Line feed mechanism for printer

In a high speed printer mechanism wherein a carriage-mounted dot matrix print head;

• having a plurality of selectively actuable and logic controlled print wires, is reciprocally driven back and forth in close proximity to and successively along different line printing paths extending across the width dimension of a print medium which engages and is driven by a rotatable shaft mounted platen, and wherein a reversible inked ribbon is interposed between the print head and the print medium for transferring dot matrix character images to and imprinting them on said medium while the latter is drawn taut against said platen, said combination further comprising:
• a rotatably driven and selectively reversible lead screw coupled to said carriage for driving said print head reciprocably across the width dimension of said medium;
• and
• a line feed mechanism for periodically coupling said rotatable platen to said lead screw in a manner that correlates the lateral displacement of said carriage with both the angular displacement of said platen, and the linear advancement of said print medium engaged by and drawn over said platen, said line feed mechanism including:
• coupling means including a platen gear coupled to the shaft of said rotatable platen of the printer, said platen gear being mounted for arcuate movement in a plane transverse to the axis of said platen shaft while remaining continuously rotatably coupled thereto;
• drive means including a drive gear rotatably coupled to said lead screw and a second intermediate gear continuously coupled to said drive gear;
• first controllably displaceable means for rotatably supporting said platen gear about said platen shaft;
• ratchet means positioned near one end of and rotatable with said platen;
• second controllably displaceable means mounted so as to selectively engage said ratchet means;
• a selectively energizable solenoid having a dual pivotal armature, one end of said armature responsively engaging said first displaceable means and the opposite end of said armature being responsively coupled to said second displaceable means, said solenoid when energized in a correlated manner with the advancement of said carriage, causing said armature thereof to be displaced from a first to a second position and thereby causing said first means engaged therewith to be displaced from a first position whereat said platen gear mounted thereon is out of engagement with said intermediate gear to a second position whereat said gears are in coupling engagement, thus causing said platen to rotate with said drive and intermediate gears and advance the print medium engagingly drawn thereover, and the armature of said solenoid when energized further causing at least in part said second means coupled thereto to be displaced from a first position in engagement with said ratchet means to a second position out of engagement with said ratchet means so as to release said platen for rotation.

A compact, mechanically driven line feed printer mechanism for use in selectively rotating a platen to advance a print medium drawn thereover one or more line spaces at a time, said mechanism comprising:

• coupling means including a platen gear adapted for coupling to an associated shaft of a platen, said platen gear being mounted for eccentric displacement relative to the axis of the platen shaft while remaining continuously coupled thereto;
• drive means including a rotatably driven drive gear;
• first controllably displaceable means for rotatably supporting said platen gear coaxially of said platen shaft;
• ratchet means adapted for mounting on and rotation with the associated platen shaft;
• second controllably displaceable means mounted so as to selectively engage said ratchet means;
• and
• selectively energizable line feed actuator means responsively coupled to both said first and second displaceable means, said actuator means when energized in a correlated manner with said driven drive gear, causing said first means to be displaced from a first position whereat said platen gear is out of engagement with said drive gear to a second position whereat said gears are in coupling engagement, thereby imparting rotational movement to the associated platen then coupled thereto, and said actuator means when energized further causing at least in part said second means to be displaced from a first position in resiliently holding engagement with said ratchet means to a second position out of engagement with said ratchet means so as to release the associated platen for rotation.

In a printer having a rotatably driven drive gear, an improved line feed mechanism of the type responsive to a line feed signal for selectively effecting single or multiple line feed modes of a rotatable platen wherein the improvement comprises:

• a rotatable gear, the axis of which is shiftable between first and second positions, the gear being normally out of engagement with the drive gear and generally concentric with the platen at the first axis position, and being in engagement with the drive gear and eccentric relative to the platen at the second axis position;
• means for normally inhibiting free rotation of the platen;
• coupling means for continuously coupling the gear to the platen for rotation therewith and for permitting the gear to rotate eccentrically relative to the platen;
• means responsive to a line feed signal for shifting the gear axis to the second position to rotate the platen;
• and
• means responsive to a line feed signal which persists for a time longer than that required to effect the single line feed mode of the platen for disabling the inhibiting means so that the platen may freely rotate in the multiple line feed mode until cessation of the line feed signal.