US3709013A

US3709013A - Extrusion press for rod or tube

Info

Publication number: US3709013A
Application number: US00038826A
Authority: US
Inventors: E Petsch
Original assignee: Maschinenfabrik Sack GmbH
Current assignee: Maschinenfabrik Sack GmbH
Priority date: 1969-05-29
Filing date: 1970-05-19
Publication date: 1973-01-09
Anticipated expiration: 1990-01-09
Also published as: JPS4926188B1; CH503525A; DE1927396A1; GB1312703A; DE1927396B2; FR2048967A5; AT300508B

Abstract

A hydraulic rod and tube extrusion press having a main extrusion ram and a piercer connected to a piston which works in a cylinder within the extrusion ram. In order to extrude tube around the piercer with the tip of the piercer stationary in the mouth of the die means are provided for supplying fluid to the return stroke chamber of the piercer piston cylinder so that the piercer is retracted at an appropriate rate relatively to the extrusion ram as the extrusion ram advances.

Description

O United States Patent 1 [111 3,709,013 Petsch [451 Jan. 9, 1973 [54] EXTRUSION PRESS FOR ROD OR [56] References Cited TUBE UNITED STATES PATENTS [75] inventor: Ernst Petsch, Mettmann, Germany 3,362,208 1/1968 Murphy ..72/265 X [73] Assignee: Maschinenfabrik Sack Gmbl-I, Dus- 2,063,562 12/1936 Sparks ..72/271 X seldorf-Rath, Germany Primary Examiner-Charles W. Lanham [22] Filed: May 1970 Assistant Examiner-R. M. Rogers [2]] APPL No: 38,826 Attorney-McGlew and Toren [57] ABSTRACT [30] Foreign Application p i it Data A hydraulic rod and tube extrusion press having a main extrusion ram and a piercer connected to a y 29, 1969 Germany 19 27 396-2 piston which works in a cylinder within the extrusion ram. In order to extrude tube around the piercer with the tip of the piercer stationary in the mouth of the die [52] US. Cl ..72/22, 72/265 means are provided for supplying fluid to the return [5 Intstroke chamber of the piercer piston cylinder so [58] Field of Search ..72/265, 22 the piercer is retracted at an appropriate rate relatively to the extrusion ram as the extrusion ram advances.

6 Claims, 6 Drawing Figures PATENTEDJAN 9 I975 3.709013 sum 3 OF 4 IN VEN TOR E'RVST PeTsw EXTRUSION PRESS FOR ROD OR TUBE The invention relates to hydraulic rod and tube extrusion presses of the kind equipped with a piercing device consisting of a double-acting hydraulic piercer piston which supports a piercer and works inside the main extrusion ram of the press.

Extrusion presses of this kind are usually arranged in such a way that tubes can be extruded by either of two alternative methods. By the first method the piercer advances with the main ram during the extrusion of the tube. After the piercer has pierced the workpiece blank the ram and the piercer advance together. By the second method the piercer remains stationary during the extrusion of the tube. After the piercer has pierced the workpiece blank the piercer continues to advance through a short distance only and then remains stationary in the mouth of the extrusion die. The piercer then remains stationary in this position while the ram advances, extruding the tube. The first of these two methods encounters no particular difficulties, but the second method, in which the piercer remains stationary during tube extrusion, involves a comparatively costly press construction.

Three methods are known for holding the piercer stationary during tube extrusion:

By the first method a piercer cylinder containing a rearward extension of the piercer piston is mounted behind the ram cylinder, the piercer piston penetrating through the wall of the ram cylinder and through the ram piston, and being guided by the hollow ram. At its forward end the piercer piston supports the piercer holder and piercer. The piercer cylinder must be very long to allow for the long total stroke of the piercer piston. This total stroke includes both the ram piston stroke and the stroke of the piercer piston relative to the ram piston during which the piercer travels all the way from its retracted position in the ram punch, through the dummy block and through the workpiece blank into the mouth of the extrusion die. The long piercer cylinder must be mounted at a distance behind the ram cylinder at least equal to the ram stroke. The entire extrusion press is therefore very long, and correspondingly costly to construct.

By the second known method for holding the piercer stationary during tube extrusion the piercer cylinder containing the piercer piston is mounted to slide in the punch holder through a distance equal to the stroke of the piercer piston relative to the ram. During tube extrusion the piercer must be held stationary in the mouth of the extrusion die by axial support. A piercer piston holder has projections which project outwards through slots in the punch holder, the movements of the projections being limited by mechanical stops to agree with the stroke of the piercer relative to the ram. The punch holder must therefore be quite long and the entire extrusion press is correspondingly long. In particular this arrangement involves the use of long tension members, which extend undesirably under the influence of the extrusion pressing forces.

