MXPA99007493A - Pulsed pressurized powder feed system and method for uniform particulate material delivery - Google Patents

Abstract

A powder feed system for delivering a quantity of particulate material to a die cavity (5) of a powder press is provided. The powder feed delivery system includes a receptacle (13) for receiving and delivering particulate material to the cavity (5). The receptable (13) has an ingress (15) through which particulate material is received under pressure and an egress (17) for registering with the interior of the cavity (5) and through which particulate material is delivered under pressure from a feed conduit (21) to the cavity (5).

Description

SYSTEM AND PRESSURIZED FEED METHOD WITH PRESSES FOR THE UNIFORM SUPPLY OF MATERIAL PARTICULATE BACKGROUND OF THE INVENTION This application is a continuation of part of the Provisional Patent Application No. 60 / 038,186, of the United States, filed on February 14, 1997, incorporated in its entirety by reference to this specification, which is a continuation in part of the Patent Application. No. 08 / 705,434, of the United States, filed on August 29, 1996, incorporated in its entirety by reference to this report, which in turn is a continuation in part of provisional application No. 60 / 019,945 filed on June 14. of 1996, incorporated in full by reference to this report.

Field of the Invention This invention relates, in general, to powder feed systems and delivery methods for feeding and depositing particulate or finely divided material in the cavity of a mold of a press for pulverized material, for compacting it. More specifically, the invention relates to a feeding system and a delivery method that distributes, with uniform density, the particles throughout the mold cavity. The feeding system and delivery method also provides a uniform, predetermined and constant weight of particulate material in the mold cavity. In one embodiment, the invention provides an apparatus and method for supplying particulate material to the mold cavity of a press for pulverized material, without the need to use a shuttle. The invention is also directed to a feeding system that includes a scale to accurately weigh the weight of the particulate material before feeding it into the mold cavity.

Description of Related Inventions In powder metallurgy, the products and parts are formed by pressing, in the desired form, finely ground or powdered metal powders, into the mold cavity of a press for pulverized material. In general, the metallic powders are compacted in the mold cavity, at room temperature, and then the compact "non-sintered" semidens is removed from the mold and heated to very high temperatures (at the material melting temperature or at a temperature approximate) to agglomerate the powders into a unified mass. The process of joining by heating, is generally known in powder metallurgy as sintering, or analogously in the field of ceramics and carbides, cooking.

When these or other similar methods are employed, some means is needed to supply quantities of powders or particulate material to the mold cavity of the press. In general, feed channels are used to supply the powders or particulate material to the mold cavity during the pressing cycle, by means of a gravity filling system. This system involves the movement of the feed channel, which contains the particulate material, in a shuttle that slides the channel forward along the table of the molding press, to a position in which the lower feed hole of the channel of feeding is exposed, superimposed and exactly matches the mold cavity, supplying enough loose powder due to gravity, to fill the mold cavity volumetrically. Next, the shuttle moves the channel back along the table of the molding press to a retracted position. This action suspends the flow of particulate material induced by gravity, from the lower orifice of the feeding channel. Then, the particulate material that is in the mold cavity is compressed into an article and the article is ejected from the mold. Then, the shuttle slides forward the channel, along the table of the molding press, displacing the ejected article and exposing again the lower hole of the feeding channel as it turns and coincides with the mold cavity. . Once again, gravity is used to fill the mold cavity with particulate material, more or less volumetrically. However, the very small holes in the mold cavity are not filled evenly. Then, once again the feed channel is retracted to suspend the flow of gravity of particulate material into the cavity.

The above-mentioned typical example of a feed channel supplies particulate material by volume (volumetric). Such volumetric feed channels depend on the pulverized material they are supplying, have a consistent bulk density and good flow characteristics (low Hall Numbers), so that there can be a precise and uniform feed rate. However, because many of the powder materials used are heavy and dense, they tend to self-compact. Moreover, the mold cavities used to make very large pieces with very fine details, are especially difficult to fill uniformly. Accordingly, these volumetric feeding channels and delivery methods, and the like, are generally not suitable or satisfactory to provide a uniform uniform distribution, nor a good density of the powder throughout the mold cavity. Consequently, the density of the pieces formed with these powder compacts is not uniform throughout the piece, and they are not consistently uniform from one piece to another. Consequently, these pieces tend to crack due to tension, especially when being expelled from the mold cavity. And if this were not enough, often the fissures only become visible in sintering.

In addition, parts with complicated shapes and parts with very precise dimensional tolerances, such as helical gears and sprockets, can not be produced satisfactorily using the pulverized material feed methods, or the feed channels, that is commonly available. Since these prior art feeding methods and channels rely solely on gravity to induce flow of the particulate material into the mold cavity, and are not suitable for uniformly supplying powders to all areas of complex mold shapes, which are needed to produce an article such as a helical gear or a cogwheel.

Specifically, the powders simply fall from the feed channel to the mold, but without any density rhythm or regularity. Certain areas of the molds, especially of molds with complex shapes, receive more particulate material than other areas. As a result, the resulting parts have an uneven density, they can fail, and their commercial use is doubtful.

Traditional methods of volumetric feeding of powders are hampered, even more by the fact that the weight of the material supplied to the mold can not be controlled, which makes it impossible to supply a uniform weight from one piece to another. Consequently, this limits more the uses of the pieces made with powder metallurgy.

Generally, as a solution to the problem of the existence of an irregular density of the powders in the mold cavity, for example when using aluminum powders, the feed hopper is agitated or vibrated to induce the flow of the particulate material and to regularize the density of the powder in the mold. However, with this method it is necessary to invest a lot of time, and it is not exact or adequate to achieve a sufficiently uniform density from one piece to another and in all areas of the piece itself.

Another disadvantage is that when shaking fine powders the "fines *" and the "fine particles *" are separated from the powder, which then remain suspended in the air and end up covering and contaminating everything around. Frequently, many of the powder materials that are used in powder metallurgy to build parts are very expensive and in some cases toxic. Also, aluminum powders suspended in the air are very explosive. Consequently, the problem of fine particles can represent a great economic loss or dangers to health or safety. Therefore, it is currently working with systems of recovery of fine particles, quite complex and expensive, and taking precautions for the safety of personnel, such as the use of masks.

U.S. Patent No. 3,697,208 to Munk et al. Describes an apparatus for filling molds with powdered fibrous materials by blowing the material into the mold. The air used to blow the material into the mold comes out through a perforated plate or a. sieve placed on top of the N. del T. In "fine" powder metallurgy means powders with particles smaller than 44 micrometers. Fine particles means powders with particles smaller than 76 micromillimeters. mold to avoid the loss of mold material during the blowing process. However, this apparatus does not serve to supply all types of particulate material to a mold, especially metals that tend to be heavier, and, consequently, would not move in the open system described in the Munk et al. Patent. The process of Munk and collaborators works like a sand sprinkler that extracts dust into an air jet that precedes the supply of dust. The air / dust ratio is quite high, and the time to carry out the filling is short. In addition, a uniform density can not be achieved in the pieces made with compressed powder due to the powders flying towards the perforated plate or screen during the supply. The requirement to use sieve, makes it impossible to build parts that do not have flat top surfaces.

