US3043425A - Extrusion press and control therefor - Google Patents

Description

July 10, 1962 A. GROHMANN ETAL ExTRusIoN PRESS AND CONTROL. THEREFOR Filed Deo.

m m h (WW ew r w M w 2 E an P V N6 y 3 w Y w w W y M Y A H P v ,U mi, l i M Y nite The present invention relates generally to improvements in and relating to hydraulic press structures and controls thereof and concerns, in particular, an extrusion press for processing metal, wherein a piston is suddenly driven forward under the action of pressurized tluid from pressurized storage means.

More specifically, the invention relates to hydraulic press structures for the production of a desired sudden ram movement from a work stroke position relative to a metal block or like workpiece to be extruded.

In prior art presses a quick release of the ram stroke is obtained by the sudden removal of excess fluid pressure on the pistons of an intensier. These pistons are subjected to the pressure of a compressed gas in a direction opposite to the Work-stroke direction and produce, by means of transmission pistons connected with them, the fluid pressure in the main press cylinder.

There is known a hydraulic metal extrusion press wherein a press piston under uid pressure from a hydraulic storage tank and operatively connected with a tool, is suddenly driven forward from a desired work-stroke position while maintaining the fluid pressure, the piston being in rigid connection with piston areas in which a uid pressure opposed to the work-stroke direction is exerted, the iluid pressure opposed to the work-stroke direction acting in opposition to the pressure on the press piston until a desired work-stroke position is reached, and being then instantly removable by means of a control valve.

Such extrusion presses, where the ram is intended to suddenly strike the metal block to be extruded and the block is then pressed further under great ram speed, have proven to be suitable especially for the pressing of metals in cold state.

The problem in such presses is iirst to adjust the ram to a position at relatively small distance from the metal block and then to strike the metal with the ram, in order to subsequently extrude the Ymetal block at great speed. In the prior art presses, the problem is solved in that a somewhat greater reaction force is built up under the tank pressure, and in opposition to the main ram, by means of holding pistons specially provided for that purpose.

This force is suddenly removed to produce the workstroke. This construction necessitates the equipping of such presses with additional hea-vy pistons and cylinders, which make the press extremely heavy and the manufacturing costs are relatively high.

It is an object of the present invention to provide means conducive to avoidance of additional holding pistons, so as to construct a press suitable for the described process which is considerably lighter in weight and less expensive than the prior presses.

It is another object of the present invention to provide means effectuating the ram work-stroke, not by two pressure receiving chambers as in the prior art to produce a pressure equilibrium in the starting position of the ram, but to arrange for the required release of the work-stroke by means of only one pressure receiving chamber to thereby achieve propulsion of the ram.

The construction is such that the hydraulic pressure is admitted to the main press piston via a valve and connects with a retraction plunger which functions merely for the exertion of the retraction pressure. The main plunger is Patented July 10,v 1962 u so constructed that during the duration of the pressure stroke it produces the required work pressing force to overcome the constant pressure in the retraction cylinder.

Pursuant to the invention the main press piston is advanced iirst under pressure from an air vessel to a desired starting position. To produ-:e the work-stroke, an inlet valve of relatively large dimensions, is opened whereby the main plunger is connected with fluid or water storage pressure means. Previously, during the advance of the press piston to the desired stroke position, the outlet valve of the retraction cylinder is opened and closedl again when the desired stroke position is reached. Pursuant to the invention a check valve normally closed by the water pressure, is installed in the retraction cylinder and opens when the pressure builds up during the pressing stroke in the retraction cylinder becomes greater than the oppositely directed pressure of the accumulator. This check Valve provides the advantage that during the pressure stroke the press plunger is relieved from the increased pressure built up in the retraction cylinder, while on the other hand the closing pressure of the check valve is so great that, as the ram moves into starting position, the opposition pressure required for holding this position can be maintained in the retraction cylinder without escaping.

