Abstract: An opaque silica glass article comprising a transparent portion and an opaque portion, wherein the opaque portion has an apparent density of 1.70-2.15 g/cm3 and contains 5×104-5×106 bubbles per cm3, said bubbles having an average diameter of 10-100 &mgr;m; and the transparent portion has an apparent density of 2.19-2.21 g/cm3 and the amount of bubbles having a diameter of at least 100 &mgr;m in the transparent portion is not more than 1×103 per cm. The opaque silica glass article is made by a process wherein a mold is charged with a raw material for forming the opaque portion, which is a mixture comprising a silica powder with a small amount of a silicon nitride powder, and a raw material for forming the transparent portion so that the two raw materials are located in the positions corresponding to the opaque and the transparent portions, respectively, of the silica glass article to be produced; and the raw materials are heated in vacuo to be thereby vitrified.

Abstract: An opaque silica glass article comprising a transparent portion and an opaque portion, wherein the opaque portion has an apparent density of 1.70-2.15 g/cm3 and contains 5×104−5×106 bubbles per cm3, said bubbles having an averaged diameter of 10-100 &mgr;m; and the transparent portion has an apparent density of 2.19-2.21 g/cm3 and the amount of bubbles having a diameter of at least 100 &mgr;m in the transparent portion is not more than 1×103 per cm3. The opaque silica glass article is made by a process wherein a mold is charged with a raw material for forming the opaque portion, which is a mixture comprising a silica powder with a small amount of a silicon nitride powder, and a raw material for forming the transparent portion so that the two raw materials are located in the positions corresponding to the opaque and the transparent portions, respectively, of the silica glass article to be produced; and the raw materials are heated in vacuo to be thereby vitrified.

Abstract: Opaque quartz glass is provided which contains gas bubbles uniformly dispersed therein and is excellent in high-temperature viscosity and heat-insulating property. The opaque quartz glass has a defined apparent density, contains bubbles having a defined average bubble diameter in a defined amount, has a defined total bubble sectional area, generally exhibits a defined linear transmittance at a thickness of 1 mm or larger to projected light of a defined wavelength and contains nitrogen in a defined concentration. The opaque quartz glass is produced by a process comprising packing into a mold a powdery source material of powdery silica having a defined average particle diameter and powdery silicon nitride dispersed therein in a defined amount, heating the powdery source material to one of two first defined temperature ranges (both under vacuum) and further heating the source material up to a second temperature higher than the melting point and not higher than 1900.degree. C.

Abstract: An engine output control and a constant vehicle speed control switch adapted to effect easy release of the control. The control comprises a throttle grip, a valve link with a return spring and a constant speed control, and a cable connecting these elements. The switch is connected to the cable and is responsive to the tension of an inner wire of the latter.

Abstract: A constant vehicle speed retaining device for motorcycle, comprising a control mechanism connected to a cable provided between a throttle valve and a throttle grip, for controlling the angle of opening of the throttle valve during the time interval between a constant speed control command and a cancellation command. A set switch generates the constant speed command, and a cancellation switch generates the cancellation command to the control mechanism. The cancellation switch is located near the throttle grip and operates in response to rotation of the latter in a decelerating direction.

Abstract: One feature of the present invention is a battery to be mounted on a vehicle, in which the battery casing is formed with a recess into which a starter magnetic switch is fitted. Another feature of the invention is a starter magnetic switch which can be fitted into the recess formed in the battery. The starter magnetic switch has a rocker means which is made of a conductive material. The rocker means has a moving electric contact which is biased normally open and which is closed when the solenoids built into the switch are energized, to close the drive circuit of a starter motor. The rocking means has one end projecting to the outside of a switch casing and is fastened to the positive terminal of the battery. In addition, a supporting means, which projects to the outside of the switch casing at the side opposed to the portion where the rocking means projects, is fastened to the negative terminal of the battery.

Abstract: An ignition device of the capacitor discharge type for small automobiles or two-wheeled vehicles, having an A.C. generator with a converter which transforms the alternating current supplied by a stator coil into direct current, increasing the voltage. Ignition voltage is provided by a charging control which releases the charge stored in a capacitor with the required timing.

Abstract: A process for producing niobium metal of an ultrahigh purity, which comprises iodizing niobium metal or niobium chloride containing at least tantalum as an impurity, thermally reducing the iodized product, and then thermally decomposing the reduced product.

Abstract: A safety device for a motor-cycle having an engine, a fluid coupling operatively connected to the engine, a power transmission mechanism which receives power from the fluid coupling, the transmission mechanism having at least two-stage speed changing function of low speed drive and high speed drive, and a shift indicating switch means which changes over in association with the shifting operation in the transmission mechanism to indicate the low speed drive, or high speed drive, or neutral position, wherein the improvement comprises a switching circuit provided between the shift indicating switch means and the ignition circuit, the switching circuit forwarding an output signal from it to the ignition circuit, when the shift indicating switch means is changed over to either the low speed drive range or the high speed drive range at the start of the engine, whereby the ignition circuit is rendered inoperable.

Abstract: Proposed in this application is a device for adjusting ignition timing in an engine for a motor-cycle having an engine, an ignition circuit for the engine, a fluid coupling connected to the engine, a power transmission mechanism which receives driving force from the fluid coupling, and shift indicating switch which changes over in association with the power transmission mechanism to indicate a low speed drive, a high speed drive, or the neutral position, wherein the ignition timing adjusting device comprises: a plurality of ignition signal emitters, each having differing signal emission timing and producing an ignition signal output to actuate said ignition circuit when the engine is in a driven state and the vehicle is in a stopped state; and a switching element which, in accordance with change-over operation of the shift indicating switch device, controls in such a manner that any one of the output signals from the plurality of ignition signal emitters may be fed as an input into the ignition circuit.