US2379540A - Apparatus for making metal articles from metal powder - Google Patents

Description

' f July 3, 1945.

APPARATUS FOR MAKING METAL ARTICLES FROM METAL POWDER Filed Dec. 28, 1942 INVENTOR Q 4155297 H6012 /70/ /P/J ATTO usvs Patente d July 3, 1 945 APPARATUS FOR vMAKIN G METAL ARTICLES FROM METAL POWDER Albert Wood Morris, Springfield, Mass.

Original application May 25, 1942, Serial No.

444,461. Divided and this application Decemher 28, 1942, Serial No. 470,332

3 Claims.

My invention relates to apparatus for making metal articles from metal powder. This'application is a. division of my application filed May 25, 1942, under Serial No. 444,461. According to the disclosure of this specification the powder is fed to a die and a ram pounds it into shape. Some of the particular features of invention are:

' the relation of the ram to the die; the form of fire ram face which hits the powder in the die; the shifting of the place where the ram hits the powder; and the way the powder is supplied to the die. These, as well as other features, will be made clear from the diagrammatic drawing and the detailed description intended for the man skilled in the particular art.

In the drawing,

fig. 1 is a sectional view to show the die for holding the powder and one relation ofthe ram to the die;

Fig. 2 is a face view of the ram to show the character of surface which hits the powder;

Fig. 3 is a diagram, showing the circle A, which represents the powder holding cavity of die block on an enlarged scale, and the circle B, which represents the circumference of ram :1 just to indicate how the ram d shifts its hits indicated by dotted circles inside circle A and on the surface of the powder held within circle A;

Fig. 4 is a diagrammatic indication of the forgingd apparatus adapted to carry on my operations; an i Fig. 5 shows the cross-section of a product with die parts which my invention is particularly adapted to make with advantage.

The mode of operation is in several respects analogous to drop forging operations. This analogy will be referred to where pertinent.

The die 5 has a cavity of horizontal cross-sectional area larger than the area of the ram head or surface 2 which is to hit the top of the powder.

O course a clearance would be desirable for itself alone. But this difference inv areas in my case is substantially more than required for mere clearance. It has a purpose to be referred to later.

The die has upwardly slanting grooves 3, there being two or more, spaced circumferentially and along the bottom of which grooves powder may be fed to the die. I prefer to feed the powder in batches or gradually, and between hits of the ram, rather than to supply the whole quantity of powder at one time.

The ram 4 is preferably reciprocated with a screw motion, see Fig. 4, caused by the large thread 5 engaging a, mating thread in frame piece 6. When the ram goes down it turns one way and when it goes up it turns the other. A relatively heavy flywheel i, with respect to the arm,

"is mounted on the top end of the ram to add force to the ramming and twisting movement.

A die block i is mounted to shift between applications of the ram head to the powder. This shifting is such that the areas indicated in Fig. 3 are hit by the ram head as it works.

Except for shifting the die block, it will be seen that the apparatus to apply the ram is one form of forging press. Other forms could be used but the one indicated is preferred on account of the twist given to the ram on dropping. Such a forging press is known as a Percussion Type One well known form has been made by to indicate how i make use of a known forging apparatus in my operation. But I show my additional feature for rotating the die block. And I show the driving disks 20 and 2t, which are successively applied to the flywheel l to drive the ram down and then drive it up, the well known operating mechanism being merely indicated.

