Patent Publication Number: US-2005116408-A1

Title: Paper-feeding device with automatic paper detecting function

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a paper-feeding device, and more particularly, to a paper-feeding device for detecting paper status automatically.  
      2. Description of the Prior Art  
      Business machines are often used in offices to help with the processing of documents. These business machines include copiers, fax machines, printers, etc. To facilitate continuous document processing, these business machines all have paper feeding systems to supply paper. Since most types of business machines can only process a single-paged document a page at a time, the paper feeding system of the machine must be able to send exactly one sheet of paper each time to the machine. If the paper feeding system sends out more than one sheet of paper at a time, the sheets are likely to jam in the machine, causing delays in the entire document handling process, as well as wasting paper. Therefore, it is of great importance that a paper feeding system that can feed exactly one sheet of paper at a time be designed.  
      In general, there are two types of feeding motors of paper feeding systems. One is a DC motor module, and the other is a stepping motor module. The paper feeding system with the DC motor module includes a DC motor, an encoder, and a stripe. The encoder and the strip can feed back velocity and location of paper for dealing with paper immediately during the situation that a feeding roller is driven by the DC motor and paper does not slide on the feeding roller. But in this way there are more necessary components and the cost will increase. In addition, the control method is more complicated.  
      Furthermore the paper feeding system with the stepping motor module only provides a feeding sensor and a stepping motor for feeding paper instead of detecting paper status. Because the immediate status of paper cannot be detected, such as a paper jam, the system cannot deal with paper immediately.  
      In addition, for upgrading the printer quality, noise control is one of the important things. Nowadays the noise generated during operation is mostly caused by motors, especially in the event of a breakdown of the stepping motor. Therefore if the breakdown of the steeping motor cannot be repaired immediately, the noise problem cannot be solved.  
     SUMMARY OF INVENTION  
      It is therefore a primary objective of the claimed invention to provide a paper-feeding device for detecting paper status automatically to solve the above-mentioned problems.  
      According to the claimed invention, a paper-feeding device includes a paper tray for holding paper, a paper advance module for picking up the paper held on the paper tray and outputting the paper, a sensing module for sensing the deformation of the paper during the feeding process and outputting a sensing signal when the paper advances in a sensing area, and a control unit for determining the paper feeding status according to the sensing signal generated from the sensing module.  
      According to the claimed invention, a paper-feeding method includes feeding a paper, outputting a sensing signal according to deformation of the paper during the feeding process, and determining whether the paper advances normally or not according to the sensing signal.  
      These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       FIG. 1  is a diagram of a printer according to the present invention.  
       FIG. 2  is a schematic diagram of the printer feeding paper.  
       FIG. 3  is a functional block diagram of the printer.  
       FIG. 4  is a flowchart of paper-feeding mechanism according to the present invention.  
       FIG. 5  is a schematic diagram of the paper deforming in the sensing area.  
       FIG. 6  is a signal oscillogram of a motor and a sensing module when the paper advances normally.  
       FIG. 7  is a signal oscillogram of the motor and the sensing module when the paper jams.  
       FIG. 8  is a schematic diagram of a sensing module detecting deformation of the paper of another embodiment according to the present invention. 
    
    
     DETAILED DESCRIPTION  
      Please refer to  FIG. 1  and  FIG. 2 .  FIG. 1  is a diagram of a printer  10  according to the present invention.  FIG. 2  is a schematic diagram of the printer  10  feeding paper. The printer  10  includes a paper tray  12  for holding paper  14 , a paper holder  16  for holding the paper  14 , a carriage  18  for moving on a shaft  20 , an ink box  22  installed on the carriage  18  for providing ink to print the paper  14 . The printer further includes a paper advance module  24 . The paper advance module  24  includes a pickup roller  26  installed above the paper tray  12  in a rotatable manner for picking up the paper  14  held on the paper tray  12 , a feed roller  28  installed in front of the bottom of the paper tray  12  in a rotatable manner for driving the paper  14  to move along an advancing direction, and a motor  30  for driving the pickup roller  26  and the feed roller  28 . The motor  28  can be a stepping motor or a DC motor. The printer  10  further includes a sensing module  32  for sensing a deformation of the paper  14  during the feeding process and outputting a sensing signal, and a paper constrainer  34  for constraining the buckling deformation of the paper  14  when the paper  14  enters sensing area of the sensing module  32 .  
