Printing wheel setting and aligning apparatus

Claim 1

Printing apparatus for printing a line of characters comprising: a plurality of toothed printing wheels having a common axis of rotation, each printing wheel having a set of type characters spaced around its periphery; means defining a printing line, parallel to the said axis and containing a printing position for each printing wheel; a plurality of setting wheels, one for each printing wheel, each setting wheel having a separate different axis of rotation and having teeth engaging in the spaces between the type faces of its printing wheel, the axes of rotation of the setting wheels being parallel to the said axis of the printing wheels and being arranged in an arc around the axis of the printing wheels; a plurality of stepping motors, one for each printing wheel, each stepping motor having a driving shaft and a toothed wheel on the driving shaft, the axis of rotation of the stepping motors being spaced from one another about the axis of the printing wheels and being further than the setting wheel axes from the axis of the printing wheels; a plurality of endless flexible transmission means, one coupling each stepping motor toothed wheel respectively to the corresponding setting wheel, whereby each stepping motor rotates the corresponding printing wheel to bring a selected character into the printing position; an alignment bar having a portion for each printing wheel and being movable to cause each respective portion to engage in a slot in its printing wheel, such engagement of said portion and said slot being possible only if the corresponding printing wheel has a printing character in the printing position; a print control means controlling the printing of a line of characters from the printing wheel; and switching means, responsive to the engagement of all said portions of said alignment bar in their respective printing wheel slots to supply to said print control means a signal indicative of the print wheel alignment.