Patent Publication Number: US-2002003207-A1

Title: Drive mechanism of optical scanner

Description:
FIELD OF THE INVENTION  
       [0001] This invention relates to the drive mechanism of optical scanner. More particularly, two motors are used for providing the output (torque) of different rotation speed respectively, so the scope of scan speed is enlarged to fit in with the required scan speed of the scanner under various resolutions.  
       BACKGROUND OF THE INVENTION  
       [0002] Scanner is a common peripheral equipment of computer, by means of internal image pick-up device to pick up document image and transfer the pick-up image into digital signal as input of computer and then perform image processing of the document.  
       [0003]FIG. 1A is a diagram showing optical scanner of prior art. The optical scanner of prior art comprises a housing  12  with upper opening  11 , transparent manuscript surface  13  that could carry weight of document and an image pick-up device  14  with image pick-up function. The said transparent manuscript surface  13  is combined with upper opening  11  of the housing  11 . The said image pick-up device  14  is set within the housing and is promoted to scan image by drive mechanism (not shown) provided by optical scanner  1 , wherein image pick-up device  14  may be optical path device of Charged Couple Device (CCD) or Contact Image Sensor (CIS).  
       [0004]FIG. 1B is a diagram showing optical scanner&#39;s drive mechanism of conventional art. The drive mechanism  2  is mounted under the transparent manuscript surface, and promotes image pick-up device  14  to scan, comprising a scan path, a delivery device  22 , a set of decelerated gears and a motor  24 .  
       [0005] The scanning path  21  consists of a slip bar  211  and a sliding rail  212 , the above slip and sliding rail parallel each other, and the image pick-up device  14  provides with a guide hole  141  and rotating wheel  142 , and they cooperate with slip bar  211  and sliding rail  212  so as to scan back and forth in the scan path  21 .  
       [0006] The delivery device  22  comprises a actuating gear  221 , a passive gear  222  and a annular gear belt  223 , wherein actuating gear  221  and passive gear are mounted in the two ends of the housing  12  respectively, the annular gear belt  223  is set on two gears  221 ,  222  respectively and parallel with scan path  21 , furthermore the annular gear belt  223  combines with the image pick-up device  14 .  
       [0007] The reduction gear set  23  is combined with motor  24  and actuating gear  221  respectively, its primary function is to provide appropriate reduction ratio so that rotational speed (torque) of motor  24  is reduced to appropriate extent and then communicate motive power to actuating gear  221 .  
       [0008] Thus the scanning mode of drive mechanism is to promote the rotation of delivery device  22  by way of output power of motor  24  so that the annular gear belt  223  drives image pick-up device  14  to move back and forth in the scan path  21 , and then scan document over the transparent manuscript surface.  
       [0009] However there are many design problems in the optical scanner  1  of the prior art. Since current consumers not only demand to increase the resolution of the optical scanner  1 , also demand scanning speed as fast as possible simultaneously, but if the resolution of optical scanner is increased, speed of image processing becomes slow, then by adjusting reduction ratio of a reduction gear set or adopting higher rotational speed motor so as to increase scanning speed of optical scanner  1 .  
       [0010] However whether DC motor or stepping motor, there both have definite specification and rotational speed (torque) range limit while left the factory, but all of the general companies purchase motor that has definite specification. Hence it is achieved by changing reduction ratio of reduction gear set, but if the wider the demanded resolution range of optical scanner, the larger the relative range of scanning speed; thus if adjust only reduction ratio change of reduction gear set that can not cover the needs of higher and lower scanning speed simultaneously, so if the motor which has two and more specifications is used and two scopes of rotational speed (torque) are provided in the same drive system simultaneously, the scanning speed scope of scanner is widened so as to match with scanning speed design of scanner under various resolutions.  
       SUMMARY OF THE INVENTION  
       [0011] The main object of this invention is to provide a drive mechanism of optical scanner. The drive mechanism is provided wider scope of scanning speed for scanner and matched with scanning speed design of scanner that has various resolutions.  
       [0012] The drive mechanism of optical scanner according to the present invention comprises an image pick-up device, a delivery device, a first motor and a second motor and a controller, the said image pick-up device can move back and forth in the scan path provided by optical scanner so as to perform image scan. The said delivery device consists of a actuating wheel, a passive wheel and a annular conveyor belt; the above-mentioned two rotating wheels are set in the two ends of scan path, the circular conveyor belt is harnessed on two rotating wheels, wherein the circular conveyor belt is parallel with scan path and connects to image pick-up device, furthermore a set of decelerated gear is set in the axis of actuating gear and a appropriate reduction ratio is provided.  
       [0013] The first motor provides rotational power of the first rotational speed and its upper output shaft can drive reduction gear set to promote rotation of delivery device, while the second motor provides rotational power of the second rotational speed and its upper output shaft can drive reduction gear set to promote rotation of delivery device, the controller is connected to the two motors in the electrical connection way so that the drive mechanism is drove by one of the two motors at the same time and the other motor is controlled in the idle running.  
       [0014] Because the rotational speed of the first motor is different from rotational speed of the second motor and both the scopes of rotational speed (torque) provided by the above-mentioned two motors are the output scopes of drive mechanism&#39;s rotational speed. Hence the scan speed scope of scanner could be widened in order to fit in with the required scan speed design of the scanner under various resolutions.  
       [0015] These and other features and advantages of the present invention will be better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0016]FIG. 1A is an optical scanner diagram of prior art.  
     [0017]FIG. 1B is a drive mechanism diagram of optical scanner according to the prior art.  
     [0018]FIG. 2 diagrammatically represents a first embodiment of the drive mechanism according to optical scanner of the present invention.  
     [0019]FIG. 3 diagrammatically represents a second embodiment of the drive mechanism according to optical scanner of the present invention.  
     [0020]FIG. 4 diagrammatically represents a third embodiment of the drive mechanism according to optical scanner of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0021] Refer to FIG. 2, diagrammatically represents a first embodiment of the drive mechanism according to optical scanner of the present invention, the drive mechanism comprises an image pick-up device  31 , delivery device  32 , a first motor  33 , a second motor  34  and a controller  35 .  
     [0022] The image pick-up device  31  may be an optical path device with a Charged Couple Device (CCD) or a Contact Image Sensor (CIS), it has a guide hole  311  and a roller  312 , the scan path  21  provided by optical scanner  1  consists of two guide bars  211  that parallel each other and guide rail  212 , the image pick-up device matches with guide bars  211  and guide rail respectively by means of guide hole  311  and roller  312  so that it can move back and forth in the scan path  21  to scan the document.  
     [0023] The delivery device  32  consists of actuating wheel  321 , passive wheel  322  and a annular conveyor belt  323 ; the above-mentioned two rotating wheels  321 , 322  may be two fixed pulleys or two gears, and annular conveyor belt  323  may be a annular rope sheave (pulley) or annular gear are set in the two ends of scan path  21 , and the annular conveyor belt is harnessed on two rotating wheels  321 , 322 , wherein the annular conveyor belt is parallel with scan path  21  and connects to image pick-up device  31 , furthermore a reduction gear set is set in the axis of actuating gear and a appropriate reduction ratio is provided.  
     [0024] The first motor  33  may be a DC motor or stepping motor, on its output shaft the motor  33  is combined with a gear  331  that engages with a set of reduction gear  36 . The first motor  33  provides rotational power of the first rotational speed and the power can drive reduction gear set  36  to promote rotation of delivery device  32  so that the image pick-up device  31  moves back and forth in the scan path  21  in order to scan the document.  
     [0025] The second motor  34  may be a DC motor or stepping motor, on its output shaft the motor  34  is combined with a gear  341  that engages with a set of reduction gear  36 . The second motor  34  provides rotational power of the second rotational speed and the power can drive reduction gear set  36  to promote rotation of delivery device  32  so that the image pick-up device  31  moves back and forth in the scan path  21  in order to scan the document.  
     [0026] The controller  35  is connected to the first motor  33  and the second motor  34  respectively in the electrical connection way, the drive mechanism  3  is drove only by one of the two motors at the same time and the other motor is controlled in the idle running through control of the controller  35 . Hence according to the invention, the scope of rotational speed (torque) provided by the first motor  33  or second motor  34  is served as the rotational speed (torque) scope of drive mechanism  3  and the rotational speed (torque) scope of drive mechanism  3  is further widened. Due to drive mechanism  3  outputs larger rotational speed (torque) scope according to the invention, thus how the resolution of optical scanner is designed in any case, a appropriate rotational speed (torque) could be found in the drive mechanism  3  to match with optical scanner  1 , so the application scope of drive mechanism  3  of optical scanner  1  is widened relatively.  
     [0027] Refer to FIG. 3, a second embodiment of the drive mechanism according to optical scanner of the present invention. Most components within the embodiment are the same as the first embodiment and thus given unnecessary details no more, here only the differences are described. The greatest difference according to the embodiment is that rotational speed (torque) output of the first motor  33  equals to rotational speed (torque) output of the second motor  34 , but different reduction ratio could be created by means of different size of gear combination so that enable two identical motors  33 , 34  to create different scope of rotational speed (torque). For example, the different diameter gears  331 , 341  are mounted on the output shaft of first and second motor  33 , 34 , or a reduction gear set  361  is set between reduction gear ser  36  and the first motor, thus enable the two motors of identical rotational speed (torque) to create larger scope output of rotational speed (torque).  
     [0028] Refer to FIG. 4, a third embodiment of the drive mechanism according to optical scanner of the present invention. Besides a reduction gear set  36  is installed on the axis of the actuating wheel  221  according to the embodiment, a reduction gear set  37  is installed on the axis of the actuating wheel  222  simultaneously and enable the output shaft&#39;s gear  331  of first motor  33  to engage with the reduction gear set  36  of actuating wheel  321  while the output shaft&#39;s gear  341  of second motor  34  to engage with the reduction gear set  37  of actuating wheel  322 . Controller  35  controls both the above-mentioned motors  33 , 34 , now reduction ratios of reduction gear sets  36 , 37  which are installed on the actuating wheel  321  and passive wheel  322  respectively may be identical and motor of different rotational speed (torque) is used, or different reduction ratio of reduction gear sets  36 , 37  and motor of identical rotational speed (torque) is used.  
     [0029] It is worthy to mention that although the motor which is used by the above three embodiments may be a DC motor or stepping motor, but a encoder must be added if a DC motor is used so as to track the position of image pick-up device at any time in the scan path.  
     [0030] Of course, the drive mechanism of optical scanner according to the present invention has been described above by taking the case as better embodiment, but implementation scope of the present invention is not really limited to the scope of the embodiment described. All of the modifications, which are made by those whose familiar with the art without departing from the spirit of the invention, are belong to the scope of the present invention. Thus the protective scope of the invention is based on the following claims.