Patent Publication Number: US-7708679-B2

Title: Folding device for a folding and gluing machine

Description:
TECHNICAL FIELD 
   The present invention concerns a folding device for folding a blank of paper, cardboard, plastic, corrugated board or similar material used to form a folded box. 
   The present invention also concerns a folding and gluing machine including a folding device according to the invention. 
   BACKGROUND ART 
   To carry out folding a folded box of a given material, it is known to convert a blank of said material in a machine called a &lt;&lt;folder-gluer&gt;&gt;. 
   A blank is usually composed of two large faces, a first face called an internal face, intended to shape the inside of the folded box and a second face called an external face, intended to shape the outside of the box. 
   With regard to the running direction of the blanks in the folder-gluer, the front edge of the blank is the transverse side of the blank which first enters into the machine and the rear side is the one which last enters. Likewise, the left edge of the blank is the lateral side of the blank located at the left side of the longitudinal axis of the folder-gluer and the right edge is the lateral side of the blank located at the right side of the longitudinal axis of the folder-gluer. 
   In a folder-gluer machine, the folding operation of a blank is achieved during its conveying through the folder-gluer, using folding tools working together on each side of the blank. The tool located on the side of the internal face of the blank is called an internal tool and the tool located on the side of the external face of the blank is called an external tool. 
   At the end of a folding operation, the blank is divided into three longitudinal adjacent parts: a first panel, a fold and a second panel folded down onto the first panel. For convenience, this terminology will be used for a blank, i.e. before the folding operation. The first panel is linked to the second panel by the fold defined by an axis and a radius. The axis and the radius of the fold are respectively called its folding axis and its folding radius. 
   Usually, a conveyor conveys the blank along a substantially planar path from the inlet towards the outlet of the folder-gluer. During the folding operation, the internal tool is pressing against the internal face of the blank along the longitudinal fold and the external tool is pressing against the external face of the first panel. During the conveying of the blank, the external tool exerts onto the first panel a bending force which is applied on the front edge of the panel for causing the rotation of the first panel around the folding axis. In this known folding process, the position and the geometry of the fold are difficult to control, particularly when folding between 0 and 90°, which causes variations in the production of the folded boxes and thus quality problems. These problems are particularly acute when the panel to be folded is stiff, as is notably the case when the blank is a corrugated board blank. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to improve the folding of a blank in a folder-gluer. To this end, the present invention refers to a folding device for folding blanks, including an internal tool fit to cooperate with an external tool for forming a longitudinal fold in a blank, and a supporting guide fit to cooperate with the internal tool to sandwich the fold as the external tool folds the blank as the blank is conveyed. The supporting guide may have a longitudinal surface of a helical shape. The internal tool may be a longitudinal ramp which may be comprised of a plurality of rollers. 
   Owing to this new design, the fold is guided and supported during its forming. That allows stabilizing the position and the geometrical characteristics of the fold and thus improves the quality of the folded boxes. 
   Other features and advantages of the invention will be more clearly understood from the description of embodiments which refers to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1   a - c  are transverse sectional views of a portion of a blank and of the device according to the invention, according to the sectional planes of  FIG. 3 ; 
       FIGS. 2   a - 2   c  are views similar to those of  FIGS. 1   a - 1   c ; illustrating a portion of a blank and of the device according to prior art; 
       FIG. 3  is a front view of the device according to the invention; 
       FIG. 4  is a perspective view of the device according to the invention with a portion of a folder-gluer; 
       FIG. 5  is a front view of the internal tool; 
       FIGS. 6   a - 6   c  are transverse sectional views of the internal tool according to the sectional planes of  FIG. 5 ; 
       FIG. 7  is a transverse sectional view of a portion of a blank and of the device according to the invention. 
   

   DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION 
     FIGS. 1   a - 1   c  illustrate in a simplified manner a folding device according to the invention as well as an example of the folding operation of a blank  10 . The blank  10  includes an internal face  11  and an external face  12 . It also includes three adjacent longitudinal parts: a first panel  10   a , a fold  10   c  and a second panel  10   b . In the example, an opposing belt conveyor  5   a ,  5   b  conveys the blank  10  in a horizontal plane, according to a substantially rectilinear path  6  (see  FIG. 3 ). The belt conveyor includes an upper conveyor  5   a  and a lower conveyor  5   b . To convey the blank  10 , the second panel  10   b  is clamped between the belts of the upper  5   a  and the lower conveyor  5   b.    
