Indirect extrusion press

An indirect extrusion press including a press frame body of the Rahmen structure. The press frame body is formed of a press platen and a main cylinder frame, which are rigidly connected together. Movably disposed between the press platen and main cylinder frame is a container adapted to retain a billet therein. A die stem fixedly extends toward the container from the platen while a pressing stem slidably extends toward the container from the main cylinder frame. Hydraulic cylinders are provided with the platen to shift the container back and forth along the longitudinal center line of the press. Hydraulic coupling cylinders are also provided with a crosshead from which the pressing stem extends and the pistons of both cylinders are connected to their respective container holders. The relative position of the container and pressing stem is maintained constant during an extrusion stroke so that the container-shifting force is added to an extrusion force. An effective scalping operation of the container is performed by using not only the container-shifting cylinders but also the coupling cylinders. An intermediate frame may also be slidably provided on the die stem such that the shifting force for the intermediate frame may also be added to the extrusion force or scalping force. The extra extrusion force is received by the container and its related moving members, thereby enabling use of the press frame body without reinforcement and allowing a reduction in the total number of parts and weight necessary, and simplification of the press.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an indirect extrusion press, and more 
particularly, to an improved indirect extrusion press equipped with a 
hydraulic coupling device and capable of adding the container-shifting 
force to the extrusion force. 
2. Description of the Prior Art 
In a conventional indirect extrusion press illustrated in FIG. 1, a press 
platen 51 defining a through bore 51A and a main cylinder frame 52 are 
spacedly and oppositely disposed along the longitudinal center line of the 
press in the front and back positions respectively, and are rigidly 
connected together by means of tie rods 53 arranged in "X" patterns so as 
to form the press frame body into a Rahmen structure. 
A main ram 55 is slidably received in a main cylinder 54 fixedly secured on 
the main cylinder frame 52. An extrusion force generating unit is 
constituted by the main ram 55, crosshead 56, pressing stem 71, etc. 
Crosshead 56 and main ram 55 are arranged in such a manner that they may 
be shifted forward namely, toward press platen 51) under no load by means 
of side cylinder devices, each of which devices includes a side cylinder 
57 and piston 58. On the other hand, a die stem 74 of a cylindrical 
configuration is fixed on the press platen 51 along the longitudinal 
center line of the press, to which die stem 74 is mounted a die 73 via a 
die holder 72. 
A container 70 can be freely shifted back and forth along the longitudinal 
center line of the press, namely, along the pressing direction by means of 
container-shifting cylinder devices, each of which is formed of a cylinder 
61 and piston 62. The relative position of container 70 and pressing stem 
71 can be fixed by means of hydraulic coupling devices, each of which is 
formed of a cylinder 59 and piston 60. Therefore, each of 
container-shifting cylinders 61 is attached to main cylinder frame 52 
while each of hydraulic coupling cylinders 59 is secured to crosshead 56 
and is slidably fitted through main cylinder frame 52. Furthermore, the 
pistons 60, 62, which are slidably received in their respective cylinders 
59, 61, are coupled at their rearmost ends with a rear frame 76 provided 
integrally with the main cylinder 54 on the periphery of the latter. The 
rear frame 76 can axially be movable independently from main cylinder 54 
insofar as a large ring-like bore is provided in the center of rear frame 
76. Rear frame 76 and container holders 69 are mutually connected by means 
of tie rods 77. 
In addition the above-described members or devices, numeral 63 indicates an 
intermediate frame which is freely shiftable by means of a hydraulic 
cylinder device including a cylinder 64 and piston 65. Intermediate frame 
63 is fitted over die stem 74 through a guide block 75, etc. Intermediate 
frame 63 is equipped with a vertical shear device which includes a 
hydraulic cylinder 66 and piston 67. A shearing edge 68 is adapted to 
sever off a discard from an extruded article. 
In the conventional indirect extrusion press shown in FIG. 1, a billet 
loaded in container 70 may be indirectly extruded through die 73 by 
shifting container 70 in such a manner that the container slides over die 
stem 74 while fixing the relative position of container 70 and pressing 
stem 71. Although the above-noted conventional press is constructed in 
such a manner that the container-shifting force may be added to the 
extrusion force of main cylinder 54 during each extrusion stroke, it is 
accompanied by following drawbacks. 
