Ex. PGS 1065
`
`EX. PGS 1065
`
`
`
`
`
`

`
`United States Patent [19]
`Cole, Jr.
`
`111111111111111111111111111111111111111111111111111111111111111111111111111
`US005404339A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,404,339
`Apr. 4, 1995
`
`[54] RETRIEVER FOR A SEISMIC STREAMER
`CABLE
`Jimmy R. Cole, Jr., Houston, Tex.
`Inventor:
`[75]
`[73] Assignee: Concord Technologies Inc., Houston,
`Tex.
`[21] Appl. No.: 201,940
`[22] Filed:
`Feb. 25, 1994
`[51]
`Int. Cl.6 ........................... G01V 1/38; HOlB 7/12
`[52] U.S. CI •......................................... 367/16; 367/18
`[58] Field of Search .................................... 367/16-19,
`367/108, 133; 181/110; 144/245
`References Cited
`U.S. PATENT DOCUMENTS
`3,041,021 6/1962 Jaffe .................................... 114/245
`3,123,842 3/1964 Oeland et al ........................ 367/108
`3,706,294 12/1972 Radford .............................. 114/245
`3,795,759 3/1974 Rhyne ................................. 114/245
`3,931,608 1/1976 Cole ........................................ 340/7
`4,222,340 9/1980 Cole ...................................... 367/16
`4,541,079 9/1985 Thigpen ................................ 357/19
`4,823,325 4/1989 Cole, Jr ................................. 367/20
`
`[56]
`
`4,928,262 5/1990 Neeley et al .......................... 367/16
`5,105,548 4/1992 Fowler .................................. 33/356
`5,224,074 6/1993 Sullivan ................................ 367/16
`
`OTHER PUBLICATIONS
`Digicourse Model 5011 Compass Bird, Advertisement,
`The Leading Edge, Sep. 1993.
`Primary Examiner-Nelson Moskowitz
`Attorney, Agent, or Firm-William A. Knox
`[57]
`ABSTRACT
`A marine seismic streamer cable retriever is activated
`promptly when the cable and its attached retriever
`exceed a pre-selected safe depth. In an alternative sce(cid:173)
`nario, an electronics module in the cable retriever moni(cid:173)
`tors the presence of through-cable communications
`traffic between a mother ship and the various sensors in
`the cable. If an interruption in communications traffic is
`detected, a clock starts a count-down and sends a warn(cid:173)
`ing to the operator aboard ship. At the end of a count(cid:173)
`down period, absent prior operator intervention, the
`cable retriever is activated.
`
`9 Claims, 5 Drawing Sheets
`
`0
`
`30
`
`0
`
`Ex. PGS 1065
`
`

`
`U.S. Patent
`
`Apr. 4, 1995
`
`Sheet 1 of 5
`
`5,404,339
`
`C)
`..--i
`
`~
`
`ru
`.....
`
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`
`w
`~
`:::=)
`LJ
`1----i
`LL
`
`Ex. PGS 1065
`
`

`
`U.S. Patent
`
`Apr. 4, 1995
`
`Sheet 2 of 5
`
`5,404,339
`
`Ex. PGS 1065
`
`

`
`U.S. Patent
`
`Apr. 4, 1995
`
`Sheet 3 of 5
`
`5,404,339
`
`33
`
`FIGURE 3
`
`33
`
`FIGURE 3A
`
`j=/45
`~--------------~··~~
`
`47
`
`46
`
`40
`
`BATTERY
`
`S\.JITCH
`
`!sQUIB
`
`FIGURE 3B
`
`Ex. PGS 1065
`
`

`
`/38
`
`OUT
`IN
`VOLTAGE
`REGULATOR
`
`51
`
`\
`
`I
`
`BATTERY )--L-J
`COIL <>
`
`SQUIB
`(
`COMMON--,
`
`50 i o-~( 1 ~PLIFER
`
`(
`I
`
`54
`25 KHZ BAND
`PASS FILTER
`+/- 500 HZ
`
`~
`PHASE
`LOCKED
`LOOP
`
`45)
`
`-=- GND
`
`..
