US3592040A

US3592040A - Device for forging crankshafts and the like

Info

Publication number: US3592040A
Application number: US754658A
Authority: US
Inventors: Gabriel Ruget
Original assignee: Compagnie des Ateliers et Forges de la Loire SA
Current assignee: Compagnie des Ateliers et Forges de la Loire SA
Priority date: 1967-09-07
Filing date: 1968-08-22
Publication date: 1971-07-13
Anticipated expiration: 1988-07-13
Also published as: ES357440A1; GB1205063A; CS153476B2; FR1543365A; NL6812652A; SE361422B

Abstract

A device for forging crankshafts having a plurality of throws disposed in different angular positions by carrying out the method consisting in upsetting one portion of a cylindrical initial blank either plain or formed with swellings, by exerting two oppositely directed efforts on the zone heated to the forging temperature, and by applying an effort perpendicular to the aforesaid oppositely directed efforts, in offsetting the intermediate portion of the initial bar. The offset portion constituting a crankpin, and the upset portions constituting two cheeks of the crankshaft to be forged.

Description

United States Patent [72] Inventor Gabriel Ruget St. Etienne, France [21 1 Appl. No. 754,658 [22] Filed Aug. 22, 1968 [45] Patented July 13,1971 [73] Assignee Compagnle Des Ateliers Et Forges De La Loire St. Cbamond, Flrrnlny, St. Etienne, Jacob-Holler Paris, France [32] Priority Sept. 7, 1967 [3 3] France [3 l 1 120,268

[54] DEVICE FOR FORGING CRANKSIIAFIS AND THE LIKE 7 Claims, 4 Drawing Figs.

[52] 0.8. CI. 72/399, 29/6, 72/403 [51] Int. Cl B21j 9/02 [50] Field of Search 72/399, 403, 383; 29/6 [56] References Cited UNITED STATES PATENTS 336,604 2/1886 Tweddell 100/269 1,338,335 4/1920 Smith 72/383 2,534,613 12/1950 Meley 29/6 2,747,253 5/1956 ConchOn. 29/6 2,959,840 11/1960 Albers 29/6 FORElGN PATENTS 1,082,482 5/1960 Germany 29/6 757,526 9/1956 Great Britain 29/6 Primary Examiner-Charles W. Lanham Assistant Examiner-Gene P. Crosby Attorney-Wenderoth, Lind and Ponack PATENIEU JULI 31971 3, 592.040

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PATENTED JUL 1 3 I97! SHEET 3 [IF 3 DEVICE FOR FORGING CRANKSHAF'IS AND THE LIKE The present invention relates to a device for forging notably but not exclusively crankshafts having a plurality of throws disposed in different angular positions, the forging operation being carried out directly, without malleting. It is the essential object of this invention to provide means capable of producing forged pieces having a continuous grain structure, wherein the fiberlike flow lines of the grain structure are directed parallel to the outer surface of the pieces, the axial zone of the original ingot merging in the mean fiber and the peripheral zone remaining close to the surface. Moreover, the device according to this invention is so designed that the necessary forging power values are considerably greater than those required for simply forging the metal, so that high-precision workpieces can be obtained, i.e. workpieces wherein the extra thickness left on the forged blanks for the final machining operations is extremely thin. The results deriving from this specific grain structure are completed by the stamping of the workpieces, thus providing a combination of the two processes which will be termed hereinafter fibrostamping."

Firstly, the hitherto known forging methods and apparatus will briefly be discussed.

To make a crankshaft, the initial blank consists of a cylindrical bar formed with swellings separated by constrictions. As a rule, the swellings are to constitute the broader portions of the workpiece, ie the portions of which the shape is altered, the constrictions constituting the eccentric or concentric narrower portions of the workpiece. The initial ingot, billet, bar or blank may also consist of a piece of metal having a plain surface throughout its length.

The crankshaft of a multicylinder engine consists of a plurality of throws on a same shaft line, which, when seen in the direction of this line, are angularly offset in relation to each other by values depending notably on the number of cylinders. A partially forged crankshaft consists of one portion of the above-described bar having as extensions a number of throws disposed at well-defined angular positions. The axis of this bar and the common shaft axis of these throws are coincident with each other and constitute the longitudinal axis of the blank.

