Abstract:
A folding device for signatures includes a saddle-shaped folding sword having an upright folding edge and an inside guide element below the upright folding edge on which the signatures are folded while passing through the folding device. An outside folding element follows and operates jointly with the inside guide element for folding the signatures.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
         [0001]    This application claims the priority of European Patent Application No. 01810320.0 filed in the European Patent Office on Mar. 29, 2001, the disclosure of which is being incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    The invention relates to a signature folding device, comprising a saddle-shaped folding sword with an inside guide element on which the signatures are folded. The device furthermore comprises an outside folding element that follows along and operates jointly with the inside guide element for folding the signatures.  
           [0003]    Folding devices of the aforementioned type are known. With these devices, the signatures to be folded are guided onto a stationary folding sword and are folded thereon while passing through, with the aid of the outside folding element that follows. Belts, round strings, V-belts or chains, for example, can form the folding element that follows. A folding design of this type has the particular disadvantage that the folding occurs only gradually and that the signatures do not fit form-fittingly against the folding sword until the end of the folding operation. Only at the end of this folding operation are the signatures held securely in place and can thus be transported without slipping. Prior to this, the signatures are quite unstable and can deviate from the predetermined course, thus resulting in an inexact folding. Another difficulty is that the signatures to be folded are slowed down on the inside, by the folding sword that is stationary, and at best have a tendency toward smearing. The higher the effect of the outside folding element, the higher the tendency to smearing.  
           [0004]    The folding element on the inside is, for example, a chain with fitted-on roof-shaped elements or is formed by round strings.  
           [0005]    A folding device as defined in the preamble is disclosed in Swiss Patent document CH 615 646 A. The inside folding element described in this document is formed by a linear row of folding rollers. On the one hand, the folding element on the inside should be a precision element, so that a sharp, closed and if possible complete fold can be formed. On the other hand, this folding element should also be robust to prevent the element from being bent or damaged during backups, which requires a certain structural size. These two requirements conflict with each other, so that compromises are necessary in the one or the other direction. If the folding element on the inside consists of rollers, arranged one behind the other as specified in the Swiss Patent, the difficulty arises that during the folding process the front edges of the signatures to be folded must repeatedly run in via the subsequent roller. If the signatures to be folded are not always positioned exactly the same way for the run in, the resulting fold is not sharp and the folding accuracy cannot meet high requirements. A precise run in of the signatures onto the rollers is difficult to realize since stresses in the signatures to be folded are hard to avoided during the process of folding the signatures while they are passing through.  
         SUMMARY OF THE INVENTION  
         [0006]    Thus, it is an object of the invention to provide a folding device of the aforementioned type, which permits a more precise folding, but which can nevertheless be produced easily and cost-effectively and is robust.  
           [0007]    The above and other objects are accomplished according to the invention by the provision of a folding device for signatures, comprising: a saddle-shaped folding sword including an upright folding edge and an inside guide element below the upright folding edge on which the signatures are folded while passing through the folding device; and an outside folding element that follows and operates jointly with the inside guide element for folding the signatures.  
           [0008]    With this type of folding device, a precise, saddle-shaped and continuous folding line can be formed at the folding sword. The inside guide element is arranged at the location where the outside folding element grips and transports the signature. As a result, the signature to be folded is guided definitively and continuously and the signatures are prevented from slipping off the folding sword, which is undesirable.  
           [0009]    According to a modification of the invention, the inside guide element is designed so that it projects from the guide surfaces on the side of the folding sword. As a result, the side regions in which the signatures are guided can be exactly determined. If, according to another modification of the invention, the folding sword is tapered in the movement direction, at least in a frontal area, the signatures can be mostly closed and the folding sword can still have a robust design. Several rollers aligned in a row advantageously form the guide element on the inside. These are preferably arranged such that they project with at least one outside edge on the side at the guide surfaces of the folding sword. A particularly good guidance is achieved if the roller surface on at least one edge is essentially parallel to one guide surface on the side of the folding sword.  
           [0010]    According to another modification of the invention, two strands, preferably two V-belts, form the outside folding element that follows.  
