US3650143A

US3650143A - Apparatus for forging crankshafts and the like

Info

Publication number: US3650143A
Application number: US841272A
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: 1968-07-19
Filing date: 1969-07-14
Publication date: 1972-03-21
Anticipated expiration: 1989-03-21
Also published as: SE371589B; JPS4924337B1; GB1229539A; DE1936012C2; DE1936012A1; DK146499B; NL159301B; NL6911154A; DK146499C; CS184303B2

Abstract

Improvement in apparatus for forging crankshafts and like workpieces. This improvement is characterized in that an upper crankpin die is mounted on a piston movable in relation to an upper cross member which is actuated by the ram of a forging press, said piston being responsive to a hydraulic ram having its cylinder carried by said cross member. The pressure developed in said ram is adjustable by means of a discharge valve set according to the dimensions of the workpiece to be forged, said valve permitting of performing the forging operation in two steps, i.e., firstly upsetting the metal while offsetting the crankpin, then forging the crankshaft webs at the end of the upsetting step.

Description

United States Patent Ruget [451 Mar. 21, 1972 541 APPARATUS FOR FORGlNG 2,534,613 12/1950 Meley ..29/6 CRANKSHAFTS AND H LIKE 2,747,253 5/1956 Conchon ..29/6

[72] inventor: Gabriel Ruget, St. Etienne (Loire), France v FOREIGN EN 0R APPLICATI NS [73] Assignee: Compagnie Des Ateliers et Forges de La 757,526 9/l956 Great Britain ..29/6

Loire (St. Chamond-Firmidy-St. Etienne- J co -ll z Rochefoucauld ri Primary Examiner-Charles w. Lanham France Assistant Examiner-Michael J. Keenan 22 Filed; July 14 19 9 Attorney-Wenderoth, Lind & Ponack [21] App], No.: 84l,272 Q [30! Foreign Application Priority Data improvement in apparatus for forging crankshafts and like July I). I968 France ..l5 9, 915 I workpieces 'Fnpmvemem ls cpamctemed Feb. 24. I969 France ..6 904 677 upper crankpm die mounted on a piston movable m relation -10 an upper cross member which is actuated by the ram of a 52 us. Cl ..72/412, 72/472, 29/6 forging press, said Piswh being responsive to a hydraulic ram [51 1 Int. Cl.'.., B21d 37/00 having its cylinder carried by said cross member. The pressure [58] Field of Search ..29/6; 72/412, 471, 472 developed in said ram is adjustable by means of a discharge valve set according to the dimensions of the workpiece to be [5 1 Rflefences Cited forged, said valve permitting of performing the forging operation in two, steps, i.e., firstly upsetting the metal while off- UNITED STATES PATENTS setting the crankpin, then forging the crankshaft webs at the 2,827,685 3/1958 Cleghorn ..29/6 end of the upsetting step. 2,790,227 4/1957 Fine "29/6 3 Claims, 13 Drawing Figures mammal 1972 3,650,143

' sum 1 0F 9 GABRIEL RUGET, Inventor Attorneys PATENTEUMARZ] m2 SHEET 3 BF '9 1 man L I PAIENTEUMAHm 1972 SHEET 4- UF 9 Had GABRIEL RUGET, Invantor PAIENIEnmm 1972 3,650,143

sum 5 OF 9 GABRIEL RUGET, Inventor ald/14M Attorneys PATENTEDMARZ] I972 3,55 4

SHEET7UF9 GABRIEL RUGIJT, Inventor AtEarnc-ys PATENTEUMARZI m2 SHEET 8 [1F 9 W\ M Q Q GABRIEL RUGET Inventor [1M4 KMM Attorneys PATENTEDMAR21 1972 SHEET. 9 or 9 Calibrated disc/var a valve /7; E

P/rcssure f/uiaL Disfribu! or H" 1,. caliEr-a ad discharge valve flistribu [0r Low-pressure calibrated discharge valve Return Pressure fluid GABRIEL Rum-y Inventor Attorneys APPARATUS FOR FORGING CRANKSHAFTS AND THE LIKE The present invention relates to apparatus for forging parts characterized by considerable variations in their cross-sectional dimensions, as described in the British Pat. Nos. 622,938, 628,519 and 696,618.