`
`~
`
`.6Q
`25 KHZ
`MODULATOR
`+1- 500 HZ
`
`~
`MICROCONTROLLER
`
`BATTERY TEST
`
`SERIAL INPUT
`
`TRANSMIT /RECIEVEI
`
`FIRE SQUIB
`
`SERIAL DATA OUT
`
`-=- GND
`
`FIGURE 4
`
`~ • '(J.).
`•
`
`""C = "'"'" ~ = "'"'"
`
`>
`'= :;
`~ ,.
`.....
`IC
`IC
`til
`
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`
`(1) -~ = tot,
`
`til
`
`...
`Cll
`~
`Q
`~ ...
`
`(H
`(H
`\C
`
`Ex. PGS 1065
`
`

`
`U.S. Patent
`
`Apr. 4, 1995
`
`Sheet 5 of 5
`
`5,404,339
`
`NO
`
`PROCESS DATA
`TO PACKET
`
`PROGRAM
`START
`
`INITIALIZE
`SYSTEM
`
`TRANSMIT
`'WARNING
`
`CHECK CLOCK
`
`. TIME-OUT
`REGISTER LIMIT
`EXCEEDED FOR
`RECEIVING
`COMMUNICATION?
`
`NO
`
`TRANSMIT
`'WARNING
`
`FIGURE 5
`
`Ex. PGS 1065
`
`

`
`RETRIEVER FOR A SEISMIC STREAMER CABLE
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`This invention relates to a combination utility module
`for monitoring the three-dimensional configuration of a
`streamer cable and for retrieving damaged cable por(cid:173)
`tions in the event of a catastrophe such as that which
`occurs when the cable exceeds a preselected depth or is 10
`rent asunder by a passing ship.
`2. Description of Related Art
`In marine seismic exploration, a ship tows a long
`streamer cable at a desired depth such as 15-20 meters
`below the water surface. The streamer cable contains 15
`acoustic receivers distributed therealong at desired
`spaced-apart intervals. A sound source periodically
`generates an acoustic wavefield which propagates
`through the water and into the earth beneath to insonify
`subsurface earth layers. The wavefield is reflected from 20
`the respective earth layers back towards the water sur(cid:173)
`face where the reflected seismic waves are detected by
`the acoustic receivers. The acoustic or seiSmic receivers
`may be hydrophones, geophones, accelerometers or
`combinations thereof. The receivers convert the me- 25
`chanica} seismic waves to electrical signals which are
`sent back to the ship, through suitable transmission
`means in the cable, for archival recording and later
`processing.
`Typically, a seismic cable may be 3000 to 4000 meters 30
`or more long. It may contain as many as a thousand
`individual data receiver channels. To avoid the need for
`thousands of separate wire lines, digital modules are
`mounted in the seismic streamer cable at intervals of 100
`to 150 meters. Each module receives analog data from 35
`respective ones of a plurality of receivers, digitizes the
`analog signals and multiplexes the resulting digital sig(cid:173)
`nals back to the ship over a single wide-band transmis(cid:173)
`sion link of any desired type. Electrical power for acti(cid:173)
`vating the digital modules is transmitted from the ship .40
`over a suitable power line in the cable for distribution to
`the respective modules.
`A seismic streamer cable is usually made up of many
`sections, each 100 to 150 meters long. A section consists
`of a PVC jacket about 5 em in diameter. The seismic 45
`receivers, data-communication channels, power lines,
`command lines and the like are mounted inside the
`cable. The digital modules are usually designed to me(cid:173)
`chanically and electrically interconnect together re(cid:173)
`spective ones of the plurality of individual cable sec- 50
`tions as well as to pre-process the received seismic sig(cid:173)
`nals. Because the above-described hardware is heavy,
`the PVC jacket is filled with a lightweight fluid such as
`odorless kerosene to render the cable sections neutrally
`buoyant with respect to the average sea water density. 55
`A streamer cable is long and flexible. Its configura(cid:173)
`tion in three axes must be known. Although the location
`of the head end of the cable is known, the effects of
`wind and sea currents may cause other parts of the cable
`to wander away from a desired line of survey by a 60
`substantial distance. Thermoclines and local changes in
`seawater density may cause the cable to erratically sink
`or rise to undesired depths. Therefore, configuration(cid:173)
`monitoring and controlling means are provided in the
`cable.