           [0011]    A particularly stable guidance of the signatures is achieved if these V-belts are not simply adjusted to feed to the folding sword, but if they are twisted along the folding sword, in accordance with the feeding. This results in a very stable guidance of the signatures during the folding operation, which are stretched over the edge of the folding sword. The signatures consequently have a stable guidance over the complete region of the folding sword and are effectively prevented from sliding off or otherwise deviating from the predetermined path. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    Further advantageous features follow from the dependent patent claims, the following description and the drawing.  
         [0013]    One exemplary embodiment of the invention is explained in further detail in the following with the aid of the drawing, in which:  
         [0014]    [0014]FIG. 1 is a schematic view from the side of a folding device according to the invention.  
         [0015]    [0015]FIG. 2 is a different view of the folding device according to FIG. 1, wherein parts are left out for drawing reasons.  
         [0016]    [0016]FIG. 3 is a view from the side of the folding sword.  
         [0017]    [0017]FIG. 4 is a view from above of the underside of the folding sword.  
         [0018]    [0018]FIG. 5 is a sectional view along the line V-V in FIG. 3.  
         [0019]    [0019]FIG. 6 is a sectional view along the line VI-VI in FIG. 2.  
         [0020]    [0020]FIG. 7 is a cross-sectional view through the folding sword and the outside folding element.  
         [0021]    [0021]FIG. 8 is a view of the folding sword in the direction of arrow VIII in FIG. 2.  
         [0022]    [0022]FIGS. 9 and 10 are schematic views showing a feeding to the outside folding element.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]    Referring to FIG. 1, signatures  3  to be folded are initially stacked one above the other to form a stack  2 . The lowest signature  3  is respectively tilted with the aid of a suction device  5  from the stack  2  into a gripping region of a gripping drum  7 . Gripping drum  7  has grippers  6  that respectively grip one tilted signature  3  and pull this signature from stack  2 . The pulled-off signature  3  can be notched with the aid of a notching wheel, not shown herein, or can be otherwise weakened or processed, for example by moistening it, in order to prepare the fold. The pulled-off signatures  3  are respectively guided individually with the aid of transfer belts  9  and  10  to a run-in  32  of a folding section  33 . A folding sword  18 , two endless strands  12  and two pressing rollers  16  essentially form folding section  33 .  
         [0024]    A shaft  8  drives gripper drum  7  in the direction of arrow  35  and a drive element  34  drives the shaft  8 . The transfer belts  10  are driven by the gripper drum  7  and are guided so that they in turn drive pressing rollers  16  and two guide rollers  29 . The drive element  34  drives a wheel  13 ′, which in turn drives the strands  12 . This ensures a synchronized operation of gripper drum  7  with pressing rollers  16  and the two strands  12 . Tension for feed belts  10  can be adjusted with a lever  11 .  
         [0025]    FIGS.  3  to  5  show that folding sword  18  consists of two halves  18   a  and  18   b , which are fitted together and are detachably connected with screws  35 . Recesses  25 , in which respectively one roller  26  is positioned, are left open between the two halves  18   a  and  18   b , wherein the rollers  26  are arranged in a row. They are positioned by screwing a head screw  24  into the half  18   a  or  18   b , as well as with a pivoting bearing  27 . Respectively below a folding edge  22 , these recesses  25  are provided with a circular-segment shaped window  36  for each roller  26 , as shown in FIG. 3. These windows  36  are respectively located in the upper region of a guide surface  21   a  or  21   b , which is slanted relative to a vertical line. An upright standing (uninterrupted), comparatively sharp folding line  22   a  is formed by the folding edge  22 . This folding line extends over the complete folding section  33 . The folding edge  22  forms an isosceles triangle in the cross section. The outside edges  26   a  of rollers  26  project over respectively one guide surface  21   a  or  21   b . According to FIGS. 9 and 10, they form side surfaces  31  in this region, which are parallel to the guide surfaces  21   a  or  21   b . The rollers  26  thus extend with their edges through the windows  36  and to the outside of the folding sword  18 , thereby projecting over the guide surfaces  21   a  or  21   b . The distance between these side surfaces  31  and the guide surfaces  21   a  or  21   b  is comparatively small, for example 0.5 mm. FIGS. 3 and 4 show that the rollers  26  and the windows  36  are arranged in the front half of the folding sword  18 . The front window  36   a , as seen in the movement direction, is located in the region of two opposite-arranged surfaces  28 , which taper the folding sword  18  at the front end, as shown particularly clearly in FIG. 4.  