By the third method a piercer piston is installed in a rearward and outward extension of the ram. This method has the disadvantage that the ram extension occupies a considerable cross sectional area in the ram cylinder, which must consequently be correspondingly large and costly to construct. The extrusion press is rather long, although it is not as long as the press used in the first of the three methods.

The object of the present invention is to provide for operation of an extrusion press of the kind described which allows the press to be constructed as short as a conventional press which is suitable only for extruding rod and not suitable for extruding tube.

In accordance with the invention, a method of operating a hydraulic rod and tube extrusion press of the kind equipped with a piercing device consisting of a double acting hydraulic piercer piston which supports a piercer for piercing a workpiece blank and which works inside a main extrusion ram of the extrusion press, is characterized in that to enable tube to be extruded through a die around the piercer with the piercer tip substantially stationary in the mouth of the die, hydraulic fluid is fed into a return cylinder chamber for the piercer piston within the main extrusion ram at a rate of flow such that the piercer is retracted relatively to the ram and remains substantially stationary whilst the main extrusion ram advances to extrude the tube.

The invention also includes a rod and tube extrusion press for carrying out the method, the press having a piercing device consisting of a double acting hydraulic piercer piston which supports the piercer for piercing a workpiece blank and which works inside a cylinder within a main extrusion ram of the extrusion press, there being means which is responsive to the axial position of the piercer and which controls the flow of hydraulic fluid to a return chamber of the cylinder within the main extrusion ram whereby when the press is set up for extruding tube around the piercer the piercer can automatically be retracted relatively to the main extrusion ram so as to maintain the tip of the piercer substantially stationary within the mouth of the die whilst the main extrusion ram advances to extrude the tube. With this arrangement, the piercer is held stationary purely by hydraulic means, and not by any sort of mechanical construction as described above, so that the disadvantages mentioned are removed.

The invention has the great advantage that it allows a simple press constructed exclusively for rod extrusion to be converted easily into a press for rod and tube ex-' trusion merely by replacing the extrusion ram, that is to say by installing a different ram, and adding some hydraulic controls, without this involving any increase in the size of the machine.

The means responsive to the axial position of the piercer may be a mobile trigger, or an electric contact or other control element situated to one side of the axis of the press and mechanically connected to the piercer. The control element is mounted on the machine in such a way that during the operation of the machine the distance between the trigger and an actuator or other complementary element is always the same as the distance between the existing position of the piercer and its final, fully advanced position in the mouth of the extrusion die. The actuator actuates a control valve in a hydraulic line which connects the piercer cylinder to a source of hydraulic pressure so that when the piercer has advanced a little beyond its desired forward limiting position in the mouth of the extrusion die the control valve, actuated by the trigger through the actuator, admits hydraulic fluid under pressure to the return chamber of the piercer cylinder, thrusting the piercer piston slightly back again so that thepiercer returns through a short distance outwards. This is only a very short movement, the piercer remaining essentially in the mouth of the extrusion die. In effect the piercer is retained constantly, during tube extrusion, at its desired final position in the mouth of the extrusion die, although oscillating very slightly about a mean position, from which it deviates. at most by a very few millimeters. This slight oscillating movement of the piercer does no harm. Moreover in practice the slight oscillations are often effectively damped by the natural inertia and viscous drag in the system.

The mechanical connection between the piercer and the mobile trigger can take the form of a flexible cable or chain or the like, which is led out through the side of the extrusion ram.

In order to allow the press to extrude tube when desired by the travelling piercer method, in which the piercer advances during the extrusion with the punch, the mobile trigger is preferably arranged so that it can be rendered inoperative.

An example of a press constructed in accordance with the. invention is shown in the accompanying drawings, in which:

FIGS. 1 to 4 show the press in axial section in a succession of operating positions; and,

FIGS. 5 and 6 show, to a larger scale, a hydraulic control valve with auxiliary parts, in two different operating positions.

The extrusion press shown in FIGS. .1 to 4 consists of a ram cylinder 1, a reaction crosshead 2, tie rods 3 with nuts for attaching the ram cylinder 1 to the reaction crosshead 2, a main ram 4, hydraulic connections 5 and 61on the ram" cylinder 1 for feeding and removing the hydraulic fluid during the forward and return strokes of the ram 4, a container 7 and a die holder 8 which is represented diagrammatically and contains the extrusion die. .On the outer end of the ram 4 there is mounted a punch holder 9 for a punch 10, the reaction thrust from the punch being taken by a thrust pad 10a.