FIG. 1 of the attached drawings illustrated separately a crankshaft throw as seen in diagrammatic section taken along a plane containing the longitudinal axis of bearings p and p (axis Ox) and the crankpin axis m. The intersection of the section plane and the transverse plane of symmetry of the throw defines the axis Oy. A complete throw is forged in a single operation by synchronizing three forging thrusts, namely two main equal and opposed upsetting thrusts R, and R, directed along the axis Ox while a third thrust D is directed along the axis Oy and intended to offset the crankpin. The simultaneous application of these three forces is attended by a continuous flow of the metal of which the fibers are directed parallel to surface of the workpiece, thus reducing considerably the surface defects and increasing the strength of the final products.

The radial cheeks may be upset by allowing the metal to assume freely its contour and the plates, which in this case have an oval cross-sectional configuration (substantially that of a very slightly eccentric ellipse), are subsequently brought to their final shape by a long machining operation.

Preferably, a procedure is adhered to whereby the cheeks thus upset are eventually each contained in a two-part die adapted to impart thereto a shape approaching as much as possible the finished shape; thus, the weight of the necessary metal as well as the subsequent machining steps are reduced. It is extremely advantageous to perform a fibrostamping" of the cheeks according to this method, but in this case the forging power available must be consistent with the desired shape, the former increasing of course as the latter departs from the shape naturally assumed by the metal. Moreover, in this case a considerable force must be exerted against the two die halves for balancing the thrust of the metal which increases with the upsetting pressure.

Up to now, the longitudinal axis of the known :ipparr u-z operating according to this prior method, which axis is merged in the longitudinal axis of the blank or billet during the forging operation, was always disposed horizontally. On the other hand, these apparatus have certain common features; thus, they comprise a central tool, to which no longitudinal movement is imparted, which transfers the crankpin to its eccentric position, and on either side of this central tool, a pair of Iongitudinally movable cradles carrying the upsetting dies and responsive to two sets of hydraulic actuators fed with fluid under pressure from a central distributor also supplying fluid to the bending actuators. Therefore, these apparatus are characterized by a certain symmetry with respect to a plane perpendicular to the longitudinal axis, which contains the initial axis.

To protect the central tool from lateral efforts likely to compromise its proper operation, the forces resulting from the metal upsetting during the simultaneous compression of the two cheeks of a throw must necessarily act symmetrically on this tool. Therefore, the movements of the aforesaid two cradles supporting the end dies are mutually responsive and linked to the crankpin-making radial movement; the general solution consists in synchronizing the three movements. This involves the use of servo means of mechanical character (such as slip ramp, rack-and-pinion devices, etc.) or preferably of hydraulic type (differential actuators, etc.) of which the use is frequently delicate, especially if the two checks of a same throw are not identical or if the temperature of the metal in the two deformed zones is not strictly the same. This apparently simple arrangement requires a costly set of auxiliary equipment for coordinating all the functions contemplated for forging the crankshaft.

Although all the known apparatus are based on the same operating principle they can broadly be divided into two sections, according to the manner in which the initial blank is introduced into the apparatus.

ln some devices the forging zone can be reached only through a passage provided in the longitudinal axial direction of the apparatus. The blank is supported at one end in overhanging relationship by means of a socket and the assembly balanced by counterweights and a crew of workmen is handled by means of a traveling crane. To introduce the blank into the device, a horizontal movement of translation must firstly be impressed thereto in a direction parallel to its major dimension, this constituting a delicate and slow operation further complicated by the horizontal position of the bar of which the plastic zone tends sag by gravity. Now gravity may be so important, when the hot portion of the blank is the central portion, that two traveling cranes are then necessary for laying the blank into a cradle portion provided to this end with slideways.

With this arrangement handling operations are made more complicated and more or less retarded, thus causing in certain cases temperature differences from one forging operation to another, but on the other hand it is advantageous in that, considering the forging pressures implemented, its permits the construction of forging apparatus of relatively moderate weight. In fact, the cradles supporting the dies and constituting bearing points for the die clamping actuators consist of closed frame structures having a considerable strength but reasonable dimensions. The major advantage of this arrangement is therefore its relative light weight which reduces its cost.