These and other objects of the invention will become further apparent from the following detailed description, reference being made to the accompanying drawing which illustrates the best mode presently contemplated for carrying out the invention:

FIG. 1 is a diagrammatic representation of a press, pursuant to the invention. in retracted position;

FIG. 2 is view similar to FIG. 1, with the press being shown in the starting position for the work stroke;

FIG. 3 is a View similar to FIG. 1 with the press being shown during the Work stroke.

Referring now to the drawing in detail, there is shown a metal block 1 which is to be extruded. The block is disposed within the receptacle or holder of the press generally indicated at 30.

The press is provided with a body or frame 3 in which the work holder 2 is mounted. The latter has a chamber 2c in which the workpiece 1 is disposed and which is adapted to receive the ram 4a projecting from one end of the press piston 4, the other end of which mounts a retraction piston 5. The pistons 4 5 and ram 4a are shown in full retracted position in FIG. l. Piston 5 operates within a hydraulic pressure chamber or cylinder 7 which is in fluid flow communication with a water or uid storage tank 10 by means of a conduit 9 and check valve 6, which is spring-loaded.

A combined conduit 11 which serves during operation of the device as both an inlet and an outlet conduit is connected to a port 31 of the retraction cylinder portion 7 at a location adjacent the intermediate cylinder portion 8. The conduit 11 extends from the port 31 to an internal passage or channel 32 of a valve assembly housing generally designated 33. The internal passage 32 communicates through a valve 13 and another internal passage 40 to an external conduit 23 leading to the fluid storage tank 10. The fluid storage tank 10 contains a fluid under pressure, such as Water. The valve 13 forms one valve portion of a combined inlet and outlet valve generally designated 42 having another portion 12 whichy truded throu'gh the die 2a to form the extruded portion 1a. To eiect movement of the piston from the operating position indicated in FIG. 3 to the retracted position in FIG. 1, the combined valve 42 is displaced to cause the portion 13 to open the communication between the conduit 23 and the internal passage 32 which in turn communicates with the conduit 11 (FIG. 1). At the same time, the valve 12 is moved to close the communication between the passage 32 and the drain A. As indicated in the drawings, this causes iluid pressure to be directed through the port 31 into the retracting cylindrical portion 7 to force the retracting piston portion 5 to move backwardly from the position indicated in FIG. 3 to the position indicated in FIG. 1.

An operating housing assembly generally designated 46 is provided with internal compartments and passages in which are operable operating valves 15 and 1S. A conduit 14 connects through a port 34 to an end of the pressure piston cylindrical portion 8 adjacent the end thereof which lies next to the retracting piston cylindrical portion 7. The port 34 connects via conduit 14 to the operating valve housing 46 which includes an internal passage 37 which extends around the operating valve 13 and through a passage indicated in FIG. 1 to be closed by the operating valve 15 and then to a conduit 35 which leads to the uid storage tank 10.

In FIG. 1, the operating valve 15 is closed under its own weight when the pressure of the spring which acts on the piston 22 to move it downwardly.. The lower end of the piston 22 is exposed via conduit 21 to pressure in an internal passage 48 of the control valve housing 33 which may be regulated to be exposed to either the pressure of the'drain (arrow A) or the pressure of the lluid storage tank 10 by a combination valve generally designated 50. The cylinder 8 is made to communicate with the pressure in the uid storage tank 10 when the valve 15 is opened. The cylinder 8 may also be communicated by means of the conduit 14 through an internal passage dened in the operating valve housing with a conduit 17 which connects through an auxiliary fluid pressure source, which, in the embodiment indicated, is a vessel 16 which is filled with a liquid and subject to compressed air pressure. The value of this operating pressure may be regulated in accordance with the operating conditions desired. When the valve 18 is opened, the pressure of the tank 16 communicates through the conduit 17, an internal passage of the operating valve housing and passage 14 through port 34. Valve 18 is opened by the upward movement of piston 24 to cause its connecting rod to lift piston valve 1S olf its seat. Piston 24 is moved upward by pressure from tank 10 communicated to line 11 when valve 13 is open (FIG. l). Valve 18 closes under its own weight when valve 13 is closed and line 11 is opened to drain passage 44 by valve 12.

