Patent Publication Number: US-2013249163-A1

Title: Paper transmitting mechanism and the document feeder with the paper transmitting mechanism

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a paper transmitting mechanism, and more particularly to a paper transmitting mechanism with a function of detecting position of the paper and adjusting the clamping force according to the position of the paper. 
     2. The Related Art 
     With reference to  FIG. 1 , a common document feeder comprises a transmitting path which is defined by plenty of guiding walls and/or guiding units for guiding paper; and plenty of transmitting roller sets placed along the transmitting path to transmit paper piece by piece through the transmitting path. 
     The transmitting roller sets include a driving roller and a driven roller; the driving roller is connected to a driving device which drives the driving roller. The driven roller is pivotably mounted around the driving roller, and provides paper a proper clamping force and friction for transmitting. 
     However, paper won&#39;t be transmitted smoothly if the clamping force and the friction between the driving roller and the driven roller are too big or too small. For example, if the clamping force and the friction are too small, the paper is apt to slip during the transmitting, and makes images misplaced. 
     In opposite, if the clamping force and the friction are too big, the paper might be pulled by the transmitting roller sets upstream and downstream, and shakes the paper and twists the image. 
     In view of these disadvantages above, the paper transmitting mechanism and the document feeder should be improved. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a paper transmitting mechanism which can adjust the clamping force and the friction between the pressure wheel and the driving wheel according to the position or the transmitting status of the paper. 
     To reach such purpose, the paper transmitting mechanism in this invention is settled along the transmitting path and includes a driving system, a driving wheel, a pressure wheel, a pressure wheel adjusting unit, and a paper sensor. 
     The driving system is connected with the driving wheel and provides the driving wheel torque for transmitting the paper; the pressure wheel is pivotably mounted around the driving wheel and clamps the paper with the driving wheel together. The pressure wheel includes a first rolling portion and a second rolling portion both mounted at the same axis. Wherein, the radius of the second rolling portion is larger than the radius of the first rolling portion, and the second rolling portion is made of softer material (such as foam). 
     The axle of the pressure wheel is connected with the pressure wheel adjusting unit, and driven close or away by the pressure wheel adjusting unit. The paper sensor is electronically connected with the pressure wheel adjusting unit and controls the pressure wheel adjusting unit according to the position of paper. 
     In this embodiment, the paper sensor is placed upstream to the driving wheel and the pressure wheel to detect the position of paper and control the pressure wheel adjusting unit immediately. 
     In another feasible embodiment, the pressure wheel adjusting unit includes a linear driving device controlled to move along a predetermined path and drives the axle of the pressure wheel. 
     In a better embodiment, the pressure wheel adjusting unit further includes an elastomeric unit. One end of the elastomeric unit is connected to the axle of the pressure wheel, the other end of the elastomeric unit is connected to the linear driving device to provide buffer by the elastic deformation of the pressure wheel and the elastomeric unit. 
     Therefore, the paper sensor can control the pressure wheel adjusting unit to increase or decrease the clamping force between the driving wheel and the pressure wheel immediately when it detects the paper either entering or leaving the paper transmitting mechanism. 
     With the paper transmitting mechanism described above, this invention further provides a document feeder which can avoid the paper slipping or vibrating during the transmitting. The document feeder comprises a transmitting path, an operating area placed in the middle of the transmitting path, a paper transmitting mechanism, and a roller set. 
     The paper transmitting mechanism is settled upstream to the operating area, and the roller set is placed downstream to the operating area. The distance between the paper transmitting mechanism and the roller set is shorter than the length of the paper to which they are transmitting to make sure both ends of the paper are clamped stably during the transmitting. 
     The paper transmitting mechanism includes a driving system, a driving wheel, a pressure wheel, a pressure wheel adjusting unit, and a paper sensor. 
     The driving system is connected to the driving wheel and provides the driving wheel torque for transmitting the paper; the pressure wheel is pivotably mounted around the driving wheel and clamps the paper with the driving wheel together. The pressure wheel includes a first rolling portion and a second rolling portion mounted to the same axis, wherein the radius of the second rolling portion is larger than the radius of the first rolling portion. The second rolling portion is made of softer material (such as foam). 
     The axle of the pressure wheel is connected with the pressure wheel adjusting unit, and driven close or away by the pressure wheel adjusting unit. The paper sensor is electronically connected with the pressure wheel adjusting unit and controls the pressure wheel adjusting unit according to the position of paper. 
     The roller comprises a driving device, a driving roller, and a driven roller. The driving device is connected with the driving roller, and provides torque to the driving roller for transmitting the paper; the driven roller is pivotably mounted around the driving roller, and clamps the paper with the driving roller together. 
     In this embodiment, the paper sensor is placed upstream to the driving wheel and the pressure wheel to detect the position of paper and control the pressure wheel adjusting unit immediately. 
     In another feasible embodiment, the pressure wheel adjusting unit includes a linear driving device, the linear driving device is controlled to move along a predetermined path and drive the axle of the pressure wheel. 
     In a better embodiment, the pressure wheel adjusting unit further includes an elastomeric unit. One end of the elastomeric unit is connected to the axle of the pressure wheel, and the other end of the elastomeric unit is connected to the linear driving device, and provides buffer by the elastic deformation of the pressure wheel and the elastomeric unit. 
     As described above, the pressure wheel in this invention is connected to a pressure wheel adjusting unit which can adjust the clamping force between the pressure wheel and the driving wheel automatically according to the position of paper and the transmitting status. Furthermore, the pressure wheel is composed of the first rolling portion and the softer but larger second rolling portion; it makes the pressure wheel keeping contacted with the driving wheel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be apparent to those skilled in the art by reading the following description, with reference to the attached drawings, in which: 
         FIG. 1  is a side-sectional view of a common document feeder; 
         FIG. 2  is a side-sectional view of a document feeder which comprises the paper transmitting mechanism of present invention; 
         FIG. 3  is a perspective view of a pressure wheel of the paper transmitting mechanism of the present invention; 
         FIG. 4  is a side-sectional view that shows the operating process of the document feeder in  FIG. 2 ; 
         FIG. 5  is a side-sectional view that shows the operating process of the document feeder in  FIG. 2 ; 
         FIG. 6  is a side-sectional view that shows the operating process of the document feeder in  FIG. 2 ; 
         FIG. 7  is a side-sectional view that shows the operating process of the document feeder in  FIG. 2 ; and 
         FIG. 8  is a side-sectional view that shows the operating process of the document feeder in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to  FIG. 2 , a paper transmitting mechanism  90  in accordance with the present invention is shown. The paper transmitting mechanism  90  includes a U-shaped transmitting path  10 . Paper  91  enters the transmitting path  10  from the entrance  11  located at the top-right of the transmitting path  10 , then is transmitted through the transmitting path  10  and leave from the exit  12  at the bottom-right of the transmitting path  10 . 
     In order to describe the present invention more clearly, the transmitting path is considered a one-way path in the descriptions below, and comparing two random points in the transmitting path, the side closer to the entrance  11  would be defined as upstream, the side closer to the exit  12  would be defined as downstream. 
     An operating area  13  is located on the transmitting path  10  between the entrance  11  and the exit  12 , at least one device for processing paper is settled in the operating area. In this embodiment, a scanner  14  and a scan sensor  15  is located in the operating area  13 . When the paper  91  trigger the paper sensor  25 , the scanner will be activated and start to scan. 
     A first roller set  30 , a paper transmitting mechanism  20 , and a second roller set  31  are mounted along the transmitting path  10  sequentially. The paper transmitting mechanism  20  is located upstream to the operating area  13 , and the second roller set  31  is located downstream to the operating area  13 ; the distance  92  between the paper transmitting mechanism  20  and the second roller set  31  is shorter than the length of the paper  91  to make sure the front and rear end of the paper  91  is clamped stably during the transmitting and avoid the paper  91  slipping at scanning. 
     The first roller set  30  and the second roller set  31  include a driving device  32 , a driving roller  33 , and a driven roller  34 . The driving device  32  connected with the driving roller  33 , and provides torque to the driving roller  33  for transmitting the paper  91 . The driving roller  33  and the driven roller  34  are both mounted to fixed axle, makes the driven roller  34  to clamp and transmit the paper  91  downstream with the driving roller  33  together. 
     An adjustable pressure wheel  23  is mounted in the paper transmitting mechanism  20 , it includes a driving system  21 , a driving wheel  22  connected with the driving system  21 , a pressure wheel adjusting unit  20 , a pressure wheel  23 , and a paper sensor  25 . 
     The pressure wheel adjusting unit  20  is connected with the axle  231  of the pressure wheel  23 , and drives the axle  231  to move. In this embodiment, a linear driving device  242  is mounted in the pressure wheel adjusting unit  24 , the linear driving device  242  is controlled to move along a predetermined path and drives the axle  231  of the pressure wheel  23  to move. An elastomeric unit  241  is connected between the pressure wheel  23  and the linear driving device  242 , one end of the elastomeric unit  241  is connected with the axle  231  of the pressure wheel  23  and the other end of the elastomeric unit  241  is connected with the linear driving device  242  to offer buffer by the deformation of the pressure wheel  23  and the elastomeric unit  241  due to the clamping force. 
     When the elastomeric unit  241  is compressed, the elastomeric unit  241  provides more normal stress to the pressure wheel  23  and increases the clamping force between the pressure wheel  23  and the driving wheel  22 . In opposite, when the elastomeric unit  241  is released, the elastomeric unit  241  offers less normal stress to the pressure wheel  23  and decrease the clamping force and friction between the pressure wheel  23  and the driving wheel  22 . 
     Referring to  FIG. 3 , to make the paper  91  transmit more stably, the pressure wheel  23  further includes a first rolling portion  232  and a second rolling portion  233 , the first rolling portion  232  and the second rolling portion  233  is settled in the same axis. The radius of second rolling portion  233  is larger than the radius of the first rolling portion  232 . The second rolling portion  233  is made of the material which is softer (such as foam) than that of the first rolling portion  232 . Therefore, the second rolling portion  233  which becomes larger and softer can keep contacting with the driving wheel  22 , and deform easily when the clamping force between the driving wheel  22  and the pressure wheel  23  increased to clamp the paper  91  more averagely. 
     Referring to  FIG. 4 , a document feeder  90  with the paper transmitting mechanism  20  in accordance with the present invention proceeds as following: when the paper  91  enters the transmitting path  10 , it would be guide to the operating area  13  by the first roller set  30  and the transmitting path  10  and trigger the paper sensor  25  after being transmitted through the first roller set  30 , and activate the paper sensor  25  to send a paper-entering signal for controlling the pressure wheel adjusting unit  24  to increase the clamping force between the driving wheel  22  and the pressure wheel  23 . 
     Referring to  FIG. 5 , the paper  91  transmitted to the downstream of the transmitting path  10  will be clamped by the paper transmitting mechanism  20 . Meanwhile, the paper transmitting mechanism  20  increases the clamping force upon receiving the paper-entering signal to avoid the paper  91  slipping during the transmitting. After that, the paper  91  will be transmitted downstream and triggers the scan sensor to activate the scanner starting scan. 
     Referring to  FIG. 6 , the paper  91  is transmitted downstream, and clamped by the second roller set  31 . The front and rear end of the paper  91  is clamped by the paper transmitting mechanism  20  and the second roller set  31  to make sure the paper  91  keeping stable and not to slip during the scanning. 
     Referring to  FIG. 7 , the paper  91  is transmitted downstream and left on the trigger area of the paper sensor  25 . The paper sensor  25  sent a paper-leaving signal for controlling the pressure wheel adjusting unit  24  to decrease the clamping force between the driving wheel  22  and the pressure wheel  23  after a predetermined delay. It avoids the paper  91  vibrating when the paper  91  leaves the paper transmitting mechanism  20 . 
     Referring to  FIG. 8 , the paper  91  is transmitted to the exit  12 , and leaves the trigger area of the scan sensor  15 . The scan sensor  15  is deactivated and stops the scan process. 
     As described above, the pressure wheel is connected with a pressure wheel adjusting unit, and the pressure wheel adjusting unit is electronically connected with a paper sensor. It makes the pressure wheel be able to adjust the clamping force according to the position and the transmitting status of the paper. Furthermore, the pressure wheel is combined by a smaller but harder first rolling portion and a softer but larger second rolling portion to keep the pressure wheel contacting with the driving wheel for offering clamping force and avoiding the paper slipping.