Abstract:
For folding sheet layers the folding blade ( 20 ) forms a comb. The comb gaps ( 27 ) are closed during fold pressing and opened during transfer of the fold to a conveyor ( 21 ). Thus the conveyor ( 21 ) engages the sheet only in the region of the comb gaps and easily withdraws the sheet without pressing it into contact against the folding blade ( 20 ). For controlling the gap variations a fully mechanical cam control ( 30 ) is provided underneath the working plane ( 10 ).

Description:
This application is a continuation of 09/338,127 filed Jun. 22, 1999, now abandoned. 
    
    
     TECHNICAL FIELD AND BACKGROUND OF THE INVENTION 
     The invention relates to an apparatus or method for transporting sheets or plies superimposed and directly interconnected via a transition, termed fold in the following. The sheet layers, such as paper, are then in direct contact by their insides and form an outside by outer mutually remote faces. The insides transit via the concave curved inside of the fold and the outer faces transit via the convex curved outside of the fold. The sheets may be multi-layer on each of the two fold sides and within the fold. Then the insides are formed by the innermost layer and the outsides by the outer-most layer between which further layers are located. Such sheet piles to be folded or already folded are further processed into e.g. exercise books. 
     Reference is made to a transport and folding apparatus known from German patent 25 19 420 as included in the present invention with which even deep piles of sheets may be folded by a simple configuration at high speed without the risk of inherent crushing. 
     When the folded sheet is withdrawn from the inserter or folding blade relatively high friction may occur. The blade ensures, however, a smooth transfer of the sheet directly to a conveyor, e.g. so that it is not pulled apart. Thereby, however, the conveyor&#39;s pressure against the outside of the sheet acts via the inside directly on the blade. Thus withdrawing the blade is empeded and limits the working speed. 
     OBJECTS OF THE INVENTION 
     An object is to provide an apparatus or a method which avoids the disadvantages of known configurations or of the kind as described. Furthermore, it is intended to enable the friction with which the sheet is withdrawn from the inserter to be reduced or the working speed to be increased. 
     SUMMARY OF THE INVENTION 
     According to the invention means are provided by which the sheet is passed on to the conveyor so that the transverse or cross force of the latter acting on the outside is transmitted to the inserter only non-significantly or to a negligible degree. This cross force commonly acts on all sheets by clamping so that the sheets will not be mutually displaced due to the conveying force oriented transverse to the cross force. The sheets are transported solely by the positive friction contact with the outside. Transfer of the friction pressure to the contact between sheet and inserter is significantly reduced or even eliminated. 
     The impact for forcing the sheet into conveying engagement may take place in the region of an opening or discontinuity of the inserter and upstream of the conveyor on the outside. Preferably this opening at the end of the inserter is an open cutout. At this cutout the conveyor engages the outside of the sheet. Thus the conveyor presses the sheets within the opening directly against each other by their insides and not against the inserter. 
     Prior to reaching the conveyor these openings of the inserter may be closed with fillers. Thus the inserter&#39;s end is initially also in contact with the fold&#39;s inside at the corresponding opening zone to be opened thereafter. Thus the fold&#39;s inside or crease is formed continuously and evenly by the inserter. Prior to or while reaching the conveyor the opening&#39;s filler is removed or retracted. Thus the filler remains outside the narrowest zone of the infeed mouth of the conveying gap but may, however, protrude as far as into the flare of this gap. 
     The invention is expedient wherever sheets need to be withdrawn from an inserter or engaging member with reduced friction. It may also be advantageous to configure a member which engages the outside of the sheet with pressure and comotion like the conveyor so that its frontmost portion as viewed in the feed direction exerts the highest pressure. Portions of the pressing face directly adjoining downstream thereof exert a lower pressure, e.g. whilst the pressing face rolls along the outer face of the sheet. Thus the fold is additionally creased or pressed flat by being rolled against the inserter without adjoining portions of the outside exposed to an unnecessarily high pressure. 