These apparatuses are adapted to be used in conventional forging presses and their chief purpose is the direct forging of crankshafts without twisting of the material. The blanks thus forged are provided with a continuous grain flow, for the necking operation, which is necessary in the usual method of slab forging, is eliminated and the metal fibers are directed parallel to the outer surface of the workpiece. The peripheral zone where the metal displays better properties remains in the vicinity of the surface, thus reducing appreciably surface defects, and the axial zone of the initial blank remains in the vicinity of the neutral axis of the finished throw and does not come to the surface at the junction between the crankpins (or journals) and the webs or cheeks, i.e., where the throw is weakest and highly stressed. With this specific texture, stresses are always directed longitudinally of the metal grain flow and the fatigue strength of the workpieces thus obtained is increased considerably.

This result is obtained by using an apparatus of the type shown diagrammatically in FIG. I of the attached drawing, this apparatus comprising essentially a lower bed plate 1 supported by the fixed cross member 2 of a conventional forging press;

a pair of sliding

cradles

3 and 3 supported by slideways 4 and 4 carried in turn by said support 1, and

an upper cross member 5 rigid with the upper crosshead 6 of the press.

In crankshaft forging, the initial blank comprises as a rule enlargements or swellings separated by constrictions. The enlargements generally are to constitute the webs or flanges of the forged crankshaft, i.e., the portions of which the shape is altered, and the constrictions are to constitute the necks of the forging, whether eccentric or not.

When following the press action the upper cross member 5 is lowered it causes via the inclined slideways 7, 7' the cradles 3 and 3' to move towards each other. This movement induces the upsetting of the metal on each side of the intermediate portion between the two end dies closed by the pressure of

rams

9 and 9 enclosed in the upper cross member 5.

As the

cradles

3 and 3" are moved towards each other the upper cross member 5 pushes vertically downward the upper crankpin die '10 against the lower crankpin die 11 which is supported by another ram l2, so as to set off transversely and downwards the upset metal.

These forging apparatuses transform the vertical movement of translation of the upper cross member 5 of the press into two perpendicular movements combined together in order to forge a throw on the blank. In FIG. 1 there is shown in dash and dot lines, between the two cradles 3 and 3', the lower crankpin die 11 and the upper crankpin die 10, a throw formed at the end of the forging operation.

It is also possible to forge crankshafts from plain bars, i.e., without alternate swellings and constrictions, by using the arrangement described and illustrated in the British Pat. No. 628,519. In this case, the cross member 5 engages firstly the

cradles

3 and 3 via slideways 7 and 7, thus producing a first upsetting of the blank metal; then this cross member 5 moves downward the upper crankpin die and the actual forging operation as described hereinabove begins at that time. This preliminary upsetting permits, from an initial plain bar, of disposing of a quantity of metal sufficient for giving to each web the necessary volume and this arrangement is particularly advantageous in the forging of crankshafts having relatively large webs in proportion to the journal diameter.

The British Pat. No. 696,618 describes the use of auxiliary cylinder and piston units acting upon the cradles 3 and 3' for increasing the upsetting force available and this arrangement is extremely advantageous when it is contemplatedto use a press of relatively long useful stroke but limited tonnage.

LII

It may be emphasized that all these arrangements have two common features: in fact, on the one hand as the upper crankpin die 10 is rigid with the cross member 5 theupsetting and offsetting strokes terminate at the same time, so that it is not possible to stop one stroke before the other; on the other hand, the metal constituting the webs is shaped freely," i.e., without being enclosed in a die or like element during any phase of the forging operation.

The advantageous features characterizing these auxiliary forging apparatuses are obvious and the crankshafts forged therein are of higher quality since the metal grain flow is properly oriented and at a lower cost, since the metal loss and machining time are reduced. However, this forging process produces rough-forged webs having substantially the shape of a plate of which the section through a plane perpendicular to the initial axis of the blank bar is of oval configuration, substantially an ellipse of very reduced eccentricity. In this case the upsetting length and the diameter of the initial bar must be calculated with a view to permit the inscription of the web to be machined within this ellipsoid, so that irregular and frequently considerable extra metal thickness must be provided thus increasing the machining time accordingly.

To reduce the total cost of crankshafts while increasing the efficiency of these forming apparatus, reduced and regular machining allowances must be obtained in the resulting blank. Under these conditions, the metal flow must be reduced by causing upper and lower crankpin dies and cradles to form together, at the end of the forging stroke, a closed volume similar to a die which the metal is forced to fill up. This improvement makes known apparatuses capable of utilizing these dies by exploiting more completely the tonnage of the press. In fact, the chief difficulty lies in the fullest or better utilization of the press power output and experience teaches that the forces to be implemented for obtaining a satisfactory forging operation are extremely high and increase as the shape contemplated departs from the shape that would be obtained if the metal was allowed to expand or flow freely." This effect is evidenced by a comparison between FIGS. 2 and 3 of the drawing.

