WO1997005977A1

WO1997005977A1 - Method and machine for making rod-shaped objects having ends with increased thickness, especially anchor bolts for concrete

Info

Publication number: WO1997005977A1
Application number: PCT/DK1995/000326
Authority: WO
Inventors: Laurids A. Jessen
Original assignee: Jessen Laurids A
Priority date: 1995-08-10
Filing date: 1995-08-10
Publication date: 1997-02-20
Also published as: AU3161495A

Abstract

In a method of making objects (1) of the kind consisting of an elongated shank (2) of generally constant thickness and having in each end a part with increased thickness, e.g. a head (3) in one end and a foot (4) in the other, said method being of the kind comprising the following steps a and b: a) a number of blanks (2') are cut from elongate stock of substantially constant thickness, b) the ends of the individual blanks are subjected to a cold-shaping process so as to form in each end a part with increased thickness, e.g. a head (3) and a foot (4), the most important novel feature is c) that on each object or workpiece, the parts (3, 4) wih increased thickness are formed simultaneously by the two ends of the object being acted upon in opposite directions, while the object is guided substantially freely movable in the longitudinal direction of the shaft (2). The invention also concerns a machine for carrying out the method.

Description

METHOD AND MACHINE FOR MAKING ROD-SHAPED OBJECTS HAVING ENDS WITH INCREASED THICKNESS. ESPECIALLY ANCHOR BOLTS FOR CONCRETE

TECHNICAL FIELD

The present invention relates to a method of making rod- shaped objects having ends with increased thickness, such as set forth in detail in the preamble of claim 1.

In the following, the invention will be explained with reference to the manufacture of anchor bolts for concrete, but the invention may in principle be used for manufac¬ turing other objects consisting of a rod-shaped body having a part with increased thickness in each end.

BACKGROUND ART

Studies in the relevant literature and experiments have shown that forming the ends with increased thickness by means of cold shaping offers certain advantages compared to e.g. hot forging or other methods.

As will be well-known, heads on ordinary nails are nor- mally formed in a cold upsetting process, a piece of wire of suitable length being held between a set of jaws and acted upon by impact, thus forming the head. For such a purpose it is necessary that the holding force of the jaws is very large, usually evidenced by the gripping marks found immediately below the heads on most nails.

The most commonly used anchor bolts for concrete normal¬ ly have a diameter on the shank of at least approximately 8 mm, and it will be obvious that if a head were to be formed on a blank with such a thickness in the same manner as described for nails, extremely strong and strongly supported jaws would be needed for holding the blank.

DISCLOSURE OF THE INVENTION

In contrast to ordinary nails, anchor bolts for concrete do, however, have a part with increased thickness in both ends, e.g. a "head" and a "foot", respectively, and this fact is exploited in the present method, according to the invention being characterized by proceeding as set forth in the characterizing clause of claim 1.

Since, when carrying out the method according to the in- vention, the very large forces used for forming the thick end parts on the blank are directed in opposite directions and occur simultaneously, they will substantially balance each other out, so that the holding of the blanks may be replaced by simply guiding them in the longitudinal direc- tion.

The present invention also relates to a machine for car¬ rying out the method according to the invention. This machine is of the kind set forth in the preamble of claim 6, and according to the invention it is characterized by the features set forth in the characterizing clause of this claim 6.

Advantageous embodiments of the method and the machine, the effects of which - beyond what is self-evident - are explained in the following detailed portion of the present description, are set forth in claims 2-5 and 7-11, re¬ spectively. BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed portion of the present descrip¬ tion, the invention will be explained in more detail with reference to the exemplary embodiments of a machine for carrying out the method according to the invention shown in the drawing, in which

Figure 1 is a perspective view of an anchor bolt for concrete of the kind to be manufactured, Figure 2 in a diagrammatic manner shows the principle of carrying out the method,

Figure 3 shows the most important parts of the machine seen from above in perspective, Figure 4 is a perspective view of one of the holding-die halves that may be inserted in the die rings in the ma¬ chine shown in Figure 3,

Figure 5 shows a die recess, in which the holding-die half shown in Figure 4 may be inserted, Figure 6 shows an example of a shaping die, with which the ends of the blanks are worked in a cold-shaping pro¬ cess,

Figure 7 as seen from above in perspective shows the bearing means for the processing rotors or rollers of the machine, and Figure 8 likewise seen from above in perspective and from the opposite side relative to Figure 7 shows the drive means for said rotors or rollers.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Figure 1 shows an exemplary embodiment of an anchor bolt 1 for concrete of the type, with which the present in¬ vention is concerned, and which in a known manner consists of a shank 2, one end of which is formed as a head 3, whereas the other end is formed as a foot 4. The whole anchor bolt 1 is normally shaped with rotational symmetry about a longitudinal axis 5, even though other shapes are possible within the scope of the invention.

