GB2048736A - Warm Forging of Connecting Rod Caps - Google Patents

Abstract

Connecting rod end caps 22 are formed by a method comprising using a closed die set, a billet of predetermined shape and volume, warm forging temperature i.e. 875 DEG -1093 DEG C, and an ejector 88, 90. The ejector pin 90 defines part of the mould cavity when retracted, ejects the finished parts when extended, and locates new billets when in an intermediate position. <IMAGE>

Description

SPECIFICATION Warm Forging of Connecting Rod Caps This invention pertains to a method and apparatus for warm forging workpieces. The workpiece may for example be connecting rod end caps for use in internal combustion engines.

A connecting rod end cap is the semicircular part in an engine which mates with the big end of the connecting rod to define the crankpinreceiving bore for the purpose of joining the connecting rod to the crankshaft of the engine.

The little end of the connecting rod is, of course, connected to a piston of the engine.

The cap, in addition to joining the connecting rod to the crankshaft, also provides a dynamic mass to counter balance the moving mass of the piston and the connecting rod. The ends of the cap, a generally crescent shaped part, also include bosses through which bolts are fitted to make the connection to a similar structure on the connecting rod. The inside surface and the bottom surfaces must be finished in order to mate properly with the other parts used with the connecting rod cap.

Heretofore, in the larger types of internal combustion engines (such as commercial vehicle engines or American automobile engines, the caps have been produced by a hot forging technique, using progressive dies, followed by conventional machining of virtually all the surfaces of the cap in order to produce an acceptable component. This technique has many disadvantages, namely, the high expense of progressive dies, the amount of waste material generated in hot forging using such dies, and the expense and opportunities for error in the extensive machining of the forging necessary to produce the finished component.

Furthermore, hot forgings always have scale (which must be removed by shot blasting); and they cannot be formed to the dimensional accuracy of parts made in accordance with the invention to be disclosed later herein.

Other prior art, more closely related to the invention, involves the manufacture of such caps for very much smaller engines, such as are used in cars exported for sale in the United States of America. Such caps do not have anywhere near the same complexity as those required for the larger United States manufactured engines, thus making them much simpler to manufacture in closed dies without flash. However, it is believed that even such simpler parts were made in successive stages, and this was done at temperatures much closer to hot forging temperatures than the temperatures used in the warm forging technique of the present invention.

In short, none of the prior art contemplates the use of warm forging and the other elements of the invention as set forth below, to produce a part of the complexity contemplated by the present invention.

With hot forging it is not possible to reproduce very fine definition of parts, the main reason being that the scale, which is always present at hot forging temperatures, has a tendency to "build up" in the dies, and thereby in turn to disrupt production.

There are three generic classes of metal forming equipment. These classes are defined by the operating restrictions or characteristics of the particular equipment.

The first of these classes comprises workrestricted machines (hammers, screw presses, etc.). Here the forming capacity has a maximum value delimited by the kinetic energy of the ram or rams immediately in advance of impact, The second of these classes embraces powerrestricted machines (hydraulic presses) in which the limiting forming load is that imposed by the power available at the hydraulic pump; in general, hydraulic presses can provide maximum forging forces at any or all points in the forging stroke.

The last of these classes consists of strokerestricted machines (for example crank, toggle and knuckle presses). Here, the kinematics of the drive mechanism determine the path-time curve of the ram head.

In the case of stroke and power-restricted machines, the machine frame has to be so designed as to withstand the maximum loads involved in forming; stroke-restricted machines can be overloaded whereas power-restricted machines cannot. In both cases there is a practical limit to the load which can be applied at a given setting and a corresponding limit to the amount of possible deformation. Multiple biows by either a stroke- or a power-restricted machine are therefore of no effect in increasing deformation beyond that yielded by the first application of load. It is this principal feature combined with a desire to maximise production that makes it necessary to use stroke-restricted equipment when considering the manufacture of workpieces with a "single hit" process.

