Abstract:
A cartridge is attached to a printer that performs a printing operation only when the cartridge is a predetermined kind of the cartridge. The cartridge includes a first predetermined number of magnet holders provided on the cartridge and a second predetermined number of magnets each of which is received in a corresponding one of the magnet holders. A maximum value of the second predetermined number is equal to the first predetermined number. A combination of the magnet holders having the magnets therein indicates the kind of the cartridge. The image forming apparatus comprises a detector section and an identifying section. The detector has magnetic sensor elements each of which detects a magnetic flux of a corresponding one of the magnets. The identifying section compares reference data with a combination of outputs of the magnetic sensor elements so as to identify the kind of the cartridge.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to cartridges such as toner cartridges, image drum cartridges, ink ribbon cartridges, and ink cartridges for use in printers, facsimile machines, and copying machines. The present invention also relates to a method of manufacturing these cartridges, and further to an image forming apparatus into which the above-described cartridges are attached. 
     2. Description of the Related Art 
     Conventional cartridges of the same construction and appearance have projections or cut-away portions different in shape from cartridge to cartridge, so that a cartridge can be identified from many other cartridges of the same appearance. The cartridge may have an area to which a seal is attached, so that users can identify the content in the cartridge. 
     However, the manufacture of cartridges having a portion of different shapes necessitates slightly different molds from cartridge to cartridge. This is uneconomical and an obstacle to the mass production of cartridges. 
     With the cartridge having a seal attached thereto, the user may inadvertently load an inappropriate cartridge into the printer. The use of an inappropriate cartridge causes poor image quality and trouble of machine operation. 
     SUMMARY OF THE INVENTION 
     The present invention was made in view of the aforementioned drawbacks and an object of the invention is to provide a cartridge where an image forming apparatus can detect the content of a cartridge when the cartridge is loaded therein. 
     In order to achieve the aforementioned object, the cartridge according to the present invention has a combination of magnets by which the content of the cartridge can be identified. 
     A cartridge is attached to an image forming apparatus that performs a printing operation only when the cartridge is a predetermined kind of the cartridge. The cartridge comprises a first predetermined number of magnet holders provided on the cartridge and a second predetermined number of magnets each of which is received in a corresponding one of the magnet holders. A maximum value of the second predetermined number is equal to the first predetermined number. A combination of the magnet holders having the magnets therein indicates the kind of the cartridge. 
     The image forming apparatus comprises a detector section and an identifying section. The detector has magnetic sensor elements each of which detects a magnetic flux of a corresponding one of the magnets. The identifying section compares reference data with a combination of outputs of the magnetic sensor elements so as to identify the kind of the cartridge. 
     Another image forming apparatus uses the aforementioned cartridge and a second cartridge attached thereto. The second cartridge includes a first detector that has first magnetic sensor elements, each of the first magnetic sensor elements detecting a magnetic flux of a corresponding one of the magnets of the first cartridge. The first cartridge includes a first predetermined number of magnet holders and a second predetermined number of magnets received in the magnet holders. A maximum value of the second predetermined number is equal to the first predetermined number. A combination of the magnet holders having the magnets received therein indicating a kind of the cartridge. 
     The image forming apparatus comprises a second detector and an identifying section. The second detector has second magnetic sensor elements, each of the magnets of the second magnetic sensor elements detecting a magnetic flux of a corresponding one of the magnets of the first cartridge. The identifying section determines contents of the first and second cartridges on the basis of outputs of the first and second magnetic sensor elements. 
