Abstract:
Apparatus for accumulating successive stacks of superimposed sheets on discrete pallets employs a conveyor which delivers a continuous imbricated stream of sheets to a stacking station where a pallet descends with an elevator and gathers a first stack. A separating finger is inserted into the accumulation of sheets at the stacking station at a level above the topmost sheet of the fully grown first stack. The thus obtained gap is increased by lowering the finger at a speed less than that of the elevator, the increased gap receives a positioning member which attracts the lower part of the growing second stack by suction, a table is inserted into the increased gap between the partitioning member and the fully grown stack, the fully grown stack and its pallet are withdrawn from the stacking station and replaced with a fresh pallet, the table and the partitioning member are withdrawn from the stacking station so that the growing second stack descends onto the second pallet, and the above-enumerated sequence of steps is tereupon repeated.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to improvements in methods of and in apparatus for manipulating sheets of paper, cardboard, metallic foil, plastic material or the like. More particularly, the invention relates to improvements in methods of and in apparatus for accumulating successive stacks of superimposed sheets on discrete supports in the form of platforms such as pallets or the like. Still more particularly, the invention relates to improvements in methods of and in apparatus for introducing empty supports (hereinafter called platforms or pallets) into and for withdrawing or otherwise removing filled pallets from a stacking station wherein a continuously advancing layer or stream of sheets is converted into a succession of stacks or piles each containing a preselected number of superimposed sheets and each supported by a discrete pallet.  
           [0002]    It is already known to introduce into a stacking station successive empty pallets at intervals which are required to gather on each empty pallet a stack or pile of superimposed sheets or to place onto each introduced empty pallet a fully grown stack of superimposed sheets. Empty pallets must be introduced at a rate and in a manner to ensure that they cannot interfere with movements of preceding pallets at, and with evacuation of preceding (loaded) pallets from, the stacking station.  
           [0003]    Successive sheets of a stream or flow of sheets are normally obtained by repeatedly severing a running strip or web of paper, foil or the like and by feeding successive sheets from the severing station to a stacking station. The apparatus at the stacking station is arranged to convert the stream into a succession of discrete stacks each of which contains a predetermined number of superimposed sheets and each of which is supported by a discrete pallet. Filled or loaded pallets must be withdrawn from the stacking station in a manner and at a rate to permit for the introduction of empty pallets in good time to ensure that each introduced empty pallet can receive a growing stack or a fully grown stack following the finished stack on the loaded pallet. Problems which arise in conventional aparatus are attributable, either primarily or exclusively or to a certain extent, to the fact that the stacking apparatus receives or should receive or can receive a continuous (uninterrupted) flow or stream of discrete sheets which are or which can be partly superimposed upon each other. The formations of sheets in a series or flow of partially overlapping sheets are known as imbricated patterns.  
           [0004]    German patent application Serial No. 36 16 470 A1 (filed by Martini et al. on May 15, 1986 and published Jun. 26, 1987) discloses a method of and an apparatus for accumulating successive piles of superimposed sheets at a stacking station. The apparatus is intended to ensure a reasonably problem-free evacuation of filled pallets from and a reasonably problem-free introduction of empty pallets to the stacking station. Successive sheets of the imbricated stream of partly overlapping sheets are fed into the stacking station by an endless belt conveyor and are gathered on a descending first pallet in such a way that each preceding sheet is fully overlapped by the next-following sheet. A separating finger is thereupon introduced into the stacking station to overlie the topmost sheet of the completed stack and to be overlapped by the first (lowermost) sheet of the next-following (growing) stack. The inserted finger descends at a speed less than that of the pallet and of the fully grown stack on the pallet to thus cause the formation of a clearance between the topmost sheet of the finished stack and the lowermost sheet of the growing stack. The clearance receives a first clamping jaw and the finger is thereupon withdrawn and lifted to a level above the topmost sheet of the next fully grown stack. The just described sequence of steps is thereupon repeated, i.e., the finger is introduced into the pile of superimposed sheets at a level such that it is located above the number of sheets piled up above the first clamping jaw and required to form a second fully grown stack above the stack below the inserted first clamping jaw (i.e., above the stack on the pallet). The thus inserted separating finger is again caused to descend at a speed less than that of the descending fully grown stack on the pallet. The thus obtained fresh (second) clearance receives a second clamping finger. The second fully grown stack (namely the stack between the two clamping jaws) is thereupon clamped by such jaws in that one of the jaws is moved toward the other jaw.  
