BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The invention relates in general to a method and apparatus for fluidizing particulate material during delivery to and filling cavities in a uniform and consistent manner during successive filling operations. The invention relates in particular to powder delivery systems for delivering particulate material and filling closed cavities, such as die cavities of die-casting machines, and for filling open cavities, such as containers on food packaging production lines.  
           [0003]    2. Description of the Related Art  
           [0004]    Powder delivery systems are used for delivering particulate material and filling die cavities of, e.g., die-casting machines prior to powder compaction in processes for fabricating consolidated part for automotive, aerospace, micro-electronics, pharmaceuticals, vitamins, etc. Powder typically is gravity-fed from a main hopper to the die cavity by transfer through a flexible tube to a feedshoe or fillshoe, which deposits powder into the die cavity. The process of depositing powder in the die cavity is called “die filling.” 
           [0005]    The process of powder delivery and filling by gravity is the most common way of delivering powder and filling a die cavity. The feedshoe is pushed forward between the surface of the die cavity and a top punch, and positioned on top of the die cavity. Depending on powder flow characteristics, cavity shape and size, type of die-casting machine, and filling method, the feedshoe is typically mechanically vibrated while on top of the die cavity to loosen the powder, break any clumps and ensure that the die cavity is full before the feedshoe is retracted.  
           [0006]    There are several problems associated with prior art processes for powder delivery and filling of a die cavity.  
           [0007]    One such problem is variation in filling conditions during successive filling operations, i.e., from part to part. Variations in filling conditions from part to part result in variations in weight from part to part, and non-uniform fill of the die cavities. A non-uniform fill results in variations in density between the front and back of the part and in distortion of the part during sintering. Typically, part specifications include limits on acceptable variations in part weight and on acceptable variations in density within the part. Parts that do not meet the specifications are rejected.  
           [0008]    The variations in filling conditions from part to part are due, in part, to variations in head pressure, clumping, surge, and dead zones of material within the feedshoe. The head pressure is due to the powder in the feedshoe, the flexible tube and the main hopper. As a result of the powder delivery system design, wherein the flexible tube is typically connected to the backside of the feedshoe, the powder in the back of the die cavity is subjected to a higher head pressure than the front of the die cavity.  
           [0009]    During operation, the feedshoe is pushed forward and centered above the die cavity and then retracted before compacting. The movement of the feedshoe across the die cavity results in the back of the die cavity being subjected to the higher head pressure for a longer period of time than the front of the die cavity. These effects combine to produce variations in part density between the back and the front of the part, which result in distortion during sintering.  
           [0010]    Clumping and surge of the powder within the feedshoe and flexible tube contributes to non-uniform filling of die cavities. Mechanical shaking of the feedshoe above the die cavity can break clumping in the powder and improve fill uniformity but is not consistent during successive filling operations.  
           [0011]    A further problem results from fine powders/particulate materials, which do not have good flow characteristics, thus posing a serious problem for the die filling operation. Lubricants are added to reduce interparticle friction and improve flowability, thereby requiring an energy intensive delubing cycle after compacting to remove all added lubricants.  
           [0012]    A further problem is that mechanical shaking of the feedshoe causes segregation of fine powders/particulate materials from coarse powders/particulate materials resulting in a loss of uniformity in particle size distribution and chemical composition. This powder segregation results in powders with different apparent densities and chemical composition being filled in the die cavity during successive powder filling operations.  
           [0013]    A solution to these and other problems is needed. Such solution is provided by the novel invention recited herein.  
         BRIEF SUMMARY OF THE INVENTION  
         [0014]    The invention contemplates supplying a technique and apparatus for delivering particulate material and filling cavities in a uniform and consistent manner during successive filling operations. In preferred embodiments, the invention provides a powder delivery system for delivering particulate material and filling closed cavities, such as the closed die cavities of die-casting machines; or for filling open cavities, such as open containers on food packaging production lines.  
           [0015]    Die Casting and Sintering  
           [0016]    The three basic steps for producing parts by the press and sinter process are mixing, compacting and sintering. In step one, mixing, elemental or prealloyed powders are mixed with lubricants or other alloy additions to produce a homogeneous mixture of ingredients. The lubricant reduces interparticle friction and improves the flow characteristics of the powder mixture. In step two, compacting, mixed powder is fed into a precision die on a die-casting machine and is compacted. Compacting the loose powder produces a “green compact” which has the size and shape of the finished part when ejected from the die. In step three, sintering, the green compacts are placed on a wide-mesh belt and slowly moved through a controlled atmosphere furnace. The parts are heated to below the melting point of the base material, held at the sintering temperature, and then cooled.  
           [0017]    Tabletting and Dry Compaction  
           [0018]    The production of pharmaceutical preparations, e.g., vitamins, or tablets containing an active medicament in a carrier or other suitable excipient, requires precise and homogeneous mixation techniques. Similarly, candies usually must have an acceptable hardness, mouthfeel, and duration within the mouth. These characteristics can depend in part upon the homogeneity of the composition in the tablet form.  
           [0019]    Dry powder, or a semidry paste, is placed within a tablet mold and subjected to pressure. The amount of pressure usually determines the hardness of the tablet, and consequently its lifetime within the mouth (subject, of course, to chewing). It is important for dosage amount and appearance that the powder feed correctly into the tabletting machine.  
           [0020]    The Closed Cavity Device  
           [0021]    In one embodiment, the invention provides a method and apparatus for powder delivery and filling of a closed cavity, such as a die cavity of a die-casting machine. The apparatus includes a mini-hopper, a transport device, a delivery chute and a gas control unit.  
           [0022]    The mini-hopper has a porous distributor plate for partitioning the mini-hopper into a first partition in which the bed of particulate material is stored and a second partition separate from the first partition and in communication with the first partition via the porous distributor plate. An inlet port is provided for receiving a compressed gas in the second partition at a low pressure, whereby only the bottom surface of the bed of particulate material becomes fluidized by migration of the compressed gas through the porous distributor plate and into the first partition.  
           [0023]    The transport is connected to the side of the mini-hopper and delivers powder/particulate material from the mini-hopper to the delivery chute. The transport has a porous distributor plate for partitioning the transport into a first partition in which the particulate material flows and a second partition separate from the first partition and in communication with the first partition via the porous distributor plate.  
           [0024]    The delivery chute can function as the powder discharge unit directly above the die cavity. Fluidizers are embedded in the delivery chute to ensure that powder is fluidized before filling the die cavity. The delivery chute is customized to part shape to optimize fill performance for individual parts or a family of parts, depending on part size and shape complexity.  
           [0025]    An in-line dryer may be provided to remove moisture from the gas supply, while an in-line filter may be used to remove solid impurities in the gas supply. The gas control unit can include three independent pressure regulators, located in a separate housing, and three pneumatic solenoids, which are used to regulate the flow of gas to each segment of the fillshoe independently. The solenoids are preferably timed to control fluidization of the powder over the die cavity.  
           [0026]    The apparatus in one embodiment provides for venting of gas in each segment of the fillshoe to prevent build up of pressure within the system and in the die cavity, which will prevent uniform, complete and consistent filling of die cavities. The apparatus also preferably provides for collection of any fine powder particles that may escape through the venting screens.  
