US3570298A

US3570298A - Forging

Info

Publication number: US3570298A
Application number: US762042A
Authority: US
Inventors: Hermann Detzel; Alfred Maier
Original assignee: Individual
Current assignee: Maschinenfabrik Alfing Kessler GmbH
Priority date: 1968-09-24
Filing date: 1968-09-24
Publication date: 1971-03-16
Anticipated expiration: 1988-03-16

Abstract

THE SPECIFICATION DESCRIBES A FORGING METHOD USING TWO DIE SETS WHICH ONLY HAVE THE FINISHED DIMENSIONS OF THE FORGING ALONG PLANES WHICH INTERSECT 90* IN THE FORGING. ALONG OTHER PLANES THE DIES HAVE GREATER DIMENSIONS.

Description

March 16, 1971 H DETZEL ETAL I 3,570,298

FORGING Filed Sent 24, 1968 6 Sheets-Sheet 1 INVENTOR;

March 16, 1971 DETZEL ETAL FORGING 6 Sheets-Sheet 2 Filed Sept. 24, 1968 FIGS -FIG.8

INVf NIOR Hermunn Dwtml Alfred Mme! FORGING 6 Sheets-Sheet 5 Filed Sept. 24, 1968 FIGS INVENTOR; Hermann Detzel Alfred Maier March 16, 1971 v DETZEL ETAL 3,570,298

rename Filed sent. 24, 1968 s Sheets-Sheet 4 INVENTOR: Hermunn [)etzel Alfred Mule! March 16, 1971 DETZEL ETAL 3,570,298

FORGING Filed Sent. 24, 1968 v 6 Sheets-Sheet 5 INVENTOR; Hermann Detzel Alfred Meier March 16,1971 HDETZEL ETAL 3,570,298

FORG ING Filed Sept. '24, 1968 s Sheets-Sheet e INVI-TNTQR; Hermann Detzel Alfred Meier United States Patent Ofice 3,570,298 Patented Mar. 16, 1971 3,570,298 FURGING Hermann Detzel, 110 Wilhelmstrasse, 7083 Wasseral- ABSTRACT OF THE DISCLOSURE The specification describes a forging method using two die sets which only have the finished dimensions of the forging along planes which intersect 90 in the forging. Along other planes the dies have greater dimensions.

The present invention relates to forging and more particularly though not exclusively to the forging of crankshafts.

Crankshafts are generally drop-forged, that is to say forged in dies, since they are engine components subjected to high stresses in which the grain should, as far as possible, follow the main journals, webs and big-ends of the crankshaft and should be cut as little as possible in subsequent machining, that is to say the grain should be aligned with the surfaces after machining.

However, above a certain size it is difficult to drop-forge crankshafts since the drop-forge hammer and dies used for the purpose are expensive and the number of shafts in a run produced is small. As a result large crankshafts are hammer forged without dies but this leads to poor grain characteristics. For such hammer forging work, the stock is given a cranked shape by means of the press so as to give it a suitable external shape with suflicient excess material to allow for machining. The metal between the webs is not removed, so that the big-ends must be milled out to size or the material around them cut away by fiamecutting. However, this cuts the grain of the stock between the webs.

In order to improve the grain configuration, methods have been developed in which a piece of stock is prerolled at particular intervals to the journal diameter of the crankshaft. At these positions the blank so produced is held and a press is used to make the intermediate, thicker part to form a throw. Besides the press, it is usually also necessary to use holding rams which prevent lateral deformation of the material. Although in this manner it is possible to achieve a satisfactory grain configuration, keeping to the longitudinal tolerances for the crankshaft usually gives rise to great difiiculties. Moreover, the degree of forging of the material in the webs connecting the big-ends with the journals is usually poor.

One object of the present invention is to provide an improved method of drop-forging.

A further object of the invention is to provide a method of hot drop-forging crankshafts which is capable of producing crankshafts with a better grain configuration and with an improved accuracy as regards longitudinal dimensions.

A further object of the invention is to provide a method of drop-forging crankshafts which does not require use of external holding rams.

A more specific object of the invention is to provide a method of forging crankshafts or the like in which the workpieces are repeatedly forged between two different die sets having different cavities, the workpiece being turned through 90 about its axis between forging operations in the two die sets.

