Patent Publication Number: US-7914433-B2

Title: Folding roller and corresponding folding device

Description:
This claims the benefit of FR 07 57793 filed on Sep. 24, 2007 and hereby incorporated by reference herein. 
     The present invention relates to a folding roller for a device for folding a flat product to be folded, the roller extending along a center axis. 
     BACKGROUND 
     From the prior art, folding rollers are known which comprise front and rear axial portions. During use, the rear axial portion extends in the region of a rear portion of a signature to be folded, whilst the front axial portion extends in the region of a front edge of a signature to be folded. 
     The rear axial portion comprises a recess which is capable of releasing the upper portion of the signature to be folded in order to prevent occurrences of creasing of the downstream portion of the folded booklet. 
     Known folding rollers are capable of gripping the central portion of the booklet in the region of the front edge thereof in order to fold the booklet. 
     SUMMARY OF THE INVENTION 
     However, it has been found that known folding rollers lead to occurrences of creasing in the region of the front edge at the location of the fold. 
     An object of the invention is to improve the quality of folding, in particular at high folding speeds. 
     To this end, the present invention provides a folding roller of the type indicated above, characterized in that the second axial portion comprises a main relief which is radially recessed relative to the first folding surface, the second axial portion including a second surface for folding the product to be folded and the main relief being radially recessed relative to the second folding surface. 
     According to specific embodiments, the folding roller may include one or more of the following features: 
     the first folding surface and the second folding surface are radially aligned; 
     the first axial portion includes an auxiliary relief which is radially recessed relative to the first folding surface, the auxiliary relief and the main relief extending over different angular ranges around the center axis; 
     the auxiliary relief extends over an angular range of between 120° and 160°, and preferably between 140° and 150°, around the center axis; 
     the main relief extends over an angular range greater than 270°, in particular greater than one of the ranges 300°, 310° and 320°, and this angular range is a maximum of 325°, around the center axis; 
     the first folding surface and the auxiliary relief form a first connection edge; the second folding surface and the main relief form a second connection edge and the first connection edge and the second connection edge are circumferentially aligned; 
     the roller includes a third axial portion which has a third folding surface which extends all the way around the center axis and which is centered on the center axis and which is radially aligned with the first folding surface, the third axial portion extending axially between the first axial portion and the second axial portion; 
     the roller includes a fourth axial portion which defines a cylindrical surface which extends all the way around and which is centered on the center axis, and which is radially aligned with the first folding surface, and the second axial portion is arranged axially between the first axial portion and the fourth axial portion and; 
     the roller includes at least one groove which extends all the way around and which extends axially between the first axial portion and the second axial portion. 
     The invention also provides a folding device including: 
     a folding plate; 
     two folding rollers which together define a folding gap, at least one of the folding rollers being a folding roller as defined above. 
     According to specific embodiments, the folding device may include one or more of the following features: 
     the folding device defines a conveying direction for products to be folded, and the second axial portion is arranged downstream of the first axial portion in the conveying direction; 
     the two folding rollers are capable of being driven in such a manner that their second folding surface is capable of overlapping a central portion of a product to be folded at the location of a front edge of this product, and the main relief is capable of overlapping a lateral portion of the front edge of the product to be folded when the product to be folded is gripped by the two rollers; 
     the folding device includes a stop which is capable of stopping the product to be folded, and the stop is axially aligned with the main relief. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood from a reading of the following description, given purely by way of example and with reference to the appended drawings, in which: 
         FIG. 1  is a sectioned view of a folding device according to the invention; 
         FIG. 2  is a partially sectioned side view of the folding device according to the invention, when viewed along the section II of  FIG. 1 ; 
         FIG. 3  is a view corresponding to the view of  FIG. 2  of the folding device before the folding operation; 
         FIGS. 4 and 5  are perspective views of a folding roller according to the invention; and 
         FIG. 6  is a schematic axial view of the folding rollers and strippers. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a folding device according to the invention, generally designated  2 . 
     The folding device  2  includes a chopper folding device of a rotary press, in particular an offset press. 
     The folding device  2  includes a folding table  4 , a folding plate  6 , two folding rollers  8  and  10  and conveying belts  12 . 
     The folding device  2  is capable of folding a signature S which is conveyed by the conveying belts  12  on the folding table. 
     The folding table  4  extends along a table plane P-P and defines a folding aperture  14 . 
     The folding plate  6  is arranged above the folding table  4  and is capable of pushing the central portion  24  of a signature S through the folding aperture  14 . 
     The folding rollers  8 ,  10  each extend along a center axis X-X and together delimit a folding gap  16 . The folding roller  8  is driven in a first rotation direction R 1  and the folding roller  10  is driven in a second rotation direction R 2  opposed to the first rotation direction R 1 . 
     Furthermore, the folding device  2  includes a stop  18  which is capable of stopping the signature S before it is folded. 
     The conveying belts  12  are driven in a driving direction E or conveying direction which extends from an inlet of the folding device  2  towards the stop  18 . 
     Each signature S delimits a front edge  20  which is directed downstream of the driving direction E and a rear edge  22  which is directed upstream of the driving direction E, each signature S also including a central portion  24  which is folded by the plate  6  and the folding rollers  8  and  10 . Each signature also includes two lateral edges  26  which extend parallel with the driving direction E. 
