Abstract:
A media thickness detector includes a driving force transmission part for removing vibration generated from a driving source. A sensing roller feeds media by receiving the driving force through the driving force transmission part. Sensing bearings are installed on bearing holders and rotate about a central shaft under an elastic force so that they are brought into close contact with the sensing roller. A damper member is connected to the central shaft at a position between the bearing holders and absorbs vibration generated in the central shaft. A thickness sensor detects the thickness of media passing between the sensing bearings and the sensing roller based on a rotating amount of the bearing holders.

Description:
[0001]     The present application claims, under 35 U.S.C. §119, the priority benefit of Korean Patent Application No. P2003-053541 filed Aug. 1, 2003 in the Republic of Korea, the entire contents of which are herein fully incorporated by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a media thickness detector, and more particularly, to a media thickness detector capable of detecting the thickness of media to be fed.  
         [0004]     2. Description of the Related Art  
         [0005]     A media thickness detector detects the thickness of media, such as bank notes, checks, tickets, certificates and paper. The reason for detecting the thickness of media is to ensure smooth operations of an apparatus by preventing a plurality of sheets of media from being fed together or by preventing inferior media from being fed. For example, such a media thickness detector is used in automatic teller machines, ticket-issuing machines, certificate-issuing machines, printers, facsimile machines, and the like.  
         [0006]     Methods of detecting the thickness of media include a method of detecting the thickness of media in which a roller comes into direct contact with media by means of a mechanical mechanism, a method of detecting the thickness of media using an optical sensor without bringing a mechanical mechanism into direct contact with media, and a combination thereof  
         [0007]      FIGS. 1 and 2  show a media thickness detector in accordance with the related art. Referring to these figures, a sensing roller  12  is installed on a rotational shaft  10  of which both ends are supported on a frame (not shown). The sensing roller  12  is disposed on a path along which media m travel. The sensing roller  12  is rotated by a driving belt  14  that is driven by a driving source. The driving belt  14  connects the driving source and the rotational shaft  10  to transmit power from the driving source to the rotational shaft  10 , thereby causing the sensing roller  12  to rotate. A timing belt is used for the driving belt  14 .  
         [0008]     A central shaft  16  of which both ends are supported on the flame is provided in the vicinity of the rotational shaft  10 . A bearing holder  18  is installed on the central shaft  16 . Return springs  19  are installed at both ends of the central shaft  16  provided with the bearing holder  18 . An end of each of the return springs  19  is connected to the bearing holding  18  at a point spaced from the central shaft  16  and the other end of the return spring  19  is connected to the frame, whereby the return spring imparts a restoring force in a specific direction. Therefore, the bearing holder  18  tends to always rotate in a specific direction.  
         [0009]     Sensing bearings  20  are provided at a side of the bearing holder  18 . As seen from  FIG. 2 , the two sensing bearings  20  are provided at both ends of the one side of the bearing holder  18 , respectively. The circumference of the sensing bearing  20  is set to be approximately a half of the traveling length of media m.  
         [0010]     The sensing bearings  20  are installed on the bearing holder  18  such that they can be freely rotated. The sensing bearings  20  tend to always move in a direction in which they are brought into close contact with the sensing roller  12 , because the bearing holder  18  is rotated toward the sensing roller  12  by means of the restoring force of the return springs  19 . The media m to have its thickness detected is fed between the sensing roller. 12  and the sensing bearings  20 .  
         [0011]     A thickness sensor  22  detects the thickness of media m by detecting a rotating amount of the bearing holder  18 . An example of the thickness sensor  22  includes a RVDT (Rotational Variable Differential Transformer) sensor.  
         [0012]     However, the aforementioned related art has the following problems.  
         [0013]     First, since the sensing roller  12  is rotated by receiving a driving force from the driving source through the driving belt  14 , vibration from the driving source is transmitted to the sensing roller  12  through the driving belt  14 . When vibration is transmitted from the driving source to the sensing roller  12 , there is a problem that the thickness of media m cannot be accurately measured, particularly when a mechanical mechanism is used for detecting the thickness.  
         [0014]     Further, each of the sensing bearings  20  must come into contact with the media. However, the two sensing bearings  20  are installed on a single bearing holder  18 . Therefore, the sensing bearings  20  cannot be brought into close contact with the sensing roller  12  with the same force when the bearing holder  18  is not accurately installed. In other words, if the bearing holder  18  is slightly tilted because of manufacturing tolerances, one sensing bearing  20  will bear against the media with a greater force than the other sensing media. Accordingly, there is also a problem in that the thickness of media m cannot be accurately detected.  
