US2753994A - Method and an apparatus for extruding metal sections - Google Patents

Description

July 10, 1956 A. c. BRIDGE METHOD AND AN APPARATUS FOR EXTRUDING METAL sscnous Filed Feb. 26, 1951 5 Sheets-Sheet 1 1 1| mun y 10, 1956 A. c. BRIDGE 2,753,994

METHOD AND AN APPARATUS FOR EXTRUDING METAL SECTIONS Filed Feb. 26, 1951 5 Sheets-Sheet 2 M1 422 aim/b 5 6 0,-

July 10, 1956 A, c BRlDGE 2,753,994

METHOD AND AN APPARATUS FOR EXTRUDING METAL SECTIONS Filed Feb- 26. 1951 5 Sheets-Sheet s M7: gril /J64 MAM a 5 172 22% .P W

A. C. BRIDGE July 10, 1956 METHOD AND AN APPARATUS FOR EXTRUDING METAL SECTIONS Filed Feb. 26, 1951 5 Sheets-Sheet 4 MW; zw/QMJ lm/ fir; b I

A. c. BRIDGE 2,753,994

5 Sheets-Sheet 5 MW 1 I M MW at 1 i; W, n /d & m. o 11 u .n m A w July 10, 1956 METHOD AND AN APPARATUS FOR EXTRUDING METAL SECTIONS Filed Feb. 26, 1951 Unite States Patent METHOD AND AN APPARATUS FOR EXTRUDlNG METAL SECTIONS Archibald Claude Bridge, Gamston, England, assignor,

mesne assignments, pany, Wilmington,

y to Anglo-American Extrusion Com- Del., a corporation of Delaware 8 Claims. (Cl. 2072) This invention relates to a method and apparatus for extruding metal sections, which sections may be either solid or hollow, the extrusion being performed by a cold percussion method.

Cold percussion extrusion as the present time is generally performed by a process known as the Hooker process. In this process when extruding, for example, a metal tube, there is used a die which is recessed within a chamber which is adapted to receive and position a metal sing with respect to the die.

A pressure operated punch is provided to work in the chamber, the punch being so dimensioned with respect to the die as to leave the required extrusion area. On operation of the punch, the slug is formed into an extruded section, but leaves within the chamber a metal discard, i. e. an unextruded disc-like portion of metal, which on withdrawal of the punch from the chamber, remains as a facing to the die within the chamber. It will, of course, be appreciated that before any further extrusion can occur, the discard must be removed.

The punch, which has completed its reverse stroke, is swung transversely to the axis of its normal working stroke, by a cross-head mechanism, which sirnnltaneously swings an extractor into alignment with the chamber. The next forward stroke of the main operating mechanism causes a forward stroke of the punch to pick up another slug of metal and also a forward stroke of the extractor to grip the discard within the chamber; the reverse stroke allows the discard to be withdrawn from the chamber and returns the punch to its initial position, the cross-head mechanism swinging the punch into alignment with the chamber and the extractor out of the path of the punch to a position in which the discard may be severed from the extractor, for example by a stripper plate. The cycle of operations can then be repeated.

It will be apparent that in this Hooker process extrusion occurs only on every alternate working stroke of the punch; moreover, as is well known, cold percussion extrusion can only occur if the metal slug is struck by the punch at the correct speed of attack and, due to the high pressures at which it is necessary to work, to obtain satisfactory operation, the punch must operate at high speed and great power. These factors entail the use of a large solid mass for the die chamber and bed of the machine, and necessitate the use of a massive crosshead mechanism, the movements of which must, of necessity, be accurate to within very fine limits, in order to obtain correct alignment of the punch and extractor with the die. of the cross-head mechanism cannot be high and this, in turn, limits the number of working strokes per minute of the machine, and restricts the length of extruded section per stroke. It is found in practice that the length and cross sectional area which can be extruded by this known Hooker process, is limited, due to the fact that when great lengths and large cross sectional areas are required, the cross-head mechanism and die sets would have to be of such massive construction to resist the high commonly practised at It is clear, therefore, that the speed of operation 2,753,994 Patented July 10, 1956 extrusion pressures involved, that they could not be satisfactorily articulated at the speeds required to perform the percussion extrusion. All these several factors provide limitations for the successful operation of the Hooker process.