     FIG. 1   a  illustrates the blank  10  at the inlet of the device according to the invention. In that position, the blank  10  is planar, i.e. the three respective longitudinal parts  10   a ,  10   c ,  10   b  of the blank are in a common horizontal plane. An internal folding tool  2  is pressing against the blank at the location of the longitudinal fold  10   c , on the side of the internal face  11  of the blank. In the example, the internal tool  2  has the form of a ramp of rollers (see  FIG. 5  for more details) oriented longitudinally. A surface  3   a  of an external folding tool  3  is pressing against the external face of the first panel  10   a , preferably, close to the left edge of the blank. In the example, the external tool  3  is a folding blade made of synthetic material from a twisted stick following a left curve so that the surface  3   a  forms a helicoid. The said helicoid  3   a  has an axis which coincides with the folding axis (see  FIG. 3 ). During the running of the blank, the blade  3  applies to the panel  10   a  a bending force which applies to the front edge of the blank. 
   According to the invention, the device includes a supporting guide  4 . During the folding operation, the supporting guide  4  is pressing against the longitudinal fold  10   c , on the side of the external face  12  of the blank, so that the fold  10   c  is sandwiched between the internal tool  2  and the supporting guide  4 . In the example, the supporting guide  4  is a metallic bar having a longitudinal surface machined to have a helical shape  4   a . The generatrix of the helical surface  4   a  is a line segment which turns around an axis coinciding with the folding axis of the fold  10   c.    
   In the position of  FIG. 1   a , the intersection of the transverse sectional plane with the helical surface  4   a  is a horizontal line segment. 
     FIG. 1   b  illustrates the blank  10  located in the second half of the device according to the invention. In that position, the blank  10  is V-shaped, the second panel  10   b  is still horizontal whereas the first panel  10   a  is inclined by an angle “a” with respect to the horizontal, with “a” illustrated equal to 60°. The internal folding tool  2  is still pressing at the location of the longitudinal fold  10   c , on the side of the internal face  11  of the blank and the external folding tool  3  is still pressing against the external face of the first panel  10   a . The supporting guide  4  is still pressing against the longitudinal fold  10   c , on the side of the external face  12  of the blank. In that position, the intersection of the transverse sectional plane with the helical surface  4   a  is a line segment inclined by an angle “b” with respect to the horizontal, with “b” equal to 30°. 
     FIG. 1   c  illustrates the blank  10  at the outlet of the device according to the invention. In that position, the blank  10  has the shape of a square, the second panel  10   b  is still horizontal whereas the angle “a” of the first panel  10   a  is equal to 90°. The internal folding tool  2  is still pressing at the location of the longitudinal fold  10   c , on the side of the internal face  11  of the blank and the external folding tool  3  is still pressing against the external face of the first panel  10   a . The supporting guide  4  is still pressing against the longitudinal fold  10   c , on the side of the external face  12  of the blank. In that position, the angle “b” of the line segment formed at the intersection of the transverse sectional plane with the helical surface  4   a , is equal to 45°. 
   The example illustrated in  FIGS. 1   a - 1   c  shows the folding of a blank in only three positions, it goes without saying as the folding is continuous that the angles “a” and “b” vary in a continuously increasing manner during the running of the blank through the folding device according to the invention. In the example, the angle “a” is equal to twice the angle “b”. In other words, as the angle “a” varies from 0 to 90° the angle “b” varies proportionally from 0 to 45°. 
     FIGS. 2   a - 2   c  illustrates in a simplified manner a folding device according to prior art as well as an example of folding a blank  100 . For comparison, the transverse sectional planes are identical to the preceding ones in  FIG. 1 . The blank  100  includes an internal face  110  and an external face  120 , it also includes three longitudinal adjacent parts: a first panel  100   a , a fold  100   c  and a second panel  100   b . A belt conveyor  50   a ,  50   b  conveys the blank  100  in a horizontal plane, according to a substantially rectilinear path. The belt conveyor includes an upper conveyor  50   a  and a lower conveyor  50   b . To convey the blank  100 , the second panel  100   b  is clamped between the belts of the upper conveyor  50   a  and the lower conveyor  50   b.    
