US2893552A - Tensioning apparatus for extrusion presses - Google Patents

Description

July 7, 1959 E. D. DAVIES 2,893,552

TENSIONING APPARATUS FOR EXTRUSION PRESSES Filed Oct; 27, 1955 4 Sheets-Sheet 1 1\ I INVENTOR Y ENOCH D. DAVIES ATTORNEY July 7, 1959 E. D. DAVIES TENSIONING APPARATUS FOR EXTRUSION PRESSES Filed 001;. 27, 1955 4 Sheets-Sheet 2 iNVENTOR ENOCH D. DAVIES WWW ATTORNEY July 7, 1959 E. D. DAVIES 2,893,552

TENSIONING APPARATUS FOR EXTRUSION PRESSES Fil ed Oct. 27. 1955 4 Sheets-Sheet 3 lNVENTOR ENOOH D. DAVIES ATTORNEY- July 7, 1959 E. D. DAVIES 2,893,552

' mnslomuc APPARATUS FOR EXTRUSION PRESSES Filed 001;. 27, 1955 4 Sheets-Sheet 4 FIG. 8

d 1 h? --G.| 22 I ENVENTOR ENOGH D. DAVIES ATTORNEY United States Patent TENSIONING APPARATUS FOR EXTRUSION PRESSES Enoch D. Davies, Wild Rose, Wis., assignor to The Oilgear Company, Milwaukee, Wis., a corporation of Wisconsin Application October 27, 1955, Serial No. 543,103

Claims. (Cl. 207-4) This invention relates to apparatus for maintaining ten-- sion on material as it is being extruded through a die.

Apparatus embodying the invention is particularly adapted to maintain tension on extrusions of aluminum during the extruding operation and the invention will be explained as being employed for that purpose, but it is not limited to that particular use.

An aluminum extrusion press ordinarily includes a container to receive the material to be extruded, a die which is rigidly held in contact with the front end of the container during the extruding operation and has one or more holes of the desired configuration extending therethrough, a ram to enter the rear end of the container and force material therefrom through the holes in the die, and a hydraulic motor for operating the ram. If the cross-sectional area of the extrusion is relatively large, the die may have only one or two holes extending therethrough but, if the cross-sectional area of the extrusion is small, the die may be provided with a larger number of holes, such as five holes.

Extrusion is effected by placing a billet of aluminum in the container and starting the motor which will advance the ram into the container and cause it to force aluminum from the billet through the die. The extrusions thus formed pass onto a table, the top of which is coated with a graphited composition to prevent it from marring the extrusions.

The motor is at first operated at a slow speed to cause the extrusions to emerge slowly from the die until the end of each extrusion has been grasped by an attendant with vise-grip pliers and then the motor is speeded up to cause the material to be extruded at a predetermined maximum rate, such as three feet per second. At the present time, the attendants walk along the table, which in some cases is sixty feet long, and each attendant guides his extrusion along the table to keep it from engaging and being marred by any other extrusion. Thus there must be as many attendants as there are holes in the die, particularly as the characteristics of the holes in the die cause the extrusions to emerge at difierent rates. Also, each attendant should pull on his extrusion with suflicient force to keep it reasonably straight.

When the extrusions reach the desired length or when the billet is nearly consumed, the ram is retracted and the motor stopped. Then the extrusions are sheared from the remaining portion of the billet, thus leaving the ends of the extrusions in the die from which they must be stripped ice die and will strip them from the die at the end of the extruding operation.

Other objects and advantages will appear from the following description of the embodiments of the invention shown schematically in the accompanying drawings in which the views are as follows:

Fig. 1 is a hydraulic circuit diagram of a tensioning apparatus in which the invention is embodied.

Fig. 2 is a section taken on the line 2--2 of Fig. 1 but drawn to a larger scale and with the reduction gear casings and the hydraulic motors shown in full.

Fig. 3 is a top plan view of parts of the tensioning apparatus with the top plate removed, the plane of the view being indicated by the line 3-3 of Fig. 2.

Fig. 4 is a transverse section taken on the line 4--4 of Fig. 3.

, Fig. 5 is a longitudinal section taken on the line 5-5 of Fig. 3.