In order to simplify handling operations the die-supporting cradles of the second type of forging apparatus are open to permit a free access to the forging zone from above. Thus, the blank can be laid directly into the dies after receiving any suitable movement of translation, which may be as simple as desired, by using for example two traveling cranes for reducing the sagging of the plastic zone. Under these conditions the same production can be obtained by using a limited personnel, whereby manufacturing cost is reduced considerably. On the other hand, for bringing into play the same die clamping forces as in the preceding arrangement, that is, for obtaining the same forging precision, the frame structures must be considerably larger and heavier, for they are flexion stressed due to the gooseneck shape of the cradles. Although the cost for operating such equipment is somewhat lower, the expenses necessary for installing it are considerably higher.

It is the essential object of the present invention to provide a relative arrangement of the elements which aims at avoiding the inconveniences briefly set forth herein-above which characterize known apparatus; with this invention, the mutual subservience of the offsetting and upsetting tools is simplified or even eliminated completely, the weight of the press used for this purpose being comparable with that of the lighter devices, but on the other hand this press has the same handling possibilities as the presses in which the forging zone is completely accessible from above.

The device according to the present invention is based on the known method of forging crankshafts throw by throw from a cylindrical billet bar, or blank, whether plain or formed with swellings, and is characterized in that the central tool performing the offsetting of the crankpins is not fixed but displaceable parallel to the longitudinal axis of the device which merges in the billet axis during the forging operation, in that said longitudinal axis is disposed vertically, and in that the joint plane of the die sections is parallel to or coincident with the plane formed by the longitudinal axis of the device and the crankpin offsetting direction.

According to a specific form of embodiment of this invention, the device is designed according to the so-cailed "inverted presses technique and comprises a fixed crossmember or beam enclosing the actuators providing the force necessary for upsetting the cheeks of the throws, said actuators being adapted to move a yoke rigid with movable vertical columns of the press; a movable crossmember secured to and adapted to drive said columns; two pairs of die sections disposed the one on said fixed crossmember and the other on said movable crossmember and adapted to hold against motion the bar or billet to be forged at points thereof which are to constitute the journals upon completion of the forging operation and which, during this operation, give the required shape to the cheeks; two pairs of actuators adapted to operate said die sections by clamping same during the forging operation, the line of action of said actuators being perpendicular to the offsetting direction; another crossmember movable in its longitudinal direction but constantly horizontal, which is adapted to receive the central tool comprising a pair of swages operated by other actuators and adapted to clamp the bar or billet at a point which, upon completion of the forging operation, constitutes the crankpin, and actuators adapted, when said swages are closed, to produce the effort necessary for bending the initial billet or bar and offset the central tool with the elements contained therein. According to this invention, cavities or passages are formed respectively in the upper and lower crossmembers to permit the introduction of the billet vertically from the top of the device.

The lateral movements of the die sections and movable crossmember are kept to the minimum values by carefully designing the column guiding means, for example by causing each column to be guided at two relatively remote points thereof, whereby the forging precision is improved and the press can be subjected without any damage to eccentric efforts, or efforts having a horizontal component.

According to this invention, the plane of the plane of the die sections is parallel to or merged in the plane containing the longitudinal axis of the device and the offsetting direction, the joint plane passing, for a given throw, through the journal axis and the crankpin axis. With this arrangement relatively complicated shapes can be obtained with greater facility by using die members having the simplest possible impressions.

According to another feature of this invention the movable crossmember carrying the central tool is guided by the press columns and by links pivotally connected to belicrank levers responsive to a fluid-operated actuator in order to balance the weight of said crossmember and the central bending tool, and also to position said crossmember in the longitudinal direction. As an alternative, this guiding action may be obtained by resorting only to tie rods, bellcrank levers and said balancing actuator, or also by using slideways rigid with the fixed beam.

According to a further modification of this invention the columns and the upper crossmember may be fixed and rigid with a beam disposed preferably at the lower portion of the device and containing the actuators operatively connected to a movable crossmember.

Other features and advantages of this invention will appear as the following description proceeds with reference to the accompanying drawings illustrating diagrammatically by way of example a typical form of embodiment thereof, it being understood that various modifications may be brought thereto without departing from the spirit and scope of the invention. in the drawing:

W6. 2 is a longitudinal section showing the device of this in-' vention, the section being taken along the plane of symmetry perpendicular to the offsetting direction;

FIG. 3 is a section taken through a plane disposed at right angles to the plane of FIG. 2 and containing the axis of two columns and a piston, and

HG. E is a plane view from above showing the portion of the device which is designed for offsetting the cranltpins.