In the method of cold percussion extrusion according to the present invention extrusion occurs through a die in such a way that the discard is formed on the operative face of the die, which face is clear of obstruction, to allow, during the return stroke of the ram, the discard to be severed and removed, whereby for each working stroke of the ram a section is extruded.

The apparatus for carrying out the above method comprises a ram, a die mounted so as to project from a machine bed or frame, thus providing an operative face clear of any obstruction, means for maintaining a slug of metal to be extruded in operative position with respect to the ram and die, and means for driving the ram towards and away from the die.

The slug may be cold at the inception of the extrusion operation and may be maintained in desired position either by mechanical gripping means, such as fingers, which hold the slug over the exposed surface of the die or a recess may be formed in the operative face of the ram, which may be adapted to reciprocate in a vertical or horizontal plane, the recess forming a slug receiving chamber. When the section to be extruded is a hollow section, the slug receiving chamber may be provided with a mandrel or pilot on which the slug is positioned.

Means such as a guillotine knife is provided for severing the discard from the exposed face of the die, when the ram is on its reverse stroke.

The main drive shaft is arranged to operate the ram and indirectly a feed mechanism for feeding slugs to the operative position and preferably through a suitable cam shaft drives a pump, compressor or valve for supplying air under pressure to actuate the slug feed mechanism.

When carrying out the method according to this invention it has been found that sections of as much as 8 to 10 feet in length can be extruded whether the sections be solid or hollow. This factor has disclosed that during extrusion of long lengths of thin-walled section, a certain amount of distortion occurs and the resultant extrusions are never perfectly straight; it has been found to be impossible to straighten such sections at a later stage, due to the high degree of cold working effect and subsequent low elongation value that is characteristic of extrusions made by the percussion method. It is, therefore, desirable that extruded sections be straightened substantially at the time the extrusion is completed and is therefore still ductile, due to the heat developed during the extrusion process.

According to a further feature of this invention therefore when the section is extruded and passes clear of the die, and whilst it is still comparatively ductile, it is subjected to a straightening force applied parallel to the axis of extrusion whereby any bending or twisting of the section is corrected, so that, when the section is severed from the discard, it is straight.

In order to carry into effect this further step in the method, a mechanical grab is provided which, as the ram approaches dead-centre and extrusion is completed, grips the extruded section and immediately thereafter is moved away from the die in a direction parallel with the movement of the extruded section, so that any bends or twists .in the extruded section are straightened before the exextruded, the current of air moving in the same direction as'that in which the metal was extruded. The cooling of a wavy, 'crooked' or distorted extruded section while still heated as a result of having been extruded, causes the section to contract; and because of the sections being held at its opposite ends respectively in thedieand by the grab, the contraction has a straightening eifect on the section. The straightening elfect thus produced supplements the straightening effect caused by moving the mechanical grab away from the die. Such flow of air, as well as assisting'in the straightening of 'the section, also assiststhe cooling and removal of the section from the machine. It is desirable that the grab should operate almost simultaneously with the ending of the extrusion and the elongation or stretching of the section be concluded before the discard is severed and while the nonextruded discard part is held in contact with the working face of the die, so that the whole cycle will have been completed before the temperature of the section has fallen below'the desiredpoint, that is to saythetemperature at which the section ceases to be ductile.

"The grab may be operated by compressed air, the supply of which is controlled by the said cam shaft.

The invention is illustrated in the accompanying .drawings in which Figure 1 is a plan view and Figure 2 a-sec-. tional elevation on the line 22 Figure 1; Figure 3 is a side elevation of the straightening mechanism, Figure 4 being a plan of Figure 3. Figure 5 is a detail view to a larger scale of the slug feeding mechanism. Figures 6 and 7' show respectively in side elevation and plan and greater detail the grab mechanism shown in Figures 3 and 4, whilst Figures8 and 9 are diagrammatic views showing a slug in position for extrusion and the extruded section formed fromthe slug, respectively.