In the case illustrated in FIG. 2, the metal flows freely and the upsetting force is proportional to the surface area of the meridian plane of the web and also to the creep strength of the metal. This creep strength increases as the e/D ratio decreases. Therefore, two causes act simultaneously to increase the upsetting force at the end of the stroke.

In the other case (FIG. 3) the metal flow is limited by the configuration given to upper crankpin die 10 and lower crankpin die 11. Assuming that the dimension D is the same as in the case illustrated in FIG. 2. On the other hand, as the metal contacts partly the upper and lower crankpin dies, the'ratio e/D should no more be used for determining the flow limit, the latter being subordinate to the sum of both ratios e /D e /D, since the meta] shape is no more altered in the area already in contact with the sidewalls; thus, the flow limit is considerably higher and increases to very important proportions when :2 and 2 tends to approach zero.

The upsetting force to be used when forging metal is about six time that necessary when the metal is allowed to flow freely, and increases very considerably during the last portion of the stroke.

A similar line or argument may be followed for explaining the increment in the offsetting effort at the end of the stroke. In fact, the shear-stress creep strength is lower in the planes remote from the geometrical bases than in the vicinity thereof; as these bases are closer to each other the flow limit and therefore the offsetting effort increase.

But if the metal is forged, two factors add their effects: on the one hand the creep strength is increased for the process takes place as ifthe bases were spaced by a distance e e in Finally, a third cause is effective in a forging operation; when the metal is forged in a die, some kind of escape or burr must be provided for the forged 'material, to permit the regularization of the shapes and stresses implemented. The metal burr thus formed has a considerable surface in proportion to its volume; besides, it cools very rapidly and its malleability is considerably lower. To shear this burr, very important forces must be developed at the end of the forging stroke.

All these reasons account for the fact that hitherto known forging apparatuses are ill-suited for properly forging the metal; as the upsetting and offsetting operations are performed simultaneously, the maximum forces are added. At the beginning of the stroke, the force available is considerably in excess of the reaction force, and-at the end of the forging operation the antagonistic efforts become abnormally high and cannot be overcome. I

It is a first object of this invention to make the best possible use of the power available in the forging press by modifying the upper crankpin die control system.

This first object is obtained by eliminating the hitherto customary rigid coupling between the movable cross member and the upper crankpin die so that the synchronization between the offsetting and upsetting movements ceases when the offsetting movement is ended but a short upsetting stroke is still available. 1

This invention is characterized in that the upper crankpin die is rendered independent of the upper cross member by mounting said upper crankpin die on a piston movable in relation to said cross member, said piston being controlled by a hydraulic ram having the pressure in its cylinder regulated by a discharge valve preset as a function ofthe dimensions of the piece to be forged, said valve permitting of performing the forging operation in two phases: firstly, upsetting the metal while offsetting the crankpin, then forging the webs during a last upsetting phase.

According to a modified form of embodiment, the pressure in said hydraulic cylinder is adjustable by means of a pair of discharge valves to permit in succession a preliminary upsetting, continuing this upsetting in conjunction with the crankpin offsetting,,and finally forging the web during a last upsetting phase.

According to another feature characterizing this invention, the action exerted by the rams clamping the lateral holding blocks or die holders of prior machines of this character is replaced by the vertical component of the force transmitted FIG. 4 illustrates the forging apparatus in longitudinal vertiby inclined slideways formed on the upper cross member of.

the apparatus to other slideways rigid with upper holding blocks.

It is a complementary object of this invention to combine the forging operation imparting'an elliptic configuration to the crankshaft webs with a final forging operation aiming at giving a well-defined shape to these webs. This double operation will be referred to as closed-die-forging" in the following disclosure.

These objects are carried out by providing dies disposed: either on the lower and upper lateral holding blocks or die holders; either on the upper and lower crankpin dies;

either on the upper crankpin die and on the lower lateral holding blocks or die holders;

or on the lower crankpin die and on the upper lateral holding blocks or die holders.

Other features and advantages of this inventionwill appear as the following description proceeds with reference to the accompanying drawing illustrating diagrammatically by way of example typical forms of embodiment of the invention. In the drawings:

FIG. 1 is a schematic view illustrating a forging apparatus as used in the prior art.

F IG. 2 is a schematic view illustrating a metal blank where the metal flows freely."