         [0026]    For the folding operation, the rollers  26  operate jointly with the two strands  12 , which form an outside folding element  38  together with the deflection rollers  13 , the guide rollers  29  and additional guide rollers  37 . The two strands  12  are preferably V-belts, for example having the trapezoid cross-sectional shape shown in FIG. 7. However, the strands  12  can also be round strings, belts or chains for example. As previously explained, the two strands  12  are driven synchronously with the transfer belts  9  and  10 . As indicated in FIG. 1, the arrow  39  shows the movement direction for the two strands  12 . The deflection roller  13 ′ deflects the two strands  12  toward the folding section  33 . The strands  12  leave this folding section  33  again at roller  13 ″. The guide rollers  37  are arranged in the region of folding section  33 , such that the two strands  12  are adjusted for feeding the folding sword  18 , as shown in FIGS. 9 and 10.  
         [0027]    For the preferred feeding method according to FIG. 9, the two strands  12  are twisted in the longitudinal direction in the region of folding section  33 . According to the cross-sectional view shown with drawn-out lines, the two strands  12  are twisted directly behind the run-in  32  so that in the region of folding line  22   a , they fit with their lower edges  40  elastically against the folding edge  22 . A signature  3  to be folded is thus guided at the folding line  22   a  in the region where a fold is to be formed. The frictional surface is comparatively small since the signatures  3  in this case are opened up comparatively wide and the folding edge  22  is comparatively sharp in the region of folding line  22   a . During the further course, the two strands  12  travel downward with the aforementioned edges  40 , respectively diametrically opposed to each other, and move initially to the position indicated in FIG. 9 with a dash-dot line. As can be seen, the edges  40  move to the region of surfaces  31  and, in the process, fold the signature  3  around the folding line  22   a . The correspondingly folded signature  3 ′ is also indicated with a dash-dot line at this location. Finally, the strands  12  reach the position shown with dashed line. In this position, the two strands  12  are also pressed elastically against the surfaces  31  of the respective rollers  26 . Between the surfaces  41  and the surfaces  31  of rollers  26 , the signature  3 ″ is held in place and carried along by the pressing force of the two strands  12 . The rollers  26  passively rotate along in this case. Since the surfaces  31  project relative to the guide surfaces  21   a  or  21   b , as explained in the above, the friction of the signature  3 ″ along the side surfaces  21   a  and  21   b  is comparatively low, but the signature is nevertheless always securely guided. It is essential that the signature  3  is guided right from the start of folding section  33  by the edges  40 . The signature  3  to be folded is thus transported in a straight line and without essentially deviating from the course in the region of folding section  33  and a precise folding line is thus formed.  
         [0028]    According to FIG. 10, the two strands  12  are not twisted for the feeding and, as can be seen, move without twisting around their longitudinal axis from the top to the bottom. The lowest position, shown with dashed lines, corresponds to the lowest position according to FIG. 9. However, shortly after the run-in  32 , the edges  40  of strands  12  are comparably far removed from the folding edge  22 . The signature  3  in this case is not pressed elastically against the folding edge  22  and, accordingly, the signature  3  is guided to a lesser degree than in FIG. 9. The feeding according to FIG. 10 is a variant of the invention. However, it can be improved if the width and the contact surfaces of rollers  26  are adapted to the outside folding elements, for example, so that the width of roller  26  decreases in the paper movement direction. In the region of deflection roller  13 , the strands  12  are lifted off the folding sword  18 . The folded signatures  3  are then moved between the two pressing rollers  16  and are closed by these rollers. The signatures  3  subsequently are moved onto the horizontally extending tongue  42 , shown in FIG. 1, and are there gripped by carriers  20  of a collecting chain  19 . After leaving the tongue  42 , they are deposited on the collecting chain  19  and are moved with this chain to an additional processing station that is not shown herein. The tongue  42  and the collecting chain  19  are not required and can be replaced with other transport means.  
         [0029]    The invention has been described in detail with respect to preferred embodiments, and it will now be apparent from the foregoing to those skilled in the art, that changes and modifications may be made without departing from the invention in its broader aspects, and the invention, therefore, as defined in the appended claims, is intended to cover all such changes and modifications that fall within the true spirit of the invention.