Figure 2 shows the principle for the formation of the head 3 and the foot 4, in the example shown divided into four stages I-IV. In stage I, a blank rod 2* is placed in a holding die 6, in which it is held or at least guided during the three succeeding stages II-IV, during which the upper end of the blank rod 2' is subjected to a step¬ wise upsetting operation by means of a tool (not shown) so as to form the head 3 in stage IV, at the same time as the lower end by means of another tool (likewise not shown) is subjected to a stepwise upsetting operation so as to form the foot 4 in stage IV. In the machine to be described below, the two tools mentioned but not shown are constituted by shaping dies placed in the periphery of two rotors or rollers adapted to rotate about axes extending at right angles to the plane of the drawing, this being the cause of the inclined end surfaces of the unfinished blank in stage II. Thus, carrying out the process using a cylindrical rotor or roller will impose a limitation on the maximum deformation, as the protruding ends of the blank rod will be subjected to bending, if the angle of entry at the start of the shaping process exceeds a certain magnitude of typically 12°. The angle of entry depends on the length of the blank rod to be shaped and on the diameter of the rotor or roller. The length of the part of the blank rod to be deformed depends on the volume of the head to be formed, but a small dia¬ meter of the rotors or rollers is desirable, as this reduces the forces involved. By using a number of shaping stages - this also being necessary for manufacturing the anchor bolts - the shaping die used in stage II may be set at an angle, so that the plane surface on the shaping die hitting the blank is not at right angles to the radius of the rotor or roller. In this manner, the angle of entry is reduced and the degree of deformation can be increased, making it possible to reduce the number of shaping stages or to reduce the degree of deformation and hence the force in the last stage. In stage III, in which the blank is more resistant to bending, it is pos- sible to deform the end in such a manner, that the end surface of the head is again at right angles to the lon¬ gitudinal axis. In other words: the inclined surfaces in stage II are due to the compensation on the shaping die with a view to reducing the angle of entry at a given degree of deformation.

The foot 4 is formed in the same manner as the head 3 by means of a tool, the force of which acts in the opposite direction, at the same time as and with a force of at least approximately the same magnitude as the force, with which the head 3 is formed, so that the forces acting on the blank will be roughly the same above and below. For this reason, it is possible to secure the holding die 6 by means of relatively "light" means, while the blank in principle "floats" between the two shaping tools, thus requiring no holding as such. The at least approxi¬ mate equilibrium of forces is due to the use of a rolling process capable of being optimized in such a manner, that the two areas of deformation and hence the force are approximately equal. This is not possible in traditional forging processes, in which the total areas on the head and the foot, respectively, are in contact with the sha¬ ping tools. When forging anchor bolts of the type de¬ scribed in the traditional manner, the force at the foot will be approximately twice that at the head. In this connection, forging can be described as shaping in a single stage or stroke, whilst rolling is a progressive shaping in a number of stages.

Figure 3 shows the essential parts of the machine, with which it is possible to produce anchor bolts 1 of the shape shown in Figure 1 according to the principle illu¬ strated in Figure 2. For the sake of clearness, Figure 3 does not show the blank rods 2 ' , the more or less finished anchor bolts 1, nor the holding dies 6. For this reason, it is relevant first to mention a number of inner die recesses 7 and outer die recesses 8, formed in an inner die ring 9 and an outer die ring 10, respectively. The inner die ring 9 has an outside diameter somewhat smaller than the inside diameter of the outer die ring 10 and is placed excentrically relative to the latter, so that when the two die rings 9 and 10 rotate about their respective vertical axes of rotation (not shown) , there will be a space between the two die rings on the right-hand side in Figure 3, whilst at the opposite side the two die rings will lie very close together or touch each other.