FIG. 3 is a similar view showing how the metal flow is limited by the configuration given to the upper crankpin die and the lower crankpin die.

cal section through the plane of symmetry containing the axis of the blank to be forged, this apparatus being similar to the one disclosed and illustrated in the British Pat. Nos. 622,938 and 696,618 but incorporating in addition the following two features characterizing this invention: firstly, the upper crankpin die carried by the upper cross member is rigid with a piston movable in relation to said cross member in the cylinder provided in said cross member, whereby the off setting movement is completed when a short final upsetting stroke is still available; secondly, impressions are formed in said upper crankpin die and on the lower crankpin die constituting, with the forging faces of the lateral holding blocks or die holders, the web dies. In these Figures, the same parts are designated by the same reference numerals as in FIG. 1;

FIG. 5 is a detail sectional view showing a die member arrangement;

. FIG. 6 is an elevational view showing a crankshaft obtainable by using the die members illustrated in FIG. 5;

FIGS. 7 and 8 are detail sectional views showing two other die member arrangements;

FIG. 9 is a diagram showing the action exerted by an inclined slideway of the upper cross member on an inclined slideway of the corresponding cradle;

FIGS. 10 and 11 are longitudinal sectional views showing the forging machine incorporating features already illustrated in FIG. 4 as well as other features to be described hereinafter.

FIG. 12 is a diagram illustrating the hydraulic circuit according to the feature of this invention whereby the pressure developing inthe upper crankpin die ram is adjusted by a calibrated discharge valve;

FIG. 13 is a hydraulic circuit diagram according to the modified form of embodiment whereby the pressure in the ram is adjusted by means of two differently calibrated valves.

As illustrated in FIG. 4, the

cradles

3 and 3 carry holding blocks 14 and l5, l6 and 17 adapted to hold the blank in position during the forging operation. The faces of these holding blocks which register with the forging zone are flat and the upper crankpin die 10 and the lower crankpin die 11 have formed therein the

impressions

20 and 22, 19 and 21. At the end of theshaping operation the holding blocks are stopped by against the fiat side faces of theupper and lower crankpin dies so that on either side of these two members a pair of closed dies are formed for shaping the blank metal to the desired configuration.

' According to the modified form of embodiment illustrated, in FIG. 5, the dies may be hollowed out of the lateral'holding blocks. Thus, as shown in this Figure, dies 31 and 33 are formed in the lateral blocks 15 and 17 for the pair of upper impressions, and other dies 30 and 32 are formed in the lateral blocks 14 and 16 for the pair of lower impressions.

This arrangement is advantageous in the very frequent cases of crankshafts 35 having webs 34 formed with a bevel 36 as illustrated in FIG. 6.

Other arrangements may be obtained by combining the two arrangements illustrated in FIGS. 4 and 5, thus:

FIG. 7 illustrates

impressions

20 and 22 formed in the upper crankpin die 10, and

other impressions

30 and 32 formed in the lower lateral blocks 14 and 16, respectively;

FIG. 8 shows impressions l9 and 21 formed in the lower crankpin die 11, and

other impressions

31 and 33 formed in the upper lateral holding blocks 15 and 17, respectively.

According to the geometrical arrangement of the crankshaft webs, and also the length and diameter of the crankpins and journals, one or the other of these solutions may be adopted.

Instead of being integral with the cross member 5 as in hitherto known constructions, the upper crankpin die 10 is carried by a piston 13a slidably mounted in the cylinder 13 of a hydraulic ram. The latter may be supplied with fluid under pressure when the cross member 5 is in its uppermost position, and when this member 5 moves downwards the cylinder may be connected to a fluid reservoir (not shown) via a valve adjusted to open under a predetermined pressure adjustable however as a function of the dimensions of the crankshaft to be forged.

The diagram of the hydraulic device connected to the ram 13 is illustrated in FIG. 12. This device comprises a calibrated discharge valve 70 connected to the ram 13, and a distributor 71 receiving the pressure fluid, the return taking place to the reservoir 72.

Similarly, the lower crankpin die 11 is carried by a piston 12a movable in a cylinder 12 of a hydraulic ram supplied with fluid under pressure when the movable cross member is in its uppermost position, just before the forging operation begins, said cylinder being connected to the reservoir via an adjustable valve when the cross member 5 is moving downwards.

The advantageous features characterizing this apparatus will appear more clearly as the description of its mode of operation proceeds.

