Abstract:
An apparatus for gathering successive sheets of a scalloped stream in an adjustable receptacle has a pivotable first stop in front of and a longitudinally adjustable second stop behind the receptacle. The second stop is shifted, together with the conveyor for the stream, toward or away from the first stop when the length of the sheets forming the stream is changed. The effective width of the receptacle is adjusted when a stream of relatively narrow sheets is followed by a stream of wider sheets or vice versa.

Description:
CROSS-REFERENCE TO RELATED CASES 
     This application claims the priority of German patent application Ser. No. 198 49 859.4 filed Oct. 29, 1998. The disclosure of the German patent application, as well as that of each US and foreign patent and patent application mentioned in the specification of the present application, is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to improvements in apparatus for accumulating successive sheets of short or long series of sheets into piles or stacks of overlapping sheets at a stacking station, and for removing stacks from a sheet-gathering receptacle at the stacking station. More particularly, the invention relates to improvements in apparatus which can automatically remove successive freshly gathered stacks while the sheets continuously arriving at the stacking station gather into fresh or growing stacks of overlapping sheets. Apparatus of such character are known as sheet piling devices, and one thereof is described and shown in U.S. Pat. No. 4,436,472 granted Mar. 13, 1984 to Kunzmann. 
     The patent to Kunzmann discloses an apparatus wherein several stacking units are placed side-by-side. A drawback of the patented apparatus is that its design imposes limits upon the number of stacks or piles which can be gathered per unit of time with a requisite degree of accuracy. Moreover, the condition of the sheets is likely to be affected if the rate at which the sheets are supplied and stacked exceeds a relatively low threshold value. 
     Another drawback of conventional apparatus of the above outlined character is that they cannot be rapidly converted for the stacking of sheets having different sizes and/or shapes. This can result in prolonged interruptions of the operation and a considerable reduction of the output. 
     OBJECTS OF THE INVENTION 
     An object of the instant invention is to provide an apparatus which constitutes an improvement over and an advantageous further development of apparatus disclosed in the aforementioned U.S. Pat. No. 4,436,472 to Kunzmann. 
     Another object of the invention is to provide an apparatus which can be rapidly converted to gather larger or smaller, wide or narrower and/or shorter or longer sheets with the same degree of accuracy. 
     A further object of the present invention is to provide novel and improved means for manipulating one or more abutments for the growing stacks of paper sheets or the like. 
     An additional object of the invention is to provide a novel and improved method of manipulating successive sheets of a stream or flow of partially overlapping sheets in a stacking machine. 
     Still another object of the invention is to provide a sheet stacking apparatus which can gather sheets of different thicknesses and/or other characteristics with the same degree of accuracy and predict-ability. 
     Another object of the invention is to provide a novel and improved method of manipulating scalloped streams of partially overlapping paper sheets or the like preparatory to and during conversion or gathering into stacks or piles. 
     Still another object of the invention is to provide an apparatus which can be reliably converted for the processing of sheets having different sizes and/or shapes within short intervals of time. 
     SUMMARY OF THE INVENTION 
     The invention resides in the provision of an apparatus for gathering successive sheets of a series of sheets (such as paper sheets) into growing stacks which are being gathered in and, when fully grown, are removed from a receptacle at a stacking station. The apparatus comprises means for conveying successive sheets of the series (e.g., successive sheets of a scalloped stream consisting of partially overlapping sheets) in a first direction (e.g., substantially horizontally) into the receptacle at the stacking station to thus accumulate in the receptacle a growing stack of overlying or overlapping sheets, front and rear abutments or stops for the sheets of a stack in the receptacle (the abutments are spaced apart from each other in the first direction and the front abutment is movable relative to the receptacle between operative and inoperative positions), means for withdrawing fully grown stacks from the receptacle in the first direction while the front abutment dwells in the inoperative position, means for transporting withdrawn stacks in a second direction (e.g., substantially horizontlly and substantially at right angles to the first direction) , and means for adjusting the rear abutment in and counter to the first direction. The conveying means can comprise a belt or chain conveyor or another suitable conveyor which can deliver to the receptacle sheets having different lengths, and the rear abutment is adjustable for the purpose and to the extent necessary to conform the spacing of the front and rear abutments from each other to the lengths of sheets being conveyed to the receptacle. 