`Three-dimensional cable configuration may be moni(cid:173)
`tored with the aid of an instrumented tail buoy in com(cid:173)
`bination with a number of three-axis sensing modules
`
`65
`
`1
`
`5,404,339
`
`2
`such as disclosed in U.S. Pat. No. 5,105,548 for an Ap(cid:173)
`paratus for Determining Azimuth, Pitch and Roll, is(cid:173)
`sued Apr. 21, 1992 to John T. Fowler and a Digicourse
`advertisement taken from the September 1993 issue of
`5 The Leading Edge. A tail buoy may include some form
`of geo-location equipment such as a GPS receiver. The
`sensing modules may include digital compasses for mea(cid:173)
`suring local cable orientation and pressure-actuated
`depth sensors for measuring and reporting the local
`cable depth. The modules are mounted in the cable at
`selected intervals therealong such that the sinuosity of
`the cable can be accurately tracked.
`The cable depth may be controlled by means of a
`module having pressure-actuated or servo-actuated
`diving planes. A number of control modules, also com(cid:173)
`monly referred to as Birds, are rotatably secured to the
`seismic cable at intervals therealong. The birds each
`include comparator means that may be preset to cause
`the bird to fly at a preselected depth. One such device is
`disclosed in U.S. Pat. No. 3,931,608, issued Jan. 06,
`1976, to Jimmy R, Cole. The depth controller may of
`course be combined with the cable-configuration moni(cid:173)
`tor as above described. The '608 patent also teaches a
`method for securing the modules to the cable using
`rotating attachment rings.
`Navigation information from the tail buoy, the com(cid:173)
`passes, the depth sensors and commands to the depth
`controllers is transmitted bi-directionally between the
`towing ship and the cable-mounted sensors over a dedi(cid:173)
`cated communications line. Information is typically
`encoded and
`transmitted using phase-shift-keying
`(FSK) over a 25-kHz carrier. Instrumentation signals
`from the respective modules are coupled into the com-
`munications line with the aid of an induction loop in the
`module that is associated with a mating induction coil
`mounted in the cable near the module attachment rings.
`A seismic streamer cable complete with all of the
`accessories as enumerated is very expensive, on the
`order of a million dollars or more. In the event of a
`catastrophe such as the cable being snagged on an ob-
`struction or cut by the screws of a passing ship, or dam(cid:173)
`aged by reason of an excessive depth, it is prudent and
`economical to recover the remanent(s) of the cable for
`repair. Since the cable is normally neutrally buoyant, it
`does not necessarily surface after being cut. In fact
`when it has been cut, the jacket of the cut section loses
`its ballast fluid so that the cable remanent sinks.
`There are devices available commercially for retriev(cid:173)
`ing a damaged cable section. One such device is de(cid:173)
`scribed in U.S. Pat. No. 4,541,079, issued Sep. 10, 1985
`to Ben B, Thigpen. Here, a C02 cartridge is provided in
`selected cable sections. If the cable becomes damaged,
`an operator on the towing ship causes an alarm signal to
`be transmitted through the water to a responder associ(cid:173)
`ated with the damaged section and to other nearby
`sections. Upon receipt of the alarm signal, the cartridge
`is fired to release the gas and inflate the cable jackets of
`the one or more nearby undamaged sections. The in(cid:173)
`flated section then floats to the surface. The problem
`with that system is that it requires operator input. If the
`operator is unaware of the existence of cable damage,
`the damaged cable is lost and gone forever.
`U.S. Pat. No. 4,823,325, issued Apr. 18, 1989 to
`Jimmy R. Cole Jr, teaches a cable retriever that uses an
`inflatable bag to lift the streamer to the water surface.
