Abstract:
An ink cartridge is detachably mounted on a cartridge holder. At least one first reflector is provided in the cartridge holder. A reflective-type optical sensor includes a light emitter and a light receiver. The optical sensor is operable to form an optical path originated from the light emitter to the light receiver via the first reflector. A shading member is provided in the ink cartridge operable to shade the optical path when the ink cartridge is mounted on the cartridge holder. A second reflector is provided in the ink cartridge. The second reflector reflects light emitted from the light emitter and varies an intensity thereof in accordance with an ink amount remaining in the ink cartridge.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application is a divisional of U.S. patent application Ser. No. 11/831,511, filed Jul. 31, 2007, pending; which is a continuation of U.S. patent application Ser. No. 11/409,068, filed Apr. 24, 2006, now U.S. Pat. No. 7,261,403; which is a continuation of U.S. patent application Ser. No. 10/413,578, filed Apr. 15, 2003, now U.S. Pat. No. 7,044,590, which claims the benefit of Japanese Patent Application No. 2002-113940, filed Apr. 16, 2002, the entire contents of each of which are hereby incorporated by reference in this application. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to an ink cartridge detector operable to detect whether or not an ink cartridge is properly mounted on a cartridge holder. The invention also relates to an ink jet printer provided with the above mentioned ink cartridge detector, and to the ink cartridge to be employed in the above mentioned ink cartridge detector. 
         [0003]    There has been widely used an ink jet printer of a type that prints characters and images on a printing medium by discharging ink which is supplied from an ink tank onto the printing medium through a print head. In the ink jet printer of this type, the ink tank of a cartridge system (hereinafter referred to as an “ink cartridge”) has been widely employed so as to facilitate supply of the ink. 
         [0004]    In the above described ink jet printer, it has been required to detect an amount of remaining ink in the ink cartridge and a mounting condition of the ink cartridge for the purpose of preventing defective printing due to shortage of the remaining ink in the ink cartridge or incomplete mounting of the ink cartridge, or for the purpose of issuing an alarm indicating the shortage or the incomplete mounting. For this reason, there have been proposed mechanisms for enabling the amount of the remaining ink and the incomplete mounting of the ink cartridge to be detected by a single optical sensor of the reflective type (disclosed in Japanese Patent Publications Nos. 10-230616A and 9-174877A, for example). 
         [0005]    In the above described detectors, a light beam is emitted from the optical sensor onto two reflectors (prisms) which are provided in a bottom of the ink cartridge, and the amount of the remaining ink and the mounting condition are detected on the basis of amounts of reflective light beams received from the reflectors. Specifically, the reflector for detecting the amount of the remaining ink is transparent so that reflectivity (intensity of reflected light) may vary according to the amount of the remaining ink, while the reflector for detecting the mounting condition is mirror-finished so that the light can be reflected irrespective of the amount of the remaining ink. 
         [0006]    However, in the above described related-art ink jet printer, there have been such problems as described below. 
         [0007]    i) It has been necessary for the ink cartridge to be provided with two reflectors which are formed of separate members, and hence, the number of components and production steps are increased, creating a high cost for the ink cartridge. 
         [0008]    ii) Because the reflectors of the ink cartridge are exposed inside the printer even when a printing operation is performed, there has been such a possibility that spots such as ink splashed during the printing operation might adhere to the reflectors to make the detection by the optical sensor unstable. 
         [0009]    iii) When the optical sensor has received the reflective light, it is decided that the ink cartridge has been properly mounted. Therefore, when the optical sensor has received an exterior turbulent light, it has been liable to be decided that the ink cartridge has been properly mounted, even though the ink cartridge has not yet been mounted. As such, the printing operation might be commenced without proper mounting of the ink cartridge. 
       SUMMARY OF THE INVENTION 
       [0010]    It is an object of the invention to provide an ink cartridge detector, in which necessity for providing an ink cartridge with a reflector for detecting the mounting condition can be eliminated although the mounting condition of the ink cartridge is detected by an optical sensor of reflective type, whereby not only reduction of cost for the ink cartridge can be attained, but also an erroneous recognition of the mounting condition due to soils or ink splash on the reflector or an exterior turbulent light can be prevented. 
