Abstract:
A sheet size detecting device is provided with the following a tray in which sheets are stored, guides that can be adjusted in position in accordance with the size of sheets stored in the tray, and bit generation sections that are moved in synchronism with movement of the guides. The device detects bits based on the movement of the bit generation sections, and the number of bits detectable is larger than the number of bit generation sections by at least one. The device detects the size of sheets stored in the tray on the basis of the correspondence between the combination of detected bits and the sizes of sheets which can be stored in the tray.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application is a continuation of U.S. application Ser. No. 10/383,677, filed Mar. 10, 2003, the entire contents of which are incorporated herein by reference.  
         [0002]     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2002-097552, filed Mar. 29, 2002, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0003]     1. Field of the Invention  
         [0004]     The present invention relates to a sheet size detecting device for detecting the size of sheets stored in a position.  
         [0005]     2. Description of the Related Art  
         [0006]     Copying machines, printers or facsimile machines have a function of detecting the size of sheets stored in a predetermined position. The sheet size detection is realized by optical sensors that are selected or used in accordance with the size of sheets. The sensors are made to detect a sheet, for example when a platen cover is closed.  
         [0007]     Jpn. Pat. Appln. KOKAI Publication No. 6-64781 discloses a technology wherein eight sheet sizes are detected by use of three sensors. According to this publication, the sheet sizes are detected by providing guides that can be adjusted in position in accordance with a size of a sheet, providing three code plates that are movable in synchronism with the guides, and arranging three sensors that detect the code plates, respectively. When sheets are stored in a tray and the guides are moved in accordance with the sheet size, a check is made to see whether or not the three sensors detect the corresponding code plates, and the sheet size is detected based on this check. To be more specific, the sheet size detection is performed as follows. For example, when the code plates are adjusted in position to increase the size from “size 1” to “size 8” in turn, a check is made to see whether the sensors detect the sheets. The detected states of the sensors are determined by comparing the detection signals with eight bit combination patterns, which are determined beforehand and correspond to different bit information of different sheet sizes.  
         [0008]     Since the sheet size detecting device employs sensors in accordance with the number of sheet types, a large number of sensors are required. For example, if the sheet size detecting device detects eight types of sheets, eight sensors are required. Due to the necessity of using a large number of sensors, the sheet size detecting device is inevitably large in size and costly.  
         [0009]     In the sheet size detecting method of Jpn. Pat. Appln. KOKAI Publication No. 6-64781, three code plates and three sensors are required for detecting eight sheet sizes. That is, the bit generation means and the bit detection means must be equal in number.  
       BRIEF SUMMARY OF THE INVENTION  
       [0010]     Accordingly, an object of the present invention is to provide a sheet size detecting device which can detect sheet sizes by means of a compact structure, and which can be provided at low cost.  
         [0011]     A sheet size detecting device according to one aspect of the present invention comprises: a tray in which sheets are stored; guides that can be adjusted in position in accordance with the size of sheets stored in the tray; and bit generation sections that are moved in synchronism with movement of the guides. The device detects bits based on the movement of the bit generation sections, and the number of bits detectable is larger than the number of bit generation sections by at least one. The device detects the size of sheets stored in the tray based on the correspondence between the combination of detected bits and the sizes of sheets that can be stored in the tray.  
         [0012]     Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0013]     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.  
         [0014]      FIG. 1  shows the outward appearance of a tray according to one embodiment of the present invention, as well as part of the internal structure of the tray.  
         [0015]      FIG. 2  shows a sheet size detecting mechanism.  
         [0016]      FIG. 3  is a schematic diagram showing a cross section of a bit detecting mechanism.  
         [0017]      FIG. 4  illustrates how sheet sizes are detected.  
         [0018]      FIG. 5  is a schematic diagram showing a control block of a sheet size detecting device.  
         [0019]      FIG. 6  is a table illustrating the correspondence between detected bit patterns and sheet sizes.  
         [0020]      FIG. 7  is a schematic diagram showing how a sheet size is detected according to the second embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     One embodiment of the present invention will now be described with reference to the accompanying drawings. In the embodiment, a sheet size detecting device  2  is provided for the manual insertion tray  11  of a copying machine  1  shown in  FIG. 5 .  
