Mosaic printing head

Claim 1

An impact matrix printing head adapted to be mounted on a printing carriage for providing an impression against a platen, including: a needle guiding assembly, said needle guiding assembly including a plurality of needles; an electromagnet assembly, said electromagnet assembly including a plurality of electromagnetic structures, each of said plurality of electromagnetic structures including a pole piece and an armature; said armature having a lever arm acting on one of said plurality of needles to drive said needle towards the platen; said electromagnet assembly further comprising a supporting ring member provided with a central cylindrical bushing, said supporting ring member including a first locking means to structurally attach said member to the print carriage; the pole pieces of said plurality of electromagnetic structures being fixed on said supporting ring member radially around said bushing; a disk shaped armature retainer having a central portion contacting said bushing and a peripheral portion, said peripheral portion having means for positioning said armatures contiguous to said pole pieces; a circular cap; second locking means for fixing said cap to said bushing through interposition of said central portion of said armature retainer; first resilient means interposed between said cap and said central portion of said armature retainer and adjustably compressed by the action of said second locking means; second resilient means mounted in the central portion of said cap, said second resilient means contacting one end of said armatures, whereby the adjustable compression of said first resilient means allows for the adjustment of the air gap width of said electromagnetic structures, and whereby said first locking means allows for the adjustment of the distance of said electromagnetic assembly from the printing platen.