U.S. Patent No. 4,813,818, to Sanzone, discloses a feed channel having a hopper that receives powdered materials from a source that communicates through a feed tube with a closed fill chamber. The filling chamber is equipped with a vacuum cleaner. The vacuum cleaner is applied to help the gravity flow of the powders through the feed tube and into the filling chamber. However, the evacuation of the chamber does not provide the rigorous density uniformity that is necessary to produce articles such as materials for thermal use applications, or articles that have strict dimensional control, etc. In thermal use materials a strict uniformity of the properties (ie coefficient of thermal expansion, thermal conductivity, etc.) is required throughout the article and from one article to another. The evacuation proposed in the Sanzone patent also does not provide for exact controlled dust weights to be supplied to the mold cavity. In addition, with the Sanzone method, the driving force exerted on the powders can never exceed atmospheric pressure.

In addition, there is currently technology to control and move the mechanical parts of the molding presses with speeds much faster than those that exist at the present time. The speed at which a molding press can produce articles is limited by the speed at which the mold cavity can be filled with particulate material. This speed is relatively slow when known methods are used to supply particles and feed channels in which gravity is used to feed the powders into the mold cavity. Accordingly, the known methods do not allow the molding presses to reach their maximum capacity to produce parts. The production speed of the molding presses is even slower when vibratory methods are used to try to create a more constant powder flow.

Moreover, in some cases there is an additional waste of time in extending and retracting the feeding channel from and into the mold cavity, so as not to encounter the upper die of the molding press during the pressing cycle or "stroke". The stroke time is lengthened due to the need for sufficient time to raise the upper die sufficiently to allow the feed channel to pass underneath on its way to the retracted position.

In the aforementioned known methods and feeding channels for supplying particulate material to the cavity of a mold, the step that consists of retracting the feeding channel by dragging it on the upper surface of the wear plate of the mold table, is necessary to cut the flow of particulate materials from the feed channel. However, this retraction of the feed channel, after filling the cavity of the mold, results in the accumulation of dust in the mold, near the trailing edge of the feed channel. This effect of "kneading" induced by friction, further exacerbates the problem of obtaining parts and articles that do not have a uniform density, as it compacts the particulate material in the mold cavity, resulting in all the aforementioned disadvantages mentioned above. .

The present invention solves the aforementioned problems, and others, by providing a powder feed system and a powder delivery method where pressure or air is used to feed the powders into the mold cavity, thereby avoiding problems inherent in gravity feeding systems. By using pressure or air in the present powder feed system and delivery method, a mass of powder is pushed well into the mold cavity, at a relatively fast speed, and a subsequent pulsation serves to level the powders inside the cavity.

The present invention further provides a method and an appended apparatus suitable for evenly and evenly distributing particulate material in all areas of the mold cavity, which functions by fluidizing the particulate material once it is located within the cavity. The resulting uniformity of material distribution in all areas of the mold cavity is carried out both in quantity and density. Moreover, the fluidization of the powders inside the mold cavity, before being carried out the compaction in the molding press, allows to fill in a uniform way the molds, including molds with complex geometries and those that serve to produce pieces of several levels. In addition, such fluidization of the particulate material can also be used to mix well powders of different materials (and densities), in order to create a homogeneous mixture of powders in the mold.

It should be understood that the use of the terms "powders" and "particles" or "particulate material" are interchangeable for the purposes of the description made in this specification, and should be interpreted as including any material whose nature is constituted by particles , and should not be limited to pulverized metals only.

The present invention also solves the problem of supplying a constant amount, by weight, of particulate material to the mold cavity, from one pressing cycle to another pressing cycle (from pressed to pressed part) providing a gravimetric feed system and a method for supplying particulate material. For purposes of this invention, the term "predetermined" is used to designate the weight of the powder to be delivered to the mold cavity of a press for pulverized material, in order to produce a piece of a specified desired weight. It should be understood that such weight will vary from one application to another (and from one piece to another) and, consequently, for purposes of this invention can not be quantified definitively.

Therefore, in the mold cavity of a press for pulverized material can be made forms of complex parts and pieces, with strict dimensional tolerances, such as gears of helical teeth and gear wheels, which until now could not be obtained by the methods of powders up to now known, using the present methods and powder supply apparatus. In addition to providing such dimensional tolerances "as molded", the present invention provides a broader applicability for the designs of pieces by imetalurgía, pieces with better ratio of net weight to full weight, as a result of which there are less fissures in the compact non-sintered and sintered parts, faster preparation times, and a higher production speed.

The present invention also allows, optionally, a system and method for supplying powder without shuttle. As the particulate material is supplied directly to the mold cavity by pressure or air, no time is lost to extend and retract a feeder reservoir to feed (throw) powders into the mold cavity of a press for pulverized material. The absence of a shuttle also eliminates the kneading of the powders caused by having to drag the known feeder tanks back into the mold cavity so that they remain seated in their retracted position. As an extra advantage, the present invention can optionally be used as a completely closed system, and in this way also reduces or eliminates the waste of dust and the environmental hazards produced by dusts lost around the cavities of the mold, which is what happens when using methods and apparatuses traditional feeders. Also, since no part of movable shuttles is needed, there may be fewer parts that break or wear out, thereby reducing costs. The safety problem of possible obstruction of the upper die of the press is also reduced.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an exploded view of a powder feed system, in accordance with an embodiment of this invention; Figure 2a is a schematic side view of an embodiment of the powder feed system, according to the present invention, in the feeding (hooked) position. Figure 2b shows the power system of Figure 2a in the reset (unhooked) position.

Figure 3 is a schematic side view of a powder supply system, showing the pressure vessel and the supply conduit.

Figure 4 is a detail, from the top, of an annular feed receptacle used in the powder feed system, according to the present invention, showing the back pressure filter cleaning system.

Figure 5 is a schematic view of an embodiment of the present powder feeding system, including a scale.

Figure 6 is a perspective view of a sprocket made using the present invention.

Figure 7 is a histogram of the concentricity values of a series of thirty pieces made in accordance with the present invention.

Figure 8 is a histogram of the height values of a series of thirty pieces made in accordance with the present invention.

Figure 9 is a histogram of the weight values of a series of thirty pieces made in accordance with the present invention.

Figure 10 is a graph illustrating height accuracy of thirty consecutive pieces made in accordance with the present invention.

Figure 11 is a graph illustrating the weight accuracy of the present powder feed system for a part having a target weight of 500 grams. The graph shows thirty repetitions of the feed cycle and illustrates the reproducibility of the weighing system.