Because of the large annular requirements for connecting rod caps, it is economical to make them on the fastest possible equipment.

Therefore, most connecting rod caps produced by conventional methods are forged on mechanical, stroke-restricted, equipment. By the conventional method the caps are normally formed on multiple impression dies where more than one end cap (normally 4, 6 or 8) can be formed from the same starting material blank and a rather large flash is generated which keeps them together and absorbs the excess material volume. After successful forging, this non-functional, interconnecting flash must be trimmed from the parts.

According to one aspect of the present invention there is provided a method of warm forging a workpiece in a closed die set comprising the steps of preparing a billet of predetermined volume, selected to be substantially equal to the volume of the desired workpiece; heating said billet to a predetermined warm forging temperature; delivering said heated billet to the female die of said die set, using the ejector of said die set when said ejector is in a predetermined intermediate position in said female die to locate said billet in the female die; using the male die acting on said billet to cause the ejector to move to a predetermined retracted position in said female die in which position a portion of said ejector will serve to define a portion of said workpiece; using said male die member to form said workpiece in a single stroke of said male die into said female die onto said billet, withdrawing said male die after said workpiece has been formed, and fully extending said ejector to eject said formed workpiece from said female die.

One of the most important elements of the invention is the use of warm forging as opposed to hot forging temperatures. The use of the lower temperatures provides the advantages of reducing and even substantially eliminating the harmful scale or oxide growth on the workpiece as well as enabling the workpiece to be produced to a high dimensional accuracy.

In conjunction with this, the reduced temperature leads to increased die pressures, therefore, an important aspect of the invention is its use of a segmented as opposed to a solid die.

In the testing carried out during the development of the invention solid dies were first tried, and despite great care in both design and usage the solid dies cracked under the severe loads imposed in producing a part of the complexity of a workpiece such as a connecting rod end cap under the conditions of the invention. The segmented die is particularly designed and has many features especially suitable for producing such workpieces, all as will be set forth in greater detail below.

Another element of the invention is the use of a closed die without a flash as opposed to an impression die or even an open die. Therefore it is, of course, dependent upon a carefully measured billet volume for use in this flashless closed segmented die. The volume of the billet, as well as its shape, must be carefully calculated so that the material in the starting billet will flow throughout the die under the single stroke pressure of the stroke restricted machine to produce the finished part. Thus two other elements of the invention are the preforming that goes into the billet, and the producing of the finished part in a single hit as opposed to successive formation with a flash with all of its attendant disadvantages.

The ejector is designed to remove the finished workpiece from the die rapidly and accurately after the workpiece is completed while at the same time forming a base on which the preformed billet for the next operation can be located so as to prevent the second billet from cocking or being other than perfectly oriented in the die in preparation for its (the second billet's) formation into a workpiece.

Another aspect of the invention provides apparatus for warm forging workpieces in a closed die set in a high speed mechanical stroke restricted press, and an ejector having a detent cooperable with the inner end of an ejector pin, - wherein the workpiece ejecting end of said ejector pin being located at a predetermined intermediate position in the female die when an opposite end of said ejector pin is on said detent, said predetermined intermediate position being such as to locate a billet in said female die in a predetermined position so that said billet is unlikely to cock when dropped into said female die, said detent being cooperable with said male die member and said billet to release said ejector pin with respect to said detent means being provided to locate said ejector pin in a predetermined retracted position in said female die when said billet begins to be formed by said male die, a portion of said ejector pin when fully retracted in said female die defining a portion of the finished workpiece, said press including means cooperable with said ejector pin to raise said ejector pin beyond said detent to an extended position to eject the workpiece from the female die, and said ejector pin being adapted to move to said predetermined position on said detent after ejection of said workpiece in preparation for the next cycle and in preparation for locating the next billet in said female die.

Many other elements go into the invention, and these include the use of suitable lubricants in the die, methods of heating the billets, the materials selected for the dies, the cooling rate of the finished workpiece, (which eliminates other subsequent steps thus further enhancing the economic advantages of the invention and the workpiece produced thereby), the speed at which the mechanical press is driven, and other lesser considerations well known to those skilled in forging techniques.

