Method of and apparatus for detecting change in the breakoff point in a droplet generation system

• US 4,487,320 A
• Filed: 11/03/1980
• Issued: 12/11/1984
• Est. Priority Date: 11/03/1980
• Status: Expired due to Term

• Current Assignee: Coulter Corporation (Danaher Corporation)
• Original Assignee: Coulter Corporation (Danaher Corporation)
• Inventors: Auer, Robert E.
• Primary Examiner(s): Reeves, Robert B.
• Assistant Examiner(s): WACYRA, EDWARD MICHAEL
• Application Number:
  US06/203,121
• Time in Patent Office: 1,499 Days
• Field of Search: 209/3.1-3.3, 209/44.1, 209/44.2, 209/546, 209/548, 209/549, 209/571, 209/579, 209/906, 209/127 R, 250/222 R, 250/222 PC, 356/39, 356/72, 356/73, 356/335, 356/338, 361/226, 364/413, 346/75
• US Class Current: 209/3.1
• CPC Class Codes: G01N 15/1404 Handling flow, e.g. hydrodynamic focusing
• CPC Class Codes: G01N 2015/1406 Control of droplet point
• CPC Class Codes: Y10S 209/906 Pneumatic or liquid stream feeding item

Abstract

A particle separator for sorting particles suspended in a liquid according to certain characteristics, including a method of and apparatus for detecting a change in the droplet breakoff point of a liquid jet stream which is subjected to vibrations. The vibrations produce amplitude undulations on the surface of the jet stream. The amplitude of the undulations is monitored or interrogated at a fixed point on the jet stream prior to the breakoff point. A change in amplitude of the undulations at that fixed point produces a signal voltage the value of which is proportional to the amplitude change. This signal voltage may be used (1) to alert the operator that a change has occurred in the point at which the jet stream is breaking up into droplets, (2) to automatically control the intensity of the vibrations for restoring the amplitude of undulation at that fixed point to its original state, or (3) to automatically disable the sorting portion of the apparatus. Any one or any combination of the foregoing three happenings can be utilized.

Claims

1. In an apparatus for analyzing and sorting particles suspended in a liquid wherein a liquid jet stream is produced and vibrations applied thereto in order to produce undulations on the surface of said stream and subsequent breakup of the jet stream into droplets which are collected downstream, the method which comprises sensing the amplitude of undulation on the surface of an uninterrupted portion of said jet stream by radiation which is scattered by said stream during its analyzing and/or sorting mode at a fixed point on said stream prior to the breakpoint region of said stream and automatically controlling the intensity of the vibrations applied to said stream in response to a change in said amplitude of undulation at said fixed point in such direction as to restore said amplitude of undulation at said fixed point to its original state, to thereby prevent drift in said breakup point.

2. In an apparatus for analyzing and sorting particles, the method of claim 1, which includes automatically restoring the value of said amplitude of undulation at said fixed point for deviations below a predetermined level, and automatically disabling said system when the deviations in amplitude of undulation at said fixed point exceed said level.

3. In the apparatus of claim 2, the method of which includes the step of simultaneously creating an alarm when said system is disabled.

4. In an apparatus for analyzing and sorting minute particles on the basis of preselected characteristics or combinations of preselected characteristics wherein a fluid suspension in the form of a jet stream is produced and vibrations applied thereto to produce undulations on the surface of said stream and subsequent breakup of the jet stream into droplets, the method which comprises interrogating said stream by applying a concentrated beam of rays to an uninterrupted portion of said jet stream by radiation which is scattered by said stream during its analyzing and/or sorting mode at any fixed point on said stream prior to the breakpoint region, deriving a d.c. signal from said interrogation which is proportional to the amplitude of the undulations at said fixed point, and controlling the intensity of said vibrations by said d.c. signal in response to a deviation of said amplitude from a predetermined level.

5. The method of claim 4 which includes converting said signal to a visual indication as to the position on said stream of the droplet breakup point.