     A method is used for manufacturing a cartridge having magnet holders that hold magnets attached thereto. The method comprising attaching at least one magnetic element into a corresponding one of the magnet holders formed of a non-magnetic material, the magnetic element not having been magnetized yet; and placing the cartridge in a magnetic field to magnetize the magnetic element. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limiting the present invention, and wherein: 
     FIG. 1 is an exploded partial perspective view of a toner cartridge according to a first embodiment; 
     FIGS. 2-2B are perspective views of a printer according to the first embodiment; 
     FIG. 2C illustrates the distance between adjacent Hall effect elements H 1 -H 4 ; 
     FIG. 3 illustrates mounting magnets to the magnet assembly  31  when the toner cartridge is assembled; 
     FIG. 4 is a perspective view illustrating when the toner cartridge is attached to an image drum cartridge of the printer of FIG. 2; 
     FIG. 5 is a partial cross-sectional view of the printer when the lid has been closed after the toner cartridge and ID cartridge are attached the printer; 
     FIG. 6 illustrates the presence and absence of magnets M 1 -M 4  and the On and OFF states of corresponding Hall effect elements, showing a when case magnets M 1  and M 3  are present; 
     FIG. 7 illustrates all possible combinations of the presence and absence of the magnets M 1 -M 4 ; 
     FIGS. 8A and 8B illustrate the steps for mounting the magnets M 1 -M 4  to the magnet assembly  31 ; 
     FIG. 9 illustrates the magnetizing process in which the magnetic elements Nm 1 -Nm 4  fitted into the magnet holders of the magnet assembly  31  are magnetized; 
     FIG. 10A is a perspective view of a printer  6  according to a third embodiment; 
     FIG. 10B is a fragmentary view of a lid  2  and the toner cartridge  3 ; 
     FIG. 11 is a partial cross-sectional side view of the printer  6  of FIG. 10A after the ID cartridge  7  and the toner cartridge  3  have been mounted and then the lid  2  has been closed; 
     FIG. 12A is a perspective view of the ID cartridge  7  with a partial exploded view; 
     FIG. 12B is a perspective view of a magnet assembly  71 ; 
     FIG. 12C illustrates the distance between adjacent Hall effect elements ME 1 -ME 4 ; 
     FIG. 13 illustrates, by way of example, the On and OFF states of the Hall effect elements and the presence and absence of the magnets; 
     FIG. 14 illustrates possible combinations of the presence and absence of ME 1 -ME 4  and MT 1 -MT 4 . 
     FIG. 15 is a partial exploded perspective view of a printer  9  according to a fourth embodiment; and 
     FIG. 16 is a partial cross-sectional view when the toner cartridge  3  and ID cartridge  10  have been attached to the printer  9  and the lid  2  has been closed. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will be described in detail with reference to the accompanying drawings. 
     First Embodiment 
     &lt;Construction&gt; 
     FIG. 1 is a fragmentary exploded perspective view of a toner cartridge  3  according to a first embodiment. Referring to FIG. 1, the toner cartridge  3  includes a main body, rotary cap  30 , magnet assembly  31 , and magnets M 1 -M 4 . The main body holds toner therein. 
     The rotary cap  30  includes a cylinder  30   a  and a lever  30   b  radially projecting from the cylinder  30   a , and is rotatably fitted over one end of the main body of the toner cartridge  3 . The cylinder  30   a  has a stopper  30   c  formed at an axial end of the cylinder  30   a . The lever  30   b  is formed with a recess  30   d  in which the magnets M 1 -M 4  are accommodated. 
     The magnet assembly  31  has magnet holders MH 1 -MH 4  formed therein into which the magnets M 1 -M 4  are firmly fitted. The magnet assembly  31  is securely assembled to the bottom surface of the recess  30   d  of the lever  30   b . The lid  2  has, for example, four magnet holders MH 1 -MH 4 , so that different toner cartridges having different toners can be identified by different arrangements of magnets M 1 -M 4 . A predetermined number of magnets are mounted into corresponding magnet holders. FIG. 1 shows, by way of example, all of four magnets fitted into corresponding magnet holders. 
     The materials of the lever  30 , magnet assembly  31 , and magnets M 1 -M 4  will be described. The rotary cap  30  and magnet assembly  31  are made of a non-magnetic material such as polystyrene. The magnets M 1 -M 4  are permanent magnets made of a magnetic material. The magnetic material is classified into two main groups; ferrite materials and metal magnetic materials. Ferrite material includes barium (Ba) ferrite and strontium (Sr) ferrite. The metal magnetic material includes Alnico and rare-earth magnetic materials. The rare earth magnetic materials include samarium-cobalt (SmCo) and neodymium-iron-boron (NdFeB). NdFeB is used in the present invention, i.e., the magnets M 1 -M 4  are in the form of magnetized NdFeB. 
     FIGS. 2A-2B are perspective views of a printer according to the first embodiment. 
     FIG. 2C illustrates the distance between adjacent Hall effect elements H 1 -H 4 . 
     Referring to FIGS. 2A and 2B, the toner cartridge  3  and ID cartridge  5  are loaded in the printer  1 . The toner cartridge  3  has magnets M 1 -M 4  mounted thereto. The toner cartridge  3  and ID cartridge  5  are consumable items that are replaced periodically. The printer  1  has a lid  2  to which a Hall effect element assembly  4  is mounted. The Hall effect element assembly  4  has Hall effect elements H 1 -H 4  that detect the magnetic fluxes of the corresponding magnets M 1 -M 4 . The content of the toner cartridge  3  is identified in terms of the ON and OFF states of the Hall effect elements H 1 -H 4 . 
