Abstract:
Sheets ( 12, 14 ) of a medium stored in a stack ( 10 ) are separated and fed into an office machine. The edge of the top sheet ( 12 ) is lifted off the corresponding edge of the following second sheet ( 14 ). At least one separator ( 26 ) is inserted into the gap ( 32 ) resulting from the lifting of the top-sheet ( 12 ) and the top sheet ( 12 ) is lifted by the separator from the following sheet ( 14 ). This causes a reduction of the friction between the top sheet ( 12 ) and the following sheet ( 14 ) during separation of the top sheet ( 12 ), so that the electrical charge of the sheets ( 12, 14 ) generated by this friction is minimized.

Description:
PRIORITY  
       [0001]     This application claims priority to German application no. 103 38 365.4 filed Aug. 21, 2003.  
       TECHNICAL FIELD OF THE INVENTION  
       [0002]     The present invention relates to a procedure for the individual feed of media sheets as well as a device for the individual feed of media sheets.  
       DESCRIPTION OF RELATED ART AND BACKGROUND OF THE INVENTION  
       [0003]     Most office machines such as copiers, printers and similar devices generally use media in sheet form. This media, generally paper sheets, is normally stored in stacks. From this stack, individual sheets are pulled and fed into the office machine. By pulling the top-most sheet off the stack, friction between the top-most and the following sheet in the stack is generated. This friction causes an electrostatic charge of the touching sheets. This electrostatic charge depends on the environmental conditions like temperature and humidity as well as the sheets&#39; surface and material characteristics. The electrostatic charge causes the sheets to stick to each other, which can make separating the top-most sheet from the stack difficult.  
       SUMMARY OF THE INVENTION  
       [0004]     The invention is based on the task to reduce the interfering influence of the electrostatic charge in order to be able to pull single sheets from the stack.  
         [0005]     The invention solves this task by a procedure for separation of sheets of a medium for feeding to an office machine, with which the sheets are kept in a stack and the top-most sheet of the stack is lifted from the following sheet on the stack at the front edge facing the transport direction and then fed to the office machine, comprising the steps of moving at least one elongated separator from the front side of the stack facing the feed direction into a gap which is formed by the lifted edge of the top sheet and the corresponding edge of the following sheet, and pushing the separator in the opposite direction of the feed direction between the top sheet and the following sheet, in order to separate the top sheet from the surface of the following sheet, while the top sheet is lifted.  
         [0006]     The top sheet may rest at least partially on a separator while it is being fed to the machine. At least one separator may conduct electricity and can be grounded. The at least one separator can be driven by a motor.  
         [0007]     The object can also be achieved by a device for separation of sheets of a medium for feeding to an office machine, with which the sheets are kept in a stack and the top-most sheet of the stack is lifted from the following sheet on the stack at the front edge facing the transport direction and then fed to the office machine, comprising: devices for lifting the front edge of the top sheet facing the feed direction from the following sheet, and at least one tongue-shaped band separator at the front side of the stack facing the feed direction which can be pushed from the front edge of the stack in the opposite direction of the feed direction into the gap formed by the lifted edge of the top sheet and the following sheet, in order to separate the top sheet from the following sheet, while the top sheet is lifted.  
         [0008]     A pusher may grab the top sheet and the top sheet may be pushed against the sheet stopper, which lifts the edge of the top sheet. The pusher can be a flex device which traverses the top sheet with freely movable feed rollers. The sheet stopper may comprise at least one continuously moving belt and the pusher may push the top sheet with its edge against the part of the at least one belt that moves upwards substantially vertically to the sheet plane. The tongue-shaped band can be a steel band of small material thickness with a cross-section profile that causes an axial stiffening of the band. The separator can be equipped with a gliding tip. At least one separator can be so long that it can be inserted in feed direction almost over the entire length of the stack. Two separators can be used at certain distances to each other and perpendicularly to the stack&#39;s edge. The at least one separator may conduct electricity or may use a conducting coating and can be grounded. The at least one separator can be driven by a motor. The motor drive of the at least one separator can be controlled in such a manner, that the separator is inserted at high speed between the top sheet and the following sheet and is removed from the inserted position to the home position at a speed that corresponds to the pull-off speed of the top sheet.  
         [0009]     The main idea of the invention is to insert at least one separator between the top-most sheet and the following second sheet in the stack, before the top-most sheet is pulled from the stack. By using a separator, the top-most sheet is separated from the following sheet&#39;s surface. When the top-most sheet is pulled from the stack, the friction between the top-most and the following sheet is considerably reduced.  