           [0005]    In a next-following step, the lower clearance is enlarged in that the pallet and the fully assembled stack thereon are lowered so that the lower clearance can receive a table which intercepts the clamping jaw and the (second) stack between the two clamping jaws. This renders it possible to evacuate the pallet and the fully grown stack thereon from the stacking station and to introduce an empty pallet which receives and supports the second fully grown stack. This involves the withdrawal of the table and a lowering of the clamped stack so that the first clamp is immediately adjacent the introduced empty pallet. The second clamp is lifted slighty above and further away from the first clamp to thus release the fully grown second stack. A lowering of the first clamp is not possible because this clamp is immediately adjacent the freshly introduced second pallet. The first clamp is thereupon withdrawn so that the second stack can descend onto the second pallet, the second clamp is withdrawn in a next-following step and the aforedescribed sequence of steps is thereupon repeated in connection with the second pallet, the second stack and a third stack which is being or which has been gathered above the second stack.  
           [0006]    A drawback of the just described conventional method and apparatus is that the number of steps to be carried out in connection with the gathering and removal of successive stacks is rather high as well as that the apparatus is bulky and its manipulation must be effected by resorting to a complex control system. Furthermore, the frequency at which filled pallets can be withdrawn from, and empty pallets can be introduced into, the stacking station has a relatively low upper limit.  
         OBJECTS OF THE INVENTION  
         [0007]    An object of the invention is to provide a novel and improved method of gathering successive stacks or piles of superimposed sheets at a stacking station and of manipulating the supports (such as platforms or pallets) for the stacks in a manner which is simpler than but at least as reliable as heretofore known undertakings.  
           [0008]    Another object of the present invention is to provide a method which can dispense with the step of clamping successively gathered fully grown stacks of sheets between pairs of clamping jaws or the like.  
           [0009]    A further object of the invention is to provide a method which can dispense with the step or steps of lifting any parts which are inserted into the accumulation of superimposed sheets at the stacking station.  
           [0010]    An additional object of the present invention is to provide a novel and improved apparatus for the practice of the above outlined method.  
           [0011]    Still another object of the invention is to provide an apparatus which need not employ clamping jaws for fully grown stacks of sheets at the stacking or gathering station.  
           [0012]    A further object of the invention is to provide an apparatus which is simpler, more compact and less expensive than heretofore known apparatus for palletizing stacks of paper sheets or the like.  
           [0013]    Another object of the invention is to provide novel and improved means for establishing and varying the dimensions of clearances in the accumulation of superimposed sheets at the stacking station.  
           [0014]    An additional object of the invention is to provide novel and improved distancing means for use between the piles of sheets at the stacking station of the above outlined apparatus.  
           [0015]    Still another object of the invention is to provide the apparatus with novel and improved means for reliably positioning certain sheets of the accumulation of sheets at the stacking station relative to the parts which are movable into and withdrawable from the stacking station and/or relative to the parts which are fixedly mounted at the stacking station.  
           [0016]    A further object of our present invention is to provide a novel and improved method of and a novel and improved apparatus for converting an imbricated stream of large or small sheets of metallic, plastic or other suitable material into a succesion of stacks each of which contains or can contain a desired number of superimposed sheets.  
           [0017]    Another object of the instant invention is to provide a novel and improved stack building and manipulating apparatus which can be utilized as a superior substitute for heretofore known apparatus serving to palletize stacks or analogous accumulations of superimposed sheets which can be utilized for the wrapping of various types of commodities as well as for numerous other purposes.  
         SUMMARY OF THE INVENTION  
         [0018]    One feature of the present invention resides in the provision of a method of supplying platforms (such as pallets) for stacks of a series of succesive sheets of paper, cardboard, metallic foil, plastic material or the like which are supplied to and are superimposed upon each other at a stacking station. The improved method comprises the step of depositing successive sheets of the series upon a first platform at the stacking station to thus accumulate on the first platform a first stack of superimposed sheets. The depositing step can be carried out by resorting to an endless belt conveyor having a upper reach which delivers successive sheets of the series from a source to the stacking station. On their way from the source to the stacking station, the sheets of the series can partially overlap each other and the source can include a device which repeatedly severs a continuous web of sheet material being supplied from a bobbin or the like.  
           [0019]    The depositing step includes lowering the first platform with the growing stack thereon and the method further comprises the steps of introducing a stack separating member sideways between the topmost sheet of the first stack and the next-following sheet of the series when the number of sheets in the first stack reaches a preselected number; utilizing the separating member to establish between the topmost sheet of the first stack and the next-following sheet of the series of sheets at the stacking station a gap; inserting a partitioning member between the separating member and the next-following sheet (the lowermost sheet of the growing stack) of the series; withdrawing the separating member from the stacking station so that the next-following sheet of the series (i.e., the lowermost sheet of the then growing stack) is free to descend onto the partitioning member; attracting the next-following sheet to the partitioning member by suction; increasing the width of the gap between the partitioning member and the first stack (this can be readily achieved by moving the first stack and the first platform downwardly relative to the desceding partitioning member); advancing into the thus widened gap a distancing member; evacuating the first stack and the first platform from the stacking station; transporting into the stacking station a second platform beneath the distancing member; removing the distancing member from the stacking station; thereupon interrupting the attracting step; and retracting the partitioning member from the stacking station so that the next-following sheet and the sheets above the next-following sheet (i.e., the growing stack or the lowermost growing stack then located at the stacking station) can descend onto the second platform.  