     When the magnet assembly  31  is assembled into the recess  30   d  of the lever  30   b , the magnets accommodated in the magnet holders are sandwiched between the magnet assembly  31  and the bottom of the recess  30   d.    
     FIG. 3 illustrates mounting magnets to the magnet assembly  31  when the toner cartridge is assembled. 
     The steps at which the magnets M 1 -M 4  are mounted to the magnet assembly  31  will be described. 
     As shown in FIG. 3, the magnets M 1 -M 4  are fitted into the magnet holders MH 1 -MH 4  of the magnet assembly  31  such that the N-poles of the magnets M 1 -M 4  are in intimate contact with the bottom of the magnet holders MH 1 -MH 4 . Thus, the magnets M 1 -M 4  will not drop from the magnet assembly  31  even if the magnet assembly  31  is flipped over. 
     The procedure of fitting the magnet assembly  31  into the recess  30   d  will be described with reference to FIG.  1 . 
     The magnet assembly  31  is first held and oriented such that the magnet holders MH 1 -MH 4  directly face the recess  30   d . Then, the magnet assembly  31  is fitted into the recess with projections  31   a  fitting into corresponding receiving portions  30   e . Upon fitting the magnet assembly  31  into the recess  30   d , the S-poles (FIG. 3) are brought into contact with the bottom surface of the recess  30   d . In this manner, the magnets M 1 -M 4  are accurately placed in position. 
     As shown in FIGS. 2A-2C and  5 , the Hall effect element assembly  4  includes the Hall effect elements H 1 -H 4 , a circuit board  40 , board holder  41 , and spring  42 . As shown in FIG. 5, a recess  41   a  formed in the board holder  41  receives the circuit board  40  therein. A side of the circuit board  40  on which the Hall effect elements are mounted faces the board holder  41 . The board holder  41  is suspended from the lid  2  by the spring  42 . 
     The circuit board  40  has four holders in which corresponding Hall effect elements H 1 -H 4  are accommodated. The Hall effect elements H 1 -H 4  are received in corresponding holders formed on the circuit board  40  such that when the lid  2  is closed completely, the Hall effect elements are in alignment with corresponding magnets M 1 -M 4  on the toner cartridge side. 
     Each Hall effect element Hi (i=1, 2, 3, 4) faces a corresponding magnet Mi (i=1, 2, 3, 4) with a gap G=2.6 mm between the magnet Mi and the Hall effect element Hi. The center-to-center distance L between adjacent Hall effect elements H 1 -H 4  is 7.1 mm and the center-to-center distance L between adjacent magnets M 1 -M 4  is 7.1 mm accordingly. The diameter of the magnets M 1 -M 4  is 3 mm and the end-to-end distance between adjacent magnets M 1 -M 4  is 4.1 mm accordingly. 
     The Hall effect element Hi detects the magnetic flux of a corresponding magnet Mi to become ON when the lid  2  is closed, and does not detect the magnetic flux of the magnet Mi to become OFF when the lid  2  is opened. For example, if the magnet Mi is absent, then a corresponding Hall effect element Hi does not become ON. When the Hall effect element Hi becomes ON, the voltage output of the Hall effect element Hi exceeds a predetermined reference value. When the Hall effect element Hi becomes OFF, the voltage output decreases below the predetermined reference value. 
     The ID cartridge  5  is a cartridge having an image drum (ID). Light illuminates the surface of the image drum to form an electrostatic latent image thereon. The electrostatic latent image is then developed with toner and is subsequently transferred to a print medium. As shown in FIG. 4, the ID cartridge  5  includes a toner cartridge receiving section  52  and a lever receiving section  53 . The toner cartridge receiving section  52  receives the toner cartridge  3  therein. The lever receiving section  53  receives the lever  30   b  of the rotary cap  30  of the toner cartridge  3 . The toner cartridge receiving section  52  extends in a direction parallel to the longitudinal direction of the ID cartridge  5 . The lever receiving section  53  is located at a longitudinal end of a chassis  50 . 
     &lt;Attaching the toner cartridge into the printer&gt; 
     FIG. 4 is a perspective view illustrating when the toner cartridge is attached to an image drum cartridge of the printer of FIG.  2 . 
