Printhead-to-platen variable spacing mechanism
View Patent ↗A spacing mechanism is provided to vary the distance between a rotary platen and a pagewidth printhead as a function of the angle of rotation of the platen. The spacing mechanism includes cams fixed at opposing ends of the platen and corresponding cam followers mounted fast with the printhead and positioned to follow the cams. Springs are arranged to bias the cam followers against the cams in use. The platen includes a number of radially located elongate working surfaces each providing a servicing function to the printhead that requires a different platen-to-printhead spacing. The cams are shaped to suitably vary the printhead-to-platen distance between each working surface and the printhead as the working surface is rotated adjacent to the printhead.
1. A printer of a type having a pagewidth printhead including:
an elongate platen arranged to rotate about an axis parallel to said printhead including two or more radially disposed elongate working surfaces to service the printhead;
a spacing mechanism arranged to vary the distance between said platen and the printhead dependent upon an angle of rotation of the platen.
2. A printer according to claim 1 , wherein the spacing mechanism comprises:
cams fixed at opposing ends of said platen;
cam followers fast with the printhead corresponding to the cams; and
a biasing mechanism arranged to bias the cams against the cam followers;
wherein the cams are shaped to vary the distance between the working surfaces and the printhead upon rotation of said platen.
3. A printer according to claim 2 , wherein the biasing mechanism comprises one or more springs.
4. A printer according to claim 2 , including an air valve cam fixed at one end of the platen.
5. A printer according to claim 4 , including an air valve cam follower abutting an operative surface of the air valve cam and arranged to operate an air valve in response to rotation of the air valve cam.
6. A printer according to claim 5 , wherein one of the working surfaces comprises a capping surface and wherein the air valve cam is shaped to operate the air valve cam follower to close the air valve upon rotation of the capping surface to a position adjacent the printhead.
7. A printer according to claim 6 , wherein the air valve cam follower is arranged to move an air valve molding longitudinally in response to rotation of the air valve cam.