In order that the present invention may more readily be understood the following description is given, merely by way of example, with reference to the accompanying drawing in which: Figure 1 is a schematic diagram showing one embodiment of the method of the present invention; Figure 2 is a perspective view of a connecting rod end cap produced in accordance with the invention; Figures 3 to 7 are sequential views showing the formation of the cap of Figure 2 in accordance with the invention; Figures 8 and 9 are cross-sectional views of the die, taken on lines 8-8 and 9-9, respectively, of Figure 3, and showing the make-up of the female die; and Figure 10 is a schematic view illustrating the concept of operation of a tension knuckle press.

Referring now to Figure 1, there is shown a schematic diagram of one embodiment of the method of this invention. The raw material, preferably in a coil 10 of circular bar stock, is passed to a parts former or header 1 2 which produces a billet 14 of the predetermined size, shape, weight, and volume required. These billets are heated to a predetermined temperature in the 20000F (81 50C to 1 093 OC), in a heater 16. A range of 18000F--18500F (9820C to 101 00C) is warm forging temperature range of 1 500- preferred. The warm billets, now referenced 18, are then passed to the press 20 and are formed in a single stroke or "hit" of press 20, into connecting rod end caps 22 of the present invention (shown in detail in Figure 2).Finally, the still warm forging pass on to some controlled cooling means, from which they exit as substantially finished formed parts.

It is an important aspect of the present invention that because of reduced dimensional and weight fluctuations of the parts produced, the amount of finish machining can be substantially reduced.

The controlled cooling means 24 can be any of the well known means. For example, various types of tunnels with conveyor belts running through them are routinely used; such cooling means are inexpensive, and they accurately control the time related cooling of hot or warm parts.

This controlled cooling aspect of the invention provides important advantages as compared to prior art hot forging techniques.

In the automotive industry, it is preferable for the caps to be "finish machined" after they are hardened, rather than before, in order to eliminate warping during heat treating. Since a certain limited amount of machining is required even of the parts produced by the invention and, coupled with the possibility of more accurately controlling the cooling of a warm forged part, the controlled cooling means 24 is used to produce a fully heattreated part directly from the manufacturing process. Heretofore, hot forged parts were fully cooled and reheated in order to be conventionally heat treated. This separate step is combined with the manufacture, in the process shown in Figure 1, thereby imparting important ecomonic advan tages to the system employing the present invention.

The warm finished parts 22 are cooled under carefully controlled conditions down to a predetermined temperature, and then quenched conventionally, thus completing the heat-treating process and producing parts ready for the finish machining. Of course the particular conditions, such as cooling rates and temperatures, are a function of the particular material used and in any case this aspect is well within the knowledge of persons skilled in the forging arts. For manufacturing connecting rod end caps for American automobiles, the automobile manufacturers specify grade 1 541 hot rolled steel. Of course, other materials could be used in other applications, and suitable changes and adjustments in the temperatures could be made accordingly.

Referring now to Figure 2, there is shown in detail a typical end cap produced in accordance with the invention. End cap 22 comprises a counter-balancing mass portion 26 at the centre and on the side opposite to that where the bore 28 for the crankshaft pin is received. At its outer ends are "feet" 30 which have a boss portion 32 which will be drilled for receiving the bolts which attach the end cap 22 to the big end of the connecting rod proper (on the opposite side of the crankshaft pin). Between the counter-balancing mass portion 26 and the feet 30, the part 22 comprises a thinned or waisted portion 36.It is this configuration of the part 22, i.e., the relatively large amounts of metal positioned at the ends and the relatively large amount of metal at the middle but with the massive middle and ends being connected by relatively thin portions, that porduces the problem solved by the invention, i.e., producing such a cap with a single stroke of a mechanical stroke-restricted press.