Figure 12 is a graph illustrating the poor concentricity variation of 30 consecutive gears whose specified diameter is 2.7 inches.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In its most basic embodiment, the present invention is directed to a method and apparatus for using pressure or air to push a mass of powders, from behind, into the cavity of a mold of a press for pulverized material and subsequently fluidizing the powders in the cavity of a mold, so as to provide a distribution of the powder, with a substantially uniform density, within the mold cavity. Such fluidization can be carried out independently of the pressurized supply. In other words, the powders or particulate material that have been delivered to the mold cavity of a press for pulverized material (or any other apparatus for making pieces or components with particulate material) by conventional methods, can also benefit from a subsequent fluidization. , once they are inside the cavity, by the application of the present invention.

Referring now to the embodiment illustrated in Figure 1, the outstanding features of a gravimetrically pulsed feed powder delivery system are shown. The feeding system, as shown, refers to the feeding and delivery of a precise quantity of powdered metals into the cavity of a mold. The pulverized metals (not shown) are supplied uniformly by exerting pressure, from behind, to push a mass of powders towards all the zones of the mold cavity 5, which will be compacted by the simultaneous application of the upper punch 7 and the lower punch 11. Metal powders are only being used for purposes of illustration and to show this invention; consequently, it should not be construed as that this invention is limited solely to the handling of metallic powders, but may also be applied to the handling and delivery of particulate materials of different weights and types, including but not limited to, for example, scales, powders, fibers or sheets of ceramics, polymers, cars and cements (cementitious materials mixed with water).

The present invention can push 500 grams of powders into a mold in only three seconds, or less. Consequently, the total cycle time to produce a piece is reduced by approximately 10 seconds, using conventional methods for feeding the powders, to 4 seconds or less when the present methods and system are applied. The concentricity and tolerances of height and weight of such parts are also considerably increased.

Specifically, the invention, as shown, is directed to a powder feed system for supplying a quantity of particulate material to the mold cavity of a press for pulverized material, such as the powder feed system exemplified in FIG. Figure 1, which is now referenced. The press for pulverized material includes a platen 1 having a table-like surface 2 which is flush with the cavity of the mold 5 and which surrounds it. The press further includes an upper die 7 which is attached to the upper ram 9 and the lower die 11. The powder delivery system, as shown in Figure 1, includes a receptacle 13, which in this case is shaped annular, which receives and supplies particulate material to the mold cavity 5. The receptacle 13 is connected to the surface of the mold 22 by means of a suitable connector, such as the illustrated bolts 4 that extend through the fasteners 4 of the receptacle and then through the threaded holes 6 in the surface of the mold 22. The receptacle 13 has an access 15 through which a mass of particulate material is received, under pressure, and an outlet 17 which coincides and communicates with the interior 19 of the cavity 5 and through which the particulate material is pushed, under pressure, from the supply conduit 21 through the interior space 16 towards the cavity 5. The supply conduit 21 is tightly sealed e at the first end 23 to the port 15 of the receptacle.

In Figure 1, the pressurized powder feed system, according to the present invention, is shown with an annular receptacle 13 and includes a body 14 of the annular receptacle that surrounds and defines the interior space 16. The body of the receptacle 14 has an upper side 18 and a lower side 20 and is sealingly connected, on the lower side 20, to the surface of the mold 22, the surface of the mold 22 being contiguous with the table-shaped surface 2 of the plate 1, so that the body of the annular receptacle 14 surrounds the upper edge 3 of the mold cavity 5, and the interior space 16 is contiguous with the cavity 5. An exhaust hole 35 extends through the body of the receptacle 14 to release the pressure that there is inside the interior 19 of the mold cavity 5.

Figures 2a and 2b illustrate an alternate embodiment of the present pressurized powder feed system, wherein the receptacle 113 has an annular shape and includes an annular receptacle body 114 quo and defines the interior space 116 through which the upper die passes. 107. The exhaust hole 135 extends through the body of the receptacle 114. The body of the receptacle 114 has a lower surface 120 for sealingly engaging the surface of the mold 122 surrounded by the plate 101 (shown in the position engaged in the Figure 2a) and the upper surface 118 to which it is movably attached and suspended from the upper ram 109 by the spring hangers 143 through which the anchoring posts 146 which are attached by the first end 145 to the receptacle body pass. 114, and extending slidably through the second end 114 toward the recess 149 of the upper ram 109. During operation, the upper ram 109 descends, lowering the body of the annular receptacle 114 to a position in which the lower surface 120 of the receptacle body 114 makes contact with the upper surface 122 of the mold cavity 105. The upper ram 109 continues to descend, whereby the upper punch 107 is lowered through the interior space 116, whereby the interior space 116 is sealed before continuing its downward course towards the mold cavity 105 and presses the particulate material (which is pushed into the cavity of the mold). mold 105 through feed conduit 121) against lower die 111.

In an alternate embodiment, which is not specifically illustrated herein, the receptacle body may form part of the mold and settle "in" the cavity, whereby the upper part of the body of the receptacle is flush with the surface of the plate . In such an embodiment, the powder feed system according to the present invention includes an annular (or otherwise suitable) receptacle body surrounding the mold cavity and defining it. The body of the receptacle has an upper and lower side, and is positioned such that the upper side of the body of the receptacle is flush with the table-like surface of the dish. Such a configuration is useful in those situations where the press for pulverized material ejects the pieces by lowering the plate relative to a stationary lower die to push up the part and eject it from the mold cavity. As will be appreciated by those of skill in the art, in the embodiments of the present invention in which the feed receptacle is bolted to the top of the plate, the parts may be stopped within the interior space of the receptacle after ejection .

It should be understood that in all of the above-mentioned embodiments, the "annular" shape of the receptacle is given as an example only, and that in fact the receptacle can have any shape with which the mold cavity is suitably surrounded, and that it has a interior that defines the shape of the cavity of the mold conforming more or less to the shape of the edge of the cavity. Accordingly, it should not be construed that the present invention is limited to annular receptacles.

In specific cases, the receptacle may be the upper punch or the lower punch of the molding press. Such a configuration can be specifically suited for situations in which very small parts are manufactured. In such cases, the integrity of the lower die is not reduced and compromised by the loss of the mass of the lower die necessary to convert it into a receptacle through which powders can be delivered.

In another alternate embodiment (not shown), the receptacle is box-shaped, and the access is a top access and the exit is a lower exit. The box-shaped receptacle is optionally arranged to cooperate with a shuttle, such as a pneumatic piston / cylinder or an articulated mechanism, to selectively reciprocate the receptacle along a horizontal plane above and beyond. transverse way to a position with which its lower outlet would be suspended from the mold cavity, and to move the receptacle downward so that its lower opening coincides with the mold cavity. Then, the powders in the receptacle are pushed, with pressure or air, into the mold cavity. Next, the box-shaped receptacle is thrown outward to allow the upper die to descend into the mold cavity and press the piece.

