Mosaic printing head with electromagnetically actuated needles with a common yoke for all electromagnets

Claim 2

An electromagnetic drive for the operation of printing needles of a mosaic printing head, comprising a housing having a tubular support portion with a guide for a plurality of needles, a plurality of needles in said guide arranged for substantially axial movement for printing, an annular common magnetic yoke for all of said needles made of magnetic material and being connected to said support portion, said yoke including an outer and an inner annular wall portions located exteriorly of and generally concentric to said needles, said yoke also including a pole piece of magnetic material for each needle arranged in circumferentially spaced locations between said outer and inner wall portions and each having a coil winding, said pole pieces and said outer and inner walls having outer end faces terminating in substantially the same plane, an armature having an outer end pivoted on said outer annular wall portion and overlying said pole piece and the end face of said inner annular wall portion and having an inner end connected to a respective needle, and spring means biasing said armature away from engagement with said pole piece.

Claim 3

An electromagnetic drive according to claim 1, wherein said yoke is made of a single piece, said spring means comprising a coil spring and engaged around a respective needle and urging the associated armature away from the pole piece, and a cover overlying said yoke and having a washer of elastic material overlying the end of said armature connected to said needle, said spring means biasing said armature into engagement with said washer.

Claim 4

An electromagnetic drive, according to claim 1, wherein said armature includes a curved outer end, said yoke outer wall portion having an aRcuate receiving groove extending therearound, said armatures having curved outer ends engaged in the arcuate receiving grooves.

Claim 5

An electromagnetic drive for operating printing needles of a mosaic printing head, comprising a housing including a tubular portion defining a printing needle guide, a plurality of printing needles disposed in said guide and having portions projecting outwardly therefrom, a yoke of magnetic material comprising three upstanding portions including a first inner cylindrical wall portion surrounding the portions of the needles which project out of said housing tubular portion, a second outer cylindrical wall portion surrounding said first inner cylindrical wall portion and spaced outwardly therefrom, a third pole piece portion having a coil winding and a base portion connected to all of said first, second and third portions and extending between said outer cylindrical wall portion and said inner cylindrical wall portion, said third pole piece being an armature pole for each needle disposed between said outer cylindrical wall and said inner cylindrical wall arranged on an arc surrounding said needles, an armature aligned with each pole, each having an inner end pivotally connected to said outer cylindrical wall and extending over its associated pole and having an outer end connected to a respective needle, each pole having an exciting coil therearound which may be energized to attract said armature for moving the associated needle.

Claim 6

An electromagnetic drive for operating printing needles of a mosaic printing head, comprising a housing including a tubular portion defining a printing needle guide, a plurality of printing needles disposed in said guide and having portions projecting outwardly therefrom, a yoke of magnetic material comprising three upstanding portions including a first inner cylindrical wall portion surrounding the portions of the needles which project out of said housing tubular portion, a second outer cylindrical wall portion surrounding said first inner cylindrical wall portion and spaced outwardly therefrom, a third pole piece portion having a coil winding and a base portion connected to all of said first, second and third portions and extending between said outer cylindrical wall portion and said inner cylindrical wall portion, said third pole piece being an armature pole for each needle disposed between said outer cylindrical wall and said inner cylindrical wall arranged on an arc surrounding said needles, an armature aligned with each pole, each having an inner end pivotally connected to said outer cylindrical wall and extending over its associated pole and having an outer end connected to a respective needle, each pole having an exciting coil therearound which may be energized to attract said armature for moving the associated needle.