US3064507A

US3064507A - Forging process and apparatus

Info

Publication number: US3064507A
Application number: US855632A
Authority: US
Inventors: Strugala Alfred; Sporenberg Willi; Schmidt Heinz
Original assignee: Wagner und Cie AG
Current assignee: Wagner und Cie AG
Priority date: 1958-11-27
Filing date: 1959-11-27
Publication date: 1962-11-20
Anticipated expiration: 1979-11-20

Description

Nov. 20, 1962 STRUGALA ETAL 3,064,507

FORGING PROCESS AND APPARATUS Filed NOV. 2'7, 1959 Jrgvenfors:

ite rates atet filice 3,064,5W Patented Nov. 20, 1952 3,064,507 FGRGING PR$CES AND APPARATUS Alfred trugala, Dortmund, Willi Sporenberg, Dortmund- Apierbeck, and Heinz Schmidt, Dortmund, Germany,

assignors to Wagner 8; Co., Dortmund, Germany Filed Nov. 27, 1959, Ser. No. 855,632 Claims priority, application Germany Nov. 27, 1958 13 Claims. (Cl. 78-9) The present invention relates to a process and apparatus for forging articles.

In particular, the present invention relates to a process and apparatus for forging an article which after it is treated according to the process and apparatus of the invention is further treated so as to be formed eventually into articles such as hearing races, spring rings, or the like, which are not of relatively large diameter.

In the manufacture of articles of this latter type it is conventional to initially forge a member which is formed with a bore extending partly therethrough, and thereafter this member is acted on by a suitable punch so as to have the wall portion which closes the bore punched therefrom and thus to form from the member a tubular piece which may thereafter be further treated until it is finally formed into annular articles such as bearing races, spring rings, and the like.

The present invention deals with a process and apparatus for forming from a blank the initially forged workpiece which has the bore extending only partly therethrough, and it is this workpiece formed according to the process and apparatus of the invention which is further treated with machines and processes not formnig part of the present invention.

At the present time when workpieces of this type are forged they have a burr, and not only is there a considerable loss of time and increase of labor costs involved in eliminating the burr, but also the temperature of the workpiece drops undesirably during the time that the burr is being removed. It is desirable to maintain the workpiece at the elevated temperature it has at the end of the forging operation in order to facilitate the further operations such as punching out the wall which closes the bore, etc.

It is accordingly one object of the present invention to provide a process and apparatus suitable of forging a workpiece of the type referred to above without any burr thereon, so that not only is there a saving in time and a saving in labor costs, but also the temperature of the workpiece will not fall during the time required to remove a burr.

Another object of the present invention is to provide a process and apparatus according to which the workpiece will be forged with extremely precise dimensions enabling highly accurate workpieces to be produced after the wall portion closing the bore thereof is punched out, even though the initial blanks introduced into the forge vary somewhat in their dimensions.

It is still another object of the present invention to provide a forging apparatus which is simple and rugged and at the same time operates very efficiently requiring no outside source of power beyond that which is normally available for reciprocating the forging rams.

It is furthermore an object of the present invention to provide a forging apparatus which will enable the workpieces to be removed without difficulty from the forging apparatus as soon as the workpiece is forged.

It is yet another object of the present invention to provide a forging apparatus which can work efficiently with hydraulic fluid even though such a fluid does not have the capability of returning parts to their initial positions when the pressure drops.

The object of the present invention also includes the provision of a structure capable of accomplishing all of the above objects and at the same time composed of simple rugged elements which are very reliable in operation and which will have a long life during which a minimum amount of maintenance is required.

With the above objects in view the present invention includes in a forging apparatus a primary cylinder means and a piston slidable therein. The structure also includes a secondary cylinder means and a die means at least part of which is carried by the piston which is slidable in the primary cylinder means. This die means when it is in an operating position defines a closed space in which a workpiece is shaped, and the secondary cylinder means serves to guide a piercing plunger which will extend into the space of the die means when the latter is in its operating position so as to form a bore which extends part way through the workpiece. At least part of the die means is fixedly carried by the piston which slides in the primary cylinder means, and a conduit means is provided for placing the primary cylinder means and a secondary cylinder means in communication with each other at least during the time that the die means is in its operating position. Finally, a means is provided for reducing the volume of the primary cylinder means when the die means is in its operating position so as to increase the pressure of a fluid in the primary and secondary cylinder means so as to advance the plunger into the space defined by the die means when it is in its operating position.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. 1 is a fragmentary sectional elevational view of one possible forging apparatus constructed according to the present invention; and

FIG. 2 is a fragmentary sectional elevational view of another embodiment of a forging apparatus according to the present invention.