         [0011]    It is also an object of the invention to provide an ink jet printer incorporating such an ink cartridge detector, and an ink cartridge detected by such an ink cartridge detector. 
         [0012]    In order to achieve the above objects, according to the invention, there is provided an ink cartridge detector, comprising: 
         [0013]    an ink cartridge; 
         [0014]    a cartridge holder, on which the ink cartridge is detachably mounted; 
         [0015]    at least one first reflector, provided in the cartridge holder; 
         [0016]    a reflective-type optical sensor, including a light emitter and a light receiver, the optical sensor operable to form an optical path originated from the light emitter to the light receiver via the first reflector; and 
         [0017]    a shading member, provided in the ink cartridge operable to shade the optical path when the ink cartridge is mounted on the cartridge holder. 
         [0018]    The first reflector may be integrally fixed on a bottom portion of the cartridge holder. In such a configuration, not only the structure can be simplified, but also reliability of detecting the mounting condition of the ink cartridge can be enhanced, in comparison with a case where the reflector is provided as a movable member. 
         [0019]    Further, the shading member may be integrally formed with the ink cartridge at a lower portion thereof (a downstream portion with regard to an inserting direction of the ink cartridge with respect to the cartridge holder). In such a configuration, the number of components and production steps of the ink cartridge can be reduced. 
         [0020]    The ink cartridge may be formed with a recess which covers the first reflector when the ink cartridge is mounted on the cartridge holder, so that at least one of side walls forming the recess serves as the shading member. In such a configuration, because the first reflector is covered when the ink cartridge has been mounted, soils or ink splash on the first reflector caused by a printing operation can be reliably prevented. 
         [0021]    The shading member may not shade the optical path when the ink cartridge is provisionally mounted on the cartridge holder. In such a configuration, such an inconvenience that the printing operation is conducted in a provisionally mounted state of the ink cartridge can be avoided. 
         [0022]    The ink cartridge detector may further comprise a first engagement member provided in the ink cartridge, and a second engagement member provided in the cartridge holder. The first engagement member may come into contact with the second engagement member such that the ink cartridge is retained at a first position in which the shading member does not shade the optical path. In addition, the first engagement member may engage with the second engagement member such that the ink cartridge is retained at a second position in which the shading member shades the optical path. 
         [0023]    In one embodiment, the first engagement member is provided as a convex portion formed on the ink cartridge; the second engagement member is provided in a free end portion of an elastic member which is supported by the cartridge holder in a cantilevered manner; the second engagement member is a V-shaped member including a first slope portion and a second slope portion so as to convex toward the ink cartridge; the convex portion is brought into contact with the first slope portion when the ink cartridge is retained at the first position; and the convex potion is retained by the second slope portion when the ink cartridge is retained at the second position. 
         [0024]    Preferably, the optical sensor and the cartridge holder are movable relative to each other. Here, it is preferable that a plurality of first reflectors are arranged in a direction of relative movement between the optical sensor and the cartridge holder. In such a configuration, it is possible to detect the mounting conditions of a plurality of the ink cartridges by the same optical sensor. 
         [0025]    Also, the ink cartridge detector may further comprise a second reflector, provided in the ink cartridge, which reflects light emitted from the light emitter and varies an intensity thereof in accordance with an ink amount remaining in the ink cartridge. Here, the second reflector may be operable to form a part of an optical path originated from the light emitter to the light receiver, when the ink cartridge is mounted on the cartridge holder. In such a configuration, it is possible to detect both the mounting condition of the ink cartridge and the amount of the remaining ink by the same optical sensor. 
         [0026]    According to the invention, there is also provided an ink jet printer comprising the above ink cartridge detector. 
