Patent Description:
Creasing machines are used for generating one or more creases in a sheet from which blanks are cut which are folded. Each of the creases forms kind of a "hinge" which allows the later formed blanks to be folded at a well defined place.

The creasing machine can be formed as a device or system which is either a standalone unit or is integrated into a larger machine or system such as a printing machine or a finishing machine.

The sheets can be made from cardboard, carton or a foil, and they can be provided to the creasing machine separately or in a continuous manner as part of a web.

The creases are formed by locally applying a pressure onto the sheet. To this end, creasing knives are known which are pressed onto the surface of the sheet so as to generate the crease. It is also known to provide local projections on the creasing tool, for example by etching away those portions of the creasing tool which shall not project, or by locally applying a plastic material in a liquid condition, which is then cured. For example <CIT> discloses a method of creasing sheets by using a creasing tool cooperating with a counter element involving a creasing plate blank is provided projections obtained by plastic deformation, the creasing plate being mounted to said creasing tool and cooperating with said counter element.

The creasing tool can either be generally flat and be moved back and forth in a direction which is generally perpendicular with respect to the plane in which the sheet extends, or it can be generally cylindrical and be rotated so as to engage at the sheet when it is being transferred through the creasing area.

The problem with all creasing machines is that they can hardly be quickly adapted to a specific pattern of creases to be applied to a sheet. This has become more of a problem since digital printing allows changing very quickly from one printing job to a different one.

Assuming that the creasing tool is to be manufactured by means of an etching process, it may take several hours until a new creasing tool is available. Assuming that the creasing projections are formed by applying a plastic material to a carrier, the manufacturing times might be shorter, depending on the time which is necessary for curing the plastic material. However, the lifetime of such a creasing tool is significantly shorter than the lifetime of a creasing tool comprising an etched steel plate. In any case, the step of adapting the creasing machine to a new creasing job is the bottleneck when the creasing machine is used in connection with a digital printing machine.

The object of the invention is to provide a creasing method which can be quickly changed from one creasing pattern to another creasing pattern.

In order to achieve this object, the invention provides a method of creasing sheets by using a creasing tool cooperating with a counter element, as defined in claim <NUM>.

The invention is based on the concept of using a metal creasing plate in which the creasing projection is formed by a large number of punching strokes, the individual punching strokes generating the creasing projection. This allows achieving two advantages. First, the creasing plate has a long lifetime as there is very little wear at the creasing projections, simply because they are made from metal. The strain hardening which inevitably occurs during punching contributes to the wear resistance of the creasing plate. Second, individual creasing plates can be manufactured quickly and with very little effort by for example a turret punching machine or a coil punching machine.

Preferably, the material of the creasing plate blank is deformed by means of a punching module. It is thus not necessary to install a separate punching machine. Rather, a dedicated (smaller) punching module can be integrated into the machine so as to form a self contained creasing machine which does not require any external machinery when it comes to manufacturing the creasing plates.

The punching module is preferably a turret punching machine or a coil punching machine as these types of machine allow manufacturing the creasing plates in a very flexible yet quick manner.

According to an embodiment, the punching module has a punch and a die, the die having an outer contour which extends, adjacent the open end of the recess, at an angle of between <NUM>° and <NUM>°, approximately <NUM>° or less than <NUM>° with respect to the longitudinal direction of the recess, the die being rotated so as to align the outer contour with an already generated creasing projection. The advantage of this geometry is that merging creasing projections can be generated which extend at an angle of <NUM>° with respect to each other.

In order to be able to quickly exchange one creasing plate against a different one, the creasing plate can is clamped to the cylindrical surface of a creasing cylinder of the creasing tool.

When a creasing cylinder is being used, it cooperates with a counter cylinder. The counter cylinder can be provided with an elastic layer against which the sheets are pressed and which allows the creasing projections to locally deform the sheets so as to generate the creases.

The counter cylinder can alternatively be provided with a layer made from a shape memory material. This layer can be clamped to the counter cylinder in order to facilitate the installation, and can be "erased", owing to the shape memory qualities of the material from which it is made, once a creasing job is finished.