A further objectof the invention is to provide a method of drop-forging in which the workpiece is successively acted upon by two different die sets which cause movement of the metal in a direction perpendicular to the line of relative movement of the dies in the sets.

A still further object of the invention is to provide means for drop-forging crankshafts or the like which makes possible successive forging in two different die sets, the die sets being mounted for sliding movement on a forging press so that they can be alternately brought into a given operative position between forging strokes, the workpiece being carried in a manipulator which turns the workpiece through about its axis during horizontal displacement of the die sets.

Still a further object of the invention is to provide a forging apparatus including a forging press with a forging table and a die set which is capable of sliding in relation to the table.

More specifically the invention is intended to provide hydraulic means for displacing the die set between individual forging or pressing strokes.

Yet a further object of the invention is the provision of a drop-forging method which does not produce flash on the workpiece.

In accordance with one aspect the present invention consists in a method of forging a hot metal workpiece comprising subjecting the workpiece repeatedly to the following forging cycle:

Squeezing the workpiece between a first pair of forging dies whose relative movement is along a first line parallel to a line radial to an imaginary axis of the workpiece, followed by squeezing the workpiece between a second pair of forging dies whose relative movement is along a second line parallel to a line radial to the axis of the workpiece, the first and second lines being angularly offset, the first pair of dies being moved closer together during each succeeding cycle, and the second pair of dies being moved closer together during each succeeding cycle.

In a preferred embodiment of the invention the work piece is turned through 90 between forging in the first and second die sets and the dies move vertically.

The deformation of the workpiece in the first forging step between the first pair of dies can amount to 10% of the total deformation required, and forging can be carried out until both the dies of the first pair come into contact and the dies of the second pair come into contact.

Preferably the workpiece during squeezing between dies is caused to move in a direction perpendicular to the axis and to the direction of relative movement of the dies so as to take on over-size dimensions in the direction perpendicular to the axis and to the direction of relative die movement. Although the invention is more specifically concerned with the production of crankshafts, it is clear that it can be used for the drop-forging of other articles.

In accordance with a further aspect the invention consists in a forging apparatus comprising a forging press characterised in that the apparatus comprises first and second die sets each having an upper and a lower die, the cavities of the two die sets representing finished profiles of a workpiece to be forged which are offset by 90 about an axis of the workpiece, and being over-size in the horizontal direction to allow the workpiece to take on over-size dimensions laterally.

The apparatus can comprise hydraulic means for reciprocating the die sets linearly so as to bring them alternately into a given operational position. In order to limit movement of the die sets, abutments can be provided and the hydraulic means can take the form of two hydraulic cylinders for moving the two die sets respectively in a horizontal direction.

Alternatively the forging press can comprise table means, carrying the die sets, and means for turning or oscillating the table means about its vertical axis so that the 3 die sets are alternately moved into an operational position, for instance through 90 or through 180 about the vertical axis.

The apparatus can further comprise a manipulator for moving the workpiece horizontally between the die sets. The manipulator can comprise a horizontal slide for guiding movement of the workpiece.

Alternatively the workpiece can be carried in a pair of tongs.

In order to render the invention more readily understood, some embodiments of it are now described with reference to the accompanying diagrammatic drawings.

FIG. 1 is a diagrammatic longitudinal section through a first die set.

FIG. 2 is a diagrammatic side view of the die set in accordance with FIG. 1.

FIG. 3 shows the upper part of the first die set from below.

FIG. 4 is a plan view of the lower die of the set as shown in FIG. 1.

FIG. 5 is a longitudinal section through the second die set.

FIG. 6 is a side view of the second die set as shown in FIG. 5.

FIG. 7 is a view of the second die set from below.

FIG. 8 shows the lower part of the second die set in plan view.

FIG. 9 is a perspective view of a workpiece.

FIG. 10 is a diagrammatic side view of a forging press with the die sets, the manipulator and the workpiece.

FIG. 11 is a diagrammatic front view of the forging press with the die sets and hydraulic shifting means.

FIG. 12 shows the manipulator with an additional transverse sliding arrangement of the jaws of the manipulator, the jaws being provided with rotating means.

FIG. 13 shows a rotary circular table carrying dies, in plan view.