         [0027]    Further, according to the invention, there is also provided an ink cartridge, operable to be detachably attached to a cartridge holder provided with a first reflector capable of forming a part of an optical path originated from a light emitter of an external optical sensor to a light receiver of the optical sensor, the ink cartridge comprising: 
         [0028]    an ink reservoir, storing ink therein; 
         [0029]    a second reflector, which reflects light emitted from the light emitter and varies an intensity thereof in accordance with an ink amount remaining in the ink reservoir, the second reflector operable to form a part of an optical path originated from the light emitter to the light receiver; and 
         [0030]    a shading member, which shades the optical path, which has been formed by the first reflector and the optical sensor, when the ink cartridge is mounted on the cartridge holder. 
         [0031]    Preferably, the shading member shades the first reflector from the light emitted from the light emitter, when the ink cartridge is mounted on the cartridge holder. 
         [0032]    Here, a recess may be formed so as to cover the first reflector when the ink cartridge is mounted on the cartridge holder, so that at least one of side walls forming the recess serves as the shading member. The recess may be shaped as to surround an outer periphery of the first reflector. 
         [0033]    Also, it is preferable that the recess is formed on a face opposing to the cartridge holder. 
         [0034]    The ink cartridge may further comprise a first engagement member. In one embodiment, the first engagement member comes into contact with a second engagement member provided in the cartridge holder, such that the ink cartridge is retained at a first position in which the shading member does not shade the optical path. The first engagement member engages with the second engagement member such that the ink cartridge is retained at a second position in which the shading member shades the optical path. 
         [0035]    Preferably, the second reflector and the shading member are juxtaposed in a direction in which the cartridge holder and the optical sensor are to be moved relative to each other. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0036]    The above objects and advantages of the present invention will become more apparent by describing in detail preferred exemplary embodiments thereof with reference to the accompanying drawings, wherein: 
           [0037]      FIG. 1  is a side view schematically showing an interior structure of a printer; 
           [0038]      FIG. 2  is a plan view schematically showing the interior structure of the printer; 
           [0039]      FIG. 3  is a perspective view of a carriage on which a print head is mounted; 
           [0040]      FIG. 4  is a front view of an ink supply section showing a state in which ink cartridges are not mounted. 
           [0041]      FIG. 5  is a front view of the ink supply section showing a state in which the ink cartridges are mounted; 
           [0042]      FIG. 6  is a perspective view of the ink supply section showing the state in which the ink cartridges are not mounted; 
           [0043]      FIG. 7  is a perspective view of the ink supply section showing the state in which the ink cartridges are mounted; 
           [0044]      FIG. 8  is a perspective view of the ink cartridge as viewed from a bottom thereof; 
           [0045]      FIGS. 9A to 9C  are explanatory views showing detection of mounting condition and detection of an amount of remaining ink; 
           [0046]      FIG. 10  is a sectional view of the ink supply section taken along a line X-X in  FIG. 7 , showing a state where the ink cartridge is plenarily mounted; and 
           [0047]      FIG. 11  is a sectional view of the ink supply section taken along a line Y-Y in  FIG. 7 , showing a state where the ink cartridge is provisionally mounted. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0048]    One embodiment of the invention will be described referring to the accompanying drawings. As shown in  FIG. 1 , an inlet  11  for inserting paper P by hand is provided on a front face of a printer  10 . An outlet  12  for discharging the paper P after printing is provided on an upper face of the printer  10 . Inside the printer  10 , there is formed a paper feeding path  13  in a V-shape in a side view extending from the inlet  11  to the outlet  12 , and a paper feeding roller unit  14  and a print head  15  are arranged on the paper feeding path  13 . The paper feeding roller unit  14  includes a paper feeding roller  16  and a paper holding roller  17  which are opposed to each other on both sides of the paper feeding path  13 , and adapted to clamp and transport the paper P in accordance with driving rotation of the paper feeding roller  16 . 
         [0049]    The print head  15  is mounted on a carriage  18  which reciprocates in a lateral direction of the paper feeding path  13  (in a direction from the left to the right in  FIG. 2 ), and adapted to perform dot matrix printing on the paper P. The position of the paper P is regulated by a platen  19 . The printing system of the print head  15  is an ink jet system in which characters or images are printed on the paper P by discharging ink, and the ink used for printing is supplied to the print head  15  from an ink supply section  20  which is provided in a rear area of the printer  10 . 