           [0020]    The depositing step can include conveying successive sheets of the series into the stacking station in a predetermined direction transversely of the direction of lowering the stacks of sheets at the stacking station (the conveying step can include advancing successive sheets of the series along a substantially horizontal path which ends at the stacking station), and the introducing step can include moving the separating member into the stacking station by advancing it in the predetermined direction.  
           [0021]    The step of increasing the width of the gap can include lowering the first stack at the stacking station at a first speed and lowering the separating member at the stacking station at a second speed which is less than the first speed so that the descending separating member lags behind the descending first platform.  
           [0022]    The inserting step can be carried out simultaneously with or can follow the withdrawing step.  
           [0023]    The attracting step can include drawing air into openings which are provided in the at least partially hollow partitioning member. Such attracting step normally involves drawing the underside of the next-following sheet of the series (i.e., the underside of the lowermost sheet of the stack which is in the process of growing above the fully grown stack being borne by the first platform) to the upper side of an apertured panel forming part of the partitioning member.  
           [0024]    The attracting step can be started upon completed deposition of at least one additional sheet of the series upon the just mentioned next-following sheet. The next-following sheet, the additional sheet and the sheets above the additional sheet (i.e., the sheets of the growing second stack) can be attracted to the partitioning member while the latter descends with but at a speed less than the speed of the first platform and of the fully grown (finished) stack on the first platform.  
           [0025]    The depositing step can include propelling successive sheets of the series against a stop at the stacking station so that each sheet which reaches the stop is located at the stacking station, and the method can further comprise the step of temporarily attracting the thus propelled successive sheets to the stop by suction.  
           [0026]    The distancing member can comprise a core which is movable into and from the stacking station and a cover which is movable with and relative to the core and includes a portion located between the core and the next-following sheet. The step of advancing the core and the cover of the distancing member into the widened gap can include moving the core into the widened gap and simultaneously moving the core relative to the cover in such a way that the speed of movement of the cover relative to the next-following sheet is zero or at least very close to zero.  
           [0027]    The method can further comprise the step of establishing a film of compressed air or another suitable compressed gaseous fluid between the distancing member and the lowermost sheet of the only stack or the lowermost stack then growing at the stacking station.  
           [0028]    Another feature of the present invention resides in the provision of an apparatus for supplying pallets or other suitable platforms for a series of successive sheets at a stacking station. The improved apparatus comprises means for conveying to the stacking station a series of successive sheets which are superimposed upon each other on arrival at the stacking station, an elevator which is arranged to suport a platform at the stacking station and to lower the platform thereon at a predetermined speed so that a growing stack of superimposed sheets supplied by the conveying means onto the platform descends therewith at the stacking station, a separating member which is arranged to be introduced into the stacking station between the uppermost sheet of a fully grown stack on the platform and the lowermost sheet of a growing next-following stack, means for lowering the introduced separating member at a speed less than the predetermined speed to thus establish a growing gap between the uppermost sheet of the fully grown stack and the lowermost sheet of the growing next-following stack, a partitioning member which is movable between a first position adjacent to and a second position within the gap as well as downwardly in the gap at a speed less than the predetermined speed to thus further increase the width (height) of the gap, means for temporarily attracting the lowermost sheet of the next-following stack to the partitioning member, and a distancing member which is movable between a first position adjacent to and a second position in the increased gap below the partitioning member.  
           [0029]    The conveying means is or can be arranged to supply to the stacking station an at least substantially continuous series of sheets, and the attracting means can include openings provided in the partitioning member and arranged to attract sheets at the stacking station to at least one selected portion of the partitioning member. The partitioning member can include mutually inclined sections. One of the sections has an upper side and the attracting means can further include at least one suction chamber provided in the partitioning member. The aforementioned openings can include suction ports provided in the upper side of the one section of the partitioning means, communicating with the at least one suction chamber and being arranged to attract the underside of the lowermost sheet of the next-following stack at the stacking station. The openings can include ports which are arranged to attract one side of the next-following (growing) stack at the stacking station.  
           [0030]    The improved apparatus can further comprise means for urging sheets away from the partitioning member during certain stages of operation of the apparatus, e.g., preparatory to withdrawal of the partitioning member from the gap. Such urging means can be designed in such a way that it includes certain parts of the attracting means. For example, the urging means can include a source of compressed air which is arranged to supply compressed air to openings forming part of the attracting means and provided in the partitioning member.  
