Forging machine with stroke adjustment means

A forging machine has a machine frame (1), radial forging rams (2) each adapted to carry a die (5), distributed angularly in a common working plane around the system axis (5); radial pressure-fluid piston (12) and cylinder (11) units on the machine frame, each with its cylinder forming or connected to a respective ram and having a stroke corresponding to the required ram stroke; and crossheads (15) mounted adjustably on the machine frame and each supporting the piston of a respective piston and cylinder unit. The stroke position of each ram is adjustable by adjustment of the crosshead towards and away from the system axis. A flange (19) is provided on each cylinder (11) and, a ring (17) extends around each ram, at the radially inner side of the flange (19), and is connected to the adjustable crosshead. Ram return piston and cylinder units (20,22) are disposed between the ring and flange.

BACKGROUND OF THE INVENTION 
This invention relates to forging machines and more particularly to such 
machines having an adjustable stroke. 
For the forging of workpieces having a distinct longitudinal axis, forging 
machines are employed which are provided with three or more rams equipped 
with dies, and distributed within a plane, and in particular with four 
such rams at 90.degree. to one another in an X arrangement. These rams act 
radially on the workpiece which is guided longitudinally along the system 
axis. The rams are guided in the machine frame and are constructed at 
their ends remote from the dies as cylinders of piston-and-cylinder units, 
or are connected to such units. The piston-and-cylinder units are 
dimensioned in accordance with the working stroke of the ram in order to 
minimize the compression volume, this being a major prerequisite for rapid 
stroke and a defined stroke end position. The stroking position, by which 
the pass contour produced by the dies is determined, is adjustable by 
means of crossheads which support the pistons of the piston-and-cylinder 
units and which are adjustable in the machine frame. A closed pass 
contour, as is necessary for certain types of work, is obtained through 
the use of replaceable sets of dies of the appropriate dimensions as in 
Peter Metzger, "Die numerisch gesteuerte Radial-Umformmaschine und ihr 
Einsatz im Rahmen einer flexiblen Fertigung" ["The numerically controlled 
radial forming machine and its employment in flexible manufacturing"], 
volume 5 of the reports issued by the Institut fur Umformtechnik 
[Institute of Forming Technology] of the University of Stuttgart, 
publishers: Springer-Verlag, Berlin - Heidelberg - New York, 1980, pages 
36-39, 67-69, 112, 113, 129), or by means of dies which are transversely 
adjustable at the rams via die holders, said dies featuring mutually 
overlapping work and side surfaces and being adjusted such that they form 
a closed pass contour in the relevant stroke end position (European 
Application No. EP 0 228 030 B1; U.S. Pat. Nos. 4,796,456 and 4,831,864). 
In order to achieve a compact design of such forging machines and, at the 
same time, minimum-clearance ram guidance, the rams according to European 
Application No. EP 0 228 658 B1 are constructed as pistons or cylinders of 
piston-and-cylinder units and directly guided, i.e. not offset, in the 
machine frame. Here -- if double-acting pistons are to be avoided owing to 
the more complicated seals required -- the pistons or cylinders serving as 
rams have to be provided with shafts which pass through the complementary 
cylinders or pistons, and the supporting crossheads which are adjustable 
in the machine frame, by means of which shafts the piston-and-cylinder 
units for the ram return strokes operate. 
SUMMARY OF THE INVENTION 
The object of the invention is to avoid not only double-acting pistons but 
also ram return strokes effected via shafts. This object is achieved in 
that, on the basis of rams constructed as cylinders or connected to 
cylinders, according to the invention the rams, or the cylinders connected 
to them, are in each case provided with, or connected to, a flange and 
surrounded in each case by a ring engaging behind the flange, the ring and 
the crosshead provided for stroke position adjustment being 
interconnected, and piston-and-cylinder units for the return stroke of the 
rams are arranged between each ring and the associated flange. 
In order to further improve accessibility to the seals of the main and 
return pistons, provision is made, in accordance with a further feature of 
the invention, for detachable connections to be provided between the rings 
and the associated crossheads, and for sufficient removability of the ring 
concerned, with the cylinder or ram surrounded by it, from the associated 
crosshead with the plunger piston which it supports, such that the seal 
between the plunger piston and cylinder can be replaced without any 
further dismantling and re-assembly.