     The transport or driving face which engages the outside of the sheet can be movable transverse to the outside of the sheet independent of its conveying motion. If the conveyor is a nipper or gripper its gap is widenable and closeable. Thus the pressure against the sheet&#39;s outside is variable or totally eliminatable. The fold can be introduced in the running direction between the jaws of the conveying nipper while simultaneously laying the jaws against the sheet&#39;s outsides and increasing the clamping force. Simultaneously the driving face of the nipper runs commonly with the sheet or inserter at the same speed and running direction. Thus a very gentle transfer is achieved. Thereby the nipper too, may press the fold flat or maintain it flat-pressed. 
     Although for controlling the motion sequences of the inserter, the transverse displacement of the conveyor, of the pressing faces electronic, hydraulic or pneumatic control means are feasible, mechanical control means are preferred. These may include a cam control. The followers guided by the curve or cam bodies are positively connected via transfer drives to the member to be controlled in each case. The transfer drive may comprise a leverage or push and pull rods or be formed solely by these. 
     By the method of the invention the sheet is transferred by the inserter and/or the pressing member to the conveyor, but the inserter is not exposed to the contact pressure of the conveyor. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Example embodiments of the invention are explained in more detail in the following and illustrated in the drawings in which: 
     FIG. 1 is a simplified perspective illustration of the apparatus, 
     FIG. 2 is a left-hand view of the apparatus of FIG. 1, 
     FIG. 3 is a magnified detail of FIG.  2 . 
    
    
     DETAILED DESCRIPTION 
     With apparatus  1  the method according to the invention is carried out fully automatically. Thereby a layer such as a pile of ten or more sheets of flushly stacked paper is folded over 180° to a fold  3 . The two equally large fold legs are then in contact with each other by the full areas of their insides and transit into each other via the fold&#39;s inside  4 . Thus they form remote outsides  5 . While folding the sheet  2  is moved at right angles to its spreaded plane  10  in direction  6  or  16  relative to a stationary frame  7  and perpendicularly away from a table  8 . To the upper table face the planarly spreaded sheet  2  is fed parallel to plane  10  by conveying means so that the fold zone coincides with a gap  9  traversing table  8 . By the transverse motion this sheet  2  is lifted vertically upwards from the table face  10  in the fold zone so that the fold  3  and the layer legs are symmetrical to and on both sides of folding plane  11  which is perpendicular to plane  10 . The sheet&#39;s length parallel to fold  3  includes multiple units and is multiply larger than the books to be produced. After folding and exit transport the sheet  2  is cross-cut into single books or the like. 
     In lifting from plane  10  the fold  3  reaches a plane  12  in which the outsides  5  are gripped for further transport in direction  6  or  16 . Thereby up to a plane  13  which is spaced from plane  10  at least as far as plane  12  or slightly further, the inside  4  is pressure loaded directly in direction  16 . Further thereby up to a plane  14  which is nearer to plane  10  than to plane  12 ,  13 , the sheet legs are maintained parallel and slightly interspaced. Between planes  12 ,  14  and  13 ,  14  respectively the insides of the sheet legs are pressed against each other directly. Planes  10  and  12  to  14  are parallel. 
     Between planes  12  to  14  and plane  10  the fold  3  or sheet legs are pressed. Thereby in the pressing zone the legs are continuously interspaced up to the inside  4  and over their full length. Pressing toward plane  11  occurs on the fly through plane  15  in direction  6 . Thereby the sheet legs slide under curving on the table face and lift off until they are planar. Pressing is terminated shortly before fold  3  reaches one of parallel planes  12  to  15 . Then the sheet legs are free of pressure contact. Pressing occurs only over a smaller height portion of the sheet legs which portion adjoins fold  3  and whilst the legs are tangential to plane  10 . This also applies for reaching planes  12  to  13 . 