The means 12 to produce the billets 14 may be a header or parts forming machine as is conventionally used in the metal forming arts. The size and shape of the billet are critical. The material is usually dictated by the customer, as set forth above. Since the billet 14 is a predetermined length, and angles and/or curves are to be formed at the extremities as needed for each particular application, the total volume is therefore also predetermined. The volume is, of course, calculated to be very nearly equal to the volume of the finished part 22 shown in Figure 2.

There are many different and often contradictory considerations. For example, the thicker the diameter of the billet is to be, so the more material flow is required. This is so because, after being struck, the material in a relatively thick billet which must be correspondingly short must flow away from the waist portions 36 and towards the heavier portions 26 and 30. On the other hand, a thinner billet permits a longer billet, but increases the possibility of the billet cocking, jamming or not landing properly in the die. This problem was solved with the use of the ejector in the press 20 which will be described in detail below and which permits the use of a relatively long billet.The ratio of the billet diameter to its length, when compared to the configuration and material distribution of the finished part, provides an enormous number of considerations and ways in which billet design affects the appearance, performance, quality, grain flow, stresses, and strength in the finished product. The ejector permits the designer a great deal more freedom.

He may make the billet to the ideal length and diameter needed for its optimal design, performance and material flow of the particular part since the spring-loaded detented ejector pin assures proper seating of the billet in the die prior to forming of the part. Another consideration for making the billet relatively long, which must of course be balanced against the considerations in determining final billet size, is that with a long billet there is less movement of material out to the ends, which movement could cause folds and discontinuities in the finished part.

For high productivity, the heater 1 6 would preferably be a direct electric heating device such as an induction or resistance heater. Such a device, with its associated short heating times, reduces scale or oxide growth as compared to a fuel-fired furnace.

Before heating, the billets are coated with a suitable lubricant which acts also as an oxide preventer or retarder. Suitable lubricants for these uses include molybdenum disulphide-and graphite-based lubricants. If fuel-fired furnaces were used instead of electrical furnaces, the lubricant might decompose or be burned off due to the increased heating time, and the surface of the part could have oxide and scale formed on it, which would detract from the finish on the parts 22 leaving the press 20. The surface finish all over the part 22 is suitable for use without further work, except for the minor amount of finish machining discussed above. This improved surface finish is one of the advantages of the invention.

The method of this invention includes the use of a particular kind of mechanical press known in the art as a tension knuckle press or "Maypres".

Such a press is shown in Figure 10. This machine is characterised by the main driving crank 38 being located below the female die (not shown), the male die 58 being located above the female die, with linkages 40, 48 connected from this crank 38 to the male die whereby the male die 58 is pulled down into the female die rather than being pushed down as in more conventional mechanical stroke-restricted presses. The machine includes tension means in the linkage between a slave crank 42 (driven by a link 40 from the main crank 38) and the male die so that any play can be taken up after the die is closed, rather than before. The tension means or backlash-absorbing means entails some tension member 48 in the nature of bands of an elastic material stretched a limited amount, but still well below their elastic limit, so that a true closed flashless die configuration is obtained.With this particular, press, it is thought that the billet weight and size can vary within a tolerance of +5% of the ideal perfect or nominal volume of material needed to fill the die to make the part 22.

With a conventional overhead push down strokerestricted type machine using a closed die flashless design, this tolerance would have had to be as low as approximately +0.5% of the ideal volume. This additional tolerance on the billet size and weight permitted by this particular press together with the other aspects of the method are instrumental in its success.

The concept as explained above is shown in more detail in the very schematic drawing of Figure 10.

The forming speed, that is the rapidity of the strokes of the male die 58 (Figure 10), is a complex variable and will be determined with consideration to many factors including: lubricating system, forging temperature, die material and die cooling. By way of example, it is anticipated that to manufacture the end cap shown in Figure 2 a forming speed in the neighbourhood of 40 strokes per minute will be attainable. This is far in excess of speeds of above 3 to 10 strokes per minute for conventional hot forging methods. In addition, the parts leaving this process do not require the trimming operations usually associated with conventional methods.

