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Tube pump and liquid ejecting apparatusTube pump and liquid ejecting apparatus description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20080056919, Tube pump and liquid ejecting apparatus. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001]The entire disclosure of Japanese Patent Application No. 2006-236910, filed Aug. 31, 2006 is expressly incorporated herein by reference. [0002]1. Technical Field [0003]The present invention relates to a liquid ejecting apparatuses. More specifically, the present invention relates to a tube pump for a liquid ejecting apparatus. [0004]2. Related Art [0005]One example of a liquid ejecting apparatus is a ink jet printer (hereinafter, referred to as "a printer"), which ejects a liquid onto a target from a nozzle formed in a liquid ejecting head. In most printers, the nozzle of the print head (liquid ejecting head) is open, meaning that ink solvent in the nozzle may evaporate, causing ink ejection failure as the ink viscosity increases. In response to this problem, printers generally include a head maintenance mechanism. [0006]Generally, the head maintenance mechanism includes a cap which is used to seal the surface of the nozzle and a sucking pump located in an ink discharging passage which communicates with the cap. The head maintenance mechanism prevents failed ink ejection by using the sucking pump to generate a negative pressure in the cap in order to remove the ink with increased viscosity from the nozzle. Typically, the sucking pump uses a tube pump, such as the tube pump disclosed in Japanese Patent Application No. JP-A-2001-301195. [0007]The tube pump disclosed in JP-A-2001-301195 includes a substantially cylindrical housing, referred to as a "guide member," for holding a middle portion of a flexible tube. The guide member includes a rotating body which rotates about an axis of the guide member and a roller or pressing member which is capable of pressing the tube. The roller moves along an inner circumferential surface of the guide member when the rotating body rotates in a predetermined direction. [0008]The portion of flexible tubing is wound around the inner circumference of the guide member into a circular shape (.alpha. shape). That is, the tube is arranged such that an upstream portion and a downstream portion of the tube partially overlap each other. [0009]Accordingly, when the rotating body operates by using a roller, which moves along the inner surface of the guide member in order to press portions of the tube against the inside surface of the guide member. Using this method, the guide member is able to depressurize the upstream portion of the tubing, creating a negative pressure in the cap, which causes the ink of increased viscosity to be sucked out of the nozzle. [0010]One difficulty of the tube pump disclosed in JP-A-2001-301195, however, is that a portion of the tube is wound so as to have an .alpha. shape in the housing, so that there is a portion of the upstream portion and the downstream portion that overlap each other. At times, the overlapping portions of the tube may be squashed by the roller. In order to squash the overlapped portion, a pressing force that is twice the force required to press a single portion of tubing is needed. In order to provide the requisite amount of force to press the overlapping section of the tube, a motor is required that is capable of enhancing pump torque and handling the load variation must be used. As a result, the motor is more expensive and larger, and may have difficulties stably driving the tube pump. BRIEF SUMMARY OF THE INVENTION [0011]One advantage of some aspects of the invention is a tube pump for a liquid ejecting apparatus with reduced pump torque and pump load variation. [0012]One aspect of the invention, is a tube pump which includes a housing with a cylindrical inner circumferential surface wherein a portion of flexible tube is wound around the cylindrical inner circumferential surface such that an upstream portion and a downstream portion of the tube partially overlap each other at a overlapping portion. The tube pump further comprises and a pressing member for pressing the flexible tube which is movably housed along the inner circumferential surface of the housing, wherein the housing includes a relief portion for releasing either the upstream portion or the downstream portion from the pressing of the pressing member. [0013]Another aspect of the invention is a liquid ejecting apparatus including a liquid ejecting head capable of ejecting a liquid from a nozzle formed on a nozzle formation surface; a cap capable of sealing the nozzle formation surface; and a sucking mechanism that capable of removing the liquid from the cap, wherein the sucking mechanism includes the tube pump described above. [0014]By using relief portions which correspond to the tube overlapping position in the inner circumferential surface of the housing, either the upstream portion or the downstream portion is moved to the relief portion, releasing one portion of the overlapping section from the pressing of the pressing member. As a result, it is possible to reduce the load required for the pressing member to compress the overlapping portion, thereby reducing pump torque and load variation in the pump. BRIEF DESCRIPTION OF THE DRAWINGS [0015]The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. [0016]FIG. 1 is a perspective view illustrating an ink jet printer according to an embodiment of the invention; [0017]FIG. 2 is a schematic sectional view illustrating the major components shown in FIG. 1; [0018]FIG. 3 is a perspective view illustrating a tube pump; [0019]FIG. 4 is an exploded perspective view of the tube pump; [0020]FIG. 5 is a top sectional view of the tube pump; [0021]FIG. 6 is an exploded perspective view of a pressing member which is assembled into a pump foil; and Continue reading about Tube pump and liquid ejecting apparatus... Full patent description for Tube pump and liquid ejecting apparatus Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Tube pump and liquid ejecting apparatus patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Tube pump and liquid ejecting apparatus or other areas of interest. ### Previous Patent Application: Tube pump and liquid ejection apparatus Next Patent Application: Actuators and fluid delivery systems using such actuators Industry Class: Pumps ### FreshPatents.com Support Thank you for viewing the Tube pump and liquid ejecting apparatus patent info. 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