Cyclically rotatable eccentric pivot for ribbon reverse lever

Claim 2

In combination with a ribbon feed device for an impact printer of the type wherein a printing ribbon is repeatedly wound and unwound between two spools mounted on said ribbon feed device with said ribbon passing over an impact printing position, and where the ribbon bears a ribbon reversing tab at each end which engages a winding spool reversing lever pivotally mounted on said ribbon feed device, wherein the improvement comprises: an eccentric rotatably mounted on said ribbon feed device and serving as the pivot for said winding spool reversing lever, means for rotatably driving said eccentric so as to displace said pivot of said winding spool reversing lever with respect to said ribbon feed device, thereby changing the position with respect to said ribbon feed device, at which said winding spool reversing lever engages said ribbon reversing tab and induces reversal of the spool winding motion, whereby the position along said ribbon is changed where sustained impact printing occurs when the reversal of ribbon motion takes place, thereby reducing ribbon wear.

Claim 3

In a ribbon feed and correction device of the type wherein two winding spools alternately wind a printing ribbon mounted therebetween, said ribbon having a ribbon reversing tab at a longitudinal end thereof to operatively engage an operating end of a reversing lever to reverse the direction of rotation of said winding spools when said ribbon is unwound to said longitudinal end, said winding spools rotatably mounted on a ribbon spool rupport plate which is pivotally mounted to a fixed mounting plate, said ribbon spool support plate undergoing a pivotal displacement with respect to said fixed mounting plate when said versing lever reverses the direction of rotation of said winding spools, said ribbon passing over a printing position fixed with respect to said fixed mounting plate, the improvement made to extend the useful liFe of said ribbon, by reducing the duration of printing impact during said reversal of winding spool rotation, comprising: a ratchet wheel rotatably mounted on said fixed mounting plate, to rotate about a first axis, a detent means mounted on said fixed mounting plate, for operatively engaging said ratchet wheel and preventing rotation thereof opposite to a preferred direction; a pawl means mounted on said ribbon spool support plate, for operatively engaging said ratchet wheel and rotatably advancing said ratchet wheel in said preferred direction when said ribbon spool support plate undergoes said pivotal displacement with respect to said fixed mounting plate; a cylindrical hub rigidly mounted on said ratchet wheel with a second cylindrical axis parallel to but displaced from said first axis, to undergo eccentric motion when said ratchet wheel rotates about said first axis; said reversing lever rotatably mounted on said cylindrical hub so that while maintaining substantially the same general orientation with respect to said fixed mounting plate, said reversing lever undergoes a circular oscillatory motion with respect to said fixed mounting plate, induced by the eccentric motion of said cylindrical hub as said ratchet wheel rotates; whereby the distance between said printing position and said operating end of said reversing lever which operatively engages said ribbon reversing tab, changes as said winding spools change their winding direction, thereby changing the portion of the ribbon undergoing printing impact at said printing position, when the direction of ribbon winding is reversed.

Claim 4

In a ribbon feed and correction device of the type wherein two winding spools alternately wind a printing ribbon mounted therebetween, said ribbon having a ribbon reversing tab at a longitudinal end thereof to operatively engage an operating end of a reversing lever to reverse the direction of rotation of said winding spools when said ribbon is unwound to said longitudinal end, said winding spools rotatably mounted on a ribbon spool rupport plate which is pivotally mounted to a fixed mounting plate, said ribbon spool support plate undergoing a pivotal displacement with respect to said fixed mounting plate when said versing lever reverses the direction of rotation of said winding spools, said ribbon passing over a printing position fixed with respect to said fixed mounting plate, the improvement made to extend the useful liFe of said ribbon, by reducing the duration of printing impact during said reversal of winding spool rotation, comprising: a ratchet wheel rotatably mounted on said fixed mounting plate, to rotate about a first axis, a detent means mounted on said fixed mounting plate, for operatively engaging said ratchet wheel and preventing rotation thereof opposite to a preferred direction; a pawl means mounted on said ribbon spool support plate, for operatively engaging said ratchet wheel and rotatably advancing said ratchet wheel in said preferred direction when said ribbon spool support plate undergoes said pivotal displacement with respect to said fixed mounting plate; a cylindrical hub rigidly mounted on said ratchet wheel with a second cylindrical axis parallel to but displaced from said first axis, to undergo eccentric motion when said ratchet wheel rotates about said first axis; said reversing lever rotatably mounted on said cylindrical hub so that while maintaining substantially the same general orientation with respect to said fixed mounting plate, said reversing lever undergoes a circular oscillatory motion with respect to said fixed mounting plate, induced by the eccentric motion of said cylindrical hub as said ratchet wheel rotates; whereby the distance between said printing position and said operating end of said reversing lever which operatively engages said ribbon reversing tab, changes as said winding spools change their winding direction, thereby changing the portion of the ribbon undergoing printing impact at said printing position, when the direction of ribbon winding is reversed.