Abstract:
A printing press having an apparatus for determining the product thickness of a folded product which is fed to folding rolls for making a fold known as the third fold. The apparatus has measuring heads that are arranged on both sides of a folding roll bearing levers. For the purpose of presetting, the product to be folded is introduced slowly between folding rolls. The position of the folding rolls is determined, and a setting signal is generated therefrom and supplied to an actuating motor via a machine presetting means. The actuating motor sets the position of the folding roll levers, such that the folding rolls can be set relative to one another with regard to their mutual spacing, in accordance with the thickness of the folded product.

Description:
FIELD OF THE INVENTION 
     The invention relates to a printing press having an apparatus for folding printed products, and more particularly to an apparatus for folding printed products that has means for presetting folding rolls according to the thickness of the printed products. 
     BACKGROUND OF THE INVENTION 
     In printing presses such as web-fed offset rotary presses, the printed products often have to be folded. To that end, the printed webs are guided through a folding former and provided with a first fold, which is known as the longitudinal fold. Subsequently, the web is cut in the folder and provided with a further fold known as the first transverse fold. Webs are frequently laid on top of one another and web streams are guided via the folding former. If said streams are cut and fed to the transverse folding apparatus, it is possible to gather the cut printed products. At this point, depending on the desired end product, great differences may occur in the thickness of the printed products which are optionally to be provided with a second longitudinal fold. 
     While the first longitudinal fold and the first transverse fold do not require the web sections or web to be folded to be stopped, to produce the second transverse fold the product is to be guided through between two folding rolls and has to be stopped beforehand. A folding blade then pushes the folded product between the rotating folding rolls. 
     The folding rolls have to be at a well-defined distance in accordance with the thickness of the product to be folded. This requires the folding rolls to be adjusted to the thickness of the product that is to be folded. To that end, it is necessary to know the thickness of the product to be folded in order to adjust the folding rolls accordingly. 
     Conventionally, the product thickness or layer thickness has been measured manually, for example, using micrometers or similar instruments. The folding rolls for the third fold are then adjusted manually or by means of manual positioning commands from actuating drives in the machine that makes the third fold. 
     BRIEF SUMMARY OF THE INVENTION 
     In view of the foregoing, it is an object of the invention to measure automatically the thickness of the products which are to be folded, in particular the products which are to be provided with a second longitudinal fold, and to make it possible to convert the measured results automatically via the machine controller into actuating commands for positioning the folding rolls, in particular in the third fold, in order to preset the machine. 
     This object is achieved by the invention. In accordance with the invention, the position of an element which touches the product which is to be processed is measured by a measuring apparatus, and actuating signals for the machine presetting means are derived as a function of the position of said element. A machine presetting means then fixes the position of the folding rolls as a function of the measured thickness of the product. 
     The invention will be described in detail below using exemplary embodiments illustrated in the drawings, of which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are schematic views showing a measuring apparatus on folding rolls; and 
         FIGS. 2A and 2B  are schematic views showing a measuring apparatus on a brake shoe. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows schematically an exemplary embodiment of a device for producing a second longitudinal fold, also sometimes known as a third fold, in printed products of a printing press. For this purpose, the folded products  1  have to be stopped, for which purpose appropriate stops and brake elements in the form of belts or brake shoes are used. As mentioned earlier in the Background, the products  1  may have a variable number of individual printed sheets, which are to be folded or have been folded, in accordance with the desired end product. 
     Therefore, the separation between folding rolls  2  and  3  has to be set to the respective thickness of the folded product  1 . For this reason, it is necessary to know the thickness of the respective product which is to be folded. 
     After they have been stopped, the folded products  1  are pushed between the folding rolls  2  and  3  with the aid of a folding drum  4 . Prior to this, the folded products  1  are fed over a folding table or a sliding plate  5 , with the result that they come to lie in the desired position above the folding rolls  2 ,  3  after positionally correct stopping, and the second longitudinal fold can be produced in a positionally correct manner with the aid of the folding drum  4 . 
     The folding rolls  2 ,  3  can be pivoted by means of folding roll bearing levers  10 ,  11 , the folding roll bearing lever  10  bearing the folding roll  3 , and the bearing lever  11  bearing the folding roll  2 . The bearing levers  10 ,  11  are supported on bearings  6 ,  7  and are pulled together by a spring  12 , with the result that the folding rolls  2 ,  3  are pressed against one another if there is no folded product  1  between them. 
     The position of the folding roll bearing levers  10 ,  11  is changed by an actuating drive  13 , for which purpose a motor  14  and a suitable feedback means  15  are required. The folding roll bearing levers  10 ,  11  are adjusted by appropriate control of said parts, in such a way that the required distance between the folding rolls  2 ,  3  is set in accordance with the thickness of the respective folded product  1  on the sliding plate  5 . For this purpose, the machine presetting means becomes active in a known manner, said machine presetting means generating, as a function of the thickness of the folded product  1  measured according to the invention, signals which are fed to the motor  14 , with the result that the actuating drive  13  pivots the folding roll bearing levers  10 ,  11  appropriately. The actuating drive  13  can preferably comprise a threaded spindle which has threads with an opposing pitch. 
     Measuring heads  8 ,  9  are arranged on both sides of the folding roll bearing levers  10 ,  11 . The measuring heads  8 ,  9  detect the positions of the levers  10 ,  11  which are used according to the invention to determine the thickness of the folded product  1  on the sliding plate  5 . 
     In a novel way, the folding rolls  2 ,  3  move into the zero position during the alignment of the folding unit, that is to say they touch. This is possible if there is no folded product  1  between the folding rolls  2 ,  3 , as can be seen in  FIG. 1A .  FIG. 1B  shows how a folded product  1  is situated between the folding rolls  2  and  3 , with the result that the latter are moved apart from one another, counter to the pressure of the spring  12 . The folding blade of the folding drum  4  between the folding rolls  2 ,  3  brings about this pressing apart of the folding rolls  2 ,  3  when the folded product  1  is fed into the nip between the two folding rolls. As a result, the relative position of the folding roll bearing levers  10 ,  11  is changed. The position of the folding roll bearing levers  10 ,  11  thus changes proportionally with respect to the thickness of the folded product  1  when the latter is pushed in between the folding rolls  2 ,  3 . This position of the folding roll bearing levers  10 ,  11  is detected by the measuring heads  8 ,  9 . The readings of the measuring heads  8 ,  9  are sent to a controller  20 , which processes the readings to determine the separation between the folding rolls  2 ,  3 . This separation corresponds to the thickness of the folded printed product. The controller  20  then generates control signals for actuating the motor  14  based on the measured thickness of the printed product. In response to the actuation signals, the motor  14  moves the actuating drive  13  in such a way that the folding rolls  2 ,  3  can be preset to the respective thickness of the folded products  1 . 
     In a prior application by the same applicants which was filed on Jan. 27, 2004 at the German Patent Office with the designation PB 04645 and whose contents are incorporated into the present application, a circuit is known for easier setting of a system of a product web processing machine, which system is dependent on the thickness of a product web. Here, a transmitter of a measuring head and a receiver are arranged on each side of the product web, with the result that reflected beams are measured as a function of the thickness of the product web and measured values can thus be generated as a function of the thickness of the web. It is possible to use said measured values in a computer to form measured signals in accordance with the web thickness. This circuit, which is described in detail in said prior application, can be used advantageously to activate the motor  14  and a suitable feedback means  15 , the measuring heads  8 ,  9  not being arranged on both sides of the product web or folded products but in each case on a folding roll bearing lever  10 ,  11  in the present invention, in a deviation from the prior application. 
       FIGS. 2A and 2B  illustrate a second exemplary embodiment in which, in a manner according to the invention, the determination of the thickness of the folded product  1  for the purpose of setting the folding rolls  2 ,  3  shown in  FIG. 1  is carried out with the aid of a brake shoe  18  for braking the folded products  1 , which are fed in on the surface of a sliding table  17 . 
     In a manner analogous to the arrangement of the measuring heads  8 ,  9  shown in  FIG. 1 , a measuring head  19  is arranged at a distance above the brake shoe  18  in the exemplary embodiment according to  FIGS. 2A and 2B . According to the invention, a differential measurement is carried out, likewise in a manner analogous to the differential measurement according to  FIG. 1 . 
     The differential measurement of the position of a brake shoe  18  or of a similar element takes place with and without a printed product which is to be folded between said component and the sliding table  17 . The result of this is the determination of the product thickness and generation of an actuating signal for presetting the folding rolls. The thickness of the printed products  1  is determined from the differential measurement of the position with respect to the sliding table  17 . 
     By way of example, in  FIG. 2A , the brake shoe  18  is initially against the surface of the sliding table  17 , without there being a folded product  1  between the brake shoe  18  and the sliding table  17 . In this state without a printed product  1 , the position of the brake shoe  18  is determined. In  FIG. 2B , the folded product  1  is moved to a position underneath the brake shoe  18 . The position of the brake shoe  18  in this state is also measured, and the difference between the two measured brake shoe positions is determined. It can be seen that this position difference measured by the measuring head  19  corresponds to the thickness of the folded product  1 . 
     An actuating signal for a motor is generated from the measured thickness, for example, in an analogous manner to the illustration according to  FIG. 1 . Using the actuating signal, the distance of the folding rolls can be set with respect to one another in accordance with the thickness of the folded product  1 . For this purpose, it is also once again advantageously possible to use the circuit according to the above mentioned prior application. However, other circuits can also be used readily for the exemplary embodiments according to  FIGS. 1 and 2 , within the scope of the capabilities of the person skilled in the art, to carry out the setting operations on the folding rolls based on the determined thicknesses of the folded products. 
     The application of the principle according to the invention for determining the thickness of the folded products is not limited to the exemplary embodiments shown in  FIGS. 1 and 2 . Rather, further possibilities using the principle on which the invention is based are available to the person skilled in the art, using which principle said person skilled in the art can perform the folding roll presetting operations in a manner which is dependent on the product thickness.