Abstract:
A former roller, which is driven for rotation, is located at the intake of a former for a folding unit. A controller unit is utilized to control the rotation of the motor, which drives the former roller, in such a way that the former roller exerts a tensile force on a material web that is fed to the former roller.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention is directed to a method and devices for folding with a former.  
         BACKGROUND OF THE INVENTION  
         [0002]    Customarily, a former is provided with a former roller, by use of which a web of material, brought in to the former from a side, is rerouted downwardly into the former. The former roller is driven by a motor at a regulated speed for avoiding imposing a tensile load on the web of material. The roller rotates with a circumferential speed matched to the conveying speed of the web and avoids the exertion of a tensile load on the web.  
           [0003]    Errors can occur in the course of processing the web of material in the folding apparatus with the result being that a considerable amount of material is conveyed into the folding apparatus, which material can no longer be correctly processed in the folding apparatus and which material thus piles up before the folding apparatus, and a device which is located upstream of it, such as, for example a printing press from which the material is supplied, can be brought to a stop. Such a pile-up of material can result in damage to the folding apparatus. To limit the amount of material which can pile up at one location, it is generally known to provide cut-off devices along the conveying path of the material, which devices cut off the web of material in the event of a malfunction. If the leading end of the web of material, which leading end is being created in the course of the cut-off, is successfully moved out of the conveying path, this results in a limitation of the amount of material which can pile up in the folding apparatus, and the danger of damage is thereby reduced. On the other hand, because of the cut-off, the tension in the web of material, which tension is present during normal operations, collapses, so that pile-ups of material can result at other locations, in particular in a device upstream of the folding apparatus, such as a printing press.  
           [0004]    DE 44 28 593 A1 describes a device for measuring and regulating the tension in a web in a former area. In the course of the use of this device, the force of the web acting on the former is detected and the former roller is controlled as a function of this force.  
           [0005]    DE 41 37 818 A1 discloses a device for setting the web tension. A number of revolutions of traction rollers arranged downstream of a former can be mutually regulated.  
           [0006]    DE 297 23 888 U1 discloses a linear former with a driven former inlet roller.  
           [0007]    A device for folding webs of material is known from U.S. Pat. No. 5,449,156. A web tension is changed by changing the number of revolutions of a traction roller.  
         SUMMARY OF THE INVENTION  
         [0008]    The object of the present invention is based on providing a former for a folding apparatus.  
           [0009]    In accordance with the present invention, this object is attained by providing a former with a former roller at the entrance to the former. The former roller is driven by a motor. In the event of the detection of an error, the web of material being directed to the former is cut. The former roller continues to rotate after the web of material has been cut. The former roller is driven by its drive motor at a web tension level which is less than half of the web tension level which exists during error free operation.  
           [0010]    The advantages which can be gained by the invention consist, in particular, in that because of the manner in which the motor rotation is regulated, it is possible to avoid the complete collapse or elimination of the tension in the web of material prior to the web&#39;s entry into the folding apparatus if the web of material is cut off in the folding apparatus because of the appearance of a malfunction. In the course of braking the folding apparatus and a device located upstream of it, material continues to be conveyed out of the upstream-located device, and a pile-up of material in the upstream-located device, which would possibly be difficult to clear up or which could result in damage to the upstream-located device, is prevented. In such a case, the material of the web can collect to a considerable extent in the former without leading to damage. The collected material can be removed from the former with little effort.  
           [0011]    The regulating device for the former is preferably provided with a sensor for use in detecting a traction force exerted by the former roller on the web of material. The regulating device regulates the rotation of the motor in such a way that this traction force is maintained substantially constant. Such a sensor can detect, for example, a force exerted on a bearing of the former roller or a force exerted on another roller rerouting the web of material. The sensor can be formed by an array of sensors for use in measuring the conveying speed of the web of material and the power consumption of the motor, from which measured values conclusions can be drawn regarding the force exerted by the former roller on the web of material.  
           [0012]    In accordance with an alternative embodiment of the present invention, the regulating unit can contain a sensor for use in detecting a conveying speed of the web of material. The regulating unit then regulates the rotation of the motor in such a way that the former roller maintains a substantially constant lead over the web of material.  
           [0013]    To assure that, in the case of a tear in the web of material, or a cut-off of the web of material, the traction force of the former roller continues to act on the web of material, at least one roller for use in pressing the web of material against the former roller is suitably provided. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    Preferred embodiments of the present invention are represented in the drawings and will be described in greater detail in what follows.  
         [0015]    Shown are in:  
         [0016]    [0016]FIG. 1, a schematic representation of a former in accordance with a first preferred embodiment of the present invention, in  
         [0017]    [0017]FIG. 2, a schematic representation of a second preferred embodiment of the former, and in  
         [0018]    [0018]FIG. 3, the former after a web of material has been torn or cut off in the folding apparatus. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]    A schematic section through a former  01  of a folding apparatus, in accordance with a first preferred embodiment of the present invention, is represented in FIG. 1. The former  01  is substantially constructed of two lateral walls  02 , which extend downward toward each other. A former roller  03 , or a former inlet roller, is mounted, rotatingly driven by a motor  04 , on the upper edge of one of the lateral walls  02  and is used for rerouting a web of material  06 , which is conveyed to the former roller  03  in the horizontal direction from a web-fed printing press  07 , represented as a dashed rectangle, into the former  01 . The former roller  03  is embodied as a former inlet roller  03 , which is arranged directly at the former inlet and which is driven at a web tension which is less than one-half of the web tension during error-free folding.  
         [0020]    The web of material  06  is conveyed between two folding rollers  08 , which are arranged at the bottom of the former  01 , to a transverse folding device which is not specifically represented, which transverse folding device separates the web of material  06  into separate sheets, which separate sheets subsequently are to be transversely folded.  
         [0021]    The web of material  06  is maintained pressed against the former roller  03  by a presser roller  12 . The presser roller  12  can have the shape of a cylinder that is substantially extending over the length of the former roller  03  and that is parallel with it. Alternatively, the presser roller  12  can be constituted by one or by several wheel disks of lesser width which are mounted on a common shaft.  
         [0022]    Two sensors  11 ,  13  are connected to a regulating unit  09 , as seen in FIG. 1. The sensor  11  is used for detecting a conveying speed of the web of material  06 . The sensor  13  is used for detecting the rotary speed of the motor  04 . The sensor  11  can be arranged, for example, on the plate cylinder of the web-fed printing press  07  in order to detect the rotational speed or the circumferential speed of the plate cylinder. The sensor  13  is arranged on the driveshaft of the former roller  03 . The sensor  13  detects a traction force exerted by the former roller  03  on the web of material, for example, and a conveying speed of the web of material  06 . With this configuration it is the object of the regulating unit  09  to regulate the rotating speed of the former roller  03  in such a way that as constant as possible a lead exists between the former roller  03  and the web of material  06  rerouted at it. The former roller  03  thus has an “advance” with respect to the web of material which should be maintained constantly and which should keep the web of material  06  under tension prior to the web of material  06  reaching the former roller  03 . The result of this tension is that the former roller  03  has a slightly greater rotational speed than the linear speed of the web of material  06  running off on it. The difference between the two speeds is a function of the size of the lead, or of the traction force exerted by the former roller  03  on the web of material  06 . To maintain the lead constant, the regulating unit  09  therefore regulates the operation of the motor  04  in such a way that the circumferential speed of the former roller  03  is greater, by a preset small differential amount, than the linear speed, detected by the sensor  11 , of the web of material  06  itself.  
         [0023]    In a second preferred embodiment of the present invention, as shown in FIG. 2, the sensor  11  for detecting the speed of the web of material  06  is replaced by a sensor  14  which measures, for example, the strength of an electrical current supply of the motor  04 . Based on this electrical current strength, and on a known supply voltage of the motor  04 , the regulating unit  09  can draw conclusions regarding the output of the motor  04  in this second preferred embodiment. By employing the speed of the former roller  03 , detected by the sensor  14 , the regulating unit  09  can draw conclusions regarding the force which the roller exerts on the web of material  06 . Thus, the regulating unit  09  can regulate the operation of the motor  04  in such a way that, during normal operations, the traction force exerted by the former roller  03  on the web of material  06  remains substantially constant.  
         [0024]    In this way, it is assured by application of both of the two preferred embodiments, that the web of material  06  is under a substantially constant tension between the outlet of the web-fed printing press  07  and the former roller  03 .  
         [0025]    If a malfunction occurs in the folding apparatus so that the web of material  06  can no longer be properly processed, it is necessary to bring the folding apparatus and the web-fed printing press to a stop as rapidly as possible in order to prevent the material of the web of material  06 , which can no longer be processed, from piling up at an undesirable location, and from possibly being wound around a roller of the web-fed printing press  07  or of the folding apparatus and resulting in damage to the press  07  or to the folding apparatus. By way of example, it is first to be assumed that the malfunction is in the form of a tear of the web of material, which material web tear results in the tension of the web of material  06 , at the location of the former  01 , collapsing. The web of material  06  is no longer pulled out of the bottom of the former  01 . Since, in the case of the first preferred embodiment of the invention in accordance with FIG. 1, the former roller  03 , which is coupled with the rotation of the plate cylinder of the web-fed printing press  07 , continues to run until the web-fed printing press  07  has come to a complete stop, the web of material  06  continues to be pulled off the output of the web-fed printing press  07  by the former roller  03  and is therefore prevented from piling up, or accumulating, at an inaccessible location in the web-fed printing press  07  and thus from possibly causing damage there. The material is instead collected in the former  01 , as is depicted schematically in FIG. 3, from which collection area it can be easily removed after the web-fed printing pres  07  and the folding apparatus have come to a stop.  
         [0026]    In the case of the second preferred embodiment of the invention in accordance with FIG. 2, in case of a malfunction, the former roller  03  is initially rotated, until the regulating unit  09  notices, on the basis of the result of the determination by the sensor  13  that the former roller  03  is stopped, because the web of material  06  is tightly stretched between the output of the stopped web-fed printing press  07  and the former roller  03 , or that the former roller  03  now rotates freely because the web of material  06  is interrupted between it and output of the web-fed printing press  07 . In these two cases the regulating unit  09  then switches the motor  04  off. The result in this second embodiment is also that web material is collected in the former  01 , from which it can be easily removed afterwards.  
         [0027]    If a malfunction is detected in the folding apparatus or in the web-fed printing press  07 , the web of material  06  is generally severed at one or at several locations by the operation of automatic cut-off devices, one of which is arranged in the inlet area of the folding apparatus in such a way that, when it cuts the web of material  06 , the tension of the latter collapses in the area of the former  01 . The result is the same as in the above considered case of the tear in the web of material. The portion of the web of material  06 , which is located downstream in the conveying direction from the cut location, is no longer drawn out of the former  01 , and web material is collected in the former  01  until the web-fed printing press  07  has come to a stop. The former roller  03  continues to rotate, for example until the stop of cylinders of a folding apparatus or the stop of cylinders of the printing groups. With the web tension collapsed, the former roller  03  is driven in the area of the former.  
         [0028]    While preferred embodiments of a method and devices for folding with a former, in accordance with the present invention, have been set forth fully and completely hereinabove, it will be apparent to one of skill in the art that various changes in, for example, the structure of the web-fed printing press, the type of material web being conveyed, and the like could be made without departing from the true spirit and scope of the present invention, which is accordingly to be limited only by the appended claims.