The blank 8, of which the portion to be shaped into a throw has just been heated to the proper forging temperature, is laid with the proper orientation upon the holding blocks 14 and 16 integral with the

cradles

3 and 3 Preferably, the lower assembly of the apparatus should be shifted laterally so that it lies outside the press during the handling operation. This operation comprises two steps: firstly lowering the blank with a crane by a vertical movement of translation upon the holding blocks, then introducing this complete lower assembly into the press by a movement of translation parallel to the blank axis and under the control of the sliding table normally equipping the forging press.

When the press is actuated, the upper crosshead 6 is lowered as well as the upper cross member 5, whereby its inclined slideways 7 and 7' engage the registering slideways formed on the sliding cradles. At the same time the upper tool members engage the lower tool members, thus causing each one of the two blank portions clamped between the

blocks

14 and 15 or 16 and 17 to become integral with the sliding cradle 3 or 3' in which it lies. As the cross member 5 continues its downward stroke, the forging operation proper begins.

The inclined slideways and the auxiliary hydraulic actuators l8 and 18' move the sliding cradles towards the upper crankpin die 10, thus upsetting the blank metal. At the same time the offsetting of the blank portion constituting the crankpin of the throw being shaped begins. In fact, due to the operation of the discharge or exhaust valves of

rams

12 and 13, the lower crankpin die exerts an upward force F] and the upper crankpin die exerts a downward force F2. These valves are so adjusted that the force F| corresponds to the clamping force to be applied to the crankpin, and the force F2 is slightly superior to the sum of the force Fr, of the offsetting force and of the opening force of the central holding blocks which is caused by the pressure exerted by the metal against the lateral walls of

impressions

20 and 22.

Under these conditions, when the cross member 5 is lowered the piston 12a supporting the lower crankpin die 11 recedes in cylinder 12 and the piston 13a supporting the upper crankpin die 10 is stationary with respect to the upper cross member 5. Thus, the crankpin die is offset downwards. Then as the upsetting movement continues the lower crankpin die 11, after having been lowered through a distance corresponding to the radius or throw of the crank to be obtained, engages stop members (not shown), thus stopping the piston movement. The offsetting is then completed and about the three fourths of the upsetting or forging stroke are performed. The press has thus supplied the accrued efforts necessary for the beginning of the upsetting phase and the whole of the offsetting operation. As the latter takes place without enclosing the metal in the die members, the offsetting force increases with the stroke but remains relatively moderate.

From this moment, on the upper crankpin die 10 is in abutment and the pressure in the cylinder 13 controlling the upper crankpin 10 rises until the exhaust valve controls the discharge of the hydraulic fluid. During the remaining portion of the crosshead stroke the thrust supplied by the press is equal to its rated thrust minus the force F This is the thrust available, accrued by the force of rams 18 and 18' for completing the upsetting and forcing the metal into the shaping impressions of the die members. During this second phase the only movement taking place is the upsetting of the metal which is terminated when the holding blocks 14,15 and 16,17 stop against the upper crankpin die 10 and lower crankpin die 1 1. Then the crankthrow forging operation is completed. The press ram 6 is raised and carries along the cross member 5 and the upper tool members, and when these members have reached their uppermost level, the lower assembly of the forging apparatus can be removed from the working table or bed of the press. The blank is subsequently removed from the holding blocks, and the sliding cradles 3 and 3' are restored to their initial position; then the

rams

13 and 12 are supplied with pressure fluid to similarly restore the upper and lower crankpin dies to their initial positions, and a new cycle can be resumed by introducing a fresh blank with a vertical movement of translation. In certain cases this blank may be introduced into the apparatus without removing the lower portion of this apparatus from under the press crosshead; in this case a vertical movement of translation directed at right angles to the blank axis must be combined with a successive horizontal movement of translation parallel to this axis. Thus, time can be saved for forging throws at the ends of the bars.

From the above description and from the details of the operation of the apparatus according to this invention it will be seen that it is possible to forge crankshaft webs by making a better use of the thrust produced by a forging press.

A modified form of embodiment consists in communicating the cylinder 13 with the reservoir via two discharge valves.

The diagram of the hydraulic device according to this modified form of embodiment is illustrated in FIG. 13. It comprises a high-pressure calibrated discharge valve 73 and a lowpressure calibrated discharge valve 74, and a pair of

distributors

75, 76.

