Patent US3877239A successfully refreshed from Google Patents.
US3877239A
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Free piston cryogenic refrigerator with phase angle control
Assignee: Raytheon Co
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Filing: 1974-03-18
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Granted: 1975-04-15
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Expires: 1994-03-18
Abstract
Abstract Cryogenic refrigerator free piston displacer reciprocates as a function of cyclic operating pressure, seal drag and bounce cylinder pressure and volume. Bounce cylinder volume is established for a particular pressure pulse frequency to optimize phase angle.
Inventors
- 👤 Bruno S Leo
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 12:56
CPC Classifications
F; F25; F25B; F25B9/00; F25B9/14; F02; F02G; F02G1/00; F02G1/04; F02G1/043; F02G1/0435; F02G1/044; F02G1/0445; F02G2250/00; F02G2250/18; F25B2309/00; F25B2309/14; F25B2309/1411
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
149 words
A cryogenic refrigerator comprising: a pulse tube, means for cyclically generating a refrigerant gas pressure pulse in said pulse tube; a free piston expander comprising a cylinder having a cold end and a warm end, a free piston mounted in said expander cylinder to separate said cylinder into a cold volume and a warm volume, the area of said piston facing said warm volume being of smaller area than the cold end of said free piston facing said cold volume, said pulse tube being connected to said warm volume, the improvement comprising: a spring urging said piston toward said cold end to reduce said cold volume, said spring having a spring constant such that the reciprocation of said free piston in said expander cylinder has an optimum substantially 90* phase angle relationship with respect to refrigerant gas pressure pulses delivered to said warm volume by said pressure pulse tube.
Claim 2
Dependent Claim
149 words
A cryogenic refrigerator comprising: a pulse tube, means for cyclically generating a refrigerant gas pressure pulse in said pulse tube; a free piston expander comprising a cylinder having a cold end and a warm end, a free piston mounted in said expander cylinder to separate said cylinder into a cold volume and a warm volume, the area of said piston facing said warm volume being of smaller area than the cold end of said free piston facing said cold volume, said pulse tube being connected to said warm volume, the improvement comprising: a spring urging said piston toward said cold end to reduce said cold volume, said spring having a spring constant such that the reciprocation of said free piston in said expander cylinder has an optimum substantially 90* phase angle relationship with respect to refrigerant gas pressure pulses delivered to said warm volume by said pressure pulse tube.
Claim 3
Dependent Claim
22 words
The cryogenic refrigerator of claim 1 wherein said spring urging said free piston to reduce said cold volume is a pneumatic spring.
Claim 4
Dependent Claim
83 words
The cryogenic refrigerator of claim 2 wherein said free piston has a bounce piston formed on the warm end thereof, said bounce piston engaging in a bounce cylinder, said bounce piston having a smaller area than the area of said free piston at its cold end, said bounce cylinder being connected to a pneumatic bounce chamber, the spring constant of said bounce chamber causing said free piston to operate at an optimum substantially 90* phase angle with respect to incoming pressure pulse cycles.
Claim 5
Dependent Claim
102 words
The cryogenic refrigerator of claim 3 wherein said bounce chamber has a spring constant to produce the physical relationship: tan theta 2d omega omega o 1/1 - ( omega omega o 1)2 where: theta phase angle between the free piston and the input pressure pulse to the warm volume d f/(2 Square Root km); f free piston friction factor omega compressor piston frequency omega o natural frequency of the free piston (k/m)1/2 k k1 + k2 k1 spring constant of piston return spring-chamber 44 k2 spring constant of gas line 20 and of free piston cylinder 24 m mass of free piston.
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) | 1978-04-14 | 1978-10-14 | 1979-04-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-04-14 | 1982-10-14 | 1983-04-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-04-14 | 1986-10-14 | 1987-04-15 | $7700.00 | Window Closed / Lapsed |