Fig. 6 is a view drawn to a larger scale than Fig. 5 and showing a vise-grip plier which is used for gripping an extrusion and has a hook for engaging a chain such as that shown in Fig. 5.

Fig. 7 is a sectional plan view of certain parts and a plan view of other parts of a tensioning apparatus for use with a machine which makes five extrusions at a time, the sections being taken approximately on the irregular line 7--7 of Fig. 8.

Fig. 8 is a transverse section taken on the line 8-8 of Fig. 7.

Fig. 9 is a view showing how a tensioning apparatus may be arranged above the extrusion die instead of below it as is the case with the tensioning apparatus shown in the other views.

An embodiment of the invention has been shown in Fig. 1 as being associated with an extrusion press having a stationary container 1 to receive an aluminum billet 2, a die 3 which is rigidly held against the outer end of container 1 during an extruding operation and has two holes 4 extending therethrough, a hydraulically operated ram 5 and a butt shear 6. The other parts of the press have not been illustrated because the press per se forms no part of the present invention. It is deemed sufficient to state herein that ram 5 is advanced by a hydraulic motor (not shown) and forces metal from billet 2 through holes 4 to form an extrusion 7 having the same cross-sectional configuration as holes 4 and that, at the end of the extruding operation, die 3 is moved away from container 1 and shear 6 is advanced and shears extrusion 7 from the remainder of billet 2. Each hole 4 is tapered and increases in cross-sectional area from its entrance end toward its exit end but Fig. l is drawn to such a small scale that the taper cannot be shown.

FIGS. 1-6

The tensioning apparatus shown in these figures includes an elongated table comprising a frame 8 and a top plate 9 having two slots 10 and 10 extending there through for the greater part of its length. The table is arranged parallel to the axis of ram 2 with the end of plate 9 adjacent to die 3 and somewhat below holes 4.

Frame 8 has two drive shafts 11 and 11 journaled in its opposite sides near its left end and two sprocket wheels 12 and 12 are fixed on shafts 11 and 11 in alignment with slots 10 and 10 respectively. Shaft 11 is connected to a hydraulic motor M1 through a reduction gear G1 and shaft 11 is connected to a motor M1 through a reduction gear G1.

Sprockets 12 and 12 are connected, respectively, by two roller link chains 15 and 15 to two idler sprocket wheels 16 and 16 which are arranged in alignment with slots 10 and 10, respectively, and journaled on a shaft 17 carried by frame 8 near the right end thereof.

The inlets of the motors M1 and M1 are connected by a channel '18 to the outlet of a pump P1 which has its inlet connected to a reservoir 19 by a channel 20 having a check valve 21 arranged therein. Pump P1 when driven will draw liquid from reservoir 19 and discharge it into channel 18. The outlets of motors M1 and M1 are connected to an exhaust channel 22 which discharges into the reservoir 19. When the motors are energized by liquid from pump P1, they will rotate shafts 11 and 11 and cause the upper reaches of chains 15 and 15 to travel away from die 3, and the liquid discharged by the motors will flow through channel 22 into reservoir 19.

The parallel connection of the hydraulic motors provided by channel 18 is a hydraulic means that causes the hydraulic motors to share the flow of fluid from the pump inversely in accordance with their hydraulic resistances. This results in the rate of flow to each motor being proportionate to their torque rating and the proportionate flow to each motor varying inversely with changes in its torque load relative to the torque load on the other motor. Where the tensions should be equal, therefore, the flow rate through each motor and therefore the speed responds to the lineal speed of its attached extrusion in order to maintain the same tension thereon as on each of the other extrusions.

In order to prevent an unloaded motor from racing when another motor is loaded, a flow control valve is connected in series with each motor. The flow control valves may control the rates at which liquid enters the motors or the rates at which liquid is discharged therefrom. Asshown, a fiow control valve V1 is connected into a branch of exhaust channel 22 in series with'motor M1- and a flow control valve V1 is connected into a branch of exhaust channel 22 -in series with motor M1. The two flow control valves are alike and each comprises an orifice choke 23 and a pressure regulating valve 24 which maintains a constant pressure'at the inlet of choke 23.