DESCRIPTION OF PREFERRED EMBODIMENTS 
The forging machine depicted in FIG. 1 as viewed in the direction of the 
system axis S comprises a frame 1 which guides four rams 2 in an X 
arrangement, grouping said rams 2 together with their drives so that the 
rams 2 move radially to the system axis S in a working plane perpendicular 
thereto. The frame 1 is provided on both sides front and rear with 
extensions 3 by means of which it is supported on piers 4 of a foundation. 
Each ram 2 is provided at its end face with a die 5, and in the stroke end 
positions of the rams 2, the dies 5 form a closed pass contour. In order 
to be able to form pass contours of which the side lengths are smaller 
than the width of the dies 5, the dies 5 are supported by holders 6 which 
are adjustable transverse to the axes of the rams 2 in the working plane, 
and the stroke end positions of the rams 2 are adjustable so that the dies 
form a closed pass contour in their respective stroke end positions in the 
manner known from EP 0 228 030 B1 with the portion of their work surface 
exceeding the pass size lying adjacent a side surface of an adjacent die. 
Another possibility of achieving a closed pass contour, at least in certain 
areas, and of preventing die collision, consists in that, during 
performance of the work, a continuous collision monitoring function is 
implemented, and in that, by means of a die change system associated with 
the forging machine, rapid die changing is performed as soon as the 
dimensions of a die set are no longer reconcilable with the workpiece size 
to be formed, because either there is a danger of the dies colliding, or 
the dies no longer sufficiently enclose a pass contour, in the manner 
known from the publication mentioned above (Peter Metzger, "Die numerisch 
gesteuerte Radial-Umformmaschine und ihr Einsatz im Rahmen einer flexiblen 
Fertigung"). The invention includes an embodiment which is devised for a 
die change operation instead of a transverse displacement of the dies. 
In larger-scale details, FIGS. 2 to 7 show a single ram 2 which is guided 
axially movably by a guide bushing 7 and -- as depicted in FIG. 7 -- by 
guide plates 8 which bear against the flats 9 of the ram 2, said guide 
plates 8 interacting with the flats 9 to prevent the ram 2 from rotating. 
At its end remote from the system axis S, the ram 2 has a stepped bore 10 
forming a cylinder 11 which receives a plunger piston 12. A ring seal 13 
is inserted at a shoulder of the bore 10 to provide a seal against the 
plunger piston 12, and is held in this position by a ring 14. The plunger 
piston 12 is supported on a crosshead 15, the distance of which from the 
frame 1 is adjustable, thus enabling the stroke position of the cylinder 
11, and therefore that of the ram 2, to be varied, while the plunger 
piston 12 and cylinder 11 are sized solely in accordance with the working 
stroke of the ram 2. The stroke position defines, as a result of the 
respective end position of the ram 2 with its die 5, the resultant 
workpiece dimension. The crosshead 15 is connected by tie rods 16 to a 
ring 17, of which the distance of which from the crosshead 15 is 
determined by spacer sleeves 18. The ring 17 surrounds the ram 2/cylinder 
11 and engages behind a flange 19 at the cylinder 11. The ring 17 is 
further provided with bores 20 which are closed at one end by covers 21 
and which form cylinders for receiving plunger pistons 22. These plunger 
pistons 22 act against the flange 19 at the ram 2/cylinder 11 for the 
return strokes thereof. 
For replacing the ring seal 13, the ring 17 is detachably connected to the 
crosshead 15, for which purpose the nuts 23 are removed from the tie rods 
16. This operation is facilitated by the fact that the tie rods 16 can be 
hydraulically preloaded by pistons 25, these being actuated in cylinders 
24 and connected to the tie rods 16, so that, with the tie rods 16 
preloaded, counter nuts 26 of nuts 23 can be turned without stress. 
