US2656743A - Die mechanism for extruding compressed powder rods - Google Patents

Description

Oct. 27, 1953 2,656,743

DIE MECHANISM FOR EXTRUDING coMPREssEn POWDER Rous E. K. LEAVENWRTH 5 Sheets-Sheet 1 mea Fgb. 2s. 1951 Qct. 27, 1953 E. K. LEAvl-:NwoRTH 2,656,743

DIE MECHANISM FOR EXTRUDING COMPRESSED POWDER RODS Filed Feb. 25. 1951 5 Sheets-Sheet 2 [Tix Oct. 27, 1953 E. K. LEAvENwoRTH 2,656,743

DIE MECHANISM FOR bFx'rRumNc; rCOMPRESSE; POWDER Rous Filed Feb. .25. 1951 5 Sheets-Sheet 3 ltr j I BY l l Oct. 27, 1953 E. K. LEAvENwoRTH DIE!v MECHANISM FOR EXTRUDING COMPRESSED POWDER RODS Filed Feb. 2S. 1951 5 Sheets-Smet',- 4

IN1/mmm Oct. 27, 1953 E. K. LEAVENWORTH 2,556.3'43

DIE'MECHANISM FOR EXTRUDING coMPREssED POWDER Rous ff JNVENTOR BY A Patented Oct. 27, 1953 DIE MECHANISM FOR EXTRUDING COMPRESSED POWDER RODS Edgar K. Leavenworth, Birmingham, Mich., as-

signor to Climax Molybdenum Company, New York, N. Y., a corporation of Delaware Application February 23, 1951, Serial No. 212,434

6 Claims.

This invention relates to die mechanisms for extruding compressed powder rods, and more particularly to mechanisms for forming a continuous rod of compressed powdered metal which is to be sintered prior to melting in an electric furnace.

The die mechanism which is the subject of the present invention is an improvement over that described in applicants copending application No. 787,797, filed November` 24, 1947. In that application, an extrusion die is disclosed having a reciprocating ram or plunger at one end which packs small incremental portions of the powdered material into the die and compresses them at a predetermined consistency. The die is of constant cross-sectional area and is of such a length that the frictional force oi the powdered metal against the walls of the die is always sufficient to prevent axial movement of the rod due to the axial force of the ram. The die is further provided with split portions which are normally held against radial expansion, but which by an arrangement of a cone and springs are released for radial movement upon the attainment of a predetermined axial force, thus reducing the frictional force of the rod in the die suiliciently to allow axial movement of the rod.

This mechanism presents inherent disadvantages which it is the object of the present invention to overcome. The springs which are used to counteract the axial force of the ram are very cumbersome and laborious to load. The die is required to have an axial motion, and bearing problems result due to excessive loads on the cone. Furthermore, the springs and cone operate as a friction brake when the compressed rod is moved through the die, thus causing excessive die wear and wasted power.

It is an object of this invention to eliminate these disadvantages and to provide an improved die mechanism which is extremely flexible in its operation and in which the labor involved in replacing or readjusting the parts is greatly reduced. In particular, it is an object to eliminate the spring arrangement and the attendant vertical motion of the die and compressed rod which is required to operate the cone and springs in the previous structure, substituting instead a mechanism which normally exerts a positive force on the split die portions to prevent their radial expansion, together with tripping means for automatically releasing this force when the axial force exerted by ram reaches a predetermined value. In association with this object, it is within the contemplation of this invention to provide a hydraulic mechanism in the form of a cylinder and piston for exerting the radial clamping forces on the die, and in which the hydraulic pressure in the ram cylinder is used to trigger the release of pressure in the die cylinder, the pressure at which this triggering takes place being adjustable by the operator.

It is a further object to provide an improved hydraulic system for an extrusion die mechanism of the above character, which is fully automatic in its operation and which includes means for varying the die cylinder releasing point without affecting the eiiiciency or speed of the system` Other objects, features, and advantages of the present invention will become apparent from the subsequent description taken in conjunction with the accompanying drawings.

