Abstract: A general biquadratic filter circuit is described which uses operational transconductance amplifiers. A bias current controls the transconductance (gm) of the amplifiers which in turn control the corner frequency (Wo) of the circuit. The circuit is configured with three potential sources which can be preselected to either be at a ground level or at a desired voltage level. By preselecting which of the potentials are grounded and which are at a desired voltage level, the circuit can become either a lowpass, highpass, bandpass or notch filter.

Abstract: A capacitive ratioing oscillator circuit utilizing a prior art pressure capsule, but through modification of the state variable oscillator circuit achieves a digital output which varies with the square root of the capacitance ratio C35 C.sub.p /C.sub.r. In this sensor the dielectric constant of the pressure media is measured in time with the pressure difference measurement. The oscillator includes a differentiator-inventor step herein each of capacitors C.sub.r and C.sub.

Abstract: A drum and piston drive system incorporates within the interior of a drum used for reeling cable in and out, a reversible electric motor which drives the drum from the inside through a gearset. Also carried within the drum is a manifold structure including a gear pump driven directly from the opposite end of the reversible motor operating in a closed hydraulic circuit to supply hydraulic pressure to reversibly move a piston in a cylinder. The manifold includes check valves limiting the pump output pressure, and a pair of accumulators which maintain a desired pressure on both sides of the pump to avoid cavitation. Relief valves in the manifold limit the pressure to the piston and check valves in each line to the cylinder block reverse flow. The system operates to control and coordinate drum rotation movement and direction with the direction and movement of the piston.

Abstract: The invention provides an accelerometer (10) which can be connected to or disconnected from a support structure (12) by means of a single fastening component (18) while holding remaining structural components (14, 16, 20) at a fixed azimuthal position relative to the top surface (38) of the support structure (12).

Abstract: In a method for use in assembling an annular shear accelerometer (10), a nested combination of an expandable force ring (14), a crystal (16), and a mass element (18) is formed, and the force ring (14) is wedge to exert radially tensile force thereon. The force ring (14) and mass element (18) thereby cooperate to exert radially compressive force on the crystal (16), thus effecting friction locks between the radially adjacent pairs of elements which make up the nested combination (14, 16, 18).

Abstract: There are electronic instrumentation assemblies in which most of the hard wired circuitry and functions are very similar for a significant number of different applications yet each assembly for a separate application is fabricated as a separate unit. Applicants system includes a single electronic circuit assembly for all such applications including a large plug-in connector, and a much smaller faceplate assembly with a mating connector unit containing software in the form of one or more PROMs plus a limited number of discrete components. An instrumentation assembly for a particular application includes the correctly programmed faceplate assembly which is plugged directly into the front panel of the electronic circuit assembly. As compared with having a separate electronic assembly for each different application, the present arrangement permits the major part of the assembly to be a single assembled unit with a single part number, configuration control, assembly and test procedure etc.

Abstract: A generally tubular-shaped or cylindrical vehicle for operation in a fluid medium is formed with a bluff or stubby afterbody and utilizes an actuator disc type propeller of approximately one-half to three-fourths of the diameter of its housing at its rear for propulsion. The propeller, in addition to driving the vehicles, is spaced from the body such that it inducts half or more of the boundary layer flow, thereby acting to draw the flow smoothly over the after part of the vehicle with a minimum of flow separation and turbulence and drag caused thereby. Steering in pitch and yaw is provided by a plurality of fins located just forward of the bluff rear surface of the vehicle. In this location the fins are more than usually effective, hence smaller than customary, because they are exposed to a fluid velocity which is near or above free stream velocity rather than at a lower velocity which is usual in vehicles having tapered afterbodies.

Abstract: A sonar array connected to a data unit includes a substantial number of hydrophone units distributed along a small diameter cable having a substantial number of connecting wires, a center strength member and a tough polyurethane jacket. The hydrophone units each include a strong metal bracket bifurcated at each end and fastened to the strength member. A generally cylindrical hydrophone member is fastened to the bracket as is a circuit board including a preamplifier and the entire unit is sealed with paraxylene resin and then molded into a smooth generally cylindrical unit which is tapered at the ends and sealed to adjacent parts of the cable jacket. To minimize the cross-sectional area and the effects of cross currents, the cable is composed of a plurality of interconnected sections, each of which is of smaller cross-section and carries fewer conductors than the section next closer to the data unit.

Abstract: A lightweight linear hydraulic actuator which is unusually inexpensive to fabricate includes a cylindrical barrel of metal tubing material, a head end gland and a rod end gland fastened to the barrel, a piston and a rod in the barrel with the rod extending through the rod end gland, ports in the sidewall of the barrel on opposite sides of the piston and fitting members having channels in registry with the ports, the fitting members including hoop type attachments around the exterior surface of the barrel and a curved surface mating with the curvature of the barrel. A circular groove is formed in the surface of the barrel around each of the ports and an O-ring seal is located in the grooves sealing against the curved surface of the fitting member. An axial extension forming part of each of the fittings includes a boss receiving a threaded fastener for fastening the fittings to the barrel.