     The apparatus can further comprise a platform which can resemble or constitute a rake and serves to separate the sheets. The platform is movable with the conveying means between a plurality of positions, such as forwardly and backwards (as seen in the first direction) and/or up and down. The movements of the platform in and counter to the first direction can take place in synchronism with movements of the withdrawing means (the latter can include gripper or holder means adapted to engage the front end portion of a fully grown stack and to pull the stack from the receptacle while the front abutment is maintained in its inoperative position). 
     The conveying means is or can be arranged to share the movements of the platform between a plurality of different levels. 
     In accordance with a presently preferred embodiment, the apparatus further comprises a carriage (such as a slide) for the aforementioned platform and for the conveying means, as well as an elevator which serves to move the carriage between a plurality of different levels. The carriage is movable (preferably relative to the elevator) in and counter to the first direction, and the elevator is movable up and down relative to the receptacle at the stacking station. 
     The mounting of the platform on the carriage is or can be such that the platform is movable relative to the carriage in and counter to the first direction through distances corresponding to the extent of adjustment of the rear abutment relative to the front abutment. 
     The forward end of the sheet conveying means is preferably disposed at a predetermined (fixed) distance from the platform. 
     The receptacle can be provided with an exchangeable bottom wall, and such bottom wall can include an exchangeable substantially strip-shaped holder as well as a plurality of sheet supporting rakes carried by the holder. The holder can further carry lateral stops and guide means for the lateral stops. 
     The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved apparatus itself, however, both as to its construction and its mode of operation, together with numerous additional important and advantageous features and attributes thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 a  is a schematic elevational view of an apparatus which embodies one form of the invention, a fully grown stack of overlapping sheets being about to be transferred from the stacking station onto an evacuating conveyor; 
     FIG. 1 b  shows the apparatus of FIG. 1 a  but in the process of gathering a next-following stack of sheets at the stacking station; 
     FIG. 1 c  shows the structure of FIG. 1 a  during a further stage of gathering the next-following stack at the stacking station and with the stack withdrawing unit retracted from the position of FIG. 1 b  back to the front stop at the stacking station; 
     FIG. 1 d  shows the structure of FIG. 1 c  but with the rear stop in a raised position; 
     FIG. 2 a  shows the apparatus of FIG. 1 a  but in the course of gathering a stack of sheets shorter than those shown in FIGS. 1 a  to  1   d;    
     FIG. 2 b  shows the apparatus of FIG. 2 a  but during gathering of a next following stack of shorter sheets; 
     FIG. 3 is an enlarged fragmentary partly sectional view of a detail in the apparatus of FIGS. 1 a  to  1   d ; and 
     FIG. 4 is a plan view of the detail shown in FIG.  3 . 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     The apparatus which is shown in FIG. 1 a  comprises a stack collecting receptacle  4  which is located at a stacking station  1  and receives successive sheets  2  of a scalloped stream of (partially overlapping) sheets to gather a series of successive stacks  3  of overlapping sheets. As a rule, or at least in many instances, the improved apparatus comprises a battery of two or more receptacles  4  each of which receives successive sheets of a discrete scalloped stream of sheets  2 , i.e., each of which gathers a discrete series of stacks  3 . The receptacles  4  are located one behind the other, as viewed in FIG. 1 a.    
     The sheets  2  of the stream shown in FIG. 1 a  are conveyed by a belt or band conveyor  7  which is operated to advance the partially overlapping sheets in the direction of the arrow  6 . The receptacle  4  of FIG. 1 a  is followed by a stack withdrawing or removing unit  8  including grippers or tongs  5 , and the tongs  5  are followed by an evacuating conveyor  9 . The latter is designed to transport the (withdrawn) stacks  3  sideways, i.e., at right angles to the plane of FIG. 1 a . In this embodiment, the conveyor  9  comprises stack-advancing endless belts  11  with integrated pneumatic table segments  12 . 