In the drawings:

Figure l is a side elevational view of the upper portion of an electric furnace installation, showing the location of the die mechanism and its associated subassemblies.

Figure 2 is a plan cross-sectional View taken along the line 2-2 of Fig. l and showing the feeding troughs and the die mechanism.

Figure 3 is a cross-sectional View in elevation taken along the line 3-3 of Fig. 2 and showing the die piston and cylinder as well as other elements of the die.

Figure 4 is a fragmentary cross-sectional view taken along the line 4-4 of Fig. 1 and showing the guide for the ram.

Figure 5 is a plan cross-sectional view taken along the line 5-5 of Fig. 3 and showing the 1ocation of the die tension bolts.

Figure 6 is a front elevational View, partly in cross-section along the line 6 5 of Fig. 3 and showing the construction of the entering portion of the die elements.

Figure 7 is a plan cross-sectional view taken along the line 1--1 of Fig. 3 and showing the construction of the die segments and the die collar.

Figure 8 is a plan cross-sectional View taken along the line 8-8 of Fig. 3 and showing the die segment clamping blocks; and

Figure 9 is a schematic view of a preferred hydraulic system for carrying out the principles of operation of this invention.

The principles of this invention are shown as enoodied in a device for producing a continuous rod of sintered metal which is fed to the Crucible or mold of an electric furnace for melting into an ingot or other object. It will be understood 3 however that these principles may as well be applied to other devices and installations where a continuous rod of compressed powder is desired to be formed. In the illustrated embodiment, after the rod leaves the die in its compressed form it passes through a series of electrodes (not shown) where. it is subjected to an electric current which heats the compressed particles sufliciently to sinter them together, thus permitting the rod to continue downwardly toward the furnace and still have sufficient strength to support its own weight. It is of course important to the sintering operation that the density of the material in the rod before sintering have as little variation as possible, so that a uniform electric current will not produce over-sintering in some portions of the rod and under-sintering in others. For this purpose, it is necessary that the amount of powder that forms each increment of the rod be held uniform within reasonable limits, and that the compression Apressure for each increment be substantially the same.

To carry out these purposes, the present invention provides a die mechanism `generally indicated at vII and a ram generally indicated at I2 which reciprocates within the upper or entering portion of the die and upon each reciprocation packs an incremental amount of powdered metal which is fed from a trough I3. Since the mechanism is shown as used in conjunctionwith an electric furnace, the entire assembly is enclosed bya housing I4 which is evacuated through a conduit I5 and is cooled by coils I6. The 'trough I3 may be of Ithe conventional vibratory type, being supported at its outer end by vibratory spring I1, and is fed from `ahopper I8 mounted above the outer end. The inner end of hopper I3 is forked, as shown in Fig. 2, and leads to both outer ends of an elongated funnel I9 surrounding the ram I2 and surmounting the die II. A vibrator 23 may be mounted on the funnel to insure a constant ow of powder. The die itself is preferably suspended by means of a plurality of posts 2I, the lower ends of which hold Aa bedplate 22 upon which the die lis mounted. The ram lI2 is disposed between these posts and comprises a piston 23 extending downwardly ,from vthe ram cylinder 'i9 (shown schematically in Fig. 9) and connected by a split element 24 to the ram proper, -thus facilitating removal kof the parts. As shown in Figs. l and 4, a double armed guide member .25 having oppositely disposed forked ends 26 is secured at the upper end of the ram I2 and slides between two diagonally opposite posts 2|, thus preventing lateral buckling movement of the ram and increasing its columnar strength.

At the top of its stroke, as shown by the dotdash lines in Fig. 3, the reduced portion at the lower end of the ram is disposed within the funnel I9, and the head member 21 is above the upper end of die II. When in this position, powdered `metal will be permitted to flow into entering end of the die and when the ram is lowered, the head member 21 will compress the powder into the die, the final position of the head member being a snug fit within the die as shown Yin solid -lines in Fig. 3.

