Line spacing device for printing machines

A bidirectional line spacing device for printing machines comprising a paper support platen having a toothed wheel synchronous with said platen and provided with peripheral teeth;

• a pawl including a tooth engageable with the toothed wheel for incrementally rotating the paper support platen;
• an eccentric device connected with said pawl;
• a motor having a rotor rotatably connected with said eccentric device for moving the tooth of the pawl according to a predetermined trajectory, wherein said trajectory has one part which interferes with the teeth of the toothed wheel for the rotation of the platen and another part external to the toothed wheel and inoperative on said platen;
• an indicator which defines a first and a second angular zone of the eccentric device, wherein the positions of the eccentric device within said first angular zone are associated with positions of the tooth disengaged from the toothed wheel and included in said other part of the trajectory and wherein the positions of the eccentric device within said second angular zone are associated with positions of the tooth included in said one part of the trajectory;
• a circuit controlled by said indicator which energizes the motor to cause the rotor to selectively rotate the eccentric device in the two directions of rotation, according to a substantially full rotation starting from a starting position within said first angular zone, through said second angular zone and until a final position within the first angular zone of the indicator is reached, in order to cause the tooth to travel, in one or the other direction, through said one part of the trajectory which interferes with the toothed wheel thereby to cause corresponding incremental rotations of the platen in the two directions;
• and a positioning detent which solely and exactly positions and arrests the platen in given line spacing positions associated with the reached line spacing position corresponding to the disengagement of the pawl tooth from the toothed wheel and irrespectively of the direction of rotation and the starting and final position of the eccentric device, wherein said positioning detent comprises a lever mounted on pivot means including a detent element and operated by a spring and wherein said spring causes the detent element to engage the teeth of said toothed wheel for positioning and arresting said platen.

A bidirectional line spacing device for printing machines comprising a paper support platen having a toothed wheel;

• a pawl including a tooth for incrementally rotating the paper support platen;
• and eccentric device connected with said pawl;
• a motor having a rotor rotatably connected with said eccentric device for moving the tooth of the pawl according to a predetermined trajectory, wherein said trajectory has a part which interferes with the toothed wheel and another part external to the toothed wheel;
• an indicator which defines a first angular zone of the eccentric device which is associated with positions of the tooth disengaged from the toothed wheel;
• a circuit controlled by said indicator which energizes the motor to cause the rotor to selectively rotate in the two directions of rotation, until the first angular zone of the indicator is reached in order to cause the tooth to travel, in one or the other direction, through the part of the trajectory which interferes with the toothed wheel thereby to cause corresponding incremental rotations of the platen in the two directions;
• a positioning detent which arrests the platen in the reached line spacing position corresponding to the disengagement of the pawl tooth from the toothed wheel;
• and a cam synchronous with said eccentric device;
• wherein the positioning detent comprises a spring, a positioning element urged by said spring and engageable with the toothed wheel for maintaining the platen in the position to which the platen has been moved and a cam follower lever;
• and wherein said cam engages said cam follower lever during the rotation of the rotor of said motor for releasing said positioning element from the toothed wheel before the engagement of the tooth of said pawl with the toothed wheel.

In a line spacing device for a typewriter, comprising a paper supporting platen, a toothed wheel connected to rotate with the platen, a pawl having a tooth arranged to cooperate with the toothed wheel, a motor, an eccentric control member rotated by the motor and carrying the pawl to impose on the tooth a trajectory having a part which interferes with the toothed wheel, a position indicator associated with said eccentric control member, a positioning detent urged by a spring for arresting the platen in predetermined line spacing positions, and a cam member mounted for rotation with said eccentric control member, said cam member engaging a cam follower attached to said positioning detent to retract said detent from said toothed wheel, wherein;

• the motor is of reversible type and the teeth of the toothed wheel and the tooth of the pawl have shape enabling said platen to be rotated bidirectionally in accordance with a bidirectional movement of the tooth of said pawl along its trajectory,
• said positioning detent comprises a lever having a detent element which cooperates with said toothed wheel under the action of said spring, and said position indicator generates a signal having a first and a second status wherein the first status of said signal corresponds to given angular positions of the eccentric control member wherein the tooth of said pawl is disengaged from the toothed wheel and wherein the second status of said signal corresponds to remaining angular positions of the eccentric control member including positions wherein the tooth of said pawl is engaged with said toothed wheel, and further comprising
• a circuit actuatable for selectively driving said motor in one of the two directions of rotations, for bidirectionally actuating the line spacing of said platen,
• wherein said circuit responds to the first status of said signal to start with the rotation of said eccentric control member from one of said given angular positions, to the switching of said signal in the second status to continue with a substantially complete rotation of the eccentric control member through the remaining angular positions, until the first status of said signal is again generated by said position indicator to stop said control member in another of said given angular positions, and wherein said spring causes said detent element to engage the teeth of said toothed wheel for exactly positioning and arresting the platen in the desired line space irrespective of the sense of rotation and the final position of said eccentric control member.