In FIG. 1 the press is shown before the beginning of the extrusion cycle. A workpiece blank 12 is shown ready for extrusion, a dummy block 11,.iwhich has a hole in the middle, being interposed between the workpiece blank 12 and the ram punch 10.

The ram 4 is hollow and contains a piercer cylinder in which works a piercer piston 13 which drives a piercer 15. The piercer piston 13 divides a cylindrical drilling in the interior of the ram4 into two

cylinder chambers

13a and 13b. .The piercer piston 13 drives a piercer holder 14 which in turn drives the piercer 15. Hydraulic fluid is supplied to the

piercer cylinder

13a, 13b by a simple hydraulic system consisting of a pump 16, a tank 17 for hydraulic fluid, and excess fluid release valve 18 and a control valve 19 which is actuated, during the operating of the machine, so as to drive the piercer piston 13 forwards or backwards, relative to the ram piston 4, or so as to retain the piercer piston 13 stationary relative to the ram piston 4. This control valve 19 is actuated in the known way by means which are not shown in the drawing. Actuation is usually by electrically controlled solenoids which respond to limit switches triggered by the movements of the machine during the operating cycle.

The pressis equipped with a further control valve 20 containing a slider 21. A compression spring 22 acts on the slider, tending to hold the slider in the position represented in FIG. 1. The purpose of this control valve 20, and its method of functioning, will be described further below.

A hydraulic lead 23 connects the pump 16 to the control valve 19 and to the controlslider valve 20. A

return line 24 takes hydraulic fluid from the valves 19 and 20 back to the storage tank 17. From the control valves 19 and 20 pressure leads 25, constructed in several sections, take hydraulic fluid under pressure to the advance stroke cylinder chamber 13a for advancing the piercer piston 13 relative to the ram piston 4..

Further hydraulic pressure lines 26, also constructed in several sections, convey hydraulic fluid under pressure to the return stroke chamber 13b for the return stroke of the piercer 15. These two

hydraulic lines

25 and 26 are made in articulated sections to allow for the movements of the ram 4 relative to the hydraulic control system.

A cable 27 attached to the piercer piston 13 passes over two deflector rollers 29, the other end of the cable being coiled on a drum 28 which is loaded by a spring so as tokeep the cable 27 constantly taut. The cable 27 passes sideways out of the ram assembly between the two guide rollers 29. Fixed to the cable 27 there is a mobile trigger 30 which cooperates with an axially adjustable actuator 32mounted on a sliding rod 31 to which there is attached an actuator arm 33 which thrusts against the slider 21 of the control valve 20. The slider 21 is the actuating device mentioned further above. The rod 31 slides in a frame 34.

The extrusion press functions as follows:

At the beginning of the operating cycle the parts are in the positions shown in FIG. 1 and the control valve 19 is shut, locking the piercer piston 13 stationary relatively to the ram 4. If it is desired to extrude a rod from the workpiece blank 12, rather than a tube, the control valve 19 remains closed and the piercer remains housed in the punch 10. For extruding rod a dummy block 11 without a hole is used. The process of extruding rod need not be described here.

For extruding tube the control valve 19 is actuated to return the piercer piston 13 into its fully retracted position. A dummy block 11 with a hole in the middle is used. The ram 4 is advanced, the ram punch 10 driving the workpiece blank 12 into the container 7. The control valve 19 is then actuated to drive the piercer 15 forwards by hydraulic pressure applied in the cylinder chamber 131:. The piercer isdriven forwards through the hole in the dummy block until the piercer strikes the workpiecev blank 12. The parts are now in the positions shown in FIG. 2. This forward movement of the piercer requires very little driving pressure in the cylinder chamber 13a. However as soon as the piercer strikes the workpiece blank 12, hydraulic pressure builds up in the cylinder chamber 13a. The increasing hydraulic pressure is utilized to actuate a pressure sensitive switch which returns the control valve 19 into its closed position, locking the piercer piston 13 in the ram 4 so that the piercer 15 is locked stationary relatively to the press punch 10. The driving faces of thepunch l0 and of the tip 15a of the piercer therefore remain stationary relative to each other.

The ram 4 is then driven forwards through a further short distance so as to upset the workpiece blank 12. The parts are now in the positions shown in FIG. 2. The ram 4 is then retracted through a short distance so as to leave a little space in the container, for receiving the workpiece material which will be driven backwards during the piercing operation. To start the piercing operation the control valve 19 is actuated to drive the piercer piston 13 forwards, the ram 4 being locked hydraulically in position in the ram cylinder 3, so that the ram cannot move in its cylinder. The piercer advances, piercing the workpiece blank 12, until the parts reach the positions shown in FIG. 3. The piercer piston 13 is now in its forward limiting position, having completed the entire stroke indicated at R in FIG. 3. The parts of the press are dimensioned so that the tip 15a of the piercer is now in the mouth 8a of the extrusion die.