The die into which the powdered metal is forced by the ram is shown in the illustrated embodiment as having a constant cross-section of vhexagonal shape. However, it willbe understood that other cross-sectional shapes could be'used for the die within the principles of the invention. As is best seen in Figs. 7 and 8, the 'die comprises six elongated segments 28, 29, 3i, 32, 33 and 34 which together form an elongated rod-forming passageway of hexagonal cross-section. In particular, each of these segments has an inner face 35, and outer face 36 and sides 37 which have matching inwardly inclined portions 38. These inwardly inclined portions are normally in fiush relation so that the inner surfaces 35 form the hexagonal passageway. Adjacent the upper end of each of these die segments is an outwardly facing transverse slot 39, and a pair of supporting plates 4I and 42 vare engaged in these slots and support the die segments against axial movement, a certain amount of play being permitted between the plates and die in a radial direction, as shown in Fig. 3. Plates 4I and 42 rest upon the upper surfaces ofthe die segment clamping blocks 43 and 44, which surround the major portion of the die segments below the slots 39 in a manner hereinafter described in detail. A collar 45 is disposed 1 around the die segments above plates 4I and 42,

and extends `to the upper ends of these die segments. The lpurpose of Vcollar 45 is vto positively prevent at all times any relative movement fof the upper portion of the die segments, thus `'crea-ting in eifect an limmovable die at this entering portion. For this purpose, the collar 45 preferably has a press `iit with the outer vfaces 35 -of the `-die segments, so that the matching surfaces 38 of the segments are in tight relation to prevent any powder working in between the segments. The height of collar 45 and thus of the solid portion of the die is such that the cavity found inside the die and above the open splits will `contain the maximum amount of loose powder which is to vbe compressed for any one increment.

The die segment supporting plates 4! and -42 are secured to the die segment clamping block 44 by means of bolts 46, but are movable with relation to block 43. The blocks 43 and 44 extend downwardly from the supporting plates 4i and 42 :substantially along the remaining length of the die segments, and are supported by the bedplate 22. The bedplate has a clearance aperture 47 into which the lower ends of the die segments extend, and which allows the Vdownward passage of the compressed powdered rod from the die. Blocks 43 and 4E each have an interior clampingsurface 48 of such configuration as to simultaneously surround. three of the die segments so as to prevent their routward radial movement. In particular, block 44 engages die segments 28, 29 and 3I while block 43 engages the remaining die segments 32, 33 and 34. The blocks are capable khowever of a releasing movement (block 43 to the left and block 44 to the right relative to the die strips as shown in Figs. 3 and '8) so as to relieve their engaging pressure on their respective die segments, thusreducing the frictional forces on the rod.

To accomplish this action, a die cylinder 49 and a die piston 5I are provided adjacent the blocks and are operatively connected thereto. As is Ybest seen in Figs. 3 and 8, the die cylinder 49 is in spaced relation with block 43 and is so disposed that the cylinder axis is perpendicular to the axis of the die passageway. In the illustrated embodiment, the diameter of cylinder 49 is such vthat it extends substantially the entire length of the die, the lower end of the cylinder side wall being adjacent but not supported by bedplate 22. It will be understood, however that the relative proportions of the die cylinder are not critical but may be varied to suit the installation. The louter end wall 52 of the die cylinder is 'iiared slightly outwardly, and the central portion thereof is -provided with a guideway 53 for slidably supporting an extension 54 of the die piston 5|. The inner end of the die cylinder is provided with a head 55 secured thereto by cap screws, and this head has a central bearing aperture 56 which slidably supports inner extension 51 of the die piston 5|. Extension 51 is of substantially greater diameter than extension 5,4, and has an end face 58 of relatively large area which engages the outer flat face 59 of block 43. An hydraulic pressure connection 6| leads to the outer end wall 52 of the die cylinder, and is connected by axial port 62 and radial ports 63 in extension 54 to the pressure chamber 84 of the die cylinder. Sealing rings 65 and 66 may be provided on the die piston and on extension 51 respectively to prevent oil leakage. The opposite side of die piston 5| is preferably connected by a conduit 61 to a source of vacuum, so that oil leaking in to the chamber 88 will not contaminate the vacuum surrounding the entire pressing mechanism.