     FIG. 5 is a partial cross-sectional view of the printer when the lid has been closed after the toner cartridge and ID cartridge are attached to the printer. 
     The procedure for attaching the toner cartridge  3  into the printer  1  will be described with reference to FIGS. 2,  4  and  5 . 
     The lid  2  is first opened. As shown in FIG. 4, the toner cartridge  3  is lowered in a direction shown by arrow A until the toner cartridge  3  is loaded into the toner cartridge receiving section  52  of the ID cartridge  5  which has been placed into the printer  1 . 
     Then, the rotary cap  30  of the toner cartridge  3  is rotated in a direction shown by arrow B to a predetermined position. In other words, the lever  30   b  is rotated until the lever  30   b  is received in the lever receiving section  53  and the stopper  30   c  abuts its mating part (not shown) formed on the toner cartridge receiving section  52 . 
     As shown in FIG. 5, when the lid  2  is rotated about a shaft  2   a  in a direction shown by arrow C, the bottom of the board holder  41  abuts the magnet assembly  31  of the lever  30   b  and the spring  42  urges the board holder  41  in the direction shown by arrow A. As a result, the lever  30   b  is further rotated slightly in the direction shown by arrow B. Therefore, even if the lever  30   b  has not been fully rotated when the user rotated the lever  30   b , completely closing the lid  2  ensures that the toner lever  30   b  is rotated to a predetermined position. 
     The lid  2  is thus completely closed. This completes the mounting of the toner cartridge  3  into the ID cartridge. When the lid  2  has been completely closed, the printer  1  performs an operation for identifying the type (content) of the toner cartridge  3 . 
     &lt;Gaps G and distance L&gt; 
     The gap G between the magnets M 1 -M 4  and the Hall effect elements H 1 -H 4  and the center-to-center distance L between adjacent Hall effect elements will be described. 
     The Hall effect element Hi should detect the magnetic flux radiated only from a corresponding magnet Mi, thereby detecting the presence and absence of the magnet Mi. Therefore, if a corresponding magnet Mi is absent, the Hall effect element Hi should not detect the magnetic flux from any other magnets. For this purpose, the size of the magnet and the center-to-center distance between adjacent magnets are carefully selected such that the Hall effect element Hi is not sensitive to the magnetic flux from any magnets that do not corresponding to the Hall effect element Hi. In the present invention, the diameter of the magnets is 3 mm and the center-to-center distance L between adjacent magnets is 7.1 mm. The center-to-center distance between adjacent Hall effect elements is 7.1. 
     The gap G between a magnet and a corresponding Hall effect element determines a minimum value of the distance L at which a Hall effect element is still not turned ON by a magnet not corresponding to it. If the minimum value of distance L is to be as small as possible, then the gap G should be made as small as possible. The distances L were measured for various values of G, thereby experimentally determining the minimum value of the distance L. Optimum distance L was L=7.1 mm and optimum gap G was 2.6 mm. 
     &lt;Toner cartridge-identifying operation&gt; 
     The toner cartridge identifying operation will be described. 
     FIG. 6 illustrates the presence and absence of magnets M 1 -M 4  and the On and OFF states of corresponding Hall effect elements. FIG. 6 shows a case when magnets M 1  and M 3  are present. 
     FIG. 7 illustrates all possible combinations of the presence and absence of the magnets M 1 -M 4 . 
     Sixteen combinations are possible by combining the presence and absence of a total of four magnets M 1 -M 4  in the magnet holders. Thus, a total of 16 toner cartridges  3  of the same appearance but with different contents can be expressed or identified. A toner cartridge  3  having no magnet is not manufactured. 
     The printer  1  stores “magnet data” indicative of the type (content) of the toner cartridge  3  that the printer  1  can accept. The magnet data describes a combination of magnets M 1 -M 4 . A plurality of items of the magnet data can be stored in the printer  1 . The printer  1  determines whether a combination of the outputs of the Hall effect elements H 1 -H 4  matches the stored magnet data, thereby identifying the content of the toner cartridge  3 . 
     For example, as shown in FIG. 6, when a toner cartridge  3  has only magnets M 1  and M 3 , the Hall effect elements H 1  and H 3  become ON and Hall effect elements H 2  and H 4  remain OFF. If the combination of the outputs of the Hall effect elements H 1  and H 3  matches with one of the items of magnet data stored in the printer  1 , then the printer  1  determines that the toner cartridge  3  is an acceptable one. 