Let it be assumed, for the present, that a tube is going to be extruded by the first method, in which the piercer advances with the punch. For this kind of extrusion the valve 19 remains as it is, so that the cylinder chamber 130 behind the piercer piston 13 contains hydraulic fluid under pressure. The mobile trigger 30 is inactivated, so that it cannot cooperate with the actuator 32. The ram 4 advances, the piercer 15 advancing with the press punch 10. On the other hand if it is desired to extrude tube by the second method, the piercer tip 15a must remain stationary in the mouth 8a of the extrusion die during the forward movement of the ram 4 and the press punch 10.

The method of functioning of the extrusion press as described up to now is known. What is new in the present invention is that novel means are used for retaining the piercer tip 15a stationary in the mouth of the extrusion die during extrusion of tube by the second method.

According to the invention, to extrude tube with the piercer tip stationary in the mouth of the die, the control valve 19 is closed, so that it is inoperative. The mobile trigger 30 is engaged, so that it can cooperate with the actuator 32, that is to say the trigger is brought back into line with the actuator. All movements of the piercer piston 13 relative to the ram 4 are now controlled exclusively by the slider valve 20. The further function of the extrusion press will now be described with the help of FIGS. 5 and 6.

For tube extrusion with a stationary piercer the mobile trigger 30 is adjusted in position on the cable 27 in such a way that with the piercer piston fully retracted in the ram, as represented in FIG. 1, the distance between the trigger 30 and the actuator 32 is equal to the distance between the piercer tip 150, in the position shown in FIG. 1, and the position of the piercer tip in the mouth ofthe extrusion die during tube extrusion, as represented in FIG. 4. During tube extrusion the forward face of the piercer tip normally projects somewhat into the die mouth, for example by the amount of the small distance as indicated in FIG. 3. Under these circumstances the mobile trigger 30 rests in contact with the end face of the actuator 32, as represented in FIG. 5.

A small movement now takes place, both the ram 4 and the piercer 15 advancing through a little distance, towards the right in FIG. 4. The trigger 30 follows this movement, also advancing through a little distance towards the right, and so thrusting the actuator 32 and the slider of the valve 20 towards the right. This opens the valve 20, bringing it into the position shown in FIG. 6. Only a small movement of the mobile trigger is required to effect this, as indicated at x in FIGS. 5 and 6. With the valve 20 open hydraulic fluid passes from the pump 16 through the

lines

23 and 26 into the return cylinder chamber 13b, returning the piercer tip 15a through the small distance x, back again into the position shown in FIG. 5, the valve 20 also opening the hydraulic

fluid return line

25, 24 so that hydraulic fluid expelled from the cylinder chamber returns to the storage tank 17.

This small movement of the piercer tip 15a can be repeated intermittently during the extrusion of the workpiece blank 12, the piercer l5 performing an oscillating movement of amplitude at most equal to x. By suitably constructing the control valve 20 the amplitude of this oscillation can be limited to quite a small value, of the order of a few millimeters. Moreover the natural inertia and viscous drag in the control system usually ensures that the slider of the valve 20 remains quiescent in an intermediate position such that fluid flows constantly into the cylinder chamber'13b and out of the chamber 1311, the piercer remaining practically stationary in the mouth of the extrusion die. It should however be observed that an oscillation of the piercer even through the full distance is quite harmless.

For the sake of simplicity in description it has been assumed in the present example of the invention that the control device which controls the flow of hydraulic fluid is a valve actuated by a mechanical trigger. It would however be perfectly possible to replace the mechanical trigger by an electric contact, the other contact being the actuating device. When the contacts close this actuates the valve electromagnetically. This arrangement would shorten the distance x. As a further alternative instead of using a control valve a variable delivery pump could be used as the pump 16, for controlling the supply of hydraulic fluid to return the piercer tip. The variable delivery pump could be controlled mechanically or electrically. If electric control is used the mechanical trigger 30 can be replaced by an electric sliding contact which slides on a potentiometer with the forward movement of the piercer in the die mouth, the potentiometer controlling the current supply to the pump. In this way it should be possible to suppress the oscillation of the piercer tip entirely. This can be done using any fluid flow control device which supplies fluid at a controlled rate to the return thrust surface of the piercer piston during the forward travel of the ram with the ram punch and the piercer piston. If the supply of fluid is correct the piercer tip remains stationary in the mouth of the die.

