Abstract:
A strike plate ( 266 ) against which sheets ( 150 ) exiting a printer contact prior to falling into a receiving tray, the strike plate comprising: a) at least one strike face ( 268 ); and b) a generally outward directed abutment surface ( 254 ) at an upper portion of the strike face, said direction being referenced to said strike face.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application incorporates by this reference all subject matter contained in PCT Patent Application Serial No. PCT/IL2003/000350, as filed on 30 Apr. 2003, and entitled “Strike Plate and Exit Section Utilizing Same”. This PCT application was published on 11 Nov. 2004 as International Publication No. WO 2004/096685 A1. 
     FIELD OF THE INVENTION 
     The field of the invention relates to strike plates that printed sheets contact after exiting a printer or copying machine seriatim so the sheets properly align in a sheet receiving tray. 
     BACKGROUND OF THE INVENTION 
     A printer or copier typically has a strike plate that a leading edge of a printed sheet contacts as it exits the printing machine, thereby halting the forward momentum of the sheet and aligning the sheet so that it falls, properly aligned, into a receiving tray. 
       FIGS. 1A and 1B  are schematic rendition of an exit section  100  of a printer or other device (not shown). After printing is completed, a printed sheet  150  moves in a direction  152  and a leading edge  170  contacts a strike plate  180 . Strike plate  180  serves to stop further motion of sheet  150  in direction  152  and align sheet  150  so that it falls flat into a stack of printed sheets  140  and/or sheet a receiving tray  102 . 
     When a sheet  150  hits plate  180 , ideally, the sheet should fall onto a tray  102 , completely aligned in both the forward and cross directions. Since sheets may not fall directly on each other in the tray a surface  160  may be used to straighten the substrates and place them against a front surface of the tray. Similar mechanisms may be employed to align the sheets in the cross direction. 
     However, when sheets  150  hit strike plate  180  they may not just stop and fall into place. Often, especially with light weight sheets, the sheets will curl down ( FIG. 1A ) or up ( FIG. 1B ). If the curl is large enough, the jogging will not be sufficient to both straighten and align the sheet and the sheet. 
     U.S. Pat. No. 4,667,949 shows an angled strike plate at a trailing edge of the sheet. The object of this plate is to force the trailing edge of a sheet toward the pile of sheets as it ricochets from strike plate  180 . 
     SUMMARY OF THE INVENTION 
     An aspect of some embodiments of the invention concerns providing an exit tray with a strike plate against which a sheet impinges, to stop forward motion of the sheet. In order to avoid curling of sheets hitting the plate, the plate has a substantially outwardly abutting, optionally substantially horizontal, surface at its upper edge, extending in a direction opposite to said forward motion. A sheet which curls upward will abut this edge and curling will be discouraged, so that it falls in a substantially flat configuration. Optionally any suitable abutment surface can be provided at the upper edge. 
     Alternatively or additionally, the plate has a substantially inwardly recessed surface at its lower edge, extending in the same direction as said forward motion. A sheet that curls downward will reach the end of the strike plate and, meeting no resistance, will no longer be encouraged by the strike plate to curl. This will encourage the sheet to fall in a substantially flat configuration. 
     Optionally, the strike plate forms a small angle with the vertical. Alternatively, the strike plate is vertical. Optionally, the angle of the strike plate is adjustable. 
     In some embodiments of the invention the strike plate is comprised of multiple strike steps, with each step offset along said motion direction of the paper with respect to a step above it. Thus, each strike step is situated between an inwardly recessed lower surface (the transition to the strike step below) and an outward facing upper surface (the transition to the strike step above). Thus, no matter which step the sheet strikes, upward or downward curling will be reduced. 
     In some embodiments of the invention, the surface of the strike steps is situated at an angle to the vertical. In particular, the present inventors have found that providing a front surface that is further recessed at its lower edge than at its upper edge by a small angle of under 15 degrees provides fewer fold-overs of the sheets, since it appears that very light papers have a tendency to ride upward (as shown in  FIG. 1B ). 
     In an embodiment of the invention the angle of the strike face of strike plate or the strike steps can be varied. This could be useful, for example, when printer handles different types of substrate. Since the optimum angle for the strike plate appears to depend on one or more of the weight and stiffness of the substrate, such optimization could reduce fold-over and jams in the system. 
     There is thus provided, in accordance with an embodiment of the invention, a strike plate against which sheets exiting a printer contact prior to falling into a receiving tray, the strike plate comprising: 
     a) at least one strike face; and 
     b) a generally outward directed abutment surface at an upper portion of the strike face, said direction being referenced to said strike face. 
     Optionally, the strike face is formed with an outwardly directed surface along its upper edge, said surface comprising the abutment surface. 
     Optionally, a lower edge of the strike face is not formed with an outward directed abutment face. Optionally, the lower edge of the strike face is formed with an inwardly directed surface. 
