This invention involves methods and apparatus relating to the assembly and structure of a dot matrix print head. In the preferred embodiment, the tops of the bobbins, yoke members, and pole pieces are ground flush in a common plane. The common plane is then used as a reference to mount and assembly remaining elements of the print head including the clapper members and backstop for the clapper members. The clapper members are mounted for pivotal movement between first and second positions by a cover member and securing cap. For uniform operation, the pivotal axis are all in the common reference plane on respective bobbin members and the gaps of the clapper members are automatically set to the identical size by intermeshing fingers on the cover and cap members. Additionally, corresponding and abutting surfaces on the bobbins, cover member, and cap member act in concert by the operation of a single screw to properly align, assembly, and adjust the operating parts of the print head.
RELATED APPLICATIONS
This application is a continuation-in-part of U.S. patent application Ser. No. 616,792 filed June 1, 1984, now U.S. Pat. No. 4,587,724, which is a division of U.S. patent application Ser. No. 499,208, filed May 31, 1983 now abandoned, which is a division of U.S. patent application Ser. No. 425,255 filed Sept. 28, 1982, now U.S. Pat. No. 4,401,392, which is a continuation of U.S. patent application Ser. No. 256,032 filed April 21, 1981, now abandoned, which is a division of U.S. patent application Ser. No. 38,724 filed May 14, 1979, now U.S. Pat. No. 4,279,518.
The armature assembly for matrix print heads having a plurality of magnetic drives for a corresponding plurality of print elements is made by providing an annular armature ring and positioning a disc annulus inside the armature ring in a concentric relation thereto; a resilient arm ring is superimposed upon the disc and armature ring so as to establish concentric placement thereto; the arm ring is fastened to the armature ring and the arms of the arm ring to the disc such that the ring arms extend above an annular gap between the armature ring and the disk; subsequent slots are thermally cutting into the disk to obtain individual armature arms, the slots extending into and through said annulus to divide the annulus into individual arms that remain connected to the armature ring on account of the fastening. The disk may have been cut out from the armature ring.
A print head for use in a wire dot printer has a plurality of wires, an armature connected to each of the wires, a core of a magnetic circuit which is disposed in opposing relation to the armature, a resilient member for biasing the armature in a direction in which it is separated from the core, and a rear case disposed so as to cover the upper side of the armature. Each of the wires is driven by the action of the armature which is attracted toward the core when a coil wound on the core is energized. The print head is provided with an armature guide having a resilient stopper disposed between each armature and the rear case to support the armature against the biasing force from the resilient member. Thus, it is possible to support each armature inserted into the armature guide by means of the stopper even more stably during an assembling step carried out before the rear case is mounted. Accordingly, the assembling operation is simplified and facilitated.
In a print head comprising a plurality of magnetic circuits each of which comprises an armature supported by a spring, a permanent magnet for biasing the armature in one direction, and an electromagnet which can be energized so as to cancel the biasing force of the permanent magnet, so that a print wire fixed to the armature may be driven by energizing the electromagnet and thereby driving the armature with the restoring force of the spring. The cross-sectional areas of the paths of magnetic flux between neighboring electromagnet circuits are made uneven. This can be achieved by providing base portions which are common to two electromagnet core portions. Thereby, the print pressure of all the print wires is made uniform and an increase in printing speed and improved print quality can be achieved at the same time.
A head for a wire dot printer wherein the distance between each pair of adjacent armatures in a circumferential direction of a housing can be minimized to allow reduction in size of the head. The head includes a plurality of armatures each of which has a laterally extending tab formed on one side and a recess formed on the other side of of an outer end portion thereof. A guide member is located between each two adjacent ones of the armatures and has a recess and a tab formed on opposite sides of an outer end portion thereof. The recess and the tab of the guide member fit with the tab of one of the adjacent armatures and the recess of the other adjacent armatures, respectively.
An armature group for mosaic printing head has a plurality of armatures wherein each armature which is part of an actuation electromagnet associated with one of a plurality of printing needles, is fixed to an elastic arm of a spring steel spider having as many arms as there are armatures. The spider, besides performing an armature positioning function allows the armature group to be handled as a unitary element which is easy to assemble. The thrust arm of each armature further has a double bend so that the plane between such arm and the corresponding needle head is perpendicular to the axis of the needle and passes through the fulcrum of the armature. This minimizes the buckling force which the needle has to undergo during the actuation phase. The construction of the armature group can be accomplished by a completely automated manufacturing process.
