Abstract: An improved acoustic source array system is provided by the invention to generate acoustic signals underwater. The system has an array of acoustic signal sources, such as air guns, towable while underwater behind a surface vessel. The array includes a plurality of these sources, and spreader bar assemblies including these sources. The sources are attached by these assemblies at predetermined separation distances in the array. The spreader bar assemblies provide manifolds for storing and regulating energy, such as compressed air, to operate the sources. The array is connected to the vessel by an umbilical. The sources are controlled by a shipboard controller for firing the sources to provide acoustic signals underwater at selected times. The array may be towed from the ship with the flat side of the array assuming an angle of approximately 45.degree. or less with respect to a vertical axis. The flat side of the array includes a horizontal axis that is normal to the direction of tow.

Abstract: A signal processing system of reduced complexity over conventional banks of matched filters for each Doppler velocity of interest is responsive to a transmission which is in the form of a train of repeated Doppler invariant signals which are preferably phase continuous. The system utilizes a head end zero Doppler correlator and tapped delay line summer with summing nodes in cascade for each Doppler velocity of interest. The summer provides coherent sums indicative of the Doppler velocity of the target.

Abstract: An electromagnetically actuated friction welder produces orbital motion at interfaces between parts (usually of thermoplastic material) to bond the parts by fusion generated by friction. This welder can also be operated alternatively to produce reciprocating vibratory forces thereby providing flexibility as to the selection of an orbital or reciprocating mode, depending upon the joint to be welded. The velocity of motion is controllable preferably around the resonant frequency of the driven structure by adjusting the frequency of the AC power which operates the electromagnetic drive motor of the welder. A plate which carries one of the parts to be welded and which is driven is flexurally mounted for movement in an orbital plane or planes containing the interfaces without substantial tilting by an array of stiff members, such as rods, located around the drive motor, attached to the plate at one end and to a tubular structure at the opposite ends thereof.

Abstract: An electromagnetically actuated friction welder produces orbital motion at interfaces between parts (usually of thermoplastic material) to bond the parts by fusion generated by friction. This welder can also be operated alternatively to produce reciprocating vibratory forces thereby providing flexibility as to the selection of an orbital or reciprocating mode, depending upon the joint to be welded. The velocity of motion is controllable preferably around the resonant frequency of the driven structure by adjusting the frequency of the AC power which operates the electromagnetic drive motor of the welder. A plate which carries one of the parts to be welded and which is driven is flexurally mounted for movement in an orbital plane or planes containing the interfaces without substantial tilting by an array of stiff members, such as rods, located around the drive motor, attached to the plate at one end and to a tubular structure at the opposite ends thereof.

Abstract: Target velocity and range are measured with high resolution in an echo ranging system (sonar or radar) using composite Doppler invariant signals consisting of at least two segments, such as "rooftop" or "vee" HFM signals, such composite signals having ambiguity functions that intersect along the zero-velocity time axis with ridge lines slanted in different directions. A single correlator is used for each segment wherein returns from the target are correlated with replicas of each segment of the composite signal to separately transform the Doppler frequency shifts of the target return into outputs whose time relationship provides a frame of reference for high resolution measurement of the velocity of the target. The time relationship measurement is implemented by a set of tapped delay lines and coherent summers which output a coherent correlation-like detection peak in a bin which corresponds to the target's velocity.

Abstract: False target (reverberation, clutter, etc.) detection is suppressed in an echo ranging system (sonar or radar) in which target velocity and range are measured using a composite Doppler invariant-like signal having at least two segments, such as are present in a "rooftop" or "vee" HFM signal, such composite signal having an ambiguity function with two or more ridge lines of different slopes that intersect along the zero-velocity time axis. A bank of matched filters provides a distribution of outputs which has an ambiguity function-like character with intersecting pairs of ridge lines, the intersecting points of said pairs characterizing the range and velocity of the echo returns. This distribution is adjusted so that the intersecting ridge lines of each pair have equal and opposite slopes with respect to the time axis. In particular, fixed reverberators, which would have ridge lines intersecting on the zero-velocity time axis, would be symmetrical about this axis.