Referring to FIG. 1 there is illustrated therein a reciprocable forging ram 1 which in a Well-known manner moves up and down according to a given cycle in response to the rotation of a crank shaft. A primary cylinder means 3 is fixed to the ram 1 for vertical reciprocation therewith, this primary cylinder means 3 having a flange 2 which is fixed to the ram 1 through any suitable means such as screws, keys, or the like. A primary piston means 4 is axially slidable within the primary cylinder means 3, and the piston 4 has an extension 5 of a diameter smaller than the interior of the cylinder 3 extending outwardly beyond the latter, the cylinder 3 terminating at its bottom end, as viewed in FIG. 1, in an in wardly directed annular flange 7 engaged by the shoulder 6 of the piston 4 to limit the downward movement of the latter with respect to the cylinder 3. In the schematic illustration of FIG. 1 the shoulder 7 and the cylinder 3 are shown as being integral, although these parts can actually be made of separate members fixed to each other. The cylinder 3 is formed with a bore 8 serving as the connection for a hydraulic conduit 9.

A die means is formed in part by a die member 10 shown in FIG. 1 as forming the lower end portion of the part 5 of the piston 4. In the schematic illustration of and this surface 11 engages a surface 15 of a complementary die member 13 which is fixed to the work table of the forging press. The die member has an interior hollow space 12 and a die member 13 has an interior hollow space 14, and when the

die means

10, 13 is in operating position the surfaces '11 and 15 press against each other so as to form an interior hollow closed

space

12, 14 in which the workpiece is shaped. It is not essential to provide a separate die member 13. Instead, a simple flat plate will sufiice and in this event the surface 11 simply engages the top surface of such a flat plate.

The structure of the invention includes a secondary cylinder means which in the embodiment of FIG. 1 is formed by a bore 16 of the piston 4. The die 10 and the portion 5 of the piston 4 serve to carry for a vertical reciprocating movement a piercing plunger 18 which is fixed with a piston portion 17 sliding in the secondary cylinder means 16. The piercing plunger means 18 carries next to its piston portion 17 a collar which at its upper surface engages a shoulder within the portion 5 of piston, 4 at the bottom end of the secondary cylinder means 16, and at its top surface the collar 19 is engaged by the upper annular spring of a stack of dished annular springs cooperating together to form a spring means 20 urging the piercing plunger means 18 upwardly to the position illustrated in FIG. 1. In the schematic illustration of FIG. 1 the parts 17-19 are indicated as being of onepiece althoughin the actual construction the piercing plunger portion 18 itself is removable from element 19 and can be exchanged for other plunger portions as, for example, by being threadedly screwed onto the element 19 at a central bore of the latter.

An ejector sleeve 21 surrounds the piercing plunger 1-8 which is slidable through this ejector sleeve 21. This sleeve 21 is movable in opposition to the spring means 20. For this purpose the sleeve 21 is provided at its top end, as viewed in FIG. P1, with an annular outwardly directed flange 22 engaged by the lower annular spring of the stack of springs which form the spring means 20, and the flange 22 engages the bottom end of the chamber 23 in which the collar 19 and the spring means 20 as well as the plunger 18 are located, this chamber 23 being formed in the interior of the portion 5 of the piston 4. As is apparent from FIG. 1, in the rest position of the parts where the spring means 20 is expanded to its initial stress shown in FIG. 1 the sleeve 21 extends into the hollow inner space 12 of the die member 10.