           [0027]    The apparatus in a particularly preferred embodiment has a low profile, fits on a compacting press, and can be pushed into position between the die surface and top punch of a die-casting machine during die filling operation.  
           [0028]    The apparatus for filling closed cavities is preferably easily movable. The apparatus is pushed forward into position above a die cavity for filling and then retracted after filling and before compacting. The low profile apparatus for filling closed cavities can be positioned between the die surface and top punch of a die-casting machine.  
           [0029]    The Open Cavity Filling Device  
           [0030]    The invention, in another preferred embodiment, provides a method and apparatus for powder delivery and filling of an open cavity, such as a container on food packaging production lines. The apparatus for filling open cavities is preferably stationary, although it may be moved for adjustment purposes or to accommodate packagings of various sizes on a continuous production line.  
           [0031]    The apparatus in one embodiment includes a mini-hopper, a transport, a delivery chute and a gas control unit.  
           [0032]    The mini-hopper can function as an intermediate storage unit for powder and is configured to receive powder from the main hopper. The mini-hopper has specially designed porous distributor plates for partitioning the mini-hopper into a first partition in which the bed of particulate material is stored and a second partition separate from the first partition and in communication with the first partition via the porous distributor plate.  
           [0033]    An inlet port is provided for receiving a compressed gas in the second partition at a low pressure, whereby only a layer of particulate material next to the porous distributor plates becomes fluidized by migration of the compressed gas through the porous distributor plates and into the first partition.  
           [0034]    The transport delivers powder/particulate material from the mini-hopper to the delivery chute. The transport has a porous distributor plate for partitioning the transport into a first partition in which the particulate material flows and a second partition separate from the first partition and in communication with the first partition via the porous distributor plate. An inlet port is provided for receiving a compressed gas in the second partition at a low pressure, whereby only the bottom layer of the particulate material becomes fluidized by migration of the compressed gas through the porous distributor plate and into the first partition.  
           [0035]    The delivery chute preferably has a center fluidizer which is used to regulate powder flow and meter the amount of powder. This can be accomplished, e.g., by the use of a timer and turning the gas flow on and off. The delivery chute can act as a fluidized powder valve by preventing powder flow once the gas is turned off.  
           [0036]    The gas control unit is used to control the gas moisture content and regulate powder fluidization and powder flow in relation to the movement of the production/filling line.  
           [0037]    In a preferred embodiment, an in-line dryer removes moisture from the gas supply. An in-line filter is also preferably used to remove solid impurities in the gas supply. The gas control unit is used to control the gas moisture content and regulate powder fluidization in relation to the movement of the production line.  
           [0038]    The gas control unit in one embodiment includes three independent pressure regulators, located in a separate housing, and three pneumatic solenoids, which are used to regulate the flow of gas to each segment of the fillshoe independently. The solenoids are timed to control fluidization of the powder over the open container on a production line. When the gas to the fluidized powder valve is turned on, particulate material flows into the open container. When the gas to the fluidized powder valve is turned off, the flow of particulate material is cut-off immediately.  
           [0039]    A timer is preferably used to regulate the time at which the gas to the fluidized powder valve is turned on and off, providing an accurate way of metering particulate material for filling a container or an open cavity.  
         OBJECTS OF THE INVENTION  
         [0040]    It is therefore an object of this invention to provide a new method and apparatus for powder filling of a die cavity.  
           [0041]    It is a further object of this invention to provide an apparatus with a low profile that can be fitted on a die-casting machine between the die surface and the top punch of the die-casting machine.  
           [0042]    It is a further object of the invention to provide a method and apparatus for powder delivery and consistent filling of a die cavity from the feedshoe during successive filling operations.  
           [0043]    It is a further object of the invention to provide a method and apparatus for powder delivery and consistent filling of a die cavity which improves uniformity of fill of the die cavity from the feedshoe.  
           [0044]    It is a further object of the invention to provide a method and apparatus for powder delivery to a die cavity which reduces or eliminates segregation of fine particles from coarse particles and which maintains uniformity in chemical composition.  
           [0045]    It is a further object of the invention to provide a method and apparatus for powder delivery and filling of a die cavity which enhances the flowability of fine powders/particulate materials.  
           [0046]    It is a further object of the invention to provide a method and apparatus for powder delivery and filling of a cavity for forming tablets, which apparatus enhances the flowability of fine powders/particulate materials.  
           [0047]    It is a further object of the invention to provide a method and apparatus for powder delivery and filling of a die cavity which reduces or eliminates the need for using organic binders to adhere the fine particles with the coarse particles to prevent particle segregation.  
           [0048]    It is a further object of the invention to provide a method and apparatus for powder delivery to a die cavity, which minimizes or eliminates the need to use a lubricant.  
           [0049]    The foregoing and other objects, features, and advantages of the invention will be apparent to the skilled artisan having regard for this disclosure. The examples which follow are intended to serve as illustrative and not by way of limitation. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0050]    [0050]FIG. 1A shows a cross-sectional view of an exemplary apparatus for filling closed cavities according to a preferred embodiment.  
         [0051]    [0051]FIG. 1B is a schematic diagram of an exemplary apparatus for a gas control unit of an apparatus for filling closed die cavities.  
         [0052]    [0052]FIG. 2A is a top plan view of an examplary delivery chute design with multiple fluidizers or pedals.  
         [0053]    [0053]FIG. 2B is a cross-sectional view of an exemplary chute design with multiple fluidizers or pedals.  
         [0054]    [0054]FIG. 2C is a cross-sectional view of an individual fluidizer.  
         [0055]    [0055]FIG. 3 is a cross-sectional view of another exemplary delivery chute design with a ring fluidizer.  
         [0056]    [0056]FIG. 4A is a cross-sectional view of another preferred embodiment of a delivery chute design with a ring fluidizer and a center fluidizer illustrating a gas off condition whereby the chute functions as a passive valve (powder locks when gas is off.  
         [0057]    [0057]FIG. 4B is a cross-sectional view of the embodiment of FIG. 4A illustrating the gas on condition whereby the delivery chute functions as a passive valve (powder flows when gas is on).  
         [0058]    [0058]FIG. 5A is a cross-sectional view of an embodiment of the invention configured for filling open cavities, showing the powder lock when the gas is off.  
         [0059]    [0059]FIG. 5B is a cross-sectional view of an embodiment of the invention configured for filling open cavities, showing the powder flowing when the gas is on.  
         [0060]    [0060]FIG. 6 is a cross-sectional view of an embodiment of the invention configured for filling open cavities with powders with good flow characteristics.  
         [0061]    [0061]FIG. 7 is a cross-sectional view of an embodiment according to the invention for filling open cavities with powders with poor flow characteristics.  
         [0062]    [0062]FIG. 8 is a cross-sectional view of a fluidized in-line connector according to the present invention to assist the flow of powders with poor flow characteristics. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0063]    The following description of preferred embodiments is meant to be read in conjunction with the accompanying drawings, in which reference characters refer to the same parts throughout the various views. The drawings are not necessarily to scale, emphasis instead is being placed upon illustrating principles of the invention. The drawings serve merely to illustrate the invention, and are not meant to limit it in scope in any way.  