     The conveying engagement with maximum pressure transverse to plane  11  from plane  12  onwards occurs only in partial sections of the length of sheet  2 . These sections are shorter than the length sections inbetween in which the pressure of the conveying engagement is relatively reduced or entirely prevented. In the vicinity of these length sections the insides of the sheet legs are thus not in contact until reaching plane  12  or  13 , but only directly thereafter. Whilst pressing is carried out between and with spacings from both planes  10 ,  14  by an arc motion in direction  18  transverse to planes  10  and  12  to  14 , the creasing pressure of ply  2  may be carried out between planes  12  to  14  by a motion in direction  19  transverse to plane  11 . Direction  19  may be parallel to planes  10  and  12  to  14  or in an arc which relative to plane  11  is steeper than direction  18 . 
     For lifting off the sheet&#39;s fold zone from plane  10  and up to planes  12  to  13  a plate inserter or folding blade  20  is provided in plane  11 . In the initial position blade  20  is totally beneath plane  10  but then moved through gap  9  in direction  16 . Thereby blade  20  is slidingly guided on the lateral bound faces of gap  9  and table  8 . Thereby blade  20  is in contact with inside  4  over the full length by an end edge which is acutedly flanked askew on both sides. Thus blade  20  conveys sheet  2  through press  22  up to plane  14 . Thereafter and up to plane  12  or  13  of conveyor  21  the blade  20  rests only against the cited length sections of inside  4  but not on the partial sections inbetween. For this purpose blade  20  is subdivided into two combs or inserter members  23 ,  24  of equal length. They have equal cross-sections between planes  10  and  12  to  14  and are permanently coplanar. 
     Each sub-member  23 ,  24  consists of juxtaposed fingers or strips of sheet-metal which are interspaced and freely protrude in direction  6 ,  16  up to their pointed ends  25  respective  26 . Both remote side edges of each member  24  are slidingly guided on two opposed side edges of two adjacent members  23 . The mutually equal width of fingers  23  is twice as large or larger than the mutually equal width of each of fingers  24 . Both laterally outermost fingers  23  are narrower than the remaining fingers  23 ,  24 . Up to plane  14  the end edges  26  of all members  24  are in a common line with the likewise straight end edges  25  of all members  23  and directly adjoin edges  25 . Then members  24  terminate the motion in direction  16  whilst members  23  continue to run up to plane  12  or  13  in direction  16 . 
     Thus an opening or shallow U-shaped depression  27  is formed between each two adjacent members  23 . The depression bottom is formed by the accompanying end  26  and the depression flanks are formed by the side edges of these members  23 . The lower ends of members  23  and  24  are exchangeably fastened to a support  28  respective  29  by tensioning screws. Slides  28 ,  29  have the shape of oblong beams oriented parallel to plane  10  and to edge  25 ,  26 . Beams  28 ,  29  have opposed tensioning or clamping faces on which members  23  and members  24  are fixed with interspacings. Accordingly, the other slide  29  or  28  slides on the plate face of each member  23  respective  24  which faces away from the accompanying tension face. Thus members  23 ,  24  are guided between these tension faces with pressure and without motion play while being precisely aligned. Slides  28 ,  29  are located beneath plane  10  or table  8 . Slide  28  is mounted for reciprocation in direction  16  on a linear guide  31  of frame  7 . Slide  29  is mounted for reciprocation in direction  16  on a linear guide  32  of slide  28 . Slides  28 ,  29  are commonly and independently displaceable in and counter direction  16  for achieving the cited positioning control of ends  25 ,  26 . The upper.end of guide  31  supports table  8 . 
     Conveyor  21  has for the infeed of sheet  2  a mouth  33  continuously flared counter direction  6 . Mouth  33  extends between plane  10  and plane  12  or  14 . In plane  12  the narrowest zone of mouth  33  is attained. Mouth  33  is bounded by driving faces  34  running in direction  6  and frictionally engaging the outsides  5  only in the vicinity of the cited partial sections. In direction  6  from plane  12  onwards these driving faces bound a conveying gap  35  for sheet  2 . Gap  35  has constant width but is resiliently widenable. Mouth  33  is flanked up to plane  12  by deflections, such as circular pulleys  36  which are located on both sides of plane  11  and over which an endless conveyor belt  37  permanently rotates. Belts  37  bound mouth  33  and with faces  34  gap  35 . 
