Abstract:
A sheet stack changing device for a sheet processing machine having a main stack lifting mechanism and a remaining-stack carrying device. The remaining-stack carrying device has bars for temporarily holding a remaining stack, a drive mechanism for moving the bars forward into the stack and retracting the bars from the stack in a staggered relation to one another. The remaining-stack carrying device is raised by a lifting mechanism. A pulling mechanism connects the bars with a carrying rail slidably engaged on the remaining-stack carrying device so that the carrying rail slides forward with the bars and retracts independently from the bars.

Description:
FIELD OF THE INVENTION 
     The present invention relates to sheet-fed printing machines and, more particularly to an improved stack changing device for sheet feeders of sheet-fed printing machines. 
     BACKGROUND OF THE INVENTION 
     It is a known practice, in sheet feeders for sheet-fed printing presses or other sheet-processing machines, to provide arrangements for automated stack change. These may consist of rack-type structures, so-called remaining-stack carrying devices, which are provided with thrusting and lifting drives for the horizontal and vertical movement. Such so-called non-stop stack changers are suited, for example, during the printing of paper sheets, i.e. in machine running, to take over remainders of finished sheet stacks from, for example, a pallet with grooves, and to deposit them again on a new sheet stack subsequently installed in the sheet feeder. Known devices are distinguished by high constructive and assembly expenditure and require special constructions of the sheet feeders. Further, devices are used here, the remaining-stack carrying device of which have a rack engaging into the grooves of the pallet. This rack is to be removed in the joining of the remaining stack with the newly installed sheet stack as a whole between the two stack parts. This involves high drive forces and places very strong stresses on the sheets lying next to the section point. Furthermore, restraining means are to be provided which prevent a shifting of the stack parts, and, in the process, severely strain the stack edges. Furthermore, the operation of the sheet feeder itself is severely hindered or even rendered impossible. The sheet flow is difficult to control in the changing operation, so that waste sheets result again and again. 
     Devices have already been developed that partly avoid some of the disadvantages described. 
     Thus, from DE 3931710 C2 there is known a nonstop sheet feeder for sheet-fed rotary presses. It has a remaining-stack carrying device which is arranged underneath a conveyor table leading from the sheet feeder to the sheet-fed rotary press. The remaining-stack carrying device has a closed frame on which there are arranged nonstop rods which can be driven as piston rods of individual cylinders by means of a pressure medium and which are drivable into grooves of a pallet carrying a sheet stack. In the driven-in state, the nonstop rods lie on both sides of the frame and they are to be removed in succession out of the range of the sheet feeder. Nothing is said about the operating sequence. The control of the nonstop rods is very expensive and is not directly adaptable to the requirements of the stack changing operation. 
     A sheet feeder is known from DE 4 203 500 A1. It has, parallel to the sheet feeder, and allocated to this on the face side, an auxiliary stack-carrying device as an independent component. With this, over a common drive, individually drivable pointed bars are provided that are drivable in grooves of a pallet carrying a sheet stack. The drive system has individual chain drives that are coupleable onto the particular pointed bars. For the guidance and accessibility of the chain drives there are required special construction measures. The chain drives are unclamped constantly under a stand of a frame of their own and they completely block the space in from of the sheet feeder, so that the latter is not accessible. In the stack-changing process, the pointed bars in the joining of main stack and remaining stack are removed, first on the outside, then in the middle and last in the zone between the pointed bars already pulled from the stack zone, so that a gentle depositing of the remaining stack onto the sheet stack is produced. For this purpose the chain drives are coupled in an expensive manner onto the pointed bars such that the pointed bars can be driven only in common. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     In view of the foregoing, an object of the present invention is to provide an improved stack changing device which overcomes the problems associated with prior art designs. 
     A more specific object of the present invention is to provide a stack changing device which allows for simple and continuous stack changing through the use of a drive that is optimally adapted to the desired stack changing conditions. 