Referring now to Figures 3 to 9, the operating part of the press 20, namely the male and female dies, as well as the modus operand! are illustrated. The male die or punch 58 is a relatively simple part. It is merely the U shaped portion to form the recess 28, as well as flanks to form the bottom of the foot portions 32. This is all there is to the male die for making the end cap 22 illustrated. In other environments, more detail might need to be imparted to the male portion.

Referring to the drawings in general terms, the invention contemplates the use of a segmented die, in order to avoid problems previously encountered with a solid die used in testing carried out to prove the invention. It was found that a one piece female die could not withstand the forces produced in repeated use for producing such complicated parts in a closed die. The segmented die provides a number of features which include the use of parting lines along natural lines in the end cap, whereby the parting lines are not evident, these lines being as close as possible to the lines of maximum stress, and an ejector pin which has an operating face the same as the top face of the counter balancing mass portion 26 of the part 22, and the use of symmetrical female die pieces.

The ejector pin will form the face of the counter-balancing mass portion 26. The female die further comprises two mutually similar bottom pieces, two mutually similar end pieces, and two mutually similar side pieces. In this way, the interchangeability and replacement of parts is greatly simplified. For example only one type of end piece need be made and replacements may be held in readiness in the event of failure.

Another feature of the invention, is the use of prestressing means to hold the various female die pieces together which yields the advantages that the entire die assembly may be readily changed in order to prevent excessive down time for routine die maintenance or replacement of broken parts. Heretofore, the machine had to be stopped and several hours of labour expended to change the female die. With the technique of this invention, and the prestressed member holding a complete female die assembly together, such a die assembly can be kept as a spare and replaced very quickly. Various bolts and quick detachment means are also provided to permit this rapid die change. In tests performed to prove the invention, a complete change of the female die was accomplished in about five minutes. Along this same line the ejector pin, together with the detents used to hold it in a partially extended upright position for locating each successive billet, is also a separate module and is separately replaceable. This part can be replaced and changed independently of the female die assembly and is located as a separate member below the die assembly. The ejector pin is driven by the conventional ejection means in the press.

Another advantage of the segmented female die for manufacturing the end caps 22, is that the side pieces which form the bulk of the die but are subjected to the least amount of stress, can be replaced separately from the end pieces which can be made relatively small. The end pieces take the major part of the stress in that the material of the billet must be pushed outwardly into the crevices in these end pieces. The ends of the die which require the most frequent replacement are the smallest die pieces, again effecting great economies in the use of the invention with regard to replacement and renewal of the dies. This is coupled with the fact that the end pieces, as well as the side pieces, are identical to each other thus again effecting great economies in the manufacture of the dies.As well as cooperating with the ejector pin which forms the face of the counter-balancing mass portion 26, the five die pieces are made to mate with others along natural ISnes in the end cap, so that any flash or iine which may occur at those segments does not have any detrimental effect on performance, and only a very minimal effect on the aesthetics on the finished parts.

Referring now to the drawings in detail, the female die assembly comprises a pair of end pieces 60 (Figures 3 and 9) which are mutually identical, and a pair of side pieces 64, one of which only is shown in Figures 3 to 7. A ring 65 sits atop the side pieces 60 and 64. Much of the detail of the end cap which is of course in die parts 60, 64 and 65 has been omitted for the sake of clarity. The pieces are provided with interfitting shoulders 66 (Figure 3) which ensure that they will mate together, at least loosely in an initial assembly. Similar shoulders (not shown) are provided between the side pieces and the ends. The end and side pieces 60 and 64 fit together so as to define between themselves an opening 70 through which the ejector pin 72 fits.

Air vent slots 73 (Figures 3 and 9) are provided as is conventional. The die pieces 60, 64 and 65 are held together by a tension ring 74. It is a simple matter to adjust the shape of the die parts to accommodate the natural parting lines to fit a particular end cap.

