Abstract: A lens barrel for a camera wherein an outer profile thereof has a reduced dimension in a radial direction of a movable lens and with a lens holding member that can be moved smoothly in a direction of an optical axis of the movable lens held on the barrel. The lens barrel comprises an outer shell having a pair of guide portions provided therein and a lens holding member holding a movable lens thereon. The lens holding member has a pair of guide portions provided at the opposite locations thereof with respect to the optical axis and is supported at the guide portions thereof for sliding movement on the guide portions of the outer shell. The lens barrel further comprises an actuator including a coil securely mounted on the lens holding member and a magnet securely mounted on the outer shell. The coil and magnet are disposed coaxially to each other around the optical axis.

Abstract: A voice coil type actuator comprising a guide shaft formed of a material at least a portion in the radial direction in the cross-section of which is permeable, a movable member slidably supported on the guide shaft, a movable coil supported coaxially with the guide shaft on the movable member, a generally tubular yoke surrounding the movable coil and covering the range of the movement thereof, and a magnetic field generating magnet being contacted with the yoke. An axially extending cutout is formed in the yoke. A portion of the movable member projects through the cutout and supports thereon a displaceable member.

Abstract: A radiation thermometer for measurement of the temperature of molten iron includes a probe tube with a sealed bottom in the form of a spheroidal shape and is made of zirconium boride ceramics. The probe tube is immersed in molten iron and radiation emitted from the spheroidal closed end of the probe tube is received by a sensor at the far end of the tube which is above the level of the molten iron. The spheroidal end of the probe tube is below the surface of molten iron by more than 10 times the inner radius of the probe tube.

Abstract: A voice coil type actuator wherein the length in an axial direction and the number of parts is reduced without deteriorating a required function and the magnetic flux density in a space in which a movable coil is located is substantially uniform over the entire length in an axial direction. The voice coil type actuator comprises a fixed guide shaft having a radial portion made of a permeable material and a movable body supported for axial sliding movement on the guide shaft. The movable coil is supported coaxially with the guide shaft on the movable body. A yoke having a substantially cylindrical profile is disposed in such a manner as to surround a range of movement of the movable coil, and a pair of fixed magnets are disposed in contact with the guide shaft and the yoke and magnetized with the opposite polarities in a radial direction.

Abstract: A two-phase brushless motor has a rotor comprising at least a pair of first magnetic poles and a pair of second magnetic poles which are smaller in width than the first magnetic poles, and a stator comprising at least a pair of first coils and a pair of second coils for producing a first phase and a second phase of varying magnetic fields, respectively, so that the torques respectively obtained from the interaction of the two pairs of magnetic poles and the two phases produced by the two pairs of coils differ from each other.

Abstract: A three-phase brushless motor in which two electromagnetic transducer elements for detecting the rotational position of a rotor are disposed so as to produce a composite signal having a phase difference of 120.degree. relative to the output signals from the electromagnetic transducer elements, and the output signals from the two electromagnetic transducer elements and the composite signal are used to determine drive currents fed to the stator coils. The rotor includes auxiliary magnetic poles having opposite polarities to those of main magnetic poles and are disposed in the rotor opposite the electromagnetic transducer elements at positions with an electrical angle of .+-.45.degree. from the boundary between respective North poles and South poles of the main magnetic poles, whereby waveforms of the composite signal and the output signals from the electromagnetic transducer elements have a steep slope at zero crossing points.

Abstract: The present invention relates to a three-phase brushless motor in which two electromagnetic transducer elements for detecting the rotation position of a rotor having a plurality of magnetized regions are disposed to have a relative positional relation with an electrical angle of 120.degree. or 240.degree., a composed signal having a phase difference of 120.degree. relative to the output signals from the electromagnetic transducer elements is provided and the drive current to be supplied to the stator coil is determined on the basis of the composed signal and the output signals from the electromagnetic transducer elements. An auxiliary magnetic pole having opposite polarity to that of main magnetic pole is disposed on the rotor at the portions near and opposing to the electromagnetic transducer elements so as to make the waveform of the composed signal of the output signals from the electromagnetic transducers steep at zero-cross points.

Abstract: An ignition spark timing control system for an internal combustion engine, which comprises a reference angle signal generator to generate reference angle signals corresponding to the reference angles of each cylinder of the engine, a divider for dividing the reference angle signals to produce divided signals, and voltage-advance converters substantially operated in an alternative manner in response to said divided signals to control ignition spark timing in dependence on an advance control signal.