In order that pump P1 may continue to run when motors M1 and Ml are idle, means are provided for bypassing the pump. As shown, a bypass valve 25 is con nected between channels 18 and 22. Valve 25 comprises a valve body 26 having an axial bore 27 and two annular grooves or ports 28 and 29 formed in the wall of the bore, a valve member 30 which is fitted in the bore and controls communication between the ports, and a spring 31 which normally holds valve member 30 in open position as shown. Port 28 is connected to channel 18 by a channel 32 and port 29 is connected to channel 22 by a channel 33. Valve 25 may be closed in any suitable manner such as by a solenoid 34 connected to thestem of the valve member 30.

The arrangement is such that, when pump P1 is running and valve 25 is open as shown, all of the liquid discharged by pump P1 will flow through channels 18 and 32, valve 25 and channels 33 and 22 into reservoir 19. Then when solenoid 34 is energized, it will raise valve member 30 which will block port 28 and thereby cause the liquid discharged by pump P1 to flow through channel 18 to motors M1 and M1 to energize the same.

Pump P1 may be of any type which has a member shiftable to vary its displacement and a control which will cause the pump to discharge liquid at predetermined maximum rate until pump pressure reaches a predeter- -mined maximum and will then reduce pump displacement until the pump is delivering just enough liquid to maintain that pressure constant.

For the purpose of illustration, the pump has been indicated as being of the rolling piston type disclosed in Patent No. 2,074,068, and as having a pressure responsive control of the type disclosed in Patent No. 2,080,810. Since both the pump and the pump control are well "known and in extensive commercial use, it is deemed su'fiicient to state herein that pump P1 includes a displacement varying member or slide block 38 which is arranged in a casing 39 andis shiftable therein between a neutral or zero displacement position and a maximum displacement position, and that pump P1 when driven will discharge liquid into channel 18 at a rate proportional to the distance slide block 38 is offset from its neutral position.

Slide block 38 is urged toward maximum displacement position by a constant force which may be provided by a spring or, as shown, by a servo-motor comprising a cylinder 40 which is carried by casing 39 and a piston 41 which is fitted in cylinder 40 and engages or is fixed to a slide block 38. Liquid for energizing servo-motor 4041 is suppliedby a gear pump P2 which when driven will draw liquid from reservoir 19 and discharge it into a branched channel 42, one branch of which is connected to cylinder 40. Liquid discharged by pump P2 in excess of requirements is exhausted through a low pressure relief valve 43 which enables pump P2 to maintain a constant low pressure in channel 42 and cylinder 40. For the purpose of illustration, pump P2 has been shown separate from pump P1 but in practice it is driven in unison with pump P1 and arranged within the casing thereof as is customary.

Slide block 38 is adapted to be moved toward zero displacement position by a hydraulic servo-motor shown as comprising a cylinder 44, which is carried by casing 39, and a piston 45 which is fitted in cylinder 44 and engages or is fixed to slide block 38. Movement of slide block 38 toward maximum displacement position is limited by a suitable stop shown as being an adjusting screw 46 which is threaded through the head of cylinder 44 and is normally engaged by piston 45. Adjustment of screw 46 determines the maximum displacement of pump -P1.

Liquid for operating servo-motor 44-45 is supplied thereto underthe control of a control valve 50 having its mechanism arranged within a casing 51. In practice, valve 50 is quite small and casing 51 is attached directly to pump casing 39 but for the purpose of illustration valve 50 has been shown separated from casing 39 and on a greatly enlarged scale Casing '51 has formed therein an axial bore 52 which is connected to the discharge side of pump P1 by a channel 53, an annular groove or port 54 which is formed in the wall of bore 52 and is connected to cylinder 44 by a channel 55 having a choke 56 arranged thereinto limit the rate at which liquid can flow into cylinder 44, and a counterbore 57 which is larger than and concentric with bore 52 and is closed at its upper end by a cover plate 58.

Flow of liquid into and out of cylinder 44 is controlled by a valve member consisting of a valve element 59, which is closely fitted in bore 52 and has at least one notch 60 formed in its lower end, and a piston 61 which is fixed to element 59 and is closely fitted in counterbore 57. Any pressure created by pump P1 will extend through channel 53 into bore 52 and tend to move valve member 59-61 toward the left against the resistance of a spring 62 arranged between piston 61 and a piston 63 which is closely fitted in counterbore 57 and provides between its upper face and the lower face of cover plate 58 a pressure chamber 64 to which the liquid under pressure is supplied as will presently be explained.