-With reference to the drawings, the machine illustrated and now to be described is suitable for the extrusion 'of metal tubing. It will, of course, be appreciated that, by varying the shape and dimensions of the die, hollow sections other than tubing can be extruded, and also solid sections canbe extruded.

Referring more particularly to Figures 1 to 4, the machine comprises a press frame 1 in which is mounted a ram 2 which is caused to reciprocate through toggles 3 actuated through eccentric rods 4 and gear wheels 5 driven through the main shaft 6 of a motor 7. The face of the ram is recessed to form a container having a slug receiving "chamber 8 in which is arranged a pilot 9 Mounted 'on a die holder 10 so as to project from-the press frame 1 is an apertured'die' 10 and as will be seen more particularly from Figure 1, the operating or work-. ing face of the die is left clear of any obstruction. The ram Z-and die 10 are so dimensioned Withrespect to one another that the die is a sliding fit within the slug receiving chamber 8, the ram and die cooperating to form an effective seal around the slug. A lever 11 pivotally; mounted as at 12 on the frame 1 is coupled atone end by links 13 to one of the toggles 3. At the other end the lever is pivoted to a member 14 which carries a knife or guillotine 15 which, as will be describedin greater detail below, is provided for severing a discard from an extruded section. A cam shaft 16 is provided, which is driven through the' drive shaft 6, as for example by means 'of bevel gears (not shown), which cam shaft carries a cam 17 formed with a cam track 18 in which rides a roller 19 carried by a slide 19a which is pinned by pin. 1% to a slug feeding member 20, which, at one end, is forkedto receive a slug and has-pivoted thereon afinger 20abia'ssed into slug gripping position asshown'in Fig-.. ure 5 by a spring 20b. The feeding member 20 is mounted by a transverse pin 21a on a part 21 (see Figure 5)., itself pivoted on the machine frame. The said feeding member 20 carries a roller 22v which cooperates with a face cam 23 andalso carries a projection 24 engaging in a slotted guide gate 25.

The said member 20 is, as shown in Figure 5,..i11.- a:

position in which the finger 20a is embracing and gripping a slug 26 and holding it in position in front .of the die 105 when the cam shaft 16 is driven the feeding member 20 is rocked about the pivotal axis of the part 21 so as to be brought into a position to receive another slug 26 from a loading slide or magazine 27. The slugs are normally prevented from falling out of the slide '27 byrquadrants 28, which can be moved out of the path of the slugs by means of rods 29 actuated through a piston 30 working in a cylinder 31, the piston being operated by compressed air, as will be described later. When the quadrants are moved out of the path of the slugs, a slug will fall onto a receiving plate 32 which is normallymaintained'beneath the slide 27 by a spring 33 .The plate-is adapted to bemoved against the action ofits' spring by the feeding means 20 when this is swung over to receive a slug.

The member 29 can also be moved in a plane at right angles to that previously described, about the transverse pin 21a carried by the pivot .part 21. This latter movement is effected by the ram 2 during its forward movement, the finger 20a, and that end of the feeding member to which the finger is pivoted, passing over and embracing the die. The feedingmember 20 is brought back again on the reverse movement of the ram by means of the roller 22 riding over the face cam 23.

It will be observed from Figure 5 that the feed member 20eat its lower end has been broken away so that the roller 22 is not in-engagcment with the face cam 23 but this has been done to clarify the drawing.

-It has been found that when sections of some considerable length, which may be from 8 to 10 feet or more, are extruded,- and the extrusion is of a thin-walled section, a certain amount of distortion occurs, and the resultant extrusions are never perfectly straight: it has been found sometimes to be impossible satisfactorily to straighten such sections at a later stage, due to the high degree of cold-working effect and subsequent low elongation value that is characteristic of extrusions made by the percussion method: furthermore, although once a section has been extruded, as described above, the section can-still be termed ductile, in that it can be bent, ithas been found that when the section has reached its normal'state, that is to say is at atmospheric temperature, the ductility is so low that it is impossible satisfactorilyvto straighten the section. It is, therefore, desirable that extruded sections be straightened substantially-at the time the extrusion is completed and therefore still is at an elevated temperature and has a high or flow ductility due to the heat developed during the extrusion process.