Pressurization of the pistons 25 associated with a ram 2 is performed 
centrally in a common system for all pistons 25. Once the ring 17 has been 
separated from the crosshead 15, the cylinder 11 and the plunger piston 12 
can also be detached from one another, as depicted in FIG. 6. 
The stroke position of a ram 2 can be adjusted by virtue of the 
above-mentioned adjustability of the associated crosshead 15. For this 
purpose, as can be seen from FIG. 7, each crosshead 15 is connected by 
four tie-bars 27 to the frame 1, through nuts 28 which are rotatably 
supported in the crosshead 15, which brace the crosshead 15 against the 
press force exerted at the plunger piston 12, and which can rotate on the 
threaded rods 29 of the tie-bars 27. The threaded nuts 28 are provided 
with external toothing 30 and are rotated in unison for each crosshead 15 
by a ring gear 31, which in turn is rotated by geared motors 32, the drive 
pinion 33 of each of which engages in the internal toothing of the 
double-toothed ring gear 31. The stroke position of each ram 2 is thus 
adjustable and can be locked by means of a brake device in the gear motors 
32. The tie-bars 27 are secured by means of shafts 34 and nuts 35 to the 
frame 1. The units formed from the cylinders 36 connected to the frame 1 
and the pistons 37 connected to the crosshead 15 serve to preload the 
crosshead 15 in the direction of the working pressure against backlash of 
the nuts 28 on the threaded rods 29. 
As is particularly apparent from FIG. 5, the die 5 associated with each ram 
2 is connected to the ram 2 by a clamping device which facilitates a 
transverse displacement or a change Of die 5 within a short time and 
without lengthy interruptions to work. The ram 2, which is provided at its 
end face supporting the die 5 with a head plate 40, is also provided at 
the same end face for die displacement or change, with a bore 41 into 
which a cylinder 42 with cover 43 is inserted. A plunger piston 44 is 
inserted in the cylinder 42, said plunger piston 44 having a hollow which 
receives one end of a tension pin 46 provided with a collar 45, and, 
between the collar 45 and the cover 43, an assembly of cup springs 47. The 
tension pin 46 passes through the head plate 40 and a clamping element 48 
located in a groove of the head plate 40, on which clamping element 48 a 
collar nut 49 associated with the tension pin 46 acts. The clamping 
element 48 is connected to a holder 50 which supports the die 5. 
Pressurization of plunger piston 44 causes the assembly of cup springs 47 
to be compressed, the clamping element 48 to be unloaded and the holder 50 
to be pushed away from the head plate 40. The holder 50 with the die 5 can 
now be transversely displaced or replaced by another holder 50 with die 5 
by a die change system. Once the die 5 has been moved to its new position 
or replaced by a die of different dimension, the plunger piston is 
depressurized again and the assembly of cup springs 47 clamps the holder 
50 and die 5 once more against the head plate 40 at the ram 2. 
For the purpose of transversely displacing the dies 5 in the illustrated 
embodiment, each head plate 40 of a ram 2 is provided with a longitudinal 
groove 51 for receiving the clamping element 48, and each clamping element 
is in turn provided with a longitudinal groove 52 for receiving the 
tension pin 46 with its collar nut 49, with the longitudinal extension of 
the grooves 51 and 52 running in the working plane common to the rams 2. 
Parallel to the grooves 51 and 52, the head plate 40 is provided with 
lateral strips 53, and the holder 50 is provided with lateral strips 54, 
which strips are provided with fine serrations facing one another. The 
lateral strips 54 are provided with toothing 55 in which pinions 56 engage 
which in turn mesh with pinions 57 on shafts 58. A pinion 56, a pinion 57 
and a shaft 58 are respectively supported in a gearbox 60 which is 
connected to the ram 2. Each shaft 58 is provided with a splined end 59 by 
means of which it engages in a hollow shaft 61 having a splined bore so 
that the shaft 58 is rotationally coupled thereto yet axially 
displaceable. Each hollow shaft 61 is driven by an oscillating motor 62 of 
which one output shaft end 63 engages in the hollow shaft 61 while a 
second output shaft end actuates a rotary transmitter 64 which indicates 
and/or controls the lateral displacement of the holder 50 with die 5.