Patent Publication Number: US-11660774-B2

Title: Holding device for a workstation of a forming machine

Description:
The present invention relates to a device enabling sheet-like elements to be held when they are introduced one by one into a workstation equipping a forming machine. The invention finds particularly advantageous but non-exclusive application in the field of manufacturing cardboard packaging. The invention also relates to a workstation of a machine for forming sheet-like elements, such as a waste-ejection station, and to a machine for forming sheet-like elements. 
     It is known to die-cut blanks in a succession of sheets by means of a forming machine, commonly referred to as a die-cutting press. In this type of machine, each sheet is introduced successively into a die-cutting station inside which the actual die-cutting operation takes place, and then into an ejection station where the waste generated in the preceding stage is removed. 
     In such a waste ejection station, each sheet is introduced individually in a pre-cut form. The blanks have indeed been die-cut but are still attached to one another via attachment points. The same is true for numerous sheet portions which are not used in the final product and are consequently considered as waste. 
     When a die-cut sheet is decelerated in the ejection station, before coming to a stop between the ejection tools, its rear part naturally tends to catch up its front part which is held by the gripper bar. This phenomenon is particularly acute when the sheets are relatively light and/or have large dimensions. 
     For whatever reason this might be, the consequence of this is that the flatness of the sheet is deformed substantially, which further increases the risk of being offset relative to the tools. Now it is known that the ejection operation requires precision in the prior positioning of the sheet; the said precision being of course all the greater when the waste is small in size. 
     In order to overcome this difficulty, it was conceived that each die-cut sheet could be held during its introduction into the ejection station, partially retaining it by its rear part. Systems generating a local suction at the face of the sheet have in particular been developed for this purpose. A Bernoulli tablet, placed transversely at the entrance to the ejection station, may be considered in particular. 
     This type of arrangement does, however, have the disadvantage of being relatively expensive. 
     Also, one of the technical problems to overcome by the subject of the present invention is to provide a holding device comprising a suction member capable of partially retaining each sheet by its rear part during the stage of introducing the said sheet into the said workstation, which would make it possible to avoid the problems of the prior art, in particular by offering good suction efficiency at low cost. 
     To this end, the subject of the present invention is a device for holding a sheet-like element during the stage of introducing it into a workstation of a forming machine, such as a waste-ejection station, the said holding device comprising a suction member configured so as to partially retain each sheet by its rear part during the stage when the said sheet is introduced into the said workstation, characterized in that the suction member has at least two motorized propeller fans installed transversely at the entrance to the workstation, beneath the plane along which the sheet-like elements move, the axes of rotation of the propellers of the fans being substantially parallel to one another and perpendicular to the plan along which the sheet-like elements move, the direction of rotation and the inclination of the propellers being configured so as to generate a flow of air capable of applying suction to the rear of the lower face of the sheet-like element during the stage in which the said sheet is introduced into the said workstation. 
     The invention as defined in this way has the advantage of generating effective holding of the sheets in the workstation at a relatively low cost. 
     According to one or more features of the holding device, taken separately or in combination: 
     the axes of rotation of the fans are implemented transversely in a transverse window with a width of less than ten centimetres, 
     the fans are of the computer fan type, 
     the holding device has between two and fifteen fans in number, 
     the holding device has a support table in which at least two through orifices are formed, the fans being arranged beneath the support table, at least partly opposite the opening of at least one through orifice, 
     the fans are fixed to the support table, 
     the through orifices are oblong holes extending in the longitudinal direction in which the sheets move, 
     additional through orifices are formed in the table support, 
     the holding device has a pilot control unit configured so as to pilot-control the motors of the fans according to a reconfigurable rotational speed of the propellers. 
     The subject of the invention is also a workstation of a machine for forming sheet-like elements, such as a waste ejection station, characterized in that it has a holding device as defined above. 
     The subject of the invention is also a machine for forming sheet-like elements, characterized in that it has at least one workstation as described above. 
    
    
     
       Other advantages and features will become apparent on reading the description of the invention, and from the attached drawings which show a non-limiting exemplary embodiment of the invention and in which: 
         FIG.  1    illustrates a forming machine into which a waste ejection station equipped with a holding device is integrated. 
         FIG.  2    shows in detail the entrance to the waste ejection station, at the moment when a sheet is ready to be introduced into it. 
         FIG.  3    is a view substantially similar to  FIG.  2    but with the sheet at the end of the stage of introducing it into the waste ejection station. 
         FIG.  4    shows an example of a fan with which the holding device is provided. 
         FIG.  5    is a highly schematic view illustrating the arrangement of the axes of rotation of the fans of the holding device relative to the plane in which the sheets move in the forming machine. 
         FIG.  6    shows a view from below of an exemplary embodiment of the holding device equipped with a support table to which the fans of the holding device are fixed. 
     
    
    
     In these drawings, identical elements have the same reference numerals. The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment or that the features apply solely to one embodiment. Individual features of different embodiments can also be combined or swapped to provide other embodiments. 
     It is understood that, throughout this text, the term “sheet” refers very generally to any “sheet-like element” such as, for example, a sheet of paper, compact cardboard, corrugated cardboard, plastic, etc. 
     The terms “front” and “rear” are defined with reference to the longitudinal direction D in which the sheets move in the forming machine  1 . These elements move from the rear to the front, generally following the main longitudinal axis of the machine. The terms “upper” and “lower” are defined with reference to the arrangement of the elements in a forming machine on the ground. 
       FIG.  1    shows a forming machine  1  enabling blanks to be die-cut from a succession of sheet-like elements  10 . These blanks are intended to be later folded and glued to make up packaging boxes. 
     In this particular embodiment, chosen purely by way of example, the forming machine  1  is classically composed of multiple workstations  100 ,  200 ,  300 ,  400 ,  500  which are juxtaposed but interdependent in order to form a single unit. Thus, an introduction station  100 , a die-cutting station  200 , a waste ejection station  300 , a receiving station  400  with blank separation, and a station  500  for discharging residual waste can be found. Moreover, the presence of transporting means  600 , which are responsible for individually moving each sheet  10  from the exit of the introduction station  100  to the discharging station  500  can be observed. 
     The number and type of workstations in a forming machine  1  can vary as a function of the nature and complexity of the operations to be performed on the sheets; the receiving station  400  can in particular be omitted. 
     It should be noted that in all of  FIGS.  1  to  3   , the different workstations  100 ,  200 ,  300 ,  400 ,  500  have been shown in a highly schematic fashion. Each of them has indeed been represented by two rectangles which symbolize respectively its upper part and its lower part, these parts being positioned on either side of the plane P in which the sheets move. 
     Conventionally, the introduction station  100  principally comprises a feeder and a feed table and it is supplied with sheets  10  from a pile stored on a palette. The feeder is more particularly responsible for removing the sheets  10  one by one from the top of the pile and sending them successively onto the directly adjacent feed table. At the feed table, the sheets  10  are placed in a lap, in other words laid one after the other so that they overlap partially. The whole lap is moved along a bed by means of a belt-driven transport system towards the die-cutting station  200 . At the end of the lap, the leading sheet  10  is systematically positioned precisely by means of a locating system commonly referred to as a register. Because such an introduction station  100  is perfectly known in the prior art, it will not be described further here. For this same reason, these different components have not been shown in detail in the drawings. 
     As for the die-cutting station  200 , it takes the classical form of a platen press which, in this exemplary embodiment, uses an upper fixed crosshead on the lower face of which a die-cutting tool is integrally formed, and a lower movable crosshead on the upper face of which the upsetting counterpieces are fixed. 
     The workstation situated just after the die-cutting station  200  is the ejection station  300 . The function of the latter is to remove the waste which is directly produced during the die-cutting of the sheets  10 . Central waste zones, as well as rear and side strips, are referred to here in particular. Whatever the case, this operation classically takes place here owing to the interaction of three elements, namely an upper ejection tool, a central ejection board, and a lower ejection tool. 
     Downstream from the ejection station  300  is situated the receiving station  400 , the main function of which consists in breaking the attachment points between the blanks by means of an upper male tool and a lower female tool. There is a dual purpose, namely to separate the blanks from one another and to make piles of blanks which can be processed subsequently by folding and gluing machines. 
     The process of processing the sheets  10  in the forming machine  1  ends in the discharging station  500  where the residual waste is discharged. The latter is released automatically and then discharged from the discharging station  500  by a belt. 
     The forming machine  1  has transporting means  600  which allow each sheet  10  to be moved individually from the exit of the introduction station  100  to the discharging station  500 . 
     In a fashion which is also very conventional, the transporting means  600  use a series of gripper bars  610  which are mounted so that they can move in transverse translation by means of two sets of chains  620  arranged laterally on each side of the forming machine  1 . Each set of chains  620  runs in a loop which allows the gripper bars  610  to follow a trajectory which passes successively through the die-cutting station  200 , the ejection station  300 , the receiving station  400 , and the discharging station  500 . 
     Concretely, each gripper bar  610  passes in a substantially horizontal plane of movement between a drive wheel  630  and a return wheel  640 , and then a returns in the upper part of the forming machine  1 . Once it has been returned to the drive wheel  630 , each gripper bar  610  is then capable of gripping a new sheet  10 . As can be seen more clearly in  FIG.  2   , each gripper bar  610  consists of a transverse bar  611  on which are mounted multiple grippers  612  which are designed so as to be able to grip the front edge of a same sheet  10  simultaneously. Each gripper bar  610  is coupled to two sets of chains  620  via the two ends of its transverse bar  611 . 
       FIGS.  1  to  3    show that the ejection station  300  is moreover equipped with a device  310  for holding each sheet  10  during its introduction stage. This holding device  310  comprises a suction member  320  which is responsible for partially retaining each sheet  10  by its rear part during the stage of introducing it into the ejection station  300 . Concretely, the suction member  320  holds the rear part of the sheet  10  without immobilizing it, allowing it to slide gradually as it moves in accordance with  FIG.  3   . 
     In order to do this, the suction member  320  has at least two motorized fans  13  with propellers  14 . The fans  13  are advantageously small commercially available fans, of the computer fan type, the propeller  14  being mounted rotatably in a frame  18  provided with screw fixing means ( FIG.  4   ). The fans  13  can all be identical. 
     The fans  13  are installed transversely at the entrance to the ejection station  300 , at the lower part of the station  300  so as to be positioned beneath the plane of movement P of the sheets, and hence be able to act in the region of the lower face of the latter ( FIG.  3   ). The fans  13  are distributed in a transverse direction T perpendicular to the longitudinal direction D of movement of the sheets in the forming machine  1  ( FIG.  5   ). 
     The axes of rotation A of the fans  13  are juxtaposed in order to cover substantially the whole width of the sheet  10 . They can be perfectly aligned or be installed in a longitudinally narrow transverse window  16 , the width Lf of which is, for example, less than ten centimetres. They may or may not be regularly spaced in the transverse direction T. 
     The axes of rotation A of the propellers  14  of the fans  13  are arranged substantially parallel to one another and perpendicularly to the plane of movement P of the sheets. 
     The direction of rotation of the propellers  14  and the orientation of the propellers  14  of the fans  13  are configured so as to generate, when functioning, a flow of air which is capable of applying suction to the rear of the sheet-like element  10  during the stage of introducing the said sheet  10  into the said waste ejection station  300 . 
     The number of fans  13  may lie between two and fifteen. It can be adjusted depending on the material of the sheets  10  and on their sizes in order to successfully retain the sheet and to generate a flow of air over substantially the whole width of each sheet  10  which is introduced into the waste ejection station  300 . 
     The holding device  310  can have a support table  11  in which at least two through orifices  12  are formed, the fans  13  being arranged beneath the support table  11 , at least partly opposite the opening of at least one through orifice  12  ( FIG.  6   ). 
     The support table  11  is a flat element arranged beneath the plane of movement P of the sheets. This can be a plate pierced with through orifices  12 , or a grid. The support table  11  can be a separate element of the frame of the waste ejection station  300  or can be entirely integrated into the frame. The fans  13  can be fixed directly beneath the support table  11 . When the support table  11  is a separate element, it is thus possible to easily equip workstations which are initially not provided with a system for holding the rear parts of the sheets. 
     This fixing of the fans  13  can be removable, which can make it possible to adapt the number of fans  13  fixed beneath the support table  11  depending on the forming operations  1  which are performed in the machine. This feature does indeed offer the possibility of increasing the number of fans  13  for large-size sheets  10  or reducing the number of fans  13  for low speeds and/or when working with relatively rigid sheets  10 . 
     The through orifices  12  are, for example, oblong holes extending in the longitudinal direction of movement D of the sheets. The through orifices  12  can be identical. 
     Additional through orifices  15  can be formed in the support table  11 , the number of orifices  12 ,  15  then being greater than the number of fans  13 . The additional orifices  15  are, for example, likewise oblong holes which are elongated in the same direction as the oblong through orifices  12  communicating with the fans  13 . The additional orifices  15  enable cushions of air to be formed between the sheet  10  and the support table  11 . 
     The holding device  310  can have a pilot control unit  17  configured so as to pilot-control the drive motors in rotation of the fans  13 . The pilot control unit  17 , such as a computer, a controller or a microcontroller, such as the computer of the forming machine  1 , has memories and programs which enable a series of instructions to be performed, in particular in order to pilot-control the stopping and starting of the fans  13 . 
     The fans  13  can be pilot-controlled by the pilot control unit  17  in order to function continuously, this being adapted for forming machines  1  functioning at very high speeds. It is, however, of course possible to provide a more or less discontinuous functioning mode of the fans  13 . In the same fashion, the fans  13  can function at constant power but it is perfectly possible to contemplate operating the fans  13  at a variable power level. This variable power can be obtained by varying the rotational speed of the propellers  14  of the fans  13 . This speed can be the same for all of the fans  13 . It can be reconfigured by the operator in particular to adapt the suction power of the fans  13  to the size and weight of the sheets  10  formed in the machine  1 . 
     The invention as defined has the advantage of generating effective holding of the sheets in the workstation at a relatively low cost. This ultimately allows the forming machine to be operated at high speed. 
     Of course, the invention also relates to any workstation  200 ,  300 ,  400  intended to equip a forming machine  1  and having a holding device  310  as described above. A waste ejection station  300  as in the particular embodiment chosen to illustrate the invention can be considered in particular here, but so too can a die-cutting station  200  or a receiving station  400  with blank separation. 
     However, even more generally, the invention furthermore relates to any forming machine  1  equipped with at least one workstation  200 ,  300 ,  400 .