Apparatus for production of filler packets for solid freeform fabrication

Abstract

A hopper ( 30 ) holds a metal and flux powder ( 24 ). A filler tube ( 28 ) conveys the powder from the hopper. Compressed gas ( 36 ) is injected into the powder to fluidize and convey the powder through the filler tube. The hopper may be vibrated ( 34 ) to prevent clumping. A gas permeable envelope ( 29 ) surrounds the filler tube and is filled with powder as it moves off the end of the filler tube. The gas escapes from the permeable envelope. Feed mechanisms ( 54, 56, 66, 74 ) may feed gas permeable sheets ( 55, 57 ) over opposite sides of the filler tube. A seaming device ( 58 A-B, 78 A-B) may seam the sheets along their edges to form the gas permeable envelope surrounding the filler tube. Closing ( 40 ) and cutting ( 42 ) machines close and cut the envelope, forming a packet ( 22 ) containing the powder.

The invention claimed is: 
     
         1 . An apparatus for production of a filler packet for additive manufacturing, the apparatus comprising:
 a hopper for holding a metal powder;   a gas permeable envelope that is impermeable by the powder;   a filler tube from the hopper inserted into the gas permeable envelope; and   a gas source that provides a compressed gas to the hopper;   wherein the powder flows from the hopper through the filler tube with the compressed gas, and the compressed gas escapes the envelope while the powder is retained by the envelope.   
     
     
         2 . The apparatus of  claim 1 , further comprising a vibration device on the hopper that fluidizes the powder. 
     
     
         3 . The apparatus of  claim 1 , further comprising a feed mechanism that draws the envelope distally over the filler tube and away from an open end of the filler tube as the envelope fills with the powder. 
     
     
         4 . The apparatus of  claim 3 , wherein the envelope is formed from a gas permeable tube of sheet material surrounding the filler tube, and further comprising a cutting and closure machine that closes a first end of the envelope before a filling thereof, closes a second end of the envelope after the filling thereof, and cuts the second end of the envelope away from the tube of sheet material. 
     
     
         5 . The apparatus of  claim 1 , further comprising:
 first and second gas permeable sheets;   a sheet feed mechanism that draws the first and second sheets over respective first and second opposite sides of the filler tube; and   a seam forming mechanism that seams first and second side edges of the first sheet to respective first and second side edges of the second sheet to form the gas-permeable envelope surrounding the filler tube.   
     
     
         6 . The apparatus of  claim 5 , wherein the filler tube comprises a laterally elongated transverse section, and further comprising a feed-wise stitching machine and a transverse stitching machine operatively connected to the sheet feed mechanism for stitching the envelope longitudinally and transversely. 
     
     
         7 . The apparatus of  claim 6 , further comprising:
 a needle plate for a feed-wise stitching needle;   a presser foot corresponding to the needle plate for the feed-wise stitching needle; and   sheet feed dogs on the needle plate and the presser foot that draw the gas permeable envelope between the needle plate and the presser foot as it fills with the powder from the filler tube.   
     
     
         8 . The apparatus of  claim 7  further comprising the feed-wise and transverse stitching machines being controllable to quilt the envelope. 
     
     
         9 . The apparatus of  claim 5 , further comprising first and second spools holding the respective first and second gas permeable sheets, the first and second spools disposed on the respective first and second opposite sides of the filler tube for feeding the sheets over the filler tube. 
     
     
         10 . The apparatus of  claim 1 , wherein the compressed gas is injected into a lower 40% of the hopper. 
     
     
         11 . The apparatus of  claim 1 , wherein the gas permeable envelope comprises alumina or silica fibers, and the metal powder comprises a superalloy. 
     
     
         12 . An apparatus for production of a filler packet for additive manufacturing, the apparatus comprising:
 a hopper for holding a powder;   a compressed gas connection for injection of a compressed gas into the hopper;   a filler tube descending from the hopper for conveying the powder from the hopper;   a gas permeable tube formed of first and second gas permeable sheets disposed on respective first and second opposite sides of the filler tube;   a sheet feed mechanism that pulls the sheets over the filler tube distally toward an open end of the filler tube; and   a sheet seaming machine that seams the sheets together along adjacent side edges of the sheets as they are pulled over the filler tube to form the gas permeable tube surrounding the filler tube;   wherein the powder flows through the filler tube with the compressed gas, and the compressed gas escapes the gas permeable tube while the powder is retained therein; and   a machine that closes the gas permeable tube around the powder therein, and a machine that cuts the gas permeable tube, separating a packet from the gas permeable tube.   
     
     
         13 . The apparatus of  claim 12 , further comprising a vibration device on the hopper or filler tube. 
     
     
         14 . The apparatus of  claim 12 , wherein the filler tube comprises a laterally elongated transverse section, and further comprising a feed-wise stitching machine and a transverse stitching machine operatively connected to the sheet feed mechanism for stitching the filler tube longitudinally and transversely. 
     
     
         15 . The apparatus of  claim 14  further comprising the feed-wise and transverse stitching machines being controllable to quilt the packet. 
     
     
         16 . The apparatus of  claim 12 , wherein the sheet feed mechanism comprises:
 a needle plate for a feed-wise stitching needle;   a presser foot corresponding to the needle plate for the feed-wise stitching needle; and   sheet feed dogs on the needle plate and the presser foot that that draw the gas permeable tube between the needle plate and the presser foot as the gas permeable tube fills with the powder from the filler tube.   
     
     
         17 . The apparatus of  claim 12 , further comprising first and second spools holding the respective first and second gas permeable sheets, the first and second spools disposed on respective first and second opposite sides of the filler tube for feeding the sheets over the filler tube. 
     
     
         18 . The apparatus of  claim 12 , wherein the compressed gas is injected into a lower 40% of the hopper. 
     
     
         19 . Apparatus for production of a filler packet for additive manufacturing, the apparatus comprising:
 a hopper for holding a powder;   a filler tube descending from the hopper for conveying the powder from the hopper;   a gas permeable tube forming machine that fabricates a gas permeable tube around the filler tube;   a feed mechanism that slides the gas permeable tube over the filler tube in a direction away from the hopper and off of an open end of the filler tube;   wherein the powder flows through the filler tube into the gas permeable tube;   and further comprising a machine that closes the gas permeable tube at two points around a portion of the powder therein; and   a machine that cuts the gas permeable tube, separating the filler packet from a remainder of the gas permeable tube.   
     
     
         20 . The apparatus of  claim 18 , wherein the gas permeable tube forming machine comprises a tube braiding machine.