I claim:

I. A rod and tube extrusion press comprising extrusion die means, a main extrusion ram adapted to extrude rod or tube through said die means, internal parts of said extrusion ram defining a cylinder therein, a piercer piston within said cylinder, a piercer connected to said piston, hydraulic fluid supply means adapted to supply hydraulic fluid to said cylinder on one or other side of said piston to advance or retract said piercer from said extrusion ram, and means responsive to the axial position of saidpiercer and controlling said hydraulicfluid supply means whereby hydraulic fluid is automatically supplied to said cylinder on said other side of said piston to retract said piercer relatively to said extrusion ram at a rate to maintain a tip of said piercer substantially stationary within said die means as said extrusion ram advances to extrude tube through said die means around said piercer, said axial position responsive means comprising a control element, means mechanically connecting said control element to said piercer on one side thereof whereby said control element moves axially with said piercer, and a complementary element adapted to co-operate with said control element to control said hydraulic fluid supply means, said control element being positioned, when said piercer tip is in'its fully retracted position, at a distance from said complementary element equal to the distance between said fully retracted piercer tip and the position of said tip when it is in its advanced position in said die means, said hydraulic fluid supply means admitting hydraulic fluid under pressure to said other side of said piston when said control element engages said complementary element, said means interconnecting said piercer and said control element including aflexible tension member which emerges laterally from said extrusion ram;

2. A press according to claim 1, wherein the cooperative function of said elements can selectively be rendered inoperative to'enable extrusion of tube with an advancing piercer.

3. In an hydraulic extrusion press of the type including a die through which extrusion iseffected, a ram for extruding material through said die, a piercer adapted to coact with said ram and movable relative thereto, and hydraulic means for controlling the position of said piercer, the improvement comprising means for sensing the position of said piercer during said extrusion operation, and means responsive to said sensing means for automatically continuously controlling said hydraulic means to maintain said piercer at-a fixed position relative to said die during said extrusion.

4. A press according to claim 3 wherein said responsive means comprise valve means operable to control fluid flow in said hydraulic means, and wherein said sensing means include trigger means mounted for movement simultaneously with said piercer and driven thereby, said trigger means being operative to actuate said valve means to maintain said piercer at a predetermined position by controlling fluid flow in said hydraulic means.

5. A press according to claim 4 wherein said trigger means include a cable attached to said piercer and movable simultaneously therewith.

6. A press according to claim 4 wherein said hydraulic means include piercer piston means defining a pair of opposed hydraulic chambers for driving said piercer in either of two opposite directions, said valve means operating in response to said trigger means to selectively supply hydraulic fluid to either of said chambers to maintain said piercer fixed relative to said die at a predetermined position.

Claims

1. A rod and tube extrusion press comprising extrusion die means, a main extrusion ram adapted to extrude rod or tube through said die means, internal parts of said extrusion ram defining a cylinder therein, a piercer piston within said cylinder, a piercer connected to said piston, hydraulic fluid supply means adapted to supply hydraulic fluid to said cylinder on one or other side of said piston to advance or retract said piercer from said extrusion ram, and means responsive to the axial position of said piercer and controlling said hydraulic fluid supply means whereby hydraulic fluid is automatically supplied to said cylinder on said other side of said piston to retract said piercer relatively to said extrusion ram at a rate to maintain a tip of said piercer substantially stationary within said die means as said extrusion ram advances to extrude tube through said die means around said piercer, said axial position responsive means comprising a control element, means mechanically connecting said control element to said piercer on one side thereof whereby said control element moves axially with said piercer, and a complementary element adapted to co-operate with said control element to control said hydraulic fluid supply means, said control element being positioned, when said piercer tip is in its fully retracted position, at a distance from said complementary element equal to the distance between said fully retracted piercer tip and the position of said tip when it is in its advanced position in said die means, said hydraulic fluid supply means admitting hydraulic fluid under pressure to said other side of said piston when said control element engages said complementary element, said means interconnecting said piercer and said control element including a flexible tension member which emerges laterally from said extrusion ram.

2. A press according to claim 1, wherein the co-operative function of said elements can selectively be rendered inoperative to enable extrusion of tube with an advancing piercer.

3. In an hydraulic extrusion press of the type including a die through which extrusion is effected, a ram for extruding material through said die, a piercer adapted to coact with said ram and movable relative thereto, and hydraulic means for controlling the position of said piercer, the improvement comprising means for sensing the position of said piercer during said extrusion operation, and means responsive to said sensing means for automatically continuously controlling said hydraulic means to maintain said piercer at a fixed position relative to said die during said extrusion.