Referring now to Figure 3, the present invention is again illustrated, whereby? less a pressure generator 225 is sealingly attached to the upper end 227 of the pressure vessel 229, and is in open communication therewith. The pressure vessel 229 is connected, at its lower end 226, to a second end 231 of the supply conduit 221. The pressure generator 225 aims to provide a pressure greater than atmospheric pressure in order to push the particulate material from the container 229 , through the feed conduit 221, into the mold cavity 205, and to optionally fluidize the particulate material 233 that is inside the cavity 205, thereby creating a substantially uniform density distribution of the particulate material 233 inside the cavity 205. Preferably, the feeding conduit 221 should be made of a material that does not generate static electricity. The inventors have found that a tube of conductive Teflon material, with graphite flakes dispersed therein, located within a stainless steel sleeve, for the purpose of grounding can be very useful. However, any non-static material is suitable for use as a supply conduit. At least one exhaust hole 235 extends through the body of the receptacle 214 to release the pressure existing within the cavity of the mold 205. The body of the receptacle 214 of this memory is shown surrounding and defining the interior space 216. The body of the receptacle 214 has an upper side 218 and a lower side 220, and is sealingly connected, on the lower side 220, to the surface of the mold 222 surrounded by the plate 201, so that the body of the annular receptacle 214 surrounds the upper edge 203 of the mold cavity 205, and the interior space 216 is contiguous with the cavity 205.

At least one exhaust hole is provided at any suitable point of the powder delivery system of the present invention. For example, as shown in Figure 3, at least one exhaust hole 235 may be located in the receptacle 213, where it extends through the body of the receptacle 214; or alternatively, at least one exhaust hole may be located in the pressure vessel 229 or both. Exhausting orifice 235 allows the release of pressure within the mold cavity 205, as pressure is used to push the powder into the cavity 205, and can also be used in conjunction with pressure pulsations to fluidize the powder which are inside the mold cavity 205. The exhaust hole 235 is further equipped with a valve 236, such as a cam-operated valve, to open and close, to relieve the pressure inside the mold cavity. 205 Referring now to Figure 4, the exhaust hole 335 is also optionally equipped with a sieve 337 located on its closest side, to prevent dust from escaping from the mold cavity 305 through the hole 335 during the supply of pressure through the powder supply conduit (not shown) into the mold cavity 305. In addition, the exhaust hole 335 is optionally equipped at its furthest end with an auxiliary pressure generator (not shown). ) to expel the powders out of the sieve 337, to clean it. A third optional conduit, the auxiliary conduit 338, is located in the receptacle 313 to supply any amount of useful additives to the interior of the mold cavity 305. Such additives include, for example, solvents, reactive lubricants of the wall of the mold. mold, activating solutions (diluted acids for the cold welding of powders), plus any other quantity of substances that are used in the production of parts and components with the press for pulverized material.

As described, the aforementioned feeding system can be gravimetric and, thus, optionally will also include a scale (or several scales for multiple weighing) juxtaposed between the receptacle of the feed system and the source of the particulate material. The scale is used to weigh the amount of particulate material before it is delivered to the mold cavity. The present gravimetric delivery method and feeding system is capable of supplying a single powder shot, up to 3000 or more grams, to be preweighed with an accuracy of approximately 0.1 grams of tolerance. The powder shot is optionally weighted and pushed from behind, under pressure, into the mold cavity, and is fluidized once it is inside the mold cavity (causing it to behave fluidly as in its natural state), with which uniformly fill all areas of the cavity, with a uniform density.

Referring now to Figure 5, a scale according to the present invention is constituted by the scale container 460 which receives a quantity of particulate material (not shown) from the lower end 462 of the hopper 464. The container 460 of the scale receives the amount of particulate material. The scale container 460 has at least one lower outlet opening 466 for expelling the particulate material to the pressure vessel 429. The scale container 460 has an upper edge 468 that has at least two points of contact. 470 support located in it. The elongate support braces 472 are suspended from the closest end 475 and attached thereto, at each of said support points 470 at least, and are joined at their most distant end 476 to the crossbar 478. The crossbar 478 is supported on the piezoelectric element 479. The piezoelectric element has a signal transmitter (not shown) that sends signals to a controller (not shown) to open and close the valve 480 associated with the discharge opening 462 of the hopper 464 The pressure vessel 429 has a valve 482, to prevent the escape of pressure when the pressure vessel 429 is receiving the pressure supplied by the pressure generator 425. The pressure vessel 429 abuts, above and in an off-center manner, on the piezoelectric element 479 by means of the crossbar 484. The crossbar 484 is constituted by a horizontal support 485 and by a vertical support 486, each of which is mounted astride the piezoelectric element 479. The pressure vessel 429 is suspended above the horizontal support 485 by the suspenders of spring 487. Pressure generator 425 generates pressures in excess of atmospheric pressure within container 429, feeds duct 421 and mold cavity 405, and is connected to pressure vessel 429 by means of pressure duct 488, since an electronic controller (not shown) whose function is to start and stop the supply of pressure to the container 429.

It is important to note that the weighing system according to the present invention operates independently of the pressure supply system and, therefore, does not pose any time disadvantage for the system. Accordingly, suitable quantities of pulverized material are weighed during the pressing cycle and, consequently, they can be used immediately once the contents of the pressurized feed system receptacle are supplied to the mold cavity.

As also shown in Figure 5, the pressurized feed system generally includes a body 414 of the feed system receptacle, through which a quantity of particulate material (not shown) is pushed into the cavity of the mold 405 and the powder feed conduit 421 for communicating with the body 414 of the receptacle. In addition, several pressure systems can be used together to provide different materials, such as copper aluminum, to make a heat sink with a copper aluminum base to have a low coefficient of thermal conductivity, or a wide variety of alloys, with different compositions, to make functionally graduated alloys.

During operation, the body 414 of the feed receptacle is positioned so that the interior space 416 exactly matches the cavity of the mold 405 and is contiguous thereto. The upper die 407 is lowered to a position in which it contacts the inner periphery 408 of the body 414 of the receptacle and seals the cavity of the mold 405, with respect to the external atmosphere, thus allowing pressurization of the system. The valve 454 of the hopper opens and allows the particulate material of the hopper 454 to flow into the container of the scale 460, with the valve (hinge) 467 closed. When the piezoelectric element 479 registers the weight of the particulate material that is within the container of the scale 460, and detects that it is half of the previously determined weight, the piezoelectric element 479 sends a signal to partially close the valve 454 of the hopper, thereby reducing the flow velocity of particulate material that goes from the hopper 464 to the container of the scale 460. When the piezoelectric element 479 registers that the weight of the particulate material that is inside the container of the scale 460 already has the predetermined weight, the valve 454 is completely closed, thereby stops the flow of particulate material from the hopper 464 to the container of the scale 460. The valve 467 opens to eject the particulate material to the pressure vessel 429. The valve 482 is closed and the pressure generator 425 generates pressure inside the pressure vessel 429, whereby the particulate material is pushed through the powder feed conduit 421 into the interior space 416 of the body 414 of the receptacle and into the mold cavity 405. The pressure is exhausted through the exhaust hole 435 (or through an auxiliary exhaust port not shown) either simultaneously with the pressure generated, pushing the particulate material, or a shortly after. Subsequently, the pressure generated is exhausted in a series of pulsations, but at least one, to fluidize the particulate material that is inside the mold cavity 405 and thus evenly distribute the powders, with a uniform density, within all the zones of the mold cavity 405. The upper die 407 continues in a downward movement and the particulate material is compressed within the cavity 405 to produce a piece (not shown). The cycle is repeated for each piece that is going to be produced.