         [0064]    The present invention provides a method and apparatus for powder delivery and filling of cavities in general, said cavities being used for sintering, casting, die casting, tabletting, or other forms of powder use including metallurgy, or other industrial, manufacturing, distributing, or other uses. For ease of description, the below occasionally references a preferred embodiment, pressing and sintering, but it is clear to the skilled artisan that many uses for the instant invention will be apparent without departing from the spirit and claims of the instant disclosure.  
         [0065]    Powder Processes Generally  
         [0066]    There are three basic steps for producing parts by a technique of pressing, or pressing and sintering.  
         [0067]    Initially, the components of the composition to be made into a part are mixed. Mixing should be uniform to ensure that the resultant part has a homogeneous structure and no large agglomerations of particles or voids are present. The components may be powders, granules, prealloyed particulates, particles made by any of several known techniques—air atomization, water atomization, or the like.  
         [0068]    The components may be uniform or irregular; in any event the primary object is to ensure a uniform dispersion, while mixing and also while being transported to the die casting machine. In this step, mixing, elemental or prealloyed powders may be mixed with lubricants or other alloy additions to produce a homogeneous mixture of ingredients. The lubricant reduces interparticle friction and improves the flow characteristics of the powder mixture.  
         [0069]    The powder or the like is then subjected to compacting, wherein mixed powder is fed into a rough cut or precision die on a die-casting, tabletting, or other machine and is compacted. Compacting the loose powder produces a “green compact” which has the size and shape of the finished part when ejected from the die. It is important that the component powder subjected to the compaction is uniformly distributed in the die or mold and homogeneous. If a tablet is being produced, this is frequently the last step if no further processes are necessary, e.g. coating or the like.  
         [0070]    During sintering, the so-called “green compacts” are placed on a wide-mesh belt and slowly moved through a controlled atmosphere furnace. The parts are heated to below the melting point of the base material, held at the sintering temperature, and then cooled.  
         [0071]    Other forms of metallurgy, e.g. the production of various alloys; or the production of ceramic metal (cermet) materials, require a similarly homogeneous dispersion of materials within a binder, lube, other carrier, or no carrier. The apparatus and method of the instant invention ensures such a dispersion.  
         [0072]    The Closed Cavity Apparatus and Process  
         [0073]    In one version of the invention, the cavity to be filled is a closed cavity, such as a die cavity of a die-casting machine or the tablet forming plate of a tabletting machine.  
         [0074]    The apparatus contains a mini-hopper, a transport device, a delivery chute and a gas control unit. The mini-hopper may function as an intermediate storage unit for powder and is configured to receive powder from the main hopper. The mini-hopper provides isolation of the fillshoe from the main powder hopper and regulates powder pressure head during the filling operation.  
         [0075]    The mini-hopper has a porous distributor plate for partitioning the mini-hopper into a first partition in which the bed of particulate material is stored and a second partition separate from the first partition and in communication with the first partition via the porous distributor plate.  
         [0076]    An inlet port is provided for receiving a compressed gas in the second partition at a low pressure, whereby only the bottom surface of the bed of particulate material becomes fluidized by migration of the compressed gas through the porous distributor plate and into the first partition.  
         [0077]    The transport is connected to the side of the mini-hopper and delivers powder/particulate material from the mini-hopper to the delivery chute. The transport has a porous distributor plate for partitioning the transport into a first partition in which the particulate material flows and a second partition separate from the first partition and in communication with the first partition via the porous distributor plate.  
         [0078]    The delivery chute may function as the powder discharge unit directly above the die cavity. Fluidizers are preferably embedded in the delivery chute to ensure powder is fluidized before filling the die cavity. The delivery chute is customized to part shape to optimize fill performance for individual parts or a family of parts, depending on part size and shape complexity.  
         [0079]    For example, one center fluidizer is used for large ring-shaped parts, and functions as a passive (no moving component) powder valve when the gas is turned on and off. Several small fluidizers are used for gear-shaped parts, and are positioned above gear lightening holes. A ring fluidizer is used for powders with poor flow characteristics and to increase fill speed.  
         [0080]    The gas control unit is used to control the gas moisture content and regulate powder fluidization in relation to the movement of the fillshoe on the die-casting machine. An in-line dryer preferably removes moisture from the gas supply, and preferably an in-line filter is used to remove solid impurities in the gas supply.  
         [0081]    In this embodiment, the gas control unit includes three independent pressure regulators, located in a separate housing, and three pneumatic solenoids, which are used to regulate the flow of gas to each segment of the fillshoe independently. The solenoids are timed to control fluidization of the powder over the die cavity.  
         [0082]    The apparatus provides for venting of gas in each segment of the fillshoe to prevent build up of pressure within the system and in the die cavity, which will prevent uniform, complete and consistent filling of die cavities. The apparatus also provides for collection of any fine powder particles that may escape through the venting screens. The apparatus has a low profile, fits on a compacting press, and can be pushed into position between the die surface and top punch of a die-casting machine during die filling operation.  
         [0083]    The Open Die or Container Apparatus and Process  
         [0084]    The invention also provides a method and apparatus for powder delivery and filling of an open cavity, such as a container on food packaging production lines.  
         [0085]    The apparatus in this embodiment likewise consists of a mini-hopper, a transport, a delivery chute and a gas control unit.  
         [0086]    The mini-hopper again may function as the intermediate storage unit for powder and receives powder from the main hopper. The mini-hopper has specially designed porous distributor plates for partitioning the mini-hopper into a first partition in which the bed of particulate material is stored and a second partition separate from the first partition and in communication with the first partition via the porous distributor plate.  
         [0087]    An inlet port is provided for receiving a compressed gas in the second partition at a low pressure, whereby only a layer of particulate material next to the porous distributor plates becomes fluidized by migration of the compressed gas through the porous distributor plates and into the first partition. The special design for the porous plates is required because of the very poor flow characteristics of food, vitamins, and similar products.  
         [0088]    The transport device delivers powder/particulate material from the mini-hopper to the delivery chute. The transport device has a porous distributor plate for partitioning the transport into a first partition in which the particulate material flows and a second partition separate from the first partition and in communication with the first partition via the porous distributor plate.  
         [0089]    An inlet port is provided for receiving a compressed gas in the second partition at a low pressure, whereby only the bottom layer of the particulate material becomes fluidized by migration of the compressed gas through the porous distributor plate and into the first partition.  
         [0090]    The delivery chute has a center fluidizer which is used to regulate powder flow and meter the amount of powder with the use of a timer and turning the gas flow on and off. The delivery chute acts as a fluidized powder valve.  
         [0091]    The gas control unit is used to control the gas moisture content and regulate powder fluidization and powder flow in relation to the movement of the production/filling line. Preferably, an in-line dryer removes moisture from the gas supply and an in-line filter is used to remove solid impurities in the gas supply.  