At the location, in which the die rings 9 and 10 are very close together or touching each other, an upper rotor or roller 11 and a lower rotor or roller 12 are placed above and below the die rings 9 and 10. On their peripheries, the rollers 11 and 12 carry a number of upper shaping dies 13 and lower shaping dies 14, respec- tively, constituting the shaping tools referred to, but not shown, in connection with Figure 2.

The inner die ring is rotatably supported on an inner bearing disk 15, whilst the outer die ring 10 is rotatably supported on an outer bearing ring 16. The inner bearing disk 15 is secured to a table top 19 by means of screws 17 and distance pieces (not visible) , whilst the outer bearing ring 16 is elastically supported on the table top 19, partly by means of guide pins 20 carrying springs 21, partly by means of wedges 22 being connected to the table top 19 by means of springs 23.

The two rollers 11 and 12 are rotatably supported close to the upper and lower ends, respectively, of a pair of roller bearing uprights 24 and 25 extending both up above and down below the table top 19.

By means of a gearbox (not shown) , the inner die ring 9 is adapted to be rotated in the direction shown by the arrow 27, and during this movement, it will carry the outer die ring 12 with it, because the blank rods 2* (not shown) , having been inserted at a short distance upstream of the roller nip at the location marked 28, will co-operate with the holding die halves (not shown) placed in the inner and outer die recesses 7 and 8, re¬ spectively, so as in effect to couple the two die rings to each other.

When the blank rods 2' have been inserted between the holding-die halves at the place of insertion 28, the inner die ring 9 will carry them towards the roller nip between the two rollers 11 and 12, the shaping dies 13 and 14, respectively, of which will upset the two ends of the blank rods in the manner explained with reference to Figure 2. The blanks having been shaped are conveyed further to a location, at which the distance between the holding-die halves is greater, as e.g. to the extreme right in Figure 3, where an ejector disk 29 rotatable about a horizontal axis protrudes downwardly between the two die rings 9 and 10.

In principle, the blanks may be worked batchwise in a number of turns, and if so, it is obviously necessary to insert the partly processed blanks, if these have been ejected after a previous turn, sufficiently far upstream from the roller nip for the distance between the die rings 9 and 10 to be large enough to allow them being in- serted. As will be explained below, it is, however, pre¬ ferred according to the invention that multi-stage pro¬ cessing is carried out in continuous operation.

The machine is preferably equipped with sensors (not shown) for sensing the movements of the outer bearing ring 16. Such sensors may be used for sounding an alarm and/or stop the machine, if the outer bearing ring carries out movements possibly due to overloading, e.g. due to incorrect starting material or operator errors. When needed, the outer bearing ring 16 may be trued up by means of suitable tools (not shown) that may be anchored in holes 30 in the table top 19.

In the exemplary embodiment shown, the inner bearing disk 15 is rigidly secured to the table top 19, but in an embodiment not shown, the inner bearing disk 15 may also be elastically supported and adapted to co-operate with sensors in the same manner as described above with reference to the outer bearing ring 16.

When the blank rods 2• are inserted in the spaces between the holding-die halves at the place of insertion 28, the lowermost ends will engage an adjustable skid (not shown) guiding them in the vertical direction towards the roller nip, where in the first instance they will be supported by the upwardly facing lower shaping dies on the lower roller 12.

As mentioned above, it is also possible in continuous operation to pass the blanks through the roller nip a number of times, as for this purpose, the number of hol¬ ding-die halves in the inner die ring 9 is attuned to the number of shaping dies 13, 14 in the rollers 11, 12 in such a manner, that each blank during a first pass is worked by a first pair of shaping dies, e.g. leading to a situation corresponding to stage II in Figure 2, during the next pass being worked by a second pair of shaping dies to achieve the situation corresponding to stage III in Figure 2, and finally a third pass with working by a further pair of shaping dies for achieving the final shape as indicated by stage IV in Figure 2.

In the exemplary embodiment shown, each roller comprises twelve shaping dies, whilst the number of holding-die halves in the inner die ring 9 is twenty-three, i.e. one less than two times twelve. This means that for each two revolutions of the rollers, a relative displacement be¬ tween them and the inner die ring corresponding to one die interspace will occur. In this manner it is possible for a blank having been worked by a first pair of shaping dies during a first pass to go through a second pass whilst being worked by a second pair of shaping dies being neighbours to the first pair, and so forth.