For purposes of the present invention, the fluidization step serves to level the powders within the mold cavity, so that they have a uniform density throughout the mold cavity. This step of fluidizing the powders can be done independently of the supply of pressurized powders, and in this way it can be used in traditional powder feeding methods and in feeding ducts in which a shuttle simply drops the powder into the mold cavity. For purposes of the present invention, fluidization can be carried out with several methods, and can include, but not limited to, the pressurization and exhaust of the mold cavity, by shaking, by vibration, the full cavity (ultrasonic, sonic vibration, agitation, electric field or magnetic impulses, etc.) or by adding powder mixed with a liquid component to the mold cavity. Such liquid could be subsequently removed by evaporation or suction, or expelled by pressure.

The present invention is further directed to a method for creating the distribution of a quantity of particulate material, with uniform density, located within the mold cavity of a press for pulverized material. The method includes supplying a quantity of particulate material to the mold cavity and fluidizing the particulate material that is inside the mold cavity, to evenly distribute the particulate material, so that it has a substantially uniform density throughout the mold cavity. mold. Preferably, the step of fluidization includes sealing the mold cavity with respect to the atmosphere and then applying at least one pressure pulse inside the mold cavity, or a series of pulsations. The series of pressure pulsations can be constituted from two to approximately 100 pressures of pressure, each of which includes supplying a pressure greater than atmospheric to the cavity of the sealed mold, and then exhausting the pressure that is inside the cavity of the mold. mold. Preferably, each of the pressure pulsations includes supplying pressure to the mold cavity in the amount of about 1 pound per square inch ("psi") to about 150 psi, for a period of time of approximately 10 seconds, and exhausting the pressure at least once during a period of time of approximately x seconds. Generally, such pressure pulsations include supplying pressure to the mold cavity in the amount of about 1 psi to about 150 psi, for a period of time from about 0.01 seconds to about 60 seconds, and to exhaust the pressure at least once per a period of time from about 0.01 seconds to about 60 seconds.

In an especially preferred method, the series of pressure pulsations includes approximately 2 to approximately 100 pressures of pressure. Each of the pressure pulsations includes supplying pressure to the mold cavity in an amount of about 1 psi to about 150 psi, for a period of time from about .01 seconds to about 60 seconds, plus pressure exhaustion of at least one for a period of time from about .01 seconds to about 60 seconds.

In the method according to the present invention, the pressure above atmospheric pressure can optionally be applied simultaneously with the powder supply passage, to push the particulate material into the mold cavity. In such cases, the pressure applied during the delivery of the powders is from about 1 psi to about 150 psi, and is applied for a period of time from about 0.01 seconds to about 60 seconds. In the methods according to the present invention, where pressure is also used to push the particulate material into the mold cavity, the fluidization step can alternatively include exhausting the pressure used to push the particulate material into the interior of the mold. cavity of the mold, of the cavity of the mold, in a series of pulses of exhausted, or at least one. Preferably, the series should be comprised of approximately 2 to 100 exhaustion beats, and each of the exhaustion beats should preferably last from about 0.01 seconds to about 60 seconds.

As a rule, the appropriate specific pressures that are generated within the mold cavity when applying the present method and powder feed system, are easily optimized, and should not be construed as limiting only to the parameters specifically indicated above. . These pressures will generally vary depending on the size and complexity of the mold cavity, and the degree of difficulty in uniformly filling the mold cavity. Likewise, the length of time suitable for pressurization (and for exhausting) can also be easily optimized by anyone who has knowledge of the subject. The aforementioned optimization is also applicable to create a suitable pulsation pattern to supply and exert pressure to create a fluidized bed of powders within the mold cavity, which results in a uniform distribution of the density of the powders in the cavity of the mold before compressing the powders, or to homogeneously mix different powders (which may optionally have different densities each) within the mold cavity. However, the step of fluidizing the powders that are inside the mold cavity should not be limited to generating and exhausting pressure within the cavity, and should be interpreted as including other means to render the particulate material that is within the cavity of the mold behaves like a fluid and in this way is distributed with a uniform density throughout the mold cavity. Such means may include, but are not limited to, methods for agitating the filled mold, such as by creating an electric field, or by ultrasonic or sonic vibration, mechanical vibration, magnetic fields or combinations of the foregoing. Alternatively, the fluidization step can be carried out by mixing the powders with a suitable liquid, which could subsequently be removed by evaporation or ejected from the mold or sucked out of the mold. The uniform distribution of the powders within the mold cavity can alternatively be achieved by supplying the powder to the mold cavity in shrink wrapped bags which are tightly placed around the powdered materials. Such sacks would also serve to level the mold materials after compaction.

As in the powder feed system described above, the particulate material suitable for use in the present method can be any known or known particulate material (e.g., particles, flakes, fibers or a mixture of the above) to be used. to manufacture parts or components. Examples of such suitable materials include, but are not limited to, metal powders, non-metallic powders, intermetallic powders and compound powders.

The method of the present invention optionally includes weighing the particulate material before supplying it to the interior of the mold cavity. Such a method includes providing a quantity of particulate material and allowing it to flow at a first rate towards the weighing receptacle resting on the scale that records the weight of the particulate material. The flow velocity is reduced to a second speed when the scale registers a weight ranging from about one quarter to about three quarters of the predetermined weight, and, preferably, about half the predetermined weight. The flow of particulate material stops when the scale registers the constant weight. Then, the constant weight of particulate material is supplied to a feed receptacle that exactly matches the mold cavity. The upper part of the mold cavity is sealed with the upper die. Simultaneously with the passage of the supply pressure is generated inside the pressure vessel and into the feed receptacle, to push, from behind, the mass of particulate material into the mold cavity. As the pressure is generated and applied from behind, the particulate material moves, before the pressurized air, as a whole mass of material. Preferably, the amount of particulate material is supplied in a hopper having a valve associated with a lower portion of the hopper. The valve opens to allow the particulate material to flow at a certain rate from the hopper to the weighing receptacle that rests on the scale that records the weight of the particulate material. The valve closes partially when the scale registers a weight that fluctuates approximately between a quarter and three quarters of the constant weight, and preferably, when the weight is approximately half the constant weight. The valve closes completely when the piezoelectric element registers the constant weight.

Of course, this method may optionally include the step of fluidizing the particulate material within the mold cavity so as to distribute the particulate material with a uniform density throughout the mold cavity. The fluidization step can be carried out by applying any of the methods previously described herein.

As indicated, the method according to the present invention is especially suitable for producing, by means of alfaroli metallurgy, pieces having complex shape and strict dimensional tolerances. In these methods, the mold cavity has a shape corresponding to that of the piece. The exemplified parts that can be constructed using the present invention include, but are not limited to, watch windows, sprockets, worm gear, worm gear, stators cores, heat sink structures, automobile rods and armatures. for electric motors.