     The signature S includes a single flat sheet. In a variant, the signature S may include at least one folded sheet whose fold forms the front edge  20 . 
     The features of the folding roller  8  will be described below, the folding roller  10  being symmetrical (see  FIG. 6 ) relative to a plate plane along which the folding plate  6  extends. 
     The folding roller  8  includes a first axial portion  30 , a second axial portion  32 , a third axial portion  34  and a fourth axial portion  36 . 
     The first axial portion  30  includes a first surface  40  for folding the signature S to be folded. This folding surface  40  is a partially cylindrical surface having a circular cross-section about the center axis X-X. 
     The first axial portion  30  further includes an auxiliary relief  42  which is radially recessed relative to the first folding surface  40 . This auxiliary relief  42  includes planar faces. The first axial portion  30  extends during the folding operation in the region of the rear edge  22  of the signature S. The connection between the first folding surface  40  and the auxiliary relief  42  forms a first connection edge A which is located at the downstream end of the auxiliary relief  42 , when viewed in the first rotation direction R 1 . 
     The auxiliary recess  42  extends around the center axis X-X over an angular range of between 120° and 160°, and preferably between 140 and 150°. 
     The roller  8  is driven in such a manner that the first folding surface  40  grips the central portion  24  when the folding plate  6  pushes the signature S into the folding gap  16 . That is to say, the two first folding surfaces  40  of the folding rollers  8 ,  10  grip the central portion  24  of the signature S. 
     The second axial portion  32  extends axially so as to overlap the front edge  20  during the folding operation when the folding device is in operation. To this end, the second axial portion  32  and therefore the auxiliary relief  42  axially overlaps the stop  18 . 
     The second axial portion  32  includes a main relief  44  which is radially recessed relative to the folding surface  40  of the first axial portion  30 . 
     As can be seen in  FIG. 5 , the second axial portion  32  further includes a second folding surface  46  which is a partial cylindrical surface having a circular cross-section about the axis X-X. The second folding surface  46  is radially aligned with the first folding surface  40 . 
     The main relief  44  extends around the center axis X-X over an angular range of preferably between 320 and 325°. Generally, it may be greater than 270°, in particular greater than one of the ranges 300°, 310° and 320°, and this angular range is a maximum of 325°. The connection between the second folding surface  46  and the main relief  44  forms a second connection edge B located at the downstream end of the main relief  44 , when viewed in the first rotation direction R 1 . The first connection edge A and the second connection edge B are circumferentially aligned. 
     The connection between the second folding surface  46  and the main relief  44  forms a third connection edge C which is located at the upstream end of the main relief  44  when viewed in the first rotation direction R 1 . This third connection edge C is circumferentially overlapped by the folding surface  40 . 
     The angular range of the auxiliary relief  42  completely overlaps the angular range of the main relief  44  in the circumferential direction around the center axis X-X. That is to say, the folding surfaces  40  and  46  are axially aligned. The main relief  44  and the auxiliary relief  42  thus extend over different angular ranges around the center axis X-X. 
     The third axial portion  34  extends axially between the first axial portion  30  and the second axial portion  32 . The third axial portion  34  is provided with a third folding surface  48  which extends all the way around the center axis X-X. The third folding surface  48  therefore has a cylindrical shape having a complete circular cross-section around the center axis. The third folding surface  48  is radially aligned with the first folding surface  40 . This third axial portion is therefore capable of gripping the signature S over the entire width between the central portion  24  and the lateral edges  26  thereof. 
     The third axial portion  34  is further provided with two grooves  50 ,  52  which extend all the way around. 
     As illustrated in  FIG. 6 , the folding device  2  also includes strippers  58  which engage in the grooves  50 ,  52  and which are capable of guiding the folded signature and removing it from the folding rollers  8 ,  10 . 
     The fourth axial portion  36  includes a cylindrical surface which has a circular cross-section which is centered on the axis X-X. The second axial portion  32  is arranged axially between the fourth axial portion  36  and the first axial portion  30  or the third axial portion  34 . 
     The folding roller  8  further includes two pins  60  which are arranged at each side of the roller. 
     The folding device  2  operates in the following manner. 
     The signatures S are transported by the conveying belts  12  as far as the stop  18 . 
     When the signature S reaches the stop position thereof, the folding plate  6  pushes the central portion  24  through the folding aperture  14  and the central portion  24  is gripped by the first folding surface  40  and by the third folding surface  48 . Furthermore, the portion of the central portion  24  which overlaps the second axial portion  32 , and the portion of the front edge  20  adjacent to the central portion are first gripped by the second folding surface  46 . 
     Then, the signature S is conveyed through the folding gap  16  via the first, the second and the third folding surfaces until the main relief  44  releases the portion of the front edge  20  of the signature at a location remote from the fold formed in the central portion  24 . At the same time, the first folding surface  40  and the third folding surface  48  continue driving the signature through the gap  16 . 
     When the folding rollers  8 ,  10  continue to rotate, the lateral edges  26  of the signature S are released in the region of the first axial portion  30  via the auxiliary relief  42 . This prevents untimely folding of the lateral edges in the region of the rear edge  22 . 
     Taking into account that the folding rollers according to the invention release a large portion of the front edge  20 , they allow creases to be prevented in the region of the front edge  20  at the location of the central portion  24 , even at high folding speeds.