A forged workpiece 24 is shown in dotted lines in FIG. 1, the workpiece 24 of course having a configuration determined by the configuration of the hollow interior space 12, '14 defined by the

die means

10, 13 when the latter is in its operating position. It will be noted that the workpiece 24 is not provided with a bore which extends all the way through the workpiece 24. Instead the workpiece 24 has a bottom wall portion 25 which extends across and closes this bore. It is not at all essential that this wall 25 have .a precisely determined thickness. As was pointed out above, the forged workpiece 24 is treated immediately after it is forged by having the trans verse wall portion 25 punched out, and for this reason there is no purpose in providinga wall 25 of a precisely determined thickness. The exterior surface of the workpiece 24 is composed of a pair of oppositely inclined :

Erustoconical portions

26 and 27 whose contour corresponds to that of the dies. The junction between these

frustoconical surface portions

26 and 27 is absolutely free of any bur-r. The inclination of the

frustoconical portions

26 and 27 is shown to an exaggerated degree in FIG. 1. Actually the inclination is extremely slight and the exterior surface of the workpiece is substantially cylindrical.

The structure of FIG. 1 operates as follows:

A blank in the form of a cubic or cylindrical block is cut with a length as precise as possible from a billet and after this blank, made of steel, for example, is heated to the forging temperature, it is placed on the die 13. The reciprocating forging ram 1 reciprocates up and down according to a predetermined cycle determined by a rotary crankshaft connected to the ram 1 for moving the latter up and down, and :as the 1 moves down with a workpiece placed on the die 13, the die 10 coop crates with the die 13- to shape the workpiece according to the configuration of the inner surface of the

hollow space

12, 14. It should be noted that the engagement of the blank by the die 10 while the latter approaches the die 13 does not result in a complete filling of the

interior space

12, 14 by the blank. This complete filling of the

space

12, 14 is prevented by engagement of the end face ll of the die 10 with the end face 15 of the die 13. When the die 10, and of course the piston 4 therewith, stop moving downwardly because of engagement of the surface 11 with the surface 15, the ram 1 together with the cylinder 3 continue their downward movement and the cylinder 3 therefore now slides downwardly with respect to the piston 4 so as to decrease the volume in the interior of the cylinder 3 and thus increase the pressure of the hydraulic fluid in the cylinder 3. When this pressure reaches a given value it will overcome the force of the spring means 20 and will result in the pressure of the fluid in the secondary cylinder means 16 becoming great enough to produce downward movement of 'the piston portion 17 of the piercing plunger means 18 which now moves downwardly while the spring 29 becomes compressed. Thus the piercing plunger 18 advances into the closed

hollow space

12, 14 and extends into the body of the workpiece to cause the latter to fill out all of the

space

12, 14 which is not occupied by the plunger 18. While the plunger 18 is advancing into the work material the latter engages the sleeve 21 and moves the latter upwardly in opposition to the spring 20 until the bottom face of the sleeve 21 is flush with the top end of the space 12 of the die member 10. This limiting of the upward movement of the sleeve 21 can be provided through a suitable size of the spring 20 or by provision of a suitable unillustrated stop member fixedly carried by the portion 5 of the piston 4 in the chamber 23 in a position to engage the flange 22 when the latter moves upwardly beyond the position shown in FIG. 1 through a distance suflicient to locate the bottom face of the sleeve 21 precisely at the elevation of the top end of the inner space 12. i

There will remain a lower wall portion 25 on the workpiece since the piercing ram 18 does not extend completely through the workpiece, and all of the excess material which would otherwise form a burr, for example, accumulates in the wall portion 25 whose thickness need not be precisely determined, as was pointed out above. Inasmuch as the volume of the blanks cannot be maintained constant the wall portions 25 of a series of workpieces 24 will have difierent thicknesses. Thus, With the process and apparatus of the invention this wall portion 25 will take over the function formerly performed by the burr in that the excess material of the blank will be accumulated in the wall 25 rather than in a burr. It should be noted that while when a burr is formed the thickness of the workpiece will vary depending upon the size of the burr so that it is not possible to precisely maintain the thickness of the forged piece, this disadvantage is avoided with the process and apparatus of the invention. Inasmuch as the

surfaces

11 and 15 engage each other over their entire areas at all times the length of the workpiece will correspond exactly to the length of the

space

12, 14 along the axis of the piston 4. Any variations will appear only in the thickness of the wall portion 25. For the purposes of the subsequent treatment step according to which the wall portion 25 is punched out, the thickness of the latter is immaterial and the wall portion 25 is punched out without forming any burr. Thus, with the process and apparatus of the invention the final workpiece, after the wall portion 25 is punched out in a manner not forming part of the present invention, will have very precise dimensions.