     FIG. 2   a  illustrates the blank  100  at the inlet of a device according to prior art. In that position, the blank  100  is planar, i.e. the three respective longitudinal parts  100   a ,  100   c ,  100   b  of the blank are in the same horizontal plane. An internal folding tool  20  is pressing at the location of the longitudinal fold  100   c , on the side of the internal face  110  of the blank. An external folding tool  30  is pressing against the external face of the first panel  100   a , close to the left edge of the blank. During the running of the blank, the external folding tool  30  applies onto the panel  100   a  a bending force which applies to the front edge of the blank. 
   In prior art, a folding guide  40  is pressing against the external face of the first panel  100   a , close to the longitudinal fold  100   c , without being in contact with the said fold. Likewise, the belt of the lower conveyor  50   b , is pressing against the external face of the second panel  100   b  close to the longitudinal fold  100   c , without being in contact with the said fold. It can thus be noted that the fold  100   c  is not supported on the side of the external face  120 . 
   The fact that the fold is not supported during its forming does not allow to control the folding operation with accuracy, which means that the geometrical characteristics of the fold such as for example the position of the folding axis, the folding radius, may vary from one blank to the other, which is not acceptable for the quality of the production. In prior art, the folding guide  40  is a folding belt, the surface of the belt which is in contact with the external face of the first panel  100   a  is designated as  40   a . In the position of  FIG. 2   a , the intersection of the transverse sectional plan with the surface  40   a  is a horizontal line segment. 
     FIG. 2   b  illustrates the blank  100  in another position of the device according to prior art. In that position, the blank  100  is V-shaped, the second panel  100   b  is still horizontal whereas the first panel  100   a  is inclined by an angle “aa” with respect to the horizontal, with “aa” equal to 60°. The internal folding tool  20  is pressing a the location of the longitudinal fold  100   c , on the side of the internal face  110  of the blank and the external folding tool  30  is pressing against the external face of the first panel  100   a , close to the left edge of the blank. In prior art, the folding guide  40  is pressing against the external face of the first panel  100   a , close to the longitudinal fold  100   c , without being in contact with the said fold. In that position, the intersection of the transverse sectional plane with the surface  40   a  is a line segment inclined by an angle “bb” with respect to the horizontal, with “bb” equal to 60°. 
     FIG. 2   c  illustrates the blank  100  at the outlet of the device according to prior art. In that position, the blank  100  has a square corner, the second panel  100   b  is horizontal whereas the angle “aa” of the first panel is equal to 90°. The internal folding tool  20  is pressing at the location of the longitudinal fold  100   c , on the side of the internal face  110  of the blank and the external folding tool  30  is pressing against the external face of the first panel  100   a , close to the left edge of the blank. In prior art, the folding guide  40  is pressing against the external face of the first panel  100   a , close to the longitudinal fold  100   c , without being in contact with the said fold. In that position, the angle “bb” of the line segment formed at the intersection of the transverse sectional plane with the surface  40   a  is equal to 90°. 
   The prior art illustrated in  FIGS. 2   a - 2   c  shows the folding of a blank only in three positions, it goes without saying as the folding operation is continuous that the angles “aa” and “bb” vary in a continuously increasing manner during the running of the blank. Moreover, the belt  40  follows the panel  110  during the whole folding operation, in other words the surface  40   a  remains in contact with the external face of the first panel  100   a  during the folding operation, consequently, the angle “aa” is equal to the angle “bb”. 
     FIG. 3  illustrates a front view of a folding device according to the invention. The arrow  6  shows the running direction of the blanks in the folder-gluer, that direction is parallel to the longitudinal axis of the folder-gluer. The arrow E shows the inlet of the device and the arrow S shows the outlet. Between the inlet E and the outlet S, the folding blade  3  forms a first blade portion of the axis  7  for folding the panel  10   a  of 0 to 90°. The axis  7  is the folding axis of the blank  10 . After the outlet S, the folding blade  3  is elongated by a second blade portion, complementary to the first, for folding the panel  10   a  of 90° to 180° (see in particular  FIG. 4 ). Alternatively, the folding of 90° to 180° can be carried out by a folding belt (not shown). 