Referring to the drawing it will be seen that the device according to this invention is designed like an inverted press. The fixed crossmember or beam ll encloses a pair of actuators (fluid-actuated cylinder-and-piston units) 6 producing the whole of the upsetting force and acting upon a yoke 10 rigid with movable columns 9. The movable crossmember 2 is secured to and driven by these columns. Both crossmembers l and 2 carry die sections 3a and 3b on the former, and 4a and 4b on the latter, respectively. These die sections are adapted to hold the bar against motion at points thereof which are to constitute the journals upon completion of the forging operation, these die sections imparting the desired shape to the cheeks during the forging operation. To this end they are connected and operated by two pairs of actuators 7 and 8 respectively, which hold them closed during the forging operation, the line of action of these actuators being perpendicular to the offsetting direction.

The joint plane of the die sections is parallel to or merged in the plane formed by the long tudinal axis of the device and the offsetting direction; for a given throw the joint plane will thus contain the axis of the journals and the crankpin axis. This arrangement constitutes the easiest way of obtaining complicated shapes by using die sections having the simplest possible impressions. The longitudinal axis of the device is vertical in order to facilitate handlings. To permit the introduction of blanks or billets in a vertical position from the top of the apparatus, apertures 12 and ii are formed in the upper and lower crossmembers, respectively, these apertures permitting the passage of the blanks. This arrangement is also advantageous in that the end die sections can be supported by frame structures or relatively light construction.

Eccentric efforts or efforts comprising a horizontal component may be exerted on the press, and in order to obtain an accurate forging the lateral movements of the die sections and of the movable crossmember 2 must be as small as possible; therefore, the columns must be guided with the maximum efficiency, for example by guiding them at two relatively remote points.

The crankpins are offset by using a central bending tool housed in the crossmember 5 adapted to move longitudinally but constantly held in a substantially horizontal position.

This requirement may be met by guiding this crossmember 5 by means of columns 9 and links 17 pivotally connected to bellcrank levers iii in order to balance the weight of the crossmember and also of the bending tool M contained therein, and to position this crossmember longitudinally. The bending tool may also be guided by using only tie rods, bellcrank levers and the balancing actuator, or by using to this end slideways rigid with the fixed crossmember or any other suitable means. The cross member 5 guides the transversely movable member containing the swages 13a and 13b. These swages are adapted, under the control of actuators l5 and 16, to clamp the bar at a point which, upon completion of the forging operation, will constitute a crankpin. After these swages have been closed, the actuators provide the force necessary for bending the blank and offset the sliding member 14 and the tools contained therein. These actuators may if desired react against the columns 9 as shown in the attached drawing, but alternate- 1y they can also bear against the fixed and movable cross members, or against slideways provided to this end.

It will readily occur to anybody conversant with the art that this arrangement is described by way of example only; thus, the columns and the upper crossmember may be fixed and rigid with a beam disposed preferably at the lower portion, said beam containing the actuators operatively connected to a movable crossmember. The relative arrangement of the elements may be modified and the forms of embodiment adapted to constructional requirements or possibilities, and the number and lines of action of the actuators may be modified at will.

The conception, specific of the present invention, of the bending device, is such that this device can assume at any time and under the influence of but a very moderate longitudinal effort a position of equilibrium between the two cradles supporting the upsetting die sections, for it can move freely while remaining parallel to itself. Thus, this specific feature not only makes it useless to provide servo means for controlling the movements of the upsetting tools but it also permits of dispensing with the hitherto symmetrical design of apparatus of this type; thus, instead of a fixed central tool disposed between two similar cradles traveling in opposite directions, a single cradle may be held against motion and incorporate all the control actuators in order to minimize the weight of the other cradle.

The forging of a complete crankshaft by using a device of this type will now be described by way of example.

