Patent Publication Number: US-2007108289-A1

Title: Bar code scanner and method of manufacturing a bar code scanner

Description:
FIELD OF THE INVENTION  
      The present invention relates to a method of manufacturing a bar code scanner.  
     BACKGROUND TO THE INVENTION  
      Bar code scanners generally have a light source which shines a beam of light onto a bar code being read. The light reflected from the bar code is then sensed with photodetector. The light source may be a laser or a light emitting diode and a lens is conventionally used for focusing the beam on the bar code. Similarly, a lens is also commonly used to focus the reflected light onto the photodetector.  
     SUMMARY OF THE INVENTION  
      It is an aim of the present invention to provide a bar code scanner that does not employ lenses.  
      According to the present invention, there is provided a bar code scanner comprising a light transmissive slit, light source means for directing a beam through said slit and light detector means for detecting light from said beam reflected back through the slit, wherein the slit is arranged for being brought into proximity to a bar code for scanning thereof. The slit need not have a particularly high aspect ration. However, it should be narrow where the major part of the light from the light source passes through it. The slit need not be parallel-sided and may be, for example, dumbbell-shaped. The slit need not comprise an aperture. The important characteristic is its light transmissivity.  
      The light source means may be configured for directing said beam through the slit such that the beam path through the slit lies in a plane substantially aligned with the slit. The light source means may be configured to direct light obliquely through the slit.  
      The light detector means may be configured for sensing reflections of said beam following a path through the slit that lies in a plane substantially aligned with the slit. The light detector means may be directional and arranged such that it is directed along a line substantially normal to the slit.  
      The combination of oblique illumination and the sensing of light reflected normal to the slit provides protection against false reading of glossy bar codes.  
      The slit is formed in a metallic element, for example a stainless steel. However, other materials that can be finely worked, such as brass, can be used.  
      The scanner may be handheld so that the scanning action is performed manually by moving the scanner. Alternatively, the scanner may be mounted in a fixed position so that bar codes can be manually or mechanically propelled past the scanner to provide the scanning action. The scanner could also itself be mechanically moved past bar codes for scanning.  
      The scanner may include a panel by which a sheet can be passed, the panel having an aperture through which the slit is exposed. The panel need not be flat. There may also be a member, having a dished portion received in the aperture, with the slit formed in an opaque element that is accommodated in the dished portion.  
      The width of the slit may be in the range 0.2 mm to 0.4 mm and is preferably 0.3 mm.  
      The separation of the openings of the slit is in the range 0.05 to 0.1 mm and is preferably 0.075 mm.  
      According to the present invention, there is provided a sheet validator including a sheet path along which a sheet to be validated is passed and a bar code scanner, according to the present invention, located for scanning a bar code on a sheet passing along the sheet path.  
      According to the present invention, there is also provided a method of method of manufacturing a bar code scanner comprising forming a light transmissive a slit and mounting the slit with respect to a light source means and a light detector means, such light from the light source can pass through the slit and light from the light source that is reflected back through the slit can be detected by the light detector means.  
      Preferably, the slit is formed by chemically etching a thin metallic element.  
      According to the present invention, there is further provided a method of manufacturing a sheet validator including a bar code scanner, the method including a bar code scanner manufacturing method according to the present invention for manufacturing said bat code scanner. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic side view of a sheet validator unit;  
       FIG. 2  is a partially cut away side view of the sheet validation and storage unit of  FIG. 1 ;  
       FIG. 3  is a section view of the bar code scanning station of the unit of  FIG. 1  viewed from the entry slot of the validator of  FIG. 1 ;  
       FIG. 4  is a bottom view of the bar code scanning station shown in  FIG. 3 ;  
       FIG. 5  shows a sheet with a bar code printed on it; and  
       FIG. 6  illustrates a manufacturing process of manufacturing sheet validators. 
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENT  
      An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:  
      Referring to  FIGS. 1 and 2 , a sheet validator  1  comprises a main body  2  and a removable storage box  3 . The unit  1  is substantially the same as the WACS 5 note validator available from Money Controls plc.  
      The main body  2  has a vertical portion  2   a  and a horizontal portion  2   b  projecting from the bottom of the vertical portion  2   a.  A sheet entry slot  4  opens through a bezel  5  at the distal end of the horizontal portion  2   b.  A sheet transport path  6  extends through the horizontal portion  2   a  and down the vertical portion  2   a.  Sheets are transported through the horizontal portion  2   a  by driven wheels  7  (only one shown by way of illustration) and belts (not shown), driven by a motor (not shown).  
      Sheets are transported down the vertical portion and, if determined to be valid, are driven transversely into the storage box  3 . Sheets determined to be invalid are reversed back out of the entry slot  4 .  
      A bar code scanning station  12  mounted to a PCB  13  located above and parallel to the sheet path in the horizontal portion  2   b.  There may be addition optical and/or magnetic sensors for conventional validity determination and sheet transport control.  
      The PCB  13  includes circuitry for processing sensor signals, including signals from the bar code scanning station for input to a processor (not shown) for note validation and sheet transport control.  
      Referring to  FIGS. 3 and 4 , the bar code reading  12  station comprises a opaque locating block  14 , a infrared LED  15 , a phototransistor  16 , a cover  17  and a thin metal plate  18 . The phototransistor  16  sits on the PCB  13  and its leads are soldered to tracks on the other side of the PCB  13 . The leads of the LED  15  are soldered on the same side of the PCD  13  as those of the phototransistor  16 . However, the LED  15  does not sit on the PCB  13  and is supported within the locating block  14 .  
