Abstract:
A feed roller is provided for use in a feed roller assembly for intermittently feeding sheets. The feed roller has a body having a cross-section including an arc portion forming a partially cylindrical configuration. A support member is coupled to the body on at least one side of the body. A distance roller is rotatably supported by the support member relative to the body. The distance roller is spaced apart opposite the arc section parallel to the body.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   Benefit is claimed of U.S. patent application Ser. No. 60/772,082, filed Feb. 10, 2006, and priority is claimed of German patent application 20 2006 002 248, the disclosures of which are incorporated by reference herein as if set forth at length. 

   BACKGROUND OF THE INVENTION 
   The invention relates to a feed roller, a feed roller assembly for intermittently feeding sheets, and a sheet handling system. 
   A feed roller and a feed roller assembly of the mentioned kind are well known in the art. As listed below some of these provide a preceding glide shoe or a side-mounted distance roller for the feed roller. The prior art feed rollers, however still have significant drawbacks. 
   In U.S. Pat. No. 5,372,359 a gliding shoe is pressed onto the pad. There is a comparatively high coefficient of friction to the pad. This results in: a higher force to drive; a speed limitation with regard to the throughput; and possibly a squeaking noise during separation. 
   Prior art rollers with side-mounted distance roller are known as a feed roller having a side-mounted distance roller or a feed roller with a distance roller mounted on each side or a feed roller the axle of which has a distance roller for the chord portion on each side of the feed roller. Side-mounted rollers or members are disclosed in JP3162331 A, JP2132025 A, JP1321225 A, and U.S. Pat. No. 4,437,656. 
   Disadvantages of side-mounted preceding distance rollers or cam shaped members which are side mounted are as follows. The preceding distance roller fixed and restricted to one or both sides of the feed roller is, in principle, intended to hold a retard pad in an appropriate circular distance to the feed roller&#39;s arc portion by the time the nose piece of the feed roller is pulling one or several sheets from the lift plate onto the retard pad. But the side-mounted members or rollers will cause the sheets to rise at their center, which is disadvantageous and may, in the worst case, even cause a paper jam. Consequently the problem arises to improve sheet feeding, in particular reliability thereof, whereas still a friction for feeding a sheet should be as low as possible. 
   This is where the invention comes in, the object of which is to specify a feed roller, a feed roller assembly, and a sheet handling system which have improved reliability of sheet feeding and lower friction for sheet feeding operation. 
   SUMMARY OF THE INVENTION 
   The object is achieved by the feed roller, the feed roller assembly, and the sheet handling system mentioned in the introduction, wherein in accordance with the invention it is proposed that the feed roller comprises: a body having a cross section comprising an arc portion and a chord portion to substantially form a semicylindrical configuration; a support member connected to at least one side of the body; and a distance roller provided freely rotatable at said support member. The distance roller is spaced apart in a distance opposite said chord portion and extends along an axis of said body. 
   The concept of the instant invention applies a distance roller basically extending along the total axis the feed roller. The rotatable body of the distance roller has no contact to the chord portion of the feed roller. The rotatable body guarantees that the contact to the papers is restricted to a single line basically extending along the axis of the feed roller. There is a contact gap between said contact line of the body of the distance roller and a leading portion, i.e. nose part of the frictive part of the feed roller. These and other measures make sheet feeding more reliable and less frictive. In particular the prior art problems as mentioned in the introduction are avoided. 
   According to the concept of the invention, a sudden impact on the retard pad by the feed roller&#39;s nose piece during the transition of the chord portion to the arc portion of the feed roller at a feed start is avoided. The preceding distance roller extending along the total axis of the feed roller is depressing the retard pad to a radius equal or similar to the radius of the nose part of the feed roller when it gets in contact with the paper. This is done without the risk of rising of the paper of affecting the paper disadvantageously in other ways. Moreover, as a distance member is formed as the distance roller feeding is performed basically without any friction. The pre-adjustment of the pad by means of the distance roller of the invention does enable a smooth transition of the uppermost paper onto the pad. 