The five die parts are assembled together in the ring 74 with a relatively light force. This assembly is in turn mounted with an extremely heavy force in a relatively larger block 76. This block 76 is the one which provides the real strength of the female die assembly. The material used has a characteristic that it is extremely strong in compression but less strong in tension.

Thus, this assembly of tension rings 74 and 76 uses this natural strength to produce an extremely strong female die. The female die is prestressed by the heavy load into block 76. The parts 60 to 76 as an assembled female die may be kept aside as a component assembly ready to be substituted in the event of any malfunction in any part of a die. This is the manner in which the great economies of the invention are achieved. It is anticipated that the assembly of the die parts in the ring 74 will be mounted into the outer main rings 76 with a pressure in the range of about 100--200 KPSI (7x108to 14X108 Pascals) preload. The preload itself is a functional element in that it aids the die in its resistance to spreading or cracking when subjected to the large forces required to form the caps and also brings the segments into intimate contact.These pressure forces are anticipated of being in the range about 250--3 50 KPSI (17.5x 108 to 24.5x 108 Pascals).

The inside of the ring part 74 is at a slight taper angle, of the order of 1/2 to 2", to the axis of the die, so that maximum force can be applied to hold the parts together.

As shown in Figure 3, a plate 78 separates the die portion from the ejector 80. The ejector is an important part of the invention. In addition to the normal function of an ejector in forging and moulding operations, in this apparatus the ejector also serves as a locating means for locating a new billet at the beginning of each operation after having ejected the finished workpiece (end cap 22) at the end of the preceding operation, and also serves as an active element in the female die itself. This greatly simplifies the automatic feeding of billets and at the same time, as described above, allows great freedom to the user as to length and diameter of the billet. Thus, the designer need not depend so heavily on the thickness and length of the billet per se to locate the billet in the die since the ejector pin serves this function when in the intermediate position.

Careful loading and accurate locating means are eliminated, and the billets can be moved over the open female die and simply dropped in, their proper location in the die being accomplished automatically because of the length of the billet and the sizes of the ejector and the other portions of the die.

The ejector includes spring-loaded detent pins 86 which hold the ejector in a partially raised position, but which, upon application of a downward force from the male die, snap out of the way to allow the ejector pin 72 to retract to permit ordinary and proper forming of the billet into an end cap. Further, jets of air or other fluid blow or otherwise remove the finished workpiece away from the die after it has been raised fully up out of the die by the ejector.

For ease of maintenance and replacement of parts, the detent pins are carried in a separate detent bushing 84 which is itself an integral and replaceable part which can be handled without unduly disturbing the entire die setup.

To these ends, the ejector 80 comprises an outer ejector ring 82 in which is carried the detent bushing 84. This bushing carries the pair of conventional spring-loaded detent pins 86. The noses of the detent pins are shaped so as to permit the detent pins to rotate in use, to even out wear, and to permit the ejector pin 72 to pass above and below the spring detent pins 86, as is evident from Figures 3 to 7.

The shank of the ejector pin 72 is of rectangular cross-section to form the end of the counter-balancing mass portion 26 of the cap when the pin 72 is fully retracted (see Figure 5).

The inner end of the ejector pin 72 has an enlarged circular portion 88, which is squared off at its inside end, and which is joined to the shank portion 90 by a frusto-conical portion 92.

The female die stack is completed by a bottom plate 94 in which is mounted an ejector driver pin 96. Driver pin 96 cooperates with a member 98 in the press, i.e., the member normally used to drive the ejector into the die.

Figure 3 shows the beginning of operations, or the beginning of the cycle during continuous operation. Some form of conventioal material conveying means 114, shown schematically in the drawing, is used, as a remote controlled clamp member. What is required is something to pick up the warm billets 18 from the heater, carry them to a predetermined location over the opening in the female die, while the male die is held raised out of the way as shown in Figure 3, and then release the billet so that it simply drops into the die.

By the instant illustrated in Figure 4, the conveying means 11 4 have retracted and are removed, the ejector pin is still held in the up position by the spring detent pins 86, and the punch stroke of the male die is about to begin.