     The present invention provides these and other advantages and overcomes the drawbacks of the prior art by providing a stack changing device with an improved pulling mechanism for moving the remaining-stack carrying bars. 
     It is advantageous that remaining-stack bars are provided which are movable independently from one another, and which are pulled, intermittently, out of the stack zone. The simple and compact drive proposed for this purpose makes possible the space-saving arrangement of the remaining-stack carrying device. A different height of the remaining-stack bars generates a smooth depositing movement of the remaining-stack onto the sheet stack. The continuous removal of the remaining-stack bars from the inside, outward, and in two stages, makes possible a gentle depositing of the remaining-stack onto the sheet stack. As the remaining-stack bars are formed with differing length, there results an improved work run-off. Further improvements are brought about by a staggering of the speed of the individual remaining-stack bars to one another. 
     These and other features and advantages of the invention will be more readily apparent upon reading the following description of preferred exemplary embodiments of the invention and upon reference to the drawings wherein: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevation view of an illustrative embodiment of a sheet feeder constructed in accordance with the present invention, 
     FIG. 2 is a plan view of a sheet feeder, 
     FIG. 3 is a plan view of a remaining-stack carrying device, 
     FIG. 4 is a plan view showing the remaining stack carrying device of FIG. 3 taking over of a remaining stack, 
     FIG. 5 is a plan view showing a stacking device during the stack changing, 
     FIG. 6 is an enlarged partial plan view showing the drive for moving the remaining stack bars, 
     FIG. 7 is an enlarged partially cut away view of the cable deflection rollers, and 
     FIG. 8 is a plan view showing the cable pull operation. 
    
    
     While the invention will be described and disclosed in connection with certain preferred embodiments and procedures, it is not intended to limit the invention to those embodiments. Rather it is intended to cover all such alternative embodiments and modifications as fall within the spirit and scope of the invention. 
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In FIG. 1 a sheet feeder  2  is represented connected with a sheet-processing machine, for example with a sheet-fed printing press  1 . In the sheet feeder  2  there is installed a sheet stack S for processing. The sheet stack S can be lifted by means of a main-stack lifting mechanism, which is not represented in detail here, in the rhythm of the sheet processing. The sheets of the sheet stack S are singled on its upper side and fed to the sheet printing press  1  in a sheet stream. In the sheet feeder  2  there is provided for this a sheet singling arrangement  4  which is equipped with a considerable number of multiple operating elements for the format-dependent adjustments, and for adjustments of the supplying of suction or blast air. The operating elements serve for the attuning of the various functions of the sheet singling device  4  to the appropriate transport of the sheets from the sheet feeder  2  to the sheet-fed printing press  1 . In the sheet feeder  2  there is arranged, further, a remaining-stack carrying device  3 , which is allocated to the face side of sheet feeder  2  facing away from the sheet-fed printing press  1 . The remaining-stack carrying device  3  is provided with a frame  6 , in which remaining-stack bars  7  are borne longitudinally slidably. By means of the frame  6 , the remaining-stack carrying device  3  is suspended on a remaining-stack lifting mechanism  5 , which here is only indicated in its position. The remaining-stack lifting mechanism can lift a remaining-stack H from the remaining-stack carrying device in the rhythm of the sheet processing and is controllable synchronously with the main stack lifting mechanism. 
     In FIG. 2, the sheet feeder  2  is shown in a top view. Upon the sheet feeder  2  there follows in the sheet running direction indicated by arrows, a conveyor table  20 , over which the sheet stream generated by the singling is transported to the sheet processing machine, for example the printing press  1 . Further, the position of the sheet singling device  4  allocated to the rear edge of the sheet stack S is shown. The orientation of the remaining-stack bars  7  is represented in its arrangement in relation to the sheet feeder  2 , in which only the two outer remaining-stack bars  7  are represented, and the others are indicated with effect lines. The position shown is the waiting position outside of the operating zone of the sheet feeder  2 . The remaining-stack bars  7  are guided within the remaining-stack carrying device  3 , so that they occupy a horizontal position. The remaining-stack carrying device  3  with its frame  6  is guided in the sheet feeder  2  by means of the guide rails  8 , and is vertically movable. The remaining-stack lifting mechanism  5  is located on the upper side of the guide rails  8 , it engages from there on the frame  6  of the remaining-stack carrying device  3 , and moves this latter up and down on the guide rails  8 . 