   On the contrary when the transition of the retard pad&#39;s circular path is not adjusted to the nose piece of the feed roller double or even multipicks are to be expected as the retard pad all of a sudden is pushed down by the nose piece of the feed roller which is causing a small but unavoidable overshoot of the pad towards a higher circular path. This will open the gap between roller and the pad in a way which invite multiple sheets to be inserted into the gap. 
   With the proceeding roller this impact may be there as well, however, in general the pad will be in a stable position by the time the friction part of the roller is moving a paper on it. 
   Further objects and advantages of the invention will become apparent from the specification and accompanying claims and from the accompanying drawing. 
   For a more complete understanding of this invention, the invention will now be described in detail with reference to the accompanying drawing. The detailed description will illustrate and describe, what is considered as a preferred embodiment of the invention. It should of course be understood, that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is therefore intended that the invention may not be limited to the exact form and detail shown and described herein, not to anything less than the whole of the invention disclosed herein and as claimed herein after. Further the features described in the description, the drawing and the claims disclosing the invention, may be essential for the invention considered alone or in combination. Whereas the invention has particular utility for, and will described as associated with, a sheet feeding device for handling papers to be used in a copier, it should be understood that the system and its method of operation are also operable in association with other forms of sheet handling systems. For example, the system is also applicable for printers, scanners and paper separators and the like. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the invention reference should be made to the accompanying drawing, wherein: 
       FIG. 1  is a cutaway side view of a feed roller assembly according to a preferred embodiment of the invention. 
       FIG. 2  is a cutaway side view of a drive mechanism for the feed roller assembly of  FIG. 1 ; 
       FIG. 3  is a detailed cutaway side view of the feed roller of the assembly of  FIG. 1 ; 
       FIG. 4  is a front view of the feed roller of the assembly of  FIG. 1 ; 
       FIG. 5 ,  FIG. 6 ,  FIG. 7 , and  FIG. 8  illustrate a sequence of feed roller movement each in a detailed cutaway side view; 
       FIG. 9  is a graph showing the position of a pad as a function of time after contact with a distance roller according to the concept of the invention; 
       FIG. 10  is an enlarged cutaway side view of the feed roller, distance roller and pad, wherein the distance roller is still in touch with the pad; 
       FIG. 11  is an enlarged side view of the feed roller, distance roller and pad, wherein the distance roller has just left the pad; 
       FIG. 12  and  FIG. 13  are cutaway side views of two further embodiments of a feed roller in form of a wave generator roller. 
   

   Like reference numbers and designations in the various drawings indicate like elements. 
   DETAILED DESCRIPTION 
   The following specification discloses improvements on a sheet feeding device as shown in  FIG. 1  which is separating papers and substrates and the like for further use in paper handling devices such as copiers, printers, scanners and the like. The device includes a paper tray assembly  10  and a feed roller assembly  20 . The drawings are not to scale and various dimensions and spacings are exaggerated for ease of reference. The degree may vary figure-to-figure. 
   A sheet in form of a paper is usually deposited as a stack  14  on a loadable paper tray  11  or plate or the like which is biased to the feed roller assembly  20  by means of a spring  13 . The spring bias elevates a downstream end of the tray by pivoting the tray about an upstream pivot axis  500 . 
   The feed roller assembly  20  comprises a feed roller  21 , fixed to a rotatable drive shaft  23  for rotation about an axis  502 . The assembly  20  further comprises a pair of cylindrical free running rollers  24 , also referred to as idler rollers, coupled to the drive shaft  23  and disposed on opposite sides of the feed roller  21 . A pad  25 , also referred to as a retard pad, is mounted on a lever  18  springloaded by a spring  26  to be pressed against the feed roller  21  or the idler rollers  24  respectively. The exemplary retard pad  25  is mounted to a distal end of the lever, whereas a proximal end is pivotally mounted for rotation about a pivot axis  504 . 
   As shown in  FIG. 3  the feed roller  21  has a cross-section comprising an arc portion  40  and a chord portion  42 . Mantel  44  along at least the arc portion of the feed roller is of a resilient high friction material (e.g., a rubber). 