In Figure 5 the workpiece is shown half formed. It should be noted that the ejector pin 72 has fallen below the spring detent pins 86. Some of the metal has been pushed down into the cavity between the bottom die parts and is formed by the top surface of the ejector pin shank 90 to thereby define the counter-balancing mass portion of the cap. It should be noted that at this stage the bulk of the part has a uniform thickness, all the metal required having been squeezed into the counter-balancing mass portion, and the remaining metal now in the waist portions is in the process of being squeezed outwardly to form the feet 30.

In Figure 6 the workpiece has been completed; and the male die 58 has completed its downward stroke.

In Figure 7 the ejector members 98 and 96 have been driven fully upwardly by the press, past the spring detent pins 86, and the completed part is held up above the female die and is awaiting removal.

The next cycle begins at Figure 3, by which time the parts 96 and 98 of the ejector will be in their retracted position, allowing the ejector pin 72 to fall backward to rest on the spring detent pins 86 (in the Figure 3 position) ready to locate the new billet as shown in Figure 4 and thereby to repeat the cycle.

Claims (20)

Claims

1. A method of warm forging a workpiece in a closed die set comprising the steps of preparing a billet of predetermined volume, selected to be substantially equal to the volume of the desired workpiece; heating said billet to a predetermined warm forging temperature; delivering said heated billet to the female die of said die set, using the ejector of said die set when said ejector is in a predetermined intermediate position in said female die to locate said billet in the female die; using the male die acting on said billet to cause the ejector to move to a predetermined retracted position in said female die in which position a portion of said ejector will serve to define a portion of said workpiece; using uaid male die member to form said workpiece in a single stroke of said male die into said female die onto said billet; withdrawing said male die after said workpiece has been formed; and fully extending said ejector to eject said formed workpiece from said female die.

2. A method according to claim 1 , wherein said billet is of a generally cylindrical configuration about an axis, and of a predetermined length and diameter; and wherein said billet is delivered to said female die with its axis generally perpendicular to the direction of motion of the male die.

3. A method according to claim 1 or 2, wherein said billet is heated to a temperature in the range of 1500 F to about 20000F.

4. A method according to claim 3, wherein said billet is heated to a temperature of 1 800 to 1850"F.

5. A method according to any one of claims 1 to 4, wherein said heating step is accomplished using direct electric induction heating means.

6. A method according to any one of claims 1 to 5, wherein said closed die set is mounted in a mechanical stroke-restricted press.

7. A method according to claim 6, wherein said press is of the tension-knuckle type.

8. A method according to any one of claims 1 to 7, wherein said press is operated to form said workpieces at a rate of approximately 40 pieces per minute.

9. A method according to any one of claims 1 to 8, including the additional steps of controiling the cooling of said workpieces after they are ejected from said die set, whereby the controlled cooled finished parts may be quenched and thus heat-treated to predetermined conditions without first cooling the workpieces and then re-heating them.

10. A method according to any one of the preceding claims, including the additional step of lubricating the dies and/or the billet using a molybdenum disulphide- or graphite-based lubricant.

11. A method according to any one of the preceding claims, wherein said closed die set includes a segmented female die surrounding said ejector and comprising identical end pieces, and identical side pieces.

12. A method according to any one of claims 1 to 10, wherein said closed die set includes a segmented female die formed by pre-assembling the female die parts into an assembly member whereby said female die pre-assembled in this way may be interchanged readily without unduly stopping the production of said workpiece manufacturing process.

13. A method according to any one of the preceding claims wherein said ejector is operative to retract into said fully retracted position out of contact with said billet.

14. A method according to any one of claims 1 to 13, wherein the female die is oriented with an upwardly facing opening; wherein said ejector comprises an ejector pin having an inner end cooperable with detent means adapted to hold said ejector pin in said predetermined intermediate position in said female die, and means are provided in the press in which said die set is mounted for fully extending said ejector pin to eject a finished part from said female die, said predtermined intermediate position corresponding to a position wherein said ejector pin locates a new billet in said female die to prevent said billet from cocking or taking any orientation other than a predetermined correct orientation when said new billet is dropped into said female die.