It is apparent that the thickness of the Wall portion 25 will determine the extent to which the piercing plunger 18 is advanced, since it is the thickness of the wall portion 25 which will vary with differences in the sizes of the blanks. When the plunger 18 has advanced through a distance suflicient to cause the work material to entirely till all of the

space

12, 14 except that occupied by the plunger 18 itself, then the plunger 18 will no longer be able to advance into the

space

12, 14 and the pressure of the fluid in the primary cylinder 3 and the secondary cylinder 16 will increase. The hydraulic conduit 9 carries a safety valve which can be adjusted so as to prevent the pressure from exceeding a certain predetermined maximum value, and this safety valve which is described below in connection with FIG. 2, will, when the plunger 18 can advance no further into the

space

12, 14 act to prevent the pressure of the hydraulic fluid from becoming dangerously high, and thus as the ram 1 together with the cylinder 3 move through their dead center position an excessive stressing of the parts is avoided.

During the initial upward movement of the ram 1 and primary cylinder 3 from their bottom dead center position, the spring 20 expands as the volume of the interior of the cylinder 3 increases so that the surface 11 remains in engagement with the surface 15 during this initial part of the upward movement of the ram 1 and the cylinder 3, while the spring 20 expands, and of course this expansion of the spring 26 will result in upward movement of the piston 17, collar 19, and piercing plunger 18 with respect to the die member 10 and the piston 4. Only when the plunger 18 has reached, with respect to the piston 4, the position illustrated in FIG. 1 does the die member 19 move upwardly with the ram 1 and the cylinder 3 so as to separate the surface 11 from the surface 15. However, at this time the spring 20 can still expand further by moving the flange 22 downwardly so that the ejector sleeve 21 now ejects the forged workpiece 24 from the die member 10. Inasmuch as the die member 13 is relatively flat the workpiece will not be retained by the die member 13. The workpiece is now completely free and can be treated further.

Referring now to FIG. 2, those parts which are identical with the embodiment of FIG. 1 are indicated by the same reference characters. It will be noted that in the embodiment of FIG. 2 the piercing plunger means 18 is not carried by the die member but is instead arranged within the die member 13. The die member 13 in the embodiment of FIG. 2 forms part of the work table of the forging press and a sleeve 29 of a slide valve 28 is fixedly carried by this work table. The outer sleeve 29 of the slide valve communicates with a conduit 30 which leads to the secondary cylinder means 31 of the embodiment of FIG. 2, and also the conduit 30 leads to an expansion tank 32 where a body of air 33 is located over the hydraulic liquid so that the body of air can expand and contract as is well known. The secondary cylinder 31 is shown schematically as being one-piece with the die 13 which forms the work table, but actually the secondary cylinder 31 is threaded onto the work table. The same applies to the expansion tank 32 whose size and location are illustrated only schematically. A nonreturn valve 34 communicates with the tank 32 and this non-return valve 34 opens when the pressure in the conduit means 39 is smaller than the pressure in the tank 32. A safety valve 35 already referred to above in connection with FIG. 1, this being the safety valve which is connected to conduit 9 of FIG. 1 so as to determine the maximum pressure of the hydraulic fluid in the primary cylinder 3 and the secondary cylinder 16, is illustrated in FIG. 2 connected to the conduit 30 as well as to the tank 32 so that the liquid which flows through the safety valve 35 will enter into the tank 32, and thus the hydraulic systems of both embodiments of the invention are closed systems. The tank 32 is also included in the embodiment of FIG. 1 and also cooperates with the safety valve and the non-return valve in the manner illustrated in FIG. 2, the non-return valve 34 communicating with the conduit 9 in the embodiment of FIG. 1. The non-return valve includes an adjusting screw 36 which is very carefully set so as to regulate the maximum pressure of the fluid at which the safety valve will open. 33 is a body of air in the tank 32.