Turning for a moment to the prior art, I am aware of the following operations: Hydraulic presses are used to consolidate powdered metal in a die and also mechanical presses are used. Customarily they do not hit the powder as by repeated forging blows. Instead, they simply apply enormous pressure to join the powder particles. Sometimes the powder is heated as by electricity, to assist its particles to join one another. I am aware also of such proposals as seen in prior patents, 2,003,609 of 1935 and 2,065,618 of 1936, in which a die part might be considered as hitting the powder in the female die as by a analogous to the provision for a flash in making drop forging dies. When the metal is hit in drop forging operations, there is a big squeeze; the metal moves through the space between the die parts, the latter being related to provide for such true flash. In my case I have conceived the provision for a similar flash. Its purpose is to obtain several advantages. The flash clearance for working the powder under forging blows of a hammer, spreads the pressure to a useful extent, and the pressure spread is directed or squeezes" for relief through the powder to such restricted or flash clearance. For this reason there is a better chance for relative movement of all powder particles in different directions than when the powder particles are all locked in one completely tight pressure mold. In my arrangement there is a better chance for them to slip around and find the best place to settle and cohere under the pressure applied. Of course, there is no identical extrusion from slip as evidenced in a flash of forged metal. But the direction of forces and movement within the mass hit are somewhat analogous. And I conceive these forces and movements to be of substantial advantage in effectively working the powdered metal to form. When they are thus worked there is less chance for hard and soft points in the metal mass. Any such hard points when they are present as in prior art methods, tend to resist the transmission of the consolidating lines of force upon which the uniform powder consolidation depends and the powder is not then uniformly consolidated, except by greatly increasing the degree of pressure to compensate for the tendency. The consolidation of powder particles depends on their cohesion brought about by great pressure and heat. The forging blows cause heat, whether or not additional heat is supplied externally.

The provision of the flash as above referred to and by sufficient side clearance in my operation has an advantage of avoiding the ordinary requirement of accurately measuring the amount of powder fed to the die cavity. I prefer to feed the powder in batches or gradually as the contents of the die cavity are worked into form by the ram die part. This has a good many advantages as contrasted with a predetermined amount of powder all fed into a closed mold before the pressure is applied. For example, in my procedure an integral article can be built up with metal powders of different kinds distributed as desired in different regions of the solid article. Brass metal may be in one region and pure copper at another.

Preferably, the face 2 of the ram 4 is made so as to aid more than a fiat face will aid in working the metaL As shown, this face, as I prefer to use it, is formed like an end milling cuttter, see Fig. 2. But the formation is placed so that the twist of the ram as it hits the powder is in the direction opposite to what it'would be if it were to cut. In this arrangement then, the ram head gives a wipin hit. That is, the blow pounds down at the same time as the lower face formation is twisted to Wipe circumferentially. Then too, the powder must take the irregular imprint of the ram face but it can't keep it as the ram face twists to wipe it out and crunch or bite it down into the mass. As will be seen, this all causes a particular kind of metal working step or steps across the face of the powder, such working step being repeated upon every ram blow. Of course, other and equivalent forms may be used on the ram face. The one like an end milling cutter is just by way of illustration to make clear the function and how to operate with it. This is not an essential but highly desirable feature in itself. It does cooperate in a particular fashion to simultaneously work the powdered metal along with the other features of the die parts having the ram part to glve'the many blows, as in drop forging.

In providing for this sort of metal workin on the metal powder particles I have the following conceptions, among others, in mind. A known way of getting two flat metal surfaces to stick is to wring them together. Such operation consists in simultaneously pressing and wiping the surfaces, as in scrubbing, one surface against the other. Remarkable results thus obtained are witnessed by mere hand operation in wringing two surfaces of Johannson gauges together. The gauges will then stick together in a most remarkable manner. The power needed to pull even a single square inch of such a joint apart is remarkably high. When the cold metal of cold gauges can be stuck together in such manner by mere hand operation, it will be appreciated how true it is that the mutual hot surfaces of metal powder particles will be made to adhere or cohere better when they are all wrung together under the force of repeated forging blows flattening contacting particles of the powder together and applying simultaneously the heat, the pressure, and twist involved in such wringing operation as I have described. In addition, when one considers the restricted opening provided by my flash? above described, the following advantage can be seen. Upon the striking of the blow for wringing together the great number of surfaces between the powder particles, such powder particles can move in a better manner, not only downwardly, but also sidewise, due to the restricted flash" opening. The resulting movement to a su stantial extent approaches the movement of mol cules in a liquid which transmits the wringing forces in all directions. In contrast to this, when a predetermined amount of powder particles are trapped and bounded by walls on every side and the pressure applied by merely moving one or more walls as in the prior art, the movement I have pointed out is not obtained. This contrast I believe to be of large importance in the conception of my invention and the means to practice it.