'In accordance with the invention, the operation of the main valve 15 is effected by the positioning of the combined control valve which includes valve portions 19 and 20 disposed in housing 33 at locations respectively interconnecting the uid storage tank with either the drain line A or a conduit 21 which acts upon the lower face of the piston 22, in accordance with the setting of the valves 19 and 20. When valve 20 is opened and valve 19 is closed, the conduit 21 is exposed to drain pressure A and the spring will force the piston 22 to the lowermost extent of its travel and permit valve to lower. However, when the Valve 50 is moved so that the portion closes off the drain passage connection and the valve 19 is opened to communicate the fluid pressure of the tank 10 to the conduit 21, the piston 22 is displaced upwardly. This eiects opening of the valve 15 by lifting it to effect communication of the fluid pressure of the tank 10 through the conduit 14 and port 34 with the pressure piston portion of the cylinder 8, as shown in FIG. 3 during the extrusion stroke.

When uid is communicated via the conduit to the conduit 14 and the pressure cylinder portion 8, the valve 15 being opened, the relief or check valve 6, which is disposed to close the communication of the conduit 9 uu'th the pressure storage tank 10, is in a closed position under force of spring 6. The check valve 6 is such that it will be maintained in a closed position by a spring 6 `until the pressure in the retracting piston cylinder portion 7 exceeds that of the fluid pressure in the storake tank 10. In this latter instance, liow outwardly lfrom the retracting piston portion 7 will be directed into the iluid storage tank 10 for recovery therein.

The operating valve 18 is operated by the rising of a connecting rod portion of a piston 24 which is subjected to the pressure in the conduit 11. The piston 24 is biased to a lower position by the associated spring 18` indicated cated in FIG. 2. Thereupon valve 13 is closed and valve 12 opened when it is desired to move piston 4 through its working extrusion stroke.

As indicated in each of the drawings, a die 2a is centered at one end `of the ram cylindrical portion or frame 3 in alignment with a workpiece 1 which is centered by a workpiece holder 2. The workpiece is insertable into a chamber 2c formed centrally of the holder 2 when the ram 4a is in its retracted position as indicated in FIG. 1. The ram is retracted by opening the inlet valve 13 and closing the valve portion 12 to admit hydraulic pressure from the tank 10 to the conduit 23 and the conduit 11 to the port 31 to move the retracting piston portion 5 backwardly to the position indicated in FIG. l.

' The extrusion process is initiated by rst bringing the ram 4a into a starting -position as indicated in FIG. 2 wherein the forward free end of the ram is inserted by a small amount into the chamber 2c to be disposed at a distance S from the workpiece 1. This move-ment of the ram from its retracted position indicated in FIG. 1 to the starting position indicated in FIG. 2 is eiected by lluid pressure from the compressed air uid vessel 16. To effect this movement, the inlet valve portion 13 is opened and the outlet valve portion 12 is closed to open valve 18 and admit pressure from tank 16 to cylinder 8 to permit piston. 4 to move to the right of the position indicated in FIG. l. After piston 4 is located at the operating position of FIG. 2, valve 13 is closed and valve .12 opened to start the working stroke. This permits closing of valve 18 under its own weight. Valve 15 ris then opened by exposing piston 22 to pressure from tank 10 by opening valve 19 and closing valve 21). Immediately after the beginning of the forward movement of the main plunger 4 a very high pressure is brought up to the space 7 in front of the piston 5, which exceeds the pressure in the tank 10. To relieve this pressure so as to prevent an opposition to the movement of the ram, check valve 6 opens to permit movement to the iluid to be directed backwardly to the line 9 and tank 10.

