US4756252A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Device for reducing the base resistance of airborne projectiles
Assignee: Saab Bofors AB
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Filing: 1981-10-22
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Granted: 1988-07-12
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Expires: 2001-10-22
Abstract
Abstract The invention deals with a method of eliminating the base resistance of a flying object. Included in the invention is a device specially adapted to the method. According to the invention base resistance is eliminated by means of the combustion gases from a combustion chamber (2) built into the object being released from the said chamber and led towards the base surface of the object via devices (9-16, 20, 24 and 30) which eliminate the greater part of the gases' motive energy before or simultaneously with their reaching an outlet located on the base surface of the object through which they are allowed to flow out under such conditions that the base resistance of the object (1, 26) is at least partly eliminated.
Inventors
- 👤 Ulf Melhus
- 👤 Lennart Johansson
- 👤 Arne Franzen
- 👤 Boo Bolinder
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 20:19
CPC Classifications
F; F42; F42B; F42B10/00; F42B10/32; F42B10/38; F42B10/40
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
139 words
A device for reducing the base resistance of a projectile adapted to fly through the air and having a sheer base surface, said device comprising: a combustion chamber for containing a propellant charge and having a discharge nozzle such that when said propellant charge is burned the combustion gases are discharged from said combustion chamber at a high speed faster than the speed of sound; outlet means for causing said combustion gases to flow out to the atmosphere through said sheer base surface; and, means for reducing the speed of flow of said high speed combustion gases so that said outflowing gases have substantially no motive power when they reach the atmosphere, said speed reducing means comprising baffle means behind said sheer base surface for causing said combustion gases to change direction after passing through said sheer base surface.
Claim 2
Independent Claim
139 words
A device for reducing the base resistance of a projectile adapted to fly through the air and having a sheer base surface, said device comprising: a combustion chamber for containing a propellant charge and having a discharge nozzle such that when said propellant charge is burned the combustion gases are discharged from said combustion chamber at a high speed faster than the speed of sound; outlet means for causing said combustion gases to flow out to the atmosphere through said sheer base surface; and, means for reducing the speed of flow of said high speed combustion gases so that said outflowing gases have substantially no motive power when they reach the atmosphere, said speed reducing means comprising baffle means behind said sheer base surface for causing said combustion gases to change direction after passing through said sheer base surface.
Claim 3
Dependent Claim
33 words
A device according to claim 1 in which said baffle means includes a baffle member positioned directly across the flow path of combustion gases flowing through an opening in said sheer base surface.
Claim 4
Dependent Claim
28 words
A device according to claim 2 in which said outlet means includes a partition wall surrounding the sides of said baffle member and having radially arranged outflow openings.
Claim 5
Dependent Claim
24 words
A device according to claim 3 in which said baffle member has a cross-section much smaller than the sheer base surface of said projectile.
Claim 6
Dependent Claim
45 words
A device according to claim 1 in which said combustion gases are caused to change direction before passing through said sheer base surface by a bulkhead located directly across the path of the combustion gases flowing out of said combustion chamber through said discharge nozzle.
Claim 7
Dependent Claim
57 words
A device according to claim 1 in which said speed reducing means further comprises a chamber between said discharge nozzle and said outlet means of sufficient size relative to the quantity of said combustion gases to reduce the speed of flow of said high speed combustion gases to a speed substantially slower than the speed of sound.
Claim 8
Dependent Claim
31 words
A device according to claim 1 in which said baffle means causes at least a portion of said combustion gases to change direction by at least 90° before reaching the atmosphere.
References Cited (Backward Citations)
GB543737A
Cited
FR1257613A
Cited
US3273334A
Cited
GB975086A
Cited
GB1008574A
Cited
GB1440560A
Cited
US3698321A
Cited
GB1317032A
Cited
DE2155787A1
Cited
US3988990A
Cited
DE2547528A1
Cited
US4091732A
Cited
US4091731A
Cited
DE2804270A1
Cited
US4213393A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-07-12 | 1992-01-11 | 1992-07-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-07-12 | 1996-01-11 | 1996-07-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-07-12 | 2000-01-11 | 2000-07-12 | $7700.00 | Window Closed / Lapsed |