The powder feeding systems and methods according to the present invention can be adapted for use in any known manufacturing process with press for pulverized material, and its temperature can also be controlled as appropriate by, for example, insulation, heating with convection or induction, microwave systems or heat transfer methods that pump oil or hot water through pipes or coils. The described feeding systems and methods can also be used in many feeder processes.

In yet another embodiment, the present invention is directed to a press for pulverized material to build parts from particulate materials. The press for pulverized material according to the present invention includes the powder feed system described above for supplying particulate material to the cavity of a mold, plus a wear plate defining the mold table of the press for pulverized material. In the embodiments of the present invention incorporating shuttle, the shuttle of the feeding system receptacle is mounted below it on an upper surface of the wear plate. In embodiments that do not have a shuttle, there is an annular feed ring attached to the upper surface of the mold table or placed within the mold cavity and flush with the surroundings thereof. Alternatively, the annular ring floats around the upper die of the press for pulverized material and is suspended around said upper die.

In the following, the invention will be described more specifically with reference to the following non-limiting examples thereof.

Examples Example 1 A series of thirty 500-gram sprockets, shaped similar to the one shown in Figure 6, with a target height of 1.5 inches and a target diameter of 2. 7 inches, are produced using the present invention in accordance with the following: Powdered steel (Hoeganas 1000B mixed with carbon) is fed through a needle valve (Red Valve, Series 2600, 1"diameter) controlled by an electronic regulator (Norgren Electronic Regulator), at a speed of approximately 250 grams per second, to a scale resting on a piezoelectric element (Tedea Huntleigh Loadcell Model # 9010), when the piezoelectric element registers approximately 250 grams, the electronic regulator causes the needle valve to clog to reduce the feeding of the powder to the element piezoelectric The needle valve closes completely when the target weight (500 grams) is recorded in the piezoelectric element The piezoelectric element is connected to the electronic regulator, which is controlled by an analogue signal.The powder initially falls through the needle valve to a scale funnel that has a closed flapper valve controlled by a electromagnetic solenoid valve (Dormeyer Industries B24253-A-7). The funnel of the scale is attached to the piezoelectric element. The piezoelectric element controller is programmed with 500 grams of target weight per piece, as well as for slow feeding and intermittent weight. The solenoid valve opens causing the flapper valve to open for heavy dust to come out, and the flapper valve closes. The powders fall into a pressure vessel having a needle valve in its upper part, to open and close the container. The needle valve closes, thus sealing the access to the pressure vessel. The outlet of the pressure vessel is connected to a feed tube (bed of a carbon / Teflon compound with stainless steel coating SC8-608-608-66). The feed tube is connected at its most distant end to a receptacle of the ring-shaped feed system via a powder supply conduit attached thereto. Pressurized air is supplied to the pressure vessel by means of a pressure regulator regulated by a regulator (Norgren Electronic Pressure Regulator R26-200-RMLA) through a filter capable of filtering water and substances up to 5 microns in size, and then to through a coalescing filter capable of removing substances of only one size. The air rises to the electronic regulator (Norgren Air Pressure Regulator 11-018-110, with dial indicator for PSI) controlled by an analog signal. The air is exhausted through a filter and expelled through a cam valve (Norgren D1023H-CC1WA 3-Way Cam Valve). At the time of filling, the electronic regulator is programmed with the appropriate amount of pressure that is controlled by a controller (Norgren Air Pressure Regulator 11-018-110, with dial indicator for PSI). The upper punch of the pulverized material press descends to seal the upper part of the annular ring feed system receptacle, sealing the system effectively, and the controller opens and closes the cam valves allowing air to enter the duct. feeding and ejecting it from the feed ring. The powders settle to the bottom of the pressure vessel, and the cam valve that lets air into the pressure vessel opens and pushes the powders through the feed tube, into the annular receptacle of the feed system, and finally into the the mold cavity. The cam valve is in the closed position in the exhaust port of the annular feed system receptacle, thus allowing air to be expelled from the mold cavity. This exhaust hole is covered by a screen that is cleaned by forcing air through it in the opposite direction from which the air is expelled. The regulator lowers the pressure of the pressure generator to the fluidization pressure, and the powders that are in the mold are subsequently fluidized by the rapid supply and by the rapid exhausting of the pressure in and out of the mold cavity. The correct parameters for the process of this procedure are the following: Process: Feed the Powders into the mold cavity - 3 beats of 1 second at 55 PSI and exhausted for .09 seconds.

Fluidization - 8 pulses from .1 second to 10 PSI, and exhausted for .09 seconds.

Inner diameter of the feed tube 0.37".

After supplying the powders to the mold cavity, the powders are pressed between the upper die and the lower die of the press at a density of 6.9 g / cc in a 220 ton Cincinatti press, to build a sprocket with the following tolerances required for the part: Weight: +/- 0.6 grams (+/- 3 sigma) Height: +/- 0.0009 inches (+/- 3 sigma) concentricity: +/- 0.0009 inches (+/- 3 sigma) the concentricity tolerance of the tool is +/- 0.006 The concentricity, height and weight measurements are taken from the thirty (30) pieces produced in this way (the concentricity is measured using a Mitotoyo BenchCenter) and the results are reported in Table 1: Table 1 The concentricity measurements are plotted on a histogram shown as Figure 7, where the measurements are plotted against the frequency of occurrence. The number of samples that are within a range of concentricity values is grouped to show the variability of the concentricity with respect to the objective value.

Height measurements are plotted on a histogram shown as Figure 8, where the measurements are plotted against the frequency of occurrence. The number of samples that are within a range of height values is grouped to show the variability of the height with respect to the target value.

The weight measurements are plotted on a histogram shown as Figure 9, where the measurements are plotted against the frequency of occurrence. The number of samples that are within a range of weight values is grouped to show the variability of the weight with respect to the target value.

Example 2 Thirty pieces of 500 grams were produced according to the procedure described in Example 1, using the following parameters: Power Pulse: 3 beats from 1 second to 25 PSI, exhausted during. 09 seconds Fluidization: 8 pulses from 1 second to 12 PSI, exhausted for .09 seconds.

The height and weight of the pieces were measured, and the results are shown in Table 2: Table 2 The measurements of the height (in inches) of each of the thirty pieces, are plotted on a graph shown in Figure 10, which shows the minimum variations in the height of the pieces.

The weight measurements (in grams) of each of the thirty pieces are plotted on a graph shown in Figure 11. Each measurement is indicated on the graph as M. The area that is inside the bracket shows the variability expected when the Best Industrial Practice is used.

Example 3 Thirty pieces of 500 grams were produced according to the procedure described in Example 1, using the following parameters: Power Pulse: 3 beats of 40 PSI for 1 second, exhausted for .09 seconds.

Fluidization: 8 beats of 12 PSI for 1 second, exhausted for .09 seconds.