         [0092]    The gas control unit in this embodiment is used to control the gas moisture content and regulate powder fluidization in relation to the movement of the production line. The gas control unit includes three independent pressure regulators, located in a separate housing, and three pneumatic solenoids, which are used to regulate the flow of gas to each segment of the fillshoe independently.  
         [0093]    The solenoids are timed to control fluidization of the powder over the open container on a production line. When the gas to the fluidized powder valve is turned on, particulate material flows into the open container. When the gas to the fluidized powder valve is turned off, the flow of particulate material is cut-off immediately. A timer is used to regulate the time at which the gas to the fluidized powder valve is turned on and off, providing an accurate way of metering particulate material for filling a container or an open cavity.  
         [0094]    Detailed Description with Reference to the Drawings  
         [0095]    In the following description, the following definitions and explanations apply.  
         [0096]    A closed die cavity refers to an embodiment set up such that there is no gap or open space between the apparatus for powder/particulate material filling and the die cavity receiving the powder/particulate material.  
         [0097]    A fillshoe is a device to which powder/particulate material is delivered in order that the die cavity or other mold may be filled.  
         [0098]    In use, the fillshoe is held tight against the die surface (no gap is allowed) and the powder/particulate material is dropped into the die cavity.  
         [0099]    To accomplish this action, the fillshoe moves in a translatory motion (back and forth) above the die cavity and therefore is size limited such that it fits between the die surface and the top punch of a die-casting machine during the fill operation.  
         [0100]    With particular reference to FIGS. 1A and 1B, a powder delivery and filling system includes a mini-hopper  10 , a transport device  12 , a delivery chute  14  and a gas control unit  16 . The mini-hopper  10  has a porous distributor plate  18  for partitioning the mini-hopper into a first partition  20  in which the bed of particulate material is stored and a second partition  22  separate from the first partition and in communication with the first partition via the porous distributor plate  18 .  
         [0101]    An inlet powder port  24  is provided for receiving powder mixture/particulate material in the first partition  20 . The inlet powder port  24  is connected to the main hopper  26  with a flexible tube  28 . The powder flows from the main hopper  26 , through the flexible tube  28 , through the inlet powder port  24  into a leveling pipe  30 , and thence into the first partition  20  of the mini-hopper  10 .  
         [0102]    When the powder level in the mini-hopper  10  reaches the base of the leveling pipe  30  the powder forms a lock, powder flow stops and the powder level remains constant. The powder flow resumes to refill the mini-hopper  10  as soon as sufficient powder is discharged from the apparatus into the die cavity  32 .  
         [0103]    As such, no metering of the powder into the mini-hopper  10  is required and the powder level in the mini-hopper  10  fluctuates somewhat during the filling operation. It is preferred that the amount of powder stored in the mini-hopper  10  should be equivalent to at least 5 times the amount of powder required to fill the die cavity  32 , thus assuring a constant flow.  
         [0104]    An inlet port  34  is provided for receiving a compressed gas in the second partition  22 . The porous distributor plate  18  ensures uniform transmission of gas pressure to all sections of the mini-hopper  10 . The mesh size of the porous distributor plate  18  depends on the particle size distribution of the powder/particulate material, and is chosen to prevent clogging by entrapment of the small particles within the pores.  
         [0105]    The mesh material is preferably stainless steel to provide high strength, good wear properties and good weldability, and non-corrosive behavior. Other materials may be used as well. The powder in the mini-hopper  10  is loosened by migration of the compressed gas through the porous distributor plate and into the first partition of the mini-hopper  10 , and depending on the applied gas pressure the powder can become fluidized.  
         [0106]    The bottom surface of powder in the mini-hopper  10  is loosened first and, as the pressure of applied gas rises becomes fluidized. As the amount of pressure is increased, all powder in the mini-hopper  10  can be fluidized. The amount of fluidization is controlled by regulating the gas pressure to the inlet gas port  34 .  
         [0107]    The proper regulation of the applied gas pressure and flow is important to the proper performance of the fill system. In the most preferred embodiment of this invention, only the bottom surface (or thin layer) of powder is loosened or fluidized. This layer will then provide a “gas bearing” which reduces friction and increases powder flow rate.  
         [0108]    The gas pressure used depends on the powder characteristics and should be kept at a minimum. Metal powders typically used in the powder metallurgy industry have admixed lubricants and can be characterized as having good flow characteristics. For these powders the applied gas pressure used in the first partition of the mini-hopper  10  is less than 5 psi, typically around 2 psi.  
         [0109]    For fine powders with poor flow characteristics, the magnitude of the applied gas pressure should be increased, typically up to 10 or 15 psi depending on powder characteristics, but care should be exercised to keep the applied gas pressure to a minimum necessary to accomplish the function of loosening the lowermost layer.  
         [0110]    It should be noted that the pressures are applied pressures on the upstream side of the porous distributor plate  18 . The actual gas pressure seen by the powder is less than the applied pressure because of a pressure drop across the porous distributor plate  18 . The gas pressure is also adjusted to control the flow rate of powder out of the mini-hopper  10 .  
         [0111]    The use of low gas pressure ensures that only the bottom layer of the powder bed stored in the mini-hopper  10  is fluidized while the majority of the powder bed remains in a solid state. The use of low gas pressure will prevent powder segregation in the mini-hopper  10  when using a powder mixture or alloy with a wide powder size distribution, prevent any dusting of fine particles, and the powder can maintain a lock around the inlet leveling pipe  30 .  
         [0112]    The use of high gas pressure results in fluidization of the entire powder bed which will cause powder segregation, dusting of fine powders, and prevent a powder lock around the inlet leveling pipe  30  which will cause malfunctioning of the fillshoe. The powder flow rate into the transport  12  can also be controlled by the inclination of the porous distributor plate  18 , shown horizontal in FIG. 1A.  
         [0113]    Adding a slope to the porous distributor plate  18  will increase the powder flow rate out of the mini-hopper  10  and prevents any dead zones of powder in the back of the mini-hopper  10 . The inclusion of a slope in the porous distributor plate is most helpful for powders/particulate materials with poor flow characteristics. The inclination should be kept small (e.g. between 0 and 20 degrees of inclination, preferably between 510 degrees, most preferably about 7.5 degrees) because a large inclination will cause uneven loosening and fluidization of the layer of powder near the porous distributor plate  18 .  
         [0114]    The mini-hopper  10  is covered with a venting screen  36 , which allows the gas to escape to prevent build up of pressure within the mini-hopper  10  while entraining any particles. The mesh size of the venting screen  36  depends on the particle size distribution of the powder/particulate material being used.  
         [0115]    The height of powder in the mini-hopper  10 , reference letter “H” in FIG. 1A, influences the flow rate of powder into the transport  12 . At a constant gas pressure, the higher the level of H, the higher the powder flow rate.  
         [0116]    The mini-hopper  10  provides a break between the fillshoe and the main hopper  26 . As such, it provides higher efficiency and accuracy of filling by isolating the filling operation from the main powder supply in the main hopper  26 , from variations in head pressure in the flexible tube  28  and main hopper  26 , and from powder surge in the flexible tube  28 . The result is to maintain the same conditions for successive fill operations, which contributes to consistency of fill of die cavity.  
