US3815022A
Expired / Lapsed
US
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Method and apparatus for measuring small aspherical particles
Assignee: General Electric Co
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Filing: 1972-10-04
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Granted: 1974-06-04
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Expires: 1992-10-04
Abstract
Abstract Method and apparatus for measuring size and asphericity of small aspherical particles is disclosed. Particles to be measured are urged through a long cylindrical pore whose diameter is greater than the largest major dimension of the particles expected and whose length is greater than several times its diameter. The suspending fluid, containing the small particles, in flowing through a long pore, exhibits a generally paraboloidal velocity profile. The variation in fluid velocity as a function of offaxis radial distance within the pore applies a shear moment to particles within the pore causing them to rotate. The resistance across the pore is measured in a conventional manner. In the case of spherical particles, rotation responsive to the fluid shear has no effect upon the resistive pulse output and measurements are performed as in the prior art. In the case of aspherical particles, on the other hand, the rotation caused by the fluid shear causes the observed resistance pulse across the pore to exhibit a plurality of relative maxima and minima. The major axis to minor axis ratio and the volume of the aspherical particles is determined from these relative maxima and minima.
Inventors
- 👤 D Golibersuch
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 12:40
CPC Classifications
G; G01; G01N; G01N15/00; G01N15/10; G01N15/1031; G01N15/12; G01N15/13
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
144 words
In apparatus for analyzing small particles, said apparatus having: fluid containment means; a partition for separating said fluid containment means into first and second chambers; a pore in said partition extending therethrough to allow movement of fluid and particles between said first and second chambers; means for causing an electrical current to flow through said pore; and means for detecting the resistance to the flow of said electrical current; the improvement which comprises: means for causing laminar fluid flow from said first chamber to said second chamber through said pore to transport said particles through said pore and to impart a rotational motion to said particles when said particles are within said pore resulting in a variation of said resistance during the passage of aspherical particles; and means for analyzing said variations of said resistance to determine the shape and volume of said particles.
Claim 2
Dependent Claim
144 words
In apparatus for analyzing small particles, said apparatus having: fluid containment means; a partition for separating said fluid containment means into first and second chambers; a pore in said partition extending therethrough to allow movement of fluid and particles between said first and second chambers; means for causing an electrical current to flow through said pore; and means for detecting the resistance to the flow of said electrical current; the improvement which comprises: means for causing laminar fluid flow from said first chamber to said second chamber through said pore to transport said particles through said pore and to impart a rotational motion to said particles when said particles are within said pore resulting in a variation of said resistance during the passage of aspherical particles; and means for analyzing said variations of said resistance to determine the shape and volume of said particles.
Claim 3
Dependent Claim
33 words
The improvement of claim 1 wherein said variations are periodic in time and said means for analyzing includes means for determining the period of said variations to determine the shape of said particles.
Claim 4
Dependent Claim
28 words
The improvement of claim 1 wherein said means for analyzing includes means for determining relative maxima and minima of said resistance to determine the volume of said particles.
Claim 5
Dependent Claim
33 words
The improvement as claimed in claim 1 wherein said pore is a long pore whose length is equal to at least five times the major dimension of the entry aperture of the pore.
Claim 6
Dependent Claim
29 words
The Improvement as claimed in claim 4 wherein said pore is a generally right circular cylindrical pore whose length is equal to between five and ten times its diameter.
Claim 7
Dependent Claim
32 words
The improvement as claimed in claim 4 wherein said source of electrical potential is a constant current source connected between first and second electrodes depending respectively into said first and second chambers.
Claim 8
Dependent Claim
26 words
The improvement as claimed in claim 6 wherein said means for detecting the resistance is a voltage responsive circuit connected between one said electrode and ground.
Claim 9
Dependent Claim
33 words
The improvement as claimed in claim 6 wherein said means for detecting the resistance includes a differential amplifier circuit having first and second input means connected respectively to said first and second electrodes.
Claim 10
Dependent Claim
23 words
The improvement as claimed in claim 1 including additionally means for preventing particles from entering and traversing said pore along the axis thereof.
Claim 11
Dependent Claim
34 words
The improvement of claim 9 wherein said means for preventing is an obstruction positioned generally coaxially with said pore and having a portion thereof in the plane of the entry aperture of the pore.
Claim 12
Dependent Claim
32 words
The improvement of claim 9 wherein said means for preventing includes a nozzle through which said particles are injected into said pore at preselected radial distance from the axis of said pore.
Claim 13
Dependent Claim
100 words
The improvement as claimed in claim 1 wherein said variations of said resistance in time are given by the relationship: 1/T2 (Vo/ pi R)2 ( gamma /1 + gamma 2)2 (1 - L/ Tau Vo) where L is the length of said pore gamma is the axis ratio of said particles, T is the period of said variations, R is the radius of said pore, r is the radial distance of said particle from the axis of said pore, Vo is the axial fluid velocity in said pore, and Tau is the transit time of said particle through said pore.
Claim 14
Dependent Claim
87 words
The improvement of claim 1 wherein said variations of said resistance in time are given by the relationship: Tau /T L gamma (r/R)/ pi R(1 + gamma 2) (1 + (r/R)2) where: L is the length of said pore, gamma is the axis ratio of said particles, T is the period of said variations, R is the radius of said pore, r is the radial distance of said particle from the axis of said pore, and Tau is the transit time of said particle through said pore.
Claim 15
Dependent Claim
56 words
The improvement of claim 12 wherein said means for analyzing includes a two-axis indicating device having first and second input means for receiving signals to be indicated on the axes thereof; said first input means being connected to said means for detecting the resistance and said second input means being connected to a time base generator.
Claim 16
Dependent Claim
135 words
The improvement of claim 12 wherein said means for detecting the resistance provides a voltage signal proportional to the resistance and further including: means connected to said means for detecting the resistance for differentiating said voltage signal; and said means for analyzing the variations includes voltage zero responsive means and first and second voltage level threshold responsive means for receiving and responding to an output of said means for differentiating; said first and second threshold responsive means being connected to and respectively initiating and terminating the operation of an elapsed time counter to determine the value of the quantity Tau ; said voltage zero responsive means providing inverted and non-inverted outputs being connected to and respectively initiating and terminating the operation of a second elapsed time counter to determine the value of the quantity T.
Claim 17
Independent Claim
157 words
A method for analyzing small non-spherical particles comprising the steps of: suspending said particles in an electrolyte solution in a first chamber, said First chamber being separated from a second chamber containing electrolyte solution by a partition having a pore therein; applying a positive hydrostatic pressure differential between the electrolyte in said first chamber and the electrolyte in said second chamber, the magnitude of said differential being preselected to cause a laminar flow of electrolyte through said pore and to cause particles to rotate in traversing said pore; applying an electrical potential across the electrolyte in said pore to cause an electrical current to flow therethrough; the resistance of said electrolyte in said pore responsive to the presence of a particle in said pore providing a current pulse whose internal structure is a function of the shape and volume of said particle; measuring and analyzing said internal structure to determine the shape and volume of said particles.
Claim 18
Independent Claim
157 words
A method for analyzing small non-spherical particles comprising the steps of: suspending said particles in an electrolyte solution in a first chamber, said First chamber being separated from a second chamber containing electrolyte solution by a partition having a pore therein; applying a positive hydrostatic pressure differential between the electrolyte in said first chamber and the electrolyte in said second chamber, the magnitude of said differential being preselected to cause a laminar flow of electrolyte through said pore and to cause particles to rotate in traversing said pore; applying an electrical potential across the electrolyte in said pore to cause an electrical current to flow therethrough; the resistance of said electrolyte in said pore responsive to the presence of a particle in said pore providing a current pulse whose internal structure is a function of the shape and volume of said particle; measuring and analyzing said internal structure to determine the shape and volume of said particles.
Claim 19
Dependent Claim
21 words
The method of claim 16 further including the step of: preventing said particles from traversing said pore along the axis thereof.
Claim 20
Dependent Claim
68 words
The method of claim 16 wherein said resistance varies when a non-spherical particle traverses said pore and does not vary when a spherical particle traverses said pore and said measuring and analyzing step includes the steps of: determining the presence or absence of variations of said resistance to determine the shape of said particles; and measuring the magnitude of said resistance to determine the volume of said particles.
Claim 21
Dependent Claim
42 words
The method of claim 18 wherein said variations occurring in the case of non-spherical particles are periodic variations and said measuring and analyzing step further includes the step of: measuring the period of said variations to determine the shape of said particles.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-06-03 | 1977-12-03 | 1978-06-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-06-03 | 1981-12-03 | 1982-06-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-06-03 | 1985-12-03 | 1986-06-04 | $7700.00 | Window Closed / Lapsed |