         [0050]    The carriage  18  is supported by a pair of front and rear guide shafts  21 ,  22  so as to move from the left to the right, and is forcibly moved in accordance with driving motion of a carriage driving mechanism  23 . The carriage driving mechanism  23  includes a cam shaft  24  which is arranged below the front guide shaft  21  in parallel thereto, and a carriage motor  26  for actuating the cam shaft  24  to rotate by way of a reduction gear train  25  ( FIG. 2 ). On an outer peripheral face of the cam shaft  24 , there is formed a cam groove in a spiral shape (not shown), with which a cam follower  27  extending from the carriage  18  is adapted to be engaged. When the cam shaft  24  is rotated in accordance with the driving motion of the carriage motor  26 , the cam follower  27  is shifted in an axial direction with spiral shifting action of the cam groove. In this manner, it will be possible to reciprocate the carriage  18  from the left to the right in accordance with normal and reverse drives of the carriage motor  26 . 
         [0051]    As shown in  FIG. 3 , the print head  15  is mounted on an upper part of the carriage  18 . A flat cable  28  and ink tubes  29  having flexibility are drawn from a side area of the print head  15 , and the ink is supplied to the print head  15  from the ink supply section  20  by way of the ink tubes  29 . The carriage  18  has a sensor mounting part  18   a  which is extended downwardly from its rear part, and an optical sensor  30  of a reflective type which includes a light emitting element  30   a  for emitting a light beam to the rear and a light receiving element  30   b  for receiving a reflective light beam is attached to a back face of the sensor mounting part  18   a.    
         [0052]    As shown in  FIG. 4 , the ink supply section  20  includes a cartridge holder  31  which is provided in a rear area inside the printer  10 , and two ink cartridges  32 A,  32 B which are detachably mounted on the cartridge holder  31  from the above. As shown in  FIG. 8 , an ink reservoir  34 A is partitioned inside the ink cartridge  32 A to store secondary ink (for example, colored ink such as cyan, magenta, yellow, red, green, blue). The secondary ink is appropriately discharged from an ink outlet  33 A formed in a bottom of the ink cartridge  32 A. A waste ink reservoir  36  is also partitioned inside the ink cartridge  32 A to store waste ink supplied from a recovery inlet  35  formed in the bottom. When the ink cartridge  32 A has been mounted at a predetermined (specific) position on the cartridge holder  31 , the ink outlet  33 A and the recovery inlet  35  are communicated with connecting ports  37 A,  38  which are formed in a bottom of the cartridge holder  31 , thus permitting supply of the secondary ink and recovery of the waste ink. 
         [0053]    On the other hand, inside the ink cartridge  32 B, there are partitioned an ink reservoir  34 B which stores primary ink (for example, black ink) and appropriately discharges the primary ink from an ink outlet  33 B in a bottom of the ink cartridge  32 B. When the ink cartridge  32 B has been mounted at a predetermined (specific) position on the cartridge holder  31 , the ink outlet  33 B is communicated with a connecting port  37 B which is formed in the bottom of the cartridge holder  31 , thus permitting supply of the primary ink. 
         [0054]    The ink cartridges  32 A,  32 B are arranged in a row along a moving direction of the carriage  18  (the optical sensor  30 ). The ink cartridges  32 A,  32 B are respectively provided, at positions opposed to a moving path L (see  FIG. 5 ) of the optical sensor  30  on their front faces, with reflectors (reflectors for detecting an amount of remaining ink)  39 A,  39 B in a shape of prism having transparency. The reflectors  39 A,  39 B have a shape of a right triangle prism, and two prism reflective faces S 1 , S 2  which are at a right angle with respect to each other are protruded into the ink reservoirs  34 A,  34 B. As shown in  FIG. 9B , when the optical sensor  30  is moved to a position opposed to the reflector  39 A and a light is emitted thereto, the emitted light is reflected at the prism reflective faces S 1 , S 2  sequentially while passing interiors of the reflector  39 A, and received by the light receiving element  30   b . When the optical sensor  30  is moved to a position opposed to the reflector  39 B and a light is emitted thereto, the emitted light is reflected at the prism reflective faces S 1 , S 2  sequentially while passing interiors of the reflector  39 B, and received by the light receiving element  30   b.    
