US4210897A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Heave compensation system
Assignee: Huntec 70 Ltd
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Filing: 1978-03-03
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Granted: 1980-07-01
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Expires: 1998-03-03
Abstract
Abstract A heave compensation system for an underwater towed seismic system of the kind in which a body containing a sound source and hydrophones is towed behind a ship, and a recording is made of echoes from the bottom and sub-bottom layers. An accelerometer in the towed body produces a signal indicative of the vertical acceleration of the body. The acceleration signal is double integrated within a frequency range having a low frequency roll-off to produce a position signal which is used to adjust the firing time of the source. If the fish heaves upwardly, the firing time is advanced; if the movement is downwards, the firing time is delayed. Preferably a pressure transducer in the fish produces a pressure signal which is also used to adjust the source firing time, for pressure variations below the lowest likely wave frequency. The crossover of the pressure and acceleration compensation systems is typically about 0.01 Hz.
Inventors
- 👤 Roger Hutchins
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 12:54
CPC Classifications
G; G01; G01V; G01V1/00; G01V1/38; G01V1/3817; G01V1/3835; G01V1/24; G01V1/26
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
338 words
An underwater seismic system for producing sound signals in water and for recording echoes from the bottom beneath the surface of such water, comprising: (1) a body adapted to travel through said water and including (a) a sound source for generating a sound signal, said source including input trigger means responsive to a trigger pulse received thereat for generating said sound level, (b) a receiver for receiving echoes from said bottom, (2) a recorder connected to said receiver for recording said echoes, said recorder including repetitive sweep means, and means for generating a first start signal upon commencement of each sweep, (3) delay means including: (a) pressure compensation means comprising a pressure transducer located in said body for producing a pressure signal indicative of the depth of said body, said pressure signal having a steady state value when the water pressure above said body is constant and said pressure signal changing in a first sense when the water pressure above said body decreases and changing in an opposite sense from said steady state value when the water pressure above said body increases, (b) means connected to said recorder for receiving said first start signal from said recorder, (c) means connected to said pressure compensation means for receiving said pressure signal and also connected to said means (b) and responsive to receipt of said first start signal for thereupon generating a second start signal at a time delayed from said first start signal by a time interval which has a predetermined value when said pressure signal has said steady state value and which decreases from said predetermined value when said pressure signal changes in said first sense and which increases from said predetermined value when said pressure signal changes in said opposite sense, (d) means connecting said means (c) to said input trigger means for said second start signal to constitute said trigger pulse, so that vertical movement of said body beneath said surface of said water will cause compensating variations in the time of operation of said source.
Claim 2
Dependent Claim
338 words
An underwater seismic system for producing sound signals in water and for recording echoes from the bottom beneath the surface of such water, comprising: (1) a body adapted to travel through said water and including (a) a sound source for generating a sound signal, said source including input trigger means responsive to a trigger pulse received thereat for generating said sound level, (b) a receiver for receiving echoes from said bottom, (2) a recorder connected to said receiver for recording said echoes, said recorder including repetitive sweep means, and means for generating a first start signal upon commencement of each sweep, (3) delay means including: (a) pressure compensation means comprising a pressure transducer located in said body for producing a pressure signal indicative of the depth of said body, said pressure signal having a steady state value when the water pressure above said body is constant and said pressure signal changing in a first sense when the water pressure above said body decreases and changing in an opposite sense from said steady state value when the water pressure above said body increases, (b) means connected to said recorder for receiving said first start signal from said recorder, (c) means connected to said pressure compensation means for receiving said pressure signal and also connected to said means (b) and responsive to receipt of said first start signal for thereupon generating a second start signal at a time delayed from said first start signal by a time interval which has a predetermined value when said pressure signal has said steady state value and which decreases from said predetermined value when said pressure signal changes in said first sense and which increases from said predetermined value when said pressure signal changes in said opposite sense, (d) means connecting said means (c) to said input trigger means for said second start signal to constitute said trigger pulse, so that vertical movement of said body beneath said surface of said water will cause compensating variations in the time of operation of said source.
Claim 3
Dependent Claim
46 words
A system according to claim 1 wherein said means (c) includes a low pass filter connected to said pressure transducer to attenuate pressure signals above a selected frequency, to reduce the effect on said time interval of pressure changes at said body above said selected frequency.
Claim 4
Dependent Claim
13 words
A system according to claim 2 wherein said selected frequency is 0.01 Hz.
References Cited (Backward Citations)
US4091356A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1983-07-01 | 1983-12-31 | 1984-07-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-07-01 | 1987-12-31 | 1988-07-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-07-01 | 1991-12-31 | 1992-07-01 | $7700.00 | Window Closed / Lapsed |