         [0015]     In addition, since the circumference or perimeter length of the sensing bearing  20  is set to be about a half of the traveling length of media m, the sensing bearing  20  is rotated twice while a sheet of media m travels between the sensing bearing and the sensing roller. Therefore, there is another problem in that the thickness detection capability is deteriorated since measuring errors that may be produced due to the tolerance of the sensing bearing  20  are accumulated.  
       SUMMARY OF THE INVENTION  
       [0016]     Accordingly, the present invention is conceived to solve the aforementioned problems in the prior art. An object of the present invention is to provide a media thickness detector wherein external vibration cannot be transmitted to components that come into direct contact with media.  
         [0017]     Another object of the present invention is to provide a media thickness detector wherein a sensing bearing is accurately contacted with a sensing roller.  
         [0018]     A further object of the present invention is to provide a media thickness detector wherein the rotation of a sensing bearing can be minimized while a sheet of media is fed past it.  
         [0019]     According to an aspect of the present invention for achieving the objects, there is provided a media thickness detector, comprising a driving force transmission which removes vibration generated from a driving source and transmits a driving force of the driving source. A sensing roller feeds media by receiving the driving force of the driving source through the driving force transmission part. Sensing bearings are installed on bearing holders rotating about a central shaft, such that an elastic force is exerted thereon in a direction in which they are brought into close contact with the sensing roller. A damper member is connected to the central shaft at a position between the bearing holders for absorbing vibration generated in the central shaft. A thickness sensor detects a thickness of the media passing between the sensing bearings and the sensing roller based on a rotating amount of the bearing holders with respect to the central shaft.  
         [0020]     The driving force transmission part may be a gear train driven by means of the driving source for providing the media feeding force.  
         [0021]     Preferably, a first gear of the gear train receives the driving force from the driving source through a belt.  
         [0022]     Preferably, both ends of the central shaft are supported on a frame on which connecting brackets in turn are installed between the bearing holders and the frame, respectively. Restoring members provide an elastic force bringing the sensing bearings into close contact with the sensing roller and are installed such that both ends thereof are connected to the connecting bracket and the frame, respectively.  
         [0023]     The sensing bearings may be freely rotatably installed on the bearing holders at positions corresponding to both lateral ends of the media, respectively.  
         [0024]     Preferably, an end of the damper member is connected to the central shaft at a position between the bearing holders.  
         [0025]     The damper member may have a spring force relatively less than a spring force of the restoring members installed at the opposite ends of the central shaft for providing the sensing bearings with the elastic force.  
         [0026]     The spring force of the damper member may be about two third of the spring force of one of the restoring members for providing the sensing bearings with the elastic force.  
         [0027]     Preferably, the following equation is satisfied: d=(0.2˜0.25)w, where d is a diameter of the sensing bearing and w is a traveling width of the media.  
         [0028]     According to another aspect of the present invention, there is provided a media thickness detector, comprising a gear train which receives a driving force for feeding media from a driving source and transmits the received driving force. A sensing roller feeds media by receiving the driving force of the driving source through the gear train. Bearing holders are installed on a central shaft at positions corresponding to both lateral ends of the fed media and rotate about the central shaft. Sensing bearings are rotatably installed on the bearing holders such that an elastic force is exerted thereon in a direction in which they are brought into close contact with the sensing roller. A thickness sensor detects a thickness of the media passing between the sensing bearings and the sensing roller, based on a rotating amount of the bearing holders with respect to the central shaft.  
         [0029]     The detector may further comprise a damper member connected to the central shaft at a position between the bearing holders for absorbing vibration generated in the central shaft.  
         [0030]     According to the media thickness detector of the present invention configured as above, there are advantages in that vibration is minimized in the parts coming into contact with the media and the part tolerance is minimized, whereby the thickness of media can be detected more accurately.  
         [0031]     These and other objects of the present application will become more readily 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  
       [0032]     The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:  
         [0033]      FIG. 1  is a side view showing the configuration of a related art media thickness detector;  
         [0034]      FIG. 2  is a plan view showing the configuration of a bearing holder and sensing bearings used in the related art media thickness detector;  
         [0035]      FIG. 3  is a side view showing the configuration of a media thickness detector according to a preferred embodiment of the present invention;  
         [0036]      FIG. 4  is a perspective view showing the main configuration of the embodiment of the present invention; and  
         [0037]      FIG. 5  is a plan view showing the main configuration of the embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0038]     Now, a preferred embodiment of a media thickness detector according to the present invention will be described in detail with reference to the accompanying drawings.  
         [0039]      FIG. 3  is a side view showing the configuration of the media thickness detector according to the preferred embodiment of the present invention,  FIG. 4  is a perspective view showing the main configuration of the embodiment of the present invention, and  FIG. 5  is a plan view showing the main configuration of the embodiment of the present invention.  
