US20080056918A1 - Tube pump and liquid ejection apparatus - Google Patents
Tube pump and liquid ejection apparatus Download PDFInfo
- Publication number
- US20080056918A1 US20080056918A1 US11/848,989 US84898907A US2008056918A1 US 20080056918 A1 US20080056918 A1 US 20080056918A1 US 84898907 A US84898907 A US 84898907A US 2008056918 A1 US2008056918 A1 US 2008056918A1
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- United States
- Prior art keywords
- tube
- shaft
- housing
- pressing member
- inner circumferential
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B43/00—Machines, pumps, or pumping installations having flexible working members
- F04B43/12—Machines, pumps, or pumping installations having flexible working members having peristaltic action
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/17—Ink jet characterised by ink handling
- B41J2/1714—Conditioning of the outside of ink supply systems, e.g. inkjet collector cleaning, ink mist removal
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/17—Ink jet characterised by ink handling
- B41J2/18—Ink recirculation systems
- B41J2/185—Ink-collectors; Ink-catchers
Definitions
- the present invention relates to a liquid ejection apparatus such as an inkjet printer and a tube pump used in a liquid ejection apparatus.
- Inkjet printers are widely known as liquid injection apparatuses for injecting liquid from a nozzle formed in a recording head onto target.
- printers since nozzles have openings on a nozzle-forming surface of a recording head (liquid ejection head), ink solvent evaporates from the nozzles. As a result, the viscosity of the ink increases, which may influence the ejection characteristics of the ink.
- Printers are therefore provided with a maintenance mechanism that performs maintenance of a recording head.
- a maintenance mechanism includes a cap for sealing a nozzle-forming surface of the recording head and a suction pump located in a drain passage.
- the maintenance mechanism drives the suction pump while sealing the nozzle-forming surface with the cap, thereby producing negative pressure in the cap. Ink having an increased viscosity is drawn out of the nozzles, and the ink ejection is prevented from deteriorating.
- suction pumps tub pumps that are disclosed, for example, in Japanese Laid-Open Patent Publication No. 2001-301195 and Japanese Laid-Open Patent Publication No. 2002-349452 are used.
- the above publications each disclose a tube pump having a substantially cylindrical housing.
- the housing accommodates an intermediate portion of a flexible tube in the longitudinal direction, a rotor that rotates about the axis of the housing, and a roller (pressing member).
- a roller pressing member
- the tube is accommodated in the housing in such a manner that the intermediate portion in the longitudinal direction wound one turn along the inner circumferential surface of the housing to form a circle.
- different sections of the tube partially overlap.
- An elongated hole that extends along the circumferential direction of the rotor is formed in a side of the rotor.
- the inner wall of the elongated hole defines a cam surface.
- the elongated hole extends in such a manner that the radial distance from the axis of the rotor is gradually reduced from one end in the circumferential direction to the other end.
- the roller has a shaft that extends along the axis, which shaft is slidably inserted in the elongated hole of the rotor.
- the roller is movable relative to the rotor between one end of the elongated hole (actuation position) and the other end (non-actuation position). As the roller moves from the non-actuation position toward the actuation position, the roller moves radially outward in the rotor.
- the shaft of the roller slides toward the actuation position (pressing position) in the elongated hole.
- the roller operates with the inner circumferential surface of the housing. That is, the roller moves along the inner circumferential surface of the housing, while consecutively pressing part of the intermediate portion of the tube.
- portion of the tube that have been released from the pressing of the roller sequentially restore. Accordingly, the interior of a portion of the tube that is upstream of the intermediate portion, which is accommodated in the housing, is decompressed, so that negative pressure is produced in the cap. This draws ink with an increased viscosity from the nozzles.
- the roller shaft moves along the elongated hole, and rotates at the actuation position.
- frictional resistance is generated between the roller shaft and the cam surface.
- the roller shaft at the actuation position, rotates and slides on the cam surface while receiving a reactive force from the pressed tube. Therefore, the frictional resistance is particularly increased when the roller is at the actuation position.
- Such frictional resistance is preferably minimized from the perspective of reducing the friction of the cam surface, reducing the torque required for operating the tube pump, and improving the pump efficiency.
- a tube pump having a housing, a tube, a rotor, and a pressing member.
- the housing has an inner circumferential surface.
- the tube has a section that is arranged in the housing in such a manner as to annularly extend along the inner circumferential surface.
- the rotor is rotatably arranged in the housing, and has a cam surface.
- the pressing member is arranged in the housing.
- 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.
- 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.
- 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.
- a liquid ejection apparatus having a liquid ejection head, a cap, and a suction device.
- the liquid ejection head has a nozzle-forming surface in which a nozzle for ejecting liquid is formed.
- the cap is capable of sealing the nozzle-forming surface.
- the suction device is capable of applying suction to the interior of the cap.
- the suction device is formed by the tube pump according to the first aspect of the present invention.
- a tube pump having a housing, a tube, a rotor, and a pressing member.
- the housing has an inner circumferential surface.
- the tube has a section that is arranged in the housing in such a manner as to annularly extend along the inner circumferential surface.
- the rotor is rotatably arranged in the housing, and has a cam surface.
- the pressing member is arranged in the housing.
- 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 main body has an insertion hole into which the shaft is inserted.
- the shaft contacts the inner surface of the insertion hole and is rotatable relative to the main body.
- the frictional coefficient of one of the shaft is lower than the frictional coefficient of the other.
- a liquid ejection apparatus having a liquid ejection head, a cap, and a suction device.
- the liquid ejection head has a nozzle-forming surface in which a nozzle for ejecting liquid is formed.
- the cap is capable of sealing the nozzle-forming surface.
- the suction device is capable of applying suction to the interior of the cap.
- the suction device is formed by the tube pump according to the third aspect of the present invention.
- a tube pump having a housing, a tube, a rotor, and a pressing member.
- the housing has an inner circumferential surface.
- the tube has a section that is arranged in the housing in such a manner as to annularly extend along the inner circumferential surface.
- the rotor is rotatably arranged in the housing.
- the rotor has a cam surface that extends in a circumferential direction of the rotor.
- the pressing member is arranged in the housing. The pressing member selectively presses the tube toward the inner circumferential surface and is slidable on the cam surface between an actuation position and a non-actuation position.
- 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.
- the frictional coefficient of the cam surface is partially different.
- a liquid ejection apparatus having a liquid ejection head, a cap, and a suction device.
- the liquid ejection head has a nozzle-forming surface in which a nozzle for ejecting liquid is formed.
- the cap is capable of sealing the nozzle-forming surface.
- the suction device is capable of applying suction to the interior of the cap.
- the suction device is formed by the tube pump according to the fifth aspect of the present invention
- FIG. 1 is a perspective view illustrating an inkjet printer according to one embodiment of the present invention
- FIG. 2 is a schematic cross-sectional view showing a part of the printer of FIG. 1 ;
- FIG. 3 is a perspective view illustrating the tube pump of the printer shown in FIG. 1 ;
- FIG. 4 is an exploded perspective view of the tube pump of FIG. 3 ;
- FIG. 5 is a cross-sectional view of the tube pump of FIG. 3 ;
- FIG. 6 is an exploded perspective view illustrating the pump wheel and the pressing member in the tube pump shown in FIG. 3 ;
- FIG. 7 is a side view showing the pressing member of FIG. 6 .