According to a preferred embodiment, the distance between the axis of rotation of the creasing cylinder and the counter cylinder is adjusted with respect to the plane in which the sheet is transported, before a creasing job is started. This allows changing the creasing direction (from above the sheets to from below the sheets, and vice versa) so as to be able to crease carton and corrugated cardboard on one and the same machine. It is sufficient to exchange which of the cylinders is provided with the creasing plate and which is provided with the layer acting as counter element to the creasing plate, and to change the distance between the axis of rotation of the two cylinders and the plane in which the sheets are being transported through the creasing area between the cylinders.

Preferably, the creasing cylinder and the counter cylinder are driven with different speeds of rotation. This ensures that the peripheral speed of both cylinders at the radius at which they interact with the sheets is identical, despite the fact that there are different effective radii.

According to an embodiment, a driving fillet is generated on the creasing plate, the driving fillet extending around the majority of the circumference of the creasing cylinder. Providing a driving fillet avoids the problem that usually, the driving engagement between the creasing cylinder and the sheets depends from the presence of creasing projections in the gap between the two cylinders, the creasing projection entraining the sheets. If however no creasing projection is present in the gap at a certain point in time, then the sheet usually has no contact to the creasing cylinder as the outer surface of the creasing cylinder is at a distance from the surface of the sheets; it is only the creasing projections which engage at the sheets. The driving fillet ensures that a driving engagement between the creasing cylinder and the sheet is always maintained (possibly apart from a short dead zone which is used for clamping the creasing plate to the creasing cylinder). Thus, even if no creasing projection is currently engaging at the sheet, the sheets are positively driven by means of the driving fillet.

The driving fillet can be obtained by locally deforming the creasing plate in a manner similar to the creasing projections. As an alternative, the driving fillet can be obtained by applying a strip of epoxy material onto the creasing plate, which is then cured.

The method preferably comprises the further step of detecting the arrival of a sheet to be creased at the gap between the creasing tool and the counter element and controlling the rotation of the creasing tool and the counter element in dependence upon said detection.

The invention will now be described with reference to the enclosed drawings. In the drawings,.

In <FIG>, a creasing machine is schematically shown. It comprises a transportation system <NUM> for advancing sheets <NUM> through a creasing area <NUM> where folding creases can be applied to the sheets <NUM>.

Additional processing stations <NUM>, <NUM> may be provided as part of the creasing machine or associated therewith. Processing stations <NUM>, <NUM> can be used for cutting, folding, gluing or otherwise processing the sheets <NUM> or articles produced therewith.

Sheets <NUM> can be made from cardboard, carton or foil, and they can later be processed so as to cut blanks from the sheets to form a package, a box, a wrapping, an envelope or a similar product.

Sheets <NUM> can be supplied to creasing area <NUM> either separately as shown in the Figure, or in the form of a continuous web guided through creasing area <NUM>.

It is also possible to integrate into creasing area <NUM> a cutting system which allows separating the individual blanks from the sheet.

In creasing area <NUM>, a creasing tool and a counter element cooperate so as to apply at least one folding crease to sheet <NUM>. To this end, the creasing tool carries a creasing plate, the creasing plate being provided with creasing projections. The geometry and arrangement of the creasing projections on the creasing plate corresponds to the folding creases to be applied to the sheet.

A first example of the creasing tool and the counter element used in creasing area <NUM> is shown in <FIG>.

The creasing tool is here in the form of a plunger <NUM> which can be advanced towards and pressed against a counter element <NUM>. At plunger <NUM>, a creasing plate <NUM> is mounted which is provided with at least one creasing projection <NUM>. Only a single creasing projection <NUM> is shown here for increased clarity.

On the side facing plunger <NUM>, counter element <NUM> is provided with an elastic layer <NUM> which preferably is formed from rubber or an elastomer.