           [0031]    The distancing member can be provided with openings which confront the underside of the lowermost sheet of the growing stack at the stacking station in the second position of the distancing member, and the apparatus utilizing such distancing member is further provided with means for supplying to the openings of the distancing member compressed air or another suitable compressed gaseous fluid in the second position of the distancing member and/or during movement of the distancing member from the second position to the first position. In accordance with a presently preferred embodiment, the distancing member includes a core which is provided with openings and a cover which overlies the openings of the core and is immediately adjacent the lowermost sheet of the growing stack at the stacking station in the second position of the distancing member as well as during movement of the distancing member from the second position to the first position. The cover is or can be impermeable to fluids. Such apparatus can further comprise means for moving the core and the cover relative to each other so that the speed of the cover relative to the lowermost sheet of the growing stack during movement of the core from its second position to its first position at least approximates zero speed.  
           [0032]    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 the modes of assembling and operating the same, 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 drawing.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0033]    [0033]FIG. 1 is a schematic partly elevational and partly vertical sectional view of an apparatus which can be utilized for the accumulation of continuously supplied sheets into successive stacks or piles and wherein the means for ensuring predictable introduction of empty platforms and predictable evacuation of loaded platforms is constructed and assembled in accordance with one presently preferred embodiment of the invention, the parts of the apparatus being shown in positions they assume during accumulation of a stack of superimposed sheets on a platform which is carried by a descending elevator;  
         [0034]    [0034]FIG. 2 shows the apparatus of FIG. 1 during that stage of operation which involves the introduction of a stack separating member between the topmost sheet of a fully grown stack on the platform and a growing second stack;  
         [0035]    [0035]FIG. 3 shows the apparatus during a stage of operation which involves separation of the fully grown stack from the growing second stack and the establishment of a gap between the two stacks by a suction-operated partitioning member;  
         [0036]    [0036]FIG. 4 shows the apparatus of FIGS.  1  to  3  during a stage of operation which follows retraction of the separating member from the stacking station;  
         [0037]    [0037]FIG. 5 illustrates the apparatus of FIGS.  1  to  4  during that stage of operation which involves attraction of a portion of the growing second stack to the partitioning member;  
         [0038]    [0038]FIG. 6 shows the apparatus of FIGS.  1  to  5  with the distancing means in a position between the fully grown stack and the partially grown stack thereabove;  
         [0039]    [0039]FIG. 7 illustrates the distancing means in a fully inserted position;  
         [0040]    [0040]FIG. 8 shows the apparatus with its parts in positions they assume upon removal of a platform with a fully grown stack thereon and introduction of an empty platform;  
         [0041]    [0041]FIG. 9 illustrates the apparatus with the partitioning member on its way toward the empty platform; and  
         [0042]    [0042]FIG. 10 shows the apparatus with its partitioning member in retracted position and the fully grown second stack directly supported by the second platform.  
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0043]    [0043]FIG. 1 illustrates certain relevant component parts of an apparatus  1  which is designed to accumulate a succession of stacks or piles of superimposed sheets  4  of paper, metallic foil, synthetic plastic material, cardboard or the like. The means for conveying successive sheets  4  of a series of sheets to a stacking station  6  and for depositing successive sheets first upon a first platform or pallet  12  comprises an endless flexible band, belt or chain conveyor  2  having an at least substantially horizontal upper reach or stretch which propels the sheets against the confronting sheet arresting and aligning upright surface  20  of a stop  8 . The trailing ends of the sheets  4  which abut the surface  20  descend in the direction of an arrow  14  adjacent to or in actual contact with an upright aligning member  10 , e.g., a wall, a plate or the like. The surface  20  and the confronting (right-hand) surface of the aligning member  10  in the apparatus  1  are preferably vertical or substantially vertical. The upper side of the illustrated pallet (first pallet)  12  is horizontal. The means for continuously or intermittently lowering the pallet  12  includes a suitable elevator  12 A the exact details of which form no part of the present invention.  
         [0044]    The operation of the elevator  12 A is preferably such that it lowers the first pallet  12  at a rate corresponding to the rate of delivery of sheets  4  by the upper reach of the endless flexible conveyor  2  so that the level  16  of the uppermost sheet  2  of the growing stack  30  on the intermittently (stepwise) but preferably continuously descending growing stack  30  remains at least substantially constant. Otherwise stated, the level  16  of successive uppermost sheets  4  of the growing column at the stacking station  6  relative to the upper reach of the conveyor is constant (unchanged).  
         [0045]    The stop  8  is provided with horizontal openings  18  in the form of bores, holes, channels or the like. Each such opening  18  extends from the upright sheet-arresting and aligning surface  20  to the other (rear or outer) surface  22  of the stop  8 . The character  24  denotes in FIG. 2 a suction chamber which is carried by or provided on or in the stop  8  and communicates with the adjacent ends of the openings  18 . The means for establishing and maintaining in the suction chamber  24  an appropriate subatmospheric pressure includes a pump  24 A or the like.  
         [0046]    The aligning member  10  for the trailing ends of the sheets  4  in the stack  30  on the pallet  12  is provided with openings in the form of windows or the like for the passage of a substantially finger-like stack separating member  26  and of a partitioning member  28 . Each of the members  26 ,  28  can enter into and can be withdrawn from the space bounded in part by the stop  8  and in part by the aligning member  10  and occupied by a growing or fully grown stack  30 , i.e., from the actual stacking station  6 .  