     In FIG. 1 it is shown that the remaining-stack carrying device  3  is installed by means of the guide rails  8  directly into the sheet feeder  2  and can be lifted over the entire height of the sheet singling device  4 . The remaining-stack lifting mechanism  5  is raisable and lowerable while supplying a sheet processing machine, for example the printing press  1 , with sheets and the remaining-stack carrying device  3  is movable outside of the processing zone for proper stack change. By means of this arrangement of the sheet feeder  2 , the latter is very well accessible from its face-side operating side. 
     In FIG. 3 there is shown a complete representation of the remaining-stack carrying device  3 . The frame  6  is vertically guided on the guide rails  8 . In the frame  6  in a front carrying rail  9  there are guided the remaining-stack bars  7  in the form of carrying bars  7 A and of spacing bars  7 B. On a rear carrying rail  10  there is arranged a pull drive  11  for the singled pulling of the carrying bars  7 A and spacing bars  7 B. The position shown is the waiting position. Further, drives  12  are provided on both sides for the longitudinal shifting of the rear carrying rail  10  on guide rails  13  of the frame  6 . The drives  12  determine the position of the rear carrying rail  10  on the rear end of, or within, the frame  6 . The front carrying rail  9  is firmly joined with the frame  6 . The carrying bars  7 A and spacing bars  7 B are of different height. The carrying bars  7 A, for example, are about twice as high as the spacing bars  7 B. By height there is meant the extension of the carrying bars  7 A or spacing bars  7 B perpendicular to the extended plane of the remaining-stack carrying device  3 . The effect of this measure will again be thoroughly shown in the following representations. 
     The carrying bars  7 A and spacing bars  7 B can be of equal length. In a preferred form of execution the carrying bars  7 A, however, are longer than the spacing bars  7 B. In the taking-over of a remaining-stack H, the carrying bars  7 A serve first of all for the load reception, and they are to be dimensioned correspondingly, in which context the load is to be deflected into a further carrying means (see FIG.  4 ). 
     In FIG. 4 there is shown the remaining-stack carrying device  3  in operation. The carrying bars  7 A as well as the spacing bars  7 B are thrust forward by means of the drives  12 , together with the rear carrying rails  10 , with respect to the front carrying rail  9 , and introduced into grooves of a pallet P carrying the sheet stack S. Front-carrying rail  9  and rear-carrying rail  10  with the pull drive  11  now lie parallel in front of the pallet P that carries a remainder of a sheet stack  5 , the so-called remaining stack H. The pallet P and the remaining stack H are not touched there by the front carrying rail  9 . The longer and higher carrying bars  7 A lie on a remaining-stack lifting rail  14  on the front end (as seen in the sheet-running direction) in the sheet feeder  2 . This remaining-stack lifting rail  14  is coupled with a lift drive and provided for support of the carrying bars  7 A as well as for their lifting during the production. Both the remaining-stack lifting rail  14  and the remaining-stack lifting mechanism  5  are connected for this purpose with the auxiliary stack lifting device, or at least they are mechanically or controllably coupled with one another so that in the stack processing, but especially in the bringing-together of the remaining stack H with a new sheet stack S, they can be synchronously lifted. 