     Opposed pulleys  36  are rotationally mounted in suspended arrangement on separate supports  38  which are pivotable on both sides of plane  11  about separate axes  39  in direction  19 . The spacing between stationary axes  39  which are located above the pulley axes is always larger than the spacing between the pulley axes. In each case one gap  33  to  35  is located in the vicinity of an arm  24  or of the accompanying breach  27 . On each side of plane  11  the supports  38  of all pulleys  36  are fastened to the common axis  39  while being longitudinally and rotatably adjustable on rest. Opposed supports  38  or axes  39  are directly but counterwise drivingly interlinked. This drive link  40  may act positively by two toothed wheels of equal size and arranged on axes  39 . These wheels are fixed to shafts  39  and mate directly. Thus the upstream end of conveyor  21  forms a gripper to be opened and closed in direction  19  in the vicinity of gap  33 ,  35 . The closing motion of both gripper jaws  36  has a vector in direction  6 . When opening the faces  34  are at an acute angle. When closed the axes of guide pulleys  36  are located in plane  12 . Above axis  39  the gap  35  is diverted transverse to a further press for pressing the fold back  3  and to a transfer station from which sheets  2  are automatically fed to a cutting station for being dismembered into separate products. 
     Press  22  has on each side of plane  11  a plate or strip-shaped pressing ram  41 . Each ram  41  has an edge face nearest to plane  11  which is a convexly curved pressing face  42 . Face  42  uninterruptedly covers the full working width of apparatus  1  or  20  or  21  or  22  and is, like ram  41 , always spaced from planes  10  and  12  to  14 . The end edges of each ram  41  are movably secured to two supports  43  which are fixed to an axis or shaft  46 . Axes  46  are equally spaced from plane  11  and are located in plane  15  in the middle between planes  10 ,  14 . Each axis  46  is located in the center plane of the accompanying face  42  or of plate  41  and spacedly behind the ram&#39;s length edge which is remote from its face  42 . Relative to its support  43  each ram  41  is linearly shiftable with guides  44  parallel to this center plane and transverse or at right angles to plane  11  or axis  46 . With respect to its supports  43  each ram  41  is spring-loaded by springs  45 , like compression springs, toward plane  11  and is thus movable up to an adjustably variable stop position. 
     As evident from FIG. 3 both rams  41  are commonly movable from the initial position shown in dot-dashed lines and nearest to plane  10  in direction  16  or  18  into the other end position as shown. In the initial position faces  42  are spaced from and located between planes  10 ,  15 . In the other end position faces  42  are spaced from and located between planes  12  to  14  and  15 . The leading end or length edge  47  of each face  42 . circumscribes an arc path  17  about axis  46  when moving between the two positions. The face sections  42  adjoining upstream to edge  47  are permanently set back from this arc path. In the initial position faces  42  thus form an infeed funnel or mouth which is constricted up to edges  47  for receiving fold  3 . This mouth is spaced from and directly adjacent to plane  10 . 
     In the simultaneous motion in direction  18  edges  47  and the adjoining face sections  42  approach plane  11 . Thereby the sheet legs urge faces  42 ,  47  counterdirectionally apart against the force of springs  45  to thus roll fold  3  flat. The highest pressing force is achieved when edges  47  reach plane  15 . Thereafter the pressing force which formerly continuously increased is then continuously diminished. Pressing is carried out continuously over the full working width and against blade  20  or all members  23 ,  24 . In the upper end position faces  42  form both the infeed mouth which is constricted in direction  16  and the outfeed mouth or funnel which widens in direction  16  up to edges  47 . Sheet  2  and faces  42  are out of contact in this end position. 
     The feed of the non-folded sheets  2  over the retracted blade  20  and all described motions as well as the outfeed are synchronized by drive and control means  30  powered by a common motor. Control  30  comprises below table  8  and laterally adjacent to plane  11  a camshaft  48 . Thereabove and farer spaced from plane  11  a control shaft  49  is mounted. On the rotary shaft  48  circumferential cams  50  to  52  and  54  are non-rotatingly mounted. On the other side of plane  11  and level with shafts  48 ,  49  an intermediate shaft  53  is provided for limiting the stroke of members  24  up to plane  14 . Means  20  to  22  are controlled and driven by cams via a rods mechanism or leverage  55 . 