         [0047]    The means for moving the separating member  26  (hereinafter called finger for short) back and forth in directions indicated by a double-headed arrow  26 A includes a drive  32 . The finger  26  is also movable up and down, i.e., in the direction indicated by the arrow  14  and counter to such direction. The arrangement is such that the finger  26  is movable (in the directions indicated by the arrows  14  and  26 A as well as upwardly, as viewed in FIG. 1) independently of movements of all other parts in the apparatus  1 ; this finger is an inverted L-shaped member and includes a plate-like or rod-like upright section  34  which is operatively connected with and exends upwardly from the drive  32 , and a horizontal or substantially horizontal partitioning section  38  extending from the upper end portion  36  of the section  34 . The section  34  is or can be parallel to the upright aligning member  10 , and the section  38  can extend through one of the aforementioned openings or windows in the aligning member  10 .  
         [0048]    It will be appreciated that the superimposed or overlapping sheets  4  on the upper reach of the conveyor  2  and in the stack  30  actually contact each other, i.e., the illustrated relationships of these sheets are chosen solely for the convenience of reading the FIGS. 1, 2, etc. The sheets  4  on the upper reach or stretch of the conveyor  2  form an imbricated pattern and are caused to continuously advance toward the surface  20  of the stop  8  (see the arrow  2 D).  
         [0049]    The partitioning member  28  also constitutes a substantially L-shaped body having an upright section or component  40  which is at least substantially parallel to the aligning member  10 . The horizontal lower section or component  48  of the partitioning member  28  (i.e., the section which is remotest from the conveyor  2 ) includes a hollow projection  42  which, in FIG. 1, extends at right angles to the component  40  toward the aligning member  10  and includes a rounded tip which can be introduced through one of the aforementioned openings in the aligning member  10  (see FIG. 3) to separate a fully assembled stack  30  from the next-following (growing) stack  76  (see FIGS.  3  to  7 ).  
         [0050]    The horizontal upper panel  44  of the projection  42  of the component  48  is provided with openings or ports  46  which establish communication between an internal compartment or chamber  50  of the component  48  and the surrounding atmosphere. When the compartment  50  is connected with a suitable suction generating device (e.g., with the pump  24 A or with an analogous pump), the upper panel  44  can attract a sheet  4  which overlies the panel  44  (see, for example, FIG. 3). The compartment  50  is further connectable with a source  50 A of compressed air so that the openings  46  can discharge streamlets or jets of air; such streamlets flow through the panel  44  and urge the adjacent lowermost sheet  4  of the growing second stack  76  away from the projection  42  when the latter is received in the space between the stop  8  and the aligning member  10 .  
         [0051]    A second compartment or chamber  52  of the partitioning member  28  is adjacent an array of openings or ports  56  in the upright section  40  of the partitioning member. The chamber  52  can communicate with the intake of a suction generating device (such as the pump  24   a  or a discrete pump, not shown, e.g., the pump which can draw air from the compartment  50 ). The openings  56  enable the member  28  to attract objects to the exposed side or surface of the section  40 .  
         [0052]    The apparatus  1  further comprises a mobile distancing member including a horizontal core or table  58  which is movable along an at least substantially horizontal path in and counter to the direction indicated by an arrow  62 , i.e., in parallelism with the upper reach of the conveyor  2 . The character  60  denotes an envelope or cover of textile material or the like which forms part of the distancing member and, in the illustrated embodiment of the apparatus  1 , overlies the upper side and the underside of the table  58 . The cover  60  is movable relative to the table  58  in the direction indicated by an arrow  64 , preferably at a speed which matches the speed of the table  58  in the direction of the arrow  62 . Thus, the table  52  and the cover  60  can move in directions and at speeds such that the position of a point X on the cover portion overlying the upper side of the table  58  remains unchanged in space, i.e., the distance from the point X to the plane of the upright aligning member  10  remains unchanged.  
         [0053]    [0053]FIG. 1 shows the parts of the apparatus  1  in positions they assume during normal operation of the apparatus. A control unit  2 A controls the operation of the conveyor  2  so that the upper reach of this conveyor delivers a succession of discrete partially overlapping sheets  4  from a source of sheets in a direction indicated by the arrow  2 D, i.e., toward and into the stacking station  6  so that the front edge of each sheet impinges upon and descends along the upright surface  20  of stop  8 . The control unit  2 A includes or is associated with an adjustable sheet sensor or counter  2 B which can be of any suitable design and generates a signal whenever the conveyor  2  completes the delivery of a predetermined or preselected number of sheets  4 , namely the desired number of sheets to be contained in a fully grown stack (see the stack  30  in FIG. 3, i.e., the sheets  4  between the pallet  12  and the section  38  of the finger  26 ). The conveyor  2  can receive a series of discrete sheets  4  from a station wherein one or more knives of a severing unit repeatedly cuts or cut across a running web of paper, metallic foil or the like.  