`An acoustical signal or a pressure switch activates the
`device and inflates the bag. An electric drill is used to
`
`Ex. PGS 1065
`
`

`
`5,404,339
`
`4
`advantages thereof, will be better understood from the
`following detailed description and
`the drawings
`wherein the invention is illustrated by way of example
`for the purpose of illustration and description only and
`are not intended as a defmition of the limits of the inven(cid:173)
`tion:
`FIG. 1 is an isometric view of the utility module of
`this invention;
`FIG. 2 is a cross-sectional side view of the retriever
`module;
`FIG. 3 is an enlarged view of the squib-activated
`gas-release valve;
`FIG. 3A is an exploded view of the squib triggering
`device;
`FIG. 3B is the electrical circuitry for controlling
`selective firing of the squib;
`FIG. 4 is a block diagram of the retriever electronics;
`and
`FIG. 5 is a flow chart of the overall system control.
`
`3
`puncture the frangible disk that seals the C02 cylinder.
`Although the triggering device is self-actuating when
`the cable exceeds a safe depth limit, in shallow water,
`the cable my never exceed the depth limit so that the
`retriever would not activate. Furthermore, the need for 5
`an electric drill complicates the system and adds
`weight. Additionally, the steel C02 bottle interferes
`with magnetic sensing devices.
`The three types of devices that were discussed above
`are customarily hung on the seismic streamer cable at 10
`various locations therealong. Because the devices are
`heavy, each must include its own ballast. A plurality of
`modules hanging outboard of the cable create a clutter
`of hardware that increases the required towing force
`and substantially increases the ambient tow noise that is 15
`superimposed upon the relatively weak seismic signals.
`There is a need for a single compact utility module
`for use with a seismic cable that includes the combined
`features of a multi-axis configuration-monitoring sys(cid:173)
`tem, a depth controller, a module-floatation means and 20
`a self-activating cable retriever. The utility module
`including the cable retriever must be free from stray
`magnetic fields that would interfere with the magne(cid:173)
`tometer-type sensing device that is incorporated with
`the configuration-monitoring system. Once initialized, 25
`the damage-control system operation must be indepen(cid:173)
`dent of any further need for operator input.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`FIG. 1 is an isometric view of the utility module of
`this invention. The utility module 10 consists of a buoy(cid:173)
`ancy member/cable retriever unit 12, a depth control
`device 14, the tail end, 15, of which contains a three-axis
`cable configuration-monitoring system. Depth control
`device 14 such as the device described in the '608 pa(cid:173)
`SUMMARY OF THE INVENTION
`tent, is secured to rotatable rings 16 and 18 by latching
`This invention provides a utility module, character- 30 cams 17 and 19 such as described in the '325 or '608
`ized by a vertical buoyancy differential, that incorpo-
`patents. Rings 16 and 18, preferably brass, naval bronze
`or plastic such as Lexan, rotate in suitable collars 22 and
`rates a seismic streamer cable configuration-monitoring
`unit and a depth-control unit, in combination with a
`24 that are clamped around seismic streamer cable 20.
`cable retriever unit. The utility module, secured to the Wings such as 26, whose attack angle is controlled by a
`streamer cable, is rotatable about the longitudinal axis of 35 well-known internal pressure comparator (not shown)
`cause utility module 10 to fly at preselected depth as set
`the streamer cable. A buoyancy member, included with
`by the operator. It is assumed that the seismic streamer
`the cable retriever, comprises a compartmented enclo-
`sure, a first compartment of which contains floatation
`cable is being towed from right to left in the drawing.
`The forward end of the utility module is tapered so that
`material. A second compartment, having frangible
`walls, contains a normally deflated inflatable member. 40 is will not become snagged.
`The cable retriever member 12 is secured to rings 16
`A non-magnetic gas source is in fluid communication
`with the deflated inflatable member. A first programma-
`and 18 by latching cams (not shown in FIG. 1) on the
`ble pressure-sensitive triggering means actuates the gas
`opposite side of the rotatable rings, preferably above the
`source to inflate the inflatable member when the utility
`depth controller 14. Member 12 is about 10 em in diam-
`module exceeds a preselected operating depth. A sec- 45 eter and over 1 meter long. As will be shown in connec-
`tion with FIG. 2, member 12 consists of a number of
`ond programmable time-delay triggering means actu-
`ates the gas source to inflate the inflatable member fol-
`compartments. A first compartment, occupying nearly
`lowing the elapse of a preselected time delay following
`one third of its length at the rear of member 12, forms a
`the occurrence of a preselected event.