While as stated previously die piston 5| is operatively engageable, by means of mating faces 58 and 59, with die segment clamping block 43, the die cylinder 49 is connected to the die segment retaining block 44. For this purpose, a plurality of tension bolts 69 are provided, and these bolts are connected at one end to the die cylinder and at their opposite ends to a bearing plate 1|. As is best seen in Fig. 6, the side wall of the die cylinder is enlarged at four circumferentially spaced points in order to accommodate these bolts, and the bolts in turn are disposed inwardly from the supporting posts 2 I. The tension bolts 89 pass freely through die cylinder head 55, and tubular spacers 12 surround the intermediate portions of the bolts between head 55 and bearing plate 1l. This bearing plate has an inner face 13 which is engageable with the outer face 14 of die segment clamping block 44. Bearing plate 1| also rests upon bedplate 22 and is connected thereto by cap screws 15. Clamping block 44 also is supported by bedplate 22 although not fastened thereto, and retaining block 43, which as will later be described moves relative to the bedplate, is supported thereby through an intermediate wear plate 16. The lost-motion connection of tension bolts 59 to die cylinder 49 and to bearing plate 1| is by means of outer nuts 11, which permit only a tensile stress to be placed in the bolts. A pair of legs 18 are also provided on bedplate 22 to support the weight of die cylinder 49 which however is not fastened to the bedplate.

The operation of the mechanism thus far described may perhaps best be illustrated by a description of the complete cycle of events during the feeding and packing of one increment of powdered metal. Starting from a condition in which the ram 25 is just beginning its upward or return stroke, the parts will be in a position as shown in the solid lines of Figure 3. When in this position, hydraulic pressure will be applied through line 6| to chamber 64, and die piston 5| will be forced toward the inner end of die cylinder 49. This hydraulic pressure will also cause the die cylinder to be forced against nuts 11, thus creating tension in bolts 89 and tending to move bearing plate 1| inwardly. It will thus be seen that the engagement of die piston 5| with retaining block 43 and the engagement of bearing plate 1| with retaining block 44 will force both of these blocks against their corresponding die segments, thus locking the die segments in their closed position as seen in Fig. 8. This will increase the frictional resistance of the compressed rod within the die to such a degree that it may not be forced downwardly by the: action of ram 25. As the ram moves upwardly it will allow powder to ow from funnel I9 into the immovable entrance portion of the die which is surrounded by collar 45.

As the die again moves downwardly in its compression stroke, this powder will be compressed within the immovable die portion so as to form another increment of the compressed rod. During the iirst portion of this packing movement, the die segment portions within blocks 43 and 44 will also remain immovable, thus maintaining the frictional resistance which prevents axial movement cf the rod. However, when a predetermined axial force has been reached, as reflected in the hydraulic pressure within the ram cylinder, the hydraulic pressure within chamber 64 will be abruptly relieved, the means for accomplishing this action being described in detail below.

When the hydraulic pressurewithin chamber 64 is relieved, the inward forces on clamping blocks 43 and 44 will be slackened, thus reducing the frictional resistance of the powdered rod within the die segments. 1t will be understood of course that the actual movements of these parts is very slight, the movement required being only that necessary to relieve the radial pressure on the rod. Since the axial force of the ram may now overcome the frictional forces within the die, the rod will be moved downwardly through the die until the ram again reaches the bottom of its stroke. When this position is reached, the hydraulic pressure within chamber 64 will again be built up to its previous degree, thus imposing the frictional forces upon the rod which lock it against axial movement, and the cycle is repeated. It will be noted that during the releasing movement of blocks 43 and 44, bearing plate 1|, bedplate 22 and die segment supporting plates `4| and 42 all will move in substantial unison with retaining block 44, although the construction will permit such relative movement between block 44 and the bearing plate and bedplate as may occur due to the reduction of internal stresses. On the other hand, die piston 5| and clamping block 43 move independently of the bedplate and the die segment supporting plates, the latter sliding upon the upper surface of clamping block 43. The play in slot 39 will permit relative movement between the supporting plates and the die segments.