         [0010]     By using a separator, the top-most sheet is at least partially lifted off the following sheet. Doing so enables air to enter the space between the top-most and the following sheet. The air works as a pad, on which the top-most sheet can float and can be pulled effortlessly and without much friction.  
         [0011]     In one preferred embodiment, the top-most sheet can be lifted off the following sheet almost entirely due to at least one separator. This reduces the friction between the top-most and the following sheet during the paper feed and minimizes the electrostatic charge caused by the friction.  
         [0012]     In one preferred embodiment, the separator has the shape of an elongated tongue which is inserted into the gap created by the edge of the top-most sheet and the following sheet. The tongue-shaped separator can be so long that it covers the entire length of the sheets that need to be separated. The separator separates the top-most sheet on its entire length from the following sheet. In order to achieve optimum separation over the width of the sheet as well, two or more tongue-shaped separators are to be used. These separators are inserted parallel to each other and side by side over the width of the stack. This ensures that the top-most sheet is separated from the following sheet more or less over its entire surface area. When the topmost sheet is pulled off the stack, it basically rests on the tongue-shaped separators, almost completely preventing it from causing friction with the following sheet.  
         [0013]     In one advantageous embodiment, the separator (at least one) is an electrical conductor and is grounded. All generated electrostatic charges are then derivated via the separator and/or separators. To do so, the separator can consist of or can be plated with a metal that conducts electricity.  
         [0014]     In one preferred embodiment, the tongue-shaped separator consists of a metal band, especially a steel band. This band can be of minimal material thickness, which ensures low mass inertia of the separator. Due to the curving of the band&#39;s cross-section profile a sufficient rigidity of the tongue-shaped separator can be achieved even at a small material thickness, as known from steel measuring tapes. Due to the low mass and rigidity of the tongue-shaped separator, the separator can be inserted between the sheets using a motor and at high speeds, so that the separation cycle is not slowed down by separator insertion.  
         [0015]     The procedure according to the invention can be used for all known separation applications, for which one edge of the top sheet is first lifted off the following sheet, so that a gap between the top sheet and the following sheet is created along this edge. The separator can be inserted into this gap. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     The invention is further explained below using the embodiment shown in the figure. The figures show:  
         [0017]      FIG. 1 a  side view of a separation by using a separator at the beginning of the separation procedure, and  
         [0018]      FIG. 2 a  corresponding view with the separator inserted. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]     In order to feed media (e.g. paper sheets) to an office machine such as a printer or copier, the sheets are stored in a stack  10 . The top sheet  12  of stack  10  is separated from the following second sheet  14  in the stack and fed to the office machine (not depicted).  
         [0020]     If a sheet is about to be fed to the machine, a command-controlled pusher  16  is set onto the top sheet  12  of stack  10 . The pusher  16  in the embodiment depicted is a flex device such as is described in DE 100 16 793 C2. The pusher  16  is equipped with feed rollers  18  on a belt that is constantly moving. The feed rollers are moved under pressure over the top sheet  12  in the direction of the paper feed, i.e. from left to right in the figure. The feed rollers  18  apply pressure on the top sheet  12  and reduce pressure on the following sheets in the stack. By using this pressure, the top sheets  12 ,  14  etc. in stack  10  are pushed forward in a scale-like fashion, i.e. the top sheet  12  is pushed forward the strongest, the following sheets  14  etc. increasingly less. This scale-like fanning of the top sheets of stack  10  can be seen in  FIG. 1 .  
         [0021]     In the feed direction of the sheets  12 ,  14  etc. in front of the stack  10 , there is a sheet stop  20 . The pusher  16  moves the sheets towards this stop. In the embodiment shown, the sheet stop consists of the constantly driven belt  22 . Several of these belts can be found distributed along the front end of stack  10 . at certain distances from each other. In the figure, the belts  22  are moving in a clockwise direction. The part of the belts  22  which is positioned towards the stack  10  moves upward vertically in front of the front edge of stack  10 .  
         [0022]     Due to the scale-like fanning of the upper sheets on stack  10  achieved by the pusher  16 , the front edge of top sheet  12  (i.e. the right edge in the figure) reaches the belts  22  first. Due to the fact that the front edge of the top sheet  12  contacts the upward-moving part of the belts  22  because of the pusher&#39;s  16  pushing pressure, the front edge of the top sheet  22  is being moved upwards by the belts  22  and is lifted from the front edge of the following sheet  14 , as shown in  FIG. 1 . The upper part of the upward-moving part of the belts  22  slightly deviates from the vertical, so that it is slightly inclined towards the stack  10 . This leaves the front edge of the top sheet  12  under pushing pressure and contacting at the belts  22 , even if the front edge of the top sheet  12  moves up.  
         [0023]     The upper deflection rollers of the belts  22  are fitted with counter rollers  24  from above. When the front edge of the top sheet  12  reaches the upper deflection point when conveyed by the belts  22 , the front edge of the top sheet  12  is grabbed by the upper deflection rollers of the belts  22  and the counter rollers  24  and transported in the direction of the feed, as shown in  FIG. 2 . The top sheet  12  is pulled from the stack  10  and separated from the following sheet  14  and fed into the office machine.  
         [0024]     In order to prevent the friction between the top sheet  12  and the following sheet  14  during pulling of the top sheet  12  from the stack  10  creates an electrostatic charge between these sheets  12  and  14  and an electrostatic adhesion of the sheets, the device described below is used.  
         [0025]     One or more separators  26  are located in front of the stopper-side front edge of the stack  10 . The separators  26  are shaped like elongated, tongue-shaped bands. In the preferred configuration, the separators are narrow steel bands of low material thickness with a cross-section profile that is slightly vaulted in order to give these steel bands the necessary axial rigidity. Steel bands such as these are used in measuring tape applications, for example. A gliding tip  28  (plastic, felt or similar) can be put on top of the separator  26  ends facing the stack  10  in order to prevent the sheets from being damaged by the separator  26 .  
         [0026]     The tongue-shaped separators  26  are placed in such a manner in front of stack  10 , that their length axis corresponds to the direction of the paper feed through the pusher  16 . During standby, which is shown in  FIG. 1 , the separators&#39;  26  plastic tips  28  are outside of the stack  10 , with the vertical position of the plastic tips  28  corresponding to the upper edge of stack  10 . From the standby position as depicted in  FIG. 1 , the separators  26  can be driven by motor and moved against the stack  10 . The drive is shown in the figure by command-controlled driven friction rollers  30  which frictionally engage the steel band of the separators  26  and advance it. The length of the separator  26  is such that the separators can reach the back edge of the stack  10  with their plastic tip  28  when they are pushed forward against the stack (in the figure towards the left). In the preferred configuration, two separators  26  are used. They are offset perpendicularly in relation to the plane and to the front edge of stack  10  and are located at positions which correspond to a third or to two thirds, respectively, of the width of stack  10 . The separators  26  are aligned with the belt  22  gaps, so that they can be moved between the belts  22  towards the stack  10 .  
         [0027]     When the office machine issues a sheet request, the pusher  16  is activated and put on the top sheet  12  of stack  10 . The top sheet  12  is pushed by the pusher  16  towards the belts  22  of sheet stopper  20 . The upward-moving belts  22  lift the front edge of the top sheet  12  from the offset following front edge of the following sheet  14 , as shown in  FIG. 1 . This creates a gap  32  between the front edge of the top sheet  12  and the front edge of the following sheet  14 .  
         [0028]     As soon as a sensor senses that the front edge of the top sheet  12  is captured between the upper deflection roller of the belts  22  and the counter rollers  24 , as shown in  FIG. 2 , the pusher  16  is lifted off the top sheet of the stack, and the separators  26  are pushed at high speed by the friction rollers  30  from the standby position depicted in  FIG. 1  to the left and against the stack  10 . The plastic tips  28  penetrate the gap  32  between the top sheet  12  and the following sheet  14  and the ribbon-shaped separators  26  are inserted over the entire length of the stack between the top sheet  12  and the following sheet  14 , as shown in  FIG. 2 .  
         [0029]     Since the two separators  26  are inserted between the top sheet  12  and the following sheet  14 , the top sheet  12  is separated on its entire surface area from the following sheet  14 . When the top sheet  12  is pulled off, it rests mainly on the separators  26  and not on the following sheet  14 , so that the friction between the top sheet  12  and the following sheet  14  is reduced considerably and no electrostatic charge is created. If a residual friction remains and a small electrostatic charge is generated, it is deviated via the conducting steel bands of the separators  26 . For this reason, they are grounded at the end not visible in the figure.  
         [0030]     Once the separators  26  have reached their final position as shown in  FIG. 2 , in which they have separated the top sheet  12  from the following sheet  14 , the separators are removed until they reach the standby position as shown in  FIG. 1 , in which they are ready for the next separation cycle. The separators are inserted at a high speed between the top sheet  12  and the following sheet  14 , so that the top sheet  12  can be separated as fast as possible from the second sheet  14  once the top sheet has been grabbed by the counter rollers  24 . The return movement of the separators  26  to the standby position is executed at a lower speed and is synchronous to the pull speed of the top sheet  12 , so that there is no relevant relative speed difference between the top sheet  12  and the separators  26 .