`buoyancy compartment that is filled with a lightweight
`In accordance with an aspect of this invention, the 50 cellular material such as Klegecell Q100, a trademark of
`fust and second triggering means may be selectively
`Klegecell Division of Hutchinson Group of Grapevine,
`electrically coupled to a pyrotechnic squib-operated
`Tex. The volume and mass of member 12 is such that it
`gas-release device that is operatively coupled to the gas
`provides sufficient buoyancy to render the entire utility
`modul~ at least neutrally buoyant and preferably to
`source.
`In accordance with another aspect of this invention, 55 provide about 2.5 kg of net positive buoyancy to utility
`module 10. Furthermore, since cable retriever member
`the pressure-sensitive means and the time-delay trigger-
`ing means are programmable in response to an encoded
`12 it much lighter than depth controller member 14, a
`command signal.
`vertical buoyancy differential is provided so that the
`ring-mounted utility module 10, taken as a whole, ro-
`In accordance with this invention, a compartment in
`the utility module includes means for receiving and 60 tates with member 12 riding above the longitudinal axis
`of streamer cable 20.
`decoding transmitted command signals for reprogram-
`ming the pressure-sensitive and the time-delay trigger-
`Referring now to FIG. 2, only the details of cable
`retriever unit 12 will be considered. The details of depth
`ing means.
`controller 14 and cable configuration-monitor 15 are
`well known from the two patents that were cited earlier
`and thus per se, is not germane to this invention. For
`simplicity, we shall refer to member 12 simply as a
`retriever.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`The novel features which are believed to be charac(cid:173)
`teristic of the invention, both as to organization and
`methods of operation, together with the objects and
`
`65
`
`Ex. PGS 1065
`
`

`
`5,404,339
`
`6
`5
`inductive coil (not shown) mounted in cable 20 just aft
`Cable retriever 12 includes several compartments. A
`of the mounting ring 22 (FIG. 1). The coil in cable 20 is
`first, or floatation compartment 28, is filled with the
`electrically connected to shipboard electronics via
`Klegecell material described earlier.
`twisted wire pair as is well known to the art.
`Compartment 30 forms a second compartment that is
`The cable retriever system electronics as a whole
`used to store a normally deflated inflatable bag 32. One 5
`consists of (1) A shipboard-mounted control system for
`preferred type of inflatable bag is supplied by Rocket
`Research of Redmond, Wash. who make air bags for
`sending control signals to the retrievers and for receiv-
`ing retriever status information for operator monitor-
`use in automobile safety devices, an adaptation of which
`ing. (2) a microprocessor communications and com-
`may be used for underwater devices such as disclosed in
`this invention. Compartment 30 has a frangible wall 31 10 mand unit mounted in each of the respective retrievers
`that becomes dislodged under the force generated by
`and (3) A hand-held communication unit that may be
`bag 32 when and if it is inflated.
`used for pre-programming the retriever units during
`deployment thereof. Each one of the components is
`Compartment 34 contains the gas source 36 which
`may be a NaN3 generator such as made by Rocket Re-
`individually powered by suitable batteries. Since all of
`search or it may be a non-magnetic aluminum bottle 15 those units are of similar design, only the retriever unit
`next will be described in detail.
`charged with C02 as furnished by Parker Hannifm
`Corp. of Eastlake, Ohio. Gas source 36, if it is a C02
`FIG. 4 is a block diagram of the retriever electronic
`module 38. Bi-directional communication between the
`bottle, is operatively coupled to inflatable member 32
`through a squib-actuated valve 37. Squib 40 is electri-
`shipboard control unit and the retriever electronics 38 is
`cally detonated in response to a triggering pulse from 20 handled over line 50 which is coupled to the inductive
`pickup coil48 (FIG. 2). Battery power is supplied over
`either a programmable pressure switch 39 or a time-
`line 51 from battery pack 49. Firing commands are
`delay clock in a microprocessor 38 (to be discussed later
`in connection with FIG. 4). The squib is of a type such
`output to squib 40 over line 45. Function switch 52
`as P/N071045-1 made by Cartridge Actuated Devices
`determines whether the unit transmits or receives.