     The sheets  2  of the growing stack  3  in the receptacle  4  are bounded by a front or downstream abutment or stop  13  and a rear or upstream abutment or stop  14  (as seen in the direction of the arrow  6 ). The front abutment is pivotable between an operative position (see FIG. 1 b ), in which it is located in front of and at a level above the growing stack of sheets  2  in the receptacle  4 , and an inoperative or retracted position (FIG. 1 a ) at a level beneath the bottom part of the receptacle. 
     The rear abutment or stop  14  can comprise several sections (the same holds true for the abutment  13 ) and is mounted on a slide or carriage  16  which is movable in directions indicated by a double-headed arrow  15 . The carriage  16  further supports the conveyor  7  as well as a rake-like platform  17  which serves as a separator and is movable with and also relative to the carriage  16 . The platform  17  can perform (relative to the carriage  16 ) strokes of variable length. 
     The discharge or downstream end  18  of the conveyor  7  is located at a fixed distance from the platform  17 . The carriage  16  is mounted on and is movable relative to a support  21  which can be said to constitute an elevator because it is movable up and down in directions indicated by a double-headed arrow  19 . 
     The receptacle  4  comprises a bottom wall or panel  22  which includes a plurality of parallel supporting rakes  23  secured to a strip-shaped holder  24  (see FIGS.  3  and  4 ). The holder  24  is provided with transversely extending guides  26  for lateral stops  27  which can be fixed in selected guides  26 , in dependency upon the format (size) of the sheets  2  and stacks  3 , by distancing members. 
     Several bottom panels  22  can be assembled with suitable lateral stops  27  into preassembled groups or modules which are held in positions of readiness for eventual use in a manner and for purposes as will be described hereinafter. 
     The mode of operation is as follows: 
     FIG. 1 a  shows a fully assembled pile or stack  3  consisting of a predetermined number of sheets  2  being confined in the receptacle  4 . The front abutment  13  (or the illustrated one of two or more front abutments) is already pivoted to its inoperative position, and the gripper or tongs  5  of the illustrated withdrawing unit  8  is ready to advance the freshly assembled stack  3  in the direction of the arrow  6 , namely onto the evacuating conveyor  9 . The latter is designed to advance the thus received stack  3  in a direction toward or away from the observer of FIG. 1 b.    
     The illustrated gripper  5  of the withdrawing unit  8  operates in synchronism with the platform  17  which comprises the aforementioned supporting rake and shares the forward movement of the fully assembled stack  3  in the direction of the arrow  6 . FIG. 1 b  shows a fully assembled stack  3  on the conveyor  9  and the next-following (growing) stack  3  in the process of growing on top of the platform  17 . Thus, the delivery of sheets  2  by the conveyor  7  need not be interrupted while the trailing abutment  14  establishes a path for advancement of successive sheets  2  of the scalloped stream of sheets toward and against the front abutment  13  which (see FIGS. 1 b  and  1   c ) is again in the operative position in which it intercepts the oncoming sheets  2 . 
     The support or elevator  21  descends, as indicated by the lower half of the arrow  19  (FIG. 1 c ) , to lower the platform  17  so that it reaches or descends even below the level of the panel  22 , and is thereupon retracted to the position shown in FIG. 1 d . Such manipulation of the elevator  21  results in the deposition of the growing stack  3  of sheets  2  on the panel  22  of the receptacle  4 . 
     The next step involves an upward movement of the elevator  21  (as indicated by the upper half of the arrow  19 ); this entails a lifting of the discharge end  18  of the conveyor  7  to a level such that it rises at the rate at which the height of the growing stack  3  on the platform  22  increases. Such mode of operation is desirable and advantageous because each sheet  2  of successively delivered sheets supplied by the conveyor  7  descends through the same distance. This contributes to uniformity of the successively accumulated stacks  3 . 
     FIGS. 2 a  and  2   b  illustrate the manner in which the improved apparatus can be adjusted to permit for the accumulation of stacks of sheets smaller or larger than the sheets  2  shown in FIGS. 1 a  to  1   d . The carriage  16  is moved in one of the directions indicated by the double-headed arrow  15 , and this results in identical movements of the rear abutment  14  as well as of the discharge end  18  of the conveyor  7  and of the platform  17 . Thus, the distance between the abutments  13  and  14  is reduced accordingly (it is assumed here that the carriage  16  has been moved in a direction to the right, as viewed in FIG. 1 a ). 