The original bar or blank, whether plain or machined with swellings and constrictions, is heated in a vertical position, preferably in a localized action furnace, for example an electrical induction furnace. When the zone to be forged has attained the requisite temperature a traveling crane grips the upper end of the bar or blank, so that the latter is suspended vertically and can thus be introduced, with or without guiding, into the press. Gravity will not tend to bend the heated zone and although a single traveling crane is used for handling the bar it is not necessary to balance the bar. Advantageously, the throw located at the top of the bar will be forged first, and then all the successive throws following the first throw in the downward direction are forged. Before each forging operation a bar section is heated, and then the bar is rotated so as to cause the fixed bending direction and the direction of the throw to merge in each other. This rotation about a vertical axis may be produced either in the device or during the heating step. Thus, at an intermediate stage of the manufacture a number of forged throw are formed in the upper portion of the blank, these throws having their final angular position prolonged by a depending rectilinear bar. Therefore, the upper aperture 12 of crossmember 2 permits the passage of a forged crankshaft and the aperture 11 formed in the fixed beam permits only the passage of the initial cylindrical blank or billet. Since the diameter of the second aperture is considerably smaller than that of the first one, relatively large actuators can be housed in this beam and the forging forces brought into play may be relatively great. By retracting laterally the bending device it is possible to upset a plate on a rectilinear bar or at any point along a crankshaft, after the corresponding die sections have been properly positioned.

The advantages resulting from this specific arrangement are due mainly to its two independent features, namely, on the one hand, the mutual subservience of the forging movements is eliminated for the bending device is longitudinally movable, and on the other hand handling operations are facilitated and made possible by using a reduced personnel because the longitudinal axis of the device is disposed vertically instead of horizontally as in prior art arrangements.

Since in the arrangement according to this invention the offsetting tool is longitudinally movable the upsetting efforts exerted on either side of this tool balance each other for, if they are unequal, they involve a translation of the tool. Thus, the hitherto necessary synchronization of the two upsetting movements is avoided.

Moreover, the subservience of the bending and crushing movements can be avoided by adopting the following sequence of steps for forging a throw. Firstly, an upsetting pressure insufficient for completely crushing the plates or cheeks is produced in the actuators and, at the same time, the bending actuators are supplied with fluid under a pressure such that they can theoretically exert a force slightly greater that the necessary offsetting effort. At the end of this operation, the complete bending and a partial upsetting are obtained. The second forging step begins; it consists in exerting the whole of the upsetting force so that the metal will fill completely the die sections. This sequence of steps (each step being discontinued when the tools concerned have completed their stroke, that is, when the desired deformation is obtained), permits of avoiding the difficulties resulting from the subservience of the movements and from the devices necessary therefor. To sum up, the known machines, through an equipment associated therewith, cause a deformation of the blank which is constantly controlled by a longitudinal or transverse displacement to prevent the central tool from being subjected to asymmetrical efforts. As contrasted thereto, the operation of the device according to the present invention is simplified because an effort theoretically slightly or very considerably greater than the reaction force is exerted in two directions instead of three, and only the termination of the resulting deformations has to be controlled; it is no more necessary to use servo means responsive to the machine for controlling the movements. This method is applicable because practical experience clearly teaches that each effort (offsetting or upsetting) varies moderately as a function of the concatenation of these operations and preserves, all other factors remaining unchanged, a substantially constant value, provided however that the first step be complete before the next one begins.

Finally, with this arrangement the necessary number of upsetting actuators or cylinder and piston units is practically halved since one of the cradles is fixed and the other is movable in relation to the former. This advantage is attended by a substantial reduction in the weight of the device and also of its cost. Moreover, one of the cradles becomes a simple crossmember having smaller overall dimensions and the forging zone nearer to one end is more accessible.

During the first bending step the deformation applied to the metal is such that its grain is oriented in a direction to cause the stress subsequently exerted on the final workpiece to be constantly applied in the longitudinal direction of the fiberlike flow lines, in order to increase the strength of the workpiece. As the unitary power brought into play during the second phase is at least 5 times greater than that necessary for freely forging the same metal, the latter is upset with force into the registering die sections which will thus very accurately shape the metal as required. During this last phase the cheeks of the throw are practically stamped. It is very advantageous to so calculate the dimensions and power requirements of the apparatus that it can produce completely, by fibrostamping, crankshafts of small and medium size, mostly forged, so as to partially stamp only the cheeks or plates of the largest crankshafts which are less frequently manufactured.