.In order to enable the straightening of the section to occur, mechanism as shown in Figures 3 and 4, and in greater detail in Figures 6 and 7, is provided. The mechanism-.-includes a grab 34, forming part of a piston and piston rod 35, working in a cylinder 36, the piston and piston rod assembly being actuated by air under pressure whichis provided from the same source as that which w operates the rods 2.9 of the slug magazine. Mounted between the cylinder 36 and the point of extrusion, on a bracket 37, is a further air cylinder 38, whose piston rod assembly 39 is coupled to toggles 40, 41. The toggle 40, at its free end, is pivoted to a bracket 42,

'- which carries the grab cylinder 36, the toggle 41 being pivotally anchored to a lug 43 on a frame 44. The bracket 42 is capable of sliding, on operation of the toggles, in a slide :45, so that the toggles 40,41 can straighten when the piston assembly 39 is moved downwardly as shown in Figure 6. The grab 34 is formed in two parts,

one :part- 34-being carried by the piston rod assembly 35.and the. other 34a being carried by the bracket 42.

As shown more particularly in Figure 4, a selector valve mechanism -46 (of known construction) is 'providedsfor supplying air under pressure to the various parts which are thereby operated, and the frame 1*is apertured behind the die to allow of extension therethrough, from the die, of an extrusion guide 47 aligned with the die and on its exit side. As is shown again in Figure 4, a pipe 48 leads from the compressed air control mechanism 46 to the guide 47 for supplying compressed air for assisting, as will be described below, in extraction of the extruded section. The cam shaft 16 enters the selector valve mechanism 46 to ensure correct timing of the supply of compressed air to the members to be actuated thereby.

Before describing the actual operation of the machine, in the diagrammatic Figures 8 and 9 there is shown a slug 26 in position on the unobstructed die Working face (Figure 8) before extrusion, the slug being held in position by the finger 20a of the feeding member 20. As shown in Figure 9 the slug has been surrounded by the container and has been impacted by the ram 2, which is now on its return stroke, and the slug has been extruded in the form of a tubular section through the die and extrusion guide 47. The ram stroke is such that a discard 49 is left on the unobstructed face of the die and engages the ram facially and engages the container peripherally. Whilst the extruded section is being straightened and cooled, the discard is severed by the guillotine 15. As will be seen in Figure the slug 26 is provided with an aperture 26a of such dimensions as to be a reasonable sliding fit on the pilot 9.

The apparatus functions in the following manner: A metal slug 26 is introduced between the ram 8 and the apertured die 10 so as to be under confinement, requiring flow of the metal through the die. Assuming the parts to be in the position shown in Figure 2, the drive is such that the toggles 3 tend to straighten, thus moving the ram 2 towards the die for extrusion. As the ram moves forward the guillotine is raised due to the lever 11 pivoting about its pivot 12. As the slug receiving chamber 8 and pilot 9 contact the slug 26, the ram 2 pushes the upper end of the feeding member forward about its pivot 21a and, as the ram gets to the end of its forward travel, extrusion occurs to form an elongated extruded section free of tension during the extrusion operation.

On reverse movement of the ram, the feeding member 20 is brought back to the position shown in Figure 2 by the roller 22 riding over the face cam 23. At the same time the lever 11 through the member 14 forces the guillotine downwardly to sever the discard still united to and forming part of the extrusion and remaining before the die, that is on the unobstructed face of the die. The cam shaft 16, during this latter movement and substantially at the conclusion of the extrusion operation, operates the selector valve mechanism 46 to supply compressed air to the grab cylinder 36 so that the grab 34, 34a momentarily grasps and holds the fore end of the extruded section while the trailing end of the section is held in the die and the section lies generally along the line of extrusion. The selector valve mechanism 46 also supplies compressed air to the stretching cylinder 38 operating its piston 39 to extend the toggles 40, 41, thereby imparting a stretching effect to the extruded section axially thereof while both ends of the section are held against movement towards each other. At the same time air under pressure is supplied through the pipe 48 to force air along and in contact with the extruded section in the direction of extrusion, which air urges the extruded section away from the die in the direction of extrusion and assists in the removal of the extruded section and at the same time cools the section. Finally, the extruded and straightened product is released and removed in its straightened condition.