     From FIG. 4 it is further to be perceived that in the represented position of the remaining-stack carrying device  3  with the carrying bars  7 A and the spacing bars  7 B, the space within the frame  6  is free and the frame  6  is open to the rear. In this preferably monitored zone which here is shown shaded, operating procedures can be performed. For this handling it is likewise of importance that the carrying bars  7 A and spacing bars  7 B are slidable into the grooves of the pallet P early, i.e. long before the required changing process. The remaining-stack carrying device  3  can be raised in common with the sheet stack S until the stack change must actually occur. Then the remaining stack H only remains to be lifted from the pallet P. When the remaining-stack bars  7  are again pulled (i.e. the stack joining has occurred), the remaining-stack bars  7  are preferably immediately driven back into the new pallet P. 
     In FIG. 5 the interrelation of the pulling movement to the arrangement is once again clarified within the sheet feeder  2 . The carrying bars  7 A and the spacing bars  7 B lie alternately in grooves of a pallet P (in which context one must imagine oneself as lying on the webs between the grooves of the pallet P, perpendicular to the sheet stack S). The carrying bars  7 A lie there on the remaining-stack lifting rail  14 . The same holds in the illustrated cases for the inner spacing bars  7 B which have only half the height of the carrying bars  7 A. The pulling process of the carrying bars  7 A begins with the carrying bars  7 A lying next to the stack middle, which, as shown, are pulled as a pair. There the remaining-stack H in this zone comes to lie continuously on the thinner spacing bars  7 B. The pulling of the thicker carrying bars  7 A and then of thinner spacing bars  7 B occurs smoothly and in close time sequence, but always separately from one another. For this a device for controlling the pull movement is provided. 
     The stack-changing, therefore, proceeds as follows: 
     I.—On reaching of a minimum height of the sheet stack S the stack-changing process is started. 
     II.—The carrying bars  7 A and the spacing bars  7 B are thrust in common from the frame  6  into the grooves of the pallet underneath the sheet stack S, the sheet stack S remaining free (open) on the rear side to the remaining-stack carrying device  3 . 
     III.—The carrying bars  7 A are undercut by the remaining-stack lifting rail and lifted until the remaining stack H is carried by the carrying bars  7 A. 
     IV.—The pallet P is lowered and removed from the sheet feeder  2 . 
     V.—The remaining stack H is further raised continuously by means of the auxiliary stack-lifting drive system for the singling of the sheets. 
     VI.—A new sheet stack S is installed in the sheet feeder  2  and raised by means of the main-stack lift. 
     VII.—On contacting of the upper side of the sheet stack S with the underside of the carrying bars  7 A the pulling process of the carrying bars  7 A is initiated. 
     VIII.—The carrying bars  7 A are pulled out individually or in pairs from inside outward, from between the remaining stack H and the sheet stack S. 
     IX.—The remaining-stack H is deposited continuously onto the spacing bars  7 B, from inside outward. 
     X.—The auxiliary stack-lifting rail becomes free, the remaining-stack carrying device  3  no longer takes on any load, the remaining spacing bars  7 B still have only a control function for the stack unification. 
     XI.—The spacing bars  7 B are continuously pulled out from inside outward, from between the remaining stack H and the sheet stack S. 
     XII.—The remaining stack H continuously comes to rest, from inside outward, onto the top side of the sheet stack S. 
     In a further form of execution, it can be provided not to use all of the remaining-stack carrying bars  7 A. Thus, in the case of very thick sheet materials which as a result of their stability can sink only slowly into the interspace becoming greater between sheet-stack S and remaining-stack H, the spacing bars  7 A can be omitted. Therewith the changing process is accelerated, since the time necessary for the pulling process of the spacing bars  7 B is saved. 
     As to the formation of the device for pulling the remaining-stack bars  7  it is already recognizable in part from FIGS. 3 and 4. Details and functioning are shown in greater detail in FIGS. 6,  7  and  8 . 