         [0040]     Referring to these figures, a driving belt  30  is driven by a driving source (not shown) which generates a driving force for feeding media m, thereby transmitting the driving force. Of course, the driving belt  30  may receive a driving force from an additional driving source separate from the driving source for feeding the media m.  
         [0041]     A first gear  34  is installed on a first gear shaft  32 . Both ends of the first gear shaft  32  are supported on a frame (not shown). In case of an automatic media dispenser, for example, the frame is a member composed of plates spaced apart from each other at a predetermined interval. Both ends of the first gear shaft  32  are installed on the frame. The first gear shaft  32  is driven by the driving belt  30 . To this end, it is preferred that an additional belt pulley (not shown) be coaxially installed on the first gear shaft  32 . A second gear  38  is installed on a second gear shaft  36 , of which both ends in turn are also supported on the frame. The second gear  38  is engaged with the first gear  34  to receive the driving force from the first gear  34 .  
         [0042]     A rotational shaft  40  of which both ends are also supported on the frame is provided with a driven gear  42  at a side thereof The driven gear  42  is engaged with the second gear  38  to receive the driving force from the second gear  38 . A sensing roller  44  is coaxially installed on the rotational shaft  40 . The sensing roller  44  is disposed on a feeding path along which media m travel. Therefore, a plurality of sensing rollers  40  may be provided according to the width of media m. The sensing roller  44  serves to feed the media m while rotating together with the rotational shaft  40 .  
         [0043]     Further, a central shaft  46  of which both ends are supported on the frame is provided. Bearing holders  48  and  48 ′ are integrally formed on and rotated about the central shaft  46 . The bearing holders  48  and  48 ′ are installed to be spaced apart along a length of the central shaft  46 . Sensing bearings  50  are installed on the bearing holders  48  and  48 ′, respectively, such that they can be freely rotated about relevant shafts.  
         [0044]     Since the sensing bearings  50  are placed at positions corresponding to the sensing roller  44 , the sensing bearings  50  should be brought into surface contact with the sensing roller  44  when the media m are not fed between them. The spacing between the sensing bearings  50  should be less than the width of media m along a direction perpendicular to the traveling direction of the media m.  
         [0045]     The following equation is satisfied: d=(0.2˜0.25)w, where d is a diameter of each sensing bearing  50  and w is a traveling width of the media m. Accordingly, when a sheet of the media m has completely passed between the sensing roller  44  and the sensing bearings  50 , the sensing bearings  50  are rotated by approximately 1.5 revolutions. This means that the diameter d of the sensing bearings  50  has been relatively increased as compared to the related art.  
         [0046]     The bearing holders  48  and  48 ′ are designed such that their installation positions correspond to both ends of the traveling media m and the sensing bearings  50 , installed on the bearing holders  48  and  48 ′, can be brought into surface contact with the sensing roller  44 .  
         [0047]     Connecting brackets  52  are provided at both ends of the central shaft  46 , respectively. An end of a restoring member  54  (e.g., a spring or elastic member) is connected to each of the connecting brackets  52 . The other end of the restoring member  54  is hooked into a side of the frame. Since the restoring member  54  is installed as such, the central shaft  46  is rotated in a direction in which the sensing bearing  50  installed on the bearing holder  48  or  48 ′ is brought into close surface contact with the sensing roller  44 . That is, the restoring members  54  serve to bring the sensing bearings  50  into close surface contact with the sensing roller  44 .  
         [0048]     A fixed shaft  56  is installed on the flame such that both ends thereof are supported on the flame. Further, a damper member  58  is installed such that its one end is supported on the fixed shaft  56 . The other end of the damper member  58  is connected to a connecting bracket  52 ′ that is installed in the middle of the central shaft  46 , i.e. between the bearing holders  48  and  48 ′. A coil spring is used for the damper member  58  which in turn serves to absorb vibration generated in the central shaft  46 .  
         [0049]     The coil spring used for the damper member  58  may be of a same type as that used for the restoring member  54 . However, the damper member  58  should have a spring force less than that of a single restoring member  54 . More specifically, the damper member  58  preferably has a spring force corresponding to about two thirds of the spring force of the single restoring member  54 . That is, considering that a restoring member  54  is provided at both ends of the central shaft  46 , the damper member  58  preferably has a spring force corresponding to about one third of the total spring force of the two opposite restoring members  54 . The above spring force setting for the damper member  58  and the restoring members  54  has been determined through actual tests.  
         [0050]     Finally, a thickness sensor  60  is provided for sensing the thickness of media m by measuring a rotating amount of the bearing holders  48  and  48 ′. An example of the thickness sensor  60  includes a RVDT (Rotational Variable Differential Transformer) sensor using a voltage change due to a rotational angle.  