         [0054]    The drive  32  (or a discrete second drive, not shown) begins to move the finger  26  downwardly (note the arrow  66  in FIG. 2) as soon as the section  38  has penetrated between the fully grown stack  30  and the lowermost sheet  4  of the next-following (growing) stack  76 . The downward movement of the finger  26  and of its section  38  takes place at a speed less than the speed of downward movement of the pallet  12  with the fully grown stack  30 ; this is indicated by the lengths of the arrows  14  and  66  shown in FIG. 2. The positions of all other mobile parts shown in FIG. 2 remain the same as in FIG. 1.  
         [0055]    [0055]FIG. 3 shows that, due to a downward movement of the pallet  12  with the fully grown stack  30  thereon which is faster than the downward movement of the separating finger  26 , the section  38  establishes a wedge-like clearance or gap  68  which narrows (due to flexibility of the sheets  4 ) in a direction from the aligning member  10  toward the stop  8 . The next step involves the introduction of the stack partitioning member  28  into the left-hand portion of the gap  68  as soon as the height of such left-hand portion of the gap suffices to accept the projection  42  (see FIGS. 3 and 4).  
         [0056]    The upright component  40  of the partitioning member  28  comes close to or actually abuts the adjacent trailing ends  70  of the lowermost sheets  4  forming part of the growing (second) stack  76  while the underside  72  of the lowermost sheet of the stack  76  abuts the upper side of the panel  44  (i.e., overlies the openings  46 ).  
         [0057]    Introduction of the partitioning member  28  into the gap  68  takes place simultaneously with or immediately precedes withdrawal of the horizontal section  38  of the separating finger  26  from the corresponding opening of the aligning member  10  (i.e., from the left hand-side of the pileup of sheets  2  then accommodated at the upright stacking station  6 ). This is shown in FIG. 4. The properly inserted partitioning member  28  begins to descend with the pallet  12  (see the arrow  74  in FIG. 4) as soon as the projection  42  completes its forward movement into the gap  68 . Such downward movement in the direction of arrow  74  takes place simultaneously with downward movement of the stack separating finger  26  in the direction of arrow  66 . The positions of all other members of the apparatus  1  (with the exception of of the continuously descending elevator  12 A and of the continuously driven conveyor  2 ) remain unchanged.  
         [0058]    The chambers  50  and  52  are connected to the suction pump  24 A or to a discrete suction generating device while the separating finger  26  is being withdrawn, or immediately upon completed withdrawal of the finger  26 , from the gap  68 . Thus, the openings  56  draw atmospheric air through the upright section  40  of the member  28  and into the chamber  52 ; such air is drawn from eventual accumulations of air in the spaces (if any) between neighboring sheets  4  of the growing stack  76  while the exposed surface  54  abuts the foraminous (such as perforated or otherwise apertured) portion of the upright aligning member  10 . Suction in the chamber  50  ensures that the openings  56  can cause the underside  72  of the lowermost sheet  4  of the growing stack  76  to adhere to the upper side of the panel  44  of the projection  42 .  
         [0059]    The suction pump  24 A is activated simultaneously with the reduction of pressure in the chambers  50  and  52 , i.e., the pressure of air in the chamber  24 , in the openings  18  and at the surface  20  of the stop  8  is reduced below atmospheric (see FIG. 5). This ensures that the openings  18  can withdraw pockets of air between the adjacent front edges  78  of the sheets  4  forming part of the growing stack  76  and can pull such front edges against the surface  20 . Still further, suction in the chamber  24  ensures that the front edges  78  of lowermost sheets  4  of the growing stack  76  cannot descend toward and onto the top sheet  4  of the fully grown stack  30 .  
         [0060]    The aforedescribed retention of lowermost sheets  4  of the growing stack  76  at the partitioning member  28  takes place while the separating finger  26  descends (in the direction of the arrow  14 ) with the pallet  12  and the fully grown stack  30  thereon. This results in a downward movement of the separating finger  26  to and beyond the position which is shown in FIG. 5, i.e., below the level of the table  58  (see FIG. 6).  
         [0061]    [0061]FIG. 6 shows that the elevator  12 A lowers the pallet  12  in the direction of the arrow  14  at a speed which exceeds the speed of downward movement of the partitioning member  28  so that the width (actually height) of the clearance or gap  68  increases and reaches a predetermined value (exceeding the height of the distancing member including the table  58  and the cover  60 ) not later than when the gap portion below the level of the partitioning member  28  can readily receive (preferably with at least some clearance) the table  58  and its cover  60 . The table  58  is thereupon introduced into the gap  68  beneath the partitioning member  28  by moving in the direction of arrow  80  in response to actuation of a prime mover  58 A (e.g., a double-acting cylinder having a reciprocable piston or a carriage reciprocable along a suitable track, not shown). The suction chamber  24  and the chambers  50 ,  52  continue to draw air through the respective openings  18 ,  46  and  56 .  
