Carriage mechanism for printer

Claim 1

A mechanism for carrying a thermal printer head or the like comprising in combination: a. a frame having a slideably mounted carriage with a printing head thereon adapted to slide from a first side of said frame to the second side of said frame and return, b. said printing head being adapted to print when traversing from said first side to said second side and to not print when being returned from said second side to said first side, c. spring means for biasing said carriage from the first side of the frame to the second side of the frame, d. escapement means for permitting said carriage to move by the action of said spring against said escapement means from the first side of the carriage to the second side of the carriage, said escapement means including a rack lying parallel to the path of travel of said carriage and pivot means on said rack whereby said rack can be rotated from a first position to a second position, e. means for rotating said rack from said first position to said second position, f. a first pawl mounted on said carriage, said pawl having a first tooth adapted to engage said rack when said rack is in the first position, and a second tooth adapted to engage said rack when said rack is in said second position, said rack and pawl means permitting said carriage to move stepwise through its path of travel from the first side of said frame to the second side of said frame as said rack is moved from the first position to said second position, g. power means for returning said carriage from the second side of said frame to the first side of said frame, said power means including a worm extending from one side of said frame to the other and a second pawl on said carriage whereby said second pawl can engage said worm and said worm will move said carriage against said spring, moving said carriage to its opposite limit of travel, h. means for rotating said worm, i. said worm having a cam thereon, said cam having three faces, namely, a low concentric face, a cam lobe and a high concentric face, j. a cam follower riding on said low concentric face while said carriage moves stepwise through its path of travel, and k. means to shift said cam follower to said lobe, whereby said cam follower rises on said lobe to the high concentric face, engaging said second pawl with said worm, whereby the carriage is caused to reverse its path of travel.