After release of the blow stroke of the main ram 4a, the metal block `1 is extruded under high ram velocity `and the extrusion 1a is formed. After the extrusion of the block the main valve 15 is again closed by the closing of the valve 20 and therefore the pressure from the tank 10 is no longer communicated to the cylindrical portion 8. Retraction of the ram is accomplished by opening the valve 13 and closing the valve'12 to pressurize conduit 11 and force the piston 5 backwardly. The check valve 6 is :maintained closed and fluid pressure escapes solely through the conduit 11 to the drain (arrow A).

When the outlet valve 12 is closed, the hydraulic pressure in cylinder 7 builds up suiciently to stop the forward stroke of the main press piston 4 when the starting position shown in FIG. 2 is reached.

The main valve 15 is of larger dimensions than the valves in the housing 33. In order to effect the work stroke of the ram 4a from its position shown in FIG. 2,

the valve 15 is opened. This is effected by operating the y control valves 19 and 20, so that fiuid pressure from tank is applied through conduit 21 to raise the piston 22 of valve from its lower position shown in FIG. 2 to its upper position shown in FIG. 3. Thereupon pressurized fluid from tank 10 is admitted with suddenness to cylinder 8 through line 35, channel 37 and conduit 14.

As the piston 4 moves forward, there is a pressure build-up in cylinder 7 in front of piston 5. This pressure reaches a comparatively high level and exceeds the water pressure of the water stored in tank 10. In order to relieve the retraction piston and to reduce the resistance to the forward movement of ram 4a, the check valve 6 opens in response to the pressure build-up and water in cylinder 7 fiows out through conduit 9 back into the storage tank 10. i

To release the ram stroke of ram 4a the outlet valve 20 of operating piston 22 is closed and inlet valve 19 is opened. The cylinder of operating piston 22 is then connected via conduits 21, 23 with water tank 10 and thus the large dimensioned main inlet valve 15 is opened. As a consequence, the main press piston 4 performs its quick blow stroke on its path S. Water retained in cylinder 7 of the retraction piston escapes via open check valve 6' and conduit 9 into water tank 10, the retraction remaining thus constant. Upon hitting the metal block 1 by means of ram 4a, this block is thus extruded and an extrusion piece 1a is obtained. Thereafter, inlet valve 19 is being closed, outlet valve 20 is opened and springloaded valve 15 is closed, the water pressure being interrupted.

The work stroke of the ram 4a results in the extrusion of the metal workpiece 1, under the high ram velocity, through the extrusion die 2a to form the extrusion 1a. After the workpiece has been extruded, the main valve 15 is closed by operating control valve 20 so as to cut off the hydraulic pressure applied to the main press piston 4.

The piston 4 is then retracted, as previously explained, by opening the retraction inlet valve 13 to connect the hydraulic pressure supply 10 to cylinder 7 over conduits 23 and 11 so as to retract piston 5, and, at the same time cylinder 8 is connected through conduits 14 and 17 to the vessel 16 by opening the feed valve 18.

vVarious changes and modifications may be made without departing from the spirit and scope of the present invention and it is intended that such obvious changeshand modifications be embraced by the annexed claims.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent, is:

l. A fluid pressure operated extrusion press comprising cylindrical housing means having a die opening for extruding material therethrough, means for mounting a workpiece in alignment with the die opening for extrusion through the opening, an extrusion ram including a small diameter forward ram portion reciprocatable in said housing to contact the workpiece and extrude it through said die opening, said ram including an intermediate pressure piston portion of relatively, large diameter connected to said ram portion and a retracting piston portion of relatively small diameter connected to said intermediate piston portion on the opposite end thereof from said ram piston portion, said cylindrical housing means dening iiuid tight cylindrical press and retracting portions for each of said press and retracting piston portions, respectively, a first fluid pressure source, a first return conduit connecting said first fluid pressure source and said retractable piston portion at a location thereon adjacent said intermediate piston portion, check valve means in said first return conduit, a second conduit connecting said first pressure source and said intermediate cylindrical portion on an end thereof adjacent said retractable cylindrical portion, a third conduit connecting said retractable cylindrical portion at an end thereof adjacent said intermediate cylindrical portion and said rst pressure source, ydisplaceable control valve means in said third conduit, main operating valve means in said second conduit, second fiuid pressure source connected to said main operating valve means, a drain conduit connected to said control valve means, said main operating valve means including displaceable Valve members for selectively communicating said first and second pressure sources to said intermediate cylindrical portion, said control valve means also including means for selectively connecting said first pressure source to said retractable cylindrical portion and connecting said retracting cylindrical portion to said drain, said third conduit being connected between said first pressure source and said retracting cylindrical portion to move said retracting pistonto a retracted position to bring said ram out of contact with the workpiece when the control valve means in said third conduit is correspondingly set, said second pressure source being in communication with said intermediate cylindrical portion when said main operating valve is correspondingly set to move said intermediate piston portion to a starting position with the ram spaced a predetermined distance from the workpiece, said first fiuid pressure being communicable with said cylindrical piston portion after said second pressure Source is disconnected therefrom by the predetermined setting of said main'operating valve means, said retractive piston portion being connected back to said pressure source through said rst return conduit and said check valve means when the pressure between said retractive piston and the end of the retractive cylindrical portion adjacent said intermediate cylindrical portion exceeds the amount of said first pressure source as determined by said check Valve means.

2. A fluid pressure operated extrusion press comprising cylindrical housing means having a die opening for extruding material therethrough, means for mounting a workpiece in alignment with the die opening for extrusion through the opening, an extrusion ram including a small diameter forward ram portion reciprocatable in said housing to contact the workpiece and extrude it through said die opening, an intermediate pressure piston portion of relatively large diameter connected to said ram portion and a retracting piston portion of relatively small diameter connected to said intermediate piston portion on the opposite end thereof from said ram piston portion, said cylindrical housing means defining fluid-tight cylindrical pressure piston, ram and retracting portions for each of said press and retracting piston portions, respectively, first fluid pressure means, second fiuid pressure means, a first return conduit connected to said fluid pressure means and said cylindrical housing retracting portion adjacent to the end thereof adjacent said cylindrical housing pressure piston portion, check valve means permitting flow only from said cylindrical housing retracting portion to said first fluid pressure means when the pressure in said ram portion exceeds that of said first fiuid pressure means, a low pressure drain conduit, a control valve assembly including a housing having an interior drain passage connected to said drain conduit, an operating pressure conduit connected to said retracting cylindrical portion adjacent the end thereof next to said cylindrical pressure piston portion, an operating pressure passage connected to said first pressure source, said drain passage and said operating pressure conduit, a main valve control housing, a control passage connected to said first pressure source, said drain conduit and said main valve contro-l housing, a first combined closed-open valve including a portion adapted when in one position to close the connection between said operating passage and said first pressure source and open the connection between said operating passage and said drain passage and vice 7 versa when in the opposite position, a second combined closed-open valve including means to open said first pressure source and close said control passage in one position and vice versa in the other position, said main valve control housing including first control passage connecting said first pressure source and said intermediate cylindrical portion at the end thereof adjacent said retractive portion, a second control passage connecting said rst passage and said second pressure source, a rst main valve including a portion biased against the pressure of said control passage When said valve closes the connection between said rst pressure source and said first control passage, and being displaceable upon increase in pressure to open and communicate the connections between said rst pressure source and said first control passage, a second main valve having a portion exposed to pressure in said operating conduit and biased thereagainst when closing the connection between said second control passage and said first control passage, and being displaceable to communicate pressure of said second pressure source to said intermediate cylindrical portion.

References Cited in the le of this patent UNITED STATES PATENTS

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