         [0062]    Suction which is established in the chamber  24  ensures that the underside  72  of the lowermost sheet  4  in the growing stack  76  does not descend into contact with the table  58  and more particularly with the cover  60  the upper panel of which is advanced in the direction indicated in FIG. 1 by the arrow  64 , i.e., counter to the direction (see the arrow  80  in FIG. 6) of entry of the table  58  into the gap  68  between the stacks  30  and  76 . However, if the underside  72  of the lowermost sheet  4  of the growing stack  76  happens to come into contact with the envelope  60 , this is compensated for in that the speed of the table  58  in the direction of the arrow  80  matches the speed of movement of the upper panel of the cover  60  in the direction of the arrow  64 ; this ensures that the position of the lowermost sheet  4  of the growing stack  76  (as seen in the direction in or counter to that indicated by the arrow  80 ) remains unchanged. Absence of sliding movement between the underside  72  of the lowermost sheet  4  of the growing stack  76  and the cover  60  is desirable and advantageous because this reduces the likelihood of providing the underside  72  of the lowermost sheet  4  of the stack  76  with lines, grooves, scratches and/or other undesirable formations as a result of contact with the cover  60 .  
         [0063]    In order to further reduce the likelihood of scoring and/or otherwise undesirably affecting the appearance of the underside  72  of the lowermost sheet  4  of the growing stack  76  above the table  58 , it is desirable and advantageous to provide the upper side of the table  58  with ports or analogous openings which discharge streamlets  82  (see FIGS. 6 and 7) of compressed air or another gaseous fluid. Such fluid issues from one or more plenum chambers (not specifically shown in the drawing) and penetrates through the foraminous cover  60  to impinge upon the underside  72 . If the cover  60  is impermeable to gases, the streamlets  82  urge the upper side of the upper panel of the cover against the underside  72 .  
         [0064]    When the table  58  reaches the front end position which is shown in FIG. 7 (or even before such time), it is lowered by its support, together with the partitioning member  28 , at a rate which is required to ensure that the uppermost sheet  4  of the stack  76  between the stop  8  and the aligning member  10  is maintained at the level  16 , i.e., at the desired or required level relative to the upper reach of the conveyor  2 .  
         [0065]    The next step involves the transport of fully grown stack  30  out of the apparatus  1 , e.g., to the right, as viewed in FIG. 7. The stack  76  continues to descend in a manner as described hereinbefore with reference to the stack  30 , and such downward movement is shared by the partitioning member  28  and the table  58 . Lowering of the stack  76  ensures that successive uppermost sheets  4  of this stack are located at the level  16 . A fresh pallet (see the pallet  86  in FIG. 8) is introduced into the stacking station  6  beneath the table  58 , and such introduction is preceded by disconnection of the suction chamber  24  from the suction pump  24 A so that the stop  8  cannot interfere with downward movement of the stack  76 . Furthermore, in the apparatus  1  the table  58  ceases to discharge jets ( 82 ) of compressed air or another gaseous fluid toward the underside of the stack  76  when the fresh pallet  86  assumes the position which is shown in FIG. 8. However, it is equally within the purview of the instant invention to continue with the discharging of jets  82  while the table  58  is being moved from the position of FIG. 8 to that which is shown in FIG. 9, to the left of the separating finger  26  and to a level nearer to that of the conveyor  2 . Thus, the directions of movement of the table  58  are reversed in comparison with the directions of movement from the position shown in FIG. 1 to that which is depicted in FIG. 8. Moreover, the cover  60  is also moved relative to the table  58 , namely in a direction to avoid any sliding movements between the lowermost sheet of the stack  76  and the upper panel of the cover.  
         [0066]    [0066]FIG. 9 shows the fresh pallet  86  in the position previously occupied by the table  58 . Thus, the distance between this pallet and the underside  72  of the lowermost sheet  4  of the stack  76  is minimal. The pallet  86  is advanced to the position of FIG. 9 simultaneously with retraction of the partitioning member  28  from the gap  68  in the direction of the arrow  88 ; this results in deposition of the stack  76  on the pallet  86  (see FIG. 10). In order to facilitate retraction of the member  28  from the underside  72  of the lowermost sheet  4  of the stack  76 , the source  50 A (FIG. 1) is caused to admit compressed air or another gas into the chamber  50  so that the openings  46  discharge jets  90  (see FIG. 9) of compressed gas. Such mode of extracting the member  28  from the gap  68  reduces the likelihood of any, or of any appreciable, frictional engagement between the member  28  and the underside  72 . This is desirable because the likelihood of scoring and/or otherwise adversely affecting the appearance of the underside  72  is reduced to a minimum.  
