Abstract:
A method for controlling a feeder of a gathering-stitching machine reduces the operating effort when setting the feeder, increases reliability when laying folded sheets on a transport device and improves quality during collating and stitching. Opening and closing times of grippers are regulated under program control, continuously and as a function of format when controlling the feeder of the gathering-stitching machine. Data relating to the dimensions and to the number of pages of the folded sheets is thus entered into a control device, from which data actuating signals for actuating elements of the grippers are generated.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority, under 35 U.S.C. §119, of German Patent Application DE 10 2011 120 994.1, filed Dec. 14, 2011; the prior application is herewith incorporated by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to a method for controlling a feeder of a gathering-stitching machine, in which folded sheets are separated one after another by at least one gripper from a stack of a magazine and laid on a transport device, and opening and closing the gripper and actuating a stitching device are carried out under remote control by actuating signals from a control device. 
     German Published, Prosecuted Patent Application DE 1 100 043 discloses a gripper for a bookbinding machine for gripping and firmly holding sheets, the closing movement of which is initiated by actuating a pneumatic operating cylinder. If the operating cylinder is placed under vacuum or pressurized with compressed air, then a gripper finger fixed to a piston rod is drawn-in counter to the force of a spring. The pressurized or vacuum air is fed to the operating cylinder through a control valve, which is controlled by an adjustable cam disk in such a way that the gripper force is regulated. A cam disk has a fixed actuating characteristic corresponding to the cam curve. No details relating to the adjustment of the cam disk are disclosed in that application. 
     In printing presses, it is also known from German Patent DE 42 21 929 C2, corresponding to U.S. Pat. No. 5,390,601, to control the movement of grippers connected to a drum by using a computer, so that rapid adaptation to changing operating conditions is possible, and the gripper force can be set as a function of the printing material. The gripper movements are controlled with a pneumatic piston-cylinder unit, with the actuating position of the piston being regulated with the aid of a displacement measuring system as a function of the rotational angle of the drum, through the use of a set point/actual comparison. In the patent, there is no more detailed explanation as to which printing material characteristic variables play a role in calculating actuating positions of the piston. 
     A gatherer-stitcher described in German Published, Non-Prosecuted Patent Application DE 197 52 017 A1 includes a plurality of folded sheet feeders. The rotational speed of the drums of a feeder can be retarded or accelerated, depending on the paper quality, with the speed of a gatherer chain being uniform. 
     A gatherer-stitcher described in German Published, Non-Prosecuted Patent Application DE 198 41 265 A1 reveals the provision of sensors which measure the length and width of the folded sheets in a feeder of the gatherer-stitcher. A register stop can be set automatically by using the sensor signals. The grippers holding the folded sheets during a delivery are conventionally actuated through the use of a cam mechanism. 
     SUMMARY OF THE INVENTION 
     It is accordingly an object of the invention to provide a method for controlling a feeder of a gathering-stitching machine, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known methods of this general type, which reduces the operating effort when setting the feeder, which increases the reliability when laying folded sheets on a transport device and which improves the quality during collating and stitching. 
     With the foregoing and other objects in view there is provided, in accordance with the invention, a method for controlling a feeder of a gathering-stitching machine. The method comprises separating folded sheets one after another from a stack of a magazine using at least one gripper, laying the separated folded sheets on a transport device, opening and closing the at least one gripper and actuating a stitching device under remote control using actuating signals from a control device, and generating the actuating signals from data relating to dimensions and number of pages of the folded sheets. 
     According to the invention, when controlling a feeder of a gathering-stitching machine, the opening and closing times of grippers are regulated under program control, continuously and as a function of format. For this purpose, data relating to the dimensions and to the number of pages of the folded sheets is entered into a control device, from which data actuating signals for actuating elements of the grippers are generated. As a result of the automated separation of folded sheets, it is possible to vary the switching and reaction times on a product basis. When pneumatic controllers are used, the number of mechanical components can be reduced, so that low production costs arise. As a result of a low number of mechanical wearing points, the reliability of the feeder is improved. Marks on the folded sheets can be avoided, in that the gripping forces can be set variably. 
     Other features which are considered as characteristic for the invention are set forth in the appended claims. 
