Abstract: An underwater vibrator is specifically adapted for generating a shear wave in a seabed and includes a frame; locomotion apparatus attached to the frame for moving the vibrator over the seabed; and cable means connected between a surface support vessel and the vibrator. The vibrator also includes buoyancy and apparatus for selectively controlling the buoyancy along with apparatus for selectively engaging the seabed with the vibrator. Apparatus is also carried by the vibrator for viewing the location of the vibrator under the water which includes lights and television equipment.

Abstract: An underwater vibrator apparatus for generating a shear wave into the consolidated seabed has a housing, a horizontally mounted mass attached to said housing for movement along an axis substantially parallel to the surface of the earth and hydraulic apparatus for oscillating the mass along the axis. Substantially all of the vibrator housing comprises a sidewall and a bottom. The sidewalls and bottom form a wedge-shaped surface means with an angled surface of the wedge-shaped surface transverse to the movement of the mass, such that as the mass oscillates the underwater vibrator against the consolidated bottom, the vibrator will settle into the bottom. The vibrator will, however, maintain contact with the bottom even when the consolidated bottom is yieldable under vibrated weight.

Abstract: An apparatus for incremental cylinder length control in a hydraulic vibrator of the type having a reaction mass with a cylinder bore disposed therein, first and second end sleeves disposed in sealed movable position in the ends of the cylinder, a piston rod sealed and slidably disposed through the first and second sleeves with a piston attached to the piston rods where the improvement comprises threading the ends of the cylinder bore and forming mating threads on the first and second sleeves with means for rotating the sleeves with respect to the cylinder so that the sleeves move toward or away from the piston thereby reducing the volume of hydraulic oil between the end of the piston and the end sleeves.

Abstract: A reaction mass and hydraulic cylinder assembly for a seismic transducer. A hydraulic biasing cylinder (76) is formed between a lower piston rod (32) and a reaction mass (44) and is located below a hydraulic drive cylinder (46). The lower piston rod (32) includes a first portion (36) and a detachable second portion (38-40), the detachable second portion forming an upward facing shoulder (42) which partially defines the hydraulic biasing cylinder (76). The hydraulic drive cylinder (46) is formed by a cylinder sleeve (48) and upper and lower cylinder bushings (50 and 52) having lower and upper ends (54 and 56), respectively, concentrically received within the cylinder sleeve (48) to define the upper and lower ends, respectively, of the hydraulic drive cylinder.

Abstract: A carrier mounted seismic vibrator system that is primarily adapted for generation of high force, high frequency seismic energy into an earth medium. The apparatus includes first and second vibrators (12F and R) as supported by first and second lift systems (28F and R) disposed in tandem juxtaposition generally centrally in said vehicle (10), and the lift systems (28F and R) are designed to maintain equal hold-down force on the vibrator coupling baseplates (32F and R) without exceeding the weight of the carrier vehicle. The juxtaposed vibrators are then energized in synchronized relationship to propagate increased amounts of higher frequency seismic energy into an earth medium.

Abstract: An underwater shear wave vibrator apparatus has a housing with a vibratory generating system mounted inside the housing for generating a force along an axis substantially parallel to the underwater seabed surface. A coupling apparatus which has an attachment surface and an underside surface for engaging the seabed is connected through a pivotal arm to the housing. A hydraulic apparatus is used for positioning the seabed engaging apparatus normal to the force axis of the vibratory generating apparatus by movement about the pivotal attachment so as to maintain contact of the seabed engaging apparatus with the seabed as the vibratory generating apparatus applies force against the seabed. Apparatus is also included for maintaining orientation of the underside surface of the positioning apparatus as the positioning apparatus moves the seabed engaging means.

Abstract: A lightweight rigid housing and baseplate structure for a seismic transducer. The baseplate (12) includes a central hub (26) for receiving a lower piston rod (76). Upper and lower skin plates (32 and 36) extend radially outward from the central hub (26). A plurality of equally angularly spaced reinforcing plates (40) also extend radially outward from the hub (26) and have their upper and lower edges rigidly connected to the upper and lower skin plates. A housing assembly (78) rigidly connects an upper piston rod (74) to the baseplate (12), and includes a frusto-conical section (82). The lightweight rigid housing (78) and baseplate (12) structure provides a seismic transducer having in-phase force distribution over substantially the entire area of the baseplate as it is engaged with the earth.

Abstract: Apparatus for incremental cylinder length control in hydraulic seismic vibrators having increased frequency range. The vibrator apparatus (10) of the type having a reaction mass (38) and axial cylinder bore (42) utilizes hydraulically movable end sleeves (86 and 96) in each end of the cylinder bore (42) so that the end sleeves (86 and 96) can be controllably positioned thereby to alter the cylinder volume and adjust the hydraulic drive system (18) for maximum efficiency relative to operating frequency.

Abstract: A hydraulic drive system for an underwater vibrator has a hydraulically driven mass for generating a seismic wave into the seabed. The hydraulic drive system for the vibrator is accomplished by filtering sea water, conveying the filtered sea water to the hydraulic pump where the sea water under pressure is supplied through a control valve to the hydraulic vibrator. The output from the control valve is coupled to the sea water. The hydraulic system provides hydraulic fluid which will not need to be cooled, thereby eliminating the normal cooling system along with several necessary accumulators and sump which are used in a closed hydraulic system.

Abstract: A high pressure seal is formed between a stationary piston and a reciprocating cylinder. The seal includes a sleeve which has an inner diameter dimensioned to permit the cylinder to slide freely over the piston rod, the sleeve being in rigid contact at one end to the cylinder and the other end to an end plate surrounding the piston and closing the end of the sleeve. A bleeder port communicates with the outer surface of the piston rod, through the piston rod, and terminates at a low pressure supply. Bleeder grooves are formed around the inner wall of the sleeve. A first bleeder groove is positioned in the inner wall of the sleeve at the mid-stroke position of the piston with second and third bleeder grooves positioned at each extreme position of the piston stroke in the inner wall of the sleeve. A plurality of pressure drop grooves is formed along the inner sleeve diameter such that the hydraulic fluid passing from the cylinder into the sleeve will gradually drop in pressure as it moves toward the end plate.

Abstract: The present invention relates to a seismic transducer for generating waves in an elastic medium and is particularly applicable to the generation of low frequency shear waves. The transducer is comprised of a mass member having more than one parallel hydraulic cylinder disposed therein, a piston member disposed in each cylinder, each piston member including a piston and a pair of oppositely extending rods, and a frame interconnecting the ends of the piston rods which frame has a base surface thereon for engaging a surface of the elastic medium in energy coupling relationship. A system of hydraulic fluid bleed-back ports associated with the piston members serve to aid lubrication and keep high pressures off of the rod end seals. The present construction permits total enclosure of the mass member and plural piston member assembly.

Abstract: Apparatus for supporting a vibrational shear wave transducer and coupling shear-wave energy into the earth's surface. The apparatus includes separate lateral base plate assemblies having the vibrator assembly operatively disposed therebetween, and the vibrator frame structure includes necessary hydraulic porting structure and supports manifold and servo valve control structure to provide a unitary, improved form of transducer apparatus. Each of the lateral base plate assemblies further includes a removable earth-coupling structure in the form of inverted pyramid or cleat structure having characteristic apex angles in both the lateral and longitudinal dimension so that earth coupling of energy is optimally effected.

Abstract: An air retaining skirt for use with an air cushion vehicle of a type which utilizes a peripheral series of loop and segment sections in combination to provide retention of the air cushion over uneven terrain or water. The loops are adapted to extend from the air cushion vehicle outward and downward in flexible, air inflatable composure, and each loop supports a plurality of ground-contacting segments affixed to the lower edge thereof and extending back up for retention at or near the lower edge of the air cushion vehicle.

Abstract: Apparatus for supplying a large amount of air periodically at a controlled rate to the air cushion beneath an air-cushion vehicle as particularly employed for coupling of controlled frequency seismic energy into the earth. The apparatus consists of a vehicle body which includes a compressed air supply or input to a self-contained plenum chamber space for applying air pressure through a multi-port rotary valve thereafter to be directed into an air cushion formed between the vehicle and the earth surface with periodic exhaust to the atmosphere. The rotary air modulator or valve is comprised of a cylindrical stator, a rotor, and a shutter, each of which includes a plurality of equispaced ports, and air flow from the plenum chamber to the air cushion is modulated by passage through the stator and rotor in accordance with an intermediate shutter position; pressure exhaust is similarly controlled.

Abstract: Apparatus for incremental cylinder length control in hydraulic seismic vibrators having increased frequency range. The vibrator apparatus (10) of the type having a reaction mass (38) and axial cylinder bore (42) utilizes hydraulically movable end sleeves (86 and 96) in each end of the cylinder bore (42) so that the end sleeves (86 and 96) can be controllably positioned thereby to alter the cylinder volume and adjust the hydraulic drive system (18) for maximum efficiency relative to operating frequency.