         [0067]    The partitioning member  28  is thereupon lifted to its starting position (see the arrow  92  in FIG. 10) and the finger  26  is lifted in the direction of arrow  94 . This completes the placing of the apparatus  1  into the condition shown in FIG. 1 except that the pallet  12  is replaced with the pallet  86 . The arrow  96  denotes in FIG. 10 the direction of downward movement of the fresh pallet  86  with the elevator  12   a . From then on, the stack  76  is treated in the same way as described above with reference to the stack  30  and as shown in FIGS.  1  to  7 , i.e., the stack  76  is caused to grow into a full-sized stack, a third stack is caused to grow at a level above but spaced apart from the stack  76 , the fully grown stack  76  is removed from the apparatus, a third pallet is deposited on the elevator  12 A, and so forth.  
         [0068]    An advantage of the improved apparatus  1  is that it is no longer necessary to clamp a fully grown stack between two jaws in a manner as disclosed in the aforediscussed published German patent application Serial No. 36 16 470 A1 of Martini et al. Instead, the lowermost sheet  4  of the growing stack  76  is attracted to the partitioning member  28  by suction. In other words, it is not necessary to compress the stack  30 , the stack  76  and the next-following stacks. The operation of the improved apparatus  1  is simpler than that of the apparatus proposed in the German patent application of Martini et al. because it is not necessary to employ two clamping jaws and/or the mechanisms which move the clamping jaws toward and away from and with each other.  
         [0069]    The suction chambers  24  and  52  enable the stop  8  and the section  40  of the partitioning member  28  to attract the adjacent sheets  4  because the recently developed web severing apparatus (i.e., the apparatus which can be utilized to subdivide a running web into a continuous series of sheets  4 ) are capable of furnishing sheets with front and rear edge faces  4   a ,  4   b  (FIG. 1) of such smoothness that, when the sheets are piled up on each other, the corresponding front and rear sides of the stacks  30 ,  76 , etc. are sufficiently smooth to enable streamlets of air flowing into the openings  18  and  56  to adequately attract the respective stacks  30 ,  76 , etc. to the surfaces  20  and  54  as long as the respective suction chambers  24 ,  52  are connected to the suction pump  24 A and/or to other suction generating means.  
         [0070]    The feature that the gap  68  and the next-following gaps can be formed by causing the finger  26  to descend at a speed less than the speed of downward movement of the preceding stack (compare the FIGS. 2 and 3) renders it possible to form gaps of optimum width (height) in a simple but efficient and time-saving manner.  
         [0071]    As can be seen in FIGS. 3 and 4, the section  38  of the finger  26  can be withdrawn from the gap  68  as soon as the height of this gap (at the left-hand side of the station  6 ) is sufficient to ensure unimpeded introduction of the projection  42  of the partitioning member  28 , i.e., such withdrawal of the section  38  can take place simultaneously with or immediately following the introduction of projection  42  into the gap  68 . However, it is equally within the purview of the invention to combine the finger  26  with the partitioning member  28  so that the finger can move in an aperture of the partitioning member.  
         [0072]    The means for drawing air from the chamber  52  and/or  56  can include a blower having a suction side connected or connectable to the sections  40 ,  48  of the partitioning member  28 , a pump (such as the pump  24 A) or any other suitable suction generating means in association with valves which are controlled by the unit  2 A to attract the edge faces and/or the undersides ( 72 ) of certain sheets during predetermined stages of operation of the apparatus  1 .  
         [0073]    The provision of the means ( 46 ,  56 ) for attracting the undersides ( 72 ) of selected sheets  4  to the panel  44  of the section  48  of the partitioning member  28  constitutes a desirable feature of the present invention. The utilization of the source  50 A of compressed air in conjunction with the chamber  50  and openings  46  renders it possible to simplify the apparatus  1  because the means ( 50 ,  50 A,  56 ) for urging sheets  4  away from the partitioning member  28  includes parts ( 50 ,  56 ) of the means ( 50 ,  52 ,  46 ,  56 ) for attracting sheets to the member  28 .  
         [0074]    The suction chamber  52  can be utilized in addition to or in lieu of the suction chamber  50 . It is often preferred to provide the partitioning member  28  with both chambers, i.e., to enable the member  28  to temporarily attract the underside ( 72 ) of the lowermost sheet  4  of a growing stack as well as the rear side of such stack, to attract only the underside of the lowermost sheet or to attract only the rear side of the stack.  
         [0075]    A substantially L-shaped partitioning member  28  (with mutually inclined sections  40 ,  48 ) is ideally suited to simultaneously attract the underside as well as the rear side of a growing stack (such as the stack  76  in FIG. 5) in order to ensure that the stack is temporarily held against movements relative to the member  28 . The reason is that the stack can be maintained in large-area contact with the member  28 .  
         [0076]    The cover  60  can constitute a sheet or strip or endless band of flexible material which may but need not be permeable to gases.  
         [0077]    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 accumulating successive stacks of superimposed sheets on pallets or the like and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the appended claims.