From Figure 2 it will also be seen that the head 3 does not attain its full width until εtage IV. This fact may be utilized by placing the ejector disk 29 in such a position relative to the inner die ring 9 that it does not engage the heads 3 until these have attained their full width; in this manner it is ensured that the anchor bolts 1 will be ejected when they are finished, but not before.

Since the holding-die halves, of which a single one 31 is shown in Figure 4, will necessarily be moved away from each other during the movement away from the roller nip, it is necessary in some way or another to retain the blanks in the holding-die halves in the inner die ring 19 with a sufficient force to prevent them from falling out. Such retaining may most easily be achieved, if the blanks consist of ferromagnetic material, by embedding suitable holding magnets (not shown) in the holding-die halves in the inner die ring 9. If the blanks are not ferromagnetic, what e.g. applies to certain types of stainless steel, the retaining may be achieved pneumati¬ cally, e.g. by means of suction holes (not shown) in the holding-die halves concerned connected to a suitable source of vacuum, or else mechanically, e.g. by means of a bead or snap spring (not shown) adapted to engage the blank outside of the semi-cylindrical recess in the hold¬ ing-die half occupied by the blank. In the latter case it is necessary to provide a recess in the co-operating outer holding-die half to accommodate the snap spring, and also to construct the latter in such a manner that it will recede when the blank rod 2 • is inserted from above. Persons skilled in this technology will know how to implement these solutions in practice, for which reason they will not be described in detail here. According to the invention it is, however, preferred to provide an upwardly facing surface in the holding-die halves 31 in the inner die ring 9 with recesses or projections, during the shaping process necessarily forming and engaging corresponding projections or recesses, respectively, in a corresponding downwardly facing surface on the blank. As may be seen from Figure 1, a projection 3a is formed on the lower side of the head 3. This projection is formed by means of the recess 3la shown in Figure 4 being formed in the uppermost end of the holding-die half 31, this solely applying to the holding-die halves belonging to the inner die ring 9. The projection 3a shown is wedge-shaped, but the projection may also be constituted by a character or sign, such as the manufacturer's logo, possibly in a simplified version. What is important for the present process is that the engagement between the recess 31a in the inner holding-die half 31 and the projection 3a on the lower side of the head 3 on the one hand is sufficient to retain the blank in abutment against the inner holding- die half, but on the other hand does not prevent the finished bolt from being ejected, e.g. by means of the ejector disk 29 or other ejecting means (not shown) .

As mentioned above, Figure 5 shows a segment of the inner die ring 9 with an inner die recess 7. On each side of the die recess there is a threaded bore 32, countersunk with a view to receiving a pair of screws with countersunk heads (not shown) co-operating with chamfer surfaces 33 on the holding-die half 31 shown in Figure 4. In fact it is sufficient to loosen one of the two screws when the holding-die halves 31 are to be replaced, as it iε pos¬ sible to turn the latter free at the side of the loosened screw, after which it is poεsible to swing it out from the die recess 7. The same applieε to the holding-die halves (not shown) occupying the outer die recesses 8 in the outer die ring 10.

Figure 6 shows an example of a shaping die 13 or 14 for insertion in a roller 11 or 12, respectively. The shaft of this die comprises two pointed-screw recesses 34 adap¬ ted to co-operate with pointed screws with 90° points in the roller, the axes of which are offset toward the bottom of the bore, in which the die is to be inserted, so that tightening of the pointed screws causes the piston to be drawn inwardly into the bore, preferably against the action of a disk spring (not shown) , the latter when the pointed screws are unscrewed pusheε the die outwardly through a small distance, thus facilitating removal.

Figure 7 shows how the two rollers 11 and 12 are rotatably supported. Since the two rollers are supported in sub¬ stantially the same manner, only the manner in which the upper roller 11 is supported will be described.

Thus, the upper roller 11 is supported in two bearing housings 35 with double-spherical bearings, so that they can carry both radial and axial loads. The bearing hous- ingε 35 may be adjusted vertically with a view to adjust¬ ing the height of the roller concerned relative to the die rings 9 and 10 by means of slides 36 adjustable by means of spindles 37, of which solely the heads may be seen.

The drive means for the rollers 11 and 12 will now be described with reference to Figure 8. It should be em¬ phasized that since the rollers are to follow each other's movements accurately, the drive means are adapted to provide a mechanical interlocking of the movements of the rollers.

