Tube pump and liquid ejection apparatus

Abstract

A tube pump including a housing, a tube, a rotor, and a pressing member is disclosed. The tube has a section that is arranged in the housing in such a manner as to annularly extend along an inner circumferential surface. The rotor has a cam surface. The pressing member has a main body that selectively presses the tube toward the inner circumferential surface and a shaft that extends from the main body and contacts the cam surface. During rotation of the rotor, the pressing member moves, with the shaft contacting the cam surface, along the inner circumferential surface while pressing the tube. The shaft has a contact part that contacts the cam surface, and is formed in such a manner that the frictional coefficient of the shaft is lower than the frictional coefficient of the main body at least in the contact part.

1 . A tube pump comprising:
 a housing having an inner circumferential surface;   a tube having a section that is arranged in the housing in such a manner as to annularly extend along the inner circumferential surface;   a rotor rotatably arranged in the housing, the rotor having a cam surface; and   a pressing member arranged in the housing, the pressing member having a main body that selectively presses the tube toward the inner circumferential surface and a shaft that extends from the main body and contacts the cam surface, wherein, during rotation of the rotor, the pressing member moves, with the shaft contacting the cam surface, along the inner circumferential surface while pressing the tube,   wherein the shaft has a contact part that contacts the cam surface, and the shaft is formed in such a manner that the frictional coefficient of the shaft is lower than the frictional coefficient of the main body at least in the contact part.   
   
   
       2 . The pump according to  claim 1 , wherein the shaft and the main body are components formed separately from each other, and the main body has an insertion hole into which the shaft is inserted. 
   
   
       3 . The pump according to  claim 2 , wherein the pressing member includes a retaining member for preventing the shaft from coming off the insertion hole. 
   
   
       4 . The pump according to  claim 1 , wherein the contact part is formed of a metal or a synthetic resin having a low friction. 
   
   
       5 . The pump according to  claim 1 , wherein the shaft is rotatable relative to the main body. 
   
   
       6 . A liquid ejection apparatus comprising:
 a liquid ejection head having a nozzle-forming surface in which a nozzle for ejecting liquid is formed;   a cap capable of sealing the nozzle-forming surface; and   a suction device capable of applying suction to the interior of the cap,   wherein the suction device is formed by the tube pump according to  claim 1 .   
   
   
       7 . A tube pump comprising:
 a housing having an inner circumferential surface;   a tube having a section that is arranged in the housing in such a manner as to annularly extend along the inner circumferential surface;   a rotor rotatably arranged in the housing, the rotor having a cam surface; and   a pressing member arranged in the housing, the pressing member having a main body that selectively presses the tube toward the inner circumferential surface and a shaft that extends from the main body and contacts the cam surface, wherein, during rotation of the rotor, the pressing member moves, with the shaft contacting the cam surface, along the inner circumferential surface while pressing the tube,   wherein the main body has an insertion hole into which the shaft is inserted, the shaft contacting the inner surface of the insertion hole and being rotatable relative to the main body, and wherein, at a contacting portions of the shaft and the main body, the frictional coefficient of one of the shaft is lower than the frictional coefficient of the other.   
   
   
       8 . A liquid ejection apparatus comprising:
 a liquid ejection head having a nozzle-forming surface in which a nozzle for ejecting liquid is formed;   a cap capable of sealing the nozzle-forming surface; and   a suction device capable of applying suction to the interior of the cap,   wherein the suction device is formed by the tube pump according to  claim 7 .   
   
   
       9 . A tube pump comprising:
 a housing having an inner circumferential surface;   a tube having a section that is arranged in the housing in such a manner as to annularly extend along the inner circumferential surface;   a rotor rotatably arranged in the housing, the rotor having a cam surface that extends in a circumferential direction of the rotor; and   a pressing member arranged in the housing, the pressing member selectively pressing the tube toward the inner circumferential surface and being slidable on the cam surface between an actuation position and a non-actuation position, wherein, during rotation of the rotor, the pressing member, if at the actuation position, moves along the inner circumferential surface while pressing the tube, thereby producing negative pressure in the tube, and, if at the non-actuation position, moves along the inner circumferential surface while pressing the tube in such a manner that no negative pressure is produced,   wherein the frictional coefficient of the cam surface is partially different.   
   
   
       10 . The pump according to  claim 9 , wherein the cam surface has a contact part, the pressing member contacting the contact part when at the actuation position, and wherein the frictional coefficient of the contact part is lower than the frictional coefficient of the remainder of the cam surface. 
   
   
       11 . The pump according to  claim 10 , wherein the contact part is formed of a material having a lower frictional coefficient than the friction coefficient of the remainder of the cam surface. 
   
   
       12 . The pump according to  claim 10 , wherein the contact part is formed as a component separate from the pressing member and is made of a material having a lower frictional coefficient than the friction coefficient of the remainder of the cam surface. 
   
   
       13 . The pump according to  claim 10 , wherein coating for reducing frictional resistance is applied to the contact part. 
   
   
       14 . A liquid ejection apparatus comprising:
 a liquid ejection head having a nozzle-forming surface in which a nozzle for ejecting liquid is formed;   a cap capable of sealing the nozzle-forming surface; and   a suction device capable of applying suction to the interior of the cap,   wherein the suction device is formed by the tube pump according to  claim 9 .