The first valve is directed to exert a vertical downward force upon the upper crankpin die 10, this force being veryslight ly inferior to Fr (the crankpin clamping force). This first valve is closed by the downward movement of the upper cross member and under these conditions the ram 13 can be discharged through the other valve setting a pressure value corresponding to the force F2. The crank forging process takes place in three successive steps. During the first step the upper crankpin die cannot overcome the lower crankpin die force and the metal is simply upset until the first discharge valve is closed; the second and third steps follow as described hereinabove. This sequence of operations: preliminary upsetting, forging, shaping, reduces the cost of crankshaft manufacture as the crankshafts can be obtained from plain blanks or bars without resorting to the hitherto customary forging or machining of spaced enlarged portions.

Another arrangement according to this invention affording a better utilization of the press tonnage, whether this arrangement is used separately or in combination with the preceding one, consists in eliminating the hydraulic ram 9 provided for clamping the lateral holding blocks 14 and 15, and also the hydraulic ram 9' for clamping the lateral holding blocks 16 and 17 illustrated in FIG. 4. According to the arrangement known through the British Pat. No. 622,938, the inclined slideways 7 and 7' engage, during their downward movement, the registering inclined slideways of the sliding cradles 3 and 3', thus producing a horizontal translation of these cradles towards each other and therefore the upsetting of the crankshaft webs.

As illustrated in FIG. 9, the action exerted by a slideway 7 carried by the upper cross member upon the registering inclined slideway of the sliding cradle producgs an inclined resultant F of which the horizontal component H provides the horizontal movement of said cradle. On the other hand, its vertical component V is transmitted (see FIG. 4) to the lower bed or worktable 2 of the press, via the sliding cradle 3 and lower frame structure 1 of the forging apparatus. This vertical component having a value of the same order of magnitude as that of the horizontal component is obviously without any useful function. In the cradle 3 the lower and upper lateral holding blocks 14 and 15 respectively are locked in position by means of the ram 9. This ram reacts against the lower face of the upper cross member 5 of the apparatus, which transmits the reaction of the operating thrust directly to the upper crosshead 6 of the press, thus tending to counteract its downward stroke. The same applies to the other sliding cradle 3' and ram 9', ofcourse.

If the reactions of rams 9 and 9' are not preponderant in the case of the free" forging process described in the British Patent No. 622,938, they become very important in the forging process with fiber orientation according to this invention, their sum attaining the order of magnitude of the maximum thrust required for the metal upsetting.

According to this invention, the rams for clamping the lateral holding blocks are dispensed with and their action is replaced by the vertical component of the force transmitted via the inclined slideways of the upper cross member to slideways registering therewith, these registering slideways being however integral with upper holding blocks in lieu of the sliding cradles.

This device is illustrated in FIG. 10 showing the forging apparatus in its open position (prior to the forging operation) and also in FIG. 11 showing the same apparatus in its closed position (end of forging operation). This apparatus comprises a lower frame structure 41 supported by the bed or worktable 42 of a conventional forging press; a pair of sliding

cradles

43 and 43 carried by slideways 44 and 44' provided on said blocks, thus causing the symmetric movement of these holding blocks towards each other and therefore the upsetting or shaping of the web metal. Adjustable limit stops (not shown) are provided for limiting the relation to the upper cross member the lowermost position of each upper lateral die-holding block and consequently their initial relative distance. The rarns 64 and 64' are provided for pressing these upper lateral die-holding blocks against said stop at the beginning of the forging operation.

The cradles 43 and 43' are also moved apart from their closed position by the same distances as the upper lateral dieholding blocks and are urged against limit stops (not shown) carried by the lower frame structure 41.

During the closing operation the blank 48 being supported by the lower die members the press crosshead 46 is lowered,

, thus carrying along the upper portion A of the apparatus, until frame structure 41; an upper cross member 45 integral with the movable crosshead 46 of said press (not shown); a pair of upper die holding blocks 63 and 63' suspended from the cross member 45 by means of a pair of hydraulic rams 64 and of another pair of rams 64', and adapted to move in relation to said cross member 45 in directions parallel to inclined slideways 47 and 47 due to theprovision of a pair of slideways 65 and of another pair of slideways 65. This suspension arrangement is given by "way of illustration, not in a limiting sense,-for it will readily occur to those conversant with the art that various modifications may be brought thereto while obtaining the same results.