The slide valve 28 is formed at an intermediate region with an annular groove 37 into which a bore 38 formed in the slide valve 28 empties. This bore 38 extends through the bar 39 which is fixed to the slide valve 28 at the upper end thereof, as viewed in FIG. 2, and the bore 38 communicates at its top end with the conduit 9 which leads through the passage 8 into the primary cylinder 3, as described above. A bracket 40 which is fixed to the ram 1 carries the bar 39.

The structure of FIG. 2 operates in the manner corresponding to the structure of FIG. 1. The workpiece is of course placed within the area surrounded by the top annular surface 15 of the die member 13, and this workpiece will become located in the

space

12, 14 when the die member Iii engages in its bottom end face 11 the annular surface 15. Of course, after the surface 11 engages the surface 15 the continued downward movement of the primary cylinder 3 will result in an increase in the pressure of the fluid, and of course the workpiece may be initially deformed before the die member 10 engages the die member 13 while the surface 11 approaches the surface 15. Thus, the continued downward move ment of the cylinder 3 after the die means 10, 13 has reached its operating position will cause the fluid whose pressure is increased in this Way to act in the secondary cylinder 1 on the piston portion 17 of the piercing plunger means 18. Of course, when the surface 11 is close to and in engagement with the surface 15 the annular groove 37 communicates with the conduit 30 so that at this time the primary cylinder 3 and the secondary cylinder 31 are in communication with each other. Thus, the piercing plunger 18 will advance into the

space

12, 14 and the workpiece 24 will be forged in the manner described above in connection with FIG. 1, the only difference being that the transverse wall portion 25 which closes the bore willbe located at the top end of the workpiece rather than at the bottom end thereof, as illustrated in FIG. 1. As soon as the advance of the piercing plunger into the

space

12, 14 has terminated the continued movement of the ram 1 and the cylinder 3 down to and through their bottom dead center position will of course continue to increase the fluid pressure and at this time the safety valve 35 will automatically open so that the fluid can now flow from the cylinder 3 through the conduit means into the tank 32. During the upward return of the ram 1 and cylinder 3 toward their top dead center positions the spring 20 will expand, as described above in connection with FIG. 1, so as to return the piercing plunger 18 to its starting position illustrated in FIG. 2 and then the valve 34 will open either because of the pressure of the body of air 33 or as the result of the action of an unillustrated return spring which may be provided in the cylinder 3 acting on the piston 4 of the embodiment of FIG. 2 to urge this piston to the position illustrated in FIG. 2.

It will be noted that with the structure of the invention there is no additional drive beyond the already -avail able drive for reciprocating the ram 1. The force which acts on the piercing plunger is derived from the downward movement of the ram 1. If desired the structure may be pneumatic instead of hydraulic, although the hydraulic arrangement is preferred, and with the structure of the invention the fact that there are no particular return springs with the hydraulic structure is of no moment.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of forging apparatus and process differing from the types described above.

While the invention has been'illustrated and described as embodied in hydraulic forging apparatus and process, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any Way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can be applying current knowledge readily adapt it for various applications without omiting features that, from the:

standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intendedtobe comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a forge, in combination, primary cylinder means; a piston slidable in said primary cylinder means, the latter being adapted to have a fluid under pressure therein; secondary cylinder means; a piercing plunger means having a portion which forms a piston in said secondary cylin der means; die means forming a hollow space, when said die means is in an operative position, with which said plunger communicates, said die means including at least one die fixed with said piston which is slidable in said primary cylinder; means providing communication between said primary and secondary cylinders when said die means is in said operating position thereof; and means cooperating with said primary cylinder for reducing the volume thereof when said die means is in said operative position so as to increase the fluid pressure within said primary cylinder and thus increase the fluid pressure within said secondary cylinder so as to advance said plunger into the hollow space of said die means to operate a workpiece.

