Abstract:
An optical reader and the driving motor of a scanner are integrally mounted on a movable module, which can slide back and forth along a track to scan an image. The driving motor exerts a force on a fixed rack attached to the frame of the scanner through a pinion. The reaction to the force causes the movable module to slide. The rack and pinion mechanism can be replaced with a friction tape and roller combination, or a steel wire wrapped around a wheel attached to the movable module.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an image reading head for an image scanner, a facsimile machine, or a copier. In particular, the present invention discloses a flat bed image reading head having a motor mounted thereon. 
     2. Description of the Prior Art 
     Flat bed image scanners are widely used today as periphery equipment for computers. A flat bed image scanner can rapidly scan a document, a magazine, a book, a graph or a picture for inputting images thereof into a computer for processing. A flat bed scanner has an optical reader, a driving mechanism, a processing circuit, a scanning window and a frame. Today, the trend is to make the scanner lightweight, thin, narrow and miniaturized. It is thus desirable that the optical reading mechanism and the driving mechanism occupy as little space as possible. 
     A conventional image reading head  199  is shown in FIG.  1  and includes: a light source  101 , a series of reflecting mirrors  131 ,  132 ,  133 , a lens  104  and an image sensor  105 . The driving mechanism includes: a motor  107 , a gear train  108 , an idler  181 , a closed-loop belt  109 , and a sliding rail  110 . The operation of the flat bed scanner is as follows: Referring to FIG. 1, a document D to be scanned is placed on top of a window  102 . After the light source  101  illuminates the document D, the reflected light from the document D reflects from the reflecting mirrors  131 ,  132 ,  133  to the lens  104  to reach the image sensor  105 . The image sensor  105  feeds image signals to an image processing circuit (not shown) for digitizing the signals, which are then fed to a computer for further processing. When the image sensor  105  completes a row of image signals, the driving mechanism moves the image reader to a next scanning area until the whole image is read. 
     Structurally, the advancing motor  107  and the gear train  108  are both fixed on the frame  112 . The closed-loop belt  109  has one end connected to the gear train  108  and the other end connected to the idler  181 . The closed-loop belt  109  is attached to the optical reading mechanism  199  to move the optical reading mechanism for effecting scanning action. 
     SUMMARY OF THE INVENTION 
     An object of this invention is to reduce the size of a flat bed scanner. Another object of this invention is to reduce the number of parts in a flat bed scanner to enhance the quality and to reduce the cost of the flat bed scanner. 
     These objects are obtained by combining the driving mechanism and the reading mechanism of the scanner into the same module. A fixture is mounted on the frame of the scanner. When the driving mechanism exerts a force on the fixture, the reaction causes the movable module to slide back and forth along a guiding portion and to scan the image to be read. The force from the movable module can be exerted on the fixture through a rack and pinion mechanism or through a friction wheel and friction tape. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows an image reading head for a prior art flat bed scanner. 
     FIG. 2 shows a side view of an image reading head in a scanner structure based on the present invention. 
     FIG. 3 is a perspective view of a scanning module of the present invention. 
     FIG. 4 is an enlarged view of a portion of FIG. 2 depicting a rack and pinion mechanism. 
     FIG. 5 shows a wire wrapping around a driven wheel attached to a scanning module of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     To achieve the object of the present invention, a drastic modification of the driving mechanism of a conventional scanner has been made. A completely new design is used to mount the driving mechanism onto the optical reading mechanism  199 . Referring to FIG. 2, a present invention flat bed scanner  200  combines a driving mechanism  207  with an image sensor  205  to form a combined optical reading and driving scanning module  299 . This combined reading/driving scanning module  299  utilizes the engagement of a gear or pinion  208  with a belt  291 . The belt  291  is a straight line rack with teeth on one side and with the two ends fixed at two stationary posts  291 A and  291 B to form a rack and pinion mechanism. An enlarged view of the rack and pinion mechanism is shown FIG.  4 . When the pinion  208  rotates, it drags the scanning module  299 . Due to the action and reaction with the belt  291 , the scanning module  299  moves back and forth along a guiding rail  210  to perform scanning of a document D placed on a window  202  of the flat bed scanner  200 . As explained in the Description of the Prior Art, a light source  201  of the flat bed scanner  200  is used to illuminate the document D. Light from the document D reflects from mirrors  231 ,  232  and  233  through lens  204  to the image sensor  205 . With reference to FIGS. 2 and 3, the scanning module  299  is connected to the guiding rail  210  through a sleeve  209  on which the scanning module  299  is mounted and which can glide along the guiding rail  210 . 
     In comparison with conventional structure, the present invention has the following features: 
     In terms of components, the present invention eliminates the idler  181  shown in FIG.  1 . 
     In terms of space, the present invention saves the space occupied by the motor  107 , the gear train  108 , and the idler  181 . The space occupied by the belt is reduced by at least a factor of 2. 
     In terms of motion, the conventional technique uses a closed-loop belt  109 , which rotates during operation, whereas the present invention scanner  200  uses a stationary rack-type belt which is fixed at the two ends at posts  291 A and  291 B. 
     In terms of structure, the conventional method uses a closed-loop belt  109  which is fixed to the image reading module  199 , whereas in the present invention, the rack-type belt  291  meshes the scanning module  299  with the pinion  208 . 
     One embodiment of the present invention is shown in FIG.  2 . The scanning module  299  is mounted with the motor  207  and pinion  208 . Due to the meshing of the teeth of the pinion  208  with those of the rack-type belt  291 , the scanning module  299  is activated and moved. The rack-type belt  291  has its ends fixed at posts  291 A and  291 B which, in turn, are fixed on the frame  212 . 
     Referring to FIG. 4, when the scanning module  299  scans an area of an image on document D, the motor  207  transfers its power through the pinion  208  to the rack-type belt  291 . Since the belt  291  is stationary, the scanning module  299  is driven back and forth along the guiding rail  210  to perform the scanning function. The present invention uses a novel design to mount the advancing motor  207  and the pinion  208  onto the reading module  199  of the conventional design. Unused space adjacent the lens  104  of a conventional design is fully utilized with the motor  207 , and so the volume of the scanning module  299  of the present invention flat bed scanner  200  is no larger than the space occupied by the conventional reading module  199 . With the motor  207  of the present invention being mounted in the unused space adjacent to the lens  204 , space normally occupied by the motor  107  and the gear train  108  is thereby saved. In addition, due to the reduction of component parts, the reliability of the flat bed scanner  200  is improved, and costs are reduced. 
     In another embodiment of the present invention, the reaction rack-type belt  291  is installed as a part of the frame  212  of the flat bed scanner  200 , since the rack  291  is stationary. The reaction mechanism is formed directly on the frame  212  during fabrication, and saves the space of the belt  291  and its associated stationary parts used in the first embodiment. Thus, the component parts of the flat bed scanner  200  are further reduced, resulting in improved reliability and cost benefits over the first embodiment. In comparison with conventional structure shown in FIG. 1, this second embodiment has the following features: 
     In terms of components, the second embodiment of the present invention does not require the idler  181 , belt  109  and fixtures for the belt  109 . 
     In terms of space, this invention saves on the space occupied by the advancing motor  107 , the gear train  108  and the idler  181 , and the space occupied by the belt  109 . 
     In terms of motion, the conventional technique uses a moving closed-loop belt  109 , while this second embodiment of the present invention utilizes the reaction of the frame  212  to propel the moving scanning module  299 . The principle of operation is totally different. There is no motion of the belt  109 . 
     In terms of structure, the optical reading module  199  is attached to the belt  109  at a fixed point. This invention uses the reaction of the frame  212  to propel the scanning module  299 . 
     The foregoing embodiments are merely the preferred examples of the present invention, and are by no means limited to these two examples. Any embodiment using equivalent principles is within the scope of this invention. For example, the rack and pinion structure can be replaced with roller and friction tapes; or, alternatively, the rack and pinion mechanism maybe replaced with a driving wheel  308  and a steel line  391  as shown in FIG. 5, in which the steel line  391  has two ends fixed to two posts  391 A and  391 B on the frame  212 . The steel line  391  wraps around the driving wheel  308 , which is attached to the scanning module  299 , and the scanning module  299  moves back and forth when the driving wheel  308  turns. The sleeve  209  sliding on the guiding rail  210  can be replaced with wheels sliding on a track. These equivalent techniques are all within the scope of this invention. in the first embodiment. In comparison with conventional structure shown in FIG. 1, this second embodiment has the following features: 
     In terms of components, the present invention saves the idler  181 , belt  109  and the fixtures for the belt  109 . 
     In terms of space, this invention saves the space occupied by the advancing motor  107 , the gear train  108  and the idler  181 , and the space occupied by the belt  109 . 
     In terms of motion, the conventional technique uses a moving closed-loop belt  109 , while this invention utilizes the reaction of the frame to propel the moving read/drive module  299 . The principle of operation is totally different. There is no motion of the belt  109 . 
     In terms of structure, the optical reading module  199  is attached to the belt  109  at a fixed point. This invention uses the reaction of the frame to propel the read/drive module. The principle of operation is totally different. There is no corresponding part of the belt  109  in the present invention. 
     The foregoing embodiments are merely the preferred examples of the present invention, and are by no means limited to these two examples. Any embodiments using equivalent principle are all within the scope of this invention. For example, the rack and pinion structure can be replaced with roller and friction tapes; or, alternatively, the rack and pinion mechanism may be replaced with a driving wheel  308  and a steel line  391  as shown in FIG. 5, in which the wire with two ends fixed to two posts  391 A,  391 B on the frame wraps around the driving wheel  308  attached to the reading/driving module, and the reading/driving module moves back and forth when the driving wheel  308  turns. The sleeve sliding on the track can be replaced with wheels sliding on the track. These equivalent techniques are all within the scope of this invention.