The hydraulic system for controlling the events in the cycle of operation is shown schematically in Fig. 9, it being understood of course that systems other than that shown in the illustrated embodiment could be used. The ram cylinder 19 and the ram |2 are shown in the upper right hand portion of the diagram, and the die cylinder 49 and die piston 5| are shown at the central right hand portion. In the diagram, solid lines are used to represent the main hydraulic conduits, and dotted lines are used for the pilot conduits. Pump motor 84 drives three hydraulic pumps 85, 86 and 81 which are designed to deliver hydraulic uid at various rates, the pumps being supplied from a tank 88. Pump which is preferably of a variable delivery type, is used as the main supply pump for the ram cylinder 19, and is connected to a pressure regulating valve 89 by a conduit 9|, valve 89 being adjusted to deliver a relatively high pressure, say 2,000 p. s. i. Valve 89 is connected to a filter 92 by a conduit 93, and the filter is connected to ram cylinder 7 valve 94 by means of conduit .85.. A conduit $6 leads from port 94B., this conduit hai/inge. branch 91 leading through a'r-estriction 98 .to the lupper chamber 99 `of :the 'ram .cylinder by means of conduit .101| Conduit 96 :also .has :a :branch 102 nonnected through ram retarding valve :|03 :and fa conduit |94 to "chamber .99. Valve 1I0-3 always allows free flow .from port 1193A `to port 193B, but shuts orf now kfrom `I503B to 1113A when cam arm |65 vis depressed bycam 10B attached toram 8|, this action occurring during an intermediate portion of the down stroke .Pump 8B is used as an auxiliary pump during the stroke and during .the 'first portion of rthe lclown stroke, and for this purpose is connected to the supply fconduit s3 through pressure :regulating `valve 10.1., check valve |168 and conduit 1119. Valve |01 is set to deliver a relatively low pressure, vsay 500 p. s. i., .so that lcheck valve .|08 will close `if a pressure .higher than this :exists in .supply .con-

duit 93.

.Pump -31 :is used to .supply .hydraulic pressure for the pilot vsystem (shown .in :dotted lines) through .a 'conduit if!! .a pressure :regulating valve I i2 set to deliver at an intermediate pressure, say .1,0% p. s. i. This pump .also supplies hydraulic .pressureto the vdie cylinder di) through a pressure reducing valve H3 set 'at .about 590 p. s.. i., die Vcylinder kvalve lill and .a conduit Bi. Pilot system `supply conduit il IE leads from `valve i l2, and has za branch 1|?! .leading to port IitSP of die cylinder pilot valve |I8 and another.' branch iis leading to `port I2|P `of ram ycylinder pilot valve 12|. .Port :I lfSX is connected by control conduit |22 to conduit tied, a vvariable setting relief valve 123 being inserted in conduit |22 and opening .only when the iluid Jin conduit IM has reached a predetermined pres sure.

The .lower chamber 124 of the ram cylinder is connected by `conduit |215 to port 94A, and this conduit is used both to supply `and to remove the fluid within chamber |124. A control conduit E2G connects conduit |25 Vto port IIBY, so that the position of die cylinder pilot valve Hi8 is controlled by .the pressure differential between conduits Idd and F25. Pilot valve IIil in turn controls the position of .ram lcylinder Valve `Htl by means of conduits I2-7| and |28 leading to ports II-llX and llllY respectively., The pressure differential between .lines Idil and |25, or between the upper and lower ram cylinder chambers, thus in eiiect controls the movement of die piston I.

Ram .cylinder pilot valve 2| is connected by conduits |25 and |3| to por-ts 94X and "94Y1respectively, so that the position of ram cylinder valve ed is Vcontrolled by valve |2|, the latter thus acting as a cycling valve. The *cycling valve is of -a rotary two-way type having a Ylost motion connection to the ram |2 by `means of forked larms |32 and |33 and cam Y|131! attached to the ram. The arrangement .is vsuch that valve |2i will be moved from one position to another only at the top and the bottom of I.the respective strokes. Valve Sd controls the supply of hydraulio pressure to chambers .99 and |24 of the ram cylinder and it will -th-us be seen that the position of the ram automatically .controls the direction in which it is driven.