         [0055]    Reflectivity (refraction index) of the prism reflective faces S 1 , S 2  is low in the case where levels of the remaining ink in the ink reservoirs  34 A,  34 B are higher than the prism reflective faces S 1 , S 2 , and is high in the case where the levels of the remaining ink are lower than the prism reflective faces S 1 , S 2 . In short, in a state where the prism reflective faces S 1 , S 2  are in contact with the ink as shown in  FIG. 9A , an emitted light beam of the optical sensor  30  is absorbed by the ink to have a low reflectivity (the intensity of reflected light is made low), and in a state where the prism reflective faces S 1 , S 2  are in contact with air as shown in  FIG. 9B , the light beam is not absorbed by the ink to have a high reflectivity (the intensity of reflected light is made high). In this manner, it will be possible to detect the amount of the remaining ink (presence or absence of the ink at the predetermined level) in the ink cartridges  32 A,  32 B on the basis of a value detected by the light receiving element  30   b  of the optical sensor  30 . 
         [0056]    As shown in  FIGS. 4 and 6 , on the bottom of the cartridge holder  31 , two reflectors (reflectors for detecting mounting condition)  40 A,  40 B are fixed in a row along the moving direction of the carriage  18  (the moving path L of the optical sensor  30 ), in an upwardly protruding posture. Each of the reflectors  40 A,  40 B has a prism part  40   a  in a shape of a right triangle prism, and reflective light paths of the optical sensor  30  are formed by two prism reflective faces S 3 , S 4  which are at a right angle with respect to each other, in the same manner as the reflectors  39 A,  39 B for detecting the amount of the remaining ink. On the other hand, recesses (hollowed parts)  41 A,  41 B are integrally formed in respective lower portions of the ink cartridges  32 A,  32 B. When the ink cartridges  32 A,  32 B have been mounted at the predetermined positions of the cartridge holder  31 , the reflectors  40 A,  40 B are inserted into the recesses  41 A,  41 B, and the surroundings are covered. On this occasion, shield parts  42 A,  42 B which are integrally formed on one side faces of the recesses  41 A,  41 B (wall portions opposed to the optical sensor) are interposed between the optical sensor  30  and the reflectors  40 A,  40 B, so as to shield light paths (irradiation paths and reflective paths) between the optical sensor  30  and the reflectors  40 A,  40 B. 
         [0057]    As shown in  FIGS. 4 and 9C , in the state where the ink cartridges  32 A,  32 B are not mounted on the cartridge holder  31 , the reflectors  40 A,  40 B are exposed. When the optical sensor  30  is moved to a position opposed to the reflector  40 A in this state, the emitted light is sequentially reflected at the reflective faces S 3 , S 4  while passing the interior of the reflector  40 A, and will enter the light receiving element  30   b . When the optical sensor  30  is moved to a position opposed to the reflector  40 B in this state, the emitted light is sequentially reflected at the reflective faces S 3 , S 4  while passing the interior of the reflector  40 B, and will enter the light receiving element  30   b . On the other hand, as shown in  FIGS. 9A and 9B , in the state where the ink cartridges  32 A,  32 B have been mounted on the cartridge holder  31 , front areas of the reflectors  40 A,  40 B are covered with the shield parts  42 A,  42 B. When the optical sensor  30  is moved to the position opposed to the reflector  40 A in this state, the emitted light is shielded by the shield part  42 A, and will not reach the reflector  40 A nor the light receiving element  30   b  of the optical sensor  30 . When the optical sensor  30  is moved to the position opposed to the reflector  40 B in this state, the emitted light is shielded by the shield part  42 B, and will not reach the reflector  40 B nor the light receiving element  30   b  of the optical sensor  30 . 