- an inkjet printer 11 which functions as a liquid ejection apparatus, has a frame 12 , which is shaped like a rectangular box.
- a platen 13 is located in a lower portion of the frame 12 .
- the platen 13 extends along the longitudinal direction, or left-and-right direction, of the frame 12 .
- a paper feeding motor 14 is located in a lower back portion of the frame 12 . Based on the driving force of the paper feeding motor 14 , a paper feeding mechanism (not shown) feeds sheets of recording paper P forward from the rear side onto the platen 13 .
- a guide shaft 15 extends in the frame 12 .
- the guide shaft 15 is located above the platen 13 and extends along the longitudinal direction of the platen 13 .
- a carriage 16 is supported by the guide shaft 15 , so that the carriage 16 reciprocates along the axial direction of the guide shaft 15 . That is, the guide shaft 15 is passed through a support hole 16 a that extends through the carriage 16 in the left-and-right direction.
- the guide shaft 15 supports the carriage 16 such that the carriage 16 can reciprocate along the longitudinal direction of the guide shaft 15 .
- a drive pulley 17 a and a driven pulley 17 b are rotatably supported on a back wall of the frame 12 at positions corresponding to opposite ends of the guide shaft 15 .
- An output shaft of a carriage motor 18 is connected to the drive pulley 17 a .
- An endless timing belt 17 which is coupled to the carriage 16 , is wound around the pulleys 17 a , 17 b . The carriage 16 is thus moved in the left-and-right direction through the timing belt 17 while driven by the carriage motor 18 and guided by the guide shaft 15 .
- a recording head 19 or a liquid ejection head, is formed on a bottom surface of the carriage 16 .
- Ink cartridges 20 are detachably mounted on the carriage 16 .
- the ink cartridges 20 supply liquid, which is ink, to the recording head 19 .
- the recording head 19 has piezoelectric elements 21 and nozzles 22 (see FIG. 2 ). When the piezoelectric elements 21 are activated, ink that has been supplied to the recording head 19 is injected onto the paper sheet P on the platen 13 . Printing is thus performed.
- a home position area (non-printing area), which does not correspond to the paper sheet P, is provided near the right end in the frame 12 .
- a maintenance mechanism 23 is located in the home position area. The maintenance mechanism 23 performs maintenance such as cleaning of the recording head 19 when printing is not being performed.
- the maintenance mechanism 23 has cap 24 and a lift device 25 .
- the cap 24 is shaped like a rectangular box with a bottom.
- the lift device 25 lifts and lowers the cap 24 .
- the maintenance mechanism 23 moves the carriage 16 to the home position area, and in this state, lifts the cap 24 with the lift device 25 , thereby sealing a nozzle-forming surface 19 a (the nozzles 22 ) of the recording head 19 with the cap 24 .
- a projection 26 extends downward from the bottom of the cap 24 .
- a drain passage 26 a for draining ink extends through the projection 26 along the up-and-down direction.
- a first end (a proximal end or an upstream end) of a drain tube 27 made of a flexible material is connected to the projection 26 .
- a second end (a distal end or a downstream end) of the drain tube 27 is inserted in a waste ink tank 28 , which shaped like a rectangular parallelepiped.
- a tube pump 29 serving as a suction device, is located in an intermediate portion of the drain tube 27 between the cap 24 and the waste ink tank 28 . The tube pump 29 draws air in the cap 24 from the cap 24 to the waste ink tank 28 .
- the tube pump 29 is activated so that viscous ink is drawn out of the nozzles 22 together with bubbles.
- the ink and bubbles are drained to the waste ink tank 28 through the cap 24 and the drain tube 27 .
- This process is referred to as cleaning.
- a waste ink absorber 30 is accommodated in the waste ink tank 28 .
- the waste ink absorber 30 absorbs and retains ink drained into the waste ink tank 28 .
- the tube pump 29 will now be described.
- the tube pump 29 has a cylindrical housing 31 that is fixed in the frame 12 (see FIG. 1 ).
- the housing 31 has a bottom wall, and a through hole 31 a is formed in the bottom wall to connect the inside and the outside of the housing 31 .
- a pump wheel 32 serving as a rotor is accommodated in the housing 31 .
- the pump wheel 32 is rotatable about an axis of the housing 31 . That is, the pump wheel 32 has a wheel shaft 33 that extends along the axis A and is inserted in the through hole 31 a .
- the pump wheel 32 is rotatable about the wheel shaft 33 in the housing 31 .
- An upstream opening (a first opening) 34 and a downstream opening (a second opening) 35 are formed in the circumferential wall.
- the upstream opening 34 and the downstream opening 35 extend along a tangential direction of an inner circumferential surface 31 b of the housing 31 .
- the upstream opening 34 and the downstream opening 35 are displaced from each other in the direction of the axis A.
- An intermediate portion 36 of the drain tube 27 in the longitudinal direction is accommodated in the housing 31 , so as to be routed to draw a circle along the inner circumferential surface 31 b of the housing 31 .
- the drain tube 27 extends to the outside of the housing 31 through the upstream opening 34 and the downstream opening 35 .
- an upstream section 36 a and a downstream section 36 b in the intermediate portion 36 are partially overlap in the direction of the axis A.
- a section in which the upstream section 36 a and the downstream section 36 b partially overlap is defined as a tube overlapping section B.
- the drain tube 27 is wound one turn in the housing 31 such that the tube overlapping section B is minimized.
- the upstream section 36 a and the downstream section 36 b each form a thin portion 37 that is thinner than the remainder of the intermediate portion 36 .
- the thickness of each thin portion 37 is determined such that the flexibility of the tube overlapping section B is close to the flexibility of the remainder of the intermediate portion 36 in the housing 31 . That is, the thickness of each thin portion 37 is determined such that the flexibility of the drain tube 27 is constant over the entire circumferential direction in the housing 31 .
- runout portions are provided on the inner circumferential surface 31 b of the housing 31 at positions corresponding to the upstream section 36 a and the downstream section 36 b .
- the runout portions can accommodate the upstream section 36 a and the downstream section 36 b .
- an upstream recess 38 and a downstream recess 39 are formed in the inner circumferential surface 31 b of the housing 31 .
- the upstream recess 38 serves as an upstream runout portion that corresponds to the upstream section 36 a .
- the downstream recess 39 serves as a downstream runout portion that corresponds to the downstream section 36 b .
- the upstream recess 38 and the downstream recess 39 are arranged to be adjacent to each other in the circumferential direction of the inner circumferential surface 31 b of the housing 31 .
- the pump wheel 32 has a disk-shaped large plate 40 and a small plate 41 , which has a smaller diameter than that of the large plate 40 .
- the large plate 40 and the small plate 41 are fixed to the wheel shaft 33 with the centers penetrated by the wheel shaft 33 .
- the large plate 40 and the small plate 41 are spaced from each other at a predetermined distance along the axial direction.
- a roller guiding slit 42 extends through the large plate 40 .
- the roller guiding slit 42 is arcuate and bulges radially outward.
- the roller guiding slit 42 has a first end and a second end.