     In an embodiment of the invention, the strike face is substantially vertical. Alternatively, the strike face is at an angle of between −5 and +15 degrees with the vertical, where a positive angle denotes that the normal to the strike face is rotated downward with respect to the horizontal. Optionally, the strike face is at an angle of between +5 and +15 degrees. Optionally, the strike face is at an angle of about +10 degrees. 
     In an embodiment of the invention, the strike plate includes a plurality of strike faces that are offset from each other in the direction of motion of the sheet. 
     There is further provided, in accordance with an embodiment of the invention, a strike plate against which sheets exiting a printer contact prior to falling into a receiving tray, the strike plate comprising: 
     a plurality of strike faces that are offset from each other in the direction of motion of the sheet. 
     Optionally, a lower surface associated with one strike face forms an upper surface of a next lower strike face. 
     Optionally, the strike plate includes a rotator, operative to rotate the strike face so as to allow for a different angle with respect to the vertical, depending on the characteristics of the sheet used. 
     Optionally, the strike plate is the surface of a cylindrical portion of an object. Optionally, the cylindrical object is rotated about the axis of the cylindrical portion with respect to the vertical. Optionally, the cylindrical portion has a diameter of between 20 and 30 mm. Optionally, the cylindrical portion has a diameter of about 24 mm. 
     There is further provided, in accordance with an embodiment of the invention, an exit receptacle and a strike plate according to an embodiment of the invention. 
     There is further provided, in accordance with an embodiment of the invention, a paper handling system comprising an exit section according to an embodiment of the invention. 
     There is further provided, in accordance with an embodiment of the invention, an imager comprising: 
     an imaging section; and 
     an exit section according to an embodiment of the invention. 
     Optionally, the imaging section is a printer. 
     Optionally, the imaging section is a copier. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary non-limiting embodiments of the invention are described in the following description, read with reference to the figures attached hereto. In the figures, identical and similar structures, elements or parts thereof that appear in more than one figure are generally labeled with the same or similar references in the figures in which they appear. Dimensions of components and features shown in the figures are chosen primarily for convenience and clarity of presentation and are not necessarily to scale. The attached figures are: 
         FIGS. 1A and 1B  are schematic side views of a exit section of a printer having a prior art strike plate; 
         FIG. 2  is a schematic side view of an exit section of a printer comprising a strike plate having multiple strike steps, according to an exemplary embodiment of the present invention; 
         FIG. 3  is an enlarged schematic cross-sectional side view of a portion of the strike plate of  FIG. 2 ; according to an exemplary embodiment of the present invention; and 
         FIG. 4  is an enlarged schematic cross-sectional side view of a portion of the strike plate of  FIG. 2 ; rotated to present strike faces at an angle to the vertical, according to an exemplary embodiment of the present invention; and 
         FIG. 5  is a very schematic flow chart of a system in which a page is printed and transferred to an exit section, in accordance with an exemplary embodiment of the invention. 
         FIG. 6  is a schematic top view of an exit section of a printer comprising a strike plate having multiple strike steps, according to an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       FIGS. 2 and 3  are schematic side views of a strike plate  200  associated with an exit section  100 , having multiple strike steps including strike steps  256  and  266 . Upper strike step  256  comprises a strike face  258  and lower strike step  266  comprises strike face  268 . 
     In an exemplary embodiment, a leading edge  170  of a sheet  150  having a higher trajectory contacts upper strike facing  258  and/or a leading edge of a sheet having a lower trajectory contacts lower strike facing  268  following exit from the printer or other device. 
     As leading edge  170  contacts strike facing  258  or  268 , the downward movement of edge  170  that is guided by the strike plate (as in  FIG. 1A ) causing downward curling in the sheet is limited. The downward curl of edge  150  is limited by the small vertical extent of strike facings  258  and  268 , limiting the surface against which edge  170  can travel. 
     Additionally, strike face  268  (for example) comprises an upper edge surface  254 . In an exemplary embodiment, surface  254  between adjacent strike steps  256  and  266 , connects a lower edge  270  of upper strike facing  258  with an upper edge  282  of lower strike facing  268 . Outward-pointing normal vector  286  is associated with strike step  256 , for example. 
     As leading edge  170  contacts strike facing  268 , any tendency to upward movement of edge  170  (as in  FIG. 1B ) is limited since edge  170  contacts surface  254  as the sheet begins to curl upward, thereby preventing further upward curl. Outward-pointing normal vector  284  is associated with surface  254 , for example. 
     Thus, each of surfaces  254 ,  264 , etc. act to reduce upward curl for the strike facing below and to reduce downward curl for the strike facing above. 