The concentricity of the resulting pieces was measured, and it was found to be the following: These concentricity values were plotted on a graph shown in Figure 12. The left side values were indicated with •. The values on the right side are indicated by B. The area below the bracket shows the area of the graph in which it is expected to fit the values obtained using the Best Industrial Practice.

The present invention can be realized in other specific forms, without departing from the spirit or essential characteristics thereof. Accordingly, the present embodiments should be considered, in all their aspects, as illustrative and not restrictive, the scope of the invention being indicated by the claims described at the end of it, more than by the previous specification, and all the changes that fall within the scope of the invention. within the meaning and range of equivalence of the claims, they are intended, therefore, to be included in them.

Claims (41)

What is claimed is:

1. A powder feed system for supplying a quantity of particulate material to the cavity of a mold of a press for pulverized material, said press for pulverized material having a plate surface in the form of a table, which is flush with a mold in the that the cavity of the mold is located, and that surrounds it; said mold cavity having an upper edge, an upper die attached to an upper ram, plus a lower die, said power supply system being constituted by the following: a receptacle for receiving and delivering particulate material to the cavity, said receptacle having an access through which the particulate material is received when pressed from behind, and an outlet that coincides exactly with the interior of the cavity and through which it is supplies the particulate material, under pressure, from a supply conduit to the cavity, said supply conduit being sealed, at a first end, to the receptacle access; at least one pressure generator sealed to an upper end of a pressure vessel, and being in open communication therewith, attached at a second end of said supply conduit, and said pressure generator supplies a pressure greater than atmospheric pressure to push the particulate material from the container, through the feed conduit and receptacle, into the mold cavity, and to optionally fluidize the particulate material that is inside the mold cavity, to create a density distribution, substantially uniform, of the particulate material within the cavity, and at least one exhaust hole to release the pressure from inside the mold cavity.

2. The pressurized powder supply system according to claim 1, wherein at least one exhaust hole is located in the receptacle.

3. The pressurized powder delivery system according to claim 1, wherein at least one exhaust hole is located in the pressure vessel.

4. The pressurized powder supply system according to claim 1, wherein the receptacle has an annular shape and includes an annular receptacle body that surrounds and defines an interior space, said receptacle body having an upper and lower side, and sealingly connected, on its lower side, to the surface of the mold, so that the. The body of the annular receptacle surrounds the upper edge of the mold cavity, and the interior space is contiguous with the cavity.

5. The pressurized powder supply system according to claim 1, wherein the receptacle is annular in shape and includes an annular receptacle body surrounding and defining the cavity of the mold, said receptacle body having an upper and a lower side, and being positioned such that the upper side of the receptacle body is flush with the surface of the mold.

6. The pressurized powder delivery system according to claim 1, wherein the receptacle is annular in shape and includes an annular receptacle body surrounding and defining an interior space through which the upper punch passes, said receptacle body having a lower surface for making sealed contact with the surface of the mold, and an upper surface to which it is movably attached and suspended from the upper ram.

7. The pressurized powder delivery system according to claim 1, wherein the receptacle is the upper die.

8. The pressurized powder supply system according to claim 1, wherein the receptacle is the lower die.

9. The pressurized powder supply system according to claim 1, wherein the receptacle is box-shaped and the access is a top access, and the outlet is a lower exit, and which further includes a mobile shuttle attached to said receptacle for selectively moving said receptacle in a horizontal plane raised above a position and transverse thereto, whereby the lower outlet protrudes from said cavity of the mold, and for moving said body of the feeding system in a downward direction to match exactly said lower outlet with the mold cavity.

10. The pressurized powder delivery system according to claim 1, further including a scale juxtaposed between the receptacle of the feed system and a source of particulate material, and said scale weighs the amount of particulate material before the same be supplied to the mold cavity.

11. The pressurized powder supply system according to claim 10, wherein said scale is constituted by a scale container that receives a quantity of particulate material from a lower end of a hopper that receives a quantity of particulate material, having said Scale container at least one lower outlet opening for releasing the particulate material towards said pressure vessel, said scale container having an upper edge having at least two support points located therein, a support brace elongate suspended and joined at its end closest to each of the at least two said support points, and joined at its most distant end to a transverse bar; and a piezoelectric element on which said transverse bar rests, said piezoelectric element having a signal transmitter that sends signals to a controller to open and close a valve associated with said discharge opening of said hopper.

12. A pressurized powder supply system for supplying a quantity, by weight, of particulate material to the cavity of a mold of a press for pulverized material, said supply system being constituted by the following: a hopper receiving a quantity of particulate material, said hopper having a discharge opening at its lower end, a valve associated with the discharge opening, said valve having an open position and a closed position; a scale container that receives a quantity of particulate material from said lower end of said hopper when said valve is in said open position, said scale container having at least one exit opening for releasing the particulate material it contains, said container of the scale an upper edge with at least two support points located therein, an elongated support strut suspended and joined, at its closest end, to each of said at least two support points, and joined at its most distant end, to a transverse bar; a pressure vessel having an obturable upper opening located directly below said lower outlet opening, for receiving the particulate material from said lower outlet opening, and a lower opening sealingly connected to a supply conduit, the supply conduit being sealed connected to the interior of a supply receptacle, and in open communication therewith, for supplying powder thereto; a pressure generator sealed to said pressure vessel for supplying a pressure, greater than atmospheric pressure, into said mold cavity, wherein said mold cavity is constituted by the following; a piezoelectric element on which said transverse bar rests, said piezoelectric element having a signal transmitter that sends signals to a controller to open and close said valve associated with said discharge opening of the hopper.

13. A method for creating a distribution, with uniform density, of a quantity of particulate material located within a mold cavity of a press for pulverized material, which includes the following steps: supplying a quantity of particulate material to said mold cavity, fluidizing the particulate material within said mold cavity, to evenly distribute the particulate material, so that it has a substantially uniform density throughout the mold cavity.

14. The method according to claim 13, wherein the particulate material is selected from a group consisting of metallic powders, non-metallic powders, intermetallic powders and compound powders.

15. The method according to claim 13, wherein the step of fluidion includes sealing the mold cavity to the atmosphere, and then applying a series of pulsations, or at least one, into the interior of the mold cavity, each pulsation includes supplying a pressure, higher than atmospheric pressure, to the mold cavity, and then exhausting the pressure from inside the mold cavity.

16. The method according to claim 15, wherein the pressure pulsations can be at least one, or a series of approximately 2 to 100.

17. The method according to claim 15, wherein each of said pressure pulsations includes supplying pressure to the mold cavity in the amount of about 1 psi to about 150 psi, for a lapse of time of approximately 10 seconds, and exhaustion the pressure, at least once, during a lapse of time of approximately x seconds.

18. The method according to claim 15, wherein each of said pressure pulsations includes supplying pressure to the mold cavity in the amount of about 1 psi to about 150 psi, for a lapse of time from about .01 seconds to about 60 seconds, and exhaust the pressure, at least once, for a period of time from about .01 seconds to about 60 seconds.