- the roller guiding slit 42 extends in such a manner that the first end is located outside of the second end with respect to the radial direction of the large plate 40 . That is, the roller guiding slit 42 extends so as to gradually approach the axis of the large plate 40 from the first end to the second end.
- a roller guiding recess 43 is formed in a peripheral portion of the small plate 41 .
- the roller guiding recess 43 corresponds to the roller guiding slit 42 of the large plate 40 .
- the inner surface functions as a cam surface C.
- a wall surface of the small plate 41 that defines the roller guiding recess 43 functions as a cam surface C.
- a pressing member 46 is supported by the large plate 40 and the small plate 41 at the axial ends.
- the pressing member 46 includes a main body, which is a roller 44 , and a shaft 45 .
- a first end of the shaft 45 is inserted through the roller guiding slit 42 to be slidable on the cam surface C.
- a second end of the shaft 45 is arranged in the roller guiding recess 43 to be slidable on the cam surface C. That is, the roller 44 moves along the cam surfaces C with the first and second ends of the shaft 45 sliding on the cam surfaces C.
- the roller 44 and the shaft 45 are separate components. That is, the roller 44 has an insertion hole 44 a extending along the axis.
- the shaft 45 which is longer than the roller 44 in the axial direction is fitted in the insertion hole 44 a .
- the ends of the shaft 45 project from both ends of the roller 44 .
- the shaft 45 is slidable on the inner surface of the insertion hole 44 a , so that the roller 44 and the shaft 45 are rotatable relative to each other.
- a material having a lower frictional coefficient than that of the roller 44 is used for forming the shaft 45 .
- a metal or a synthetic resin having a low friction is used.
- a synthetic resin having a low friction includes resins of a sliding grade, such as polyacetal (POM) and polystyrene (PS).
- the material for forming the shaft 45 polyacetal of a sliding grade is used. Accordingly, the frictional coefficient of the shaft 45 is lower than that of the roller 44 .
- Retaining members, or retaining pins 47 for preventing the shaft 45 from coming off are provided at both ends of the roller 44 .
- the retaining pins 47 prevent the shaft 45 from coming off the insertion hole 44 a of the roller 44 .
- the retaining pins 47 are configured no to prevent relative rotation between the roller 44 and the shaft 45 .
- the pressing member 46 is moved to the first end of the roller guiding slit 42 . That is, the pressing member 46 is located at a pressing position, which is a radially outer position in the pump wheel 32 , or an actuation position. At the actuation position, the pressing member 46 moves from a upstream side to a downstream side along the longitudinal direction of the drain tube 27 as the roller 44 rotates, while pressing and squeezing the intermediate portion 36 of the drain tube 27 .
- the pressing member 46 is moved to the second end of the roller guiding slit 42 . That is, the pressing member 46 is located at a non-pressing position, which is a radially inner position in the pump wheel 32 , or a non-actuation position. At the non-actuation position, the pressing member 46 contacts the intermediate portion 36 of the drain tube 27 with a pressing force that is smaller compared to that in the case where the pressing member 46 is at the actuation position, and does not squeeze the drain tube 27 . The decompressed state in the drain tube 27 is eliminated.
- the shaft 45 of the pressing member 46 contacts contact parts N.
- the contact parts N are formed of a material having a lower frictional coefficient than the remainder of the pump wheel 32 .
- PTFE polytetrafluoroethylene
- the nozzles 22 (the nozzle-forming surface 19 a ) of the recording head 19 are sealed by the cap 24 .
- the pump motor (not shown) is activated and the pump wheel 32 is rotated in the actuation direction. Accordingly, the roller 44 is moved while rotating about the shaft 45 , while squeezing the intermediate portion 36 of the drain tube 27 from the upstream side to the downstream side. At this time, both ends of the shaft 45 slide and rotate on the contact parts N on the cam surfaces C of the pump wheel 32 , while the intermediate portion of the shaft 45 slides and rotate on the inner surface of the insertion hole 44 a.
- the contact parts N are formed of polytetrafluoroethylene, which is a low friction material, and the shaft 45 is formed of polyacetal of a sliding grade. Therefore, the frictional resistance between the shaft 45 and the cam surfaces C and the frictional resistance between the shaft 45 and the roller 44 are both reduced.
- the roller 44 presses the tube overlapping section B the upstream section 36 a and the downstream section 36 b of the drain tube 27 in the tube overlapping section B are moved to the upstream recess 38 and the downstream recess 39 , respectively, so as to escape the pressing by the roller 44 at different timing.
- the thin portion 37 of the tube overlapping section B causes the flexibility of the tube overlapping section B to be close to the flexibility of the intermediate portion 36 except for the tube overlapping section B. Therefore, the fluctuation of torque when the intermediate portion 36 of the drain tube 27 is pressed by the roller 44 is suppressed.
- the present embodiment provides the following advantages.
- the shaft 45 is made of polyacetal of a sliding grade having lower frictional coefficient than that of the roller 44 . Therefore, the frictional resistance between the shaft 45 and the cam surfaces C is lowered. This reduces the force required for rotating the pump wheel 32 when actuating the pump. Thus, the pump torque is reduced. Accordingly, the size of the pump motor (not shown) for driving the pump wheel 32 can be reduced, and the pump efficiency of the tube the pump 29 is improved. As a result, in the cleaning of the recording head 19 , the interior of the cap 24 is efficiently and reliably vacuumed by the tube the pump 29 .
- the pressing member 46 is structured such that the shaft 45 and the roller 44 are rotatable relative to each other.
- the frictional resistance between the shaft 45 and the roller 44 is lower than the frictional resistance between the shaft 45 and the cam surfaces C, so that, during the activation of the pump, the roller 44 is mainly rotated relative to the shaft 45 . Since this suppresses the friction between the shaft 45 and the cam surfaces C, the wear of the shaft 45 and the cam surfaces C is suppressed.
- the contact sections N are formed of polytetrafluoroethylene, which has a lower frictional coefficient than that of the remainder of the cam surfaces C.
- the pressing of the tube overlapping section B by the pressing member 46 corresponds to simultaneously pressing of two sections of the drain tubes 27 by the pressing member 46 .
- the tube overlapping section B is easily flexed. Therefore, the load required for squeezing the tube overlapping section B with the pressing member 46 is reduced by a simple structure that only has the thin portion 37 . Thus, the pump torque is reduced and the pump efficiency is improved.
- the flexibility of the tube overlapping section B is made close to the flexibility of portions other than the tube overlapping section B. That is, the load required for squeezing the tube overlapping section B with the pressing member 46 is made close to the load required for squeezing sections of the intermediate portion 36 other than the tube overlapping section B.
- the load required for squeezing the intermediate portion 36 is equalized over the entire length of the intermediate portion 36 in the housing 31 . Therefore, fluctuation of the pump torque is suppressed. This allows the tube the pump 29 to operate in a stable manner.
- the upstream recess 38 and the downstream recess 39 are formed in the housing to correspond to the upstream section 36 a and the downstream section 36 b , which form the tube overlapping section B, respectively.
- the upstream section 36 a and the downstream section 36 b moved to the corresponding recesses 38 , 39 , respectively, so as to escape the pressing. Therefore, the load required for squeezing the tube overlapping section B with the pressing member 46 is effectively reduced. This reduces the pump torque and improves the pump efficiency.