The functioning of this automatic .hydraulic system may perhaps best be understood by a. description 'of the events which take place during a complete cycle of operations. Starting Afrom an initial Ycondition in which the ram is at the eu-v treme upper end `oi :the stroke, as shown in Fig` .9, the manual :start and :stop `valve 135 may be moved to allow .flow of fluid from .pumps and .85 through conduits 93 Aand Hit respectively to kconduit 95.. .A branch .line VI3i3 from `valve Y89 may tbe provided for the operation of the valve |93, so that Valves 89 and |91 .may be simultaneously opened. At the time of this initial movement, the `pilot .system `pump I! will VSupply iluid through conduits III, IIS and :I I9 Ato ports I MP, HEP :and IZIP. With the ram cylinder ,pilot valve :|21 in its position as shown .in Fig. 9, :port IlZIIA `will be connected to port IZIP, and `port Il2fIB will be connected to ,port |2I T, that is, to tank. The .resultant pressure in conduit :I 29 over that of conduit ISI will shift :ram lcylinder valve 94 to the right as 4shown in Fig. 9, 'connecting port 95A with pout 94T vand connecting a port 94B to port 94E. Itwill `be understood, ofcourse, that the directions of movement `of the valves given in .this description :are merely illustrative, and :that the actual .movements will depend upon the particular valve port construction. Upon this .movement Iof valve 94., .the supply from con-- duit Y95 will .flow into conduit 9S and through the branches si `and lez thereof to upper ram cylinder chamber 99. This will cause a rapid downward initial movement of .ram I2, since the ram :cylinder is .bei-ng supplied by both pumps E15 fand 186. During this action, the pressure in Chamber '93 Vwill be greater Ythan that in chamber |24 and conduit 1M. However the pressure in cham-ber Sie is not great enough to open valve 4213 and this valve remaining closed, the pressure in control conduit |223 Will be greater than that in :conduit l11.22. Die cylinder vpilot valve IIB will thus -be held in its leftward position as shown in Fig. 9., :thus connecting lport l ISP to port HSA and connecting port IISB to tank. Conduit lf2? will therefore be pressurized, shifting die cylinder valve YIM so as to connect port l MP to port IIB. It will thus be seen that during the first portion of .the .-ram down stroke, pressure will vbe supplied .to the chamber of die cylinder 49, holding the dies in their locked position.

The ram will continue to move downwardly under the influence of the hydraulic .fluid delivered by pumps 85 and '85 until the compressive forces in the ram are such that the pressure in the supply line I 69 becomes greater than the setting of pressure regulator valve IG?. When this occurs only the .iiuid from pum-p 85 will be delivered to the chamber 99 check valve |68 preventing .back lovv .of fluid to Ipump 85. r-Ihe rluid delivered from this .pump will be .returned to the tank via return .conduit |38. The ram will Acontinue to .move at the slower rate until cam engages arm 1.6.5, shutting off the flow from conduit |92 to conduit |94. The supply fluid from conduit Q5 will then .now only through branch 97| and through restriction 9B to the chamber 99. The .restriction 93 will thus have the effect of .further reducing the velocity of the ram as .it continues downwardly.

As the-charge .of powdered metal is compressed to greater density, the axial forces in ram I2, and thus the hydraulic pressure `in chamber 99, will steadily increase. Valve |"23, which is .subject to the pressure in chamber S9, is vset to open when this pressure has reached a point at whichthe proper density of the powder .charge is reached. This .pressure vmay be predetermined from tests or by calculation, and the valve `I2A3 is preferably adjustable .so .that its opening pressure may be varied. Upon itsv opening, conduit |22, connected to port iliX, will be subjected to the pressure from chamber te. Conduit 12E, which is connected between conduit IE and port HEY, is still subjected to the relatively low pressure in chamber |24. The resultant pressure differential will thus shift die cylinder pilot valve H8 to a position such that port Hel is connected to port HSB and port HBA is connected to tank. This in turn will shift die cylinder valve i I4, connecting port l IAB to tank. The die cylinder A9 will thus be abruptly relieved of pressure, allowing the retraction of die piston 5i. As described above, this action will allow the rod to move downwardly under continued axial force of ram l2. lt will be observed that since the supply fluid for the ram nows only through restriction 98', the opening or valve 23 will not materially lessen the pressure in chamber 9s, so that there is no danger of throwing in the auxiliary pump and thus speeding up the stroke. The rod will thus move downwardly at a controlled rate desirable for the operation oi the furnace.

