Tube pump and printer provided with the same

1. A tube pump comprising:

a tube through which fluid is flowed;

a housing member comprising a cylindrical chamber in which the tube is accommodated, the cylindrical chamber including an inner peripheral surface along which the tube is arranged;

a rotator comprising a first shaft and a first portion provided on the first shaft, the first portion including a guide having first and second ends, the first end positioned a first distance from the first shaft, the second end positioned a second distance from the first shaft, the second distance being greater than the first distance;

a roller having a first shank received by the guide, the roller configured to selectively press the tube to deform the tube; and

a contact member having a contact portion in the cylindrical chamber extending outwardly towards the inner peripheral surface at least the first distance and less than the second distance, the contact portion formed by the housing member, the contact portion being configured to selectively contact the roller.

2. The tube pump of claim 1 ,

wherein the guide comprises a curved groove defined by the first portion of the rotator,

wherein the guide includes a guide wall formed in an inside of the curved groove in a radial direction of the cylindrical chamber,

wherein a shape of the guide wall is determined according to

α<sin −1 (μ+cos β),

wherein αis a pressure angle which a direction in which the guide wall presses the first shank forms with a direction in which the first shank moves,

wherein μis a rolling friction between the roller and the tube, and

wherein βis an angle which a direction orthogonal to a diameter direction of the rotator forms with a direction in which a surface of the tube extends.

3. The tube pump of claim 2 , wherein the housing member includes a bottom surface of the cylindrical chamber,

wherein the contact portion is formed by the bottom of the cylindrical chamber.

4. The tube pump of claim 1 , wherein the first portion of the rotator is disc shaped and includes a first side facing an open end of the cylindrical chamber and a second side opposite the first side, and wherein the guide is on the second side of the first portion of the rotator.

5. The tube pump of claim 1 , wherein the roller further includes a roller body and a second shank, the first and second shanks extending axially from the roller body, wherein the second shank is configured to contact the contact portion when the first shank is positioned in the first end of the guide.

6. The tube pump of claim 5 , wherein the second shank is configured to not contact the contact portion when the first shank is positioned in the second end of the guide.

7. The tube pump of claim 1 , wherein the guide is configured to position the first shank in the first end of the guide in response to rotation of the rotator in a first rotation direction, and position the first shank in the second end of the guide in response to rotation of the rotator in a second rotation direction.

8. The tube pump of claim 1 , wherein the roller is configured to revolve in response to rotation of the rotator.

9. A tube pump comprising:

a tube through which fluid is flowed;

a housing member comprising a cylindrical chamber in which the tube is accommodated, the cylindrical chamber including an inner peripheral surface along which the tube is arranged;

a rotator comprising a rotation shaft and a first portion provided on the rotation shaft, the first portion including a guide, the rotator being rotatable in the cylindrical chamber;

a roller received by the guide to be moved between a pressing position and a release position when the rotator is rotated in first and second rotation directions, respectively; and

a contact portion formed by the housing member, wherein the roller contacts the contact portion when the rotator rotates in the first rotation direction to move the roller from the release position to the pressing position, and the roller does not contact the contact portion when the rotator rotates in the second rotation direction.

10. The tube pump of claim 9 , wherein the roller is configured to revolve in first and second directions in response to rotation of the rotator in first and second directions, respectively.

11. The tube pump of claim 10 , wherein the roller includes a first shank received by the guide and a second shank configured to contact the contact portion when the rotator rotates in the first rotation direction.

12. The tube pump of claim 9 , wherein the roller is configured such that when in the pressing positon the roller presses the tube to deform the tube for generating a pressure in the tube, and when in the release position the roller is displaced from the release position and pressure in the tube is not generated.