- the intermediate portion 36 of the drain tube 27 can be routed in the housing 31 to minimize the tube overlapping section B. Therefore, when the pump is used, the load for squeezing the intermediate portion 36 of the drain tube 27 with the pressing member 46 is made equal to a load required for squeezing a single drain tube 27 along the entire circumference of the housing 31 , while substantially eliminating the amount of leak. Thus, the pump torque is reduced and the pump efficiency is improved.
- the present invention is not limited to the above described embodiment, but may be embodied as follows, for example.
- the upstream section 36 a and the downstream section 36 b of the tube overlapping section B may be made of a material having a lower rigidity than that of sections of the intermediate portion 36 other than the tube overlapping section B, thereby increasing the flexibility of the tube overlapping section B. This reliably reduces the load required for squeezing the tube overlapping section B with the pressing member 46 .
- the frictional coefficient on the cam surfaces C of the pump wheel 32 may be partially changed in accordance with the configuration of the tube the pump 29 . This allows the pressing member 46 to press the drain tube 27 in a favorable manner, and to smoothly move between the pressing position and the non-pressing position. As a result, the pump torque is reduced and the pump efficiency is improved.
- the contact parts N in the cam surfaces C may be formed as components separate from the large plate 40 , and made of a low friction material such as polytetrafluoroethylene and polyacetal or polystyrene of a sliding grade.
- the low frictional resistance members are molded products that are press fitted to the large plate 40 . Accordingly, the sliding resistance between the shaft 45 and the contact parts N when the pressing member 46 presses the intermediate portion 36 of the drain tube 27 is reliably reduced by a simple structure.
- Low friction coating such as polytetrafluoroethylene or grease for reducing frictional resistance may be applied to the contact parts N of the cam surfaces C. Accordingly, the sliding resistance between the shaft 45 and the contact parts N when the pressing member 46 presses the intermediate portion 36 of the drain tube 27 is easily and reliably reduced.
- the contact parts N on the cam surfaces C may be subject to surface treatment such as polishing, thereby reducing the frictional coefficient of the contact parts N.
- the retaining pins 47 may be replaced by seal rings functioning as retaining members.
- the frictional coefficient of one of the sliding section of the shaft 45 and the sliding section of the roller 44 may be set lower than the frictional coefficient of the other. Since this reduces the frictional resistance of the shaft 45 and the roller 44 , only the roller 44 is rotated without causing the shaft 45 to rotate when the pump wheel 32 is rotated during the activation of the pump. Therefore, the load applied to the cam surfaces C from the shaft 45 is reduced, which reduces the wear of the cam surfaces C caused by the shaft 45 . Further, the frictional resistance between the shaft 45 and the roller 44 . This reduces the force required for rotating the pump wheel 32 when actuating the pump. Thus, the pump torque is reduced and the pump efficiency is improved.
- the shaft 45 may be press fitted to the insertion hole 44 a of the roller 44 so that the roller 44 and the shaft 45 rotate integrally.
- the shaft 45 of the pressing member 46 may be made of a low friction material such as polytetrafluoroethylene.
- Only parts of the shaft 45 of the pressing member 46 that slide on the cam surfaces C, that is, only both end portions of the shaft 45 may be formed of a low friction material such as polytetrafluoroethylene, metal, and polyacetal or polystyrene of a sliding grade.
- the roller 44 and the shaft 45 may be formed as an integral body.
- the upstream recess 38 and the downstream recess 39 do not need to be arranged to be adjacent to each other in the circumferential direction of the inner circumferential surface 31 b of the housing 31 .
- Either one of the upstream recess 38 and the downstream recess 39 may be omitted.
- the pressing member 46 may include a sliding member that slides on the intermediate portion 36 of the drain tube 27 , while pressing the intermediate portion 36 .
- the liquid ejection apparatus which is equipped with the tube pump 29 , is embodied as the inkjet printer 11 .
- the present invention may be embodied as a liquid ejection apparatus used for manufacturing color filters for liquid crystal displays or pixels of organic EL displays.
- the tube pump 29 may be mounted on apparatus other than liquid ejection apparatuses.
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Ink Jet (AREA)
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.
Description
- This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2006-236909, filed on Aug. 31, 2006 and No. 2006-236911, filed on Aug. 31, 2006, the entire content of which is incorporated herein by reference.
- 1. Technical Field
- The present invention relates to a liquid ejection apparatus such as an inkjet printer and a tube pump used in a liquid ejection apparatus.
- 2. Related Art
- Inkjet printers (hereinafter referred to as printers) are widely known as liquid injection apparatuses for injecting liquid from a nozzle formed in a recording head onto target. In a printer, since nozzles have openings on a nozzle-forming surface of a recording head (liquid ejection head), ink solvent evaporates from the nozzles. As a result, the viscosity of the ink increases, which may influence the ejection characteristics of the ink. Printers are therefore provided with a maintenance mechanism that performs maintenance of a recording head.
- A maintenance mechanism includes a cap for sealing a nozzle-forming surface of the recording head and a suction pump located in a drain passage. The maintenance mechanism drives the suction pump while sealing the nozzle-forming surface with the cap, thereby producing negative pressure in the cap. Ink having an increased viscosity is drawn out of the nozzles, and the ink ejection is prevented from deteriorating. As such suction pumps, tub pumps that are disclosed, for example, in Japanese Laid-Open Patent Publication No. 2001-301195 and Japanese Laid-Open Patent Publication No. 2002-349452 are used.
- The above publications each disclose a tube pump having a substantially cylindrical housing. The housing accommodates an intermediate portion of a flexible tube in the longitudinal direction, a rotor that rotates about the axis of the housing, and a roller (pressing member). When the rotor rotates in one direction, the roller moves along the inner circumferential surface of the housing while pressing the tube.
- The tube is accommodated in the housing in such a manner that the intermediate portion in the longitudinal direction wound one turn along the inner circumferential surface of the housing to form a circle. Thus, in the housing, different sections of the tube partially overlap. An elongated hole that extends along the circumferential direction of the rotor is formed in a side of the rotor. The inner wall of the elongated hole defines a cam surface. The elongated hole extends in such a manner that the radial distance from the axis of the rotor is gradually reduced from one end in the circumferential direction to the other end. The roller has a shaft that extends along the axis, which shaft is slidably inserted in the elongated hole of the rotor. The roller is movable relative to the rotor between one end of the elongated hole (actuation position) and the other end (non-actuation position). As the roller moves from the non-actuation position toward the actuation position, the roller moves radially outward in the rotor.
- When the rotor rotates in an actuation direction, which is one of the circumferential directions, the shaft of the roller slides toward the actuation position (pressing position) in the elongated hole. At the actuation position, the roller operates with the inner circumferential surface of the housing. That is, the roller moves along the inner circumferential surface of the housing, while consecutively pressing part of the intermediate portion of the tube. As the roller moves, portion of the tube that have been released from the pressing of the roller sequentially restore. Accordingly, the interior of a portion of the tube that is upstream of the intermediate portion, which is accommodated in the housing, is decompressed, so that negative pressure is produced in the cap. This draws ink with an increased viscosity from the nozzles.
- When the tube pump is operating, the roller shaft moves along the elongated hole, and rotates at the actuation position. In these cases, frictional resistance is generated between the roller shaft and the cam surface. Particularly, when tube pump is performing suction, the roller shaft, at the actuation position, rotates and slides on the cam surface while receiving a reactive force from the pressed tube. Therefore, the frictional resistance is particularly increased when the roller is at the actuation position. Such frictional resistance is preferably minimized from the perspective of reducing the friction of the cam surface, reducing the torque required for operating the tube pump, and improving the pump efficiency.
- However, the tube pumps disclosed in the above publications take no countermeasures to reduce the frictional resistance between a roller shaft and a cam surface.
- Accordingly, it is an objective of the present invention to provide a tube pump and a liquid ejection apparatus that reduce the torque required for operation and improves the pump efficiency.
- To achieve the foregoing objective and in accordance with a first aspect of the present invention a tube pump having a housing, a tube, a rotor, and a pressing member is provided. The housing has an inner circumferential surface. The tube has a section that is arranged in the housing in such a manner as to annularly extend along the inner circumferential surface. The rotor is rotatably arranged in the housing, and has a cam surface. The pressing member is arranged in the housing. 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. 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.
- In accordance with a second aspect of the present invention, a liquid ejection apparatus having a liquid ejection head, a cap, and a suction device is provided. The liquid ejection head has a nozzle-forming surface in which a nozzle for ejecting liquid is formed. The cap is capable of sealing the nozzle-forming surface. The suction device is capable of applying suction to the interior of the cap. The suction device is formed by the tube pump according to the first aspect of the present invention.
- In accordance with a third aspect of the present invention, a tube pump having a housing, a tube, a rotor, and a pressing member is provided. The housing has an inner circumferential surface. The tube has a section that is arranged in the housing in such a manner as to annularly extend along the inner circumferential surface. The rotor is rotatably arranged in the housing, and has a cam surface. The pressing member is arranged in the housing. 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 main body has an insertion hole into which the shaft is inserted. The shaft contacts the inner surface of the insertion hole and is rotatable relative to the main body. 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.
- In accordance with a fourth aspect of the present invention, a liquid ejection apparatus having a liquid ejection head, a cap, and a suction device is provided. The liquid ejection head has a nozzle-forming surface in which a nozzle for ejecting liquid is formed. The cap is capable of sealing the nozzle-forming surface. The suction device is capable of applying suction to the interior of the cap. The suction device is formed by the tube pump according to the third aspect of the present invention.
- In accordance with a fifth aspect of the present invention, a tube pump having a housing, a tube, a rotor, and a pressing member is provided. The housing has an inner circumferential surface. The tube has a section that is arranged in the housing in such a manner as to annularly extend along the inner circumferential surface. The rotor is rotatably arranged in the housing. The rotor has a cam surface that extends in a circumferential direction of the rotor. The pressing member is arranged in the housing. The pressing member selectively presses the tube toward the inner circumferential surface and is slidable on the cam surface between an actuation position and a non-actuation position. 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. The frictional coefficient of the cam surface is partially different.
- In accordance with a sixth aspect of the present invention, a liquid ejection apparatus having a liquid ejection head, a cap, and a suction device is provided. The liquid ejection head has a nozzle-forming surface in which a nozzle for ejecting liquid is formed. The cap is capable of sealing the nozzle-forming surface. The suction device is capable of applying suction to the interior of the cap. The suction device is formed by the tube pump according to the fifth aspect of the present invention
- Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.
- The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:
-
FIG. 1 is a perspective view illustrating an inkjet printer according to one embodiment of the present invention; -
FIG. 2 is a schematic cross-sectional view showing a part of the printer ofFIG. 1 ; -
FIG. 3 is a perspective view illustrating the tube pump of the printer shown inFIG. 1 ; -
FIG. 4 is an exploded perspective view of the tube pump ofFIG. 3 ; -
FIG. 5 is a cross-sectional view of the tube pump ofFIG. 3 ; -
FIG. 6 is an exploded perspective view illustrating the pump wheel and the pressing member in the tube pump shown inFIG. 3 ; and -
FIG. 7 is a side view showing the pressing member ofFIG. 6 . - One embodiment of the present invention will now be described with reference to the drawings. Unless otherwise specified, a front-and-back direction, an up-and-down direction, and a left-and-right direction each agree with an arrow in all the drawings.
- As shown in
FIG. 1 , aninkjet printer 11, which functions as a liquid ejection apparatus, has aframe 12, which is shaped like a rectangular box. Aplaten 13 is located in a lower portion of theframe 12. Theplaten 13 extends along the longitudinal direction, or left-and-right direction, of theframe 12. Apaper feeding motor 14 is located in a lower back portion of theframe 12. Based on the driving force of thepaper feeding motor 14, a paper feeding mechanism (not shown) feeds sheets of recording paper P forward from the rear side onto theplaten 13. - A guide shaft 15 extends in the
frame 12. The guide shaft 15 is located above theplaten 13 and extends along the longitudinal direction of theplaten 13. Acarriage 16 is supported by the guide shaft 15, so that thecarriage 16 reciprocates along the axial direction of the guide shaft 15. That is, the guide shaft 15 is passed through asupport hole 16 a that extends through thecarriage 16 in the left-and-right direction. The guide shaft 15 supports thecarriage 16 such that thecarriage 16 can reciprocate along the longitudinal direction of the guide shaft 15. - A
drive pulley 17 a and a drivenpulley 17 b are rotatably supported on a back wall of theframe 12 at positions corresponding to opposite ends of the guide shaft 15. An output shaft of acarriage motor 18 is connected to the drivepulley 17 a. Anendless timing belt 17, which is coupled to thecarriage 16, is wound around thepulleys carriage 16 is thus moved in the left-and-right direction through thetiming belt 17 while driven by thecarriage motor 18 and guided by the guide shaft 15. - A
recording head 19, or a liquid ejection head, is formed on a bottom surface of thecarriage 16.Ink cartridges 20 are detachably mounted on thecarriage 16. Theink cartridges 20 supply liquid, which is ink, to therecording head 19. Therecording head 19 haspiezoelectric elements 21 and nozzles 22 (seeFIG. 2 ). When thepiezoelectric elements 21 are activated, ink that has been supplied to therecording head 19 is injected onto the paper sheet P on theplaten 13. Printing is thus performed. - A home position area (non-printing area), which does not correspond to the paper sheet P, is provided near the right end in the
frame 12. Amaintenance mechanism 23 is located in the home position area. Themaintenance mechanism 23 performs maintenance such as cleaning of therecording head 19 when printing is not being performed. - Next, the
maintenance mechanism 23 will be described. - As shown in
FIG. 2 , themaintenance mechanism 23 hascap 24 and alift device 25. Thecap 24 is shaped like a rectangular box with a bottom. Thelift device 25 lifts and lowers thecap 24. Themaintenance mechanism 23 moves thecarriage 16 to the home position area, and in this state, lifts thecap 24 with thelift device 25, thereby sealing a nozzle-formingsurface 19 a (the nozzles 22) of therecording head 19 with thecap 24. Aprojection 26 extends downward from the bottom of thecap 24. Adrain passage 26 a for draining ink extends through theprojection 26 along the up-and-down direction. - A first end (a proximal end or an upstream end) of a
drain tube 27 made of a flexible material is connected to theprojection 26. A second end (a distal end or a downstream end) of thedrain tube 27 is inserted in awaste ink tank 28, which shaped like a rectangular parallelepiped. Atube pump 29, serving as a suction device, is located in an intermediate portion of thedrain tube 27 between thecap 24 and thewaste ink tank 28. Thetube pump 29 draws air in thecap 24 from thecap 24 to thewaste ink tank 28. - With the nozzle-forming
surface 19 a being sealed with thecap 24, thetube pump 29 is activated so that viscous ink is drawn out of thenozzles 22 together with bubbles. The ink and bubbles are drained to thewaste ink tank 28 through thecap 24 and thedrain tube 27. This process is referred to as cleaning. Awaste ink absorber 30 is accommodated in thewaste ink tank 28. Thewaste ink absorber 30 absorbs and retains ink drained into thewaste ink tank 28. - The
tube pump 29 will now be described. - As shown in
FIGS. 3 and 4 , thetube pump 29 has acylindrical housing 31 that is fixed in the frame 12 (seeFIG. 1 ). Thehousing 31 has a bottom wall, and a throughhole 31 a is formed in the bottom wall to connect the inside and the outside of thehousing 31. Apump wheel 32 serving as a rotor is accommodated in thehousing 31. Thepump wheel 32 is rotatable about an axis of thehousing 31. That is, thepump wheel 32 has awheel shaft 33 that extends along the axis A and is inserted in the throughhole 31 a. Thepump wheel 32 is rotatable about thewheel shaft 33 in thehousing 31. - An upstream opening (a first opening) 34 and a downstream opening (a second opening) 35 are formed in the circumferential wall. When viewed from above, the
upstream opening 34 and thedownstream opening 35 extend along a tangential direction of an innercircumferential surface 31 b of thehousing 31. Theupstream opening 34 and thedownstream opening 35 are displaced from each other in the direction of the axis A. Anintermediate portion 36 of thedrain tube 27 in the longitudinal direction is accommodated in thehousing 31, so as to be routed to draw a circle along the innercircumferential surface 31 b of thehousing 31. Thedrain tube 27 extends to the outside of thehousing 31 through theupstream opening 34 and thedownstream opening 35. - In the
housing 31, anupstream section 36 a and adownstream section 36 b in theintermediate portion 36 are partially overlap in the direction of the axis A. A section in which theupstream section 36 a and thedownstream section 36 b partially overlap is defined as a tube overlapping section B. In the present embodiment, thedrain tube 27 is wound one turn in thehousing 31 such that the tube overlapping section B is minimized. - In the tube overlapping section B, the
upstream section 36 a and thedownstream section 36 b each form athin portion 37 that is thinner than the remainder of theintermediate portion 36. The thickness of eachthin portion 37 is determined such that the flexibility of the tube overlapping section B is close to the flexibility of the remainder of theintermediate portion 36 in thehousing 31. That is, the thickness of eachthin portion 37 is determined such that the flexibility of thedrain tube 27 is constant over the entire circumferential direction in thehousing 31. - As shown in
FIG. 5 , runout portions are provided on the innercircumferential surface 31 b of thehousing 31 at positions corresponding to theupstream section 36 a and thedownstream section 36 b. The runout portions can accommodate theupstream section 36 a and thedownstream section 36 b. Specifically, anupstream recess 38 and adownstream recess 39 are formed in the innercircumferential surface 31 b of thehousing 31. Theupstream recess 38 serves as an upstream runout portion that corresponds to theupstream section 36 a. Thedownstream recess 39 serves as a downstream runout portion that corresponds to thedownstream section 36 b. When viewed from above, theupstream recess 38 and thedownstream recess 39 are arranged to be adjacent to each other in the circumferential direction of the innercircumferential surface 31 b of thehousing 31. - As shown in
FIG. 6 , thepump wheel 32 has a disk-shapedlarge plate 40 and asmall plate 41, which has a smaller diameter than that of thelarge plate 40. Thelarge plate 40 and thesmall plate 41 are fixed to thewheel shaft 33 with the centers penetrated by thewheel shaft 33. Thelarge plate 40 and thesmall plate 41 are spaced from each other at a predetermined distance along the axial direction. A roller guiding slit 42 extends through thelarge plate 40. The roller guiding slit 42 is arcuate and bulges radially outward. The roller guiding slit 42 has a first end and a second end. The roller guiding slit 42 extends in such a manner that the first end is located outside of the second end with respect to the radial direction of thelarge plate 40. That is, the roller guiding slit 42 extends so as to gradually approach the axis of thelarge plate 40 from the first end to the second end. - A
roller guiding recess 43 is formed in a peripheral portion of thesmall plate 41. Theroller guiding recess 43 corresponds to the roller guiding slit 42 of thelarge plate 40. Among the wall surfaces of thelarge plate 40 that define the roller guiding slit 42, the inner surface functions as a cam surface C. Also, a wall surface of thesmall plate 41 that defines theroller guiding recess 43 functions as a cam surface C. - A pressing
member 46 is supported by thelarge plate 40 and thesmall plate 41 at the axial ends. The pressingmember 46 includes a main body, which is aroller 44, and ashaft 45. A first end of theshaft 45 is inserted through the roller guiding slit 42 to be slidable on the cam surface C. A second end of theshaft 45 is arranged in theroller guiding recess 43 to be slidable on the cam surface C. That is, theroller 44 moves along the cam surfaces C with the first and second ends of theshaft 45 sliding on the cam surfaces C. - As shown in
FIG. 7 , theroller 44 and theshaft 45 are separate components. That is, theroller 44 has aninsertion hole 44 a extending along the axis. Theshaft 45, which is longer than theroller 44 in the axial direction is fitted in theinsertion hole 44 a. Thus, the ends of theshaft 45 project from both ends of theroller 44. Theshaft 45 is slidable on the inner surface of theinsertion hole 44 a, so that theroller 44 and theshaft 45 are rotatable relative to each other. - A material having a lower frictional coefficient than that of the
roller 44 is used for forming theshaft 45. Specifically, a metal or a synthetic resin having a low friction is used. A synthetic resin having a low friction includes resins of a sliding grade, such as polyacetal (POM) and polystyrene (PS). In the present embodiment, the material for forming theshaft 45, polyacetal of a sliding grade is used. Accordingly, the frictional coefficient of theshaft 45 is lower than that of theroller 44. - Retaining members, or retaining
pins 47, for preventing theshaft 45 from coming off are provided at both ends of theroller 44. The retaining pins 47 prevent theshaft 45 from coming off theinsertion hole 44 a of theroller 44. The retaining pins 47 are configured no to prevent relative rotation between theroller 44 and theshaft 45. - When a pump motor (not shown) is activated and the
pump wheel 32 is rotated in an actuation direction of thepump 29, that is, in a direction causing tube thepump 29 to perform suction (a direction indicated by an arrow inFIG. 5 ), the pressingmember 46 is moved to the first end of the roller guiding slit 42. That is, the pressingmember 46 is located at a pressing position, which is a radially outer position in thepump wheel 32, or an actuation position. At the actuation position, the pressingmember 46 moves from a upstream side to a downstream side along the longitudinal direction of thedrain tube 27 as theroller 44 rotates, while pressing and squeezing theintermediate portion 36 of thedrain tube 27. - As the pressing
