Abstract: First and second optical waveguides are provided which extend at one end to one side of an electro-optic plate and are interconnected at the other ends, and the connection point is connected to one end of a third optical waveguide. Light from the third optical waveguide is branched to the first and second optical waveguides, whereas light beams from the first and second optical waveguides are supplied together to the third optical waveguide. The angle of the first optical waveguide to the above-mentioned one side of the electro-optic plate is deviated from 90.degree.. The end face of the first optical waveguide at that side forms a reflecting surface and is connected to one end of a fourth optical waveguide. The other end of the fourth optical waveguide extends to another side of the electro-optic plate.

Abstract: In a closed loop type fiber optic gyro the number of waves of a ramp voltage for providing a phase difference between right-handed light and left-handed light which pass through an optical fiber coil is counted, the ramp voltage is converted into a digital value, and the digital value is used as a fraction of the calculated number of waves of the ramp voltage, thereby improving the accuracy of the azimuth angle being measured.

Abstract: In a fiber optic gyro, the operation of a light source which generates light for input as right-handed light and left-handed light into an optical fiber coil is controlled by the ON/OFF operation of a pulse generated by a logic circuit, thereby reducing the quantity of heat generated in the light source. Preferably, a DC component eliminating circuit is provided at the preceding stage of a synchronous detector for eliminating the ON/OFF frequency component of light. More preferably, a gate circuit is provided at the output side of the synchronous detector to cut off both end portions of the synchronous detector output during the ON state of the light source, thereby removing spike noise.

Abstract: In a fiber optic gyro of a zero serrodyne system employing a linear ramp voltage, a phase difference is provided, by a rectangular biasing voltage of a fixed period, between two rays of light which propagate through an optical fiber coil in opposite directions. Interference light of the two rays of light is detected and the detected output is synchronously detected by the biasing voltage in a synchronous detector. A positive increment and a negative increment in the synchronously detected output are detected by a positive increment detector and a negative increment detector, respectively. The positive and negative increments thus detected are added together by an adder, and based on the added output, a ramp voltage generator is controlled so that a maximum ramp phase shift which is applied to the two rays of light may be an integral multiple of 2 .pi.rad.

Abstract: A modulated phase difference is detected between two rays of light phase modulated by a phase modulator, having propagated through an optical fiber coil in opposite directions and interfering with each other. A ramp voltage controlled in polarity and frequency in accordance with the detected phase difference is generated. The ramp voltage is applied to the phase modulator to control it so that a maximum phase shift of light thereby is 2.pi. k rad (where k=.+-.1, .+-.2, . . . ). To correct the temperature characteristic of the phase modulator, a peak value control circuit creates a reference voltage corrected by a voltage detected by a temperature sensor and controls the peak value of the ramp voltage by the reference voltage, thereby ensuring that the maximum phase shift of light in the phase modulator is always 2.pi. k rad regardless of temperature changes.

Abstract: In a fiber optic gyro in which a biasing phase modulator and a ramp phase modulator are provided at the one end and the other end of an optical fiber coil, a biasing voltage and a ramp voltage are applied to the phase modulators to induce a phase difference between two rays of light which propagate through the optical fiber coil in opposite directions, the interference light is detected by a photodetector, the phase difference component is obtained from the photodetector output by a synchronous detector, and the synchronous detector output is used to control the polarity and the frequency of the ramp voltage, an external signal is added to the synchronous detector, output to fluctuate the frequency of the ramp voltage, or a component of an image frequency spaced apart from the frequency of the biasing voltage by a value twice the intermediate frequency is removed by a subtractor from the synchronous detector output, thereby improving the scale factor of the fiber optic gyro.

Abstract: Light waves are allowed to pass clockwise and counterclockwise through a circuit optical path of at least one loop, and the light waves having passed through the optical path are interfered with each other. Phase modulator is inserted in one end of the circular optical path, by which the light waves are phase modulated. The intensity of the interference light is detected, as an electric signal, by a photodetector. The fundamental wave component of the modulation frequency of the phase modulator, contained in the electric signal converted by the photodetector, is synchronously detected by a first synchronous detector, from which is output a signal corresponding to an input angular velocity. Second and fourth harmonic components of the modulation frequency of the phase modulator, contained in the electric signal, are synchronously detected by second and third synchronous detectors.

Abstract: After a metallic cylindrical tube is bulged to form a bellows with a circular cross section, this bellows is ovalized to form a bellows with an oval cross section. For this reason, an inexpensive round tube (cylindrical tube) can be used as the material for a bellows with an oval cross section and it is unnecessary to use an expensive oval tube. Accordingly, a bellows with an oval cross section can be produced at low cost.

Abstract: This invention relates to an apparatus for manufacturing a T-joint, which consists of a tube portion and a collar portion, by using burring techniques. The apparatus is provided with a high-frequency induction heating unit for heating the circumferential portion of a pilot hole made in a tube, a cooling ring for ejecting a coolant to the circumferential portion of the pilot hole, and a temperature distribution control for controlling the heating rate of the heating unit and the coolant ejection rate of the cooling ring. The apparatus thus constructed enables the working temperature of the parts of the circumferential portion of the pilot hole in the plane of which includes the axes of the tube and the collar to be lower than that of the parts of the circumferential portion in the plane extending at right angle to the above-mentioned plane.

Abstract: A method and apparatus for increasing a thickness of a tubular member which ensures a uniform thickness increase of the tubular member and a reduction of an increase in a thickness on an inner diameter side of the tubular member. A portion of the tubular member is subjected to upsetting by applying thereto a compressive force in an axial direction of the tubular member, while the portion is being heated locally and progressively so that a surface layer of the portion of the tubular member reaches a high temperature and a thermal gradient is generated between inner and outer diameter portions of the tubular member. A loading arrangement is provided which is adapted to apply a compressive force in the tubular member in an axial direction thereof, with an annular heater being arranged around an outer circumference of the tubular member. The annular heater is capable of being moved in an axial direction of the tubular member and a control device is provided for controlling a temperature of the heater.

Abstract: A key-board switching unit for electronic instruments is constructed with a printed circuit board provided with a plural number of pairs of fixed contact points on the surface and an insulating covering sheet member mounted on or above the printed circuit board and provided on the bottom surface with movable contact points to face the fixed contact points.

Abstract: A fluid pressure reducing device having a core provided with a peripheral spiral groove and a pipe receiving the core. The portion of the pipe receiving the core is radially contracted so that the ridges of the spiral groove of the core intrude into the inner peripheral surface of the pipe, thereby to form a spiral passage between the pipe and the core. The pressure of a fluid is reduced as the latter flows through the spiral passage. This fluid pressure reducing device is easy to produce and permits an easy fine adjustment of the flow resistance.

Abstract: The invention provides a novel composition capable of giving an electrically conductive, flexible shaped body having stability in the applied voltage vs. current performance. The composition comprises an electrically insulating polymeric material having flexibility such as a diorganopolysiloxane, a finely divided particulate or fibrous metallic silicon such as a finely powdered semiconductor grade high purity metallic silicon dispersed in the insulating polymeric material as the matrix and an organosilicon compound having at least one functional group directly bonded to the silicon atom or at least one peroxy linkage directly bonded to the silicon atom in a molecule.

Abstract: Improved mold release is obtained in a styrene polymer by incorporating a mixture of fatty acid and metal fatty acid salt.