Abstract: An apparatus for measuring mechanical strain in a bolt, stud or other tensile member includes a measuring rod which is held in a fixed position with respect to a selected point in an axial bore in the tensile member being measured. A bolt extension tube extends into the axial bore to provide a wrench support function and is held in a fixed position with respect to a second point on the tensile member. Straining the tensile member results in a relative displacement between the rod and the tube which is proportional to tensile member elongation. Means are provided for setting a preselected strain, measuring strain, displaying strain and providing a control signal to control straining of the tensile member.

Abstract: A transistor base drive circuit achieves optimum base current levels to avoid unnecessary transistor power dissipation by including means for diverting excessive base drive from the transistor base to the transistor collector. A capacitor in series with the transistor base decreases switch transition time. Increasing capacitance of the capacitor results in a decrease in transistor saturation voltage, thereby decreasing power dissipation in the transistor.

Abstract: A direct current electric motor marine propulsion system is provided with a pair of shunt wound direct current electric motors which are alternatively connected in a series/parallel circuit configuration. A forward biased diode between the motors in the series circuit, provides for smooth switching characteristics. Fine control of low speed operation is accomplished through the use of a chopper in series with the power source. A contactor connected across the diode provides for reverse current flow during regenerative braking.

Abstract: An electromagnetic projectile launcher is provided with a magnetic field in the path of the projectile. This field induces currents in conductors within the projectile or interacts with a magnetic projectile to produce a torque which imparts spin stabilization to the projectile. Arcuate conductive rails are brought together to form a cylindrical bore to accommodate the cylindrical projectile necessary for spin stabilization.

Abstract: An arc welding process is provided with a preheating step in which a consumable wire electrode is heated prior to insertion into the electrode stick-out region. This is accomplished by the circulation of current from a preheating power supply through a segment of the wire. Both gas-metal and gas-tungsten arc welding processes are disclosed, along with apparatus used in these processes.

Abstract: A voltage regulator for aircraft generators controls generator output voltage by controlling exciter field current. Exciter field current sensors and generator output voltage sensors produce control signals which are proportional to exciter field current and generator voltage. These signals are combined and compared with a reference voltage signal by a comparator. A current controller regulates exciter field current in response to the comparator output.

Abstract: A method is disclosed for preparing a silicon carbide-coated substrate without subjecting the substrate to unnecessary thermal stress. A coating of a silicon carbide precursor polymer is placed on a substrate and the coating is subjected to a laser beam of sufficient energy to raise the temperature of the coating in the area of impingement of the laser beam to approximately 1200.degree. C. to 1600.degree. C. until the coating is converted into a silicon carbide ceramic material. The area of laser beam impingement is located in an inert atmosphere or vacuum while the reaction is taking place.

Abstract: A pole switch firing control for a pulse width modulated inverter controls pole switch operation under steady state operating conditions such that the inverter output duplicates a reference signal waveform after a fixed time delay. Pole switch operating time for a given pulse in an inverter output cycle is measured and subtracted from a fixed time interval to get a delay time. In the succeeding output cycle, the corresponding pulse is produced by initiating the pole switch operating sequence after the delay time, thereby causing the pole switch to operate a fixed time following the reference signal.

Abstract: a multiphase AC current of one frequency is converted to a multiphase current of another frequency by a frequency changer having its output terminals terminated by a load having the impedance characteristics of a voltage source. In this arrangement the multiple phases of a practical AC current source such as a synchronous generator are connected directly to each load phase, even where the bidirectional switches of the UFC are arranged in pulse groups or a bridge configuration.

Abstract: An electromagnetic projectile launching system is provided with a rail configuration in the breech area which increases the electromagnetic field to increase armature acceleration and initiate sliding current transfer at a lower current. Two configurations are disclosed. The first comprises multiple rails disposed parallel to the launcher barrel rails in tne breech region and connected in series such that current in the multiple rails flows in the same direction as current in the closest barrel rail. Connecting shunts are disposed in equal numbers on opposite sides of the barrel rails to balance electromagnetic forces. The second configuration comprises nonparallel barrel rails containing a bend in the breech region.