     Levers  56  are non-rotatingly and with interspacings arranged on shaft  49 . Levers  56  protrude freely toward plane  11 . On the end of each lever  56  a rod  57  is pivotably mounted by its bottom end and oriented perpendicular to plane  10 . The upper end of this rod is hinged to the underside of slide  28 . Also a rod is hinged in the same axis as rod  57  on each transfer member  56 . This rod is a knee lever  58 . Its upper end is pivotably hinged to the underside of slide  29  or above. In the extended position, namely during the stroke up to almost plane  14  both knee legs of lever  58  are also perpendicular to plane  10 . The effective length of rod  58  is varied with a control rod  59 , adjoining the rod  58  and oriented away from the plane  11 . 
     Cam plate  50  serves to pivot shaft  49  commonly with transfer elements  56  to  59 ,  69 . For this a follower  60  is guided on cam  50 . A corresponding follower  61  is guided on cam plate  51  to actuate conveyor  21  via intermediate elements  71 ,  65 ,  67 ,  39 ,  38 . A follower  62  is guided on cam plate  52  for actuating press  22  via intermediate elements  72 ,  66 ,  68 ,  46 ,  43 . A follower  64  is guided on cam plate  54  for actuating the slide  29  via the transfer elements  74 ,  75 ,  63 ,  59 ,  58  or for mutually moving slides  28 ,  29  or sub-members  23 ,  24 . The intermediate members comprise an obtuse-angled bent lever  63  arranged on axis  53 . Rod  59  is hinged to the upwards oriented arm of lever  63 . When in the middle between its two end positions the effective axial plane of this upper arm is perpendicular to plane  10 . 
     From levers  56  and from the free ends of corresponding levers  71 ,  72 ,  74  the control motion is transferred to associated apparatus parts via linkage  55  assembled from push and pull rods  57 ,  58 ,  65 ,  66 . These rods are permanently oriented as perpendicular as possible to plane  10  and located between those planes of axes  36 ,  39  or  46  which are parallel to plane  11 . Each of these rods traverses plane  11  between its hinging points. 
     Follower  60  is mounted at the free end of lever  70  which like levers  56  is arranged non-rotatably on shaft  49 . Each of followers  61 ,  62 ,  64  is mounted on an associated lever  71 ,  72 ,  74  which in turn is rotatably mounted on shaft  49 . Thus the accompanying transfer elements are actuatable independently of transfer elements  56 . All levers  70  to  72 ,  74  freely protrude from shaft  49  toward plane  11 . In the associated center position the effective axial plane of each of these levers and of levers  56  is perpendicular to plane  11 . All levers are mutually independently spring-loaded by springs  73  in a downward direction or against the associated cam. 
     A rod  65  is hinged on lever  71  by its lower end and inclined at an acute angle to plane  11 . Rod  65  passes plane  10  and is hinged by its upper end on a lever  67  which points away from plane  11  and is fixed to shaft  39 . Shaft  39  is located on that side of plane  11  which is remote from shafts  48 ,  49 . The effective axial plane of lever  67  is perpendicular to plane  11  when nippers  21  are in center position. Follower  61  lies between the lower hinge point of rod  65  and shaft  49 . To the free end of lever  72  separate rods  66  are hinged by their lower ends. Thus their common hinge axis may be coaxial with the accompanying hinge axes of rods  57 ,  58  while these hinge points are equally radially spaced from axis  49 . Rods  66  diverge upwards at an acute angle, traverse plane  10  and are separately hinged by their upper ends to the opposed ends of levers  68 . 