     If the combination of the ON and OFF states of the Hall effect elements H 1  and H 3  do not match the stored magnet data, then the printer  1  determines that the loaded toner cartridge  3  is not an acceptable one. Then, the printer  1  indicates to the user by way of a display or a voice message that the attached toner cartridge is not accepted, and then stops the entire operation. 
     Second Embodiment 
     A second embodiment differs from the first embodiment in that the magnets M 1 -M 4  are mounted to the magnet assembly  31  in a different way. The rest of the construction is the same as that of the first embodiment. In the second embodiment, the magnetic elements that have not been magnetized yet are fitted into the magnet holders of the magnet assembly  31  made of a non-magnetic material, and then the entire assembly of the magnet assembly  31  is subjected to magnetization so that the magnetic elements are magnetized into the magnets M 1 -M 4 . 
     FIGS. 8A and 8B illustrate the steps for mounting the magnets M 1 -M 4  to the magnet assembly  31 . 
     FIG. 9 illustrates the magnetizing process in which the magnetic elements Nm 1 -Nm 4  fitted into the magnet holders of the magnet assembly  31  are magnetized. 
     As shown in FIG. 8A, the magnetic elements Nm 1 -Nm 4  which have not been magnetized yet are fitted into the magnet holders of the magnet assembly  31 . 
     The magnet assembly  31  is placed in a magnetizing field so that the magnetic elements Nm 1 -Nm 4  are magnetized to become magnets M 1 -M 4 . Several tens of magnet assembly  71   s    31  having magnetic elements Nm which have not been magnetized yet are stacked on an electromagnet table  100   a . Then, the magnetizing apparatus  101  is powered on, so that a magnetizing field is established between the electromagnet tables  100   a  and  100   b . Thus, all of the magnetic elements Nm mounted on the several tens of magnet assemblies  31  are simultaneously magnetized to the same polarity (the ends of the magnetic elements in contact with the bottom of the magnet assemblies  31  are magnetized to N-pole). 
     In the first embodiment, the magnets M 1 -M 4  are mounted to the magnet assembly  31 . Thus, the magnets attract one another, making assembly operation somewhat difficult. In the second embodiment, when the magnetic elements are assembled to the magnet assembly  31 , they have not been magnetized yet. This facilitates the assembly operation of the magnetic elements to the magnet assembly  31 . 
     In the first embodiment, the magnets M 1 -M 4  must be assembled so that their magnetic polarities are properly oriented. Thus, there is a chance of the magnets M 1 -M 4  being mounted with improper orientations. The second embodiment not only eliminates the need for orienting the magnets M 1 -M 4  in a specific direction but prevents the magnets M 1 -M 4  from being mounted with wrong orientations. 
     Third embodiment 
     FIG. 10A is a perspective view of a printer  6  according to a third embodiment. FIG. 10B is a fragmentary view of a lid  2  and the toner cartridge  3 . 
     FIG. 11 is a partial cross-sectional side view of the printer  6  of FIG. 10A 
     Elements of FIGS. 10A and 10B and FIG. 11 similar to those of the first embodiment have been given the same references. 
     The ID cartridge  7  and the toner cartridge  3  are loaded into the main body of the printer  6 . The ID cartridge  7  has magnets ME 1 -ME 4  and the toner cartridge  3  has magnets MT 1 -MT 4 . The magnets ME 1 -ME 4  and MT 1 -MT 4  are the same as the magnets M 1 -M 4  of the first embodiment. The lid  2  of the printer  6  is provided with a Hall effect element assembly  8 , which includes Hall effect elements HE 1 -HE 4  that detect the fluxes of the magnets ME 1 -ME 4  and Hall effect elements HT 1 -HT 4  that detect the fluxes of the magnets MT 1 -MT 4 . The printer  6  determines based on the outputs (ON and OFF states) of the Hall effect elements HE 1 -HE 4  whether an ID cartridge  7  loaded into the printer  6  is an appropriate one, and on the outputs (ON and OFF states) of the Hall effect elements HT 1 -HT 4  whether a toner cartridge  3  attached to the ID cartridge  7  is an acceptable one. 
     FIG. 12A is a perspective view of the ID cartridge  7  with a partial exploded view. 
     FIG. 12B is a perspective view of a magnet assembly  71 . 
     The ID cartridge  7  has an image drum (ID) mounted therein. As shown in FIG. 12A, the ID cartridge  7  includes a chassis  70 , a magnet assembly  71 , magnets ME 1 -ME 4 , a toner cartridge receiving section  72 , and a lever receiving section  73 . The toner cartridge receiving section  72  and lever receiving section  73  are of the same structure as the toner cartridge receiving section  52  and lever receiving section  53  of FIG. 4, respectively. 