         [heading-0022]     (First Embodiment)  
         [0023]      FIG. 1  shows the outward appearance of the manual insertion tray  11  as well as part of the internal structure of the tray  11 . The tray  11  has two guides  12  and  13  each having a substantially “L”-shaped cross section. The guides  12  and  13  are movable in the longitudinal direction of the tray  11  in accordance with the size of sheets to be used. Each of the L-shaped guides is made up of two plates, one plate being parallel to the manual insertion tray  11 , and the other plate being perpendicular thereto. Sheets are stored between the plates that are perpendicular to the manual insertion tray  11 .  
         [0024]     Guide  12  is integrally assembled with a rack gear  14 . The rack gear  14  is in mesh with a pinion gear  16  which is rotatable around an axis perpendicular to the moving direction of the guide  12 . Likewise, guide  13  is integrally assembled with a rack gear  15 . This rack gear  15  is also in mesh with the pinion gear  16  and extends in parallel to the rack gear  14  described above. With this structure, when one of the guides  12  and  13  is moved in accordance with a sheet size, the other guide move in the opposite direction simultaneously. Therefore, the center of the sheets is always at the same position without reference to the sizes of the sheets, i.e., without reference to the adjustment of guides  12  and  13 .  
         [0025]     Sheets of eight sizes “A” to “H” can be stored in the manual insertion tray  11 . The sheet size increases from size “A” to size “H” in this order.  
         [0026]      FIG. 2  shows a mechanism for detecting a sheet size when sheets are stored in the manual insertion tray  11  and the guides are adjusted in accordance with the size of the sheets. It should be noted that  FIG. 2  shows the sides of the pinion gear  16 , rack gear  14  and rack gear  15  that are opposite to the sides shown in  FIG. 1 . In other words, the pinion gear  16 , rack gear  14  and rack gear  15  shown in  FIG. 1  are depicted upside down in  FIG. 2 . The plate of guide  12  that is parallel to the manual insertion tray  11  is fixed to one end of rack gear  14  by means of bolts  17 , and the plate of guide  13  that is parallel to the manual insertion tray  11  is fixed to one end of rack gear  15  by means of bolts  18 . With this structure, guides  12  and  13  are integrally assembled with rack gears  14  and  15 , respectively. The rack gears  14  and  15  are opposed to each other and in mesh with the pinion gear  16  located therebetween.  
         [0027]     The rack gear  15  has bit generating sections  19  and  20  to determine the guide positions. The bit generating section  19  has a rectangular projected portion extending in the moving direction of the guide  13 . A depressed portion (a hollow section)  21  is located at the predetermined position of the projected portion. Likewise, the bit generating section  20  has a rectangular projected portion extending in the moving direction of the guide  13 .  
         [0028]     Electric switches made up of stationary metal terminals and conductive elastic members and serving as bit detecting sections are located at positions to which the bit generating sections  19  and  20  of the rack gear  15  are movable. As shown in  FIG. 2 , the stationary metal terminals  22 ,  23  and  24  are prevented from moving together with the rack gear  15 . To be more specific, they are fixed inside the manual insertion tray  11 . They are supported by means of support members, for example. Two ( 22 ,  23 ) of the stationary metal terminals are provided at positions to which bit generating section  19  is movable, and the remaining one ( 24 ) is provided at a position to which bit generating section  20  is movable.  
         [0029]     The elastic conductive members  25 ,  26  and  27  are located between the stationary metal terminals  22 ,  23  and  24  and the moving tracks of the bit generating sections  19  and  20 . One-end portions of the conductive elastic members  25 ,  26  and  27  are secured inside the manual insertion tray  11 . When the bit generating sections  19  and  20  move and the projected portions come to predetermined positions, one end of conductive elastic member  25  comes into contact with stationary metal terminal  22 . A bit is detectable in this electrically conductive state. Therefore, the conductive elastic member and the stationary metal terminal jointly function as an electric switch. Bit detection signals from the three electric switches are supplied to ports X, Y and Z, respectively, and these ports are formed in the sheet size detecting section  3  that is provided for the sheet size detecting device  2 , as shown in  FIG. 5 .  
         [0030]      FIG. 3  is a schematic diagram showing a cross section of a mechanism that is configured to detect a bit when the electric switch is turned on.  
         [0031]     The bit generating section  19 , which is integral with the rack gear  15 , moves in the direction indicated by the arrow in  FIG. 3 , in synchronism with the movement of the guide  13 . The stationary metal terminal  22  and the conductive elastic member  25  are located at positions toward which the bit generating section  19  moves.  