Namely, the overall pressing force to be generated during an extrusion 
stroke is a combination of forces exerted on main cylinder 54 and side 
cylinders 57 as well as a force applied onto the container unit. In order 
to make the press capable of withstanding the overall pressing force, it 
is indispensable to make each constituent parts of the main structure, 
which is formed by pressing platen 51, main cylinder frame 52 and tie rods 
53 connecting said platen 51 and frame 52 together into the Rahmen 
structure, more durable by a degree at least equivalent to the shifting 
force of the container unit. This certainly results in an increase in its 
number of constituent parts a complication of its structure and an 
increase in its weight. 
The inventors of this invention have heretofore made a number of 
inventions, including, for example, copending U.S. patent application Ser. 
No. 199,626 filed Oct. 22, 1980, U.S. Pat. Nos. 4,251,202 and 4,230,661 
and copending U.S. patent application Ser. No. 946,330 filed Sept. 27, 
1978, all of which relate to an extrusion press or extrusion process. 
SUMMARY OF THE INVENTION 
An object of this invention is to solve the drawbacks of the 
above-described prior art press. 
Another object of this invention is to provide an indirect extrusion press 
of a Rahmen structure and with extremely high movement accuracy. 
A still further object of this invention is to provide an indirect 
extrusion press capable of increasing its effective extrusion force by 
adding the container-shifting force to the extrusion force. 
An additional object of this invention is to provide an indirect extrusion 
press which contemplates simplification of the structure and mechanism, 
and reduction in both total number of parts and overall press weight. 
A still further object of this invention is to provide an indirect 
extrusion press which permits effective container scraping work. 
In order to achieve the above objects, the present invention provides in 
one aspect in indirect extrusion press in which a press platen and main 
cylinder frame are disposed oppositely, i.e., in the front and back 
positions, respectively, and connected together by means of a plurality of 
tie rods into a press frame body of a Rahmen structure a die stem is fixed 
on the press platen along the longitudinal center line of the press, and a 
container and pressing stem are shifted so that a billet loaded in the 
container can be indirectly extruded through a die attached to a die stem, 
the press characterized by the fact that the platen is provided with a 
plurality of hydraulic cylinders adapted to shift the container, a 
crosshead is provided with a plurality of hydraulic coupling cylinders, 
the pistons of the container shifting cylinders and coupling cylinders are 
coupled with container holders so that a container unit is formed, the 
relative position of the container and pressing stem is fixed during each 
extrusion stroke, and the container-shifting force is added to the 
extrusion force via the pressing stem.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring first to FIGS. 2 through 6, a preferred embodiment of the present 
invention will be described hereinbelow in detail. While the embodiment is 
a single-acting indirect extrusion press equipped with an intermediate 
frame, this invention may also be applied to any indirect extrusion 
presses other than those equipped with such intermediate frame. It may 
equally be applied to double-acting indirect extrusion presses. 
In FIG. 2 where the single-acting indirect extrusion press equipped with an 
intermediate frame is in its initial position, a press platen 1 defining a 
through bore 1A along the longitudinal center line of the press and a main 
cylinder frame 2 are spaced apart and oppositely disposed in front and 
back positions, respectively. Platen 1 and frame 2 are firmly connected to 
each other by means of tie rods 3 which extend in "X" patterns along each 
of the top, bottom, and both sides of the press, thereby forming a press 
frame body of a Rahmen structure as indicated by the letter "A" in FIG. 2. 
A main cylinder 4 is fixed on main cylinder frame 2 along the longitudinal 
center line of the press, and slidably receives a main ram 5 to form an 
extrusion force generating unit. Main ram 5 is provided through a 
crosshead 6 with a pressing stem 21, which extends forward along the 
center line of the press (here, the term "forward" means the pressing 
direction while its opposite direction is expressed by the term 
"backward"). 
Main cylinder frame 2 is equipped with side cylinders 7. A piston 8, which 
is slidably fitted in each side cylinder 7, is coupled with crosshead 6 so 
as to enable pressing stem 21 to move forward without any load. 
On the back end face of press platen 1, is provided a die stem supporting 
device 31 through which the front end, i.e., base portion of die stem 24 
is fixedly secured along the center line of the press. Needless to say, 
die stem 24 is detachable and may be taken out of the press if necessary. 
Die stem 24 is of an elongated cylindrical body. Die 23 is attached at the 
rear extremity thereof via a die holder 22. 
A container 20 has a billet 27 received along the center line of the press 
and is held in place by means of container holders 19 which in turn are 
coupled in a cooperative manner with container shifting devices and 
hydraulic coupling devices, thus constituting a container unit as 
indicated by the letter "B" in FIG. 2. Thus, in the interior of the press 
frame body A, four container-shifting cylinders 11 are disposed and fixed 
on press platen 1 at the diagonally-opposed four corners of platen 1. 
