A sheet convey apparatus and a printer having such a sheet convey apparatus have rock arms rockable around a rotational center of a driven roller on which an endless belt is supported. Urging roller attaching plates for supporting the urging roller, a transmission shaft, urging roller driving arms and urging cylinders are attached to the rock arms, and the urging cylinders can abut against the corresponding urging roller driving arms. Urging force releasing springs are connected between the urging roller driving arms and the rock arms. When the urging cylinders are extended, the urging roller is urged against the endless belt, and, when the urging cylinders are retracted, the urging force of the urging roller is released. In this way, a sheet urging force is kept constant to eliminate unevenness of the contact between the sheet and the endless belt, and any streak is prevented from being formed on the sheet.
A coupling assembly for a printing system that includes a threaded bolt that engages a threaded bore of a first dovetail nut. The assembly also includes a second dovetail nut with a bore through which a shaft of the bolt passes. Each dovetail nut has two tapered portions located on opposite sides of the bore of the respective nut. When the bolt/dovetail nut combination is assembled, the two dovetail nuts are located a distance apart so that the tapered portions of the two nuts define a pair of slots. To connect sections of the web guide together, each slot engages a flared connector of a respective section.
A printing system that includes a web guide having a preprinting section which guides a substrate into the printing system, and a postprinting section which maintains tension in the substrate as the substrate moves through the printing system. A printing section is positioned between the preprinting section and the postprinting section. The printing section includes a removable platen to provide a gap in the printing section to prevent excess ink which is deposited onto the substrate from accumulating underneath the substrate.