2. In a forge, in combination, primary cylinder means; a. piston slidable in said primary cylinder means, the latter being adapted to have a fluid under pressure therein; secondary cylinder means; a piercing plunger means having a portion which forms a piston in said secondary cylinder means; die means forming a hollow space, when said die means is in an operative position, with which said plunger communicates, said die means including at least one die fixed with said piston which is slidable in said primary cylinder; means providing communication between said primary and secondary cylinders when said die means is in said operating position thereof; means cooperating with said primary cylinder for reducing the volume thereof when said die means is in said operative position so as to increase the fluid pressure within said primary cylinder and thus increase the fluid pressure within said secondary cylinder so as to advance said plunger into the hollow space of said die means to operate a workpiece; and spring means cooperating with said plunger for retracting the latter out of said space and for urging said plunger to a predetermined rest position.

3. In a forge, in' combination, primary cylinder means; a piston slidable in said primary cylinder means, the latter being adapted to have a fluid under pressure therein; secondary cylinder means; a piercing plunger means having a portion which forms a piston in said secondary cylinder means; die means forming a hollow space, when said die means is in an operative position, with which said plunger communicates, said die means including at least one die fixed with said piston which is slidable in said primary cylinder; means providing communication be- 'tween said primary and secondary cylinders when said die means is in said operating position thereof; and means cooperating with said primary cylinder for reducing the' volume thereof when said die means is in said operative position so as to increase the fluid pressure within said primary cylinder and thus increase the fluid pressure within said secondary cylinder so as to advance said plunger into the hollow space of said die means to operate a workpiece, said means for reducing the volume of said primary cylinder including a reciprocable forging ram which fiXably carries said primary cylinder.

4. In a forge, in combination; primary cylinder means; a piston slidable in said primary cylinder means, the latter being adapted to have a fluid under pressure therein; secondary cylinder means; a piercing plunger means having a portion which forms a piston in said secondary cylinder means; die means forming a hollow space, when said die means is in an operative position, with which said plunger communicates, said die means including at least one die fixed with said piston which is slidable in said primary cylinder; means providing communication between said primary and secondary cylinders when said die means is in said operating position thereof; means cooperating with said primary cylinder for reducing the volume thereof when said die means is in said operative position so as to increase the fluid pressure within said primary cylinder and thus increase the fluid pressure within said secondary cylinder so as to advance said plunger into the hollow space of said die means to operate a workpiece; conduit means communicating at least with said primary cylinder for supplying hydraulic fluid thereto; and safety valve means carried by said conduit means for determining the maximum pressure within said primary cylinder means.

5. In a forge, in combination, primary cylinder means; a piston slidable in said primary cylinder means, the latter being adapted to have a fluid under pressure therein; secondary cylinder means; a piercing plunger means having a portion which forms a piston in said secondary cylinder means; die means forming a hollow space, when said die means is in an operative position, with which said plunger communicates, said die means including at least one die fixed with said piston which is slidable in said primary cylinder; means providing communication between said primary and secondary cylinders when said die means is in said operating position thereof; and meanscoopei'ating with said primary cylinder for reducing the volume thereof when said die means is in said operative position so as to increase the fluid pressure Within said primary cylinder and thus increase the fluid pressure within said secondary cylinder so as to advance said plunger into the hollow space of said die means to operate a workpiece, said secondary cylinder means being in the form of a bore of said piston in said primary cylinder means.

6. A forging apparatus comprising, in combination, primary cylinder means adapted to contain a fluid under pressure; a piston slidable in said primary cylinder means; a worktable; a secondary cylinder means carried by'said worktable; a piercing plunger slidable in said secondary cylinder means; a reciprocable forging ram carrying said primary cylinder means; die means carried at least in part by said piston and having a closed position defining a space communicating with said piercing plunger; and conduit means part of which moves with said primary cylinder means, said conduit means providing communication between said primary and secondary cylinder means when said die means is in said closed position thereof.

7. A forging apparatus comprising, in combination, primary cylinder means adapted to contain a fluid under pressure; a piston slidable in said primary cylinder means; a worktable; a secondary cylinder means carried by said worktable; a piercing plunger slidable in said secondary cylinder means; a reciprocable forging ram carrying said primary cylinder means; die means carried at least in part by said piston and having a closed position defining a space communicating with said piercing plunger; and conduit means part of which moves with said primary cylinder means, said conduit means providing communication between said primary and secondary cylinder means when said die means is in said closed position thereof, said conduit means including a slide valve composed of a stationary outer member and a movable inner member, said movable inner member forming the part of said conduit means which is connected with said primary cylinder means for movement therewith.