   As shown in  FIG. 4  the distance roller  27  is spaced apart from the feed roller direction beyond said chord portion  42  and continuously extends along a transverse span of the body of feed roller  21 . The distance roller has a periphery lying within the outer radius R 1  of the arc portion  40  of the feed roller  21 . The distance roller  27  is freely running for rotation about an axis  506 . The exemplary distance roller is mounted on an axle  28 , kept by axle supports  29  which are fixed to the core of the feed roller  21 . The length of the distance roller  27  essentially corresponds to the length of the feed roller  21  (e.g., the distance roller extends along the axle  28  along its total length). This avoids rising of a center of a paper during feeding operation. 
   As shown in  FIG. 4  the length L R  of the feed roller  21  is about 30 mm. Respectively the distance roller is of similar length. Of course the length of the distance roller  27  and the feed roller  21  may vary, in particular in a typical range between 25 mm and 35 mm. 
   As shown in  FIG. 3  the radius R 1  of the feed roller is about 19 mm. Other preferred embodiments may also use a radius in a range between 15 mm and 25 mm. In this embodiment the arc portion  40  extends on the surface of the feed roller  21  along an angle section θ 0  of an exemplary 225° leaving the portion  42  with an angle θ 1  of 135°. Exemplary θ 0  is 220° to 230°. Exemplary θ 1  is 130° to 140°. 
   The distance roller  27  has an exemplary diameter D of 10 mm. Other embodiments may have a diameter in a range of 8-12 mm or preferable in a range of 4-10 mm. 
   The distance roller  27  is arranged at a position opposite to said chord portion C near a leading edge (nose point)  48  of the arc portion  40 . An exemplary angle θ 2  between the distance roller  27  and the leading edge  48  is 25° in the embodiment of  FIG. 3 . Other embodiments may preferably use also an angle in a range between about 20° to 30°. Consequently the feed roller  21  is arranged to come into contact with a sheet of paper  15  along a contact line, said contact line being separated by a gap of no contact (i.e., essentially along the angle θ 2  to a second contact line basically in the area of the leading edge  48  of said arc portion  40 . Said contact line (or outer rim) of the feed roller  21  is located at a radius R 1  and an outer rim of said free running roller  24  is located at a radius R 2 , wherein R 2  is smaller than R 1 . However, the difference is only slight. In particular a preferred extremity of the distance roller may be characterized by the relation of R 2  and R 1 . In the instant embodiment R 2  amounts to about 99% of R 1 . Other preferred ranges of R 2  are 95-100% of R 1 , 98-100% of R 1  and 98.5-99.5% of R 1 . 
   As shown in  FIG. 1  the distance roller  27  is arranged to come into contact with the paper at feed start prior the feed roller&#39;s nose point  48  coming into contact with the paper. Running freely at least its surface material has a low coefficient of friction so to generally keep friction between the paper and the distance roller  27  low. 
   The predominant effect and functionality is described with reference to  FIGS. 5-8 . 
   During a feed cycle operation when the roller assembly  20  is turned continuously by means of a drive mechanism  50  ( FIG. 2 ) The drive mechanism  50  includes a motor-driven drive gear  52  engaged to a timing gear  54 . The mechanism  50  further includes a solenoid  56  activated by a feed start signal. The spring  13  lifts the tray leading edge so that the uppermost sheet  15  is in a position to engage the roller assembly  20  ( FIG. 6 ). As the roller assembly  20  rotates between the  FIG. 6  and  FIG. 7  orientations, the distance roller  27  is moved over the leading edge of the uppermost sheet  15 , slightly pressing the stack  14  down against the load spring  13 . 
   After being rolled over the leading edge of the uppermost sheet  15 —without or only slightly moving the sheet towards the output direction, the distance roller  27  comes into contact with the surface of the retard pad  25  (during transition between  FIGS. 7 and 8 ). 
   By this time the pad  25  slightly is being pressed down from the radius R 2  of the idler roller  24 , to the feed roller outer radius R 1 . 
   While the distance roller  27  still is traveling on the pad  25  the feed roller&#39;s nose point  48  is pulling the uppermost paper (or even some of the subsequent ones) from the paper stack onto the pad by means of its frictional connection. 