Abstract: An elongated armature can be moved rectilinearly but is preferably rotated between a first position in which it bridges the gap between two parallel rails to short circuit a very large DC current applied to one end of the rails and a second position where electrical contact with one rail is interrupted. Interruption of the circuit through the armature generates a massive arc which is driven by electromagnetic forces toward the second ends of the rails. Means are also provided for rapidly increasing the voltage across switch terminals to either more rapidly commutate the current into a secondary circuit and/or to more rapidly cause arc extinction. The switch is particularly useful for projectile launcher systems where the armature can be continuously rotated for burst firing. Preferably, the launcher rails are longitudinal extensions of the switch rails so that the arc initially produced by switch opening or armature rotation can be used directly in arc driving of projectiles.

Abstract: An electrical resistance heater controller is provided with a plurality of circuit branches connected in parallel with each other and in series with a heating element and an external AC power source. Each circuit branch includes the series connection of a capacitor and a solid state switch. The switches are controlled by a gating device to switch during the zero crossing of the AC source voltage waveform. Power delivered to the heating element is controlled by varying the amount of series capacitance in the circuit.

Abstract: An electromagnetic projectile launching system is provided with an automatic plasma armature formation device. An arc created when a conductive armature breaks contact with a pair of conductive rails is commutated through an aperture in one of the rails to a second pair of conductive rails where the arc is used as a plasma driving armature to propel a projectile.

Abstract: The cylindrical rotor of a switch for switching very large DC currents has a conducting element extending arcuately over a portion of its cylindrical surface and axially therealong. Two stationary brush members extend radially inward toward and axially along and are in sliding electrical contact with the cylindrical rotor surface. An arc chamber formed in the insulation between the brush members and extending arcuately around the rotor from one of the brush members accommodates the massive arc which is drawn as the rotor is rotated from a first position in which the conducting element shorts the brush members and conducts therebetween the very large current applied to the brush members and a second position in which contact between the rotor conducting element and the one brush member is broken. In one embodiment of the invention, the rotor conducting element shorts the second brush member to a third when the rotor is in the second position.

Abstract: A high reliability electrical power system is provided with a microprocessor-based control unit which maintains power output and performs control functions for the system which is driven by the power system. A self locking feature prevents the transmission of potentially erroneous control signals if a component of the system being controlled or the control unit fails. The control unit conducts a series of self-test routines which result in the generation of digital key words. If the correct key words are generated and the other circuits of the control unit are operating properly, the control unit output remains operative. If the self test routines detect a failure in the system being controlled or the control unit or if a failure occurs in one of the control unit output circuits, the control unit output is locked into a predetermined state.

Abstract: A self-cooled rotating electrical machine is provided with multiple axial and radial coolant passages. Wedges within the interpolar spaces of a salient pole rotor provide an axial coolant path which receives coolant deflected by vanes on the end of the wedges. Coolant expelled at the center of the wedges passes through axial passages in the stator and through a gap between the rotor and stator. Impeller tabs on the ends of the wedges force coolant around stator windings. Recirculation of coolant is prevented by shrouds attached to the ends of the wedges.

Abstract: A solid state relay is provided with a control logic circuit which receives a low level input control signal and controls at least two power field effect transistor (FET) switching elements by means of optical isolators. Break-before-make operation is accomplished by a logic circuit which momentarily turns off all FET's each time the relay is switched. Connecting an external power source to a function selecting input terminal causes the relay to operate as a normally open, normally closed, or latching relay. A voltage spike suppression network protects the FET from voltage spikes appearing across it. FET turn off time is reduced by using a Zener diode to limit maximum gate voltage.

Abstract: A solid state relay is provided with a control logic circuit which receives a low level input control signal and controls a power field effect transistor (FET) switching element by means of an optical isolator. Connecting an external power source to a function selecting input terminal causes the relay to operate as a normally open, normally closed, or latching relay. A voltage spike suppression network protects the FET from voltage spikes appearing across it.

Abstract: A direct current power controller for use in electrical control systems such as aircraft control circuits. The controller utilizes a field effect transistor (FET) as the switching element. A bias voltage supply circuit powers a gate driving circuit, current limiting circuit, and trip indicating circuit. Gate driving circuitry is not directly connected to the system ground, thus minimizing load interference with controller performance and eliminating the need for level shifting circuitry. Remote control circuitry is provided.

Abstract: An electrical switch for use in alternating current circuits is constructed to provide slow contact separation and positive switch action. A pivotally mounted operating handle accepts a pivot pin at one end of a link member. A pivot pin at the other end of the link member fits into a brush lifter. Angular motion of the operating handle produces rectilinear motion in the brush lifter which results in opening and closing the switch contacts. A unique arc shield which encircles one out of each pair of contacts, protects the switch mechanism from destructive effects of contact arcing.