         [0032]     The conductive elastic member  25  has a cross section substantially in the shape of “S.” When the bit generating section  19  moves, its projected portion raises the concave portion  28  of the conductive elastic member  25  (i.e., the concave portion  28  is moved in the upward direction as viewed in  FIG. 3 ). When the concave portion  28  of the conductive elastic member  25  is raised, the convex portion  29  of the conductive elastic member  25  is raised as well and brought into contact with the stationary metal terminal  22 . When the conductive elastic member  25  and the stationary metal terminal  22  are in contact with each other, a current is allowed to flow, and the electric switch  30  detects a bit.  
         [0033]     When the rack gear  15  moves further, the depressed portion of the bit generating section  19  comes to the position of the concave portion  28  of the conductive elastic member  25 . At this time, the conductive elastic member  25  returns to its original position because of the elasticity thereof. Since the conductive elastic member  25  is separated from the stationary metal terminal  22 , the electric switch  30  no longer detects a bit.  
         [0034]     As can be seen from the above, the movement of the bit generating section  19  provided with the depressed portion  21  at the predetermined position allows detection of four bit combination patterns, namely, the patterns determined by whether or not electric switch  30  (made up of stationary metal terminal  22  and conductive elastic member  25 ) detects a bit and by whether or not electric switch  31  (made up of stationary metal terminal  23  and conductive elastic member  26 ) detects a bit. In addition, the movement of the bit generating section  20  allows detection of two bit combination patterns, namely, the patterns determined by whether or not electric switch  32  (made up of stationary metal terminal  24  and conductive elastic member  27 ) detects a bit. Hence, the manual insertion tray  11  can detect eight sheet sizes.  
         [0035]      FIG. 4  illustrates how the sheet sizes are detected based on bits detected by the electric switches  30 ,  31  and  32 .  
         [0036]     In  FIG. 4 , the numbers within the thick-line frames indicate bit information which the electric switches  30 ,  31  and  32  output when the guides  12  and  13  are moved in accordance with the sheets of sizes A to H and the rack gear  15  moves accordingly. The bit detected by electric switch  30  is output to port X, the bit detected by electric switch  31  is output to port Y, and the bit detected by electric switch  32  is output to port Z.  
         [0037]     When the guides  12  and  13  are adjusted to the positions of size A (in which case, sheets have the narrowest width), “0”, “0” and “1” are output to ports X, Y and Z. The bit information detected by the electric switches  30 ,  31  and  32  changes each time sheets of a different size are used. The bits output to ports X, Y and Z are “0,1,1” in the case of size B, “0,1,0” in the case of size C, “1,0,1” in the case of size D, “1,1,1” in the case of size E, “1,1,0” in the case of size F, “1,0,0” in the case of size G, and “0,0,0” in the case of size H.  
         [0038]     As described above, when the guides  12  and  13  adjusted in accordance with the sizes of sheets, the electric switches  30 ,  31  and  32  output eight kinds of bit information dependent on the sheet sizes. As shown in  FIG. 6 , a storage section  4  electrically connected to the sheet size detecting section  3  is made to store eight bit combination patterns corresponding to sheet sizes beforehand. Each time the sheet size detecting section  3  detects a sheet, the combinations of the bits output from the electric switches  30 ,  31  and  32  is compared with the bit combinations patterns stored in the storage section  4 , thereby detecting the size of the sheet.  
         [0039]     In the present embodiment, the bit generating section  19  provided with the projected portion and the depressed portion  21  located at the predetermined position, and the bit generating section  20  provided with the projected portion, are arranged in parallel to the rack gear  14  and are movable in the direction in which the guides are movable. The electric switches  30  and  31  are located at positions to which the bit generating section  19  is movable. Likewise, the electric switch  32  is located at a position to which the bit generating section  20  is movable. With this configuration, 3-bit information is obtained regarding the size of the sheets stored in the manual insertion tray  11 , and the 3-bit information can be compared with the bit combination patterns corresponding to the eight sheet sizes. Therefore, the controller of the copying machine  1  can detect eight sheet sizes.  
         [0040]     Unlike the prior art configuration, the present embodiment does not have to employ three bit generating sections. That is to say, the present embodiment uses two bit generating sections  19  and  20 , and detection of eight sheet sizes is enabled. Hence, the manual insertion tray  11  has a decreased width, and the sheet size detecting device is compact in size and does not occupy much space.  
