US4664685A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Linear drive motor control in a cryogenic refrigerator
Assignee: Azenta Inc
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Filing: 1985-11-19
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Granted: 1987-05-12
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Expires: 2005-11-19
Abstract
Abstract In a Stirling cryogenic refrigerator, the movement of the displacer is monitored by sensing the back EMF in the displacer drive coil throughout displacer stroke. The back EMF signal is applied through a feedback circuit to control the phase relationship of displacer movement with a reference signal related to the pressure wave.
Inventors
- 👤 Niels O. Young
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 03:49
CPC Classifications
F; F02; F02G; F02G1/00; F02G1/06; F02G1/04; F02G1/043; F02G1/0435; F25; F25B; F25B9/00; F25B9/14; F25B2309/00; F25B2309/003
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
160 words
A cryogenic refrigerator comprising a gaseous working fluid which is alternately compressed and expanded to cool a portion of the working fluid to cryogenic temperatures and a linear drive motor for driving a piston element in the refrigerator which acts on the working fluid in a thermodynamic refrigeration cycle, the linear drive motor comprising a drive coil through which current is applied to drive an armature coupled to the piston element, the refrigerator further comprising: a detector circuit coupled to the drive coil for sensing, throughout stroke of the piston element, an electrical parameter of the coil which is a function of movement of the armature and for generating from the electrical parameter of the coil a position signal indicative of position of the piston element; and motor drive circuitry for applying current to the drive coil, the motor drive circuitry being responsive to the position signal in controlling movement of the piston element throughout stroke of the piston element.
Claim 2
Dependent Claim
160 words
A cryogenic refrigerator comprising a gaseous working fluid which is alternately compressed and expanded to cool a portion of the working fluid to cryogenic temperatures and a linear drive motor for driving a piston element in the refrigerator which acts on the working fluid in a thermodynamic refrigeration cycle, the linear drive motor comprising a drive coil through which current is applied to drive an armature coupled to the piston element, the refrigerator further comprising: a detector circuit coupled to the drive coil for sensing, throughout stroke of the piston element, an electrical parameter of the coil which is a function of movement of the armature and for generating from the electrical parameter of the coil a position signal indicative of position of the piston element; and motor drive circuitry for applying current to the drive coil, the motor drive circuitry being responsive to the position signal in controlling movement of the piston element throughout stroke of the piston element.
Claim 3
Dependent Claim
20 words
A cryogenic refrigerator as claimed in claim 1 wherein the detector circuit senses the back EMF across the drive coil.
Claim 4
Dependent Claim
27 words
A cryogenic refrigerator as claimed in claim 2 wherein the piston element is coupled to a displacer for displacing the working fluid through a thermal regenerator matrix.
Claim 5
Dependent Claim
26 words
A cryogenic refrigerator as claimed in claim 3 wherein the motor drive circuitry responds to the phase relationship between the displacer position and a reference wave.
Claim 6
Dependent Claim
27 words
A cryogenic refrigerator as claimed in claim 1 wherein the piston element is coupled to a displacer for displacing the working fluid through a thermal regenerator matrix.
Claim 7
Dependent Claim
26 words
A cryogenic refrigerator as claimed in claim 5 wherein the motor drive circuitry responds to the phase relationship between the displacer position and a reference wave.
Claim 8
Dependent Claim
157 words
A cryogenic refrigerator comprising means for generating a pressure wave in a gaseous working fluid and a displacer for displacing the working fluid through a thermal regenerator matrix in predetermined timed relationship with the pressure wave, the displacer being driven by a linear drive motor comprising a linear drive coil through which current is applied to drive an armature coupled to the displacer, the refrigerator further comprising: a detector circuit coupled to the drive coil for sensing, throughout stroke of the displacer, an electrical parameter of the coil which is a function of movement of the armature and for generating from the electrical parameter of the coil a position signal indicative of position of the piston element; and motor drive circuitry for applying current to the drive coil, the motor drive circuitry being responsive to the position signal in controlling the relative phase of movement of the displacer to the pressure wave throughout stroke of the displacer.
Claim 9
Dependent Claim
157 words
A cryogenic refrigerator comprising means for generating a pressure wave in a gaseous working fluid and a displacer for displacing the working fluid through a thermal regenerator matrix in predetermined timed relationship with the pressure wave, the displacer being driven by a linear drive motor comprising a linear drive coil through which current is applied to drive an armature coupled to the displacer, the refrigerator further comprising: a detector circuit coupled to the drive coil for sensing, throughout stroke of the displacer, an electrical parameter of the coil which is a function of movement of the armature and for generating from the electrical parameter of the coil a position signal indicative of position of the piston element; and motor drive circuitry for applying current to the drive coil, the motor drive circuitry being responsive to the position signal in controlling the relative phase of movement of the displacer to the pressure wave throughout stroke of the displacer.
Claim 10
Dependent Claim
20 words
A cryogenic refrigerator as claimed in claim 7 wherein the detector circuit senses the back EMF across the drive coil.
References Cited (Backward Citations)
US1100280A
Cited
US2649572A
Cited
US2905876A
Cited
US3754154A
Cited
US3991586A
Cited
US4345442A
Cited
US4397155A
Cited
US4389849A
Cited
US4417448A
Cited
US4567726A
Cited
US4534176A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-05-11 | 1990-11-10 | 1991-05-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-05-11 | 1994-11-10 | 1995-05-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-05-11 | 1998-11-10 | 1999-05-12 | $7700.00 | Window Closed / Lapsed |