The shifting areas indicated in Fig. 3 and on which the powder may receive the ram blows, may be arranged for in various ways. Just for example, the die block 8 may be mounted to rotate, see Fig. 4, from a sprocket drive 9, in circle marked A of Fig. 3. As block 8 carries the die with the cavity circle marked B, the latter will always receive the plunger within it in the same general relation, as indicated in Fig. 3. But the ram 4 reciprocating in a fixed line will hit the shifting areas, as indicated in Fig. 3, because of the rotation of block 8 on a center offset from the axis of ram 4.

To feed the powder one may give the die cavity its initial charge of small amount, and then depend on the jar of each blow to keep powder supplied from a plurality of hourglass feeding cans l0, one for each groove 3. As small streams of powder come out of the storage supplies, they run down the grooves into the die cavity. It is a 'simple matter then to have the powder feed regulated automatically. As the machine works, the powder is most effectively worked to build up the article in the die cavity. When it is big enough the machine is stopped.

A characteristic of the product made as it comes from the die will be in its interior uniformity and integrity of composition. It may be that it will need to be trimmed. But that is a small matter compared to the advantages attained when viewed in the light of dimculties inherent in trying to squeeze powder under pressure in completely closed molds.

In making this disclosure I havenot referred -to any particular metal or metals. The art is general in this respect. My invention relates to many metals, either pure or alloyed, and many articles. Some metals in the powder form may be heated by electricity or otherwise. And I desire to include, as I conceive the utility of my invention, those subsidiary operations which are known and which are generally as applicable to the steps of working with powdered metal as I do it as they are when others do it. t

Also, there are several features of my disclosure which can be used to advantage without using all of them. Just for example: the face of the ram head may be fiat; the powder may be fed all at one time; the ram may not be twisting when its blow is struck; the area of the successive blows with respect to the top face of the powder may be one instead of several shifting areas; my apparatus may be any form of forging apparatus modified for my operations. But I have described my invention with all features workable to ether in the same operation. This is the best way to work the powdered metal according to my conception.

I will now disclose the making of a specific article of other than simple cylindrical form, to shown the way my basic conception may be used with improvements for particular problems.

In the example indicated in Fig. 5, the problem is to make a cartridge case head. Fig. indicates the female die portion ll; 95 and i5 represent two ram shapes. The case head. may be made of powdered metal worked into a coherent metal body by forging operations. On account of the shape of the body, it having different depths or protuberances, I proceed in the following manner: To begin with, I treat the die cavities or recesses, one for the central boss i2 and one for the outer flange id, as if to begin with they were cavities to make separate articles of their shape. Thus, I feed metal powder to such cavities and proceed to forge it with suitable male dies i l and n5 until such cavities are filled with the coherently forged metal and to their shape. I then consider the rest of the total cavity for the case head as a-simple disk, the top line represented at dotted line it; proceed to fill it with the metal powder as in Fig. 4; forging it as I proceed until the article is finishedall in one substantially continuous or progressive operation. At such time the whole cavity is filled with the coherently forged metal. It can then be trimmed and finished much as any forging needs to be.

Of course during this operation the form of the male die will need to be changed. This is indicated by the ram forms of Figs. 4 and 5. The male die shape for the central cavity will be a different shape from the male die shape for the flange cavity. And the finishing die shape or ram for the disk shape on the top of the cartridge head will be stilldifierent. But each may be advantageously operated with respect to its cavity as if the article to be made were of that cavity shape. The male die shapes or rams the metal in the cavities at the same time in some cases, and successively in others. There is the question of timing. But it will be clear that by shifting the female die under the proper male die or shifting the male dies one after the other to apply over the female die in .proper order, the whole operation may be carried on without delay. A good way is to have a series of forging hammers carrying the series of male dies or rams arranged adjacent one another in a line. Then the female die can be shifted from one male die to underlie the other at the proper time to receive its blows. In this way the forging operations can be carried on in a substantially continuous manner from the beginning of the mold filling operations to the end when the whole mold or die is completely filled.

