A linear variable differential transformer includes: a moving portion having a shape extending in a direction of an axial line; a bobbin including a through hole formed such that the moving portion is movable in the direction of the axial line, an outer circumferential surface of the bobbin having a shape inclined symmetrically with respect to a center line thereof based on the direction of the axial line; a primary coil wound around the outer circumferential surface of the bobbin; and a secondary coil wound around the wound primary coil, a wound outer surface of the secondary coil having a shape parallel to the axial line.

An actuating device comprising at least one magnetic drive (12) with a solenoid coil (34) which, accommodated in a housing (10), generates heat during operation affecting the performance of the device, wherein said heat is dissipated at least partially into the environment as power loss via the housing (10), is disclosed, which is characterized in that, for improved heat dissipation, parts (40, 42) of the device consist of at least one special plastic material, which has a thermal conductivity coefficient of 0.25 to 1.25 W/(m.Math.K).

An actuating device comprising at least one magnetic drive (12) with a solenoid coil (34) which, accommodated in a housing (10), generates heat during operation affecting the performance of the device, wherein said heat is dissipated at least partially into the environment as power loss via the housing (10), is disclosed, which is characterized in that, for improved heat dissipation, parts (40, 42) of the device consist of at least one special plastic material, which has a thermal conductivity coefficient of 0.25 to 1.25 W/(m.Math.K).

A linear actuator includes a magnet housing having first and second planar sides, a front plate and a rear plate, and a base plate covering a channel defined by the magnet housing. A first plurality of magnets is secured to the first planar side and a second plurality of magnets is secured to the second planar side. A linear guide slidably secured to an inner surface of the base plate. A piston assembly has a piston element attached to the linear guide. The piston assembly includes a shaft and a printed circuit board attached to the piston element. The printed circuit board defines a controller and a printed coil assembly. A flex cable is electrically connected to the printed circuit board. The piston assembly is disposed to move linearly during operation of the linear actuator.

A linear actuator includes a magnet housing having first and second planar sides, a front plate and a rear plate, and a base plate covering a channel defined by the magnet housing. A first plurality of magnets is secured to the first planar side and a second plurality of magnets is secured to the second planar side. A linear guide slidably secured to an inner surface of the base plate. A piston assembly has a piston element attached to the linear guide. The piston assembly includes a shaft and a printed circuit board attached to the piston element. The printed circuit board defines a controller and a printed coil assembly. A flex cable is electrically connected to the printed circuit board. The piston assembly is disposed to move linearly during operation of the linear actuator.

An electromagnetic drive device includes a through-hole, through which a rod is received, and the rod includes an outer wall surface that is slidable relative to the through-hole. A clearance, which is measured from the outer wall surface of the rod placed in a maximum projected position to an inner wall surface of the through-hole, is smaller than a clearance, which is measured from the outer wall surface of the rod placed in a maximum retracted position to the inner wall surface. Therefore, a retracting-time clearance becomes relatively large, and thereby a frictional force between the rod and a support tubular portion can be reduced. Furthermore, a projecting-time clearance becomes relatively small, and thereby the amount of swing of a distal end of the rod in a radial direction can be reduced.

An electromagnetic drive device includes a through-hole, through which a rod is received, and the rod includes an outer wall surface that is slidable relative to the through-hole. A clearance, which is measured from the outer wall surface of the rod placed in a maximum projected position to an inner wall surface of the through-hole, is smaller than a clearance, which is measured from the outer wall surface of the rod placed in a maximum retracted position to the inner wall surface. Therefore, a retracting-time clearance becomes relatively large, and thereby a frictional force between the rod and a support tubular portion can be reduced. Furthermore, a projecting-time clearance becomes relatively small, and thereby the amount of swing of a distal end of the rod in a radial direction can be reduced.

The present disclosure relates to a magnetic circuit assembly of a bone conduction speaker. The magnetic circuit assembly may generate a first magnetic field. The magnetic circuit assembly may include a first magnetic element, and the first magnetic element may generate a second magnetic field. The magnetic circuit may further include a first magnetic guide element and at least one second magnetic element. The at least one second magnetic element may be configured to surround the first magnetic element and a magnetic gap may be configured between the second magnetic element and the first magnetic element. A magnetic field strength of the first magnetic field within the magnetic gap may exceed a magnetic field strength of the second magnetic field within the magnetic gap.

The present disclosure relates to a magnetic circuit assembly of a bone conduction speaker. The magnetic circuit assembly may generate a first magnetic field. The magnetic circuit assembly may include a first magnetic element, and the first magnetic element may generate a second magnetic field. The magnetic circuit may further include a first magnetic guide element and at least one second magnetic element. The at least one second magnetic element may be configured to surround the first magnetic element and a magnetic gap may be configured between the second magnetic element and the first magnetic element. A magnetic field strength of the first magnetic field within the magnetic gap may exceed a magnetic field strength of the second magnetic field within the magnetic gap.

The electromagnetic device includes a coil bobbin around which a coil is wound and that is formed from a non-magnetic material, and a movable core that is provided in a cylindrical hollow portion of the coil bobbin and moves by excitation of the coil. A first protrusion and a second protrusion facing a part of the lower half of the movable core are formed on the inner peripheral surface of the cylindrical hollow portion in ranges extending from two openings to a middle point of the coil bobbin, respectively, and the movable core is supported by the first protrusion and the second protrusion when the movable core moves.