Abstract: A liquid level indicator apparatus provides direct readout of liquid level at high resolution using an array of vertically disposed Hall-effect magnetic switches. To overcome the limit to closer spacing of the switches imposed by their vertical dimension, they a disposed side by side horizontally and vertically by a distance less than the vertical dimension of each switch. They are mounted on a flat flexible substrate and then bent around into a hollow cylinder or prism shape. A floating magnet of annular shape surrounds the cylinder, or a magnet corresponding to the cylindrical or prismatic shape floats inside the surrounding circuit board. Several circuits are shown for displaying a liquid level readout resulting from the actuation of the switches by the magnet.

Abstract: A velocity fuse for a hydraulic line shuts off fluid flow when the flow rate exceeds a preset flow value. The shut off value may be adjusted while the fuse is mounted in the hydraulic circuit. A damping mechanism of the dash pot type prevents the fuse from responding to flow surges of short duration. A poppet or piston within a tubular housing reciprocates between an open position held by a spring and a closed position when flow through an adjustable aperture causes a great enough pressure drop to overcome the spring bias. The damping mechanism is unaffected by the flow rate setting.

Abstract: Sensors for mounting in fluid chambers respond electrically to low pressures in the fluid, while resisting damage or leakage at high pressures. A flexible diaphragm, mounted at one end of a housing, is sandwiched between first and second annuli, leaving a center portion free to move in response to fluid pressure changes. The diaphragm moves a cylinder, which reciprocates in the second annulus against an adjustable spring bias. Travel of the cylinder away from the fluid is limited by a stop. Once the stop is reached, increased pressure on the diaphragm forces it against a fixed wall composed of a face of the second annulus and a face of the cylinder. The forces on the diaphragm are then all compressive. This enables the use of an easily flexed diaphragm for low pressure sensitivity, while resisting damage from high pressures. The moving cylinder is used to move a magnet that actuates a Hall effect switch, a Hall effect analog output transducer, or a reed switch.

Abstract: A target flow meter has a target with a broad face attached to the free end of an elastic stalk. The stalk has at least a portion with an oblong cross section. A fixed end of the stalk is attached to a rigid support secured in the system to be measured with the broad face disposed transverse to the fluid flow. Strain gauges are affixed to the longer sides of the oblong portion. A temperature sensor may also be affixed there. The strain gauges are immersed in the fluid to be measured. Wires to the gauges and sensor pass through a fixed seal to the outside. They may be protected from the fluid by an impervious coating. By applying the strain gauges within the fluid, the system may be reduced in size, achieve greater sensitivity, and better temperature compensation.

Abstract: A fluid fuse is operable to shut off fluid flow only when a certain predetermined volume of fluid has passed through in a single operative cycle. This can then be reset by dropping the inlet pressure. The device protects a hydraulic system from line rupture while automatically resetting after every routine operative cycle when less than the predetermined volume flows. A cylinder has a large diameter bore portion and a small diameter bore portion and holds a sliding piston with large and small diameter segments sealed to respective bore portions by sliding seals. An annular fluid chamber between the seals is reduced in volume as the piston, during fluid flow, moves from a reset position toward a closed position. In the closed position a valve member at the end of the small diameter segment seals off fluid flow as it engages a valve seat at the outlet. Fluid from the annular chamber passes to the outlet through an axial passage in the piston so that the piston may advance.

Abstract: A control system for an electromagnetic device prevents overheating of the coils to permit optimizing design parameters without the need for excessive safety factors. A pull coil circuit feeds a high current to pull windings for a preset time interval after receipt of an initiating voltage. A hold coil circuit feeds a holding current to holding windings with a reduced flux after receipt of an initiating voltage only if it exceeds a preset voltage threshold. The hold current is cut off when the initiating voltage falls below a preset threshold. The pull coil circuit is rendered inoperative for a preset time interval after current is discontinued to ensure adequate cooling between operations.

Abstract: A hydraulic damper has a dashpot piston reciprocating in a cylinder bore. Piston rods extend axially from both sides of the piston. Sealing structures at both ends of the cylinder connect to the cylinder and sealingly engage the piston rods to form two symmetrical hydraulic working chambers divided by the dashpot piston. A narrow passage through the piston provides a restricted fluid flow path between the two working chambers for hydraulic damping of piston motion. A cavity in the first piston rod is provided with a spring-biased, sliding reservoir piston forming a pressurized hydraulic fluid reservoir connected to the midpoint of the narrow passage between working chambers by a narrow conduit. Both narrow passage and conduit have fixed dimensions and no valves. A cavity in the second piston rod contains a spring centering mechanism.