Pistons 12, which are slidably received in their respective cylinders 11, 
are connected to container holders 19, respectively. On the other hand, 
hydraulic coupling cylinders 9 are fixedly secured with crosshead 6 in a 
diagonal arrangement. The corresponding pistons 10 are coupled with 
corresponding container holders 19. 
An intermediate frame 13 is fitted over die stem 24 via a guide ring 25 and 
etc. and is movable back and forth along the longitudinal direction of die 
stem 24 by means of pistons 15 slidably received in their respective 
cylinders 14 which are secured to press platen 1. Intermediate frame 13 
includes a vertical shearing device including a cylinder 16, piston 17, 
shear 18, etc. Movable members such as crosshead 6 and container holders 
19 are slidingly guided by means of guide members (not shown). 
An extrusion operation is now described referring to FIGS. 3 to 6 wherein 
FIG. 3 illustrates a billet 27 being charged into the receiving hole of 
container 20 by means of a billet loader 26 while shifting container 20 
forward. In other words, extrusion operation may be started after charging 
billet 27 into container 20 by a suitable mechanism. 
Subsequent to placing billet 27 in container 20, billet loader 26 is swung 
out of the press. Then, working oil is supplied to the rear chamber of 
each side cylinder 7 to shift main ram 5 forward under no load, thereby 
holding billet 27 between the front face of pressing stem 21 and die 23 
with a dummy block or pressing disc 29 interposed between the front face 
and billet 27, now ready for extrusion. 
Then, working oil is fed to the rear chamber of each side cylinder 7 as 
well as to main cylinder 4 so that main ram 5 resumes its advance. This 
upsets billet 27 into container 20, thereby filling up container 20 with 
billet 27 and generating a friction force between container 20 and billet 
27. Thereafter, working oil is supplied to the rear chamber of each 
container-shifting cylinder 11, the back chamber of each side cylinder 7 
and main cylinder 4, resulting in a simultaneous advance of container 20 
and pressing stem 21. Thus, billet 27 is extruded through die 23 provided 
with die stem 24 while maintaining a state in which any relative movement 
of container 20 is restrained with respect to main ram 5. 
Here, by adjusting the delivery rate of each pump so as to make the moving 
speed of the piston of each container-shifting cylinder 11 equal to or 
faster than that of main ram 5, the shifting force of container 20 can be 
combined with the extrusion force through billet 27 because the oil within 
the hydraulic coupling 9 is entrapped. Furthermore, container 20 can be 
synchronized in motion with stem 21 by virtue of the friction force 
between billet 27 and container so long as the friction force is larger 
than the container shifting force 20. 
On the other hand, where working oil is supplied to the forward portion of 
each hydraulic coupling cylinder 9, the container-shifting force is added 
to the main ram-shifting force, i.e., extrusion force via pressing stem 21 
since cylinder 9 is secured to crosshead 6 and its piston 10 is coupled 
with its respective container holder 19. In FIG. 4, working oil is charged 
into each of ports a, b and c. 
Here, the pressure increment timing of each hydraulic coupling cylinder 9 
becomes important for intercoupling main ram 5 and container 20 at a 
desired position in accordance with the length of billet 27 by making use 
of friction force between the container 20 and billet 27. 
The above pressure increment timing may be at any time after the friction 
force between container 20 and billet 27 becomes, subsequent to the 
upsetting step of the billet, greater than the pressing force of each of 
coupling cylinders 9 and container-shifting cylinders 11 but immediately 
before the friction force becomes smaller than the pressing force due to a 
decrease in length of billet 27. After supplying working oil to each 
coupling cylinder 9 and locking the relative position of container 20 and 
die stem 24 (or crosshead 6), the container-shifting force is added to the 
extrusion force during the entire extrusion stroke through hydraulic 
coupling cylinders 9, while maintaining the relative position of container 
20 and die stem 24 (or crosshead 6). The relative position of container 20 
and crosshead 6 is fixed as long as they are coupled under pressure, 
thereby forming the Rahmen structure "C" as shown in FIG. 4 and further 
improving the accuracy of movement. 
In the above-noted extrusion stroke, the extrusion force generated by main 
cylinder 4 and side cylinders 7 is added with the container-shifting 
force. The above extrusion force is received by the Rahmen structure of 
press frame body A while the extrusion force of container-shifting 
cylinders 11 is received by the container unit B. Accordingly, an article 
28 can be extrusion-formed by the combined greater pressing force without 
need for reinforcing press frame body A. 