     If one desires to change the effective width of the receptacle  4 , i.e., to stack narrower or wider sheets, it is merely necessary to replace the aforementioned module  22 ,  27  with a different module. 
     The extent of movement of the platform  17  in or counter to the direction indicated by the arrow  6  is changed as a function of change of the distance between the front and rear abutments  13  and  14 . The length of the forward stroke of the gripper  5  remains unchanged due to the absence of any appreciable changes of the forward stroke of the stack removing unit  8 . In fact, the length of the forward stroke is reduced if the format (size) of the sheets  2  is reduced. 
     An important advantage of the improved apparatus is that the just discussed changes of the format of the stacks  3  can be carried out in a simple and time-saving manner. This is accomplished by the provision (a) of the carriage  16  which supports the platform  17  and the rear or upstream abutment  14 , and (b) of the means for moving the carriage  16  up and down (arrow  19 ) as well as forwardly and backwards (arrow  15 ). Furthermore, the carriage  16  supports the conveyor  7  at a fixed distance from and above the platform  17 . 
     Another advantage of the improved apparatus is that the aforedescribed changes of the format can be carried out without necessitating any changes in the position and/or movements of the front or downstream abutment(s)  13 . This, in turn, ensures that the stroke or strokes of the gripper or grippers  5  can remain unchanged. 
     A further important advantage of the improved apparatus is that the discharge end  18  of the sheet supplying conveyor  7  and the platform  17  share the movements in directions indicated by the double-headed arrow  19 ; this ensures that the extent of descent of successive sheets  2  from the conveyor  7  into the receptacle  4  is the same while a stack  3  is in the process of growing in the receptacle as well as during withdrawal of a fully grown stack from the receptacle (while the conveyor continues to deliver sheets toward and beyond the discharge end  18 ). 
     An additional important advantage of the improved apparatus is that the carriage  16  (which is movable in directions indicated by the double-headed arrow  15 ) carries the conveyor  7 , the rear abutment  14  and the platform  17 . This renders it possible to complete any required adjustments within a surprisingly short interval of time, i.e., the parts  7 ,  16  and  17  can be adjusted as a unit. 
     Additional savings in time and space are achieved by the provision of the elevator  21  which is movable up and down (arrow  19 ) and supports the carriage  16  in such a way that the latter is movable in directions indicated by the arrow  15 . Such practically universal movability of the carriage  16  with and relative to the elevator  21  contributes to simplicity and predictability of stacking of sheets in the receptacle  4  as well as to rapid conversion of the apparatus for the stacking of larger, smaller, narrower or wider sheets. The movements of the platform  17  in dependency on the selected format of stacks  3  can be simplified and rendered more precise by selecting the extent of movements of the platform in directions indicated by the arrow  15  to conform to the selected distance between the front and rear abutments  13  and  14 . 
     The features which are illustrated in and which were described with reference to FIGS. 3 and 4 contribute to a simplification of adjustments which are to be carried out when the conveyor  7  is to deliver narrower sheets  2  following the delivery of a series of wider sheets or vice versa. 
     An advantage of the feature that the mounting of the front abutment  13  can remain unchanged when the length of the sheets  2  is changed from shorter to longer or vice versa is that the strokes which are being performed by the grippers  5  can remain unchanged. This simplifies the design of the stack withdrawing unit  8  as well as of the evacuating conveyor  9 . 
     To summarize: The improved apparatus renders it possible to simplify the conversion from the stacking of sheets having a first format to the stacking of sheets having a different second format and to enable the persons in charge to complete the conversion within a surprisingly short interval of time. Furthermore, the components which render such conversion possible are simple, compact and inexpensive. 
     Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic and specific aspects of the above outlined contribution to the art of apparatus for accumulating and transporting stacks of paper sheets and the like and, therefore, such aaptations should and are intended to be comprehended within the meaning and range of equivalence of the appended claims.