Abstract: An electromagnetically actuated friction welder produces orbital motion at interfaces between parts (usually of thermoplastic material) to bond the parts by fusion generated by friction. This welder can also be operated alternatively to produce reciprocating vibratory forces thereby providing flexibility as to the selection of an orbital or reciprocating mode, depending upon the joint to be welded. The velocity of motion is controllable preferably around the resonant frequency of the driven structure by adjusting the frequency of the AC power which operates the electromagnetic drive motor of the welder. A plate which carries one of the parts to be welded and which is driven is flexurally mounted for movement in an orbital plane or planes containing the interfaces without substantial tilting by an array of stiff members, such as rods, located around the drive motor, attached to the plate at one end and to a tubular structure at the opposite ends thereof.

Abstract: In seismic profiling systems utilizing sweeps of signals which change in repetition frequency during the transmission interval, interference results from a spurious correlation against an interfering sweep, usually produced by the first break reflection of a simultaneously transmitted sweep which is in the opposite sense for 3-D surveying or from another source. The first break interfering sweep repeats while correlating with time slipped replicas in surveying for deeper and deeper reflecting interfaces and appears as correlation sidelobe interference which has a significant contribution to the correlator output only when the interfering sweep and the replica are in a condition where their frequencies are identical or nearly so. This condition is known as stationary phase.

Abstract: A transmission from a hydroacoustic source, especially for underwater geophysical exploration, is generated in accordance with two binary codes (provided by two pulse trains or sequences having two levels and which provide a spectrum of harmonically related components). One of these codes has one more or one less harmonic component than the other. The transmission is provided with a frequency spectrum which extends between an upper and lower frequency limit by sweeping the pulse trains over an octave (2:1) frequency range, far shorter than the range of the spectrum, and utilizing one of the codes and then the other of the codes during the sweep. The spectrum of the transmission extends between two arbitrary frequencies which need not be harmonically related, notwithstanding that the sweep is limited to an octave in frequency range.

Abstract: A water gun seismic source for use in underwater environments has a sleeve valve (100) for opening a jet aperture (37, 101) to enable jets of pressurized water to be emitted for the generation of a seismic signal. The water is pressurized by a drive piston (3) which is reciprocated to a cocked position for pressurizing the water for the jets. A compressed air operated cocking mechanism (4, 7, 8, 76 or 110-199 or 200-260) is coupled to the piston for cocking it. The cocking mechanism may utilize cocking piston (7) slideable on a shaft (4) connected to the drive piston (3) which cocking piston is returned to a position where any load due to such cocking piston is decoupled from the shaft. The sleeve valve (100) may be biased to close the jet aperture ports (101) by compressed air and opened with high timing resolution when the pressurized water held back by the sleeve valve is applied to actuate it (via 40, 41, 50 & 43).

Abstract: A transmission which requires only a single source to transmit is generated in accordance with a code which is binary (a pulse train having two levels which produces a specific harmonic line spectrum). The pulses are generated by pulse time modulation of the position and duration of pulses in a sweep which extends to the upper end of the spectrum.

Abstract: In order to stress relieve exposed portions of plastic welds, and thereby reduce susceptibility of such welds to solvent-induced crazing and cracking, the welded parts are formed with flanges extending outwardly therefrom. These flanges are at least partially joined during welding, their adjoining surfaces providing at least a portion of the welded joint. After welding, the flanges are compressed in a direction transverse to their adjoining welded surfaces, the compression being of sufficient magnitude to exceed the yield strength of the flanges, thereby relieving stresses in the exposed portion of the welds. The flanges may be sheared, as by a blade which provides both transverse compressive forces and compressive forces in the direction of the adjoining welded surfaces. The flanges may be sheared through, so as to enable the sheared off end to be removed, or the shearing may penetrate only through the weld zone, providing a notch, but leaving the flanges in place.

Abstract: A hydroacoustic transducer for generating and applying acoustic energy to a load coupling structure has a hydroacoustic amplifier with a driver stage and a power stage. The power stage includes a valve, which obtains high power conversion efficiency by operating to switch the flow of pressurized hydraulic liquid on and off thereby providing a switching amplifier which presents a pressure source of acoustic energy. This source is connected to a load coupling structure by way of an acoustic transformer and an inertive element in series with the source. The inertive element is provided by a liquid-filled bore and is terminated at its input end by the larger area of a stepped piston which provides the acoustic transformer. The smaller area of the stepped piston is in hydraulic communication with the power stage of the hydroacoustic amplifier.