After completion of the extrusion stroke, the receiving hole of container 
20 is subjected to scraping or cleaning as shown in FIG. 5 when container 
20 is retracted backward. Then, as shown in FIG. 6, a discard 30 and 
extruded article 28 are severed off by means of a suitable shearing device 
and each movable member is returned to its original position, resulting in 
completion of the pressing cycle. 
The container-scraping stroke is now described in further detail referring 
to FIG. 7. Upon the completion of the extrusion stroke, the piston rod 12 
of each container-shifting cylinder 11 is extended backward to shift 
container 20 in the direction shown by an arrow. During this backward 
movement of container 20, the inner wall of the through bore of container 
20 is cleaned up, in other words, scraped together with discard 30 by the 
dummy block or pressing disc 29 which has very little clearance with the 
inner wall. Here, the load occurring for removal of the resultant shell 
from the inner wall of the container 20 is not constant during the 
scraping stroke but tends to change considerably. To avoid the so-called 
stick-slip phenomenon, a brake circuit 33 is provided. 
As described above, the force required for the scraping work of container 
20 varies considerably depending on the thickness of discard 30, the 
material of the billet, the diameter of the through bore of container 20, 
the temperature of billet 27, etc. In some instances, the shifting force 
P.sub.1 of each of container-shifting cylinders 11, 12 becomes 
insufficient to perform the scraping operation. If this occurs, working 
oil is supplied to hydraulic coupling cylinders 9 in such a fashion that 
the pistons of these cylinders are retracted. In the illustrated 
embodiment, an additional pulling forces P.sub.2 is applied to container 
20 by each of hydraulic coupling cylinders 9 to shift container 20 toward 
the main ram 5. 
If addition of the pulling forces by hydraulic coupling cylinders 9 is 
proven to still be insufficient to conduct scraping operation and the 
press is provided with an intermediate frame, piston 15 of each cylinder 
14 may be extended backward and, in the illustrated embodiment, a force 
P.sub.3 combined with the container-shifting power via spacer blocks 32. 
Here, the combined force P.sub.1 +P.sub.3 is backed up by the pressure 
Pb.sub.1 of the working oil in main cylinder 4 while the force P.sub.2 is 
backed up by the reaction force Pb.sub.2 occurred at crosshead 6. Brake 
circuits 33, 34, 35 are each adapted to avoid so-called stick-slip 
phenomenon. In the illustrated embodiment, brake circuits 33, 34, 35 are 
provided separately with their respective cylinders 9, 11, 15. However, 
more than one cylinder may be connected to a common brake circuit. 
As described above, pressing platen 1 and main cylinder frame 2 are 
spacedly and oppositely arranged in the front and back positions and 
connected together by means of a plurality of tie rods 3 into a press 
frame body A of the Rahmen structure. Die stem 24 is fixedly disposed on 
pressing platen 1 along the center line of the press. Container 20 loaded 
with the billet 27 and pressing stem 21 are shifted so as to indirectly 
extrude the billet 27 through the die 23 attached to die stem 24. 
According to this invention, platen 1 is provided with a plurality of 
hydraulic cylinders 11 for shifting container 20 while a plurality of 
hydraulic coupling cylinders 9 are secured with crosshead 6. Piston 12, 10 
of container-shifting cylinders 11 and coupling cylinders 9 are coupled 
with container holders 19, thus constituting container unit B. The 
relative position of container 20 and pressing stem 21 is fixed during an 
extrusion stroke so that the container shifting force is added to the 
extrusion force via pressing stem 21. This arrangement can bring about the 
following advantages: 
The connection between container 20 and pressing stem 21 or container 
holders 19 and crosshead 6 can be performed at a desired relative position 
in accordance with the length of billet 27. The container-shifting force 
can be added to the extrusion force, resulting in an increase of the 
effective extrusion force. In addition, a Rahmen structure is formed by 
crosshead 6 and container holders 19 as shown in FIG. 4 while the 
crosshead 6 and container holders 19 are coupled together. The 
container-shifting cylinders 11, hydraulic coupling cylinders 9 and 
container 20 are arranged in a cooperative manner to constitute the 
container unit B to enhance the movement accuracy which is most important 
for indirect extrusion. Therefore, the main structure, namely, press frame 
body A may be formed without need for taking the force of 
container-shifting cylinders 11 into consideration, resulting in such 
advantages that the structure and mechanism of the press can be 
simplified, the total numbers of parts may be reduced and the press may be 
reduced in weight. 
Obviously, many modifications and variations of the present invention are 
possible in light of the above teaching. It is therefore to be understood 
that within the scope of the appended claims the invention may be 
practiced otherwise than as specifically described herein.