`Inc. of Fairfield N.J. When triggered, C02 gas escaping 25 Function switch 52 is shown as separate units for clarity
`but are actually OR'ed together in a single unit.
`from gas source 36 flows into normally deflated mem-
`ber 32 through suitable tubing 33. As member 32 be-
`The inductive coil 48 is coupled with a parallel reso-
`nance circuit to increase the circuit Q and to function as
`comes inflated, it dislodges frangible wall 31 and
`an inherent band pass filter. In the receive mode, switch
`emerges from compartment 34 to expand to a volume of
`at least 0.06 m3 when immersed in the water at the 30 52 is followed by a coupling amplifier 53 and an active
`band pass filter 54. The signal is detected by a low
`pre-programmed pressure depth.
`The valve assembly 37 is shown in enlarged detail in
`power phase locked loop 56. The output of the phase
`FIG. 3.1t consists of a squib-actuated gas-release device
`locked loop is the actual detected frequency deviation
`40 coupled to a valve collar 43 that is screwed into the
`corresponding to the transmitted data. The discrete data
`neck of the gas bottle 36. Tubing 33 provides a fluid 35 signal is passed to microprocessor 58 which receives
`and digests incoming commands and in response
`passageway from collar 43 to member 32 when the
`valve assembly is activated. As earlier stated, the valve
`thereto, controls performance of required activities.
`fires if the cable and retriever exceed a safe depth or Microprocessor 58 also is responsible for time keeping
`and goes into a low power sleep state when there are no
`upon the occurrence of a selected event such a severing
`of the cable but followed by a pre-selected time-out 40 communications expected. It monitors the presence of
`period. A twisted wire pair 45 couples the electronics
`communications activities through the cable 20. To
`package with squib 40, programmable pressure switch
`send discrete data back to the shipboard control unit,
`46 and squib battery 47.
`the input side of switch 52 is opened and the output side
`FIG. 3A illustrates the parts of the squib-actuated
`is closed. Data pass from the microprocessor 58 through
`valve assembly 37 which includes the explosive squib, 45 25-kHz modulator 60. The modulated data are amplified
`40, itself which, when fired drives a lance 41 into a
`by power amplifier 62 and pass out through inductive
`coupler 48. Oscillator 64 provides the carrier for encod-
`diaphragm (not shown) mounted inside collar 43 in a
`conventional manner.
`ing the outgoing data.
`FIG. 3B shows the wiring diagram for actuating
`The shipboard control unit and the hand-held pro-
`valve assembly 37. If the retriever exceeds a preselected 50 gramming units are of substantially the same design as
`the retriever electronics module 38 except that those
`depth, depth switch 46, which may be of any well-
`known type, closes and fires the squib 40 independently
`units include a keypad coupled to the microprocessor
`of input signals from the retriever electronics 38 that
`for introducing program commands and an LCD for
`may be received over twisted pair 45. If excessive depth
`polling and displaying the status of the retriever status.
`In operation, there are two scenarios in view of
`is not a problem, then squib 40 may be fired under pro- 55
`gram control by retriever electronics 38 next to be de-
`which the cable retriever 12 will be actuated: (i) When
`scribed.
`the cable or a portion thereof exceeds a pre-selected safe
`Compartment 34 also includes an electronics package
`water depth, the retriever will immediately activate
`itself without delay. (ii) During normal operations,
`38 for receiving and acknowledging program command
`signals transmitted by an operator from the towing ship 60 there is always chatter on the communications line due
`to the various sensors reporting their current status.
`using FSK coding at a carrier frequency of 25 kHz,
`1200 baud, ±500 Hz frequency deviation. Electronics
`Therefore, a sudden lack of communications activity
`would suggest that the cable has been cut or damaged.