      The PCB  13  is fixed by screws (not shown) to the upper wall  21  of the sheet path bar code scanning station  12  is clamped between the upper wall  21  of the sheet path and the PCB  13 .  
      The cover  17  is moulded from a transparent plastics material and comprises a rectangular plate  17   a  that has a rounded rhombic dished portion  17   b.  A pair of legs  17   c  project from diagonally opposite corners of the plate  17   a  and the free ends of the legs  17   c  bear against the under side of the PCB  13 . The dished portion  17   b  is received snugly in a rhombic aperture in the upper wall  21  of the sheet path.  
      The locating block  14  is located between the cover  17  and the PCB  13  and comprises a main portion  14   a  and a press-fitted cover portion  14   b.  The cover portion  14   b  has a pair of small lugs (not show) that are received by apertures (not shown) in the side walls of the main portion  14   a  to retain the cover portion  14   b  in position.  
      A pair of ridges  14   c  project from the bottom of the main portion  14   a  and are received in the dished portion  17   b  of the cover  17 . The ends of the ridges  14   c  are chamfered for locating the locating block  14  relative to the cover  17 . The ridges  14   c  extend from one end of the locating block  14  to a position somewhat short of the other end of the location block  14 , which overhangs the planar part of the cover  17 .  
      A channel extends transversely across the underside, in the orientation shown in  FIG. 3 , of the main portion  14   a  of the locating block  14 . The floor of the right hand part of the channel, in the orientation shown in  FIG. 3 , is flat while the floor of the left hand part has a semi-circular cross-section and slopes towards the PCB  13 . When the cover portion  14   b  is fitted in place, the upper side of the cover portion  14   b  and the left hand part of the channel define a sloping circular-section passageway in which the LED  15  is received.  
      The phototransistor  16  is received in a circular-section passageway the extends through the main portion  14   a  from its upper face to the floor of the channel in the right hand part thereof. The passageway holding the phototransistor  16  is arranged to extend normal to the PCB  13  and the sheet path  6 .  
      A thin metal plate  18  is rhombic and conforms to the dished portion  17   b  of the cover  17  in which it is located. The plate  18  has a thin transverse slit  19  extending across the plate  18  between positions close to the sharper corners of the plate  18 . The plate  18  is 0.075±0.025 mm thick and the slit is 0.3±0.1 mm wide.  
      In use, a sheet  31  bearing a longitudinal bar code  32 , as shown in  FIG. 5 , is driven past the bar code scanning station  12 . The LED  15  shines light onto the bar code  32  as it passes under the slit  19 . The light from the LED  15  is reflected from the sheet  31 . However, the level of reflected light from dark bar code elements  32   a  is negligible compared to the level of reflected light from light bar code elements  32   b.  The reflected light is sensed by the phototransistor  16  which produces an electrical output dependent on the incident light level. Thus, the output of the phototransistor  16  varies with the reflectivity of the bar code portion aligned with the slit  19 . The output of the phototransistor  16  is processed in a conventional manner.  
      It should be noted that the LED  15  shines light through the slit  19  obliquely whereas the phototransistor  16  is arranged to sense light reflected normal to the sheet  31  bearing the bar code being read. Consequently, glossy dark bar code elements  32   a  are not erroneously determined to be light elements  32   b.    
      A method of manufacturing a sheet validating apparatus will now be described with reference to  FIG. 6 .  
      The portions  14   a,    14   b  of the locating block  14  are moulded using a conventional technique in a locating block moulding operation  101  and the PCB  13  is assembled in a PCB assembly operation  102 . The PCB assembly operation  102  comprises soldering electronic components, including the LED  15  and the phototransistor  16 , to the PCB  13  itself.  
      The locating block  14  is then added to the PCB assembly in a locating block mounting operation  103 . In the locating block mounting operation, the main portion  14   a  is pushed over the phototransistor  16  so that the phototransistor  16  is lodged in the circular-section passageway though the main portion  14   a  and the main portion  14   a  tests against the PCB  13 .  
      The LED  15  is introduced into the sloping part of the channel and the cover portion  14   b  is then pressed into place to retain the LED  15  in position.  
      The cover  18  is moulded in a covert moulding operation  104  using a conventional technique.  
      The plate  18  is formed in an etching operation  105  by etching a sheet of stainless steel using a photochemical etching process.  
      The upper wall  21  of the sheet path is moulded in an injection moulding operation  106 .  
      The components produced in operations  101  to  106  are assembled together in an assembly operation  107 . In the assembly operation  107 , the cover  18  is positioned on the upper wall  21  with its dished portion  18   a  projecting into the rhombic aperture in the upper wall  21 . The PCB assembly is then offered up to the upper wall  21  and fixed using screws. This locates the locating block  14  correctly with respect to the cover  18 .  
      The other components of the validator, including control and validation electronics and sheet handling mechanical and electromechanical components, are formed in a set of operations  108 .  
      Finally, the validator is assembled from the components and sub-assemblies available after operations  107  and  108  in an final assembly operation  109 .  
      It will be appreciated that many modifications may be made to the embodiment described above. For example, the plate may be formed by laser cutting or punching instead of etching. The plate and the cover need not be rhombic and the bar code scanning station could be positioned under the sheet path.