     Each lever  68  is firmly seated on the accompanying shaft  46  and freely protrudes toward plane  11 . In the cited center position of press  22  the levers  68  are perpendicular to plane  11 . The hinge axis between rod  66  and lever  68  is located below the center plane of face  42  which is parallel to this hinge axis. This hinge axis is located in an axial plane which is common with the accompanying deflection  36  and parallel to plane  11  when this deflection  36  is closest to plane  11  as FIGS. 2 and 3 show. The upper end of a rod  75  is hinged to lever  74  between shaft  49  and follower  64  or above shafts  48 ,  49  and levers  56  and  70  to  72 . The lower end of rod  75  is hinged to the shorter arm of lever  63  with a spacing from shaft  63  which is smaller than the accompanying hinge spacing of rod  59 . This shorter arm protrudes downward and is inclined to plane  11 . Both hinge points of rod  75  are located on both sides of plane  11 . The length of each rod  57 ,  58 ,  59 ,  65 ,  66  and  75  is continuously variable for setting. This also applies to each of the individual levers of toggle joint  58 . Furthermore, the effective axial plane of each of levers  56 ,  70  to  72  and  74  is perpendicular to plane  11  when in its center position. 
     The axis of each of the rotating bodies or linkages  36 ,  38  to  41 ,  43 ,  46 ,  48  to  54  and  56  to  75  is parallel to planes  10  and  11 . The axes of shafts  39 ,  46 ,  48 ,  49 ,  53  are permanently stationary relative to frame  7 . 
     Operation and Method 
     Shaft  48  and the non-rotatably fixed cams  50  to  52 ,  54  rotate as shown in FIGS. 1 and 2 continuously counter-clockwise in direction  76 . Thus slides  28 ,  29  and blade parts  23 ,  24  are reciprocated over an adjustable stroke between their upper and lower end positions at continuously varying speeds. Thereby and below plane  14  the ends  25 ,  26  or upper sides of slides  28 ,  29  are permanently aligned level. Before or whilst thus the ends  25 ,  26  downwardly traverse faces  42  the press  22  is lowered to its initial position which it attains when blade  20  has reached its lower reversing point or shortly after it has commenced its upward motion. At this moment—or shortly before—mouth  33  also starts to open. Lever  58  is extended so that edges  25 ,  26  are in line. Before blade  20  reaches gap  9  the spread-out sheet  2  is fed over gap  9  and immediately seized by edge  25 ,  26 . Thus sheet  2  in forming fold  3  is elevated into the region of faces  42  which still stand in initial position. This region forms in the upper end position (FIG. 3) the transition between the infeed and outfeed funnels. This region is nearer to edge  47  than to the lower end of faces  42 . On attaining this region the faces  42  run synchroneously with fold  3  and roll it against the inclined flanks of ends  25 ,  26 . As of having attained the coplanar center position of rams  41  the rolling pressure of faces  42  is continuously reduced up to their upper end position and until faces  42  fully release from the sheet legs to then being traversed by the aligned flush ends  25 ,  26 . Faces  42  are continuously held in this alignment up to the cited return stroke of blade  20 . 
     Ends  25 ,  26  commonly still ascend toward plane  14 . Shortly before plane  14  is reached members  24  with slide  29  are progressively decelerated relative to unit  23 ,  28  until the differential stroke needed to form gaps  27  is executed and until firstly ends  26  have reached plane  14  and secondly ends  25  have reached plane  13  (FIG.  3 ). On entry of fold  3  into plane  12  and while being supported by ends  25  the pulleys  36  reach on their before started closing motion the closed position for gap  33 ,  35 . Pulleys  36  thus press the insides of the sheet legs directly against each other in each of the at least five or seven gaps. Between these gaps  27 , where in their upper end position  13  the upper ends  25  of members  23  engage between the sheet legs, no such transverse pressing takes place. In this region folded sheet  2  is thicker by blade  20  than in the region of gaps  27 . In their upper end position  14  the upper ends  26  are above those zones of members  36 ,  37  which are nearest to plane  10 . Thereby ends  26  have a spacing from plane  12  which is smaller than the radius of members  36 ,  37 . Shortly before fold  3  attains plane  12  it is seized by the permanently continuously revolving faces  34  and synchroneously driven by members  23  up to attaining plane  13 . Then fold  3  is entirely withdrawn from blade  20  or members  23 ,  24  in direction  6  to then being further conveyed to the back press. 