     Although the invention is illustrated and described herein as embodied in a method for controlling a feeder of a gathering-stitching machine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
     The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1  is a diagrammatic, perspective view of a gathering-stitching machine having a plurality of feeders; 
         FIG. 2  is a cross-sectional view of a feeder; 
         FIG. 3  is a side-elevational view of a separating drum with pneumatic operating cylinders; 
         FIG. 4  is a cross-sectional view showing a pair of grippers of a separating drum, operated by operating cylinders; 
         FIGS. 5.1-5.3  are perspective views of folded sheets and dimensions thereof; and 
         FIG. 6  is a schematic diagram of a control device for a feeder. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the figures of the drawings in detail and first, particularly, to  FIG. 1  thereof, there is seen a gathering-stitching machine which includes, inter alia, three feeders  2 - 4  disposed one after another in a production direction  1 , a stitching station  5  and a cross-conveyor  6 . Folded sheets  7 - 9  which are separated in the feeders  2 - 4  are laid one above another astride on an endlessly circulating gathering chain  10  and are conveyed to the stitching station  5 . In the stitching station  5 , the collated folded sheets  7 - 9  are joined to one another by spine wire stitching. After the cross-conveyor  6 , the folding sheets  7 - 9  which are joined to one another are given a new production direction  11  for onward transport to a trimmer. 
     As is seen from the sectional illustration of the feeder  3  in  FIG. 2 , folded sheets  7  are located in such a way as to be stacked one above another in a magazine  12 . The base of the magazine  12  lies at an angle to the horizontal. The folded sheets  7  rest with their folded leading edges on a register rail  13  and with their side edges on lateral edge stops  14 . The lateral stops  14  can be set to a spine length L of the folded sheets  7  through the use of a motor  15  and a spindle drive  16  in a direction  17  at right angles to the plane of the sheet. The motor  15  is connected to a control device  18 . 
     In order to separate the folded sheets  7  from the underside of the folded sheet stack, suction grippers  20  are disposed underneath an opening  19  in the base of the magazine  12 . The suction grippers  20  are fixed to a hollow shaft  21  and can be pivoted about an axis of the hollow shaft  21  at a separation cycle rate. 
       FIG. 2  illustrates a situation in which a separated folded sheet  7 . 1  has been transferred from the suction grippers  20  into mechanical grippers  22  of a separating drum  23 . The separating drum  23  rotates about its shaft  24  in a direction  25 . A folded sheet  7 . 2  preceding the separated folded sheet  7 . 1  is held in further mechanical grippers  26  of the separating drum  23 . The grippers  26  are located diametrically opposite the grippers  22  in relation to the shaft  24 . 
     During a further rotation of the separating drum  23  in the direction  25 , the folded sheet  7 . 2  comes with its leading edge against a pocket-like stop  27 . The stop  27  can be pivoted about the shaft  24  in a direction  30  in a manner corresponding to folded sheet widths B 1 , B 2  by a motor  28  and a gearbox  29 . The motor  28  is connected to the control device  18 . 
     Two further drums  31 ,  32 , which are disposed underneath the separating drum  23 , rotate in opposite directions as shown by the direction of arrows  33 ,  34 .  FIG. 2  shows a situation in which a folded sheet  7 . 3  preceding the folded sheet  7 . 2  is opened through the use of the drums  31 ,  32 . While the folded sheet  7 . 3  lies with its leading edge against the stop  27 , the ends of the folded sheet  7 . 3  running after it on the separating drum  23  were gripped by double grippers  35 ,  36  of the drum  31 . The lap of the folded sheet  7 . 3  has been transferred from the top grippers  36  to grippers  37  of the opener drum  32 . The folded sheet  7 . 3  is drawn apart at the ends and allowed to fall over the gathering chain  10 . The folded sheet  7 . 3  is laid over a folded sheet  7 . 4 , which has already been laid on the gathering chain  10  through the use of the feeder  2 . 
       FIGS. 3 and 4  show a pneumatic controller of the movement of the grippers  22 ,  26  of the separating drum  23 . The separating drum  23  includes two drum disks  23 . 1 ,  23 . 2 , which are seated in a rotationally fixed manner on the hollow shaft  24 . Disposed between the disks  23 . 1 ,  23 . 2  are pneumatic operating cylinders  38 ,  39 , from each of which two respective pneumatic control lines  40 . 1 - 40 . 4  lead to channels  41 . 1 - 41 . 4  in the interior of the shaft  24 . A supply of compressed air for the operating cylinders  38 ,  39  is carried out through rotary lead-throughs  42 . 1 - 42 . 4 , each disposed at the end of a respective channel  41 . 1 - 41 . 4 . Operating piston rods  43 ,  44  of the operating cylinders  38 ,  39  are connected to levers  45 . 1 ,  45 . 2 ,  46 . 1 ,  46 . 2 , which are seated in a rotationally fixed manner on gripper shafts  47 . 1 ,  47 . 2 ,  48 . 1 ,  48 . 2  of the grippers  22 ,  26 . A pair of grippers  22 . 1 ,  26 . 1 ;  22 . 2 ,  26 . 2  is disposed on each disk  23 . 1 ,  23 . 2 . As the piston rods  43 ,  44  are moved in and out of the operating cylinders  38 ,  39 , the gripper shafts  47 ,  48  have a torque applied to them which effects closing and opening of the grippers  22 ,  26 . 
