Armature supporting structure of a print head

#The present invention relates to a print head in which print wires are moved to a printing position by swinging armatures by means of energized coils, and more particularly, to an armature supporting structure thereof.

#Conventionally, in some conventional print heads of this type, a plurality of armatures are swingably supported on a head body by means of leaf springs, individually, and print wires are moved to a printing position by swinging the armatures.

#In these conventional print heads, however, the armatures are supported with the aid of the leaf springs, which are bound to suffer a prolonged high-order vibration, after the printing wires strike against printing paper, or after they return to a rest position after printing operation. Thus, it takes the leaf springs much time to be restored to their original position. As a result, the printing cycle becomes too long for high-speed printing.

#FIGS. 1 to 6 show a first embodiment of the present invention, in which

#FIG. 1 is a partial exploded perspective view showing a principal part of a print head,

#FIG. 2 is a cutaway side view of the print head,

#Referring now to FIGS. 1 to 6, a first embodiment of the present invention will now be described in detail.

#As shown in FIGS. 2 and 3, a body 11 of a print head, which is made of a magnetic material, has a circular recess 12 opening toward a platen 31. A bottom wall and a cylindrical outer peripheral wall of the head body 11 constitute a rear yoke 13. A flange portion 13a extends outward from the platen-side end face (hereinafter referred to as a front end face) of the rear yoke 13. The flange portion 13a has a rectangular configuration, as viewed from the platen side, including top and bottom sides, extending parallel to the axis of the platen 31 or the traveling direction a carriage (not shown) carrying the print head thereon, and two lateral sides extending at right angles to the top and bottom sides. A plurality of electromagnetic devices 14 are arranged in a ring, on the bottom surface of the recess 12. Each electromagnetic device 14 is composed of a core 15 protruding integrally from the head body 11, a coil bobbin 16 fitted on the core 15, and a coil 17 wound around the bobbin 16. The respective cores 15 of the devices 14 are arranged at regular angular intervals on the head body 11.

#A platelike permanent magnet 18 is fixedly bonded to the front face of the rear yoke 13. As shown in FIG. 4, the permanent magnet 18 is formed of a pair of half pieces 19 and 20 arranged symmetrically. The paired pieces 19 and 20 are fixedly bonded to each other at their facing end portions. Each of the pieces 19 and 20 has the same rectangular external shape as the flange portion 13a of the rear yoke 13. The permanent magnet 18 is formed with a center opening 21, which is concentric with the circle along which the cores 15 are arranged. Having a rectangular external shape, the magnet 18 is additionally long in its diagonal direction. Even if its width or side length is minimized, therefore, the whole permanent magnet 18 can secure a satisfactory magnetic force.