6. The method of claim 4 which includes utilizing said d.c. signal to disable said apparatus upon a deviation of said amplitude from a predetermined level.

7. Apparatus for analyzing and sorting minute particles while the particles are suspended in a liquid, comprising in combination:

first means for producing a jet stream from said liquid suspension, second means for vibrating said jet stream to produce undulations on the surface of said stream and subsequent breakup of the stream into droplets for collection downstream, third means for impinging a beam of concentrated rays upon an uninterrupted portion of said jet stream during its analyzing and/or sorting mode at a fixed location thereon prior to the breakpoint region, a photo diode means operating in the current mode so positioned as to receive and detect the rays scattered by said jet stream as a result of impingement by said beam, rectifier means having an input and output, said input of said rectifier means coupled to the output of said photo diode means, for producing a voltage which is proportional to the amplitude of the undulations on the jet stream at said fixed location and said output of said rectifier means coupled to said second means, indicating means coupled to the output of said rectifier means and responsive to the rectified output thereof for indicating a change in the amplitude of undulation at said fixed location, and particle sensing means operating at a point prior to the breakoff point.

8. Apparatus according to claim 7, wherein said indicating means includes a meter.

9. Apparatus according to claim 7, wherein said indicating means includes an audible alarm.

10. Apparatus according to claim 7, wherein said second means includes a piezo-electric vibrator, said beam is a laser beam, said rectifier means includes a full wave rectifier, and said photo diode means is located generally in the same plane as the laser beam and also in the plane of light scattered produced by the impingement of said laser beam on said jet stream.

11. Apparatus according to claim 7 including disabling means coupled to the output of said rectifier means, said disabling means including a relay driver latching device coupled to the output of a fast change detector for disabling the sorting function of said apparatus.

12. Apparatus according to claim 7, including an automatic gain control circuit having an input coupled to the output of said rectifier means and having an output coupled to said vibrating means for altering the intensity of vibrations applied to said jet stream in response to a change in the level of said amplitude of undulation of said fixed location in such direction as to restore said amplitude of undulation at said fixed location to its original state and thereby correct for a change in the breakoff point of said jet stream.

13. Apparatus for analyzing and sorting minute particles while the particles are suspended in a liquid, comprising in combination:

first means for producing a jet stream from said liquid suspension;

second means for vibrating said jet stream to produce undulations on the surface of said stream and subsequent break-up of the stream into droplets for collection downstream;

third means for impinging a beam of concentrated rays upon an uninterrupted portion of said jet stream during its analyzing and/or sorting mode at a fixed location thereon prior to the breakpoint region, means positioned to receive and detect rays scattered by said jet stream as a result of impingement by said beam, a trans-impedance operational pre-amplifier coupled to said last means, an A.C. path including an A.C. amplifier coupled to the output of said pre-amplifier, a rectifier means having an input and output, said input of said rectifier means coupled to the output of said A.C. amplifier, for rectifying the signal obtained therefrom and said output of said rectifier means coupled to said second means, and means coupled to and responsive to the output of said rectifier means for alerting the operator of a change in said breakoff point.

14. In an apparatus for analyzing and sorting particles suspended in a liquid, said apparatus including first means for producing a jet stream from said liquid suspension, second means for vibrating said jet stream to produce undulations on the surface of said stream and subsequent breakup of said stream into droplets for collection downstream, the improvement comprising:

third means for impinging a beam of radiation upon an uninterrupted portion of said jet stream during its analyzing and/or sorting mode at a fixed location thereon prior to the breakpoint region,

fourth means, coupled to said second means, for receiving and detecting the radiation from said third means which is scattered by said stream and for providing an output which is proportional to the amplitude of undulation at said fixed location,

fifth means electrically coupled to said fourth means for providing a signal indicating a change in the amplitude of undulation at said fixed location;

whereby said change in the amplitude of undulation correlates to a change in position of the breakoff point of said droplets.

15. Apparatus for analyzing and sorting minute particles while the particles are suspended in a liquid, comprising in combination:

first means for producing a jet stream from said liquid suspension, second means for vibrating said jet stream to produce undulations on the surface of said stream and subsequent breakup of the stream into droplets for collection downstream, third means for impinging a beam of concentrated rays upon said jet stream at a fixed location thereon prior to the breakoff point of said droplets, a photo diode so positioned as to receive and detect the rays scattered by said jet stream as a result of impingement by said beam, rectifier means coupled to the output of said photo diode for producing a voltage which is proportional to the amplitude of the undulations on the jet stream at said fixed location, means coupled to the output of said rectifier and responsive to the recitified output thereof for indicating a change in the amplitude of undulation at said fixed location, an automatic gain control circuit having an input coupled to the output of said rectifier means and having an output coupled to said vibrating means for altering the intensity of vibrations applied to said jet stream in response to a change in the level of said amplitude of undulation at said fixed location in such direction as to restore said amplitude of undulation at said fixed location to its original state and thereby correct for a change in the breakoff point of said jet stream, and means coupled and responsive to the output of said rectifier means for disabling the sorting function of said apparatus, said disabling means including a fast change detector and a relay driver latching device coupled to the output of said detector.

16. Apparatus according to claim 15, including a manually controllable by-pass path for short-circuiting the output of said automatic gain control circuit.

17. Apparatus for analyzing and sorting minute particles while the particles are suspended in a liquid, comprising in combination:

first means for producing a jet stream from said liquid suspension, second means for vibrating said jet stream to produce undulations on the surface of said stream and subsequent break-up of the stream into droplets for collection downstream, third means for impinging a beam of concentrated rays upon said jet stream at a fixed location thereon prior to the breakoff point of said droplets, means positioned to receive and detect rays scattered by said jet stream as a result of impingement by said beam, a trans-impedance operational pre-amplifier coupled to said last means, an A.C. path including an A.C. amplifier coupled to the output of said pre-amplifier, a rectifier coupled to the output of said A.C. amplifier for rectifying the signal obtained therefrom, means coupled to and responsive to the output of said rectifier for alerting the operator of a change in said breakoff point, a D.C. path having a D.C. amplifier also coupled to the output of said pre-amplifier, a voltage-controlled gain amplifier coupled to the outputs of both said A.C. and D.C. amplifier in such manner that the output from the D.C. amplifier controls the gain of said voltage-controlled gain amplifier, and a connection from said rectifier to said last amplifier, whereby said rectifier rectifies the A.C. signal obtained therefrom and produces a voltage which is proportional to the amplitude of the undulations on the jet stream at said fixed location.

18. In an apparatus for analyzing and sorting particles suspended in a liquid, said apparatus including first means for producing a jet stream from said liquid suspension, second means for vibrating said jet stream to produce undulations on the surface of said stream and subsequent breakup of said stream into droplets for collection downstream, the improvement comprising:

radiation means for impinging a beam of radiation upon an uninterrupted portion of said jet stream during its analyzing and/or sorting mode at a fixed location thereon prior to the breakpoint region, and

sensing means, coupled to said second means, responsive to radiation from said radiation means which is scattered by said stream, for providing an output to said second means which is proportional to the amplitude of undulation at said location.

19. The apparatus according to claim 18, further including particle sensing means, responsive to said beam of radiation which illuminates said particles in said jet stream, for sensing said particles at said fixed location.

20. In an apparatus for analyzing and sorting particles suspended in a liquid wherein a liquid jet stream is produced and vibrations applied thereto in order to produce undulations on the surface of said stream and subsequent breakup of the jet stream into droplets which are collected downstream, the method which comprises sensing the amplitude of undulation on the surface of an uninterrupted portion of said jet stream by radiation which is scattered by said stream during its analyzing and/or sorting mode at a fixed point on said stream prior to the breakpoint region, and controlling said vibrations in proportion to the amplitude of the undulation at said fixed point.