Multi-head wide-format thermal plotter

Abstract

A wide-format thermal plotting apparatus includes a single platen roller and a plurality of thermal print heads arranged in first and second diametrically opposed rows on the platen roller, the second row having at least one more print head than the first row. More specifically, the rows are arranged in upper and lower opposed relation so that the first, or lower row supports the force applied by the upper row plus the weight of the platen roller, thereby preventing bowing thereof. A supply of print media is sequentially threaded through the first and second rows of print heads, wrapping around the platen roller so that the second or upper row is the downstream printing row. The print heads are arranged in alternating relation between the rows such that print lines of print heads in alternate rows abut or overlap each other with respect to the width of print media. Each print head is mounted for pressured engagement with the platen roller, the print heads in the second row being adjusted to have a greater engagement pressure than the print heads in the first row. The platen roller is driven so that the print media is sequentially drawn through the first and second rows of print heads. The higher number of print heads in the second, downstream row and the increased engagement pressure thereof ensures that the print media remains in contact with the platen roller during printing.