     The chassis  70  is provided with a magnet receiving section  70   d . The magnet assembly  71  is provided with magnet holders that receive magnets ME 1 -ME 4  therein. The magnet assembly  71  is securely mounted to the bottom surface of the magnet receiving section  70   d  with projections  71   a  fitting into the receiving portions  70   e . The magnet assembly  71  is provided with four magnets ME 1 -ME 4  (FIG. 10B) so that a plurality of different types of the ID cartridge  7  can be expressed or identified. The magnet assembly  71  is of the same structure as the magnet assembly  31  of the first embodiment. The magnet assembly  71  and the chassis  70  are made of a non-magnetic material, for example, polystyrene. 
     The magnets ME 1 -ME 4  are sandwiched between the magnet holders of the lid  2  and the bottom surface of the magnet receiving section  70   d . Referring back to FIG. 10B, all of the four magnets are received in corresponding magnet holders by way of example. The arrangement and number of magnets can be selected according to the content or type of the ID cartridge  7 . The magnets ME 1 -ME 4  are mounted to the magnet assembly  71  in the same manner as the first and the second embodiments where the magnets M 1 -M 4  are mounted to the magnet assembly  31  of the toner cartridge  3 . 
     FIG. 11 is a partial cross-sectional side view of the printer  6  of FIG. 10A after the ID cartridge  7  and the toner cartridge  3  have been mounted and then the lid  2  has been closed. The hatched portion of FIG. 11 shows the cross sectional view taken along lines A—A of FIG.  12 B. 
     As shown in FIGS. 10B and 11, the Hall effect element assembly  8  includes Hall effect elements HE 1 -HE 4 , Hall effect elements HT 1 -HT 4 , circuit board  80 , board holder  81 , and springs  82 . The Hall effect elements HE 1 -HE 4  and HT 1 -HT 4  are aligned with the magnet holders MEH 1 -MEH 4  of the ID cartridge  7  and magnet holders MTH 1 -MTH 4  of the toner cartridge  3 , respectively. The Hall effect elements HE 1 -HE 4  and HT 1 -HT 4  are mounted on the circuit board  80 . The Hall effect elements HE 1 -HE 4  and HT 1 -HT 4  are the same as the Hall effect elements H 1 -H 4  of the first embodiment. As shown in FIG. 11, the board receiving section  81 a formed on the top of the board holder  81  receives the circuit board  80  therein, the Hall effect element side of the circuit board  80  facing down. The board holder  81  is suspended from the lid  2  by the springs  82 . 
     The circuit board  80  has four Hall effect elements HE 1 -HE 4  and four Hall effect elements HT 1 -HT 4  mounted thereon. The Hall effect elements HE 1 -HE 4  and HT 1 -HT 4  correspond to the four magnet holders MEH and the four magnet holders MTH, respectively. 
     The Hall effect elements HE-HE 4  are fixed at locations such that when the lid  2  is closed, the Hall effect element HEi (i=1, 2, 3, 4) faces the magnet MEi (i=1, 2, 3, 4). The gap G between the Hall effect element HEi and the magnet MEi is 2.6 mm. Likewise, just as in the first embodiment, the Hall effect elements HT 1 -HT 4  are fixed at locations such that when the lid  2  is closed, the Hall effect element HTi (i=1, 2, 3, 4) faces the magnet MTi (i=1, 2, 3, 4). The gap G between the Hall effect element HTi and the magnet MTi is 2.6 mm. 
     FIG. 12C illustrates the distance between adjacent Hall effect elements ME 1 -ME 4 . 
     The diameter of the magnets is 3 mm and the center-to-center distance between adjacent magnets is 7.1 mm. Thus, the end-to-end distance between adjacent magnets is 4.1 mm. The center-to-center distance L between adjacent Hall effect elements HE mounted on the circuit board  80  is 7.1 mm. Likewise, the center-to-center distance L between adjacent Hall effect elements HT is also 7.1 mm. Therefore, the center-to-center distance L between adjacent magnet holders MEH and MTH is also 7.1 mm. 