     The remaining-stack bars  7  are represented in part as differently formed carrying bars  7 A and spacing bars  7 B, and they lie in the front carrying rail  9  and the rear carrying rail  10 . The carrying bars  7 A are longer and about twice as thick as the spacing bars  7 B. All the remaining-stack bars  7  are provided at their end with a deflection roller  30  for the guidance of a cable  40 . In correlation with this on the rear carrying rail  10  there are arranged further deflection rollers  31  for the cable  40 . Cable  40  is so led by means of rollers  30  that the remaining stack bars are loaded toward the carrying rail  10 . Cable  40  in this state is largely wound around a cable drum  41 . The end of cable  40  is not firmly joined with the remaining-stack bars  7  but is movable both in common with these and also independently therefrom. The carrying rail  10  can be constructed to undercut the remaining-stack bars  7  or to limit their movement to the rear with impact. In order to move the remaining-stack bars  7 , the rear carrying rail  10  is moved on guide rails  13  by means of a drive  12 . Drive  12  can be constructed as a pressure-medium drive or as an electric motor drive. For the sliding-in of all the remaining stack bars  7  into the grooves of the pallet P, these are thrust forward in common by the drive  12 , by means of the carrying rail  10  up to the front carrying rail  9  (FIG.  4 ). 
     For the pulling-out of the remaining-stack bars  7 , the rear carrying rail  10  is first driven back independently from the remaining stack bars  7 , by means of drive  12  going back into the starting position shown in FIG.  3 . There, the remaining-stack bars  7 , first at least the carrying bars  7 A are clamped between the remaining stack-stack H and sheet stack S. They do not follow the movement of the rear-carrying rail  10 . For this, the cable  40  is unrolled from a cable drum  41  arranged on the rear-carrying rail  10 , which is releasable under control for this purpose. Cable  40  then runs over the cable rollers  30  and is stretched in zig-zag form between the remaining-stack bars  7  and the rear-carrying rail  10 . After this, the remaining-stack bars  7  are pulled out of the stack zone by means of the cable  40 . For this a cable drive  42  is provided which is likewise arranged on the rear carrying rail  10 , the cable drive engages on the cable drum  41  and sets the latter into rotation. The rear carrying rail  10  is blocked by the drive  12  and takes up the tensile force from cable  40 . 
     For the staggered pulling of the remaining-stack bars  7 , on the rear carrying rail  10  there is provided, further, a locking mechanism which in dependence on the position of individual remaining-stack bars  7 , either frees or blocks adjacent remaining-stack bars  7  for the pulling movement. For the control of the pulling movement, the remaining-stack bars  7  themselves can be used. Therewith it is made possible that by means of the one cable  40  the remaining-stack bars  7  can be pulled in a fixed pattern offset to one another. 
     A further development of the drive device provides that two cable drums  41  are arranged parallel to one another on the rear carrying rail  10 . Then also two cables  40  are present, one cable  40  then being coupled with one half of the remaining-stack bars  7 . 
     Likewise, both cable ends can be fastened to the cable drum  41 . Then the cable  40  is guided outward from the carrying rail  10  by the deflection rollers  30  and is coupled in a cross bond from the outside of the carrying rail  10 . In this case, through a doubled pulling movement on the cable drum  40  there is yielded a doubling of the pull path. 
     In particular, the cable guidance can be provided in such manner that first the carrying bars  7 A, and only then the spacing bars  7 B, are pulled. For this, the cable  40  is first conducted in the described pattern over the deflection rollers  30  of the carrying bars  7 A and the corresponding deflection rollers  31  on the carrying rail  10 . Then it is led back from the ends of the carrying rail  10  to the middle, and then again in the described pattern over the deflection rollers  30  of the spacing bars  7 B and the corresponding deflection rollers  31  on the carrying rail  10 . In this case, the deflection rollers are mounted on the carrying bars  7 A or spacing bars  7 B, and the assigned deflection rollers  31  are installed on the carrying rail  10  in a both-sided orientation. The cable guidance then occurs, on the one hand above the carrying rail  10  and, on the other hand, underneath this carrying rail  10 . 
     The execution of the pull drive is not restricted to the use of a cable  40 . For this purpose another tension means can be used, for example, also a chain or a belt.