   Between the inlet E and the outlet S, the angle formed between the generatrix of the helical surface  4   a  and the horizontal plane varies in a continuously increasing manner between 0° at the inlet E and 45° at the outlet S. The ramp  2  of rollers includes a plurality of rollers  2   a  aligned on an axis parallel to the folding axis  7 . In a device according to the invention, the fold  10   c  can be sandwiched between the internal tool  2  and the supporting guide  4 . To do so, the contact points of the rollers  2   a  with the internal face  11  of the fold  10   c  are opposite to the contact line of the helical surface  4   a  with the external face  12  of the fold  10   c.    
   The distance which separates the said contact points of the rollers  2   a  from the said contact line of the helical surface  4   a  is adjustable according to the thickness “e” of the blank to be folded (see  FIG. 7 ). 
   Advantageously, a conveying belt  8  is guided along the helical surface  4   a  so that the fold  10   c  of the blank can be sandwiched between the internal tool  2  and the said belt  8 . In that embodiment, the supporting guide  4  includes the conveying belt  8 , which takes the shape of the helical surface  4   a.    
     FIG. 4  illustrates a folding device according to the invention and a portion of the folder-gluer. For clarity reasons, the upper conveyor  5   a  is not shown, only two belts of the lower conveyor  5   b  are shown. The folding blade  3  is entirely shown. In a device according to the invention, a blank  10  which arrives at the inlet E is sandwiched between the rollers  2   a  of the ramp  2  and the helical surface  4   a , at the place where the longitudinal fold  10   c  must be formed. Leaving the device, the blank  10  is folded at 90°, in other words, the first panel  10   a  forms a right angle with the second panel  10   b . The following folding operation, i.e. folding the first panel  10   a  of 90° to 180°, being carried out in a conventional manner, will not be described here. 
     FIG. 5  illustrates a ramp  2  of rollers used as internal tool. That ramp has a plurality of identical rollers  2   a . Each roller  2   a  is mounted free rotatably around an axis  2   c  (see  FIGS. 6   a - 6   c ). All the axes  2   c  are in a same longitudinal plane. Brackets  2   b  are intended to mount the ramp  2  onto the folder-gluer. 
     FIGS. 6   a - 6   c  illustrate the ramp  2  in a transverse sectional view according to the sectional plans A-A, B-B and C-C of  FIG. 5 . These sectional plans are identical to the sectional plans of  FIG. 3 . The inclination of the rotation axis  2   c  of the rollers  2   a  with respect to the horizontal is constant from one roller to the other over the whole length of the ramp  2 . 
     FIG. 7  illustrates in a transverse section according to the-sectional plan B-B, the contact points of a roller  2   a  with the fold  10   c  of a blank  10  sandwiched between the internal tool  2  and the supporting guide  4 . The periphery of the roller  2   a  has a rounded shape. That rounded shape is an arc of a circle A 1  with a radius R, of a center  7 ′ and of an angle α. The radius R is the folding radius of the fold  10   c . In the example R is equal to 0.75 mm and α is equal to 150°. The straight line passing through the center  7 ′ of all the rollers  2   a  defines the folding axis  7 . The contact points of the roller  2   a  with the blank  10  thus form an arc of a circle A 2  contained in A 1 , in other words, the radius and the center of A 2  are the same as for A 1 , but the angle of A 2  is less than the angle of A 1 , that is to say β is the angle of A 2 . The angle β can also be defined as being the angle of the arc of a circle obtained by the projection of the contact points of the roller  2   a  in a normal plane to the running direction of the blank. 
   Advantageously, the bisecting line of the angle β is orthogonal to the line segment formed at the intersection of the-sectional plan B-B with the helical surface  4   a . That feature can be seen on all the transverse sections along the folding device according to the invention. Owing to that feature, the fold  10   c  is guided at all the steps of its forming. 
   Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.