Thus, the most frequently required machining operations are reduced or eliminated due to the power value brought into play and also to the specific joint plane utilized. In fact, if the lateral cheeks and more particularly the heels of the flanges @QWE have concave shapes to which balance-weights have to be secured, these flanges have in many instances for their plane of symmetry the plane containing the axis of the journals and crankpin axis; as a rule, it is easier to obtain as a rough-forged piece a shape very close to the desired one by adopting this plane as the joint plane of the die sections. If such shapes had to be obtained through the known arrangement (with the joint plane perpendicular to the offsetting direction) die sections of complicated configuration must be used which are adapted to receive detachable elements so that the piece can be removed from the die impression.

This arrangement is also attended by many advantageous features due to the vertical position of the longitudinal axis of the device and of the blanks during the forging operations.

These blanks are transfered in a position such that gravity can neither bend their line of shaft not open previously forged throws, even when they are heated to the forging temperature.

All handling operations can be performed by using a single traveling crane without holding the bar in an overhung position, and without having to direct and balance this bar during the translation thereof. It is as delicate to move the blank parallel to its axis when the latter is horizontal, as simple to perform this operation when the axis is disposed vertically; to introduce the bar into the forging device, the bar is allowed to descend as in a well; by using a traveling crane adapted to this purpose this operation is not attended by any complicate guiding problem. The handling of the bar is greatly simplified and can be performed by a reduced crew, thus reducing the final cost of the crankshafts.

Nevertheless, these simplifications are obtained by maintaining the shape of a closed frame structure for the cradles containing the die sections. Handling is simplified, as already explained hereinabove, but the device itself is light in weight and its manufacturing cost is relatively low. Moreover, the reduced aperture provided in the fixed beam facilitates the positioning and dimensioning of the fluid-operated actuators; thus, extremely high forging power may be brought into play while reducing the extra thickness of forged workpiece and therefore the metal to be removed by machining.

The device according to this invention is remarkably well adapted for forging crankshafts and leaving only moderate extra metal thereon for subsequent machining steps. The method utilized to this end imparts a continuous grain to the workpieces, the throws are formed directly with their correct angular positions, whereby malleting can be dispensed with. This result is obtained by using a relatively light device, free of complicated servo means for controlling the movements, and which can be operated by a reduced crew. But in addition, by retracting the bending mechanism, the device can rapidly be transformed into a press having a high forging power and a relatively long stroke, since only one cradle is movable. It can be used as an ordinary inverted press and is capable of comparable production rates; however, it can also be used for forging plates at any desired point along shafts of relatively great length and diameter; in this case the bar is introduced from the top through the upper aperture, as in the case of a crankshaft blank. Finally, workpieces of more complicated configuration can be forged, such as those requiring the use of die sections strongly pressed against each other; in this case the power of actuators 7 or 8 constituting two presses acting in directions at right angles to the direction of action of the main press will be used.

Although the present invention has been described in conjunction with preferred embodiments, it crossmember be understood that modification and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and appended claims.

What l claim is:

l. A device designed more particularly but not exclusively for forging crankshafts havin a pluralit of throws disposed in different angular positions a ong the s aft line by using the known method consisting in upsetting one portion of a cylindrical initial blank possibly formed with spaced swellings intended to constitute the checks of the forged crankshaft, by exerting two oppositely directed efforts on the blank zone heated to forging temperature and, by applying another effort perpendicular to said two efforts, in offsetting the intermediate portion of the initial blank, said offset portions being intended to constitute a crankpin of the forged crankshaft, the thus upset portions subsequently constituting the two cheeks of each throw of the crankshaft, said device comprising a central tool for offsetting said crankpin portion of the throw, a first crossmember supporting said central tool, said central tool being movable in a direction perpendicular to the longitudinal axis of the device whereas the first crossmember supporting said central tool is movable in a direction parallel to the longitudinal axis of the device during the forging operation, movable crossmember and a fixed crossmember, each movable and fixed crossmember supporting a die section adapted on the one hand to hold said blank against motion at points thereof which are to constitute the journals upon completion of the crankshaft forging operation, and on the other hand to impart the desired shape to the cheeks during the forging operation, and a pair of actuators associated with each movable and fixed crossmember the line of action of said actuators being perpendicular to the offsetting direction, wherein the joint plane of said die sections is parallel to the longitudinal axis of the device and to the offsetting direction, said joint plane containing, for a given throw, the axis of the journals and the crankpin axis, whereby complicated shapes can be obtained by using die sections having the simplest possible impressions.