   With the retard pad  25  in a prepared height position as defined by the circular distance to the feed roller, the sheet(s) of paper smoothly get driven onto the pad  25  by the feed roller  21  ( FIG. 8 ). 
   As the surface of the retard pad  25  slightly is inclined with respect to the paper feed direction, the sheets  15  consequently get shingled out along the pads  25  surface. In this embodiment the pad has a length L P  of 20 mm. Other embodiments may use a preferred length of between about 18-22 mm. 
   By means of graduated frictional factors between feed roll  21 , retard pad  25  and the subsequent sheets  14  to come on the one hand and with the shingling effect of the retard pad  25  on the other hand only the uppermost paper  15  will make it to the exit rollers  30  ( FIG. 1 ), being dragged by the feed roller  21  against the resistance of the other sheets in the stack  14  or/and the retard pad  25 . 
     FIG. 9  shows the position of the retard pad  25  over time. 
   Before the distance roller  27  is reaching the retard pad  25  (position  520 ), the pad  25  is biased against the idler rollers&#39;  24  perimeter at R 2  which is slightly smaller than the perimeter at R 1  of the feed roller  21 . 
   Without the distance roller  27  the nose piece of the feed roller  21  firstly would have to push down the retard pad  25  at the entrance corner. As a consequence this would disadvantageously open the gap between the feed roller  21  and the pad  25  in a way that would occasionally allow too many sheets to enter the gap. As a result double or greater multipicks could be expected, as the retard pad  25  all of a sudden would be pushed down by the nose piece  48  of the feed roller  21 . This would cause an unavoidable overshoot of the retard pad with its lever mechanics towards a higher circular path with regard to the drive shaft axis  502 . 
   With the preceding distance roller  27  according to the concept of the invention the impact described above on the retard pad  25  may be there as well, however it will be much smaller (position  522 ). Also the pad  25  will be in a steady-state position (position  524 ) by the time the friction part  44  of the roller  21  is moving a paper  15  onto it. Between positions  522  and  524 ,  FIG. 9  shows a partial recovery of the pad position to a level between R 1  and R 2 . 
   Further advantages of the inventive concept are described as follows and may depend on the detailed configuration of the distance roller  27 . A first configuration provides a distance roller  27  preferably having a low coefficient of friction, so to essentially avoid any friction between the paper and the distance roller  27 . For this purpose, a single distance roller  27  is provided and at least the surface of the distance roller  27  is preferably made of a comparatively hard material preferably of a low coefficient of friction. The hard material may be chosen from the group consisting of steel, hard plastic material (e.g., polyamide (PA) or polyoxymethylene polyacetyl (POM)), and the like. Hard material preferably avoids a non-circular deformation of the distance roller  27  against the paper. 
   As a result after being rolled over the loading edge of the uppermost sheet  15 —basically without significantly moving the sheet  15  towards the output direction—the distance roller  27  is getting in contact with the retard pad&#39;s  25  surface. The functionality of this first configuration is described with reference to  FIG. 10  and  FIG. 11 , which illustrate a sequence of operation of the feed roller  21 , the distance roller  27  and the retard pad  25 .  FIG. 10  shows a situation of operation wherein the uppermost sheet  15  just is inserted onto the retard pad  25  by the feed roller  21 . The distance roller  27  is still in touch with the retard pad  25 , having opened the gap for the uppermost sheet  15  and possibly even several sheets. The spring force F 2  of the retard pad  25  may be subdivided between forces acting on a paper contact point P 1  (force F 2-1 ) and a distance roller contact point P 2  (force F 2-2 ). A particular preferred development of the inventive concept provides a pad shape of the retard pad  25  designed such that the impact of the distance roller  27  on the retard pad  25  is preferably lowered. In particular, by providing the pad  25  with a sloping surface the preferred development may provide that the impact of the distance roller  27  on the pad  25  is restricted to a smooth gliding onto the pad with the paper in between. Thereby, the impact as illustrated in  FIG. 9  is preferably lowered or even removed. In any case the operating position of the pad  25  will reach its working position ( 524 ) earlier than in prior art embodiments. In other words the pad time constant (5τ) is preferably reduced by the concept of the instant development. 