     The present inventors have found that for very light substrate materials, which lack stiffness, have a stronger tendency to curl upward, such that, even with an upper surface for the strike step, fold-over or other undesirable results can result. The inventors have further found that when the angle of the strike face forms an acute angle, “α” with the vertical as shown in  FIG. 4 , this tendency is counteracted. An angle of 10 degrees has been found to work well with most substrate materials, although this angle may not be optimum and may depend on the substrates used. However, in some embodiments of the invention, it may be desirable to vary the angle, optionally depending on the substrate material used. This can be accomplished most simply by rotating the body of the strike plate and thus the angle of the strike face. Angles of between −5 and 15 degrees may be suitable for some situations, with 0-15 or 5-15 being of more general utility. While no particular means is shown, suitable mechanisms for rotating the strike plate by a desired amount can be used. 
     As used herein, a positive angle with the vertical is one formed by a clockwise rotation of a vertical surface about a horizontal line, for the view direction of the Figs. More generally, the rotation is such that a normal to strike face is downward rotated. 
     In the embodiment shown, the strike “plate” is actually an edge of a cylinder. Since only a small portion of the cylinder is functional, a smaller portion of the cylinder may be used. It is convenient to use a cylinder, since this shape is easy to manufacture, however, functionally, it is not necessary. Furthermore, while a cylinder having a diameter of 20-30 mm has been found to be suitable, other diameters can be used. In a particular embodiment, a diameter of 24 mm operated satisfactorily. In some embodiments of the invention, a planar surface is provided, rather than a curved surface as indicated. For ease of manufacture, the upper and lower edges may radial surfaces, such that they are perpendicular to the strike faces. However, the angle of the upper and lower edge surfaces is not critical. A non-radial surface is shown, for example, in the Figs. 
     In an embodiment of the invention, tray  102  is capable of movement upward and downward, such that as the tray fills, the receiving surface remain the same. In an embodiment of the invention an alignment stop  280  (which may be only 10 mm wide) is provided beneath strike plate  200 . Stop  280  mates with a cut-out portion of tray  102  and is optionally fixed in height with respect to strike plate  200 . As tray  102  rises and is lowered, the alignment stop slides within the cut-out portion. Optionally, stop  280  is rotatable in the direction of the arrow, as indicated, so that the sheets may be easily removed from the direction of its leading edge. 
     Strike plate  260  can be made of any suitable materials such as aluminum or an other metal. Preferably, the aluminum is hard anodized and optionally Teflon impregnated. 
     In an exemplary embodiment, strike step  256  has a vertical extent of five millimeters. However, it may have a vertical extent of more than or less than five millimeters, for example based upon the thickness of sheets  250  used in printer  100 . 
     In an exemplary embodiment, surface  254  has a horizontal extent of 3-5 mm. This allows it to fall down without problems. However, it may have a horizontal extent of more than 5 mm, or less than 3 mm, for example based upon the flexibility of sheets  250  used in printer  100 , the distance between the strike point and the tope of the pile of sheets and sheet velocity. Further, the vertical extents of edge surfaces  254  and  264  may exhibit a 1:1 ratio with the horizontal extents of strike facings  258  and  268 . Alternatively or additionally, the ratio may be higher or lower depending on the speed and/or print media used in the printer. 
     In an exemplary embodiment of the invention, the exit section of the invention is part of a printer of other paper feeding/stacking device. A very schematic flow diagram of such a combination is shown in  FIG. 5 . 
       FIG. 6  is a schematic top view of an exit section of a printer comprising a strike plate having multiple strike steps. In an exemplary embodiment of the invention, the strike plate is the surface of a cylindrical portion of an object, and the cylindrical object is rotated about the axis of the cylindrical portion with respect to the vertical. This rotation is shown as element  296  in  FIG. 6 . 
     In an exemplary embodiment of the invention, rotator  294  of  FIG. 6  is operative to rotate the strike face so as to allow for a different angle with respect to the vertical, depending on the characteristics of the sheet used. This rotation of the strike plate is also shown in  FIG. 2  as element  292 . 
     Although this description and the claims refer to paper, the invention may also be used with any other printing media, and the claims cover the apparatus and the method when any printing media is used. Additionally, this invention may be used with any printing device, whether a copy machine, printer or facsimile, that produces printed sheets seriatim. 
     The present invention has been described using non-limiting detailed descriptions of embodiments thereof that are provided by way of example and are not intended to limit the scope of the invention. It should be understood that features and/or steps described with respect to one embodiment may be used with other embodiments and that not all embodiments of the invention have all of the features and/or steps shown in a particular figure or described with respect to one of the embodiments. Variations of embodiments described will occur to persons of the art. 
     Furthermore, the terms “comprise,” “include,” “have” and their conjugates, shall mean, when used in the disclosure and/or claims, “including but not necessarily limited to.” 
     It is noted that some of the above described embodiments may describe the best mode contemplated by the inventors and therefore may include structure, acts or details of structures and acts that may not be essential to the invention and which are described as examples. For example, details of the tray and internal alignment mechanisms for the sheets after they fall into the tray, may not be present or may be replaced by other mechanisms. Structure and acts described herein are replaceable by equivalents, which perform the same function, even if the structure or acts are different, as known in the art. Therefore, only the elements and limitations as used in the claims limit the scope of the invention.