US 4,728,205 AGranted

Positioning of dampeners in a wire matrix print head

AssigneeCanon Kabushiki Kaisha

InventorsHitoshi Hasumi, Hirofumi Hirano

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Abstract

An impact type dot head for forming a character, symbol or the like by a dot matrix comprises: four printing wires arranged in a line in a wire holder; a guide member to guide the wires in parallel; four drive units each for pushing the rear edge of the wire in its axial direction and allowing the front edge of this wire to be projected to the printing position; and a foredamper consisting of a silicone rubber serving as a vibration damping material attached to the holder along its side surface. The drive unit includes an armature to clap the rear edge of the wire and an electromagnetic member to attract the armature. Each printing wire comprises a long thin-diameter portion on the front edge side, a short thick-diameter portion near the rear edge side and an intermediate taper portion connecting them. A coil spring having a diameter which is larger than the diameter of the front edge of the wire and is smaller than the thick portion is elastically attached to the wire, thereby allowing the wire to be pushed and returned from the printing position to the original portion. The printing wires therefore can be accurately guided with a simple and inexpensive structure and printing noise can be reduced.

Claims6

Dependent claims

An impact type dot head comprising:

a plurality of printing wires;
wire drive means having a plurality of armatures to move said printing wires toward a projecting direction and an electromagnetic member for operating said armatures;
first stopping means having a first surface which is impacted by said armatures when said wires are moved in the projecting direction for limiting movement of said armatures in said projecting direction;
second stopping means having a second surface which is impacted by said armatures when said wires are returned in an opposite direction to said projecting direction for limiting movement of said armatures in said opposite direction;
guide means for guiding said wires movably in said projecting direction and said opposite direction, said guide means including a cylindrical guide portion whose axis is in said projecting direction, positioning means extending radially from said cylindrical guide portion and having a first positioning surface for engaging the first surface of said first stopping means to determine the position of the first surface relative to said guide means in the projecting direction, and a second positioning surface for engaging the second surface of said second stopping means to determine the position of the second surface relative to said guide means in a direction axially opposite from the projecting direction;
and
means engaging and fixing said positioning means, said first stopping means and said second stopping means in a state where said first surface engages said first positioning surface and said second surface engages said second positioning surface.

4 more elements

Dependencies are inferred from the claim text.