FIG. 14 shows a further embodiment of a rotary circular table in plan view.

Referring now generally to the drawings and more speicfically to FIG. 9, it should be noted that in the method in accordance with the invention two different die sets are used by which a workpiece 6 is forged in two

planes

14 and 15 which are offset by 90 about the axis of the workpiece.

For this purpose the workpiece 6 after being forged in the first die set is turned through 90 about its axis and placed in the second die set whose cavity is correspond ingly rectangularly offset from that of the first die set.

The first die set consists of a lower half or die *1 and an upper die '2, see more specifically FIGS. 1, 2, 3, 4, and 11. The second die set consists of the lower die 3 and the upper die 4, see more specifically FIGS. 5, 6, 7, 8, and 11. Each of the

die cavities

8 and 12 has the final dimensions of the workpiece in a vertical plane while in the horizontal or transverse direction it is over-size so that a free space 9, 9' is present for the escape or displacement of the workpiece material during the course of forging, as will be explained specifically below. In FIGS. 1 to 8 the final dimensions of the workpiece 6 as shown in broken lines and the

free spaces

9, 9 extending laterally from the direction 13 of pressing can be seen in both die sets.

Before forging using the two die sets as shown in FIGS. 1 to 8 is carried out a bar or blank is pre-forged to suitable starting dimensions, this not being shown in the drawings or described because pre-forging of such a blank can be carried out using procedures well-known to those in the art.

For forging in accordance with the invention a manipulator 11, or in the case of small workpieces a pair of tongs, is used. For the purpose of grasping the workpiece by means of a manipulator, a spigot 7 is forged on the workpiece. During the course of drop-forging in the die set this spigot lies outside the die. The spigot can serve for sampling the metal of the workpiece for quality control.

During the first pressing or forging step in the abovementioned die set shown in FIGS. 1 to 4, the workpiece is pressed by the ridge 5 defining the cavity 8 of the lower die 1 so that material is pressed in a direction of the crank 10. This deformation, which could in convenventional methods be carried to completion by single or several forging strokes, is however not completed in the method in accordance with the invention in a single stroke, that is to say during a single stroke relative movement of the two dies is not sufficient to bring them together along the plane of junction 14 (see FIG. 2.). The two dies 1 and 2 are separated, the workpiece 6 is then removed from the cavity 8 of the lower die 1 by the manipulator 11 in an upward direction and the manipulator 11, which engages the spigot 7 of the workpiece 6, turns about the axis of the workpiece. Then either the second die set is moved into the position of the first die set, as will be described in more detail below in the case of the embodiment of the invention shown in FIG. 11, or the workpiece itself is moved horizontally into the space between the second die set 3, 4, the second die set being mounted in a separate die forging press mounted beside a first die forging press in which the first die set is arranged. The workpiece is then placed in the lower die 3 of the second die set by the manipulator 11, see FIGS. 5 to 8. In a similar manner the workpiece is now forged by one or more strokes of the upper die 4. Both in the first forging operation in the first die set and in the second forging operation in the second die set the degree of deformation can amount to about 10% of the total deformation of the workpiece required.

In order to convey the workpiece from the first die set to the second die set it is naturally possible in the case of small forgings to use a simple pair of tongs, and in this case may in some cases be possible to dispense with the spigot 7 forged on the workpiece, that is to say, if the tongs can be used for removing the workpiece from the cavity of the lower die in each set and turning the workpiece about its axis.

After the rotation of the workpiece through 90 about its axis drop-forging in the second die set as shown in FIGS. 5 to 8 is carried out in the same manner as before. This is followed by renewed forging in the first die set as shown in FIGS. 1 to 4 and then there is further pressing in the second die set 5 to S. This alternate forging in the two die sets is continued until the upper and lower dies 1 and 2 or 3 and 4 come to lie against one another along their

junction planes

14 and 15, as shown in FIGS. 2 and 6. This is generally achieved after 8 to 12 pressing operations, half of the pressing operations being carried out in one die set and the other half in the other die set.

The above-described method in its general form can be used for the forging of all sorts of crankshafts with any desired number of cranks, and also for the forging of other workpieces in which a good grain configuration is required. Besides the two above-mentioned die sets it is also possible to use further die sets with die cavities which differ from each other, so that a still closer approximation of forging to the finished dimension is achieved. In general, however, use of the two abovementioned die sets as described and illustrated is sufficient.