The sheets <NUM> to be provided with a folding crease are advanced with transportation system <NUM> so as to be positioned between plunger <NUM> and counter element <NUM>. Plunger <NUM> is then pressed against elastic layer <NUM> whereby creasing projection <NUM> creates a folding crease <NUM> by locally deforming sheet <NUM>.

A second embodiment of the creasing tool and the counter element is shown in <FIG>. Here, the creasing tool is provided in the form of a creasing cylinder <NUM>, and the counter element is in the form of a counter cylinder <NUM>. Accordingly, creasing plate <NUM> is curved, and elastic layer <NUM> is cylindrical.

The folding creases <NUM> are generated by advancing sheet <NUM> through the gap between creasing cylinder <NUM> and counter cylinder <NUM>.

The interaction between creasing plate <NUM> and sheet <NUM> is shown in more detail in <FIG>.

Creasing projections <NUM> are formed at creasing plate <NUM> by repeatedly and locally deforming the material of creasing plate <NUM> so as to generate the creasing projections <NUM> in the desired pattern. In order to allow for the desired plastic deformation, creasing plate <NUM> is formed from steel, in particular from carbon steel or stainless steel. It preferably has a thickness in the order of <NUM> to <NUM>.

For generating the creasing projections <NUM>, a punching module <NUM> is provided, in particular a turret punching machine or a coil punching machine. Punching machines of these types are generally known. They however are preferably slightly adapted for being used in combination with the creasing machine. In particular, punching module <NUM> may not be as versatile and powerful as a conventional punching machine as it only has to perform a very limited number of different operations (namely generating generally straight creasing projections) in a rather thin material.

Punching module <NUM> is schematically shown in <FIG> with a punch <NUM> used for plastically deforming a creasing plate blank <NUM>'.

Further, punching module <NUM> comprises a turret <NUM> in which a plurality of different punches <NUM> is stored.

<FIG> schematically shows how punching module <NUM> generates a creasing projection <NUM> by repeatedly plastically deforming creasing plate blank <NUM>'. With full lines, punch <NUM> is shown which cooperates with a die <NUM> positioned on the opposite side of creasing plate blank <NUM>'. With dashed lines, the position of punch <NUM> during the previous punching stroke is shown, and dotted lines indicate the position of punch <NUM> during the again proceeding punching stroke.

Each stroke generates a small, plastically deformed area at the creasing plate blank <NUM>', with the entirety of the plastically deformed areas forming the creasing projection(s) <NUM>.

<FIG> show different embodiments of the punch arranged on a carrier <NUM>.

In <FIG>, a punch <NUM> with a comparatively short projecting portion <NUM> is shown. The length of the projecting portion can be in the order of one centimeter.

At its ends which are opposite each other when viewed along the longitudinal direction of the projecting portion <NUM>, comparatively small radii are provided. They can be in the order of <NUM> to <NUM> millimeters.

In <FIG>, a punch <NUM> is shown in which the projection portion <NUM> is approximately three times the length of the projecting portion <NUM> of the punch <NUM> shown in <FIG>. It can be seen that the radii at the opposite ends of the projecting portion are comparatively large.

In <FIG>, a punch <NUM> is shown which has different radii at the opposite ends of the projecting portion <NUM>. There is a small radius R<NUM> which is in the order of <NUM> to <NUM> millimeters only, and there is a large radius R<NUM> which can be in the order of <NUM> to <NUM> millimeters.

The height H (please see also <FIG>) with which the projecting portion <NUM> projects over the forward end face of punch <NUM>, is in the order to <NUM> to <NUM>.

<FIG> show an embodiment of die <NUM> adapted for cooperating with punch <NUM> and mounted on a carrier <NUM>.

Die <NUM> has a support surface <NUM> at which creasing plate blank <NUM>' may abut during the punching operation. Within support surface <NUM>, a recess <NUM> is provided. Recess <NUM> is sized so as to receive the plastically deformed material of creasing plate blank <NUM>' forming the creasing projection <NUM>.

As can be seen in <FIG>, recess <NUM> is open at its opposite ends.