`package also monitors the communication activity be-
`However, a dearth of activity might merely mean that
`tween sensors in the cable and a shipboard control sys-
`tem. Battery pack 49 consisting of two D-type cells 65 the system has temporarily been shut down for mainte-
`nance. Therefore, a time delay function is programmed
`provides power to the electronics package 38. Battery
`pack 49 has a service life of about one year. Induction
`into the retriever electronics so that the retriever is not
`coil48 provides electromagnetic coupling with a similar
`activated prematurely. A delay of up to 24 to 48 hours
`
`Ex. PGS 1065
`
`

`
`8
`the retriever would then perform its ordained function
`upon the completion of the pre-programmed count(cid:173)
`down period. By way of example but not by way of
`limitation, the time-out warning period might be four
`hours. In the circumstance of an untoward event such as
`an excessive depth submergence in combination with a
`severed cable, immediate operation of the pressure
`switch to inflate the bag takes precedence over the
`delayed operation of the time-out operational sequence.
`The electronics section 38 may be programmed and
`interrogated using any desired encoding sequence. For
`example but not by way oflimitation, a coded command
`signal in hexadecimal format might take the form 7E 7E
`aa bb cc dd where 7E 7E is the command header, aa is
`the specific-action ident such as "set pressure switch",
`bb is a unit address, cc is a datum value such as the
`preselected pressure setting to be introduced to the
`programmable pressure switch and dd is the checksum.
`Individual units may be addressed or a global command
`may issue. Table I lists the retriever command protocol.
`To avoid communication interference between re(cid:173)
`trievers, the time clocks are synchronized as previously
`explained. Each retriever is assigned a unique address
`which determines the time schedule that a particular
`retriever is enabled for broadcasting. A broadcast inter(cid:173)
`val starts every 20 minutes with the first interval start(cid:173)
`ing at the next 20-minute boundary from the retriever
`reset. The 20-minute interval is divided into 255 4-
`second time slots. The 255 time slots correspond to the
`255 available retriever addresses. That number of ad(cid:173)
`dresses is needed in order to accommodate multiple(cid:173)
`cable configurations. Each retriever address is assigned
`a unique time slot. The retriever has up to 4 seconds to
`broadcast its message within the assigned time
`TABLE I
`Retriever Command Protocol
`Response
`7E 7E 10 aa bb cc
`
`5,404,339
`
`7
`may be selected if desired. Thus, a first triggering means
`inflates an inflatable member 32 when the retriever
`exceeds a preselected depth. A second triggering means
`causes the inflatable member 32 to become inflated
`following a pre-selected time delay after the occurrence 5
`of a preselected event such as cessation of communica(cid:173)
`tions.
`As the cable is being payed out from the mother ship,
`a plurality of retrievers are installed in sequence to the
`cable at desired intervals. When the installation is com- 10
`plete, the operator issues a command to set the desired
`time-out period before a retriever will fire. The control
`unit will interrogate each retriever in succession on the
`streamer cable, or on each cable if multiple streamer
`cables are deployed. Upon completion of the interroga- 15
`tion, the shipboard electronics compiles a report of the
`status of each retriever.
`With reference to the flow chart of FIG. 5, Follow(cid:173)
`ing the status report, the system is initialized by sending
`a sync command to all of the retrievers to synchronize 20
`all of the respective internal clocks. At the same time,
`each retriever is assigned a sequence number for time(cid:173)
`division multiplexing of communications so that no two
`retrievers will attempt to talk at the same time.
`In the event that one or more retrievers decides to 25
`fue because of cessation of communications as indicated
`at the "Communications Received?" decision point, a
`message will be sent continuously back to the ship
`warning of a contemplated action to be taken by a re(cid:173)
`triever. The operator can then inhibit the retriever from 30
`taking action and restart the count-down sequence as
`shown at the "Reset Time-Out Register". If, on the
`other hand, the streamer cable had actually been cut,
`the operator would never have received the warning;
`
`Command
`7E 7E00aa bb
`
`Description
`Reset retriever. Where
`"aa" is the retriever
`address. Wheil "aa" = FF,
`all retrievers are
`addressed. "bb" is the
`checksum.