The disadvantages of using twice the number of die sets and the frequent turning of the crankshaft, and of shifting the die sets or shifting the workpiece horizontally, are more than outweighed by the advantages which are obtained with the method in accordance with the invention; there is no need to provide flash removing tools and pre-bending tools for bending the blank. The turning of the workpiece about 90 can readily be carried out with suitable manipulators in a precise manner. Moreover, it is also possible, if required, to manipulate the workpiece manually using tongs.

A further substantial advantage resides in the fact that points of weakness occurring along the flash lines in the case of conventional forgings are completely avoided and that crankshafts forged in accordance with the invention are of high quality as regards the cheek pieces or webs, that is to say the parts connecting the big-ends with the main crankshaft journals. High quality is also obtained as regards the transitional Zones between the big-ends and the Webs.

FIG. 11 shows the overall forging apparatus for carrying out the invention with means for shifting the die sets. Reference numeral 16 indicates the upper ram or top of a conventional forging press, which is moved in the direction of the arrow 13 towards the lower ram or support 17.

FIG. represents the forging press in accordance with FIG. 11 as seen from the direction of arrow C as shown in FIG. 11, a forging manipulator 11 also being shown which is in the form of a wheeled vehicle. The forging press is not shown in all its details but only diagrammatically because such forging presses are known and can be made in the most different forms of construction. The same applies for the forging manipulator 11. Thus it is not necessary to use a vehicle with wheels 40 as is illustrated, and other forms of the manipulator can be used. The feature which is to be provided for is that the workpiece 6 should be held by means of its spigot 7 by the manipulator jaws 37 of the manipulator head 38 so that the workpiece 6 can be moved in the direction of the arrow 35 by driving the manipulator 11, and in the reverse direction. Moreover, in order to carry out the method in accordance with the invention, it is necessary that the manipulator head 38 with the gripping jaws 37 should be capable of being turned in the direction of the arrow 41 between individual forging operations.

For this purpose it is convenient to move the manipulator slide 42 in the direction of the arrow 36 upwards or downwards. Furthermore an inclination of the manipulator head 38 can be conveniently provided in order to allow alteration in the angle to the horizontal, as indicated by arrow 39, this enabling the workpiece to be placed more precisely in its desired position.

It may be convenient, as a further feature, to support the workpiece 6 at the end, opposite to the manipulator 11, of the forging press shown in FIG. 10, during forging. This is not shown as it is a known practice in the case of heavy and/ or long workpieces.

The forging press shown in FIGS. 10 and 11 has four

columns

31, 32, 33, and 34, column 34 not being visible because it lies behind the column 32 in FIG. 10 and in FIG. 11 it lies behind the column 33. As will be explained below, the performance of the method in accordance with the invention can be carried out with smaller presses, for example with presses only having two columns.

On the upper ram 16 a table or base plate 18 is attached by means of bolt 43, or in another convenient manner.

A slide 19 is carried on the plate 18 by means of interconnected male and female parts 44 of dovetail shape, shown in broken lines in FIG. 11. The upper dies 2. and 4 of the two die sets are wedged in the slide 19 with a center distance of a, see also FIG. 11. For this use is made of a dovetail joint 45 which runs at 90 to the dovtail by which the slide 19 is carried so that shifting of the slide 19 does not tend to dislodge the dies. For shifting the slide 19' use is made of a hydraulic cylinder 20 which is attached by means of a bracket 21 on the plate 18. The piston 22 in the cylinder v20 shown in FIG. 11 operates by means of a piston rod 23 which is connected with the slide 19 so as to bring about a shifting in the direction of arrow 46 in FIG. 11 in both directions. For this purpose the cylinder 20 is made double acting. Preferably the stroke of the cylinder is arranged to perform half strokes equal to half the distance a so that the slide 19 is moved sufiiciently to bring one or other of the upper dies exactly to the middle of the press, that is to say half way between

columns

31 and 33 and the

columns

31, 32, 33, and 34 are evenly loaded in a symmetrical manner.