         [0051]     Hereinafter, the operation of the media thickness detector according to the present invention configured as above will be described in detail.  
         [0052]     When the driving source is driven, the media m are fed. The thickness of the traveling media m is detected while they are passing between the sensing roller  44  and the sensing bearings  50 . That is, when the driving force of the driving source is transmitted to the first gear shaft  32  through the driving belt  30 , the first gear shaft  32  and thus the first gear  34  are rotated. The rotation of the first gear  34  causes the second gear  38  engaged with the first gear to be rotated, and the rotational shaft  40  is also rotated by means of the driven gear  42  engaged with the second gear  38 . Here, the second gear  38  is used to set the rotational direction of the sensing roller  44  to be consistent with the traveling direction of the media m.  
         [0053]     Accordingly, while the driving force of the driving source is transmitted through a train of gears  34 ,  38  and  42 , the vibration that may be produced in the driving source and the driving belt  30  can be prevented from being transmitted to the sensing roller  44 .  
         [0054]     When the driving force is transmitted as such and the sensing roller  44  is rotated, the traveling media m passes between the sensing roller  44  and the sensing bearings  50 . When the media m pass between the sensing roller  44  and the sensing bearings  50 , which are in surface contact with each other, the bearing holders  48  and  48 ′, with the sensing bearings  50  installed thereon, are rotated about the central shaft  46  by a predetermined angle against the elastic force of the restoring members  54 .  
         [0055]     Since the bearing holders  48  and  48 ′ are rotated in proportion to the thickness of media m, the rotating amount of the bearing holders  48  and  48 ′ is measured using the thickness sensor  60  and the thickness of media m can be detected.  
         [0056]     Should vibration be produced in the central shaft  46 , i.e. in the bearing holders  48  and  48 ′ or the sensing bearings  50 , the damper member  58  serves to absorb the vibration. Accordingly, the thickness of media m can be accurately measured in accordance with the rotating amount of the bearing holders  48  and  48 ′.  
         [0057]     Since the damper member  58 , having the spring force less than that of the restoring members  54 , is connected in the middle of the central shaft  46 , a substantial damping operation can be accomplished. However, if the spring forces of the damper member  58  and the restoring members  54  are the same as each other, the vibration may be further amplified due to a resonance phenomenon.  
         [0058]     Furthermore, the diameter d of the sensing roller  50  was designed to be relatively larger as compared with the related art. Accordingly, since the sizes of the sensing bearings  50  are increased, the number of revolutions of the sensing bearings  50  made while a sheet of the media m passes between the sensing bearings  50  and the sensing roller  44  can be minimized.  
         [0059]     In addition, the bearing holders  48  and  48 ′ are separately manufactured and mounted to the central shaft  46 . Therefore, it is easy to adjust the sensing bearings  50  installed on the bearing holders  48  and  48 ′ so that they can be brought into surface contact with the sensing roller  44  at a desired pressure, respectively. For example, a user can loosen the attachment screws and move the bearing holders  48  and  48 ′ to ensure that the bearings  50  contact the sensing roller  44  with equal pressure.  
         [0060]     The media thickness detector of the present invention, configured as above, has the following advantages.  
         [0061]     First, the vibration can be prevented from being transmitted to the sensing roller when the driving force of the driving source is transmitted to the sensing roller. Therefore, since the vibration is not transmitted to the sensing roller for feeding the media of which thickness will be measured, there is an advantage in that the thickness of media can be relatively accurately measured.  
         [0062]     Further, the bearing holders on which the sensing bearings are installed are separately manufactured and mounted to the central shaft. Therefore, the installation of the bearing holders can be individually adjusted such that the sensing bearings installed on the bearing holders can be more accurately brought into close contact with the sensing roller. Accordingly, there is another advantage in that the feeding of and thickness measurement for the media can be more accurately accomplished. Also, the bearing holders  48  and  48 ′ can be adjusted to sit at various points along a length of the central shaft  46 . Therefore, the thickness of media m, having various widths (taken in a travel direction of the media m) can be measured, in accordance with the present invention.  
         [0063]     Furthermore, since the damper member is installed at the central shaft on which the sensing bearings are installed, it can absorb the vibration of the central shaft. Therefore, any external disturbance is not transmitted to the sensing bearings, whereby the thickness of media can be more accurately measured.  
         [0064]     The scope of the present invention is not limited by the illustrated embodiment but defined by the appended claims. It will be apparent that those skilled in the art can make various modifications and changes within the scope of the invention defined by the claims.  
         [0065]     For example, by using a linkage or cam instead of the gear train, the vibration from the driving source can be prevented from being transmitted to the sensing roller. Although the coil spring has been used for the damper member, the damper member is not limited thereto. Any kinds of damper members may be employed if they can absorb the vibration from the driving source.