Importance

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Abstract

A tube pump for an ink jet printer includes a driving wheel that is selectively driven in a forward or reverse direction in accordance with the rotation of a drive source. The driving wheel contains two slots that extend symmetrically and radially from the center of the driving wheel. The pump also includes two rollers that are coupled to the drive wheel via roller shafts respectively extending from a radial center of the rollers into the slots. A pressing piece is also provided that forces the shafts into the radially outermost end of the slots to press a tube of the tube pump when said drive wheel rotates in reverse and forces the shafts into the radially innermost end of the slots to not press the tube when said drive wheel rotates in the forward direction. In an alternative arrangement, the tube pump contains a pump chamber, and a tube having an .alpha.-like-shaped loop portion is inserted into and disposed along the inner wall of the pump chamber. A driving wheel train is provided, rotated around a shaft of the pump chamber, and has a single roller that cooperates with the inner wall of the pump chamber to press the tube. Also, a guide slot is formed in the driving wheel train to transfer the roller between a tube pressurizing state and a tube nonpressurizing state based on the rotation of the driving wheel train.

First Claim