In the following description the various component elements and functions of the apparatus will be designated as explained hereinafter:

a. Upper portion of the apparatus refers to the assembly A including all the component elements secured to or associated with the upper crossmember 45;

b. Lower portion of the apparatus refers to the assembly B including all the component elements secured to or associated with the lower frame structure 41,

c. Closed position" of the apparatus means the position assumed not only by the apparatus but by all or any of its component elements at the end of the forging operation;

d. Open position" of the apparatus means the position assumed not only by the apparatus but by all or any of its com- "ponent elements before the forging operation, with the press crosshead 46 in its uppermost position.

The Open" and Closed" positions of the apparatus are illustrated in FIGS. 10 and 11 respectively.

Before beginning the forging operation, of course, the apparatus is in its open position. The upper lateral die-holding blocks 63 and 63' are each moved away from their closed position by a distance equal to the web upsetting stroke.

As these holding blocks are caused to move parallel to the inclined slideways 47 and 47' in relation to the upper cross member 45, this symmetric diverging movement implies, for both die-holding blocks, a downward movement in relation to the cross member 45. It is this relative downward movement of the upper lateral die-holding blocks (which takes place under these conditions) that permits during the forging operation proper the relative downward movement ofthe upper cross member in relation to the upper lateral die-holding the upper die members 55 and 57 thereof engage the

lower die members

54 and 56, thus clamping the blank 48 therebetween. The upper lateral die-holding blocks 63 and 63 engage at the same time the sliding cradles 43 and 43', the upper crankpin die 50 engaging on the other hand the lower crankpin die 51. Key means (not shown) prevent any relative horizontal movement between the cradles 43 and 43', on the one hand, and the die-holding blocks 63 and 63', respectively. In this position corresponding to the beginning of the forging operation proper, the thrust exerted by the hydraulic rams 64 and 64' against the die-holding blocks 63 and 63 is amply sufficient to prevent the upperv die members 55 and 57 from being lifted in relation to the lower lateral die

members

54 and 56 respectively. As the movable crosshead of the press continues its downward stroke when the metal upsetting process is initiated the action of

rams

64 and 64 is suppressed and only the vertical thrust of the press, which is exerted on the inclined slideways, provides the contact between the upper lateral holding blocks and the lower lateral holding blocks with a pressure sufficient to counteract at any time the opening force developed by the thrust from the upset metal. The key means provided between the upper lateral die-holding blocks 63 and 63' on the one hand and the

cradles

43 and 43 on the other hand will cause these cradles to be driven during the upsetting movement. The other movements, namely the offsetting of the throw and the end of the forging process, take place in the manner described hereinabove, or as in known apparatus according to the British Pat. Nos. 622,938, 628,519 and 696,618. Upon completion of the forging operation the apparatus is closed so that the upper lateral die members 55 and 57 engage upper crankpin die 50 and the lower lateral die

members

54 and 56 engage the lower crankpin die 51. Then the hydraulic rams 64 and 64' are operated in the pull" direction so thatthey withdraw upwards the upper lateral dieholding blocks 63 and 63 As a consequence, these blocks are locked in the abutment position against the uppercrankpin die. The movable crosshead 46 of the press is raised and thus caused to carry along during its upwards stroke the upper portion of the apparatus; the upper die-holding blocks 63 and 63' are thus disengaged from the cradles 43'and 43 and the lower die members 55 and 57 as well as theupper crankpin die 50 are disengaged from the blank 48. Then, it is only necessary to remove the blank 48 from the apparatuswhich, after the movement of the die members away from each other, is ready to initiate another forging cycle.

The lifting height necessary for extracting the lower portion B of the apparatus from the press table by means of the pull means usually associatedtherewith is definitely inferior to that required for performing the same operation in the case of known apparatus such as described in the British Pat. No. 622,938. This feature permits of constructing for a same press an apparatus capable of forging webs of greater dimensions than those permitted by the use of a conventional forging apparatus.

A The forging with fiber orientation requires upsetting forces considerably greater than those required for the so-called free" forging process; therefore, relatively powerful'and consequently larger auxiliary hydraulic rams 58 must be used in this case. An arrangement characterized by a greater compactness than that of the arrangement shown in FIG. 4 consists, as illustrated in FIGS. 10 and 11, in incorporating the hydraulic rams 58 in the sliding cradles 43 (or 43').

With this invention, by using as a power source forging presses of known design and types, the above-described advantageous features can be obtained with crankshaft blanks and similar workpieces having considerably reduced machining allowances and also a continuous grain flow structure which improves very considerably the fatigue strength, or wear and tear resistance, of the parts thus forged.

