Abstract: The arm assembly includes an arm member composed of a rotatable boss member; three or more arm plates each formed from a thin, non-magnetic metal sheet and extending in parallel from one side of the boss member; a coil member fixed to the other side of the boss member such that the coil member is swingable in a magnetic gap; and a suspension member having a front end equipped with a recording/reproducing head and a rear end fixed o a free end of each arm plate; wherein pins projecting from upper and lower surfaces of the boss member are fitted into through-holes of an uppermost arm plate and a lowermost arm plate so that the uppermost and lowermost arm plates are strongly fixed to the boss member, and wherein at least one arm plate disposed between the uppermost and lowermost arm plates is integrally fixed to the boss member with a thermoplastic resin.

Abstract: A swing-type actuator has (a) a housing including a pair of yokes and a permanent magnet attached to at least one of the yokes opposing each other for defining a magnetic gap therebetween; and (b) a swingable arm having at one end a hold member encompassing a movable coil, such that the hold member and movable coil have essentially the same thickness and the movable coil is swingable in the magnetic gap, the arm and the hold member being integrally formed of a thermoplastic resin having a longitudinal modulus of 30.times.10.sup.4 kg/cm.sup.2 or more.

Abstract: The swing-type actuator includes (a) a housing comprising a pair of yokes opposing each other and a permanent magnet attached to at least one of the yokes for defining a magnetic gap therebetween, (b) a swingable arm having one end to which a hold member encompassing a periphery of a movable coil is fixed, and the other end to which a function member is fixed, such that the movable coil is swingable in the magnetic gap, and (c) a thin non-magnetic plate adhered to at least part of a surface of the movable coil facing the permanent magnet. The hold member is made of a thermoplastic resin and molded integrally with the movable coil and the arm, and the hold member has substantially the same thickness as that of the movable coil.

Abstract: A swing-type actuator comprising (a) a housing comprising two yokes and permanent magnets attached to the yokes with their different magnetic poles opposing each other, a magnetic gap existing between the opposing permanent magnets; and (b) a swingable arm having one end to which a movable coil is fixed and the other end to which a function member is fixed, such that the movable coil is swingable in the magnetic gap, the movable coil being integrally fixed to the arm by a hold member made of a thermoplastic resin having a modulus of 10.sup.5 kg/cm.sup.2 or more.

Abstract: A focus magnet having (a) three axially magnetized hollow cylindrical permanent magnets disposed concentrically along a center axis of a cathode ray tube such that their opposite magnetic poles face each other; (b) yokes in the form of hollow discs disposed on both sides of the permanent magnets; (c) a static control coil disposed inside a center permanent magnet; (d) a horizontal dynamic control coil disposed inside one of side permanent magnets; and (e) a vertical dynamic control coil disposed inside the other side permanent magnet, whereby electron beams passing in the cathode ray tube are converged to a small spot diameter.