     The grippers  22 ,  26  are opened and closed on the basis of the dimensions and the number of pages n of the folded sheets  7 . Depending on whether a trailing fold sheet NF with B 1 &lt;B 2 , ( FIG. 5.1 ), a leading fold sheet VF with B 1 &gt;B 2  ( FIG. 5.2 ) or a folded sheet with equal fold widths with B 1 =B 2  ( FIG. 5.3 ) is involved, the dimensions illustrated in  FIG. 5  are taken into account. Further dimension-based data are the sheet thickness d and the grammage G. 
     The performance of the method is to be described below by using the schematic diagram illustrated in  FIG. 6 : 
     The control device  18  includes, inter alia, an input device  49  for operator entries, which is connected to a computer  50 . The computer  50  contains a memory for operator entries relating to the following variables: sheet width B 1 , sheet width B 2 , spine length L, grammage g, number n of pages, type of fold such as trailing fold sheet NF, leading fold sheet VF or sucker sheet suck, and pressure set point p (sp) . 
     In the computer  50 , the variables which are entered are processed and lead to pre-setting of various elements in the feeders  2 - 4 . The spine length L results in a pre-setting of the side stops  14  on the magazine  12  by using the motor  15 . The sheet width B 2  leads to a pre-setting of the register stop  27  using the motor  28  and of the gripper opening angle α o  of the grippers  22 ,  26  on the separating drum  23 . Both sheet widths B 1 , B 2  are used in order to preset the gripper closing angle α c  of the grippers  35 - 37  on the drums  31 ,  32 . The spine length L, the sheet widths B 1 , B 2  and the sheet thickness d result in a pre-setting of a thickness monitoring device, a wire feed and a clincher tool belonging to the stitching station  5  and a height of a stepper belt. The gripping forces F of the grippers  22 ,  26  of the separating drum  23  are preset by using the sheet thickness d. The predefined pressure set point p (sp)  exerts some influence in presetting the gripping force F and the switching time t sw  of two-way valves  51 . 1 - 51 . 4 , which are connected to the rotary lead-throughs  42 . 1 - 42 . 4 . The switching time t sw  of the valves  51 . 1 - 51 . 4  is controllable, for which purpose there is a connection  52  between the valves  51 . 1 - 51 . 4  and the computer  50 . 
     The pressure set point p (sp)  is transmitted through a connection  53  from the computer  50  to a pressure controller  54 . The actual pressure p (act)  is transmitted from the pressure controller  54  through a connection  55  to the computer  50 , where a comparison with the pressure set point p (sp)  is carried out continuously. If the pressure set point p (sp)  and actual pressure p (act)  agree, the switching time t sw  remains constant. If p (act) &gt;p (sp) , the switching time t sw  required for this actual pressure p (act)  is passed on to the valves  51 . 1  to  51 . 4 . Furthermore, the information to reduce the pressure p sp  is transmitted to the pressure controller  54 . If p (act) &lt;p (sp)  then the switching time t sw  required for this pressure p (act)  is likewise transmitted to the valves  51 . 1 - 51 . 4  and the information to increase the pressure to p (sp)  is passed on to the pressure controller  54 . With the aid of the pressure controller  54  and the feedback of p (act) , it is possible to ensure that the gripper opening angles and gripper closing angles needed for sheet separation continually remain constant. 
     In addition to the p (sp)  calculated in accordance with the program, provision is made that an operator can at any time during the operation manually predefine the desired positive pressure p (sp)  individually for each feeder  2 - 4  without disrupting the running production. Following the manual intervention, the regular set point-actual comparison between p (sp)  and p (act)  is again carried out. 
     All of the settings and changes are stored in the computer  50 . In the case of identical subsequent jobs, this data can be retrieved. This reduces the setup time, so that the operating costs are reduced. 
     The compressed air for actuating the grippers  22 ,  26  is provided by a pump  56 , which is connected to the pressure controller  54  through a maintenance unit  57 . The compressed air is provided from the pressure controller  54  to the valves  51 . 1 - 51 . 4  through a connection  58  which, in accordance with the two-way switching, passes on the compressed air through the rotary lead-throughs  42 . 1 - 42 . 4  to the operating cylinders  38 ,  39 . The drive of the drums  23 ,  31 ,  32  is carried out synchronously through the use of the control device  18 , with a rotary encoder  59  on the shaft  24  being used to output the current rotational speed and the current rotational angle a of the drum  23  to the control device  18  and to the computer  50 . 
     The invention is not restricted to the exemplary embodiment described. Automatic control of the gripper movements can also be carried out for the grippers  35  to  37  of the drums  31  to  32 . Instead of pneumatic actuating elements, it is also possible for electric or electromagnetic actuating elements to be used.