     As shown in FIG. 11, when the lid  2  is closed, the bottom of the board holder  81  abuts the magnet assembly  71  mounted in the chassis  70  so that the magnet assembly  31  mounted in the rotary cap  30  is urged in a direction shown by arrow A by the springs  82 . Just as in the first embodiment, the board holder  81  engages the lever  30   b  of the rotary cap  30  such that the rotary cap  30  is placed in position. When the lever  30   b  has been placed in position, the magnet assembly  71  and the magnet assembly  31  are of the same height. Then, when the lid  2  has been closed, the board holder  81  is urged by the springs  82  to abut the top surface of the magnet assemblies  71  and  31 . Thus, the gaps between the Hall effect elements HE 1 -HE 4  and magnets ME 1 -ME 4  are the same as those between the Hall effect elements HT 1 -MT 4  and the magnets MT 1 -MT 4 . 
     FIG. 13 illustrates, by way of example, the On and OFF states of the Hall effect elements HE 1 -HE 4  and HT 1 -HT 4  and the presence and absence of the magnets ME 1 -ME 4  and MT 1 -MT 4 . In Fig. the magnets ME 1  and ME 3  are present and therefore the Hall effect elements HE 1  and E 3  are ON. Likewise, the magnets MT 1  and MT 3  are present and therefore the Hall effect elements HT 1  and HT 4  are ON. 
     A cartridge-identifying operation for identifying a cartridge attached into the printer  6 . 
     The cartridge-identifying operation is carried out when the lid  2  is closed and when the printer  6  is powered on. Therefore, every time the ID cartridge  7  or toner cartridge  3  is replaced, the cartridge-identifying operation is performed. 
     FIG. 14 illustrates possible combinations of the presence and absence of ME 1 -ME 4  and MT 1 -MT 4 . 
     A total of sixteen different combinations can be made by combining the presence of the magnets ME 1 -ME 4  in the magnet holders MEH 1 -MEH 4  with the absence of magnets NE 1 -ME 4  in the magnet holders MEH 1 -MEH 4 . An ID cartridge  7  having all magnet holders MEH 1 -MEH 4  empty of magnets is not to be manufactured. Thus, according to the type or the content therein, 15 different ID cartridges  7  of the same appearance can be identified. Likewise, a total of sixteen different combinations can be made by combining the presence and absence of the magnets MT 1 -MT 4  in the magnet holders MTH 1 -MTH 4 . A toner cartridge  3  having all magnet holders MTH 1 -MTH 4  empty of magnets is not to be manufactured. Thus, according to the type or the content therein, 15 different toner cartridges  3  of the same appearance can be identified. 
     The printer  6  stores the magnet data for ID cartridge (i.e., combinations of the magnet holders in which magnets are present) and the magnet data for the toner cartridge (i.e., combinations of the magnet holders in which magnets are present). The printer  6  determines whether the stored magnet data for ID cartridge  7  matches with a combination of the ON and OFF states of the Hall effect elements HE 1 -HE 4 , thereby identifying the content of the ID cartridge  7  attached to the printer  6 . The printer  6  also determines whether the magnet data for toner cartridge  3  matches with a combination of the ON and OFF states of the Hall effect elements HT 1 -HT 4 , thereby identifying the content of the toner cartridge  3  attached to the printer  6 . If the printer  6  determines that the ID cartridge  7  or toner cartridge  3  is not an acceptable one, a display or voice message indicates to the operator that the inserted ID cartridge  7  or toner cartridge  3  is not acceptable, and the printer  6  stops. 
     Fourth Embodiment 
     &lt;Construction&gt; 
     FIG. 15 is a partial exploded perspective view of a printer  9  according to a fourth embodiment. 
     FIG. 16 is a partial cross-sectional view when the toner cartridge  3  and ID cartridge  10  have been attached to the printer  9  and the lid  2  has been closed. Elements of FIGS. 15 and 16 similar to those of the first embodiment have been given the same references. 
     Referring to FIGS. 15 and 16, the ID cartridge  10  is equipped with Hall effect elements HI that detect the magnetic fluxes of the North poles of the magnets M. The Hall effect elements and magnets are arranged in the same manner as the first embodiment. The toner cartridge  3  has magnets M with the N poles oriented to the Hall effect elements HI and the S poles oriented to the lid  2 . The lid  2  has Hall effect element assembly  4  incorporating Hall effect elements H that detect the fluxes of S poles of the magnets M. The Hall effect elements HI and H are of the same type. The printer  9  checks the ON and OFF states of the Hall effect elements H to determine whether the content of the toner cartridge  3  is acceptable. The printer  9  also checks the ON and OFF states of the Hall effect elements HI and H to determine whether the content of the ID cartridge  10  is acceptable. 