It can further be seen in <FIG> that the outer contour of die <NUM> adjacent one of the open ends of recess <NUM> extends inclined with respect to the longitudinal direction of recess <NUM>. In particular, the outer contour at each side of recess <NUM> extends at an angle of <NUM>° with respect to the longitudinal direction of recess <NUM>.

At the opposite end of recess <NUM>, the outer contour of die <NUM> extends perpendicularly with respect to the longitudinal direction of recess <NUM>.

An elastic ejector <NUM> is arranged at die <NUM>. Ejector <NUM> is formed as a plate from rubber or an elastomer and snugly surrounds die <NUM> so that it stays at the position shown in <FIG> without any additional measures.

In <FIG>, a different embodiment of die <NUM> is shown. Here, die <NUM> has the inclined contour at both open ends of recess <NUM> (please see the portions to which arrows P point).

In <FIG>, a conventional die <NUM> is shown which has a circular support surface <NUM>.

In <FIG>, a schematic cross section through the punch <NUM> cooperating with die <NUM> is shown.

The creasing plate blank <NUM>' is held, during the process of locally plastically deforming it so as to create the creasing projections <NUM>, between die <NUM> and the carrier <NUM>. Carrier <NUM> is here spring loaded towards die <NUM> so as to act in the manner of a clamp.

This avoids tension in the creasing plate blank <NUM>' which could result in unwanted deformations.

In <FIG>, it is schematically shown how adjacent creasing projections <NUM> can be formed by means of the punch cooperating with die <NUM>. For better clarity, the punch and the creasing plate are not shown in <FIG>. Rather, only creasing projections <NUM> formed at creasing plate <NUM> are shown.

The creasing projection <NUM> extending towards the left in <FIG> is a projection which was previously formed. The creasing projection <NUM> extending through the recess in die <NUM> is the creasing projection currently formed together with punch <NUM>. It can be seen that the "new" creasing projection <NUM> can be formed to a point where it is immediately adjacent the "old" creasing projection <NUM>.

The result of the immediately adjacent creasing projections <NUM> is visible in <FIG> where folding creases <NUM> are shown which are arranged at a <NUM>° angle with respect to each other and which almost merge into each other. Since very little uncreased material remains in the corner between the folding creases <NUM>, a very precise fold can be achieved in this area.

In <FIG>, it is shown how three creasing projections <NUM> can be formed at a creasing plate. Due to the particular contour at one of the open ends of recess <NUM>, the three creasing projections <NUM> can almost merge into each other at an intersection point. It can be seen in <FIG> where such creasing projections <NUM> can be used for forming folding creases <NUM> at a sheet <NUM>.

These creasing projections are aimed to fold a composite flap of a crash lock bottom box or of a four corner or six corner tray.

Punching module <NUM> is capable of producing different creasing plates <NUM> by appropriately deforming a creasing plate blank <NUM>' at the required locations. It is in particular possible for the creasing machine, in particular for a schematically shown control <NUM> of the creasing machine, to determine, upon receipt of data for a new creasing job, whether a new creasing plate <NUM> is to be manufactured or whether an "old" creasing plate used in a previous creasing job can be used. Depending on the determination, control <NUM> either initiates that punching module <NUM> manufactures a new creasing plate <NUM>, or that the "old" creasing plate <NUM> is retrieved from an inventory <NUM> where the previously manufactured creasing plates <NUM> are being stored.

The creasing plate <NUM> (either newly manufactured or retrieved from inventory <NUM>) is taken over by handling system <NUM> and is then mounted at the creasing tool.

If the creasing tool is a punch, the plate is mounted in a flat shape. If the creasing tool is a creasing cylinder, creasing plate <NUM> can be either bent and clamped to creasing cylinder <NUM>, or a circumferentially closed creasing sleeve can be formed which can then be mounted to creasing cylinder <NUM>.

As is explained above, a punch having larger radii at opposite sides (to be precise: having larger radii at opposite sides of its projecting portion <NUM>) is used for obtaining creasing projections <NUM> which have a smooth transition between the material deformed with each stroke of the punch. <FIG> shows creasing projections <NUM> which terminate at a larger distance from each other. The creasing projections <NUM> very smoothly merge into the creasing plate <NUM>.

<FIG> shows two creasing projections <NUM> which terminate in a very small distance from each other so as to almost merge into each other. These creasing projections <NUM> are obtained by using a punch <NUM> which has at least at its "forward" end (referring to the direction in which the creasing plate blank <NUM>' is displaced during consecutive strokes) a small radius. The small radius allows for a comparatively steep rise of the creasing projection <NUM> from the creasing plate <NUM> so that a small distance between adjacent ends of the creasing projections <NUM> is possible.

It can be seen that the ends of the creasing projections which are at the opposite ends, terminate with a larger radius.

<FIG> show cross sections through creasing projections <NUM> which have been proven to be very effective for creasing carton.

In <FIG>, the creasing plate has a thickness in the range of <NUM> while the height h of the creasing projection is in the range of <NUM> to <NUM>.

Depending from the particular carton to be creased, the radius r at the apex of the creasing projection <NUM> can be in the range of <NUM> to <NUM>. In other words, the apex matches an inscribed circle with a diameter of 2r.

Preferred values for the height h are in the region of <NUM>, while preferred radii can be <NUM> and <NUM>.

In <FIG>, a creasing projection <NUM> for creasing corrugated cardboard is shown. It can be seen that a much wider creasing projection is used as compared to the profiles shown in <FIG>. In particular, the angle α is more than <NUM>°. According to a preferred embodiment, this angle can be in the range of <NUM> to <NUM>°, in particular <NUM>°.

The wider conical shape of the profile of creasing projection <NUM> is effective to compress the carton on each side of the crease so as to create the space which is necessary for folding the corrugated cardboard (because of its increased thickness), thereby reducing the tension which is generated when the carton is folded.

Here again, a typical height of the creasing projection <NUM> is in the region of <NUM>. As the radius r at the apex of the profile, a value in the order of <NUM> to <NUM> is suitable, in particular <NUM>.

As a radius R at the base of creasing projection <NUM>, a value in the order of <NUM> has been proven to be beneficial.

An inscribed circle here again can have a diameter of <NUM>.

It is important to note that the creasing projections <NUM> on one and the same creasing plate <NUM> can have different heights, depending from the particular requirements.

<FIG> show an advantageous aspect of the creasing tool.

When changing from creasing cardboard to creasing corrugated carton, it is necessary to change the crease direction. This can very easily be done by changing the function of the two cylinders <NUM>, <NUM>.

In <FIG>, the upper cylinder acts as the counter cylinder <NUM> while the lower cylinder is the creasing cylinder <NUM>. Accordingly, the elastic layer <NUM> is mounted to the upper cylinder while creasing plate <NUM> is mounted to the lower cylinder.

In the configuration shown in <FIG>, this arrangement is reversed. The elastic layer <NUM> is mounted to the lower cylinder while creasing plate <NUM> is mounted to the upper cylinder. Thus, the upper cylinder acts as creasing cylinder <NUM> while the lower cylinder acts as counter cylinder <NUM>.

It is however the same set of cylinders which is being used. The function of the cylinder is simply determined by the "tool" mounted to it (either creasing plate <NUM> or elastic layer <NUM>). Accordingly, both cylinders are provided with identical clamping mechanisms (here very briefly indicated with reference numeral <NUM>), and the cylinders have the same diameter.

The functional outer radius of both cylinders depends from the tool mounted to it. In particular, the functional outer radius of the cylinder provided with the elastic layer <NUM> is larger than the functional radius of the cylinder provided with creasing plate <NUM>. Accordingly, the plane in which sheet <NUM> is advanced through the creasing area between the cylinders has to be adjusted depending from the particular configuration. The respective Δ is indicated between <FIG>.

The vertical adjustment of the plane in which sheets <NUM> are provided can either be obtained by vertically adjusting the feeding device which advances the sheets, or by vertically adjusting the two cylinders <NUM>, <NUM> with respect to the feeding plane.