As the ram proceeds to the end of its rearward travel the roller 19 rides in the cam track 18 to rock the feed ing member 20 towards the left (Figure 5) so that it moves to receive a further slug simultaneously. The compressed air from the selector valve mechanism is admitted to the cylinder 31 to actuate the rods 29 to move the quadrants 28 out of the path of the lowermost slug 26 in the slide 27, so that the lowermost slug drops onto the receiving plate 32 which is pushed towards the left by the feeding member 20 against the spring 33, the slug then rolling oif the plate 32 into position in the feeding member 20. The finger 20a is pivoted at 200 against the action of its spring 20b by a stop 27a on the magazine 27 to allow the slug to drop into position, the finger 20a returning to its gripping position shown in Figure 5 as the feeding member 20 is swung back again to approach the die.

It is a well known fact that successful cold percussion extrusion depends mainly upon the co-relation of the pressure applied by the ram and the speed of impact of the ram with the slug. As an example of cold percussion extrusion according to this invention an aluminium slug having an outside diameter of 1% inch, and a length of up to 2 inches can be used, and with a ram the impact speed of which is 10 to 20 inches per second under a pressure of 75 tons per square inch, the pressure will produce pure aluminium tube nearly 10 feet in length, having an outside diameter of .415 inch, and inside diameter of .375 inch.

It will be appreciated that the co-relation of the pressure and the speed of impact of the ram may vary according to the size of the slug and the shape and crosssection of the extruded section required, as is well-known to those skilled in the art of such extrusion. My method of percussively cold extruding metals and alloys with the ram speeds and pressures co-related to the metal, the size of the slug and the shape and cross section of the extruded section required, and extrusion products producible by that method are disclosed and claimed in my co-pending application Serial No. 551,153, filed December 5, 1955.

With apparatus constructed in accordance with this invention it will be mainly appreciated that there may be only one main moving part, namely the ram, since, when a slug is in extrusion position, the ram commences its working stroke, extrudes the metal through the die, leaving the discard in position on the unobstructed exposed surface of the die, so that during the return movement of the ram the discard is severed and removed, and a 45' further slug is fed to extrusion position, thereby obtaining the great advantage that a section is extruded for every working stroke of the ram.

It has been stated with reference to Figures 4, 6 and 7 that the grabbing and stretching of the extruded section is performed by means of compressed air; it will, of course, be appreciated that instead of compressed air, any fluid or liquid pressure can be employed, or the grab and stretching means can be electrically operated.

I claim:

1. In a method of producing an elongated straight metal section from a cold metal slug, positioning the slug against a die having an unobstructed working face transverse to the direction of extrusion and an extrusion aperture; positioning a container to surround the slug with said slug operatively positioned with respect to said die; forcing a ram against said slug to extrude part of the slug metal through said die aperture to form an extruded section; leaving a non-extruded discard part of the slug engaging said ram facially and said container peripherally while still united to said extruded section and also engaging said unobstructed working face of the die; grasping and holding the extruded section at a point beyond said die in the direction of extrusion therethrough to prevent movement of said discard part and said extruded section oppositely to the direction of extrusionj moving said ram and said container reversely to separate them from said die and discard part while so holding said extruded section; and then transversely severing said discard part from the extruded section.

2. In a method of producing an elongated metal section from a metal slug, intfoducingthe ,slug between a ram and an iape'rtur'ed die under confinement requiring flow. of the metal through the die, driving the ram and die relativ'elyYmWard each other to eXtr-ude'slugmetal through'the die aperture to form an elongatedextruded section'free of tension 'duringthe extrusion. operation, and then substantially'at'the conclusion ofthe extrusion operationgrasping and holdingthe foreend f the extruded section while the trailing end of the. section is held 'inthedieand said sectionlies generally along'the line'of extrusion, :thereupon tensionj-ng said section throughout 'itslength'Whil'e both ends of said section are held against. movement towards each other to straighten the section thereby-to afford the product straightness when released, and finally releasing and removing the completed product in its straightened condition.

