High speed particle sorter using a field emission electrode

• US 4,279,345 A
• Filed: 08/03/1979
• Issued: 07/21/1981
• Est. Priority Date: 08/03/1979
• Status: Expired due to Term

• Current Assignee: John C. Allred
• Original Assignee: John C. Allred
• Inventors: Allred, John C.
• Primary Examiner(s): Rolla, Joseph J.
• Application Number:
  US06/063,461
• Time in Patent Office: 718 Days
• Field of Search: 209/509, 209/3.1, 209/3.2, 209/3.3, 209/576, 209/577, 209/579, 209/588, 209/606, 209/3, 209/44.1, 209/127, 209/552, 250/222 CP, 356/39, 324/71 CP, 346/75, 235/92 CP
• US Class Current: 209/3.2
• CPC Class Codes: B07C 5/36 Sorting apparatus characterised by the means used for distribution sorting according to destination B07C3/003, B07C3/02
• CPC Class Codes: G01N 15/1459 the analysis being performed on a sample stream
• CPC Class Codes: G01N 15/149 specially adapted for sorting particles, e.g. by their size or optical properties
• CPC Class Codes: G01N 2015/1438 Using two lasers in succession
• CPC Class Codes: G01N 2015/149 Sorting the particles

Abstract

The invention sorts small particles by subjecting them to a charging and motivating field produced by a single positively charged electrode. The magnitude of the charge placed on the particle passing the electrode is a function of the observed particle parameters. Once the particle has been deflected in accordance with its observed parameter, the particle may be collected for further study.

Claims

1. An apparatus for analyzing and sorting small particles on the basis of preselected parameters or combinations of pre-selected parameters comprising:

generating means for segregating one of said particles in at least one liquid droplet;

sensing means downstream of said generating means for sensing the presence or absence of said preselected parameter of said particle;

flow means for passing said particles from said generating means to close proximity of an electrode, said electrode being located downstream of said sensing means;

discrimination means responsive to said sensing means and functionally connected to said electrode for selectively establishing a positive high potential electric field on said electrode when said particle is closely adjacent said electrode if said sensed particle displays said pre-selected parameter; and

collection means located downstream of said electrode for receiving said particles.

2. An apparatus as in claim 1 including an environmental envelope filled with a gas whose speed of sound is higher than air surrounding said droplet from said generating means to said collection means.

3. An apparatus as in claim 2 where said flow is at a velocity less than the speed of sound in said gas.

4. An apparatus as in claim 3 wherein said gas is at subatmospheric pressure.

5. An apparatus as in claim 1 wherein said generating means is an ultrasonic droplet generator, said sensing means is a laser whose output intersects said particle and is then sensed by a photodetector, said flow means is a stream of droplets emitted by said generator under pressure, said discrimination means is an electrical signal discriminator responsive to said sensor capable of placing a high potential electric charge on said electrode if said sensor detects that said particle displays said pre-selected parameter;

and said collection means is a plurality of grounded collection containers located so as to intercept the terminus of said particle flow both when said electrode is charged and when it is not.

6. An apparatus as in claim 5 where said flow is at the rate of over 100 meters per second, close proximity is less than 0.1 inches, and electric field is strong enough to deflect said flow.

7. An apparatus as in claim 6 wherein the degree of positive electrical potential placed on said electrode is a function of the quantative presence of said sensed pre-selected parameter of said particle.

8. An apparatus as in claim 6 including at least one additional electrode capable of being charged to a high positive potential relative to said droplets in response to the presence of a second sensed parameter of said particle.

9. An apparatus as in claim 8 wherein said second electrode is located and operated in parallel with said first electrode.

10. An apparatus as in claim 8 wherein said second parameter is sensed prior to said particle'"'"'s passage near said first electrode and a sorted output stream then passes near said second electrode.

11. A method of sorting small particles according to pre-selected parameter comprising:

sensing said particles to measure said parameter of each particle;

sequentially moving each said particle to near at least one electrode;

placing a high positive electric potential on said electrode relative to said particle when each said sensed particle is near it if said particle displays said pre-selected parameter; and

collecting said particles downstream from said field emission cathode.

12. A method as in claim 11 wherein near is within 0.1 inch;

said high potential is at least strong enough to deflect said stream; and

said sequential movement is accomplished by creating a high velocity stream of particles.

13. A method as in claim 12 wherein high velocity is any velocity less than the speed of sound in the medium through which said particle stream is passing.