Printer having swingable printing rings

Printer having a plurality of rotatable printing rings each bearing on the periphery thereof a plurality of printing characters and a platen, each of said printing rings being individually moved selectively by means of a driving shaft driven by a driving motor toward said platen after selection of a desired character from said plurality of characters during the rotation of each printing ring upon issuance of a printing signal from a control circuit of said printer so to permit a line of printing of desired characters to be given on a paper located around said platen between said platen and said printing rings by the abutment of the respective printing rings against said platen during a predetermined number of revolution of said driving shaft, wherein the improvement comprises in combination a gear integral with each printing ring, a plurality of swingable printing ring supporting levers each having a shaft secured to the free end of said lever, said shaft rotatably supporting the respective printing ring, each of said printing ring supporting levers being biased by a spring so as to be swung in the direction to move said printing ring supported thereon away from said platen, a plurality of driving gears secured to said driving shaft and each meshing with said gear of the respective printing ring so as to rotate the latter about the axis of said shaft for selection of a desired character by said printing signal, each printing ring supporting lever being swingably supported on said driving shaft so as to permit each printing ring to move in orbital path around said driving shaft and abut against said platen, a plurality of driving levers swingably supported on said driving shaft and each biased by a spring in the direction in which said printing rings are moved toward said platen, each of said driving levers engaging with the respective printing ring supporting lever so as to urge said printing ring thereon toward said platen against the action of said spring of said printing ring supporting lever, a plurality of select levers each releasably arresting the respective driving lever at a position in which each printing ring is held apart from said platen by the engagement of the respective printing ring supporting lever with said driving lever, a plurality of electromagnetic members selectively actuated for a short time by said control circuit upon issuance of the printing signal and each coupled with the respective select lever so that, when the respective electromagnetic member is actuated in synchronism with the selection of said desired character during the rotation of said printing ring, said select lever coupled therewith is moved to release said driving lever arrested thereby so as to permit the same to be swung by said spring thereof for urging said printing ring supporting lever to move said printing ring thereon toward said platen, stopper means for limiting the swinging movement of each driving lever to a position whereby said printing ring supporting lever is swung further together with said printing ring thereon by virtue of the inertia thereof against the action of said spring thereof after said driving lever is stopped by said stopper means thereby permitting said printing ring to abut against said platen for the printing operation while the respective printing ring supporting lever is swung back by said spring thereof after the abutment of said printing ring thereof against said platen so as to be held by said driving lever which is held at said stopped position by said stopper means thereby clearing said printing ring from said paper, reset means engageable with the respective driving lever and actuated in synchronism with the rotation of said driving shaft so as to allow each driving lever to be swung for actuating the respective printing ring supporting lever after releasing of said driving lever from said select lever at the beginning of the rotation of said driving shaft while said reset means urges each driving lever upon completion of said predetermined number of revolution of said driving shaft so that the respective driving lever is arrested by said select lever thereof which has restored its initial position by the deactuation of said electromagnetic member thereof to return each printing ring at its initial starting position, signal emitting means rotated in synchronism with said driving shaft, signal receiving means cooperating with said signal emitting means so as to issue an electrical signal each time one cycle of the printing operation is effected by the rotation of said driving shaft, said electrical signal being applied to said control circuit for controlling the starting and stopping of the operation of said printer, a detecting disc rotated in synchronism with said driving shaft and provided with a plurality of slits around the rotational axis thereof corresponding in number to that of the characters on the respective printing ring, and a detecting device cooperating with said slits in said detecting disc for issuing character synchronizing timing signals in timed relationship to the angular phases of the respective characters on each printing ring as it rotates, said timing signals being applied to said control circuit for permitting a desired character of said plurality of characters on each printing ring to be selected for the printing operation during the rotation of the respective printing ring.