2. A device as set forth in claim 1, wherein said joint plane of said sections contains the longitudinal axis of the device and the offsetting direction.

3. A device as set forth in claim 1, wherein the longitudinal axis of the device is disposed vertically, and passages are formed in said movable and fixed crossmembers to permit the passage of the blank introduced from the top of the device, whereby frame structures of relatively light construction can be used for supporting the end die sections.

4. A device as set forth in claim l, wherein said fixed crossmember contains a first set of actuators delivering the force necessary for upsetting the cheeks of each crankshaft throw, said device being provided with vertical movable columns, said device comprising a yoke rigid with said columns, and adapted to be operated by said first set of actuators, said movable crossmember being rigid with said columns; said pair of actuators with each crossmember adapted to operate said die sections and to keep them tightly closed during the forging operation, said first crossmember fixed against horizontal movement and carrying said central tool, said central tool comprising a pair of swages responsive to a control actuator for clamping the blank at a point which, in the final forged member, is to constitute the crankpin, and other actuators adapted, when said swages are closed, to produce the effort necessary for bending the initial blank and to offset said central tool and the elements contained therein.

5. A device as set forth in claim 4, wherein said movable and fixed crossmembers have apertures respectively to permit the introduction of the blanks in a vertical position and direction from the top of the device.

6. A device as set forth in claim 4, wherein said first crossmember is guided by the columns and also by a link pivotably connected to bellcrank levers responsive to actuators for balancing the weight of the first crossmember and the central tool and for vertically positioning said central tool.

7. A device as set forth in claim 4, in which said first crossmember is guided by means of slideways rigid with said fixed crossmember.

Claims

1. A device designed more particularly but not exclusively for forging crankshafts having a plurality of throws disposed in different angular positions along the shaft line by using the known method consisting in upsetting one portion of a cylindrical initial blank possibly formed with spaced swellings intended to constitute the cheeks of the forged crankshaft, by exerting two oppositely directed efforts on the blank zone heated to forging temperature and, by applying another effort perpendicular to said two efforts, in offsetting the intermediate portion of the initial blank, said offset portions being intended to constitute a crankpin of the forged crankshaft, the thus upset portions subsequently constituting the two cheeks of each throw of the crankshaft, said device comprising a central tool for offsetting said crankpin portion of the throw, a first crossmember supporting said central tool, said central tool being movable in a direction perpendicular to the longitudinal axis of the device whereas the first crossmember supporting said central tool is movable in a direction parallel to the longitudinal axis of the device during the forging operation, movable crossmember and a fixed crossmember, each movable and fixed crossmember supporting a die section adapted on the one hand to hold said blank against motion at points thereof which are to constitute the journals upon completion of the crankshaft forging operation, and on the other hand to impart the desired shape to the cheeks during the forging operation, and a pair of actuators associated with each movable and fixed crossmember the line of action of said actuators being perpendicular to the offsetting direction, wherein the joint plane of said die sections is parallel to the longitudinal axis of the device and to the offsetting direction, said joint plane containing, for a given throw, the axis of the journals and the crankpin axis, whereby complicated shapes can be obtained by using die sections having the simplest possible impressions.

4. A device as set forth in claim 1, wherein said fixed crossmember contains a first set of actuators delivering the force necessary for upsetting the cheeks of each crankshaft throw, said device being provided with vertical movable columns, said device comprising a yoke rigid with said columns, and adapted to be operated by said first set of actuators, said movable crossmember being rigid with said columns; said pair of actuators with each crossmember adapted to operate said die sections and to keep them tightly closed during the forging operation, said first crossmember fixed against horizontal movement and carrying said central tool, said central tool comprising a pair of swages responsive to a control actuator for clamping the blank at a point which, in the final forged member, is to constitute the crankpin, and other actuators adapted, when said swages are closed, to produce the effort necessary for bending the initial blank and to offset said central tool and the elements contained therein.