The method according to claim 15, wherein the series of pressure pulsations is from about 2 to about 100 pressures of pressure, and each of said pressure pulsations includes supplying pressure to the mold cavity by an amount of about 1 psi at about 150 psi, for a period of time from about .01 seconds to about 60 seconds, and exhausting the pressure, at least once, for a lapse of time from about .01 seconds to about 60 seconds.

20. The method according to claim 13, wherein the step of fluidion includes a series of applications, or at least one, of an element selected from a group consisting of electric fields, magnetic fields, ultrasonic vibration, sonic vibration, vibration. mechanical, liquid fluidion or a combination of the above.

21. The method according to claim 13, wherein the pressure above atmospheric pressure is also applied during the supply step, to push particulate material, from behind, as a mass towards the mold cavity, and said pressure is about 1 psi at approximately 150 psi, applied for a period of time from approximately .01 seconds to approximately 60 seconds.

22. A method for supplying a quantity of particulate material to the cavity of a mold of a press for pulverized material, such that said particulate material has a uniform density throughout the mold cavity, said method including the following steps: generate a pressure higher than the atmospheric pressure, behind the particulate material, using the pressure higher than atmospheric pressure, to push the particulate material through a feed receptacle having an outlet that exactly matches the cavity of the mold and that opens towards it, in said cavity of the mold; Y fluidizing the particulate material within said mold cavity to evenly distribute the particulate material, so as to have a substantially uniform density throughout the mold cavity.

23. The method according to claim 22, wherein the pressure used to push the particulate material into the mold cavity is from about * 1 psi to about 150 psi, and the duration of the pressure generation step is about. 01 seconds to approximately 60 seconds.

24. The method according to claim 22, wherein the step of fluidion includes exhausting the pressure used to push the particulate material into the mold cavity, from the mold cavity, into a series of pulsed exhausts, or at least one .

25. The method according to claim 24, wherein the series includes from about 2 to about 100 pulsed exhausts, and each of the pulsed exhausts lasts from about .01 seconds to about 60 seconds.

26. The method according to claim 22, wherein the step of fluidization includes applying a series of pressure pulsations, or at least one, to the interior of the mold cavity, each of said pressure pulsations including supplying a pressure , higher than the atmospheric pressure in the mold cavity, and then exhausting the pressure from inside the mold cavity.

27. The method according to claim 26, wherein the pressure pulsations can be from 1 to about 100 pressures of pressure.

28. The method according to claim 26, wherein each 1 of said pressure pulsations includes supplying pressure to the mold cavity by an amount of about 1 psi to about 150 psi, for a lapse of time from about .01 seconds to about 60 seconds, and exhaust the pressure with a series of exhaust periods, or at least one, each of said exhaustion periods lasting a lapse of time from approximately .01 seconds to approximately 60 seconds.

29. The method according to claim 26, wherein the series of pressure pulsations includes from 1 to about 100 pressure pulsations, and each of said pressure pulsations includes supplying pressure to the mold cavity in an amount of approximately 1 psi. at approximately 150 psi, for a lapse of time from approximately .01 seconds to approximately.60 seconds, and exhaust the pressure with a series of, or at least one, exhaust periods lasting a period of approximately .01 seconds to approximately 60 seconds.

30. The method according to claim 22, wherein the step of fluidization includes a series of applications, or at least one, of an element selected from the group consisting of electric fields, magnetic fields, ultrasonic vibration, sonic vibration, vibration. mechanical, liquid fluidization or a combination of the above.

31. The method according to claim 22, further including the step of weighing said particulate material before being delivered into the mold cavity.

32. A method for uniformly supplying a constant weight of particulate material in the mold cavity, which includes the following steps: supply a quantity of particulate material, allowing said particulate material to flow at a first speed towards a weighing receptacle that rests on a scale, to record the weight of the particulate material; reducing said flow to a second speed when the scale registers a weight that is approximately one quarter to about three quarters of the predetermined weight; stop said flow when the scale registers the constant weight; Y generating pressure within the pressure vessel to push the constant weight of particulate material into the mold cavity, through a feed receptacle that exactly matches the mold cavity.

33. The method according to claim 32, further including the following steps: supplying the amount of particulate material in a hopper having a valve associated with a lower portion thereof; and opening said valve to allow said particulate material to flow with velocity from the hopper to the weighing receptacle that rests on the scale and records the weight of the particulate material, partially closing said valve when the scale registers a weight that is approximately a quarter to approximately three quarters of the constant weight and Completely close said valve when the piezoelectric element registers the constant weight.

34. The method according to claim 32, further including the step of fluidizing the particulate material within the mold cavity to distribute particulate material with a uniform density throughout the mold cavity.

35. The method according to claim 34, wherein the step of fluidizing the particulate material within the mold cavity is carried out by exhausting the pressure that was used to push the particulate material into the mold cavity, from inside the cavity. of the mold, said exhaust being carried out by means of a series of exhaust pulsations, or with at least one.

36. The method according to claim 34, wherein the step of fluidizing the particulate material within the mold cavity is carried out by applying a series of pressure pulsations, or at least one, inside the mold cavity. , each of said pressure pulsations including supplying a pressure, higher than the atmospheric pressure, in the mold cavity, and then exhausting the pressure from inside the mold cavity.

37. A method to produce a piece of complex shape and dimensional and rigorous tolerances by powder metallurgy, which includes the following: providing a mold cavity having a shape corresponding to that of the piece; generating pressure from behind a powder feed receptacle, which exactly matches the mold cavity, to push the particulate material through the receptacle and into the mold cavity; fluidizing the particulate material within the mold cavity, to evenly distribute the particulate material to a uniform density, throughout the mold cavity; Y compressing said particulate material within said mold cavity, to cause said particulate material to agglomerate and thereby produce said piece.

38. The method according to claim 37, wherein the step of fluidizing the particulate material within the mold cavity is carried out by exhausting the pressure used to push the particulate material into the mold cavity, from inside the mold cavity. , said exhausting being carried out by means of a series of exhaust pulsations or at least one.

39. The method according to claim 37, wherein the step of fluidizing the particulate material within the mold cavity is carried out by applying a series of pressure pulsations, or at least one, inside the mold cavity. , each of said pressure pulsations including supplying a pressure, higher than atmospheric pressure, in the mold cavity, and then exhausting the pressure from inside the mold cavity.

40. The method according to claim 37, wherein the step of fluidization is carried out by applying to the cavity of the mold a series of selected elements, or at least one, of the group consisting of electric fields, magnetic fields, sonic vibration , ultrasonic vibration, mechanical vibration, liquid fluidization or a combination of the foregoing, said application causing the particulate material to behave like a fluid and, consequently, uniformly distribute the particulate material throughout the mold cavity.

41. The method according to claim 37, wherein said piece can be a member of the group consisting of clock windows, cogwheels, helical gears, worm gears, stator cores, heat sinks, automobile rods, heat sinks, heat, automobile rods, and induced for electric motors.