Abstract: An array of optical waveguide transducers, especially suitable for use in a multi-channel hydrophone seismic streamer, contains optical waveguides which are deformed in response to the parameter being sensed (underwater acoustic energy in the case of the seismic streamer). Two optical signals are obtained from each transducer, amplitude modulated in opposite polarity in accordance with the parameter and returned to a collection point by way of optical signal highways, such as optical fiber waveguides. The optical signals are time division multiplexed on the return highways by successively providing light pulses to each of the transducers upon activation of separate light sources associated therewith which are electrically activated by electrical signals propagated along a transmission line wherein the electrical signals are successively delayed.

Abstract: An optical transducer with an optical waveguide having two paths for the propagation of light is deformed in response to acoustical pressure variations or other parameters to be sensed to modulate the amplitude of the light propagated along the two paths in opposite polarities. The light outputs of the two paths are sensed by photodetectors and applied to an electrical differencing circuit. The mean values of the photodetector outputs are balanced as by mechanically providing a predetermined bias deformation of the fiber, or by electrically matching outputs of the detectors such that, on the average, the output of the differencing circuit is zero. Dynamic deformation of the fiber in the transducer results in unbalanced outputs of the photodetectors which unbalance is sensed by the differencing circuit. This differential detection method minimizes optical and mechanical sources of noise in the light source and waveguide and leads to increased signal-to-noise and enhanced dynamic range of the transducer.

Abstract: Methods and apparatus describedmaximize, within a predetermined frequency band, the continuous or near-continuous transmission of broadband acoustic power into a medium having a finite tensile strength such as water or earth. Such methods and apparatus also minimize, for a given broadband acoustic power level in a given frequency band, the negative dynamic pressure or stress excursion of an acoustic signal with respect to the average pressure or stress present in the absence of the signal. Such signals may be transmitted for geophysical exploration purposes. The signals place the medium alternately under compressive and tensile stresses with respect to some average stress, where the time duration of the application of the compressive stress is short compared with the time duration of the application of the tensile stress. The tensile stress does not exceed the tensile strength of the medium or its interfaces.

Abstract: The driving power and driving rate of a pile driver hammer is increased without increasing the overall weight of the hammer through the use of a hydraulic spring transformer which is disposed between the ram and the pile in the housing of the hammer and presents a Q at the frequency where the mass of the ram and the stiffness of the hydraulic spring are in resonance which is less than about one.

Abstract: A hydraulic rotary percussive drill which is adapted to operate as a drill for installing rock bolts in mines is described. The drill is configured so that the shank (which holds the drill steel and bit) forms a right angle with the impact mechanism, thereby reducing the height of the drill and providing longer lengths of drill steel feed in a confined environment. A hydraulic spring force coupler transfers the impact energy from the impact mechanism to the shank, steel and bit and shapes the energy so as to provide force pulses of such length as to couple efficiently the percussive energy to the rock being drilled while reducing the strain in the steel and bit. A rotation mechanism may be mounted in the same leg of the right angle as the shank, steel and bit to rotate the steel and bit independently from the percussive action.

Abstract: A source is described capable of generating acoustic signals under water at high cycling rates suitable for providing seismic signals of controlled amplitude and spectral shape and with precise timing for geophysical exploration. The source has a pair of radiating pistons in a housing having a cylindrical sleeve and radial webs. Axial shafts extend outwardly from the pistons and support the pistons in the webs. The peripheral edges of the pistons are in sliding contact with and are guided by the sleeve. The pistons and sleeve define a chamber between the pistons which, under quiescent conditions, contains gas under a low pressure or partial vacuum. The shaft on at least one of the pistons extends into another chamber in the hub of one of the webs.

Abstract: Methods and apparatus for generating and transmitting seismic signals for the purpose of seismic exploration are disclosed. The signals are force pulses shaped to have a spectrum constrained to the range of frequencies which are necessary for penetration to desired depths within the earth and for resolution of the geological reflection surfaces therein. These pulses are provided in a non-repetitive or aperiodic train, constructed to produce a transmitted energy spectrum whose mean energy extends smoothly at a substantially constant level over the spectrum frequency range, notwithstanding that the repetition frequency of the pulses may be swept over a frequency band much narrower than the spectrum range. The transmitted spectrum can exhibit an auto-correlation function having a major lobe which is predominant over any side lobes, corresponding to a desired level of resolution of the geological reflection surfaces.

Abstract: A seismic source is described which drives one or more jets of high velocity water into an underwater environment and then abruptly terminates the jets. The momentum of the free jet columns generate vapor cavities in the water away from the housing of the source which cavities collapse coherently to generate the seismic signal. A piston and a valve sleeve are slidably mounted in a cylinder in the housing. The piston seals off a volume of gas on its rearward side. The forward side of the piston defines one surface of a chamber. The chamber receives high pressure water from an inlet. In its rearward position, the valve sleeve seals a set of jet apertures in the side of the cylinder. In its forward position the valve sleeve opens the apertures, exposing the chamber interior to the exterior underwater environment. With the valve sleeve in its rearward position with the apertures sealed, the high pressure water entering the chamber moves the piston to its rearward position and compresses the gas.

Abstract: Apparatus is described for welding of thermoplastic parts and the like where the heat to melt the surface or surfaces to be joined is produced by friction during high frequency rubbing. The parts are adapted to be placed on a platen which enables the mating surfaces of the parts to be brought into clamping engagement in a welding head. The welding head includes a seismic mass. Stiff flexural members support a plate, against which the parts are clamped with respect to the seismic mass, and which provides for relative vibratory motion of the mating surfaces to be joined. A hydroacoustic driver is coupled to the plate and causes the plate to execute linear vibratory motion at a high frequency, where the stiffness of the flexural members is resonant with the mass of the vibrated portions of the head. Due to the stiffness of the flexural member and the high frequency of vibration, the relative displacement of the mating surfaces to be joined during vibration can be extremely minute.

Abstract: Impact tools are described which are capable of developing percussive forces for rock drilling, seismic exploration and other repetitive high force applications. Each of the tools contains a hammer and a valve which may be hydraulically actuated so as to constitute a hydroacoustic oscillator. The valve is actuated in one direction by being engaged by the hammer and in the other direction by fluid pressure means. The fluid pressure means may be controlled by varying the fluid pressure magnitude which applies forces to the valve to effect the movement thereof so as to control the frequency of oscillation of the hammer (i.e., impact blow frequency). Control may also be provided over the hammer stroke and the blow energy.

Abstract: Impact tools are described which are capable of developing percussive forces for rock drilling and other repetitive high force applications. A hydroacoustic oscillator contained in such tools includes a hammer and a valve mechanism which is actuated by the hammer for controlling the flow of pressurized fluid so as to establish pressure variations which sustain the oscillation of the hammer. A number of alternative valve mechanisms are disclosed, each including a valve element, the motion of which is controlled by controlling the flow of fluid with respect to the valve element as the hammer and valve element move relative to each other. Such flow control is afforded by chambers defined by the valve element; hydraulic fluid flow with respect to which is controlled so as to determine the deceleration of the valve element and the motion of the element in its actuation by the hammer.

Abstract: Impact tools are described which are capable of developing percussive forces for rock drilling and other repetitive high force applications. A hydroacoustic oscillator contained in such tools includes a hammer and a valve mechanism which is actuated by the hammer for controlling the flow of pressurized fluid so as to establish pressure variations which sustain the oscillation of the hammer. A number of alternative valve mechanisms are disclosed, each including a valve element, the motion of which is controlled by controlling the flow of fluid with respect to the valve element as the hammer and valve element move relative to each other. Such flow control is afforded by chambers defined by the valve element; hydraulic fluid flow with respect to which is controlled so as to determine the deceleration of the valve element and the motion of the element in its actuation by the hammer.

Abstract: A broadband low frequency source suitable for deep sea applications without pressure compensation is disclosed. The source utilizes hydraulically powered flexural disc radiators which are sized to small fractions of the generated wavelength. Inertance is applied hydraulically to the radiators to effectively mass load the radiators, thus lowering the resonant frequency of the radiators to fall within the transmission band to minimize driving power requirements and provide for operation over a wide bandwidth.

Abstract: Impact tools are described which are capable of developing percussive forces for rock drilling and other repetitive high force applications. A hydroacoustic oscillator contained in such tools includes a hammer and a valve mechanism which is actuated by the hammer for controlling the flow of pressurized fluid so as to establish pressure variations which sustain the oscillation of the hammer. A number of alternative valve mechanisms are disclosed, each including a valve element, the motion of which is controlled by controlling the flow of fluid with respect to the valve element as the hammer and valve element move relative to each other. Such flow control is afforded by chambers defined by the valve element; hydraulic fluid flow with respect to which is controlled so as to determine the deceleration of the valve element and the motion of the element in its actuation by the hammer.

Abstract: A transmitter of acoustic energy which propagates that energy in a directional manner is described. An acoustic signal generator is connected at one end of an acoustic transmission line which exhibits a certain characteristic impedance. The line has a number of ports spaced along its length. Surrounding each port is a coupler section which is antiresonant at the driven frequency and which presents a high acoustic driving point impedance to its associated port. In one embodiment, the interior diameter of the line is changed following each port as to make the acoustic pressure along the line and at each port constant, and the acoustic energy radiated in each coupler equal. Accordingly, acoustic energy is partitioned evenly at each port so as to define an array of equal strength radiators having directional acoustic signal propagating characteristics.

Abstract: Impact tools are described which are capable of developing percussive forces for rock drilling and other repetitive high force applications. A hydroacoustic oscillator contained in such tools includes a hammer and a valve mechanism which is actuated by the hammer for controlling the flow of pressurized fluid so as to establish pressure variations which sustain the oscillation of the hammer. A number of alternative valve mechanisms are disclosed, each including a valve element, the motion of which is controlled by controlling the flow of fluid with respect to the valve element as the hammer and valve element move relative to each other. Such flow control is afforded by chambers defined by the valve element; hydraulic fluid flow with respect to which is controlled so as to determine the deceleration of the valve element and the motion of the element in its actuation by the hammer.