     FIG. 11  shows an operation situation wherein the distance roller  27  has just left the retard pad  25 . The retard pad spring pressure F 2  is now fully acting on point P 3 . This favors an effective shingling of sheets being inserted in the gap between the feed roller  21  and the retard pad  25 . In other words the above-mentioned gap of no contact (for instance angle range of  FIG. 3  providing angles θ 2  between about 20°-30°) preferably allows that the retard pad spring pressure F 2  is fully acting on an inserted paper as soon as possible. As a consequence just a single sheet is going to be fed to the exit roller assembly  20  and double or even multipicks are securely avoided. Thereby the concept of the instant invention is also superior to prior art concept using glide shoes or other kind of guide members as outlined in the introduction. 
   A second configuration provides a distance roller—also referred to as a wave generator roller—comprising two or more single rollers, which are arranged in a sequence on a support member  30 . The embodiment of wave generator roller  37 A shown in  FIG. 12  comprises three rollers  31 A,  33 A,  35 A of equal diameter. The embodiment of wave generator roller  37 B of  FIG. 13  comprises three rollers  31 B,  33 B,  35 B the diameter of which is increasing along the sequence in the movement direction of the wave generator roller  37 B. In principle, a wave generator roller  37 A,  37 B also achieves the above-mentioned advantages. Additionally the advantageous effects are achieved, which become clear from the following description with reference to  FIG. 12  and  FIG. 13 . Preferably the rollers  31 A,  31 B,  33 A,  33 B,  35 A,  35 B of a wave generator roller  37 A,  37 B have an extremely low coefficient of friction. In particular at least the surface of the rollers  31 A,  31 B,  33 A,  33 B,  35 A,  35 B may be made for this purpose from a hard material, e.g. steel, hard plastic material (e.g., PA, POM), or the like. 
   In the case a first roller  35 A,  35 B is not able to shingle a sheet  15  from the stack  14 ,—which may be due to a fast processing speed of the feed roller  41 A,  41 B—this will be accomplished and/or at least continued by a second roller  33 A,  33 B and/or a third roller  31 A,  31 B. In other words the wave generator roller  37 A,  37 B achieves a repeatedly processed preceding separation technique by means of the multiple—at least two—rollers. 
   While being rolled over the uppermost paper  15  the wave generator&#39;s roller  37 A,  37 B slightly is shingling nearly out all sheets below. Due to the hard material and the comparatively soft paper stack, a propelling effect is achieved on nearly all the papers, at least those in an upper position in the stack by means of a hard roller being pressed and rolled on them and the uppermost sheet  15  is shingled out most when treated accordingly—however, in this case only in the range of about 0.1-0.2 mm with respect to the next sheet in the stack. 
   Although the effective distance the roller  37 A,  37 B in this case is being moved over the paper is limited to about 10-15 mm due to the arc it describes, which corresponds to a relative difference of about 0.1-0.2 mm of the uppermost sheet  15  to the subsequent one, the propelling or shingling effect is such that the static coefficient of friction between the papers can be overcome—even in the case of heavy paper stock. Due to the hard roller&#39;s pressing multiple papers below the uppermost paper  15  are shingled up. 
   Moreover any “edge welding” of the sheets is overcome also by the slight displacement of the sheets. “Edge welding” involves poor cutting conditions of the individual sheets in a ream of paper which have a tangible burr in the cut direction when performed with a edgeless tool. In case the sheets of a ream accidentally are inserted into the tray such that the burr is directed upwardly and with in the leading edge in feed direction, multipicks result because the uppermost sheet is connected (welded) to the subsequent one. In this case only a preceding separation technique will help, which is able to separate two subsequent sheets just a short distance but with high shingling force. This is effectively performed by means of the wave generator. After having rolled over the leading edge of the uppermost sheet  15 , the wave generator roller  27  is getting in contact with the retard pad&#39;s surface. By this time the retard pad slightly is being pressed down from a radius of the idler roller to the roller outer radius R 1 . 
   What has been described above are preferred embodiments of the present invention. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present invention, but one of ordinary skill in the art will recognize that many further combinations and permutations of the present invention are possible. Accordingly, the present invention is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims.