Patent US4475335A successfully refreshed from Google Patents.
US4475335A
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US
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Free piston heat engines
Assignee: BTG International Ltd
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Filing: 1983-02-03
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Granted: 1984-10-09
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Expires: 2003-02-03
Abstract
Abstract A Stirling cycle heat engine, specially suitable for use in environments subject to acceleration or large temperature variations, including a free and reciprocating displacer piston fitted with a non-contact device which acts with increasing force to oppose further movement whenever the piston overshoots desired limits of its movement. The device may include a magnet which is carried by the piston shaft and which experiences repulsion from like poles of magnets carried by the shaft housing.
Inventors
- 👤 Gordon Davey
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 11:34
CPC Classifications
F; F02; F02G; F02G1/00; F02G1/04; F02G1/043; F02G1/0435; F02B; F02B71/00; F02B71/04; F02G1/045; F02G2258/00; F02G2258/80
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
50 words
A heat engine comprising: a free piston, adapted to execute reciprocatory movement of predetermined maximum stroke, and a non-contact movement-resisting device associated with said piston, said non-contact device being located so as to oppose further said reciprocatory movement with increasing force whenever said piston approaches either end of said stroke.
Claim 2
Dependent Claim
50 words
A heat engine comprising: a free piston, adapted to execute reciprocatory movement of predetermined maximum stroke, and a non-contact movement-resisting device associated with said piston, said non-contact device being located so as to oppose further said reciprocatory movement with increasing force whenever said piston approaches either end of said stroke.
Claim 3
Dependent Claim
27 words
A heat engine according to claim 1 in which said non-contact device is of magnetic type and gives rise to forces of repulsion between like magnetic poles.
Claim 4
Dependent Claim
104 words
A heat engine according to claim 1 including a piston shaft attached to said piston and a stationary housing surrounding said shaft, and in which said non-contact device includes a first magnet attached to said shaft and two second magnets fixed to said housing, so arranged that a first pole of said first magnet approaches a like pole of one of said second magnets when said piston approaches a first end of said stroke, and so that a second pole of said first magnet approaches a like pole of the other said second magnet when said piston approaches the second end of said stroke.
Claim 5
Dependent Claim
27 words
A Stirling thermodynamic cycle heat engine according to claim 1 including a displacer piston and a compressor piston, in which said free piston is said displacer piston.
Claim 6
Dependent Claim
27 words
A Stirling thermodynamic cycle heat engine according to claim 1 including a displacer piston and a compressor piston, in which said free piston is said compressor piston.
Claim 7
Dependent Claim
25 words
A Stirling thermodynamic cycle heat engine according to claim 1 including a surrounding container attached to means for creating acceleration and large variations of temperature.
References Cited (Backward Citations)
US3828558A
Cited
US4183214A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-10-09 | 1988-04-09 | 1988-10-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-10-09 | 1992-04-09 | 1992-10-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-10-09 | 1996-04-09 | 1996-10-09 | $7700.00 | Window Closed / Lapsed |