     Whilst members  23 ,  24  pass through their upper reversing points in directly interconnected motions, the spacing  13  to  14  of ends  25 ,  26  is still maintained over a first section of the downward motion while press  22  remains in the upper end position. 
     Whilst thus blade  20  is lowered with increasing speed, the ends  25 ,  26  in passing through press  22  are brought into alignment by closing gaps  27 . Thereby members  24  move downward slower than members  23 . The relative speed between slides  28 ,  29  is highest at its start and diminishes up to the aligned position. This motion terminates shortly before reaching the lower reversing point. This point is maintained over two-fifths of a full motion cycle or over 140° of a revolution of shaft  48 . Relative thereto nippers  22  remain in upper end position longer. During this time the next sheet  2  is run in one go over stationary gap  9  either parallel or perpendicularly to this gap  9 . Thereby, sheet  2  is aligned until it abuts on a transverse stop. It is not until then that press  22  commences its motion down to the lower end position which it attains on commencement of the new stroke of folder  20 . Nippers  21  remain closed over the majority of each cycle, namely 315° of a cam rotation. Its opening commences or is attained whilst press  22  attains its lower end position and whilst blade  20  commences its upward stroke. Its closure commences or is attained when blade  20  has traversed press  22  or prior to engagement of blade  20  and sheet  2  on nippers  21  or after members  23 ,  24  have commenced their relative motion or when this relative motion is completed in forming gaps  27 . The upward motion of blade  20  is faster in the first stroke section than whilst ends  25 ,  26  traverse press  22  and is again faster thereafter. Similarly, shortening of lever  58  may be quicker at the start than towards the end. Modulation of the motion sequences is evident from the curved shapes shown in FIG.  2 . 
     The control of the relative motion of slide  29  without, although possible, resilient stops results in damping the mass forces. Thus smooth operation with low shock and vibration is assured even at a high running speed. Up to a hundred or more folds or stroke cycles or revolutions of shaft  48  may be implemented per minute. Since many parts are symmetrical to plane  11  or to a center plane which is perpendicular to one of planes  10 ,  11  these parts may be used optionally on both sides of plane  11  to the same degree. This applies e.g. to units  36 ,  38 ,  39 , to units  41  to  45  or to their component parts as identified by separate reference numerals or to rods  66 . The entire control is space-savingly located below table  8 . Thus plane  10  is traversed only by rods  65 ,  66 . 
     Means  77  are provided for preventing apparatus  1  from being overloaded or for interrupting control connections to easier set the apparatus. Means  77  form a releasable drive link or coupling between unit  60 ,  70  and linkage  55  or levers  56 . Lever  70  is rotatably mounted on axis  49 . A slaving driver  78  or catch is pivotably mounted on lever  70  between follower  60  and axis  49 . Pawl  78  drivingly engages a counter member  79  in the sense of the lifting motion of blade  20 . This engagement is positive but automatically releases counter a spring force when a predetermined driving force is exceeded. Thus the drive link between follower  60  and members  23 ,  24  is open-circuited, e.g. should blade  20  become jammed by a pile-up of sheets  2 . Counter member  79  is a lever which is mounted on axis  49  or non-rotatably connected to lever  56 . Lever  79  freely protrudes toward plane  11  and driver  78 . Driver  78  is formed by the shorter downwardly pointing arm of a two-armed lever. The longer upwardly pointing arm is connected to an actuating member of a control  80 . By means of control  80  the release force of means  77  or the cited spring force is continuously variable. When control rod  80  is coaxially connected e.g. to a pneumatic cylinder or piston rod the coupling  77  may be optionally engaged and disengaged therewith. This cylinder drive is fixed or pivotably mounted on a support which is arranged on axis  49  or on the bearing thereof. 
     The cited features, such as properties, effects, configurations etc. may be provided precisely as described, or merely substantially or approximately so and may also greatly deviate therefrom depending on the particular requirements. “Perpendicular” and corresponding terms shall also be understood to include transverse orientations which may deviate from a right angle.