In a similar manner the lower arm 17, which is stationary, carries the base plate 24 on which the slide 25 is mounted in a similar manner to the upper slide 19. In this slide 25 the lower dies 1 and 3 of the two die sets are mounted with a center distance of a. In this case as well a hydraulic cylinder 26 is provided which is fixed by means of a bracket 27 on the base plate 24 and has a piston 28 which is connected with the slide by means of piston rod 29. The piston 28 is arranged to move the slide through a distance equal to half the center distance of the lower dies 1 and 3 in the direction of the arrow 47.

The movement of the

slides

19 and 25 in both directions is preferably limited by abutments, not shown, in order to ensure that the shifting brings the dies into the precise positions required. These abutments can be formed by means in which the

pistons

22 and 28 abut in their cylinders 20' and 26 respectively.

For operation the cylinders 20 and 26 are connected with suitable hydraulic liquid ducts which are connected with a suitable source of liquid under pressure via suitable valves and control means, these not being shown in the diagrammatic drawing as they can be of a type Wellknown to those in the art. In the present case, in which the upper ram 16 is arranged to move downwards onto the lower ram, it is generally necessary to provide flexible hydraulic liquid ducts for the upper cylinder 20, while this is not necessary in the case of the cylinder 26 on the lower ram 17. If both rams are arranged to move, it may be necessary to provide flexible ducts leading to both cylinders 20 and 26.

In what follows the operation of the apparatus in ac cordance with FIGS. 10 and 11 will now be described in more detail. Firstly the pre-shaped workpiece 6 is grasped by the head 38 with jaws 37 of the manipulator 11, as indicated in FIG. 10. Then the upper ram 16 is moved to a position somewhat higher than that shown in the drawing so that sufficient space is left in the pairs of dies 1 and 2 and 3 and 4. Furthermore both the upper slide 19 and the lower slide 25 are moved half the distance a from the symmetrical position shown in FIG. 11 to the right or the left in accordance with which pair of dies is to be used for the first forging operation. Then the manipulator 11 is driven up in the direction of arrow 35 so that the workpiece 6 is brought into its forging or pressing position between, for example, dies 1 and 2. The manipulator head 38 is now lowered in the direction of arrow 36 until the workpiece comes to lie on the lower die 1. Then at least one forging stroke is carried out by means of the upper ram 16 moving downwards in the direction of arrow 13 so that a deformation of the workpiece takes place which is equal to about 10% of the total deformation in the die junction plane 14, see FIG. 9. Next the upper ram 16 is moved upwards again and the workpiece 6 is raised by the manipulator 11 in the direction of the arrow 36. The manipulator head 38 is now turned to in one or other direction about the axis of the workpiece. During this rotating or turning the cylinders 20 and 26 are used to move the die sets in the above-described manner so that now the other pair of dies, in this case dies 3 and 4, come to be placed symmetrically in the press, that is to say so that their center is aligned with the center line 48 of the press. The workpiece 6 is lowered by means of the manipulator 11 onto the die 3 and the workpiece is subjected to one or more forging or pressing strokes, the upper ram moving in the direction of arrow 13 so that a deformation of the workpiece is produced which is again equal to about 10% of the total deformation necessary. Then the workpiece 6 is raised out of the lower die 3 by means of the manipulator 11 and turned back throuhg 90 so that the workpiece again assumes its original position. Following this there is a shifting in the opposite direction, as indicated by arrow 35, so that dies 1 and 2 come into the operation position. Forging or pressing is then carried out ing of the manipulator, for example on the wheels 40, is

avoided. 1

The procedure can also be carried out by means of automatic control means, for example'by meansof following control means which is adapted to sense when one operation is completed and then switch over to the next operation. For this purpose the manipulator 11 can be connected with the hydraulic circuit not shown, controlling the forging press, so that as soon as the workpiece 6 has been grasped correctly by the manipulator, forging is carried out automatically until the workpiece is fully forged. It is, however, also possible, for instance in the case of small workpieces for which a different type of the manipulator is used, for the necessary movements 'to be exclusively performed by the manipulator without. the dies being shifted horizontally. v v

In particular, in accordance with a further embodi ment of the invention, the manipulator 11 can be pro vided with an additional transverse slide 50 (see FIG. 12) on which the manipulator head 38 is carried so it slides in the direction of the arrow 36 it can also carry out limited movement in the direction of the arrow 51 in order to bring the workpiece 6 to one die set or the other. In this case there is no lateral shifting of the dies, though there is an eccentric loading of the press which is, however, not constant and occurs first on one side and then on the other.