Abstract: Improved load regulation is provided in a switched mode power supply having an integrator, with a controlled reference signal connected thereto, a comparator circuit and a square wave generator, connected to the terminals of an AND circuit, and AND circuit connected to a power driver outputting to a transformer having two secondary windings. A current sensing resistor connected to the power driver is fed back to the comparator where this current level is compared with the integrator output. A first secondary winding is connected through a diode to the load with a capacitor connected across the load and a second secondary winding is connected in a feedback line to the integrator with a series diode, a capacitor is connected across the second secondary winding with a voltage divider connected across the second secondary line in parallel with the capacitor. The above arrangement is for current mode topology and an alternate arrangement is shown for voltage mode topology.

Abstract: A hydraulic servo system to control flow rate of working fluid to a hydraulic motor as a function of command includes a spool-type pilot valve with manual or electrohydraulic structure for positioning the pilot valve and control conduits connecting the pilot valve to a flow control valve having lands and chambers between the lands for directing flow to the hydraulic motor, the flow control valve having a cylindrical cavity at one end and being exposed to full system pressure at the other end, a shuttle valve coaxially positioned with respect to the flow control valve having an axial extension extending into the cylindrical cavity, a spring in the cavity which tends to urge the flow control valve in a direction to oppose the system pressure, with control passages connecting opposite sides of the shuttle valve with the flow control valve chambers causing the shuttle valve to select the higher pressure in the flow control valve chambers and causing the spool to seek a position providing the desired flow rate.

Abstract: A cable wiper assembly for airborne sonar includes a housing suspended from a hoist used to rapidly raise and lower a sonar transducer at the end of a cable. The wiper assembly is interposed ahead of the cable-directing sheaves forming part of the hoist to strip away the sea water which adheres to the cable as it is pulled from the ocean. The cable wiper housing includes a series of internal grooves each of which contains and secures one wiper stage. Each stage includes a washer-like wiper of elastomeric material whose internal diameter is just slightly smaller than the cable diameter carried in a shallow cup-shaped holder having an internal port significantly larger than the cable diameter and secured by means of an upper washer-member overlying the wiper whose internal diameter is slightly larger than the diameter of the cable.

Abstract: A high speed rotary filter device is disclosed which utilizes a shrouded rotor, the shroud located over the central bladed portion of the rotor minimizing secondary flow within the device and thereby enhancing the separation and removal of very small particles from the airstream passing through the device.

Abstract: A cryocooler system including a reversed Brayton cycle turbo-refrigerator system having a surge control valve in the bypass line between the compression section inlet and outlet. The compression section includes at least one compressor and an aftercooler which rejects the heat of compression to a heat sink. The cooling section includes at least one regenerator and a turbo-alternator for expansive cooling of the working fluid.

Abstract: A differential variable capacitance acceleration sensor includes a sandwich structure having three stacked plates of silicon with the center plate mounted such that its center portion is enabled to move in a sealed cavity with each side thereof moving toward and away from a fixed cooperating plate forming the opposite side of a capacitive circuit. The center portion or mass of the center plate is suspended from its rim by means of a large number of integral fingers extending from the rim to the top and bottom surfaces of the center portion. This center mass includes a number of through holes to permit the passage of air from one side to the other and may also include grooves to aid in the flow of air. The fixed top plate or lid and the base also have, or may have, grooves to assist in the passage of air. An alternative embodiment includes a smaller number of more compliant fingers to provide a more compliant structure.

Abstract: A linear hydraulic motor includes a piston rod of conventional steel carrying a fragible piston head movable in a cylinder, the head being designed to break away in the event the cylinder wall is punctured and deformed such that a portion of the cylinder wall becomes an obstacle in the path of the piston. Two or more such motors are frequently connected redundantly to one control surface such that if one motor is damaged, the other can continue to perform its function. The piston head is of a brittle metallic matrix material and includes a conventional seal groove formed on its cylindrical surface.

Abstract: A direct drive servo valve includes a housing and a series of conduits connecting the housing to a fluid pressure source and to an associated actuator, a sleeve in the housing having a plurality of passageways interconnecting the conduits and a spool valve member rotatable within the sleeve to connect the conduits as desired, the spool valve being rotated by a torque motor. The torque motor rotor is connected to the return side of the fluid pressure source. The sleeve is formed of a series of disks which have a desired pattern of holes therethrough and which are bonded together to create a manifold structure having the desired pattern of passageways. A rotary variable differential transformer is connected to the spool and provides feedback signals to an external circuit controlling the torque motor. A torque rod is connected to the spool and the housing to provide a preload which tends to center or "null out" the spool position when there is no input signal.

Abstract: A level wind system suitable for winding an elongated sonar array onto and off from a storage drum includes a guide member which guides the array into a counterbalanced free pivoting arm having a large radius arcuate section terminating substantially in tangential relationship to said drum and which uses the tension force on the array to continually reposition itself relative to each previous wrap on the drum. A series of rollers are located on the inside surface of the arm to guide the array and to minimize the forces on the array. A pair of spring-loaded rollers are positioned between the storage drum flanges which hold the array in position and prevent slack from developing during power-off situations.

Abstract: A stepper motor shaft position sensor differentiates the current provided when the stepper motor is excited as by a step command voltage. The differentiated current is, in effect, a signature indicative of whether or not the motor shaft has taken a step. If the differentiated current falls below a predetermined level within a predetermined interval the motor shaft has taken a step as indicated by a sensor output at a predetermined logic level. Otherwise, the sensor output is at another predetermined logic level indicating that a step has not been taken and the motor is in a stalled condition. The sensor output is applied to a utilizing means which provides a continuous verification of the steppper motor shaft position.