1 5. A method of warm forging complex workpieces in a closed die, wherein an ejector pin is used such that in its fully retracted position it acts as part of the mould cavity to define a portion of the workpiece; when in a predetermined intermediate position between its fully retracted and fully extended positions it acts as a locating means for a new billet put into the female die; and when moved into its fully extended position it operates conventionally for ejecting a finished workpiece.

1 6. A method of warm forging workpieces, substantially as hereinbefore described with reference to the accompanying drawings.

1 7. Apparatus for warm forging workpieces in a closed die set in a high speed mechanical stroke-restricted press, and an ejector having a detent cooperable with the inner end of an ejector pin, wherein the workpiece ejecting end of said ejector pin being located at a predetermined intermediate position in the female die when an opposite end of said ejector pin is on said detent, said predetermined intermediate position being such as to locate a billet in said female die in a predetermined position so that said billet is unlikely to cock when dropped into said female die, said detent being cooperable with said male die member and said billet to release said ejector pin with respect to said detent, means being provided to locate said ejector pin in a predetermined retracted position in said female die when said billet begins to be formed by said male die, a portion of said ejector pin when fully retracted in said female die defining a portion of the finished workpiece, said press including means cooperable with said ejector pin to raise said ejector pin beyond said detent to an extended position to eject the workpiece from the female die, and said ejector pin being adapted to move to said predetermined intermediate position on said detent after ejection of said workpiece in preparation for the next cycle and in preparation for locating the next billet in said female die.

1 8. Apparatus for warm forging workpieces, substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

19. A connecting rod cap made by the method of any one of claims 1 to 16.

New Claims or Amendments to Claims filed on 29 November 1979 Superseded Claims 1, 17-1 9.

New or Amended Claims:

1. A method of warm forging a workpiece in a closed die set comprising the steps of preparing a billet of predetermined volume, selected to be substantially equal to the volume of the desired workpiece; heating said billet to a predetermined warm forging temperature; delivering said heated billet to the female die of said die set, using the ejector of said die set when said ejector is in a predetermined intermediate position with respect to said female die to locate said billet in the female die; using the male die acting on said billet to cause the ejector to move to a predetermined retracted position in said female die out of contact with said billet in which position a portion of said ejector will serve to define a portion of the mould cavity defining said workpiece; using said male die member to form said workpiece in a single stroke of said male die into said female die onto said billet; withdrawing said male die after said workpiece has been formed; and fully extending said ejector to eject said formed workpiece from said female die.

1 7. A method according to any one of the preceding claims, wherein said workpiece is an internal combustion engine connecting rod end cap.

1 8. Apparatus for warm forging workpieces in a closed die set in a high speed mechanical stroke-restricted press, and an ejector having a detent cooperable with the inner end of an ejector pin, wherein the workpiece ejecting end of said ejector pin being located at a predetermined intermediate position in the female die when an opposite end of said ejector pin is on said detent, said predetermined intermediate positon being such as to locate a billet in said female die in a predetermined position so that said billet is unlikely to cock when dropped into said female die, said detent being cooperable with said male die member and said billet to release said ejector pin with respect to said detent, means being provided to locate said ejector pin in a predetermined retracted position in said female die when said billet begins to be formed by said male die, a portion of said ejector pin when fully retracted in said female die defining a portion of the finished workpiece, said press including means cooperable with said ejector pin to raise said ejector pin beyond said detent to an extended position to eject the workpiece from the female die, and said ejector pin being adapted to move to said predetermined intermediate position on said detent after ejection of said workpiece in preparation for the next cycle and in preparation for locating the next billet in said female die.

1 9. Apparatus for warm forging workpieces, substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

20. A connecting rod cap made by the method of any one of claims 1 to 17.