A main motor 39 which - depending on the diameter of the head and the foot of each anchor bolt to be made - may have a power in the interval 10-100 kW, drives a gearbox 40 secured to the machine's base plate 42. The gearbox 40 is connected to two intermediate shafts 43, the latter driving the roller shafts (not visible in the drawing) through planet gears 44. At each end, the intermediate shafts 43 have flexible couplings 45 of a known type with limited flexibility in order to allow vertical ad¬ justment of the rollers 11 and 12.

The planet gears 44 must also, of course, allow vertical adjustment of the rollers, and for this purpose, each of them is held against rotation solely by a holding plate 50, in a known manner co-operating translatably but non- rotatably with the machine frame, e.g. by means of a slot-pin combination.

The rotational movements of the rollers are sensed by suitable means (not shown) controlling a servo motor 38, the latter driving the inner die ring 9 through the gear- box (not shown) referred to in connection with Figure 3. In this manner it is possible to ensure that the blanks placed in the holding dieε are at all times in the correct position and move with the correct speed relative to the shaping dies 13 and 14 working on them.

The means (not shown) , with which the blank rods 2 ' are inεerted at the place of inεertion 28, may advantageously be controlled by a sensor adapted to be acted upon by the finished anchor bolts being ejected by the ejector disk 29. In this manner, it is posεible to avoid that blank rods are inserted - or rather attempted to be in¬ serted - into dieε, from which the previouε workpiece haε not yet been removed. Also with regard to these means, persons skilled in the art will be able to choose and/or design such means without further guidance from the pres¬ ent description.

The servo motor 38 referred to in connection with Figure 8 is advantageously controlled in such a manner, that when the shaping dies 13 and 14 come into contact with the workpieces conveyed by the inner die ring 9, the speed of the workpieces will be slightly lower than that of the shaping dies. This causes the frictional forces between the shaping dies and the workpieces to counteract a tendency towards bending the ends of the workpieceε oppoεite to the direction of movement.

In connection with thiε control of the servo motor 38 the arrangement can be such that the driving of the inner die ring 9 through the gearbox 26 is released aε εoon as the pair of shaping dies in question has begun to deform the workpiece, and to be re-established after the end of the deforming process, so that the next workpiece may be conveyed forward with the correct speed and position relative to the next pair of shaping dies.

To prevent the fingers of the operating personnel or e.g. tools from being caught between the two die rings 9 and 10, the machine should be suitably encased in a known manner (not shown) . This will, of course, also apply to the intermediate shafts 43 and posεibly the meanε (not εhown) for εupplying blank rods and removing finiεhed anchor boltε. LIST OF PARTS

1 anchor bolt

2 εhank

2' blank rod

3 head

3a projection

4 foot

5 longitudinal axiε

6 holding die

7 inner die recess

8 outer die recess

9 inner die ring

10 outer die ring

11 upper roller

12 lower roller

13 upper shaping die

14 lower shaping die

15 inner bearing disk

16 outer bearing ring

17 screws

19 table top

20 guide pins

21 springε

22 wedgeε

23 εprings

24 inner roller bearing upright

25 outer roller bearing upright

27 arrow

28 place of insertion

29 ejector disk

30 holes

31 holding-die half

31a recesε

32 threaded bore 33 chamfer surface

34 pointed-screw recess

35 bearing housing

36 slide 37 spindle

38 servo motor

39 main motor

40 gearbox

42 base plate 43 intermediate εhaft

44 planet gear

45 flexible coupling 50 holding plate

Claims

C L A I M S:

1. Method of making objects (1) of the kind consisting of an elongated shank (2) of generally constant thickneεε and having in each end a part with increaεed thickness, e.g. a head (3) in one end and a foot (4) in the other, said method being of the kind comprising the following stepε a and b: a) a number of blanks (2¹) are cut from elongate εtock of εubεtantially constant thickness, b) the ends of the individual blanks are subjected to a cold-shaping proceεε so as to form in each end a part with increased thickness, e.g. a head (3) and a foot (4) , c h a r a c t e r i z e d in c) that on each object or workpiece, the parts (3,4) with increased thickness are formed simultaneouεly by the two ends of the object being acted upon in opposite directions, while the object is guided subεtantially freely movable in the longitudinal direction of the shaft (2) .