Abstract: In order to stress relieve exposed portions of plastic welds, and thereby reduce susceptability of such welds to solvent-induced crazing and cracking, the welded parts are formed with flanges extending outwardly therefrom. These flanges are at least partially joined during welding, their adjoining surfaces providing at least a portion of the welded joint. After welding, the flanges are compressed in a direction transverse to their adjoining welded surfaces, the compression being of sufficient magnitude to exceed the yield strength of the flanges, thereby relieving stresses in the exposed portion of the welds. The flanges may be sheared, as by a blade which provides both transverse compressive forces and compressive forces in the direction of the adjoining welded surfaces. The flanges may be sheared through, so as to enable the sheared off end to be removed, or the shearing may penetrate only through the weld zone, providing a notch, but leaving the flanges in place.

Abstract: A seismic source drives one or more jets of high velocity water into an underwater environment and then terminates the jets by means of a valve member, the motion of which is controlled to obtain precisely timed high energy seismic pulses to provide reflected signals from which high resolution seismograms may be obtained when the signals are processed.

Abstract: A seismic array containing a large number of seismic sensors, which may be optical hydrophones, has successive sections, each of which contains a subarray of sensor channels, interconnected by a fiber optic signal transmission line via telemetry modules. Synchronizing signals for initiating successive scans of the sensors in the array and timing the multiplexing of the channels are transmitted along the signal transmission line from the tail end of the line through telemetry modules to the head end. Equipment for receiving, demultiplexing and processing the seismic data is provided at the head end. The array may be towed as a seismic streamer and the head end equipment located topside on the towing vessel. The telemetry modules provide hybrid optical/electrical operation such that array sections including the optical hydrophones and fiber optic links are coupled to each other exclusively by electrical connectors.

Abstract: Joints between thermoplastic parts are friction welded (e.g., as by vibration welding) or otherwise thermally welded in such a manner that a non-uniform temperature distribution results during welding which effectively blocks flash flow from the edge of the joint, and upon cooling, produces a joint that is at least partially stress relieved and is resistant to solvent-induced crazing and cracking. Joints may employ nonparallel adjoining surfaces and/or flexural lips, which bend slightly under pressure applied during welding so as to produce a non-uniform pressure distribution and nonparallel welding surface over at least a portion of the resulting weld near the outside edge. In addition, one or more axial grooves may be used to isolate the nonparallel or lipped area of the weld from the remainder of the weld area so as to increase the lip compliance and reduce the effective pressure of molten material acting on the lip during welding.

Abstract: To relieve stresses in a plastic weld which may weaken the weld and increase its susceptibility to solvent-induced crazing or cracking, forces are applied to the weld zone (the interface between welded parts) after it has cooled to solid condition, but preferably when it is at a higher temperature than the regions of the parts adjacent thereto, which forces are higher than the yield strength of the material at the weld zone and lower than the yield strength of the material in the regions of the parts adjacent to the weld zone. The forces thereby cause yielding or plastic deformation which effectively relieves certain thermally induced stresses in the weld. Tensile stresses in the weld are thereby relieved, to reduce susceptibility of the weld to solvent-induced crazing or cracking.

Abstract: A seismic source operable in deep bore holes, and especially suitable for acoustic well logging and geophysical exploration, produces a controlled-spectrum seismic impulse. The source has a hammer which is hydraulically cocked through a hydraulic transformer into a hydraulic spring. Upon command, the hammer can be released, converting stored energy in the spring to kinetic energy of hammer motion. The hammer impacts on a liquid impulse shaping spring which couples impulse energy of controlled spectral width to the formation surrounding the hole by means of a balanced piston assembly which can be prebiased against the side walls of the hole.

Abstract: Time Division Multiplex (TDM) telemetry of submultiplex sequences of signals which may be obtained from successive sections of sensors in a sensor array are transmitted synchronously by locking generators in each section, which determine the time slots in which samples of the sensor signals from each sensor in the array may be transmitted, to successive synchronizing pulses which are generated in the section of the array furthest from the head end of the array where the telemetered signals are received. The synchronizing signals are transmitted once per scan of all of the sensors in the array and phase or time the operation of clock generators and counters which establish the timing so that neither the time slots nor the sensor data signals which are transmitted therein to the collection point at the head end of the array interfere with one another. The sensor array may be a seismic array such as a seismic streamer or spread used in geophysical exploration.