normal to the direction of tooth pressure application during service of the finished gear.

l3.- A forged bevel gear blank having its fibre structure extending in generally radial direction of the blank to thereby present the fibre structure of each tooth zone as generally similar to that of the remaining tooth zones and with the fibre structure of each tooth zone having the general direction of length of its fibres Within the zone as extending substantially normal to the direction of tooth pressure application during service of the finished gear, said blank also presenting the forging flash as radially external of the:tooth zone and as of general shell formation conforming generally to the cross-sectional contour of the teeth of the toothed zone to thereby place the flash as located in a zone lying outside of the circumference of the blank structure used in producing the finished gear.

FRANK V. ELBERTZ.

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