         [0058]    In this manner, it is possible to detect the mounting condition of the ink cartridges  32 A,  32 B by the optical sensor  30 , without providing the ink cartridges  32 A,  32 B with the reflectors for detecting the mounting condition. Moreover, in the state where the ink cartridges  32 A,  32 B are not mounted on the cartridge holder  31  as described above, since the light receiving element  30   b  is always subjected to the light emission, an exterior turbulent light will not influence detection results of the mounting condition of the ink cartridges  32 A,  32 B, even though the exterior turbulent light is emitted to the light receiving element  30   b . Further, in the state where the ink cartridges  32 A,  32 B have been mounted on the cartridge holder  31 , since the reflectors  40 A,  40 B are covered with the recesses  41 A,  41 B, the ink will not adhere to the reflectors  40 A,  40 B, even though the ink is splashed during the printing operation. As a result, it is possible to prevent an erroneous detection caused by ink adhering to the reflectors  40 A,  40 B. 
         [0059]      FIG. 10  is a sectional view of the ink supply section taken along a line X-X in  FIG. 7 , showing a state where the ink cartridge is plenarily mounted, and  FIG. 11  is a sectional view of the ink supply section taken along a line Y-Y in  FIG. 7 , showing a state where the ink cartridge has been provisionally mounted. As shown in these drawings, there are provided, in a rear part of the cartridge holder  31 , two lock plates  43 A,  43 B in an upright manner. The lock plates  43 A,  43 B are elastic plate members formed with V-shaped locking portions  44 A,  44 B in their upper end portions. When the ink cartridges  32 A,  32 B have been mounted on the cartridge holder  31  from above, convex portions  45 A,  45 B projected from back faces of the ink cartridges  32 A,  32 B lie on the lock portions  44 A,  44 B of the lock plates  43 A,  43 B, as shown in  FIG. 11 , to hold the ink cartridges  32 A,  32 B in a provisionally mounted state. On this occasion, the shield parts  42 A,  42 B of the ink cartridges  32 A,  32 B are located above the prism parts  40   a  of the reflectors  40 A,  40 B, and the light paths between the optical sensor  30  and the reflectors  40 A,  40 B will not be shielded. 
         [0060]    Further, in the above described provisionally mounted state, when the ink cartridges  32 A,  32 B are pushed downward, the lock plates  43 A,  43 B are pressed by the convex portions  45 A,  45 B to be tilted so as to once retreat backward, and then, ride over the convex portions  45 A,  45   b  to be tilted so as to be returned forward. After the lock plates  43 A,  43 B have been tilted to be returned, the locking portions  44 A,  44 B are engaged with upper parts of the convex portions  45 A,  45 B as shown in  FIG. 10 , and the ink cartridges  32 A,  32 B are held (locked) in their mounting positions. On this occasion, the shield parts  42 A,  42 B of the ink cartridges  32 A,  32 B are interposed between the prism parts  40   a  of the reflectors  40 A,  40 B and the optical sensor  30  to shield the light path of the optical sensor  30 . 
         [0061]    As described above, according to this embodiment, the printer  10  is constructed by including the optical sensor  30  of a reflective type which projects the light to the cartridge holder  31  to detect the mounting conditions of the ink cartridges  32 A,  32 B on the basis of the reflective light, the reflectors  40 A,  40 B which are provided on the cartridge holder  31  to form the reflective light path of the optical sensor  30 , and the shield parts  42 A,  42 B which are provided in the ink cartridges  32 A,  32 B, and adapted to shield the light path of the optical sensor  30  when the ink cartridges  32 A,  32 B have been mounted on the cartridge holder  31 . In short, although the mounting condition of the ink cartridges  32 A,  32 B is detected by the optical sensor  30  of the reflective type, necessity for providing the ink cartridges  32 A,  32 B with the reflectors for detecting the mounting condition can be eliminated. Therefore, not only reduction of the cost for the ink cartridges  32 A,  32 B can be attained, but also, an erroneous recognition of the mounting condition due to soils such as ink splash on the reflectors or an exterior turbulent light can be prevented. 