`7E 7E OS aa bb cc dd Set Time-out. Where "aa"
`and "bb" is the time in
`minutes, "cc". is the unit
`address, and "dd" is the
`checksum.
`
`7E 7E 06 aa bb
`
`Return battery power.
`Where "aa" is the unit
`address, and "bb" is the
`checksum.
`
`7E 7E 07 aa bb
`
`Arm retriever. Where "aa"
`is the unit address, and
`"bb" is the checksum.
`
`7E 7E 08 aa bb
`
`7E 7E 09 aa bb cc
`
`Synchronize internal
`clock. Where "aa" is the
`unit address, and "bb" is
`the chei:ksum.
`
`Command broadcast by
`retriever to indicate an
`about to fire state. Where
`"aa" is the unit address,
`"bb" is the time remaining
`in 5 minute intervals, and
`
`Description
`Command Acknowledged.
`Self test performed with
`results in "aa". Unit
`address is in "bb". Check
`sum in "cc".
`
`7E 7E 16 aa cc dd
`
`7E 7E 17 aa bb cc
`
`7E 7E 15 aa bb cc dd ee Command acknowledged.
`ff
`Where "aa" and "bb" are
`the last programmed time(cid:173)
`out "cc" and "dd" is the
`new time-out "ee" is the
`unit address, and "ff" is
`the unit check sum.
`Command Acknowledged.
`Where "aa" is the battery
`voltage in 5 m V
`increments, "cc" is the unit
`address, and "dd" is the
`checksum.
`Command Acknowledged.
`Where "aa" was the last
`state (armed = 01,
`disamed = 00), "bb" is the
`present state, and "cc" is
`the command checksum.
`Command Acknowledged.
`Where "aa" is the last
`command received. "bb"
`is the status error code,
`"cc" is the unit address,
`and "dd" is the checksum.
`
`7E 7E 18 aa bb cc dd
`
`N/A
`
`Ex. PGS 1065
`
`

`
`9
`
`5,404,339
`
`10
`
`Command
`
`Description
`
`TABLE !-continued
`Retriever Command Protocol
`Response
`
`7E 7EOAaa bb
`
`"cc" is the checksum.
`Last Command received
`inquiry. Where "aa" is the
`unit address, and "bb" is
`the checksum.
`
`7E 7E lA aa bb cc dd
`
`Description
`
`Command Acknowledged.
`Where "aa" is the last
`command received. "bb"
`is the status error code,
`"cc" is the unit address,
`and "dd" is the checksum.
`
`slot before yielding to the next time slot. Under normal
`circumstances, a retriever will require less than 0.5 15
`second to broadcast its message. The remaining time
`allows for responses from the shipboard control unit
`and also allows for long term drift between retriever
`interval timers.
`This invention has been described with a certain de- 20
`gree of specificity by way of example only and not by
`way of limitation. This invention is limited only by the
`appended claims.
`What is claimed is:
`1. In combination with a multi-axis streamer-cable 25
`configuration-monitoring and control module mounted
`on a seismic streamer cable from a supporting ring that
`is rotatable about the longitudinal axis of said seismic
`streamer cable, a cable retriever system, comprising:
`an enclosure, said enclosure being fastened to said 30
`supporting ring oppositely from said configuration(cid:173)
`monitoring and control module;
`a floatation compartment in said enclosure;
`at least a second compartment in said enclosure for
`containing a normally-deflated inflatable member, 35
`said second compartment including a frangible
`wall;
`non-magnetic gas supply means in fluid communica(cid:173)
`tion with said normally-deflated inflatable member;
`first triggering means for causing said gas supply 40
`means to inflate said normally deflated inflatable
`member when said cable retriever exceeds a prese(cid:173)
`lected water depth; and
`second alternative triggering means for causing said
`gas supply means to inflate said inflatable member 45
`after the elapse of a preselected time delay follow(cid:173)
`ing the occurrence of a preselected event.
`2. The cable retriever system as defined by claim 1,
`wherein:
`said gas supply means is a solid-chemical gas genera- 50
`tor.
`3. The cable retriever