The manipulator construction in FIG. 12 substantially corresponds to that of FIG. but has vertical guide 49 with slide 50 enabling the manipulator head to be moved horizontally by hydraulic drive through the distance a as indicated by arrow 51. The slide also carries the means 42 for rotating the manipulator head. This means is provided with an adjustable indexing ring on which 90 angles are marked. The cooperating means are provided to give the driver of the manipulator an optical signal when rotation through 90 has been completed. When the indexing ring has once been set, the manipulator driver only requires to move the shaft of the manipulator head in one direction of rotation and then the other.

This method of displacing the workpiece in the manipulator through the center distance a of the dies has the great advantage that the dies are mounted in a fixed manner on the upper and lower parts of the press and that the die shifting means shown in FIG. 11 is not required.

FIGS. 13 and 14 show a further form of apparatus in accordance with the invention including two round tables on which the dies are so mounted that their center of gravity is approximately in the middle of the press. In the arrangement of FIG. 13 the table comprises an upper rotary part 52 in the form of a 90 sector or segment while the lower part 53 of the table is a 180 sector, both parts being arranged in a two column press with

columns

54 and 55. These two columns are connected by the stationary connecting part 56.

The turning table part 52 is arranged to be oscillated through precisely 90 about the pin 57 by means of a suitable drive device so that firstly the die 1 is brought into the working position, as shown in FIG. 13 and then, following oscillation through 90, the other die 3 is brought precisely into the working position, that is to say in a central position between the two

columns

54 and 55 so that this arrangement in accordance with the invention assures a precisely symmetrical loading of the press throughout operation. The corresponding upper dies 2 and 4 are carried on a corresponding turning part attached to the upper ram. This is not shown as the con struction can be precisely similar to the construction shownin FIG. 13, theaxisof oscillation being the same, that is to say coinciding, with the axis ofp'in 57. This em bodiment of the invention has the advantage that presses

withonlytwo columns

54, and 55 can be used without any additional space requirement. Arrow 60 is used to indica'te the direction of oscillation of the table part 52 out of the position shown in FIG. 13. v

In the embodiment ofFIG. 14 a round table 58 is used which can be rotated or oscillated in the direction of the arrow 59. 'I'his'arrangement is more suitable for use with a large press having four columns, as is shown in FIG. 10. Withsthis arrangement as well the diesare close to the center of the press so that there is only a very slight tipping action on the press stand. The rotation or oscillation" of the table 58 or of the table part 52 in accordance with FIG. 13 can be ensuredmechanically by means of a gear wheel drive, by meansof a Geneva mechanism, by means of wire IOpes or chains, or by an electro-hydraulic system using pistons or piston rod, or by means of rotary pistons. These means'for causing rotation or oscillation can be of a type well-known of those in the art so they are not described. It should, however, bementioned that the most'variou's means can be used including those incorporating" an intermediate step-down drive powered by an electric motor.

, In the present case, that is to say in the case of the construction 'in' accordance with FIG. 14, the'table 58 is turned in the direction of the arrow 59' about 180 so that either the die 1 or the die .3 is moved intothe operational position in'the front part of the lower ram 17. It is,- however, possible also to provide for an eccentric arrangement of the rotary table 58 in relation to the four

columns

31, 32, 33, and 34, just as in the case of the construction in FIG. 13 in which the pivot pin 57 is offset in relation toa line connecting the columns..54 and 55. In accordance with FIG. 14- the pivot pin 61 is, however, arranged so as to.be precisely symmetrical in relation. to all four columns.

The .tableSS can eitherbe arranged to be rotated, that i s to sayalways move in steps in the same direction, or it can be arranged to be oscillated in which case it is moved in,steps in the opposite directions. If a rotary table is mounted on the upper ram of the press. and a further rotary table is mounted on the lower ram of the press and provision is made for the mounting of the dies so'asto be oifset'by 180 or about the axis of turn ing of the table, the following possibilities are'presented.