member 46 moves, a section of thedrain tube 27 that is upstream of tube thepump 29 is decompressed. Air and ink in thecap 24, which seals the nozzle-formingsurface 19 a, are gradually drained to thewaste ink tank 28 by the rotation of thepump wheel 32 in the actuation direction, which produces negative pressure in thecap 24. - In contrast, when the
pump wheel 32 is rotated in a direction opposite to the actuation direction (a direction opposite to the direction of the arrow inFIG. 5 ), the pressingmember 46 is moved to the second end of the roller guiding slit 42. That is, the pressingmember 46 is located at a non-pressing position, which is a radially inner position in thepump wheel 32, or a non-actuation position. At the non-actuation position, the pressingmember 46 contacts theintermediate portion 36 of thedrain tube 27 with a pressing force that is smaller compared to that in the case where the pressingmember 46 is at the actuation position, and does not squeeze thedrain tube 27. The decompressed state in thedrain tube 27 is eliminated. - As shown in
FIG. 6 , when the pressingmember 46 is moved to the first end of the roller guiding slit 42 on the cam surface of thepump wheel 32, theshaft 45 of the pressingmember 46 contacts contact parts N. The contact parts N are formed of a material having a lower frictional coefficient than the remainder of thepump wheel 32. In the present embodiment, polytetrafluoroethylene (PTFE) is used as the low friction material. - The operation of the
tube pump 29 will now be described. - When performing the cleaning of the
recording head 19, the nozzles 22 (the nozzle-formingsurface 19 a) of therecording head 19 are sealed by thecap 24. In this state, the pump motor (not shown) is activated and thepump wheel 32 is rotated in the actuation direction. Accordingly, theroller 44 is moved while rotating about theshaft 45, while squeezing theintermediate portion 36 of thedrain tube 27 from the upstream side to the downstream side. At this time, both ends of theshaft 45 slide and rotate on the contact parts N on the cam surfaces C of thepump wheel 32, while the intermediate portion of theshaft 45 slides and rotate on the inner surface of theinsertion hole 44 a. - In the present embodiment, the contact parts N are formed of polytetrafluoroethylene, which is a low friction material, and the
shaft 45 is formed of polyacetal of a sliding grade. Therefore, the frictional resistance between theshaft 45 and the cam surfaces C and the frictional resistance between theshaft 45 and theroller 44 are both reduced. - When the
roller 44 presses the tube overlapping section B, theupstream section 36 a and thedownstream section 36 b of thedrain tube 27 in the tube overlapping section B are moved to theupstream recess 38 and thedownstream recess 39, respectively, so as to escape the pressing by theroller 44 at different timing. In addition, thethin portion 37 of the tube overlapping section B causes the flexibility of the tube overlapping section B to be close to the flexibility of theintermediate portion 36 except for the tube overlapping section B. Therefore, the fluctuation of torque when theintermediate portion 36 of thedrain tube 27 is pressed by theroller 44 is suppressed. - When the
roller 44 is moved on theintermediate portion 36 of thedrain tube 27, while squeezing the upstream side to the downstream side of theintermediate portion 36, the interior of thedrain tube 27 that is upstream of thetube pump 29 is decompressed, so that a negative pressure is produced in thecap 24. On the basis of the negative pressure, air and ink in thenozzles 22 and thecap 24 are drawn and drained to thewaste ink tank 28 through thedrain tube 27. Accordingly, the cleaning of therecording head 19 is completed. - The present embodiment provides the following advantages.
- (1) In the pressing
member 46, theshaft 45 is made of polyacetal of a sliding grade having lower frictional coefficient than that of theroller 44. Therefore, the frictional resistance between theshaft 45 and the cam surfaces C is lowered. This reduces the force required for rotating thepump wheel 32 when actuating the pump. Thus, the pump torque is reduced. Accordingly, the size of the pump motor (not shown) for driving thepump wheel 32 can be reduced, and the pump efficiency of the tube thepump 29 is improved. As a result, in the cleaning of therecording head 19, the interior of thecap 24 is efficiently and reliably vacuumed by the tube thepump 29. - (2) Since the
shaft 45 and theroller 44 of the pressingmember 46 are components formed separately from each other, the materials for theshaft 45 and theroller 44 are easily altered in accordance with the configuration of the tube thepump 29. - (3) The pressing
member 46 is structured such that theshaft 45 and theroller 44 are rotatable relative to each other. The frictional resistance between theshaft 45 and theroller 44 is lower than the frictional resistance between theshaft 45 and the cam surfaces C, so that, during the activation of the pump, theroller 44 is mainly rotated relative to theshaft 45. Since this suppresses the friction between theshaft 45 and the cam surfaces C, the wear of theshaft 45 and the cam surfaces C is suppressed. - (4) The retaining pins 47 for preventing the
shaft 45 from coming off theinsertion hole 44 a of theroller 44 are attached to theshaft 45 of the pressingmember 46. Therefore, the positional relation between theshaft 45 and theroller 44 is maintained. - (5) On the cam surfaces C of the
pump wheel 32, the contact sections N are formed of polytetrafluoroethylene, which has a lower frictional coefficient than that of the remainder of the cam surfaces C. Thus, when the pressingmember 46 presses theintermediate portion 36 of thedrain tube 27, the sliding resistance between theshaft 45 and the cam surface C is reduced. Since this reduces the load during the actuation of tube thepump 29, the pump torque is reduced and the pump efficiency is improved. - (6) The pressing of the tube overlapping section B by the pressing
member 46 corresponds to simultaneously pressing of two sections of thedrain tubes 27 by the pressingmember 46. In this respect, since the present embodiment provides thethin portion 37 in the tube overlapping section B, the tube overlapping section B is easily flexed. Therefore, the load required for squeezing the tube overlapping section B with the pressingmember 46 is reduced by a simple structure that only has thethin portion 37. Thus, the pump torque is reduced and the pump efficiency is improved. - (7) The flexibility of the tube overlapping section B is made close to the flexibility of portions other than the tube overlapping section B. That is, the load required for squeezing the tube overlapping section B with the pressing
member 46 is made close to the load required for squeezing sections of theintermediate portion 36 other than the tube overlapping section B. Thus, the load required for squeezing theintermediate portion 36 is equalized over the entire length of theintermediate portion 36 in thehousing 31. Therefore, fluctuation of the pump torque is suppressed. This allows the tube thepump 29 to operate in a stable manner. - (8) The
upstream recess 38 and thedownstream recess 39 are formed in the housing to correspond to theupstream section 36 a and thedownstream section 36 b, which form the tube overlapping section B, respectively. When the tube overlapping section B is pressed by the pressingmember 46, theupstream section 36 a and thedownstream section 36 b moved to the corresponding recesses 38, 39, respectively, so as to escape the pressing. Therefore, the load required for squeezing the tube overlapping section B with the pressingmember 46 is effectively reduced. This reduces the pump torque and improves the pump efficiency. - (9) Since the
upstream recess 38 and thedownstream recess 39 are arranged in thehousing 31 to be adjacent to each other along the circumferential direction of the innercircumferential surface 31 b of thehousing 31, theintermediate portion 36 of thedrain tube 27 can be routed in thehousing 31 to minimize the tube overlapping section B. Therefore, when the pump is used, the load for squeezing theintermediate portion 36 of thedrain tube 27 with the pressingmember 46 is made equal to a load required for squeezing asingle drain tube 27 along the entire circumference of thehousing 31, while substantially eliminating the amount of leak. Thus, the pump torque is reduced and the pump efficiency is improved. - The present invention is not limited to the above described embodiment, but may be embodied as follows, for example.