         [0117]    The transport device  12  receives powder from the mini-hopper  10  and is connected to the side of the mini-hopper  10  via side discharge  38 . The side discharge  38 , as opposed to a discharge from the base, helps to keep the profile of the apparatus to a minimum to meet the clearance requirements for installation and operation on a die-casting machine.  
         [0118]    The transport device  12  has a porous distributor plate  40  for partitioning the transport device  12  into a first partition  42  in which the particulate material flows and a second partition  44  separate from the first partition and in communication with the first partition via the porous distributor plate  40 . The powder flows from the mini-hopper  10  into the first partition of the transport device  12 . The powder flow stops when the transport  12  is full.  
         [0119]    The powder flow resumes as soon as powder is discharged from the delivery chute  14  into the closed die cavity  32 . An inlet gas port  46  is provided for receiving a compressed gas in the second partition. The porous distributor plate  40  ensures uniform transmission of gas pressure to all sections of the transport  12 .  
         [0120]    The powder is loosened and can become fluidized by migration of the compressed gas through the porous distributor plate and into the first partition. The mesh size of the porous distributor plate  40  again depends on the particle size distribution of the powder/particulate material, and is chosen to prevent clogging by entrapment of the small particles within the pores.  
         [0121]    The degree of fluidization is controlled by regulating the gas pressure to the inlet port  46 . The pressure and volumetric flow of the gas is critical to the proper performance of the fill system. The gas pressure used in the transport  12  is the same or similar to the pressure used for the mini-hopper  10 , and the pressure and volumetric flow are kept at a minimum.  
         [0122]    Again, the use of low gas pressure ensures that only the bottom layer of the powder in the transport device  12  reaches a fluidized state while the majority of the powder remains solid. This will prevent powder segregation in the transport device  12  when using a powder mixture or alloy with a wide powder size distribution, and prevent any dusting of fine particles.  
         [0123]    The transport device  12  is covered with a venting screen  48 , which allows the gas to escape to prevent build up of pressure within the transport  12  while entraining any particles. The mesh size of the venting screen  48  depends on the particle size distribution of the powder/particulate material being used. The venting screen extends over the entire length of the transport  12  to minimize the time required for gas to escape and minimize any disturbance of the powder flow.  
         [0124]    The transport device  12  sits preferably at an angle of about 45 degrees to the horizontal. Other configurations are possible, including from 0-15 degrees, 15-30 degrees, 30-45 degrees, and 45-60 degrees. Inclinations beyond 60 degrees are possible, but will require a large clearance between the die surface and upper punch.  
         [0125]    This angle controls the powder trajectory as it enters the delivery chute  14 . This angle can be adjusted to make sure it meets the clearance requirements of the die-casting machine on which the system will be mounted. As such, it can in some embodiments vary from zero, i.e., horizontal, to around 50 degrees. The angle of the transport device  12  to the horizontal influences the flow rate from the transport device  12  through the delivery chute  14  and into the die cavity  32 .  
         [0126]    For the same head pressure, a high angle for the transport device  12  will increase the flow rate while a low angle will reduce the flow rate. The angle of the transport device  12  is tailored to powder type. Typically, powders with poor flow characteristics or high angle of friction require a higher angle for the transport device  12 .  
         [0127]    The gas pressure at inlet port  46  is also used to control the flow rate. An increase in gas pressure will result in an increase in powder flow rates and vice versa. The applied gas pressure is adjusted depending on, inter alia, the cross-sectional area of the transport device  12 , the cross-sectional area of the die cavity opening, the volume of the die cavity  32 , and the time allowed for fill during the compacting operation. In addition, the width of the transport device  12  is tailored such that the width increases slightly from the mini-hopper  10  to the delivery chute  14 . The increase in width results in a diverging channel for powder flow. The result is much improved and consistent powder flow, especially for powders with poor flow characteristics.  
         [0128]    The delivery chute  14  functions as the powder discharge unit directly above the die cavity  32 . The delivery chute  14  has an outer ring  50 , which surrounds the opening of the die cavity  20 . The delivery chute  14  is covered with a venting screen  52 , which allows the gas to escape to prevent build up of pressure within the delivery chute  14  while entraining any particles.  
         [0129]    As noted above, the mesh size of the venting screen  52  depends on the particle size distribution of the powder/particulate material being used. The venting screen  52  should be proximate to the die cavity  32  to allow the gas to escape in the least amount of time to prevent any turbulence caused by buildup of gas pressure and delay in die filling operation. The size of the venting screen  52  is also maximized to minimize the time required for the gas to escape. The lack of proper venting will cause variations in filling and partial filling, especially for powders with poor flow characteristics.  
         [0130]    Fluidizers are preferably embedded in the delivery chute  14  to ensure powder is fluidized just before filling the die cavity  32 . The design of the fluidizers is customized to part shape to optimize fill performance for individual parts or family of parts, depending on part size and shape complexity.  
         [0131]    Turning now to FIG. 2A, several small exemplary fluidizers are illustrated. Those as in FIG. 2A are used for gear-shaped parts, and are positioned, e.g., above gear lightening holes.  
         [0132]    A ring fluidizer as illustrated in FIG. 3 may be used for powders with poor flow characteristics to improve fill consistency.  
         [0133]    One center fluidizer is illustrated in FIGS. 4 a  and  4   b , and can be used, e.g., for large ring-shaped parts. A unique feature of this center fluidizer is that it acts like a powder valve when the gas is turned on and off. FIG. 4A illustrates the “gas off” situation where the powder is not flowing, and the backup on the central fluidizer keeps the powder locked. FIG. 4B illustrates the “gas on” situation where the powder is flowing by the fluidization action of the gas.  
         [0134]    In addition, a ring fluidizer may be combined with either a center fluidizer or several small fluidizers to increase fill speed and further improve fill uniformity.  
         [0135]    Referring again to FIG. 1, an inlet port  54  is provided for receiving a compressed gas in the center fluidizer. The delivery chute  14  is attached to the transport device  12  by a joint plane  56 . The method of attachment allows the easy removal of the delivery chute  14  and its quick replacement and customization for a different die cavity  32 .  
         [0136]    Turning to FIG. 1B, it may be seen that the gas control unit  16  may be located in a separate housing and is used to control the gas moisture content and regulate powder fluidization timing in relation to the movement of the fill shoe on the die-casting machine.  
         [0137]    An in-line dryer  58  may be used to remove moisture from the gas supply. An in-line filter  60  may be used to remove solid impurities in the gas supply. The gas control  16  contains a control device  62 , which may be a computing device capable of being programmed for various run profiles and sensing parameters to control the fluidized particulate flow. The control device may also incorporate a timer, three independent pressure regulators  64 , three pressure gauges  66 , and three pneumatic solenoids  68 . The gas control unit  16  is used to regulate the flow of gas to each segment of the fillshoe independently.  
         [0138]    The timing of the gas flow to the center fluidizer is used to control the amount of powder discharged into the die cavity  32 . The timing may be triggered by a micro-controller on the die casting machine or by a proximity sensor mounted on the die casting machine. The die casting or other machine may also be connected to the control device  62  to provide seamlessly integrated operation.  
         [0139]    The use of 3 independent stages for pressure and timing allows customization and tuning of each stage of the system for multiple applications.  
         [0140]    Returning to FIG. 1, it may be seen that the apparatus also provides an exhaust hood  70  for collection of any fine powder particles that may escape through the venting screens. The exhaust hood  70  has a vent  72  which is left open or can be connected to a vacuum machine if the escape of any amount of particles is considered detrimental to the environment.  
         [0141]    The venting screens are designed as removable vents for easy maintenance and cleaning of the apparatus. A hold-down mechanism is attached to the fillshoe to hold the fillshoe tight on the die casting machine and move the fillshoe forward into fill position and pull it back from under the punch during compacting. The hold-down mechanism may be attached to the fillshoe at shoulder bolts  74 .  
         [0142]    [0142]FIG. 2A shows the design for a delivery chute for producing, e.g. a gear, by the process according to the invention with one (1) lightening hole at the center and eight (8) lightening holes around the circumference. The delivery chute shows the layout, which includes a center fluidizer  74  and eight fluidizers  76  around the circumference. An outer ring  82  around the fluidizers inside the delivery chute  14  has an inside diameter larger than the outside diameter of the die cavity  32  and surrounds the die cavity  32  when the fillshoe is in the fill position.  
         [0143]    As the fillshoe is pushed forward into fill position above the die cavity, the fluidizers will be right above core rods inside the die cavity.  
         [0144]    [0144]FIG. 2B illustrates a vertical cross section and shows how the center fluidizer  74  and the fluidizers  76  around the circumference are suspended from a manifold  84  inside the delivery chute  14 . A gas port  86  is provided to allow gas to flow into the individual fluidizers.  
         [0145]    Turning now to FIG. 2C, it can be seen that each individual fluidizer  88  has a tube  90 , which acts as a support and allows gas to flow through, The tube  90  is connected at the base to a cup  92 . The cup  92  is covered with a porous distributor plate  94 , which ensures uniform transmission of gas to the powder inside the delivery chute  14 . The tube  90  has holes  96  between the cup  92  and the porous distributor plate  94 . The holes  96  are evenly distributed around the circumference of the tube  90  to ensure uniform gas pressure inside the chamber between the cup  92  and porous distributor plate  94 . The tube  90  has threads  98  at the top. The threads  98  are used to suspend the fluidizer  88  from the manifold  84  (FIG. 2B). A lock nut  99  at the base of the threads  98  is used to secure a tight fit of the fluidizer  88  to the manifold  84 .  
         [0146]    The center fluidizer  74  (FIG. 2A) and the fluidizers  76  around the circumference have the same design as discussed for an individual fluidizer  88  (FIG. 2C). The diameter of the center fluidizer  74  can be different than the diameter of the other fluidizers  76 , depending on the part shape.  
         [0147]    A collimator  100  (FIG. 2A) is centered within the delivery chute  14  (FIG. 1A) and on the center fluidizer  74  (FIG. 2A). The optimal case for powder filling is to drop the powder vertically and uniformly above the die cavity  32 . The powder exits the transport device  12  at an angle alpha and enters the delivery chute  14  through the collimator  100 .  
         [0148]    The collimator  100  changes the direction of the powder to vertical. By adjusting the height of the collimator  100  a nearly uniform distribution of powder is achieved. Without the collimator  100  the powder exits the transport at an angle and hits the front of the delivery chute before dropping into the die cavity  32 . As a result, without the collimator  100  variations in fill are seen between the front and back of the die cavity  32 .  
         [0149]    Typical operation of the fluidized fillshoe includes several stages. The fluidized fillshoe shown in FIG. 1A is mounted on a die casting machine. The fillshoe is pushed forward until the delivery chute  14  is centered above the die cavity  32 . As the fillshoe is pushed forward, the powder is fluidized by turning the gas pressure on.  
         [0150]    The powder is dropped in the die cavity  32  and the fillshoe is then retracted. The fillshoe may dwell on top of the die cavity  32  for around one second, depending on the size of the die cavity. Other fill times are possible, but the preferred ranges are from 0.10 to 0.5 seconds, 0.5 seconds to 1.0 seconds, and 1.0 to 3.0 seconds.  
         [0151]    Powder overfills the die cavity  32  and as the fillshoe is retracted the front of the delivery chute  14  scrapes the top of the die cavity and levels the powders. Typically, the gas pressure is turned off after the dwell time and during retraction of the fillshoe. However the gas may merely be run at a reduced pressure so as to substantially lessen or completely reduce the powder flow without completely closing the valves.  
         [0152]    Once the gas pressure is off, all powder within the fillshoe returns to a state resembling a solid. During the next fill operation, the powder will have to be fluidized again before filling. The system in a preferred embodiment delivers an amount of powder for each fill operation enough to fill, or slightly overfill, the die cavity  32  and then is turned off, as opposed to a continuous fill operation. However, in some circumstances a continuous fill may be desirable, e.g. in extremely high speed operations.  
         [0153]    [0153]FIG. 3 shows a delivery chute  102  with a ring fluidizer configuration, S porous distributor plate  105  lies within the outer ring  106  on the delivery chute  102 . An inlet gas port  108  is provided for receiving a compressed gas between the porous distributor plate  105  and the outer ring  106 .  
         [0154]    A plurality of gas ports are present spaced radially around the ring in a preferred embodiment. The porous distributor plate  105  ensures uniform transmission of gas pressure to all sections of the delivery chute  102 .  
         [0155]    A powder ring around the porous distributor plate  105  inside the delivery chute  102  becomes fluidized by migration of the gas through the porous distributor plate  105  and into the delivery chute  102 . The powder is fluidized just before it drops inside the die cavity  110 . Venting screens  112  are provided to allow the gas to escape and prevent buildup of pressure inside the delivery chute  102 . The inclination of the porous distributor plate  105  to the horizontal varies from zero (horizontal) to 90 degrees (vertical) depending on the powder flow characteristics and part shape, including size and complexity. Preferred ranges are from 10-45 degrees, 45-90 degrees, and especially about 45 degrees.  
         [0156]    [0156]FIG. 4A illustrates a delivery chute  102  with both a fluidized valve and ring fluidizer. The fluidized valve is used to meter the powder flow into the die cavity  110  by turning the gas flow on and off. The fluidized valve consists of an individual fluidizer  114  combined with an extended collimator  116 . The collimator  116  extends inside the delivery chute leaving a gap D 3  between the base of the collimator tube  116  and the top of the porous distributor plate  104 . When the gas is off, the powder  120  in the collimator  116  and above the porous distributor plate  104  forms a lock preventing any powder flow out of the delivery chute.  
         [0157]    The functioning of the fluidized valve depends on proper formation of a powder lock as soon as the gas is shut off. The powder lock illustrated in FIG. 4A depends on the powder characteristics, especially the powder angle of repose, the diameter D 1  of the collimator tube  116 , the diameter D 2  of the porous distributor plate  104  and the gap D 3 . An angle beta is defined such that the tangent of beta is equal to D 3  divided by (D 2 −D 1 )/2 (see graphical representation 1 below). If the angle beta is greater than the angle of repose of the powder, than no powder lock will form. D 2  is typically controlled by the inside diameter of the part to be compacted. D 1  is fixed for a given delivery chute. D 3  can be adjusted to enable a powder lock. 
         
 
         [0158]    Typically, the angle beta is reduced to less than or equal to the angle of repose of the powder. At the same time, the gap controls the powder flow rate out of the delivery chute. If the gap D 3  is reduced significantly, the performance of the fillshoe will be adversely affected. The gap D3 should be as large as possible to increase powder flow rate when the gas is turned on while maintaining a powder lock when the gas is shut off. When the gas is turned on, the powder flows as illustrated in FIG. 4B.  
         [0159]    Typical operation of the fluidized fillshoe with a single fluidized valve has one major difference from the design with multiple fluidizers. While the gas is turned off, the fillshoe is pushed forward until the delivery chute  122  is centered above the die cavity  124 . No powder is dropped in the die cavity as the fillshoe is pushed forward. Once the delivery chute  122  is centered above the die cavity  124 , the gas is turned on and the die cavity  124  is filled. As such, all powder is dropped vertically, consistently and uniformly into the die cavity during successive filling operations.  
         [0160]    The dwell time of the fill shoe over the die cavity  124  depends on the size of the die cavity  124 . The gas is shut off, a powder lock is formed inside the collimator tube  126 , and then the fill shoe is retracted. The dwell time is controlled with the timer to minimize the amount of overfill of the die cavity  124 . As the fillshoe is retracted, the die cavity surface is scraped and the excess loose powder within the delivery chute  122  is discharged into a cavity or sloped area in a wear plate on top of the die casting machine. As such, during the subsequent fill operation no residual powder exists within the delivery chute and no powder is dropped in the die cavity  124  during fillshoe movement.  
         [0161]    Turning now to FIGS. 5A and 5B, a preferred apparatus for open cavity will be described in detail.  
         [0162]    “Open cavity” refers to a set up in which there is a gap or open space between the apparatus for powder/particulate material filling and the cavity or container receiving the powder/particulate material.  
         [0163]    Typically, powder/particulate material is delivered to a filling station above the container and dropped freely into an open container. Air in the container is allowed to escape freely. In this application, the fill system is stationary. When located on a production line, there is generally no limit on space above the open cavity.  
         [0164]    With reference to FIG. 5A particularly, a powder delivery and filling system for an open cavity includes a mini-hopper  128 , a transport  130 , a delivery chute  132  and a gas control unit (not shown, but similar to FIG. 1B). The mini-hopper  128  has a porous distributor plate  134  for partitioning the mini-hopper into a first partition  136  in which the bed of particulate material is received and a second partition  138  separate from the first partition and in communication with the first partition via the porous distributor plate  134 .  
         [0165]    An inlet powder port  140  is provided for receiving powder mixture/particulate material in the first partition. The inlet powder port  140  is connected to the main hopper with a leveling pipe  142 . The powder flows through the inlet powder port  140  into the leveling pipe  142  into the first partition  136  of the mini-hopper. When the powder level in the min-hopper  136  reaches the base of the leveling pipe  142  the powder forms a lock, powder flow stops and the powder level is maintained constant.  
         [0166]    The powder flow resumes as soon as powder is discharged from the mini-hopper  128  into the transport  130 . An inlet gas port  144  is provided for receiving a compressed gas in the second partition of the mini hopper  128 . The porous distributor plate  134  ensures uniform transmission of gas pressure to all sections of the mini-hopper  128 . As elsewhere, the porous distributor plate may be either vertical or at an angle to the vertical, depending on powder flow characteristics.  
         [0167]    As noted above, the layer of powder near the porous distributor plate  134  becomes loose by migration of the compressed gas through the porous distributor plate and into the first partition. The mesh size of the porous distributor plate  134  depends on the particle size distribution of the powder/particulate material, and is chosen to prevent clogging by entrapment of the small particles within the pores.  
         [0168]    The mesh material is preferably stainless steel to provide high strength, good wear properties, good weldability and non-corrosiveness. Other materials may be selected for varying purposes, e.g. filtering or the like, and other materials may be used such as aluminum, copper, reinforced felting, etc.  
         [0169]    The fluidization is controlled by regulating the gas pressure to the inlet port  144 . The volume of the gas flow and the gas pressure is important to the proper performance of the fill system. The gas pressure used depends on the powder characteristics and preferably should be kept at a minimum. The use of low gas pressure ensures that only the layer of the powder near the porous distributor plate  134  is fluidized while the majority of the powder remains in a solid state.  
         [0170]    This will prevent powder segregation in the mini-hopper  128  when using a powder mixture with a wide powder size distribution, prevent any dusting of fine particles, and the powder can maintain a lock around the inlet leveling pipe  142 .  
         [0171]    Turning now to FIG. 5B, it can be seen that the mini-hopper  128  is covered with a venting screen  148  which allows the gas to escape to prevent build up of pressure within the mini-hopper while entraining any particles. The mesh size of the venting screen  148  depends on the particle size distribution of the powder/particulate material being used.  
         [0172]    The mini-hopper  128  provides a break between the fillshoe and the main hopper. As such, it advantageously isolates the filling operation from the variations in head pressure, and provides a constant powder head. The result is to maintain uniform conditions for successive fill operations, which contributes to consistency of fill.  
         [0173]    The transport device  130  has a porous distributor plate  152  for partitioning the transport into a first partition  154  in which the particulate material is received and a second partition  156  separate from the first partition and in communication with the first partition via the porous distributor plate  152 . An inlet gas port  158  is provided for receiving a compressed gas in the second partition.  
         [0174]    The porous distributor plate  152  ensures uniform transmission of gas pressure to the first partition of the fluidized pipe transport device  154 . The layer of powder near the porous distributor plate  152  becomes loose by migration of the compressed gas through the porous distributor plate and into the first partition. Again, the mesh size of the porous distributor plate  152  depends on the particle size distribution of the powder/particulate material, and is chosen to prevent clogging by entrapment of the small particles within the pores.  
         [0175]    The mesh material is preferably stainless steel to provide high strength, good wear properties, good weldability and is non-corrosive, but other materials may be used.  
         [0176]    The fluidization is controlled by regulating the gas pressure to the inlet port  158 . The magnitude of the gas pressure is important to the proper performance of the fill system. The gas pressure used depends on the powder characteristics and should be kept at a minimum. The use of low gas pressure ensures that only a thin layer of the powder near the porous distributor plate  152  is loosened to eliminate or minimize dusting and segregation.  
         [0177]    The transport  130  is covered with a venting screen  160  which allows the gas to escape to prevent build up of pressure while entraining any particles. The mesh size of the venting screen  160  depends on the particle size distribution of the powder/particulate material being used. The inclination of the porous distributor plate  152  to the horizontal varies depending on powder flow characteristics. A typical inclination is around 45 degrees, but ranges from 5-25; 25-65; and 65-75 are possible depending on the powder type.  
         [0178]    The delivery chute  132  functions as the powder discharge unit directly above the open cavity  164 . The delivery chute  132  has a collimator pipe  166  and a fluidizer  169 . The collimator pipe  166  redirects the direction of flow of the powder to vertical and is directly positioned above the open cavity.  
         [0179]    The fluidizer  169  has the same design as the fluidizer illustrated in FIGS. 4A and 4B. The combination of the collimator pipe  166  and fluidizer porous distributor plate  168  enable the system to function as a fluidized valve with powder flow when the gas is turned on and no powder flow when the gas is turned off.  
         [0180]    The delivery chute  132  is covered with a venting screen  170  which allows the gas to escape to prevent build up of pressure within the delivery chute  132  while entraining any particles. The mesh size of the venting screen  170  depends on the particle size distribution of the powder/particulate material being used. The proximity of the venting screen  170  to the top of the porous distributor plate  168  is critical to allow the gas to escape in the least amount of time to prevent any turbulence caused by buildup of gas pressure and interference with powder flow within the collimator tube  166 .  
         [0181]    An inlet gas port  172  is provided for receiving a compressed gas in the fluidizer.  
         [0182]    The gas control unit  16  as illustrated in FIG. 1B is located in a separate housing and is used to control the gas moisture content and regulate powder fluidization timing in relation to time of filling of the open container. The gas control unit  16  is used to regulate the flow of gas to each segment of the fillshoe system independently. The timing of the gas flow to the center fluidizer is used to meter the amount of powder discharged into the cavity  164 .  
         [0183]    The gap D 3  between the base of the collimator tube  166  and the top of the porous distributor plate  168  is adjusted to control the flow rate. When the gas is off, the powder in the collimator  166  and the porous distributor plate  168  forms a lock preventing any powder flow out of the delivery chute  132 .  
         [0184]    The functioning of the fillshoe system depends on proper formation of a powder lock as soon as the gas is shut off. The powder lock illustrated in FIG. 5A depends on powder characteristics, especially the powder angle of repose, the diameter D 1  of the collimator tube  166 , the diameter D 2  of the porous distributor plate  168  and the gap D 3 . An angle beta is defined such that the tangent of beta is equal to D 3  divided by (D 2 −D 1 )/2. If the angle beta is large than no powder lock will form. D 2  is typically controlled by the inside diameter of the part to be compacted. D 1  is fixed for a given delivery chute. D 3  can be adjusted to enable a powder lock.  
         [0185]    Typically, the angle beta is reduced to less than or equal to the angle of repose of the powder. A preferred angle is 45 degrees, and other usuable ranges include 25-65 degrees and from 10-80 degrees, approaching the vertical or horizontal. At the same time, the gap controls the powder flow rate out of the delivery chute. If the gap is reduced significantly, the performance of the fill system will be adversely affected. The gap D 3  should be as large as possible while maintaining a powder lock.  
         [0186]    When the gas is turned on, the powder flows as illustrated in FIG. 5B. A built in micrometer  174  is used to adjust the gap D 3 . The micrometer  174  is near the gap D 3  which makes it easy to use, and is on the outside the delivery chute  132  which makes it easy to access.  
         [0187]    [0187]FIG. 6 illustrates one method for supporting the apparatus for filling open cavities. The apparatus may be affixed to post  176   
         [0188]    [0188]FIG. 7 illustrates an embodiment suitable for powder/particulate material with very poor flow characteristics. A fluidized cone  178  is introduced between the transport  180  and the delivery chute  182 . The fluidized cone  178  has a porous distributor plate  184  for partitioning the fluidized cone  178  into a first partition in which the particulate material is received and a second partition separate from the first partition and in communication with the first partition via the porous distributor plate  184 .  
         [0189]    An inlet gas port  186  is provided for receiving a compressed gas in the second partition. The layer of powder near the porous distributor plate  184  becomes loose by migration of the compressed gas through the porous distributor plate and into the first partition. The fluidization is controlled by regulating the gas pressure to the inlet gas port  186 . The magnitude of the gas flow and the gas pressure is important to the proper performance of the fill system.  
         [0190]    The gas pressure used depends on the powder characteristics and should be kept at a minimum. The use of low gas pressure ensures that only a thin layer of the powder near the porous distributor plate  184  is loosened to eliminate or minimize dusting and segregation. The cone fluidizer  178  is covered with a venting screen  188  which allows the gas to escape to prevent build up of pressure while entraining any particles.  
         [0191]    The inclination of the porous distributor plate  184  to the horizontal varies depending on powder flow characteristics. A typical inclination is around 45 degrees.  
         [0192]    Turning now to FIG. 8, an embodiment suitable for powder/particulate material with poor flow characteristics is described. With such characteristics, replenishment of the mini-hopper from the main hopper through a flexible hose may be inconsistent. An in-line fluidized connector is introduced at discrete locations along the flexible tube, especially at the location where there is a reduction in the diameter of the tube.  
         [0193]    The purpose of the fluidized connector is to assist powder flow in pipes and tubes, especially at areas with a transition in pipe diameter. With reference to FIG. 8, a porous distributor plate  190  surrounds the outer ring  192  of the fluidized connector  194 . An inlet gas port  196  is provided for receiving a compressed gas between the porous distributor plate  190  and the outer ring  192 . A powder ring around the porous distributor plate  190  inside the fluidized connector  194  becomes fluidized by migration of the gas through the porous distributor plate  190  and into the fluidized connector  194 .  
         [0194]    Venting screens  198  are provided to allow the gas to escape and prevent buildup of pressure inside the fluidized connector or exit through the inlet pipe  200  or the outlet pipe  202 . The inclination of the porous distributor plate  190  to the horizontal is 45 degrees, but is adjusted depending on the powder flow characteristics.  
         [0195]    The control of gas pressures, volumes, and flow to the various gas inlet ports of the present invention is controllable by variable valves as illustrated in FIG. 1B. The valves may be controlled by a computer running appropriate software to accomplish the result of smooth flow. The valves may also be manually adjusted by an experienced operator for smooth flow. Suitable computer equipment includes standalone or networked computers for control of stages of a continuous process. Strategically located sensors may detect excess powder flow, and optical inspection may reveal insufficiently filled dies or molds. In that event, the sensors, which can be linked to the control computer, signal that too much or too little powder is being transferred though the apparatus, and the gas flow may be increased or decreased as the situation warrants.  
         [0196]    While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.
A fluidizing method transports particulates by gravity flow but passes the particulates through a fluidizer which is partitioned by a porous distributor plate to form first and second chambers and wherein the particulate materials pass through said first chamber which is in gaseous communication with said second chamber via the porous distributor plate. Gas is delivered to the second chamber at a pressure sufficient to generate a gas bearing between the porous distributor plate and the particulate material. The gas is permitted to migrate through the particulate material, but it is then vented to the surrounding atomosphere without causing substantial turbulence in the particulate material and to reduce tendencies for dusting and separation of the particulates into sizes.