- Inthe-case-of 'the180" arrangement of 'the' dies, see FIG. 14, that is'c-to sayone behind the other,'the tables can be turned in steps always in the same direction; the tables do not have to be turned through in one direction and then turned through 180 back in the opposite direction, although this is advantageous if terminal abutments are used. The arrangement of dies with their axes aligned as shown in FIG. 14 has the further advantage that two shafts can be simultaneously forged, a manipulator being provided on each side of the press. This arrangement offers advantages in the case of small workpieces. In the case of larger workpieces it is convenient to arrange the dies so as to be oifset through 90 about the pin 57 of the table so that the operational position for the dies is symmetrical in relation to the press.

In this case there is a further advantage in the case of forging crankshafts by methods in which a die with only two throws is used while the finished crankshaft has a multiple of two throws. In this case when two throws have been completely forged the crankshaft is moved along its axis by means of the manipulator through a distance equal to the axial length of two throws and is then further forged by means of the dies which produce further throws.

This possibility can also be applied in the case of the transverse linear movement of the die or of the workpiece in the manipulator.

What we claim is:

1. A method of forging a hot metal workpiece, comprising:

(a) placing the workpiece between a first pair of forging dies whose relative movement is along a line parallel to a first line radial to the axis of the workpiece and whose cavities are over-size in the direction perpendicular to said relative movement,

(b) squeezing the workpiece between said first pair of dies to partially deform the workpiece in the direction of relative movement of the dies, while allowing the workpiece to move freely in the direction perpendicular to the direction of movement of the dies,

(c) removing the partially deformed workpiece from the first pair of dies,

(d) placing the workpiece between a second pair of forging dies whose relative movement is along a line parallel to a second line radial to the axis of the workpiece, and whose cavities are over-size in the direction perpendicular to said relative movement, the first and second radial lines being offset angularly relative to each other,

(e) squeezing the workpiece between said second pair of dies to partially deform the workpiece in the direction of relative movement of the dies while allowing the workpiece to move freely in the direc tion perpendicular to the direction of movement of the dies, and

(f) repeating the foregoing steps until the dies of each pair are brought into contact with each other.

2. The method of claim 1 wherein each partial deformation is about of the total deformation required.

3. The method of claim 1 wherein the first and second radial lines are offset 90.

4. The method of claim 3 wherein the relative movement of the die sets is vertical and the workpiece is rotated 90 between forging in the first and second die sets.

5. Apparatus for forging a hot metal workpiece, comprising (a) a forging press having upper and lower relatively movable die support members,

(b) first and second forging die sets each having an upper and lower die, the cavities of the two die sets representing finished profiles of the workpiece to be forged which are offset by 90 about an axis of a workpiece to be forged and being over-size in the horizontal direction to allow the workpiece to take on an over-size dimension laterally,

(0) means conecting the upper dies to the upper support member, and

(d) means connecting the lower dies to the lower support member.

6. The apparatus of claim 5 wherein the connecting means includes hydraulic means for reciprocating the die sets linearly so as to bring them alternately into a given operational position.

7. The apparatus of claim 5 wherein the connecting means includes table means carrying the die sets and being arranged for turning about its vertical axis for bringing the die sets alternately into an operational position.

8. The apparatus of claim 7 wherein the die sets are offset by an angle of about the vertical axis of the table means.

9. The apparatus of claim 7 wherein the die sets are offset by an angle of about the vertical axis of the table means.

10. The apparatus of cairn 5 including workpiece manipulating means supported adjacent the press and including workpiece gripping means, and means mounting the gripping means for movement of a workpiece vertically, horizontally and rotationally relative to the die sets.

11. The apparatus of claim 10 wherein the mounting means for the gripping means includes (a) a main support movable toward and away from the press,

(b) slide means mounted on the main support for vertical reciprocation,

(c) a head mounting the gripping means, and

(d) means mounting the head on the slide means for vertical movement with the latter and for axial rotation relative thereto.

12. The apparatus of claim 11 including means mounting the head for horizontal reciprocation relative to the main support.

References Cited UNITED STATES PATENTS 171,457 12/ 1875 Wilcox 72-472 173,854 2/1876 Garvin 72-472 2,653,373 9/1953 Brauchler 29-6 2,892,254 6/ 1959 Garvin 296 LOWELL A. LARSON, Primary Examiner U.S. Cl. X.R.