Abstract: An apparatus for protecting a linear motor having a structure in which permanent magnets and a coil are subjected to relative movement, comprising (a) a means for detecting current flowing through said coil, (b) a multiplying means for calculating the squared value of the detected current every constant time &Dgr;t, (c) a memory means receiving said squared values for successively storing said squared values from the first one to the nth one, the first squared value being eliminated when the (n+1)th squared value is input, and the same operation being repeated subsequently, (d) an adding means for calculating the total of n squared values in said memory means, (e) a means for setting a reference value, which is to be compared with the total of said squared values, (f) a means for comparing the total of said squared values with said reference value for outputting an overload signal when said total has become larger than said reference value, and (g) an overload-preventing means receiving said overload sig

Abstract: A magnet roll has a plurality of magnetic poles on a surface with at least one magnetic pole portion being composed of an anisotropic bonded magnet including magnet powder and binder resin. The anisotropic bonded magnet contains R—T—N magnet powder, wherein R is at least one rare earth element including Y, Sm being indispensable, and T is Fe or Fe and Co. The R—T—N magnet powder may also contain inevitable impurities such as C, O and H. The binder resin constitutes 20-70% of the volume of the anisotropic bonded magnet such that the anisotropic bonded magnet have a maximum energy product (BH)max of 10 MGOe or more and a residual magnetization Br of 2800 G or more.

Abstract: A magnet roll including a cylindrical permanent magnet having a surface thereon a plurality of magnetic poles which extend along an axis of the magnet roll and an electroconductive ceramic layer formed at least on a circumferential surface of the cylindrical permanent magnet. The electroconductive ceramic layer may be TiC, WC, TiN, TiCN, CrN, ZrN, HfN, Ti+TiN, and Cr+CrN. The magnet roll is used in a developing method of developing a latent image on a photosensitive drum by a magnetic developer while applying a bias voltage to a developing zone, in which the number of the magnetic poles (N) satisfies the relation: N.gtoreq.(V.sub.1 /V.sub.2).times..pi.D/6, wherein V.sub.1 is a peripheral speed (mm/s) of the photosensitive drum, V.sub.2 is a peripheral speed of the magnet roll and D is an outer diameter (mm) of the magnet roll.

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 method for developing electrostatic latent image on a rotating photoconductive drum by a magnetic developer transported by a rotating developing roll disposed opposite to the photoconductive drum, the developing roll being made of a cylindrical permanent magnet having on circumferential surface thereof equispaced magnetic poles extending along the axial direction. In the method the magnetic poles are equispaced by an inter-pole pitch of 0.5-10 mm, the photoconductive drum and the developing roll are rotated so as to move in opposite directions in an developing zone, and the ratio of peripheral speeds of the developing roll and photoconductive drum are regulated within 1 to 5. By the above method, an electrophotographic imaging apparatus can be reduced in the size thereof while reproducing high-quality images.