When the ram i2 reaches the bottom of its i stroke cam |34 will strike arm ls, shifting ram cylinder pilot valve l2! so thatport lZiP is connected to port l2|B and port lziA is connected to tank. lThis action will shift ram cylinder valve 94 so as to connect port @4P to port 94A and port 94B to tank. The pressure differential between chambers 99 and |24 will thus be reversed, and the fluid from pumps 85 and te will begin to drive the ram 8! upwardly. At the same time, the pressure drop in chamber @il will allow closing of valve 123, and the increased pressure in conduit 125 will cause pilot valve H8 to shift back to its original position, again shifting die cylinder valve H6 so as to apply pressure to the die cylinder. During the up stroke, the iluid from chamber Si! will flow freely through conduit HM and check valve E03 back to the tank. When the ram reaches the top of its stroke, cam 34 will strike arm E32, shifting pilot valve IZI back to its original position which in turn will shift ram cylinder valve 94 so as to again supply pressure to charnber S9, and the cycle will be repeated. It will be observed that the cycle is fully automatic and will repeat until start and stop valve 35 is actuated to cut off the supply from pump d.

A die mechanism for compressing powders metal rods is thus provided in which a very high degree of consistency in the density oi the rod can be achieved. The releasing motion is accomplished during each stroke by a fully automatic mechanism which is controlled solely by the instantaneous axial force in the ram, the releasing point being easily adjustable for different density requirements.

While it will be apparent that the preferred embodiment of the invention herein disclosed is well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

l. A die for extruding a continuous rod of compressed powdered metal, said die including six elongated individual segments together forming a hexagonal passageway for the reception and formation of said rod, a collar securing said segments together in immovable relation at one end thereof, a pair oi' oppositely disposed clamping blocks extending along the remaining portion of said die, each of said clamping blocks being movable between a clamping position engageable with three of said sections and a retracted position allowing radial expansion of said sections; and means for moving said blocks between their clamping and retracted positions, said means comprising a hydraulic cylinder adjacent said die, a piston within said cylinder and movable between an extended position in operative engagement with ,one of said blocks and a retracted position out of such operative engagement, and connecting means between said cylinder and the other of said clamping blocks for operatively engaging said other block when said first block is engaged by said piston, whereby both of said blocks are moved simultaneously into their clamping position.

2. The combination according to claim l, means for supplying fluid under pressure to said cylinder to hold said clamping blocks in their clamping position, and pressure actuated means controlled by the axial force acting on said compressed rod for relieving said uid pressure when that force reaches a predetermined value.

3. A mechanism for extruding a rod of compresssed powdered metal, including a reciprocating ram for packing successive charges of said powder, a die for receiving and forming said charges, hydraulically operated holding means for preventing axial movement of said rod by the axial force of said ram, a holding valve for controlling the l'iow of uid to said holding means, a ram cylinder and piston for actuating said ram, a ram cylinder valve for controlling the ilow of iluid to both sidesJ of said ram piston and movable between a ram extending and a ram retracting position, a cycling valve controlled by the position of said ram to shift said ram cylinder valve between its said positions, said holding valve being movable between a position in which it actuates said holding means into clamping position and a position in which it allows retraction of said holding means, and iluid pressure actuated means for moving said holding valve from its first-mentioned to its second-mentioned position in response to the attainment of a predetermined pressure acting on said ram cylinder in a direction to extend the ram.