I claim:

I. An apparatus for forging crankshafts and like workpieces to be fitted to a forging press having a movable crosshead comprising a pair of cradles mounted to slide horizontally in relation to said press in opposite directions, a cam face on each cradle, a slideway for each cradle, an -upper cross member having a slideway registering with said cradle cam face mounted for engagement by said movable crosshead, each cradle comprising a lateral die member to hold the blank to be forged during the forging operation proper and to upset the blank metal as a consequence of the movement of said cradles towards each other, a lower crankpin die, an upper crankpin die coacting with said lower crankpin die, said dies during the forging operation clamping the blank and offsetting the upset metal both transversely and downwardly, a piston movable in relation to said upper cross member on which said upper crankpin die is mounted, a hydraulic ram having its cylinder body carried by said cross member controlling said piston, a calibrated discharge valve set as a function of the dimensions of the workpiece to be forged for adjusting the pressure developed in said ram for forging in two stages, namely a first stage comprising upsetting the metal while offsetting the crankpin and a second stage comprising forging the crankshaft webs at the end of said upsetting stage.

2. An apparatus as set forth in claim 1 wherein a pair of discharge valves are provided to adjust the pressure developed in said cylinder to permit in succession first an upsetting of said blank metal, then a further upsetting of said blank metal while simultaneously offsetting the crankpin portion of said blank metal, and then finally upsetting and shaping the webs during the last fraction of the upsetting stage 3. Apparatus as set forth in claim 1 comprising lateral upper dies, upper blocks integral with said lateral upper dies and lower lateral dies located in said sliding cradles, the locking of said upper dies upon said corresponding lower dies being obtained by means of the vertical component of the force exercised by said upper cross member upon the corresponding upper block through the intermediary of two inclined guideways assuring the support of said upper cross member upon said die holding block, said locking maintaining the blank metal to be forged upon its pouring between said dies and preventing narrow openings of the latter during said operation, said upper die holding blocks resting upon said sliding cradles and urging them symmetrically towards one another in order to produce said pressing back of the blank metal to be forged, additional hydraulic rams for holding said upper die holding blocks against abutments at the beginning of the forging operation, means for rendering said rams inoperative when the forging operation begins and drawing then against said upper die and blockingit there to the end of the forging in order'to permit the opening of the apparatus and removal of the forged piece.

Claims

1. An apparatus for forging crankshafts and like workpieces to be fitted to a forging press having a movable crosshead comprising a pair of cradles mounted to slide horizontally in relation to said press in opposite directions, a cam face on each cradle, a slideway for each cradle, an upper cross member having a slideway registering with said cradle cam face mounted for engagement by said movable crosshead, each cradle comprising a lateral die member to hold the blank to be forged during the forging operation proper and to upset the blank metal as a consequence of the movement of said cradles towards each other, a lower crankpin die, an upper crankpin die coacting with said lower crankpin die, said dies during the forging operation clamping the blank and offsetting the upset metal both transversely and downwardly, a piston movable in relation to said upper cross member on which said upper crankpin die is mounted, a hydraulic ram having its cylinder body carried by said cross member controlling said piston, a calibrated discharge valve set as a function of the dimensions of the workpiece to be forged for adjusting the pressure developed in said ram for forging in two stages, namely a first stage comprising upsetting the metal while offsetting the crankpin and a second stage comprising forging the crankshaft webs at the end of said upsetting stage.

2. An apparatus as set forth in claim 1 wherein a pair of discharge valves are provided to adjust the pressure developed in said cylinder to permit in succession first an upsetting of said blank metal, then a further upsetting of said blank metal while simultaneously offsetting the crankpin portion of said blank metal, and then finally upsetting and shaping the webs during the last fraction of the upsetting stage.

3. Apparatus as set forth in claim 1 comprising lateral upper dies, upper blocks integral with said lateral upper dies and lower lateral dies located in said sliding cradles, the locking of said upper dies upon said corresponding lower dies being obtained by means of the vertical component of the force exercised by said upper cross member upon the corresponding upper block through the intermediary of two inclined guideways assuring the support of said upper cross member upon said die holding block, said locking maintaining the blank metal to be forged upon its pouring between said dies and preventing narrow openings of the latter during said operation, said upper die holding blocks resting upon said sliding cradles and urging them symmetrically towards one another in order to produce said pressing back of the blank metal to be forged, additional hydraulic rams for holding said upper die holding blocks against abutments at the beginning of the forging operation, means for rendering said rams inoperative when the forging operation begins and drawing then against said upper die and blocking it there to the end of the forging in order to permit the opening of the apparatus and removal of the forged piece.