- The
upstream section 36 a and thedownstream section 36 b of the tube overlapping section B may be made of a material having a lower rigidity than that of sections of theintermediate portion 36 other than the tube overlapping section B, thereby increasing the flexibility of the tube overlapping section B. This reliably reduces the load required for squeezing the tube overlapping section B with the pressingmember 46. - The frictional coefficient on the cam surfaces C of the
pump wheel 32 may be partially changed in accordance with the configuration of the tube thepump 29. This allows the pressingmember 46 to press thedrain tube 27 in a favorable manner, and to smoothly move between the pressing position and the non-pressing position. As a result, the pump torque is reduced and the pump efficiency is improved. - The contact parts N in the cam surfaces C may be formed as components separate from the
large plate 40, and made of a low friction material such as polytetrafluoroethylene and polyacetal or polystyrene of a sliding grade. In this case, the low frictional resistance members are molded products that are press fitted to thelarge plate 40. Accordingly, the sliding resistance between theshaft 45 and the contact parts N when the pressingmember 46 presses theintermediate portion 36 of thedrain tube 27 is reliably reduced by a simple structure. - Low friction coating such as polytetrafluoroethylene or grease for reducing frictional resistance may be applied to the contact parts N of the cam surfaces C. Accordingly, the sliding resistance between the
shaft 45 and the contact parts N when the pressingmember 46 presses theintermediate portion 36 of thedrain tube 27 is easily and reliably reduced. - The contact parts N on the cam surfaces C may be subject to surface treatment such as polishing, thereby reducing the frictional coefficient of the contact parts N.
- The retaining pins 47 may be replaced by seal rings functioning as retaining members.
- Without reducing the frictional resistance between the
shaft 45 of the pressingmember 46 and the cam surfaces C of thepump wheel 32, the frictional coefficient of one of the sliding section of theshaft 45 and the sliding section of theroller 44 may be set lower than the frictional coefficient of the other. Since this reduces the frictional resistance of theshaft 45 and theroller 44, only theroller 44 is rotated without causing theshaft 45 to rotate when thepump wheel 32 is rotated during the activation of the pump. Therefore, the load applied to the cam surfaces C from theshaft 45 is reduced, which reduces the wear of the cam surfaces C caused by theshaft 45. Further, the frictional resistance between theshaft 45 and theroller 44. This reduces the force required for rotating thepump wheel 32 when actuating the pump. Thus, the pump torque is reduced and the pump efficiency is improved. - The
shaft 45 may be press fitted to theinsertion hole 44 a of theroller 44 so that theroller 44 and theshaft 45 rotate integrally. - The
shaft 45 of the pressingmember 46 may be made of a low friction material such as polytetrafluoroethylene. - Only parts of the
shaft 45 of the pressingmember 46 that slide on the cam surfaces C, that is, only both end portions of theshaft 45 may be formed of a low friction material such as polytetrafluoroethylene, metal, and polyacetal or polystyrene of a sliding grade. - The
roller 44 and theshaft 45 may be formed as an integral body. - The
upstream recess 38 and thedownstream recess 39 do not need to be arranged to be adjacent to each other in the circumferential direction of the innercircumferential surface 31 b of thehousing 31. - Either one of the
upstream recess 38 and thedownstream recess 39 may be omitted. - Instead of the
roller 44 and theshaft 45, the pressingmember 46 may include a sliding member that slides on theintermediate portion 36 of thedrain tube 27, while pressing theintermediate portion 36. - In the illustrated embodiment, the liquid ejection apparatus, which is equipped with the
tube pump 29, is embodied as theinkjet printer 11. However, for example, the present invention may be embodied as a liquid ejection apparatus used for manufacturing color filters for liquid crystal displays or pixels of organic EL displays. Alternatively, thetube pump 29 may be mounted on apparatus other than liquid ejection apparatuses.
Claims (14)
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 .
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2006-236911 | 2006-08-31 | ||
JP2006236909A JP4175412B2 (en) | 2006-08-31 | 2006-08-31 | Tube pump and liquid injection device |
JP2006236911A JP4232805B2 (en) | 2006-08-31 | 2006-08-31 | Tube pump and liquid injection device |
JP2006-236909 | 2006-08-31 |
Publications (1)
Publication Number | Publication Date |
---|---|
US20080056918A1 true US20080056918A1 (en) | 2008-03-06 |
Family
ID=39151801
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US11/848,989 Abandoned US20080056918A1 (en) | 2006-08-31 | 2007-08-31 | Tube pump and liquid ejection apparatus |
Country Status (1)
Country | Link |
---|---|
US (1) | US20080056918A1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20170370356A1 (en) * | 2015-03-31 | 2017-12-28 | Brother Kogyo Kabushiki Kaisha | Tube pump and printer provided with the same |
WO2020018876A1 (en) * | 2018-07-20 | 2020-01-23 | Nano-Dimension Technologies, Ltd. | Contactless inkjet print head maintenance |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5897300A (en) * | 1995-09-08 | 1999-04-27 | Graymills Corporation | Quick-release bolt for use with pump housing |
US20050030354A1 (en) * | 2003-04-04 | 2005-02-10 | Seiko Epson Corporation | Tube pump and liquid injection apparatus |
US6955251B2 (en) * | 2000-08-08 | 2005-10-18 | Ntn Corporation | Clutch unit |
-
2007
- 2007-08-31 US US11/848,989 patent/US20080056918A1/en not_active Abandoned
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5897300A (en) * | 1995-09-08 | 1999-04-27 | Graymills Corporation | Quick-release bolt for use with pump housing |
US6955251B2 (en) * | 2000-08-08 | 2005-10-18 | Ntn Corporation | Clutch unit |
US20050030354A1 (en) * | 2003-04-04 | 2005-02-10 | Seiko Epson Corporation | Tube pump and liquid injection apparatus |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20170370356A1 (en) * | 2015-03-31 | 2017-12-28 | Brother Kogyo Kabushiki Kaisha | Tube pump and printer provided with the same |
US10119534B2 (en) * | 2015-03-31 | 2018-11-06 | Brother Kogyo Kabushiki Kaisha | Tube pump and printer provided with the same |
WO2020018876A1 (en) * | 2018-07-20 | 2020-01-23 | Nano-Dimension Technologies, Ltd. | Contactless inkjet print head maintenance |
CN112955326A (en) * | 2018-07-20 | 2021-06-11 | 维纳米技术公司 | Non-contact inkjet printhead maintenance |
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Legal Events
Date | Code | Title | Description |
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AS | Assignment |
Owner name: SEIKO EPSON CORPORATION, JAPAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:HARADA, SHUHEI;REEL/FRAME:020034/0013 Effective date: 20070828 |
|
STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION |