WO1998001823A1

WO1998001823A1 - Leaf-turning device for turning over and counting a pile of sheets and an index-cutting machine provided with such a device

Info

Publication number: WO1998001823A1
Application number: PCT/SE1997/001185
Authority: WO
Inventors: Kalle Eino Aksberg; Sture Stenson Lindvall
Original assignee: Arno Maskin Ab
Priority date: 1996-07-04
Filing date: 1997-07-01
Publication date: 1998-01-15
Also published as: EP0978096A1; AU3564297A; SE506945C2; SE9602653L; PL330998A1; SE9602653D0; JP2000514578A

Abstract

A leaf-turning device for turning over and counting a pile (12) of sheets, comprising a leaf-turning nozzle (20, 30) for holding a sheet by suction and displacing it away from the rest of the pile. A lifting rod (24) is movable relative to the pile (12) and the leaf-turning nozzle (20, 30) to be inserted between a sheet held by the nozzle by suction and the rest of the pile and to pull said sheet away from the nozzle and to displace said sheet to an intermediary storage position. The lifting rod is arranged to move in a circular path within which said leaf-turning nozzle (20, 30) is positioned and which extends between the leaf-turning nozzle (20, 30) and the pile (12). A blow nozzle (21) is provided for directing a jet of air (22) against the edge of the sheet lifted off by the leaf-turning nozzle, in order to release any additional entrained sheets, before the lifting rod (24) pulls away the counted sheet from the nozzle. The invention likewise concerns an index-cutting machine provided with such a leaf-turning device.

Description

LEAF-TURNING DEVICE FOR TURNING OVER AND COUNTING A PILE OF SHEETS AND AN INDEX-CUTTING MACHINE PROVIDED WITH SUCH A DEVICE

The present invention relates to a leaf-turning device as well as to an index-cutting machine provided with such a device.

Leaf-turning devices exist for many different pur- poses, for instance to count the number of notes or documents in a bundle of notes or documents, or to count predetermined number of sheets or leaves in a book or catalogue block in connection with the shaping of thumb- index along one edge of the block. Such thumb-indexes are produced by a machine known as an index-cutting machine (or thumb-index cutter) forming indentations along a thumb-index side of an insert comprising one or several sheets. The insert is sometimes referred to as a block, particularly if it is to be fitted with or is provided with covers to form a book, a catalogue or the like.

Prior-art leaf-turning devices for these purposes either operate entirely mechanically or on the basis of vacuum technology.

As one example of mechanically operating leaf-turn- ing devices may be mentioned the one disclosed in the

International Publication W093/25427. In accordance with this prior-art device the stitched or bound block of sheets is bent about a displaceable support, making the free edges of the bent sheets assume an offset position relative to one another, whereby the sheets retained in position by a finger means may be dropped one by one onto a sheet-block support while at the same time the number of released sheets are counted. When the desired number of sheets have been released and have formed a group of sheets on top of a sheet support the required indentations are produced by removing sheet material in a cutting or punching operation performed along the sheet edge. This procedure is then repeated a requisite number of times in order to form the required number of thumb- index indentations, depending upon the intended number of groups of sheets or leaves in the book or catalogue block. Devices of this prior-art type function very well after setting of the machine for a particular paper grade and thickness but require much from the operators in the way of setting accuracy and skill.

One example of a leaf-turning and sheet-counting unit based on vacuum technology is the unit described in GB-A-1, 55, 108. This unit comprises a counting head moving downwards along a corner of a pile of sheets while flipping through the sheets therein and comprising a suction rail which includes a suction nozzle and which is pivotable about a horizontal axis so as to be able to grip the corner of the uppermost sheet of the pile by means of one of its sides, bending said sheet upwards in order to give room for insertion of a lifting rod, which is orbiting around the suction rail to bend the gripped sheet about the suction rail, lifting it to the upper face thereof, against which upper face the sheet is allowed to rest while the required number of sheets are being counted and which face is used as a temporary sheet support to the sheets already counted. When the required number of sheets has been counted a separation edge is placed underneath the suction rail in order to interrupt the leaf-turning operation.

In a commercial version of this leaf-turning device the counting of the number of sheets is performed from the bottom upwards along one corner of the bundle or block of sheets. However, the principle is the same, i.e. the lifting rod performs an orbiting motion in a very narrow or flat path around the suction rail, bending each individual sheet about the suction rail in order to carry the counted sheets past said rail. The number of counted sheets is determined by counting the number of orbits performed by the lifting rod around the suction rail during the counting process. Also these mechanisms based on vacuum technology require accurate setting in order to ensure that the number of counted sheets indicated by the mechanisms coincides with the actual number of flipped-through sheets. Consequently, it is important that the suction force of the suction rail be adjusted to the current paper or sheet grade, ensuring that only one sheet at a time will be swept around the suction rail while the lifting rod is orbiting around the suction rail. As long as the paper or sheet grade is similar in a bundle of sheets the difficulties in achieving correct sheet counting results are not insurmountable but should the bundle of sheets comprise sheets of different grades and porosity errors may easily arise. The reason therefor is that the suction force must be adjusted to the bending stiffness of those sheets that are thicker or stiffer, which may cause the suction rail to grip, by suction force, more than one sheet of a thinner or less stiff grade, with ensuing erroneous leaf-turning results. Another disadvantage inherent in these prior-art units based on vacuum technology is that sometimes they may damage the turned-over sheets owing to the careless treatment to which they are exposed because of the forced bending or sweeping of the sheet corners, held fast by suction, in a narrow path around the suction rail, which may cause permanent deformation of the sheet corners.

One object of the present invention thus is provide a leaf-turning device and also an index-cutting machine equipped with such a device, ensuring safer leaf-turning and counting results by making use of suction in order to achieve the leaf turning. Another object of the invention is to reduce the risks for permanent damage to turned- over sheets. Yet another object of the invention is to allow the sheets to be turned by means of a leaf-turning device that is of more simple construction but yet more reliable. Another object of the invention is to eliminate one or several other disadvantages found in prior-art devices of similar type.

These and other objects of the invention are achieved by means of a leaf-turning device and an index-cutting machine as defined in claims 1 and 9, respectively. The dependent claims define particularly preferred embodiments of the invention.

The invention is based on the technology known from GB-A-1, 55, 108 according to which the sheet in question is lifted off the rest of the pile of sheets while making use of a vacuum pressure, whereupon it is carried past the suction nozzle to an intermediate storage station. Contrary to the case in the prior-art leaf-turning device based on vacuum technology the leaf-turning device in accordance with the present invention is provided with a blow nozzle adapted to direct a separating jet of air against the edge of the sheet removed from the pile by the leaf-turning nozzle in order to release any additional entrained sheets before the separating rod pulls the counted sheet away from the leaf-turning nozzle. If, in accordance with a particularly preferred embodiment of the invention, use is made of an air-deflecting surface or the like in order to guide the jet of air along the edge of the block of sheets in a direction away from the leaf-turning nozzle, while the leaf-turning nozzle is positioned closely adjacent the block of sheets, release will be initiated of the sheets closest to the one held by suction by the leaf-turning nozzle, already before the sheet held by suction by the leaf-turning nozzle is lift- ed off the block of sheets as a result of the movement of the leaf-turning nozzle away from the block of sheets.

Should it be considered necessary to provide sufficient space to accommodate the moving separating rod, it is possible in accordance with such an embodiment of the invention to use a separate sheet holder instead of the opposite side of the suction nozzle, for the purpose of establishing the intermediate storage of already turned- over sheets.

A less complicated drive mechanism thus is achieved in accordance with the invention, since the lifting rod may be displaced or moved in a different manner relative to the leaf-turning nozzle and may engage the held sheet at a considerable distance away from the suction nozzle, thus being able to gently bend the sheet and thus carry it to the intended intermediate storage position. Owing to this arrangement the risks for permanent damage to the turned-over sheets are eliminated and in addition, the lifting rod could, should so be desired, be displaced in a simple circular path around the leaf-turning nozzle instead of moving in the elongate orbital path employed in the above-mentioned prior-art vacuum-based technology. In summary, the invention resides in a leaf-turning device for turning over and counting a pile of sheets. The leaf-turning device includes a leaf-turning nozzle to hold a sheet by suction and to convey it away from the rest of the pile. A lifting rod is movable relative to the pile and to the leaf-turning nozzle for insertion of said rod between a sheet held by the nozzle by suction and the rest of the pile and for pulling said sheet away from the nozzle and convey the sheet to an intermediate storage position. The lifting rod is arranged to move along a circular path within which the leaf-turning nozzle is positioned and which extends between the leaf- turning nozzle and the pile. A blow nozzle is provided to direct a jet of air against the edge of the sheet having been lifted off the pile by the leaf-turning nozzle, in order to release any additionally entrained sheets, before the lifting rod pulls the counted sheet away from the nozzle. The invention likewise concerns an index-cutting machine fitted with such a leaf-turning device. The invention will be described in more detail in the following with reference to the accompanying drawings illustrating two examples of devices configured in accordance with the invention and in which:

Fig. 1 is a schematic view of an index-cutting machine including a leaf-turning device in accordance with the invention,

Figs 2-5 show a sequence of steps of a leaf-turning procedure, making use of the leaf-turning device in accordance with Fig. 1, Fig. 6 is a schematic view of another embodiment of a leaf-turning device in accordance with the present invention, and Figs 7-10 illustrate a sequence of steps of a leaf-turning procedure, employing the leaf-turning device in accordance with Fig. 6. Fig. 1 is a schematic view of an index-cutting machine which in a manner known per se comprises a cutting unit having a stationary lower cutting edge 10 and a movable upper cutting edge 11. The spine of a block of sheets 12 is clamped in a holder 13 located at a distance from the cutting unit for adjustment of the depth of the thumb-indexes. In a manner not illustrated in detail the holder may be displaced on the one hand towards and away from the cutting unit and on the other at right angles thereto (vertical direction as seen in Fig. 1). The former movement is used for setting the spacing between the holder and the cutting unit in conformity with the current depth of the thumb-indexes whereas the latter movement it used to direct the lowermost sheet of a counted bundle of sheets to a position level with the stationary cutting edge of the cutting unit, ensuring that the lowermost sheet of the bundle of sheets, after completion of the leaf-turning operation, is kept flat and at an angle of 90° to the spine of the block of sheets and also ensuring that a correctly configured recess may be formed during the cutting operation. The former movement is performed during the setting of the index-cutting device in conformity with the current thumb-index depth whereas the latter movement is employed in the course of the activity of the index-cutting device in order to lift the entire block of sheets step by step and in dependence on the current thickness of the sheets and the current number of sheets in the bundle of turned- over sheets. If the sheets have a thickness of e.g. 0.1 mm and the current bundle of turned-over sheets is to contain 14 sheets, the latter movement is made use of to move the block of sheets 1.4 mm upwards in order to position the spine end of the lowermost sheet level with the upper face of the lower cutting edge.

The holder 13 likewise comprises a cylindrical support rod 14 and a sheet-block support 15 supporting the depending sheets of the block 12 of sheets, maintaining them in a bent or arcuate configuration. The support rod and the sheet block support are displaceable relative to the sheet holder 13 and to the cutting unit 10, 11, and they are fed stepwise in the direction towards the latter as the leaf-turning process progresses, such that the first sheet not yet turned-over assumes a correct position relative to a leaf-turning nozzle to be described further on. Also in this case the stepwise feeding is effected in dependence on the sheet thickness of the individual sheets of the block. The mechanisms used to effect these various setting movements are already known and for that reason are not shown or described in any detail.

The leaf-turning device also comprises a holder-up rod 16 which is kept pressed against the not yet turned- over sheets during the entire leaf-turning process in order to keep the sheets stretched while at the same time this rod also acts as a means of support to the already turned-over sheets. The holder-up rod is mounted on a pivotable arm and may pivot from a lower position 16 to a cutting position 16' and from there to a lifting position 16" wherein the cut sheets have been moved to a ready position for already cut sheets or leaves. The already cut sheets are retained in this position by a retainer bar 17. The latter is displaceable lengthwise, whereby it may be pulled out of the path of movement of the holder- up rod 16, allowing the cut sheets free passage during the movement of the holder-up rod 16 from position 16' to position 16". When the holder-up rod 16 has reached position 16", the bar 17 is pushed to the position illustrated in Fig. 1 in order to retain the cut sheets when the holder-up rod 16 is pivoted downwards to its bearing-down position (lower position in Fig. 1).

The very leaf-turning device in accordance with the embodiment of Figs 1-5 comprises a suction head 20. The suction head serves as a leaf-turning nozzle and is pivotable about an axis extending in parallel with the depending sheets, and in addition it is displaceable towards and away from the depending sheets, as will be described in more detail with reference to Figs 2-5. A blow-off nozzle 21 is located somewhat below the suction head, said blow-off nozzle being directed obliquely towards the suction nozzle and the depending sheets in order to direct a sheet-separating flow of air 22 against said sheets. To control the flow of air a guiding surface in the shape of a concave recess 23 is formed in the lower edge of the suction nozzle. The leaf-turning device likewise comprises a lifting rod 24 which may be moved in a round or circular path about a fixed geometrical axis 25. As will be described further on, the lifting rod is inserted between an already turned-over sheet and the rest of the depending sheets, lifting the turned-over sheet upwards and past the suction nozzle 20, up to the upper face of a retainer rod 26, in which position the sheets are stored until the correct number of sheets with respect to the current lot of sheets has been counted. In accordance with this embodiment it is not absolutely necessary to use the retainer rod 26 as a support for intermediate storage of the already turned-over sheets before the latter are transported to the position wherein the thumb-index recesses are cut. This is due to the fact that the flow of air issuing from the blow nozzle 21 will produce an excess pressure in the space between the depending sheets of the block of sheets and the sheets retained by the suction nozzle and because the air blown into that space will maintain the already turned-over sheets at some distance exteriorly of the nozzle 20 (to the right thereof as seen in Fig. 1) . The lifting rod 24 thus is adapted to move in a closed path within which the leaf-turning nozzle 20 as well as the retainer rod 26, if used, are positioned and which extends between the leaf-turning nozzle and the pile. When the correct number of sheets has been counted the holder-up rod 16 is moved to its position 16' to support the lot of sheets while the thumb-index recesses are being cut or punched. In order to carry the current lot of sheets upwards, to the cutting device, a lifting arm 27 is used, said arm assuming its lower position of rest (illustrated in continuous lines in Fig. 1) during the leaf-turning operation but being moved during the lifting operation along a path between on the one hand the retainer rod 26 and the position 16' of the holder-up rod, and on the other, the depending sheets of the block of sheets 12 and up to its upper position 27 ' illustrated by dash and dot lines in Fig. 1.

In the following the various steps of the leaf-turning and punching processes will be described in closer detail with reference to Figs 2-5. In Fig. 2, the leaf- turning-device is shown in its position of departure for turning over the first sheet. The leaf-turning nozzle 20 is positioned closely adjacent the first sheet of the block 12 of sheets, holding it by suction. At the same time the sheet-separating flow of air 22 is directed against the concave recess 23 to be directed obliquely downwards to the left (as seen in Fig. 1), along the free peripheral edges of the sheets in the block 12 of sheets. The following step involves pivoting the leaf-turning nozzle 20 counterclockwise about a horizontal axis to the position illustrated in Fig. 3. As a result, the sheet held by suction is pivoted outwards, away from the remainder of the sheets in the block 12 of sheets. When the leaf-turning nozzle is being pivoted, the recess 23 will be moved away from the air jet 22. As a result, the air jet will blow directly onto the edge of the sheet being entrained by the leaf-turning nozzle 20 and consequently it will blow off from that sheet any additional sheets that may have been entrained by the leaf-turning nozzle. At the same time an excess pressure is generated in the space between the outwards folded sheet and the remainder of the sheets in the block 12 of sheets. In the meantime, the lifting rod has travelled over a part of its circular path, from its position of departure illustrated in Fig. 2 to the position illustrated in Fig. 3. During the continued leaf-turning process the nozzle 20, having been swung outwards, is moved more or less straight to the right, away from the block 12 of sheets, to provide space for insertion of the lifting rod 24 into the space between the outwards-lifted sheet and the depending sheets in the block 12 of sheets. This phase is illustrated in Fig. 4.

As the lifting rod 24 continues along its path of movement, passing upwards past and above the nozzle 20 at a distance therefrom, it will cause the suction-held sheet to be pulled off alongside the suction nozzle 21 and be carried arcuately above the retainer rod 26. The air jet 22 will facilitate this movement, in addition to which it will tend to blow the sheet entrained by the lifting rod 24 outwards, past the retainer rod 26. As the lifting rod subsequently completes its circular movement and returns to the position of departure illustrated in Figs 1 and 2, the entrained sheet will rest against the retainer rod and assume the position illustrated in Fig. 1.

The various part steps of the leaf-turning procedure are repeated until the intended number of sheets have been turned over and been carried upwards to their intermediate storage position on top of the retainer rod 26. Because the holder-up rod 16 abuts against and is forced downwards to bear upon the block 12 of sheets, the discrete turned-over sheets will take on a distinct curved configuration.

As mentioned above, the support rod 14 and the sheet-block support 5 are moved stepwise to the right as seen in Figs 1-5 during the leaf-turning procedure, whereby the discrete sheets next to be turned over will be positioned within the operative area of the suction nozzle 20 when the latter assumes its position illustrated in Figs 1 and 2.

When the required number of sheets have been turned over, the drive mechanisms, not illustrated, that actuate the holder-up rod 16 and the lifting arm 27, are activated. The holder-up rod 16 is carried to its position 16' and the lifting arm 27 is moved successively upwards to its upper position 27' in order to lift the turned-over lot of sheets above the holder-up rod 16' . The lifting arm 27 is then again pulled downwards to its lower position and in doing so will deposit the turned-over lot of sheets on top of the holder-up rod 16' and the fixed cutting edge 10. The lot of sheets is now ready to be punched or cut by the movable cutting edge 11 as the latter is carried downwards, past the fixed cutting edge 10.

After completion of the cutting or punching of the thumb-index recesses, the holder-up arm is pivoted further upwards from position 16' to the upper position 16" in order to carry the finished sheets to a ready position above the retainer bar 17. Temporarily, this bar is retracted from its position in the path of movement of the holder-up arm 16 and of the finished sheets carried by said arm, allowing the sheets to pass upwards, above the bar 17. Before the arm 16 is again pivoted downwards from position 16" to the lowermost position 16, the bar 17 is reintroduced into the path of the finished sheets in order to retain the latter in the ready position.

As soon as the various components have returned to their positions illustrated in Figs 1 and 2, the turning- over of the next lot of sheets to be punched or provided with thumb-index recesses is begun.

The leaf-turning operation may be performed at a very high speed, the turning-over of a block containing 150 sheets in which 15 thumb-index punches are to be made can be performed in about 30 s, inclusive of the automa- tic change of blocks of sheets.

The embodiment of the invention illustrated in Figs 6-10, which is the currently most preferred embodiment since it allows the desired rapid leaf-turning and thumb-indexing cutting operations to be performed by means of a mechanism that is even more simple and contains even fewer movable parts. For the sake of simplicity identical numeral references have been used for such components of the embodiment of Figs 6-10 that have exact counterparts in the embodiment of Figs 1-5. For this rea- son, these components will not be described in any detail .

The two embodiments are distinguished from one another through the design of the nozzle retracting the current sheet from the depending block of sheets. In accordance with Figs 1-5 direct-contact suction was used because the nozzle 20 sucks in air through its nozzle aperture. Instead, the sought-after effect is obtained in accordance with Figs 6-10 in that a narrow elongate jet 31 of air is ejected through a slit-shaped nozzle opening in a nozzle 30. The air jet 31 is directed essentially in parallel with the depending sheets in the block 12 of sheets and in a direction towards the holder-up rod 16 in order to entrain the outermost sheet by suction, as will be described in the following with reference to Figs 7-10. Otherwise the embodiments in accordance with Figs 6-10 and Figs 1-5 operate in the same way. Fig. 7 illustrates the leaf-turning device at the stage of turning over the very first sheet. The air jet 31 brushes along the outermost sheet and will pull it away from the depending sheets of the block of sheets. The pulling-out effect will be considerably more effi- cient, when the nozzle 30, as illustrated in the Figures, is designed with a convex arcuate surface 32 which is turned towards the block 12 of sheets such that the effective "nozzle opening" which forms between said surface 32 and the depending sheets of the block 12 of sheets presents its narrowest through-section area at or adjacent the slit-shaped nozzle opening through which the air jet 31 leaves the nozzle 30. The widening gap between the surface 32 and the sheets in the block 12 of sheets thus will create an underpressure above the narrowest section area, exactly in the same way as a venturi pipe. The separating air jet 22 exiting through the nozzle 21 is to have a lower flow rate than the air jet 31 exiting from the nozzle 30 in order not to disturb the extraction of the outermost sheet in the block 12 of sheets to be turned over.

As appears from Fig. 8 the outermost sheet will be sucked outwards, away from the block of sheets, the separating air jet 22 then being directed precisely against the marginal area of said sheet. Should one or several additional sheets be entrained outwards in the suction operation towards the nozzle 30, the air jet 22 will separate any such entrained sheets from the outermost sheet and blow them back against the rest of the sheets in the block 12 of sheets. Like in the embodiment in accordance with Figs 1-5 the lifting rod 24 moves in a continuous circular movement about the axis 25. When the sheet held by suction by the nozzle 30 reaches the nozzle surface 32 the lifting rod 24 has already entered the space between the nozzle 30 and the block 12 of sheets. At the same time, the separating air of the air jet 22 has begun to displace the suction-held sheet upwards and to the right as seen in Fig. 9, which facilitates the mechanical lifting movement of the lifting rod in accordance with Fig. 10. When the lifting arm 24 has released the turned-over sheet such that the latter is supported by the retainer rod 26, the turning over of the subsequent sheet will have begun, as is illustrated in Fig. 8.

This successive leaf-turning, sheet by sheet, of the block 12 of sheets progresses thereafter until a predetermined number of sheets have been turned over. The num- ber of turned-over sheets is counted also in this case by supervision of the number of revolutions performed by the lifting rod 24 about its axis 25.

Contrary to the case in the embodiment of Figs 1-5 the nozzle 30 may be maintained stationary during the entire leaf-turning process. Lifting-out of the sheet to be turned over is not effected by moving the nozzle 20 relative to the block 12 of sheets but by sucking the outermost sheet intended to be turned over outwards in response to the venturi effect and the ejector pumping effect achieved by the powerful air jet 31. Mechanically therefore, this embodiment is more convenient to design than the one illustrated in Figs 1-5.

The rest of the procedure, involving handling of turned-over sheets in the lot of sheets, lifting of the lot of sheets to the cutting position and further to the ready position, is performed in the same manner as in accordance with the embodiment of Figs 1-5 and therefore will not be described here.

From what has been said above appears that by uti- using the present invention the sheets may be turned over in a more gentle way as they are bent into a smooth arcuate configuration having a comparatively large radius of curvature instead of being swept in a sharp bend about a relatively thin suction-nozzle blade, as taught by the prior-art, vacuum leaf-turning technology represented by GB-A-1, 455, 108 and the commercial equivalences thereof. Likewise, it is apparent that the mechanism necessary to achieve the required movements of the leaf-turning device and the thumb-index cutting machine is a great deal more simple and consequently less expensive to manufacture and easier to service. According to the illustrated embodiments of a leaf- turning device of the invention the discrete sheets of a block of sheets are turned over from a depending block of sheets. However, within the scope of the invention the leaf-turning operation could also be performed in other positions, for instance by lifting the sheets by suction from an essentially horizontally positioned block of sheets. In addition, the sheets or leaves forming the block of sheets or pile of sheets need not be interconnected along the spine of the block of sheets, i.e. they need not be inserts for catalogues or books, but the discrete sheets or leaves may be piled loosely one on top of the other and be retained along one edge while the leaf- turning operation is effected along the opposite edge or from a corner area of said latter edge.

Claims

1. A leaf-turning device for turning over and count- ing a pile (12) of sheets, comprising a holder (13) for gripping the pile (12) along one edge thereof, a leaf-turning nozzle (20, 30) disposed adjacent the opposite edge of the pile or adjacent a corner portion thereof for holding a sheet, by suction, and for displacing said sheet away from the rest of the pile, a retainer (26) for retaining the sheets thus removed from the pile, a separating rod (24) which is movable relative to the pile (12) and to the nozzle (20, 30) to be inserted between a sheet held by suction by the nozzle and the rest of the pile and to pull said sheet away from the nozzle and to displace said sheet to a position, wherein it rests on the retainer (26) , and a counting mechanism counting the number of completed lifting and displacement motions performed during the turning-over of the sheets of the pile of sheets, c h a r a c t e r i s e d in that the leaf-turning device comprises a blow nozzle (21) for directing a jet of air (22) against the edge of the sheet lifted off the pile by said leaf-turning device, in order to release any further entrained sheets before the separating rod (24) pulls the counted sheet away from the leaf-turning nozzle.

2. A leaf-turning device as claimed in claim 1, c h a r a c t e r i s e d in that the abutment (26) is formed by a retainer rod (26) disposed at a distance away from the leaf-turning nozzle (20, 30) .

3. A leaf-turning device as claimed in claim 1 or 2, c h a r a c t e r i s e d in that the separating rod (24) is a lifting rod (24) arranged to move in a circular path within which are positioned the leaf-turning nozzle (20, 30) and, as the case may be, the retainer rod (26) and which extends between the leaf-turning nozzle (20, 30) and the pile (12) so as to cause the lifting rod (24) to engage a sheet removed from the pile (12) by said leaf- turning nozzle (20, 30), pulling said sheet away from the leaf-turning nozzle and carrying it to an intermediate storage positioned beyond the leaf-turning nozzle (20, 30) .

4. A leaf-turning device as claimed in claim 1, 2 or 3, c h a r a c t e r i s e d in that the leaf-turning nozzle (20) is a suction nozzle (20), said nozzle being carried against the pile of sheets to hold the outermost sheet by suction and including a drive mechanism for pivoting the nozzle about an axis which extends essentially in parallel with the sheet and for moving the nozzle in an essentially translatory movement away from the pile of sheets in order to allow insertion of the separation rod (24) between the turned-over sheet and the remainder of the pile of sheets.

5. A leaf-turning device as claimed in any one of claims 1-4, c h a r a c t e r i s e d in that the leaf- turning nozzle (20) configured as a suction nozzle is formed on its side facing the blow nozzle (21) with an air-deflecting surface (23) for directing the jet of air

(22) away from the blow nozzle along the side edge of the pile of sheets, when the leaf-turning nozzle abuts against the pile of sheets, said air-deflecting surface

(23) being displaced outwards away from the path of said air jet during pivotment and displacement motions of said leaf-turning nozzle.

6. A leaf-turning device as claimed in claim 2, c h a r a c t e r i s e d in that the leaf-turning nozzle (30) is configured as a blow nozzle (30) having a slitlike outlet opening directed essentially alongside the sheets in the pile (12) of sheets in order to lift off, by a suction effect similar to the venturi effect, the outermost sheet in pile of sheets and to make room for the separation rod (24) .

7. A leaf-turning device as claimed in claim 6, c h a r a c t e r i s e d in that the face (32) of the leaf-turning nozzle (30) that is turned towards the pile of sheets has a convex shape in order to strengthen the venturi effect.

8. A leaf-turning device as claimed in claim 6 or 7, c h a r a c t e r i s e d in that the blow nozzle (30) is stationary.

9. An index-cutting machine designed to form a thumb-index along a thumb-index side of an insert (12) composed of a plurality of sheets, comprising a cutting unit (10, 11) and a leaf-turning device in accordance with any one of the preceding claims, said leaf-turning device and said cutting unit having a holder-up rod (16) arranged to hold the sheets in the pile (12) of sheets during the leaf-turning operation and, upon completion of the leaf-turning operation, to be moved out of the path of movement of a lifting arm (27) arranged to lift the turned-over sheets that are retained by a retainer rod (26) to a cutting position, wherein the turned-over sheets are kept directed in alignment with the cutting unit and from which position the cut sheets are moved to a ready position (at 17).