To help see the simplicity of the operation I refer to its analogy in some respects to the operation of making sand cores in foundry work. In the latter operation there is a shaping mold sometimes having several and separate cavities. The mold is gradually filled with sand and as it is filled the same is tamped down to make the core of uniform consistency. Now, the skilled molder knows an art of tamping the sand into its core shape so that the whole sand body is of good, uniform consistency. He fills and tamps all cavities, then fills the main body andftamps it. His tamping of the cavities depends on their shape. He may tamp the center portion of a cavity filling to push the sand hard against the walls. Then he may tamp an annular area around the outer body portion. By progressive tamping of this sort he works the sand into uniform, hard-packed consistency with uniform density and to the shape of the pattern or mold or core. By forging operations on powdered metal gradually fed into shaping dies with metal forging blows to do the tamping to the shape desired and between the powder feedingoperations are similar to the making of a sand core. That is, in mechanical operation there is a similarity. But with regard to the power used, the changes taking place in powdered metal 00- hesion, and the final results, there is of course a great difference. As a preliminary operation to the forging blows I may in some instances apply mere powder tamping hits with suitable tarnping heads to get the powder arranged with uniformity. Then the forging blows are afterwards applied to drive the particles into cohesion and to permanently join them together.

In my operations the forging blows generate a. substantial amount of heat. It prepares the particles of the powder to join one another. The pressure applied simultaneously with the heat in the metal powder and particularly the twist of the pressure blow wrings the powder particles together, all giving a degree of coherence which is highly desirable.

There is also an advantage in my operations in this: As the article is formed gradually, increasing in weight after each batch feed of powder, the metal character of the powder may be varied. For example, if it is desirable to have the upper portion of one metal character and the lower of another, the character of the metal powder may be changed. The operations, except for the material fed and the time of feeding, are the same. Not only the metal character, that is its composition, may be changed, I

as copper to brass, but the size of the powder particles may be changed, or both may be changed. This will give controlled characteristics to the body of the article made. That is, its consistency, considered microscopically, may be varied whether the feed be changed with respect to kind of metal (or alloy) or size of their particles, or both. This fact makes my way of making the article adapted for easily varying its metal or physical characteristics or both such characteristics of the article.

Having disclosed my invention and its various features so that the man siklled in the art may use the improvements, what I claim is:

I claim:

1. A hammer head or ram having a striking face of generally toothed form in which the ridges of the teeth may hit powdered metal and the sloping faces of the teeth may wipe the powder with a metal working operation when the powder is hit, means with a die cavity to hold 'the powder for hitting with the hammer, said means having a flash-like clearance with respect to the hammer head as it enters the cavity to hit the powder and power means to work said hammer in the way of a forging hammer, with means to twist said hammer about an axis coincident with its line of application to the powder whereby the teeth on the hammer will wipe the face of the powder with great power simultanepower means to operate said hammer against the powder with enough force to heat and join its particles under repeated blows powder feeding groove means leading to said cavity, powder feeding means adapted to feed said cavity slowly with powder during the operation of the machine, said cavity being larger in area than the hammer, and means to shift said die part with relation to the hammer blow so that hammer blows overlap each other and gradually cover the whole area of the powder in said die part all for the purpose described.

3. A metal working apparatus to forge parts made of powdered metal, comprising an automatically operable forging hammer on its hitting edge having teeth with sloping surfaces on "corresponding sides, means to twist the hammer at the time of the forging blow and irr-a direction for the sloping surfaces of the teeth to wipe powdered metal particles together as they are forged, and a suitable die to hold the powdered metal for working it bythe forging and wiping action of the forging hammer.

ALBERT WOOD MORRIS.

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