         [0041]     The bit generating sections  19  and  20  are arranged in two rows. With this configuration, a product error, such as a phase shift between adjacent rows, is prevented, and yet the structure is simple. It is therefore possible to provide a sheet size detecting device which is fabricated with high precision and at low cost.  
         [0042]     In the first embodiment described above, the two bit generating sections  19  and  20  have projected and depressed portions, and these portions are detected by the electric switches  30 ,  31  and  32 . However, the present invention is not limited to this. For example, a bit generating section may be provided with a notch detectable by an electric switch.  
         [0043]     Furthermore, it is not necessary to employ an electric switch for bit detection. A sensor (e.g., a light sensor) may be arranged at a predetermined position, and the projected portion and the depressed portion or notch may be detected by checking whether light has passed or blocked.  
         [heading-0044]     (Second Embodiment)  
         [0045]     The second embodiment of the present invention will now be described. Structural elements that are similar or correspond to those of the first embodiment are denoted by the same reference numerals, and a detailed description of such structural elements will be omitted.  
         [0046]      FIG. 7  is a schematic diagram showing how a sheet size is detected according to the second embodiment of the present invention.  
         [0047]     In the manual insertion tray  11  of the first embodiment, the rack gear  15  is provided with the bit generating sections  19  and  20 . The manual insertion tray of the second embodiment does not employ this structure. In place of this structure, a pinion gear  16  rotatable on an axis of rotation is provided with circular bit generating sections  41  and  43 . Bit generating section  41  includes a projected portion extending in the rotating direction of the pinion gear  16 , and a depressed portion  42  formed at the predetermined position of the projected portion. Bit generating section  43  is provided radially inward of bit generating section  41  and has a depressed portion extending in the rotating direction of the pinion gear  16 .  
         [0048]     The projected portions of the bit generating sections  41  and  43  are covered with coatings that reflect light. Reflection type sensors  44  and  45  are provided for bit generating section  41 , and reflection type sensor  46  is provided for bit generating section  43 . When the reflection type sensors  44 ,  45  and  46  detect the projected portions of the bit generating sections  41  and  43 , they detect bits being generated.  
         [0049]     With this configuration, the bit generating sections  41  and  43  rotate together with the pinion gear  16 . The rotation of the bit generating section  41  allows detection of four bit combination patterns, namely, the patterns determined by whether or not reflection type sensor  44  detects a bit and by whether or not reflection type sensor  45  detects a bit. In addition, the rotation of the bit generating section  43  allows detection of two bit combination patterns, namely, the patterns determined by whether or not reflection type sensor  46  detects a bit. Hence, the manual insertion tray  11  of the second embodiment can detect eight sheet sizes, like the tray  11  of the first embodiment.  
         [0050]     Rack gears  14  and  15  engaging with the pinion gear  16  extend in parallel to each other. Therefore, the diameter of the pinion gear  16  is determined in such a manner that the circumference of the pinion gear  16  is equal to one half of the width required for detecting all sheet sizes. That is, the diameter of the pinion gear  16  is defined by (maximum of detectable sheet width)/2π.  
         [0051]     According to the second embodiment, 3-bit information is obtained regarding the size of the sheets stored in the manual insertion tray  11 , and that 3-bit information can be compared with predetermined bit combination patterns corresponding to the eight sheet sizes. Therefore, the controller of the copying machine can detect eight sheet sizes.  
         [0052]     As described above, three bit generating sections are not required, as in the prior art. Since the second embodiment can detect eight sheet sizes by use of only two bit generating sections  41  and  43 , and the diameter of the pinion gear is defined as (maximum of detectable sheet width)/2π, it is possible to provide a sheet size detecting device whose manual insertion tray is compact in size and does not occupy much space.  
         [0053]     The bit generating sections  19  and  20  are arranged in two concentric patterns. With this configuration, a product error, such as a phase shift between adjacent patterns, is prevented, and yet the structure is simple. It is therefore possible to provide a sheet size detecting device which is fabricated with high precision and at low cost.  
         [0054]     In the second embodiment as well, the two bit generating sections  41  and  43  may be provided with a notch detectable by a light sensor. Needless to say, the bit detecting section may be an electric switch, as in the first embodiment.  
         [0055]     The embodiments were described, referring to the case where the present invention is applied to the manual insertion tray  11  of a copying machine  1 . The present invention is in no way limited to this. For example, it is applicable to a sheet size detecting device provided at a predetermined position of a sheet feed cassette to detect the size of sheets stored therein.  
         [0056]     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.