Powder feed rate sensor

Abstract

A powder feed rate sensor includes a surface or diaphragm configured to detect powder feed rate.

What is claimed is: 
     
         1 . A method of measuring powder feed rate during a material deposition process comprising:
 directing powder toward a surface;   generating acoustic vibration pulses caused by the powder contacting the surface;   detecting the acoustic vibration pulses;   converting the acoustic vibration pulses to an electrical signal; and   measuring the electrical signal to determine the powder feed rate.   
     
     
         2 . The method of  claim 1 , wherein the surface can be positioned at an oblique angle relative to the direction of the power. 
     
     
         3 . The method of  claim 1 , wherein the surface comprises a metal diaphragm having a thickness range from about 25 micron to about 1000 micron. 
     
     
         4 . The method of  claim 1 , wherein the step of detecting the acoustic vibration pulses comprises using a sensor. 
     
     
         5 . The method of  claim 4 , wherein the sensor comprises a pressure transducer, piezoelectric sensor, or an acoustic microphone. 
     
     
         6 . The method of  claim 1 , wherein the step of directing the powder comprises dropping the powder onto the surface. 
     
     
         7 . The method of  claim 1 , wherein the step of directing the powder comprises directing the powder within a substantial vacuum. 
     
     
         8 . A powder feed rate sensor with an in-situ configuration for vapor deposition comprising:
 a diaphragm, which, when powder is directed onto the diaphragm, emits acoustic vibration pulses caused by the powder contacting the surface;   a sensor configured to detect the acoustic vibration pulses;   a converter configured to convert the acoustic vibration pulses to an electrical signal, wherein the electrical signal comprises a representation of the powder feed rate.   
     
     
         9 . The powder feed rate sensor of  claim 8  wherein the diaphragm can be positioned at an oblique angle relative to the direction of the powder and the diaphragm comprises a metal diaphragm having a thickness range from about 25 micron to about 1000 micron. 
     
     
         10 . The powder feed rate sensor of  claim 8 , wherein the sensor comprises a pressure transducer, a piezoelectric sensor, or an acoustic microphone. 
     
     
         11 . The powder feed rate sensor of  claim 8 , wherein the sensor has sensitivity range from about 500 mV/psi (72.5 mV/kPa) to about 50,000 mV/psi (7,250 mV/kPa). 
     
     
         12 . A closed loop powder feed rate control system for a material deposition system comprising:
 a powder source;   a powder output conduit; and   a powder feed rate sensor and control module, wherein the module is configured to control a rate of delivery of powder from the powder source based on the powder feed rate.   
     
     
         13 . The powder feed rate control system of  claim 12 , wherein the powder source comprises a vibratory bowl. 
     
     
         14 . The powder feed rate control system of  claim 12 , wherein the sensor and control module comprises:
 a diaphragm, which, when powder is directed onto the diaphragm emits acoustic vibration pulses caused by the powder contacting the diaphragm;   a sensor configured to detect the acoustic vibration pulses;   a converter configured to convert the acoustic vibration pulses to an electrical signal, wherein the electrical signal comprises a representation of the powder feed rate; and   a feed back control module reading the sensor and adjusting the powder feed rate.   
     
     
         15 . The powder feed rate control system of  claim 12 , wherein the sensor and control module comprises:
 a parallel plate capacitor, configured to provide an electric field in a powder path, wherein the electric field is altered by the presence of powder directed along the powder path, causing a change to the capacitance;   a sensor detecting the change of the capacitance and correlating the change to the powder feed rate; and   a feed back control module reading the sensor and adjusting the powder feed rate.   
     
     
         16 . The powder feed rate control system of  claim 12 , wherein the sensor and control module comprises:
 a light source configured to direct light toward a powder path;   a high speed camera configured to perform fast frame capture on powder directed along the powder path;   a process module counting pixels with contrast against background on images resulting from the fast frame capture to correlate to powder feed rate; and   a feed back control module reading the output of the process module and adjusting the powder feed rate.   
     
     
         17 . The powder feed rate control system of  claim 12 , wherein the sensor and control module comprises:
 a powder path;   a current source;   an electrode having an angled surface relative to the powder path, wherein the electrode is electrically connected to the current source, and held at an elevated potential, and configured to lose charge when powder is directed onto the angled surface and generate a current;   an ammeter electrically connected to the current source and the electrode, configured to detect the current and correlate the current to the powder feed rate;   and   a feed back control module reading the ammeter and adjusting the powder feed rate.   
     
     
         18 . The powder feed rate control system of  claim 12 , wherein the sensor and control module comprises:
 a light source configured to direct an incident light beam toward a powder path, wherein the beam is scattered by the presence of powder directed along the powder path;   a scattered beam sensor configured to detect the scattered beam intensity;   a process module read the scattered beam intensity from the scattered beam sensor to correlate to powder feed rate; and   a feed back control module reading the output of the process module and adjusting the powder feed rate.   
     
     
         19 . The powder feed rate control system of  claim 12 , wherein the sensor and control module comprises:
 a powder exit chute, wherein powder is directed to the output conduit through a transparent section of the exit chute, forming a 1-grain thick layer on the transparent section;   a light source configured to direct light toward the transparent section, wherein the transmitted light intensity can be made proportional to the powder feed rate;   a sensor configured to detect the transmitted light intensity;   a process module read the transmitted light intensity from the sensor to correlate to powder feed rate; and   a feed back control module reading the output of the process module and adjusting the powder feed rate.