Abstract: A rigid external case structure for a thermal ink-jet pen cartridge, which includes an ink reservoir within the case. The case includes an external frame structure made of an engineering plastic, and defining an open loop, with opposed open areas defined on each opposed side of the loop. Two opposed thin metal side cover plates are attached to the frame structure to cover the open areas, and provide rigidity to the case structure. As a result, the frame structure is substantially non-compressible in response to forces applied against the side members or against the frame, protecting the ink reservoir and preventing ink drool from the pen printhead.

Abstract: An ink jet printer (30) includes a print head reservoir container (14) having a colorant refill needle (26) extending from the exterior to the interior thereof and a vacuum port (24) therein, and a service station (50) having a valve (52) that controllably connects the refill needle (26) to a colorant supply (56) and controllably connects the vacuum port (24) to a vacuum manifold (60). Colorant is added to the reservoir container (14) by first drawing a vacuum on the interior of the reservoir container (14) with the vacuum manifold (60) connected to the vacuum port (24) and with the refill needle (26) sealed, and then sealing the vacuum port (24), placing the refill needle (26) in communication with the exterior colorant supply (56), and permitting the partial vacuum in the interior of the reservoir container (14) to draw colorant from the colorant supply (56) into the interior of the reservoir container (14).