2. Method according to claim 1, c h a r a c t e r¬ i z e d in that the process of acting upon the two ends of the object is controlled in such a manner that said two ends are acted upon with forces of substantially equal magnitude.

3. Method according to claim l or 2, c h a r a c- t e r i z e d in that the object is guided by means of a longitudinally divisible die, the latter being divided after the processing of the object so as to release the at least partly finished object (1) . 7/05977 PCΪ7DK95/00326

18

4. Method according to claim 3, c h a r a c t e r¬ i z e d by the use of a divisible die, of which one part in an upwardly facing shaping surface comprises at least one recess or projection, with which correspondingly at least one projection or at least one recess, respec¬ tively, is formed in a downwardly facing surface on a part of the object having increased thickness, all in such a manner, that the gravity-dependent engagement between the recess or recesses and the projection or projections is sufficient to retain the object or work¬ piece in abutment against said one die part during the continued process of εhaping, but inεufficient to prevent the workpiece or object being removed by means of suitably adapted ejecting means after the termination of the sha- ping process.

5. Method according to any one or any of the claims 1- 4, c h a r a c t e r i z e d in that the procesε is carried out in stageε.

6. Method according to claim 5, c h a r a c t e r¬ i z e d in that the workpiece or object is cooled between at least two successive processing stages.

7. Machine for carrying out the method according to any one or any of the claims 1-6 and of the kind compri¬ sing tools (13,14) for carrying out a cold-shaping procesε of the ends of elongate blanks (2') so aε to form end partε with a greater diameter than the remainder of the blankε (2'), e.g. in the form of a head (3) and a foot (4), c h a r a c t e r i z e d by εuch an arrangement that the elongated blanks (2') at both ends are acted upon simultaneously by cold-shaping tools (13,14) while the blanks (2') are guided in the longitudinal direction by suitably adapted dies (31) .

8. Machine according to claim 7, c h a r a c t e r¬ i z e d by such an arrangement that the procesε is con- trolled in such a manner, that the two ends of the blank are acted upon with forces of substantially equal mag¬ nitude.

9. Machine according to claim 7 or 8 , c h a r a c- t e r i z e d by a) die carriers in the form of al) a firεt and substantially rotationally symmetrical die carrier (9) adapted to be rotated about its own axis and with equal angular intervals carries a number of first die halves (31) , and a2) a second and substantially rotationally symmetrical die carrier (10) freely rotatable about its own axis and with equal angular intervals carries a greater number of second die halveε adapted to co- operate with εaid first die halves (31) to form dies with through-going openings extending parallel to said axis and having widened partε for the end partε (3,4) with increaεed diameter of εaid objectε, as well as b) cold-εhaping means in the form of bl) a first (11) and a second (12) rotor adapted to be driven mutually εynchronously in mutually opposite direction about axes extending at angles of prefer¬ ably 90° with the axes of rotation for the die car- riers (9,10), said two rotors (11,12) being placed with one on each side of, e.g. above and below, reεpectively, the die carriers (9,10), and b2) cold-εhaping toolε (13,14) distributed about the periphery of the rotors (11,12) with equal angular intervals and having their working surfaces facing generally radially outwardly, and c) means for controlling the rotational movement of said first die carrier (9) in dependence of the rotational movement of the rotors (11,12) for achiev¬ ing the desired movements of the blanks or workpieces placed in the dies relative to the cold-shaping tools (13,14).

10. Machine according to claim 9, c h a r a c t e r¬ i z e d in that the number of dies in said first die carrier (9) differs from a whole multiple of the number of cold-shaping tools in each of the rotors (11,12).

11. Machine according to claim 9 or 10, c h a r a c¬ t e r i z e d in that the second die carrier (10) is in the form of a ring surrounding said firεt die carrier (9) and having an inner diameter at leaεt εo much larger than the outer diameter of the first die carrier (9) that the distance between the two die carriers at the point lying diametrically oppoεite the place, at which their reεpective dieε halves co-operate, is sufficient to allow the passage of an end part (3,4) on a finished object (1) .

12. Machine according to claim 11, c h a r a c t e r¬ i z e d by an ejecting means (29) placed in the inter¬ space between the first (9) and the second (10) die car¬ rier in εuch a manner, that it doeε not engage the head (3) or the foot (4) of the object (1), until the part concerned (3 or 4) has attained its final size.