4. A mechanism for extruding a continuous rod of compressed powdered metal, including a die for receiving and forming incremental charges of said powder, a ram movable between a retracted position away from Said die and an extended position within said die and compressing one of said charges, a ram cylinder and piston for operating said ram, holding means engageable with said die for preventing axial movement of said rod when the ram is compressing one of said charges, a die piston and cylinder for operating said holding means, a die cylinder valve for controlling the ilow of fluid to said die cylinder, said die cylinder valve being movable between a clamping position in which said die piston and cylinder actuate said holding means and. a tripping position in which said die piston and cylinder release said holding means, and means for controlling the position of said die cylinder valve, said means comprising valve actuating mechanism responsive to the pressure acting on the extending side of said ram cylinder for shifting said die cylinder valve to its tripping position when said pressure has reached a predetermined value.

5. Apparatus for forming a continuous rod of compressed powdered metal in successive increments, comprising, a die. having 'an opening therethrough which normally is of substantially the same cross sec-tion throughoutits length, means for supplying powdered metal` tothe die opening at one end thereof, powder compressing means includingV a reciprocating plunger operable to compress the powderwithi'n said; die opening against the previously formed' portion ofT the rodl and thus compact to iinal form successive increments of said rod in a portion of the. die openingadjacent said one end, the remaining portion of they length ofsaid' die opening re` oei-ving a length of the fully' formed rod, at least a par-t of said remaining portion of the die be ing radially expansible, hydraulic pressure: op` erated mechanism for radially clamping the ex:- pansible portion of the die, means for supplying operating uid to said mechanism at a pressure which will cause the mechanism to clamp, the die and hold the compressed' rod against movement in the die under the influence of, the force exerted by the plunger, and valve.. means actuated in response to theforce exerted by said plunger tocompress the powder for reducing. the pressure of' the fluid suppliedv to said clamping mechanism when the force exerted by said plunger reaches a predetermined value andY thus permit expansion of the split portion of the die and movement of` the compressed rod through the die opening after the plunger has completed only a portion of` its stroke in the powder compressing direction.

6I. Apparatus for forming a continuous rod of. compressed powdered metal. in successive increments, comprising a die having an opening therethrough which normally is of substantially the same cross section throughout its. length, means for supplying powdered metal to the die opening at one end thereof, powder compressing means including aV reciprocating piunger operable to compress the powder With-in said die opening against the previously formed portion of the rod' and thus compact to` ina-l form successive increments or said rod in a portion oi the die opening adjacent. said one end, hydraulic; pressure means for reciprocating said plunger, the remaining portion ofthe length of said die opening receiving a. length of: the fully formed rod, atleast a partofsaid remaining portion of the die being radially expansible, hydraulic pres-V sure operated mechanism for radially clamping the expansible portion of the die, means for supplying operatingfluid tosaid mechanism at a pressure which will cause the mechanism to clamp the die and hold the compressed rod against movement in the die under the,A influence of' the force' exertedv by the.V plunger,- and pressure operated valve means.` actuated in response toh the pressure ofthe hydraulic :duid acting on; said' plunger to compress the powder for reducing the pressure of the fluid supplied to said clamping mechanism when the. pressure of the hydraulicV uid' acting on said plunger reaches a predetermined value and thus permit expansion of the split portion of the die and movement of the compressed rod through the die opening after the plunger has completed only'A a portion of its stroke in the powder compressing: direction.

EDGAR'-V K. LEAVENWORTH.

References Cited' in the flle of this patent UNITED STATES PATENTS 'Number Name Date 473,579 Illingworth Apr; 26, 1892 757,409 Olson Apr. 12, 1904 1,101,953- Bland June 23, 1914 2,097,502 Southgate Nov. 2, 1937 2,165,614 Cook et al June 1I, 1939 2,261,304 Sparks Nov. 4, 1941 2,284,704 Welblund et al. June 2, 1942. 2,289,787Y Kaschke et a1. July 14, 1942 2,300,302 Morn Oct. 27, 1942 2,449,257 Tucker Sept. 14, 1948

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