3. The method set forthin claim 2 wherein said tensioningof theextruded section is, effected by moving one end of said'section in a direction away from the other'end'of'the section and axially thereof.

'4."The method set forth in claim '2 wherein the extrusi'onoperation is performed percussively upon a cold metal slug to eifect cold Working of the metalwith resultant heating of the metal emerging; from the die to a temperature at which the extruded section has sufficient ductility to enable said. section to be straightened, the 'tensio'ning of said section being elfected while said section is still at said temperature.

' 5." In a method of producing an elongated metal section from a metal slug, introducing the slug between a ram .and an apertured die under confinement requiring flow of slug metal through the die, driving the ram and die 'relatively'toward each other to extrude a .part of the slug metal through the die aperture to form the elongated section free of tension during the extrusion operation and leaving discard metal before the die at the conclusion of the extrusion operation, then substantially at the conclusion of the extrusion operation grasping and holding the fore end of the extruded section while the trailing end of'the section is held in the die by said disca'rd metal and said section lies generally along. the line of extrusion, thereupon tensioning said section throughout, its'length while both ends of said. section are held against movement towards each. other to straighten the.

8 section thereby toafford the product straightnesstwvhen released, and finally releasing and removin g fine 1. completedproduct in its straightened condition.

6. Themethod set for in claim 5 wherein said-Jensioning ofthe extruded sectionis effected by moving one end of, said section in adir'ection away from theother end of thesection and axially'thereof.

7.,Ihe. method set forth in claim 5 wherein the-extrudedsection is-at an elevated temperature, and said tensioning of said section is effected by cooling the section to cause said section to contract while both ends of the section are held against movement towards each other.

8. Apparatus for producingan elongated straight metal section from ametal slug comprising a frame; a die element mountedon said frame; a ram element mounted on said frame; means for driving one of. said elements towards the other of said elements on a-WOrking stroke to extrude slug metal through the die to form. an;.;extruded section; means. for 'tensioning said section'substantially from end-to-end in a straight line whilezthe trailing end thereof'is held in said die at the conclusion of an extrusion operation; and means for operating ,said drivingmeans and said tensioning means in timed relation to cause1the tensioning means to operate after-the working stroke, of, said one of said elements has been performed, to thereby straighten said section.

References Cited in the file of this patent ':UNITED STATES PATENTS 5,253 Cornell Aug. 21,; 1847 1,769,205' Clark July 1, 1930 1,841,396 Benz Jan. 19, 1932 1,924,294 Shirk et al. Aug, 29, 1933 2,176,365 Skinner at al Oct. 17, 1939 2,261,304 Sparks Nov. 4, 194 2,487,972 KatZ NOV. 15, 19 49 2,487,973 Kent NOV. 15, 1949 2,539,564 Barrett Jan. 30, 1951 FOREIGN PATENTS 1,001 Australia July 3, 1931 402,317 Great Britain Nov, 30,- 1933

Claims (1)

1. IN A METHOD OF PRODUCING AN ELONGATED STRAIGHT METAL SECTION FROM A COLD METAL SLUG, POSITIONING THE SLUG AGAINST A DIE HAVING AN UNOBSTRUCTED WORKING FACE TRANSVERSE TO THE DIRECTION OF EXTRUSION AND AN EXTRUSION APERTURE; POSITIONING A CONTAINER TO SURROUND THE SLUG WITH SAID SLUG OPERATIVELY POSITIONED WITH RESPECT TO SAID DIE; FORCING A RAM AGAINST SAID SLUG TO EXTRUDE PART OF THE SLUG METAL THROUGH SAID DIE APERTURE TO FORM AN EXTRUDED SECTION; LEAVING A NON-EXTRUDED DISCARD PART OF THE SLUG ENGAGING SAID RAM FACIALLY AND SAID CONTAINER PERIPHERALLY WHILE STILL UNITED TO SAID EXTRUDED SECTION AND ALSO ENGAGING SAID UNOBSTRUCTED WORKING FACE OF THE DIE; GRASPING AND HOLDING THE EXTRUDED SECTION AT A POINT BEYOND

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