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:
This is a Continuation-in-part Application of U.S. patent application Ser. No. 08/821,217, filed Mar. 20, 1997. 
    
    
     This invention relates to image scanner, facsimile and image printer—in particular to a reading head for such equipment. 
     The Flat Bed Image Scanner is widely used today as a periphery equipment for a computer. It can rapidly scan a document, a magazine, a book, a graph and a picture and input into a computer for processing. A flat bed scanner is composed of an optical reader, a driving mechanism, a processing circuit, a scanning window and a frame. Today, the trend is to make the scanner light-weight, thin, narrow and miniaturized. so it is desirable that the optical reading mechanism and the driving mechanism can occupy less space. 
     FIG. 1 shows a conventional technique. The components include a contact image sensor (CIS)  120 , a stepping motor  132 , a gear train  134 ,  136  (only two gears shown for brevity), an idler  136 , a belt  130  for moving the CIS  120  and a guide rail (not shown). 
     The working principle of the image scanner is as follows: Referring to FIG. 1, a document to be scanned is placed on a glass window  110 . The contact image sensor  120  converts the image signal into digital signals, which are fed to an image processor (not shown) and then to a computer for further processing. When the CIS  120  reads a row of image signals, the driving mechanism moves the CIS  120  to another scanning successively until the complete image is scanned. 
     Structurally, the conventional technique has the driving mechanism, the stepping motor  132  and the gear train  134 ,  136 , the idler  138  installed in fixed positions on the frame (not shown). The belt  130  is attached to the CIS  120  at a certain point, and moves the CIS in directions indicated by the arrowheads  140 . Such a structure occupies a great deal of space, and uses a great deal of material. 
     SUMMARY 
     An object of this invention is to reduce the size of a flat bed image scanner. Another object of this invention is to save material for the construction of the flat bed image scanner. 
     These object are achieved in this invention by combining the driving mechanism and the reading sensor in the same scanning 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 glide back and forth along a track 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 between a gear and a grooved belt or a gear and a grooved frame The force can also be exerted through a wire or a ribbon fixed at two ends and wrapped around a wheel on the movable module. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a prior art structure of a flat image scanner. 
     FIG. 2 shows a rack and pinion mechanism between a gear and a grooved belt for moving a combined driver and sensor scanning module. 
     FIG. 3 shows an enlarged view of the contact between the gear and the grooved belt shown in FIG.  2 . 
     FIG. 4 shows another embodiment of the present where the transport mechanism is accomplished by means of a wire fixed at two ends and wrapped around the combined driver and sensor scanning module. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In this invention the driving mechanism shown in FIG. 1 is totally altered to a new design. FIG. 2 shows the structure of the present invention. The contact image sensor  220  and the stepping motor  232  are integrated into an “integrated image reading and driving module”, which moves as it scans. This integrated image reading and driving module depends on the gear train  234 ,  236  to control the speed. The gear  236  is driven by a belt  230 . The ends of the belt  230  are fixed at points  238 , and the belt itself does not move. When the gears train  234 ,  236  turns, the attached image read driving module moves back and forth along the direction of the arrowheads  240  in parallel with the belt and performs the function of scanning. 
     In comparison with conventional flat-bad image scanner, this invention has the following advantages: 
     In terms of space, the structure of this present invention saves the space occupied by the stepping motor  132 , the gear train  134 ,  136  and the idler  138 . The invention also saves the space and the material used up by the belt. 
     In terms of motion, belt  130  is a closed loop, while the belt  230  of this invention is fixed at two ends. 
     In terms of structure, the conventional belt has the contact image sensor attached at a fixed position. In this invention, the teeth of the idler  236  driven by the integrated reading and driving module engage the teeth of a fixed belt, so as to move the integrated reading and driving unit back and forth. 
     FIG. 2 shows the first embodiment of the present invention. The integrated reading and driving unit has the stepping motor  232 , gear train  234 ,  236  mounted in fixed position relative to the contact image sensor  220  as a single unit. The gear train  234 ,  236  exerts force on the belt  230  which is fixed at the two ends  238 . 
     FIG. 3 shows an enlarged view of how the gear  236  engages the belt  230 . The grooves  2362  on the gear  236  engage the grooves  2302  on the belt  230 . Then the gears  236  turns, the reaction force supplied by the grooves  2302  on the belt  230  drives the integrated reading and driving module back and forth. 
     The invention attaches the stepping motor  232  and the gear train  234 ,  236  on the contact image sensor. Thus, the space near the contact image sensor is fully utilized to reduce the overall volume of the scanner to be smaller than a conventional flat bed scanner. At least, the space occupied by the stepping motor  132 , the gear train  134 ,  136 , the idler  138  and the belt can now occupy half as much space. In addition, due to the reduction in component counts, the reliability can be improved and the cost of the product can greatly be reduced. 
     The feature of this invention is that the element receiving the driving force is stationary. In the previous embodiment of the present invention, the element receiving the force is a belt. In a second embodiment of this invention, the belt is eliminated. The element for receiving the driving force is directly built on the frame of the scanner. Thus the space and cost of the belt used in the first embodiment is further reduced. 
     In comparison with the conventional scanner shown in FIG. 1, this embodiment has at least the following advantages: 
     In terms of components, the idler  138  and belt  130  are eliminated. 
     In terms of space, this embodiment saves the space occupied by the stepping motor  132 , the gear train  134 ,  136 , the idler  138 , and the belt  130 . 
     In terms of motion, the belt  130  in the prior art is a moving, closed loop. This embodiment utilizes the unitary structure of the frame to receive the driving force. The technique and design principle are totally different from conventional design by using a motionless belt. 
     In terms of structure, the belt  130  in a conventional structure uses a belt which is a moving closed loop. This invention uses the frame of the scanner to receive the driving force. The technique and design are totally different from conventional ones. 
     FIG. 4 shows a third embodiment of the present invention. The element receiving the driving force is a thin wire  410  or a ribbon with low index of elasticity. The thin wire or ribbon is fixed at two ends  422 , which is fixed on the frame of the scanner or another frame mounted on the main frame, and is wrapped at least one turn around a driving roller or friction wheel  406 . When the driving force is exerted, the roller or friction wheel  406  utilizes the reaction force to move the integrated reading and driving module back and forth along a guide. To implement the scanning function. The gear train  402 ,  404  transmits the driving force from the motor to the roller or friction wheel  406 . 
     In comparison with conventional technique shown in FIG. 1, this embodiment has at least the following advantages: 
     In terms of component count, this embodiment does not use the idler  138 , and the belt is substituted by a tight line  410 . 
     In terms of space, this embodiment saves the space occupied by the idler  138  and the major space occupied by the belt  130 . 
     In terms of motion, the conventional technique uses a moving, closed loop belt. This invention uses a tight wire to receive the driving force and is totally different from the conventional technique of using a moving belt. 
     In terms of structure, the conventional technique uses a moving, closed loop belt. This embodiment used a non-elastic wire or ribbon, which is fixed on to the frame of the scanner or another fixed frame, to receive the driving force. The technique and design principle is totally different from conventional ones. 
     The foregoing embodiments are preferred examples of the present invention and are not limited to these examples. For instance, the engagement of the gear and the grooves of the belt can be replaced with roller and friction tape or gear and corrugated tape. All these equivalent modifications are all within the scope of this invention.