8. In a forging apparatus, in combination, a die having a hollow space in which a workpiece is shaped; a piercing plunger slidably carried by said die; an ejector sleeve also slidably carried by said die, said plunger extending slidably through said sleeve; and spring means cooperating with said sleeve for urging the latter to a rest position where part of said sleeve extends into said space.

9. In a forging apparatus, in combination, a die having a hollow space in which a workpiece is shaped; a piercing plunger slidably carried by said die; an ejector sleeve also slidably carried by said die, said plunger extending slidably through said sleeve; and spring means cooperating with said sleeve for urging the latter to a rest position where part of said sleeve extends into said space, said sleeve having a flange engaged by said spring means and engaging a shoulder of said die.

10. In a forging apparatus, in combination, a primary cylinder; a reciprocable forging ram carrying said primary cylinder; a piston slidable in said primary cylinder; die means part of which is fixed to said piston; and stop means located in the path of movement of said die means during downward movement of said forging ram to stop the movement of said die means while said forging ram continues to move downwardly so that said primary cylinder means will move downwardly with respect to said piston to reduce the volume of said primary cylinder means and thus increase the pressure of a fluid therein.

11. In a forging apparatus, in combination, a primary cylinder; a reciprocable forging ram carrying said primary cylinder; a piston slidable in said primary cylinder; die means part of which is fixed to said piston; stop means located in the path of movement of said die means during downward movement of said forging ram to stop' the movement of said die means while said forging ram continues to move downwardly so that said primary cylinder means will move downwardly with respect to said piston to reduce the volume of said primary cylinder means and thus increase the pressure of a fluid therein; secondary cylinder means; a piercing plunger slidably carried by said secondary cylinder means and communicating with the interior of the die means; and conduit means providing communication between said primary and secondary cylinder means at least when said stop means has stopped the movement of said die means so that during the continued downward movement of said primary cylinder means with 1G respect to said piston the fluid under pressure will act in said secondary cylinder means on said piercing plunger to actuate the latter.

12. In a forging apparatus, in combination, a pair of die members cooperating with each other to define a hollow closed space when said die members are in an operative position, said die members respectively having surfaces engaging each other when said die members are in their operative position; piercing plunger means slidably carried by at least one of said die members for movement into the space defined by said die members when the latter are in their operating position so as to form in a workpiece a bore which does not extend completely through the workpiece; and means cooperating with said plunger means for moving the same into said space until the workpiece fills that portion of the space which is not occupied by said plunger means, said means for moving said plunger means into said space stopping the advance of said plunger means into said space when the workpiece fills all of the space which is not occupied by said plunger means, so that there will be no burr formed on the workpiece at the place where said pair of die members engage each other.

13. In a forging apparatus, in combination, a pair of die members having an operating position pressing against each other to define a hollow space in which a workpiece is shaped; piercing plunger means slidably carried by at least one of said die members for movement in said space; hydraulic means cooperating with said plunger means to advance the latter into said space until all of the space which is not occupied by said plunger means is occupied by the workpiece with said plunger means extending only part way through the workpiece; and safety valve means cooperating with said hydraulic means to limit the pressure of the fluid acting on said plunger means to a value which will stop the movement of said plunger means irrespective of the distance the latter has advanced into said space when said space is filled by the workpiece except for the portion of said space occupied by said plunger means, whereby the workpiece will not have a burr,

References Cited in the file of this patent UNITED STATES PATENTS 1,971,937 Keck Aug. 28, 1934 2,319,373 Tormyn May 8, 1943 2,482,280 Lerma Sept. 20, 1949 2,809,395 Gregory Oct. 15, 1957 2,909,955 Williams Oct. 27, 1959 FOREIGN PATENTS 553,703 Italy Jan. 2, 1957 794,375 Great Britain Apr. 30, 1958