         [0062]    Moreover, because the reflectors  40 A,  40 B are fixed members which are integrally provided in the bottom of the cartridge holder  31 , as compared with the reflectors  40 A,  40 B formed of movable members, not only the structure can be simplified, but also reliability of detecting the mounting condition can be enhanced. 
         [0063]    Further, because the shield parts  42 A,  42 B are integrally formed in the lower parts of the ink cartridges  32 A,  32 B, the number of the components and the production steps of the ink cartridges  32 A,  32 B can be decreased. 
         [0064]    Still further, because the ink cartridges  32 A,  32 B have the recesses  41 A,  41 B which cover the reflectors  40 A,  40 B when they have been mounted on the cartridge holder  31 , and the shield parts  42 A,  42 B are formed at the one side faces of the recesses  41 A,  41 B, the reflectors  40 A,  40 B can be protected when the ink cartridges have been mounted, and defective detection due to soils such as ink splash or damage of the reflectors  40 A,  40 B can be prevented. 
         [0065]    Furthermore, the shield parts  42 A,  42 B will not shield the light path of the optical sensor  30  when the ink cartridges  32 A,  32 B are provisionally mounted on the cartridge holder  31 , and therefore, problems such as conducting the printing operation in the provisionally mounted state of the ink cartridges  32 A,  32 B can be avoided. 
         [0066]    Still further, because the cartridge holder  31  and the optical sensor  30  are relatively movable with respect to each other, it is possible to detect the mounting conditions of a plurality of the ink cartridges  32 A,  32 B, and to detect the amount of the remaining ink in the ink cartridges  32 A,  32 B by the same optical sensor  30 . 
         [0067]    Still further, the cartridge holder  31  is provided with a plurality of the reflectors  40 A,  40 B which are arranged in a row along the direction of the relative movement of the optical sensor  30  (along the line L shown in  FIGS. 4 and 5 ), and accordingly, the same optical sensor  30  can detect the mounting conditions of the plurality of the ink cartridges  32 A,  32 B. 
         [0068]    In addition, the ink cartridges  32 A,  32 B are provided with the reflectors  39 A,  39 B for detecting the amount of the remaining ink, enabling the amount of the remaining ink to be detected by the optical sensor  30 , and accordingly, the same optical sensor  30  can detect the amounts of the remaining ink as well as the mounting conditions of the ink cartridges  32 A,  32 B. 
         [0069]    Although one of the embodiments according to the invention has been described heretofore, the present invention is not limited to those matters shown in the above described embodiment, but may include such a scope as those skilled in the art can make modification and application of the invention, on the basis of the description in the claims and in the detailed description of the invention, and the well known art. 
         [0070]    For example, although in the above described embodiment, the shield part is formed on one side face of the recess which is integrally formed in the ink cartridge, the shield part may be in any shape, provided that it can shield the light path of the optical sensor  30  when the ink cartridge has been mounted on the cartridge holder. For example, the shield part may be formed in a hook-like shape (L-shape) on the one side face of the ink cartridge. 
         [0071]    Moreover, although in the above described embodiment, the ink cartridges are mounted on the printer body, the invention can be realized in the printer in which the ink cartridges are mounted on the carriage. Specifically, by providing the reflectors on the cartridge holder which is mounted on the carriage, and detecting them by the optical sensor which is provided on the printer body, similar function and advantageous effects to those in the above described embodiment can be obtained. 
         [0072]    According to the present invention as has been herein before described, although the mounting condition of the ink cartridge is detected by the optical sensor of a reflective type, necessity for providing the ink cartridge with the reflectors for detecting the mounting condition is eliminated, and not only reduction of the cost for the ink cartridge can be attained, but also, an erroneous recognition of the mounting condition due to soils such as ink splash on the reflectors or an exterior turbulent light can be prevented.