The force exerted by spring 62 is initially regulated by an adjusting screw 65 which is threaded through cover plate 58 and engages piston 63 until the force exerted by the liquid in chamber 64 exceeds the force with which spring -62urges piston 63 against screw 65 and then piston 63 will further compress spring 62 and the pressure required to raise valve member 59-61 will be proportional to thepressure in chamber 64.

In order that liquid may escape from cylinder 44 when the control valve is closed, the space between pistons 76 1 and 63 ,isflconnected to a drain and piston 61 is urn a provided in its upper edge with a plurality of small tapered grooves or slots 66 which communicate when the valve is closed with an annular groove or port 67 which is formed in the wall of counterbore 57 and is connected to cylinder 44 by a channel 68. p

. The parts preferably are so constructed that the vertical distance between slots 60 and 66 is exactly equal to the vertical distance between the lower edge of port 54 and the upper edge of port 67. When the pressure created by pump P1 has reached a predetermined value as determined by the resistance of spring 62 or by the pressure in chamber 64, it will have moved valve member 5961 towardthe left until the bottom of slot 60 is even with the lower edge of port 54 and the bottoms of slots 66 are even with the upper edge of port 67 so that there isno flow of liquid either into or out of cylinder 44. 1

Then a slight increase in pump pressure will cause valve member 59-61 to move farther toward the left and permit liquid to flow from channel 53 through bore 52, slot 60, port 54 and channel 55 into cylinder 44 and cause piston 45 to shift slide block 38 toward the right to reduce pump displacement until pump P1 is discharging just enough liquid to maintain pump pressure at a predetermined value. Conversely, a slight drop in pump pressure permits spring 62 or the pressure in chamber 64 to move valve member 59-61 toward theright to partly uncover port 67 so that liquid can escape from cylinder 44 through channel 68, port 67 and counterbore 57 to drain, thereby permitting servo-motor 4041 to move slide block 38 toward the left to increase pump displacement until pump P1 is discharging enough liquid to maintain pump pressure at the predetermined value.

Liquid is supplied to pressure chamber 64 from pump P2 under the control of a valve 72 comprising a valve body 73 having an axial bore 74 and two annular grooves or ports 75 and 76 formed in the wall of the bore, a valve member 77 fitted in bore 74 and a spring 78 which urges valve member 77 to a position in which chamber 64 is connected to drain. Chamber 64 is connected by a channel 79 to bore 74 at a point between port 75, which has a branch of channel 42 connected thereto, and port 76 which communicates with an exhaust channel 80 which discharges into reservoir 19.

With valve member 77 in the position shown, it would appear from the drawing that all of the liquid in chamber 64 and channel 79 could escape into reservoir 19 but, preferably, means are provided to prevent the liquid from escaping such as by arranging valve 72 at least as high as valve 50 or by inserting a low pressure resistance valve in channel 80.

When valve member 77 is shifted toward the left, liquid from channel 42 will flow through valve 72 and channel 79 into chamber 64 and will cause piston 63 to move toward the right and compress spring 62, thereby enabling pump P1 to create a pressure proportional to the resistance of relief valve 43. Valve member 77 may be shifted toward the left in any suitable manner such as by means of a solenoid 81 which is connected to the stem of valve member 77.

Operation Before an extruding cycle is started, pump P1 is running and is discharging liquid through channels 18 and 32, valve and channels 33 and 22 into reservoir 19 at a maximum rate as determined by the adjustment of screw 46. Then closing valve 25 will divert the liquid through channel 18v to motors M1 and M1 and cause them to rotate shafts 11 and 11 and sprocket wheels 12 and 12 The liquid discharged by motors M1 and M1 will flow through valves V1 and V1 and channel 22 to reservoir 19.

' Pump P1 will at first attempt to deliver liquid to the motors at a maximum rate but valves V1 and V1 limit the rate at which liquid can flow therethrough, thereby causing pump pressure to rise and liquid to ilow from block 38 toward the right and thereby reduce the displacement of pump P1 until it is delivering just enough liquid to maintain constant the pressure determined by the adjustment of screw 65. I

As the pump displacement decreases, spring 62 will move valve element 59 toward the right and, when the pump is delivering just enough liquid to maintain the predetermined pressure constant, the left end of notch 60 will be in alignment with the edge of port 54 and the bottoms of the slots 60 in piston 61 will be in alignment with the left hand edge of port 67 so that liquid is trapped in cylinder 44 and holds slide block 38 stationary.

The rotation of sprocket wheels 12 and 12 causes chains 15 and 15 to travel therearound and around sprocket wheels 16 and 16 respectively, and the upper reaches of the chains to travel away from die 3. The speeds of motors M1 and M1 are determined by the adjustment of valves V1 and V1 which are so adjusted that the linear speeds of chains 15 and 15 are slightly greater than the maximum speeds at which extrusions 7 emerge from die 3.

The extrusion press at first causes extrusions 7 to emerge at a slow speed. After each extrusion has emerged a short distance, an attendant grasps the end of it with a vise-grip plier 4 (Fig. 6) having a hook 85 pivotally connected thereto and he then inserts the hook through one of the slots 10 or 10 in top plate 9 and into engagement with the chain 15 or 15* underneath that slot as indicated in Fig. 6. Hook 85 is slideable freely in the slot and it is wide enough to keep the plier substantially parallel to the slot. As soon as hook 85 engages the chain, the motor driving that chain is slowed down because valve 50 is so adjusted that the pressure created by pump P1 is just sufficient to enable the motor to maintain a predetermined tension upon the extrusion, such as a pull of 30 pounds. Slowing down the motor results in pump P1 tending to deliver more liquid than is required to drive the motors but valve 50 will function in the above described manner to reduce pump displacement until the liquid discharged by pump P1 is just sufficient to drive the motors.

When all of the extrusions have been connected to the chains, the press is speeded up and the metal isextruded through die 3 at a maximum rate. Increasing the extruding rate causes a momentary drop in pump pressure which enables spring 62 to move valve element 59--61 toward the right and liquid to escape from cylinder 44, thereby enabling servo-motor 40-41 to move slide block 38 toward the left to increase the delivery rate of pump P1 and piston 45 to eject liquid from cylinder 44 through channel 68, port 67, slot 66 and counterbore 57 to exhaust. As soon as pump P1 is delivering enough liquid to maintain the predetermined pressure constant, valve 50 will operate in the above described manner to stop further movement of slide block 38.

When the extrusions reach the desired lengths or when billet 2 is nearly exhausted, the press is stopped which causes extrusions 7 to stop emerging from die 3. Then die 3 is moved a short distance away from container 1 and stopped and immediately thereafter shear 6 is advanced and cuts extrusions 7 from the remainder of billet 2. Stopping the extrusions causes the motors to stall and pump pressure to rise, moving die 3 away from container 1 causes pump pressure to drop and stopping die 3 causes the motors to stall and pump pressure to rise but control valve 50 responds to the change in pressure and efiects in the above described manner the necessary variations in the displacement of pump P1 to enable it to maintain the pressure substantially constant and thereby enable the motors to maintain constant tension upon the extrusions.

After extrusions 7 have been sheared from the remainder of billet 2, valve 72 is shifted to connect pressure chamber 64 in valve 50 to pressure channel 42. .Then the pressure created by pump P2 will act upon pisa, greater pressure than is necessary to enable the motor to strip the extrusions from the die.

FIGS. 7 AND 8 The tensioning apparatus shown in these figures differs from the apparatus shown in Figs. 1-6 only in that it is adapted to maintain tension on five extrusions at the same time. Therefore, corresponding parts have been indicated by corresponding reference numerals but with different exponents added to the reference numerals applied to Figs. 7 and 8.

' As shown, the apparatus includes an elongated table comprising a stationary frame 8 and a top plate 9 which is fixed to the top of frame 8' and has five slots 10 10,- 10 10 and 10 extending therethrough for the greater part of its length. Frame 8 has five shafts 11 11, 11 li and 11 journaled therein near its left end and connected through reduction gears G1 G1 G1 G1", and G1 to hydraulic motors Ml- M1, Ml Ml and Ml respectively. In order that an attendant may approach close to plate 9 when removing extrusions of maximum length from the table, motor M1 may be arranged inside of frame 8 as shown.

Shafts 11 and 11 have two sprocket wheels 12 and 12 fixed thereon directly beneath slots 10* and 10, respectively. Shafts 11 11 and I1 have three sprocket wheels 12 12 and 12 fixed thereon directly beneath slots 10 10 and 10, respectively. Sprocket wheels 12 12", 12 12*, and El are connected by five endless chains 15 15, 15 15*, and 15 respectively, to five idler sprocket wheels 16 16, 16 16, and 16 which are journaled upon a shaft 7 carried by frame 8 near the right end thereof.

Each of motors M1 M1 Ml M1 and M1 has a branch of pressure channel 18 (Fig. 1) and a branch of exhaust channel 22 connected thereto, and a flow control valve similar to valve VI (Fig. 1) is connected in series with each motor. The tensioning apparatus shown in Figs. 7 and 8 functions in exactly the same manner as the apparatus shown in Figs. 1-6 but it is capable of maintaining equal tension upon five extrusions simultaneously as they emerge from a die, and it is also capable of stripping the extrusions from the die at the end of the extruding operation as previously explained.

FIG. 9

This figure illustrates how the sprocket and chains of a tensioning apparatus, such as that shown in Figs. 7 and 8, may be arranged above an extrusion press which has been represented by a container 1 to receive the material to be extruded, a die 3 a ram and a shear 6 The press has an elongated table 89 arranged in front of and below die 3 as is customary.

The tensioning apparatus includes a frame 8 which is connected at its right end to the frame of the press (not shown) by a support 90 and it is connected at its left endto table 89 by a support 91. Frame 8 has attached to its lower face a plate 9 having as many elongated slots (not shown) therein as there are holes in die 3 and it carries as many chains and the drives therefor as there are holes in die 3 with the lower reach of each chain directly above one of the slots in plate 9;

- For the purpose of illustration, the mechanism carried 8 by plate 9 has been indicated as being the same as that which is carried by frame 8 but is reversed in respect thereto. Therefore, such parts as appear in- Fig. 9 have been indicated by the same reference numerals as the corresponding parts shown in the mechanism shown in Fig. 7 so that further description thereof is unnecessary.

The tensioning apparatus operates in the previously described manner but after a plier 84 (Fig. 6) has been clamped on an extrusion, the hook 85 is inserted through a slot in plate 9 and engaged with the lower reach of the chain in alignment with that slot. Arranging the pulling mechanism above the die is of particular advantage when a maximum number of extrusions having very small cross-sectional areas are extruded simultaneously be cause, when the pulling mechanism is arranged below the die and there are slots in the top plate of the table, there is danger that some extrusions might be marred by coming in contact with the corners formed on the plate by the slots since it is impossible to keep the corners coated with the composition, but with the pulling mechanism arranged above the die there are slots in the top of the table 89 and, therefore,- there is no danger of the small extrusions being marred by the corners formed by the slots.

The tensioning apparatus described herein may be modified in various ways without departing from the scope of the invention which is hereby claimed as follows:

1. In combination with an extrusion press including a die having a plurality of holes through which a billet of material is pushed to' emerge in a plurality of extrusions at lineal rates that tend todiifer from one another, tensioning means comprising ahydraulic pump,- a plurality of hydraulic motors, means connecting said hydraulic motors hydraulically in parallel with each other and with said pump, valve means connected in series with each of said hydraulic motors to limit the maximum rate of fluid flow therethrough for limiting the maximum speeds of said hydraulic motors to a value greater than the corre sp'ondingrate said extrusions emerge from said die, a plurality of driven members each operatively connected to a shaft of a different one of said hydraulic motors, and means attaching said driven members to diiie'rent said extrusions so that said apparatus applies and maintains an equal pull on each of said extrusions.=

2. Apparatus for use with an extrusion press having a die with a plurality of holes through which a mass of material is' pushed to emerge in a plurality of extrusions at lineal rates' that may differ from one another, said apparatus comprising a variable delivery hydraulic pump including regulating means for maintaining pump discharge at a predetermined pressure; a plurality of hydraulic motors connected hydraulically in parallel with each other and in common to said pump, now control valves each connected in series with a different said motor to limit the maximum speed thereof fo a predetermined value, individual pairs of driven and idler sprockets each engaged by a continuous chain, and separate detachable means adapted for independent attachment to each said chain and to each said extrusion for separate movement therewith so that said apparatus maintains each said extrusion at a tension equal to the tension on each other said extrusion.

3. In combination with an extrusion press including a die having a plurality of holes through which a billet of material is forced under pressure to emerge from a front face of the die in a plurality of extrusions corresponding to said holes and at lineal rates that are not uniform, a variable delivery hydraulic pump selectively operable at relatively low and high output pressures, a plurality of hydraulic m'otors connected in parallel with each other and with said pump, valve means connected in series with each said hydraulic motor to limit the rate of fluid flow therethr'oug'h, a plurality of mechanical devices each coupled independently to difie'rent said hydraulic motors and including clamping members each adapted for attachment to a corresponding one of said extrusions; whereby, when said pump operates at said low output pressure said motors maintain each of said extrusions at equal tension insufl'icient to pull the material through said die; a shear device for shearing remaining said billet material from the back face of said die at the end of a press cycle for said extrusion press, and manually operable control means causing said pump to operate at said high pressure after said shearing has taken place so that said hydraulic motors strip said extrusions from the die.

4. Apparatus for use with an extrusion press having a die with a plurality of holes through which a mass of material is pushed and emerges from a front face of the die in a plurality of extrusions at lineal rates that may difier from one another, said apparatus comprising a variable delivery hydraulic ptnnp, a plurality of hydraulic motors connected hydraulically in parallel with said pump, valve means connected in series with each said hydraulic motor to limit the rate of flow of fluid therethrough for limiting the speed of said motors to a predetermined value, a movable means operatively connected to each said hydraulic motor for movement thereby in a direction away from said die at a speed tending to exceed the speed of movement of said extrusions, means attaching each said movable means to different said extrusions, said hydraulic pump having a displacement varying member shiftable to vary the stroke of said pump, means continuously urging said displacement member in a direction to increase pump stroke, a servo motor operative to urge said displacement member in an opposite direction to decrease pump stroke, a control valve operatively connecting said servo motor to the outlet of said pump to limit the stroke of said pump and maintain said pump pressure at a first predetermined value sufiicient to cause said hydraulic motors to maintain each of said extrusions at equal tension that is not sufficient to pull said extrusions from said die, a solenoid valve hydraulically connected to said control valve and operative to supply fluid under pressure thereto in opposition to the outlet pres- 4 sure of said pump to increase the stroke of said pump for raising the outlet pressure of said pump above said predetermined value to thereby give said hydraulic motors suflicient torque to pull said extrusions from said die; whereby, said apparatus is selectively operable to tension said extrusions as they are formed and to pull said extrusions from the die in a stripping operation at the end of an extrusion cycle.

5. Apparatus for use with an extrusion press in which a mass of material is pushed through a pair of holes in a die and forms a pair of extrusions that emerge from the die at different lineal rates, means for maintaining a predetermined tension on each of said extrusions, said tensioning means comprising a variable delivery hydraulic pump, a pair of hydraulic motors, means connecting said hydraulic motors in parallel with each other and in common with said pumps, a first continuous chain and sprocket means coupled to one of said motors, a second continuous chain and sprocket means coupled to a second one of said motors, a first detachable means connecting said first chain to one of said extrusions for movement therewith away from said die, a second detachable means connecting said second chain to the other of said extrusions for movement therewith away from said die, and means regulating said pump to supply fluid to said motors at a predetermined pressure sufficient for applying said predetermined tension to said extrusions and not suflicient for pulling said extrusions through or from said die.

References Cited in the file of this patent UNITED STATES PATENTS 644,919 Illingworth Mar. 6, 1900 2,056,896 Douglas Oct. 6, 1936 2,074,068 Ferris Mar. 16, 1937 2,080,810 Douglas May 18, 1937 2,332,069 Gettig Oct. 19, 1943 2,720,310 Yack et a1 Oct. 11, 1955 FOREIGN PATENTS 159,973 Australia Nov. 25, 1954 284,085 Great Britain Jan. 26, 1928 192,471 Germany Dec. 2, 1907

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