     The ID cartridge  10  includes a chassis  100 , a toner cartridge receiving section  102 , a lever receiving section  103 , Hall effect elements HI, a circuit board  104  on which the Hall effect elements HI are mounted, and a circuit board receiving section  105  that accommodates the circuit board  104 . The chassis  100  and toner cartridge receiving section  102  are of the same construction as the chassis  50  and toner cartridge receiving section  52  of FIG.  4 . 
     The chassis  100  has the lever receiving section  103  at one end thereof. The lever receiving section  103  accommodates the lever  30   b  having magnets M mounted therein. The lever receiving section  103  has a circuit board receiving section  105  into which the circuit board  104  is fitted with Hall effect elements side facing down. 
     The circuit board  104  has four Hall effect elements HI 1 -HI 4  each of which faces a corresponding one of four magnet holders of the lever  30   b . The circuit board  40  has four Hall effect elements H 1 -H 4  each of which faces a corresponding one of four magnet holders of the lever  30   b . Thus, a Hall effect element HIi (i=1, 2, 3, and 4) faces the N-pole of a magnet Mi (i=1, 2, 3, and 4) held in a magnet holder MHi while the Hall effect element Hi faces the S-pole of the magnet Mi. 
     When the lid  2  has been closed, the Hall effect elements HIi of the ID cartridge  10  faces the magnet Mi such that the gap GI between the magnet Mi and the Hall effect elements HIi is 2.6 mm, i.e., the same as the gap G between the Hall effect elements Hi and the magnet Mi in the first embodiment. The center-to-center distance between adjacent Hall effect elements HI mounted on the circuit board  104  is 7.1 mm, i.e., the same as the center-to-center distance between adjacent magnet holders MH on the magnet assembly  31 . 
     &lt;Operation for identifying toner cartridge and ID cartridge&gt; 
     The toner cartridge/ID cartridge identifying operation will now be described. This operation is activated when the printer  9  is powered up and when the lid  2  is closed. In other words, every time the ID cartridge  10  or the toner cartridge  3  is replaced, the operation is performed. 
     Just as in the first embodiment, the printer  9  determines whether the content of the toner cartridge  3  is acceptable one. That is, the printer  9  stores a predetermined item of “magnet data” therein and determines whether the magnet data matches with the combination of the ON and OFF states of the Hall effects H 1 -H 4 . If it is determined that the attached toner cartridge  3  is not accepted, then, a display or voice message indicates to the operator that the inserted toner cartridge  3  is not acceptable, and the printer  9  stops. 
     Then, the printer  9  determines whether the combination of the ON and OFF states of the Hall effect elements HI 1 -HI 4  matches with the combination of the ON and OFF states of the Hall effect elements H 1 -H 4 . If they match with each other, then it is determined that the attached ID cartridge is an acceptable one. If they do not match with each other, then, a display or voice message indicates to the operator that the inserted ID cartridge is not acceptable, and the printer  9  stops. In the fourth embodiment, an ID cartridge having no Hall effects elements HI or having improper gaps GI between the Hall effect elements HI and the magnets M is determined as an unacceptable one. 
     The Hall effect elements H mounted on the lid  2  may be omitted, in which case, a check is made to determine whether a combination of the ON and OFF states of the Hall effect elements HI 1 -HI 4  matches with the magnet data stored in the printer  9 . If they match with each other, then it is determined that the contents or types of the toner cartridge  3  and the ID cartridge are acceptable. 
     Fifth Embodiment 
     A fifth embodiment differs from the first embodiment in that the magnets M mounted on the toner cartridge  3  are used to detect the opening and closing of the lid  2 . The rest of the construction is the same as the first embodiment. In order to detect the opening and closing of the lid  2 , a magnet M and a corresponding Hall effect element H are required. Conventional printers use a micro switch and a lever for driving the micro switch. This mechanical switch did not provide good detection accuracy. 
     In the fifth embodiment, if any one of the Hall effect elements H 1 -H 4  is in the ON state, then the printer  1  determines that the lid  2  is closed. If all of the Hall effect elements H 1 -H 4  are in the OFF state, then the printer  1  determines that the lid  2  is open, and the printer  9  stops. 
     While the first to fifth embodiments have been described with respect to the toner cartridge and the ID cartridge for a printer, the present invention may be applicable to ink cartridges and ink ribbon cartridges for facsimile machines and copying machines. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art intended to be included within the scope of the following claims.