      Please refer to  FIG. 3 .  FIG. 3  is a functional block diagram of the printer  10 . The printer  10  further includes a control unit  36  electrically connected to the sensing module  32  and the motor  30  for determining the feeding status of the paper  14  according to the sensing signal outputted from the sensing module  32  and controlling the motor  30  according to the feeding status of the paper  14 . The control unit  36  includes an amplifier  38  for amplifying the buckling deformation of the paper  14  detected by the sensing module  32 , and an analog-to-digital converter  40  for converting analog signals outputted from the amplifier  38  into digital signals. The printer  10  further includes a display unit  42  electrically connected to the control unit  36  for presenting the status of the paper  14  detected by the sensing module  32 .  
      Please refer to  FIG. 4 .  FIG. 4  is a flowchart of paper-feeding mechanism according to the present invention. The method includes the following steps:  
      Step  100 : The paper advance module  24  starts feeding the paper  14 .  
      Step  102 : The sensing module  32  detects the buckling deformation of the paper  14  and outputs a corresponding sensing signal to the control unit  36 .  
      Step  104 : The control unit  36  determines the feeding status of the paper  14  such as whether the paper  14  advances normally according to the corresponding sensing signal. If the paper  14  advances normally, the paper  14  continues advancing until the paper  14  advances out completely. And if the paper  14  advances abnormally, go to Step  106 .  
      Step  106 : The control unit  36  generates an interrupt signal to the motor  30 . When the motor  30  receives the interrupt signal from the control unit  36 , the motor  30  stops the paper advance module  24  from feeding the paper  14 .  
      Step  108 : Finish feeding the paper  14 .  
      The detailed description of the above-mentioned steps is introduced as follows. The motor  30  generates the feeding power of the paper advance module  24  of the printer  10 . The motor  30  drives the pickup roller  26  and the feed roller  28  to rotate, and the paper  14  advances by the static frictional force between the paper  14  and the surface of rollers after the pickup roller  26  and the feed roller  28  feed the paper  14 . Please refer to  FIG. 5 .  FIG. 5  is a schematic diagram of the paper  14  deforming in the sensing area. After the paper  14  advances into the feed roller  28 , the motor  30  drives the feed roller  28  to feed the paper  14  so that the front end of the paper  14  advances by the frictional force between the paper  14  and the surface of the feed roller  28 . Due to the sudden advance of the paper  14 , the front of the paper  12  will experience a buckling deformation. And because the range of the buckling deformation is located above the sensing module  32 , the sensing module  32  can measure the deforming variation of the paper  14 . The sensing module  32  can be a reflective-type sensor for emitting a sensing signal to the paper  14  and receiving the sensing signal reflected from the paper  14  to calculate the deformation of the paper  14 . The sensing module  32  can include only one sensor or a plurality of sensors, and the sensor can be a breaking-type sensor, a reflective-type sensor, a receiving-type sensor, and so on. After the paper  14  advances into the sensing area, the deformation magnitude of the paper  14  has to be limited so that the deformation of the paper  14  can be located within the measurable range of the sensing module  32 . Therefore, the paper constrainer  34  can constrain the buckling deformation of the paper  14  when the paper  14  advances into the sensing area of the sensing module  32 . The distance between the paper constrainer  34  and the sensing module  32  can be 5 mm, that is, the deformation of the paper  14  is limited within 5 mm. The distance between the paper constrainer  34  and the sensing module  32  can be designed according to the measurable range of the sensing module  32 .  
      When the paper  14  starts advancing, the paper holder  16  does not apply any force on the paper  14  so that the end nearby the paper holder  16  of the paper  14  is a free end and the paper can be deformed in a wave motion. After the paper  14  finishes advancing, the paper holder  16  can hold the paper  14  that has not been fed yet. During the feeding procedure the end nearby the pickup roller  26  of the paper  14  is not fixed by the paper holder  26  so as to be a free end, and the end nearby the feed roller  28  of the paper  14  can be regarded as a fixed end for fixing the paper  14  so that the paper  14  can advance with the feed roller  28  simultaneously instead of sliding. In addition, because one end of the paper  14  is a free end and the other end of the paper  14  is a fixed end, the paper  14  can experience a buckling deformation easily for providing the basis of generating sensing signals by the sensing module  32 .  
      Please refer to  FIG. 6 .  FIG. 6  is a signal oscillogram of the motor  30  and the sensing module  32  when the paper  14  advances normally. When the paper  14  advances normally and every time the motor  30  receives a driving signal, the paper  14  can advance at a small distance along the advancing direction. Due to the sudden advance of the paper  14 , the front of the paper  12  will experience a buckling deformation. Therefore the sensing module  32  detects the deformation variation of the paper  14  and generates a corresponding response signal. The time interval between the driving signal of the motor  30  and the response signal generated by the sensing module  32  is small because after generating the driving signal of the motor  30 , the sensing module  32  detects the deformation variation of the paper  14  and generates the response signal timely. The above-mentioned situation is the normal situation of feeding procedure. Please refer to  FIG. 7 .  FIG. 7  is a signal oscillogram of the motor  30  and the sensing module  32  when the paper  14  jams. When the paper  14  jams, even if the motor  30  continues receiving the driving signal and the motor  30  rotates, the paper  14  cannot advance normally. Therefore there is no buckling deformation of the paper  14  due to the sudden advance of the paper  14 . And the sensing module  32  cannot detect the deformation variation of the paper  14  and cannot generate the corresponding response signal. The buckling deformation of the paper  14  detected by the sensing module  32  can be transmitted to the control unit  36 . The amplifier  38  can amplify the signal, and then the analog-to-digital converter  40  can convert the analog signal outputted from the amplifier  38  into the digital signal. The control unit  36  can determine whether the paper  14  advances normally or not according to the digital signal generated by the analog-to-digital converter  40  and the above-mentioned criteria.  
      When the paper  14  advances normally, the paper  14  continues advancing until the paper  14  advances out completely. When the paper  14  jams, the control unit  36  can generate an interrupt signal to the motor  30 . After the motor  30  receives the interrupt signal from the control unit  36 , the motor  30  stops the paper advance module  24  from feeding the paper  14 . That is, the feeding procedure is over. The control unit  36  also can transmit a signal to the display unit  42  for displaying the paper jam status. The display method can use either light or sound for warning users about the abnormal feeding status. Because the control unit  36  can adjust the operation of the motor  30  timely according to the sensing signal generated from the sensing module  32 , the print efficiency can be increased and the noise due to the motor  30  out of control can be reduced. That is, the control unit  36  can determine feeding status of the paper  14  according to the sensing signal generated from the sensing module  32  and generate a feedback signal to control the print procedure and the operation of the motor  30 . It is a closed-loop feedback control method for controlling the print procedure and the feeding status of the paper  14 .  
      The sensing module  32  can detect the deformation of the paper  14  by using a strain gauge. Please refer to  FIG. 8 .  FIG. 8  is a schematic diagram of a sensing module  44  detecting deformation of the paper  14  of another embodiment according to the present invention. The sensing module  44  includes a transmission link  46  having one end to contact the paper  14 , a spring  48  sheathed on the transmission link  46 , and a deformation sensor  50  installed on the spring  48  for sensing deformation of the spring  48  tugged by the deformation of the paper  14  during the feeding process. The deformation sensor  50  can be a strain gauge, a tensiometer, a contact probe, a sensor made of piezoelectric material, and so on. For example, if the deformation sensor  50  is a strain gauge, the strain gauge will generate different voltage magnitudes according to different deformations of the paper  14  due to that one end of the transmission link  46  contacts the surface of the paper  14  slightly for transferring the motion status of the paper  14  to the strain gauge via the spring  48 . The voltage value generated by the strain gauge can be outputted to a converting circuit  52  for converting the voltage value into the corresponding deformation of the paper  14  and transmitting the deformation data to the control unit  36  so as to determine the feeding status of the paper  14 . Furthermore, the control unit  36  can generate a feedback signal to control the print procedure and the operation of the motor  30 .  
      In contrast to the prior art, the present invention provides a paper-feeding device that can detect deformation of the paper  14  during the feeding procedure with the sensing module  14  and generate the corresponding sensing signal to the control unit  36  for adjusting the operation of the motor  30  timely according to the corresponding sensing signal transmitted from the sensing module  32 . Therefore the print efficiency can be increased and the noise due to the motor  30  out of control can be reduced. That is, the control unit  36  can determine feeding status of the paper  14  according to the sensing signal generated from the sensing module  32  and generate a feedback signal to control the print procedure and the operation of the motor  30 . The present invention uses a closed-loop feedback control method for controlling the print procedure and the feeding status of the paper  14 . The paper-feeding device according to the present invention can be used for printers, faxes, multi-function products (MFP), and so on. The present invention can detect status of the paper  14  and adjust the operation of the paper advance module  24  so that the paper jam problem can be solved immediately to avoid noise, and the efficiency and value of products can be upgraded.  
      Those skilled in the art will readily observe that numerous modifications and alterations of the device and the method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.