Another consequence from the functional radius of the two cylinders being different is that the speed of rotation of the cylinders is slightly different as the tangential speed at the point of engagement at the sheets <NUM> has to be the same. Further, it has to match the speed with which the sheets <NUM> are advanced through the creasing tool.

In order to allow for an individual control of the speeds of rotation, each cylinder is provided with a servo motor <NUM> which is controlled by means of a machine control <NUM>. Machine control <NUM> is also provided with a signal relating to the position of the clamping devices <NUM> as they form a dead zone where no creasing can be made.

Machine control <NUM> is furthermore provided with a signal relating to the position of the sheets <NUM> advanced through the creasing tool. This signal can be obtained via a sensor <NUM> which for example detects the leading edge of the sheets <NUM> upstream of the creasing tool.

Based on the effective radii RE, the speed V with which the sheets <NUM> are advanced through the creasing tool, and the signal from sensor <NUM>, machine control <NUM> suitably controls the servo motors <NUM> so as to achieve the proper speed of rotation U for each of the cylinders and also the correct position of the dead zone with respect to the individual sheets.

For manufacturing creasing plate <NUM>, it has to be kept in mind that the creasing plate blanks <NUM>' are deformed when being in a flat shape while the creasing plates are mounted, when installed on a creasing cylinder <NUM>, in a curved shape. This results in the creasing projections <NUM> having, when the creasing plate is mounted to the creasing cylinder <NUM>, a distance from each other which is larger than in the flat configuration of the creasing plate.

As can be seen in <FIG> and <FIG>, the creasing projections <NUM> are pressed into the carton to be creased by a certain distance (for example <NUM>) which however is less than the total height of the creasing projection. It is however preferred that the outer surface of creasing plate <NUM> does not touch the upper surface of sheets <NUM>. Accordingly, a gap exists between the outer surface of creasing plate <NUM> and the upper surface of sheet <NUM>.

<FIG> shows in an example the straight real length L between two creases <NUM>, measured in parallel with the feeding direction of sheet <NUM>. The same curved real length L can be measured between the apex of the corresponding creasing projections <NUM> on the functional, effective radius RE. It can be seen that in a developed, flat condition of creasing plate <NUM>, because of the difference between the development radius RD and the functional, effective radius RE, the developed length LD is less than the real length L. Accordingly, two creasing projections <NUM> have to be formed on the creasing plate <NUM> in a distance, parallel to the feeding direction, which is less than the actual distance which the respective creases shall have on sheet <NUM>.

In <FIG> and <FIG>, another aspect of the creasing tool is shown.

Typically, sheet <NUM> is driven between the creasing cylinder <NUM> and the counter cylinder <NUM> by the contact of the creasing projections <NUM> with the sheet and also because of the contact of the sheet with the counter cylinder. However, there are creasing configurations where at a certain point in time, no creasing projection <NUM> engages at sheet <NUM>. Because of the gap G explained with reference to <FIG> and <FIG>, no proper driving force would be exerted onto sheet <NUM> in these points in time.

To ensure that sheet <NUM> is always positively driven irrespective of the particular position of creasing projections <NUM>, a driving fillet <NUM> is provided which extends in a circular direction along the entire creasing plate <NUM>. Driving fillet <NUM> can be a plastically deformed portion of creasing plate <NUM> in the same manner as the creasing projections <NUM>.

It is however also possible to create driving fillet <NUM> in a different manner. As an example, an epoxy fillet could be added to the creasing plate in a separate manufacturing operation. Such driving fillet can be seen in <FIG>.

Driving fillet <NUM> does not have to project over the surface of creasing plate <NUM> in a manner which creates a distinct crease in sheet <NUM>. The height can be chosen mainly in view of the intended driving force which shall be generated.

<FIG> show the clamping mechanism <NUM> in more detail.

The clamping mechanism <NUM> is effective to anchor both ends of either creasing plate <NUM> or elastic layer <NUM> and force both ends towards each other equally. This ensures that the respective sleeve is correctly located around the cylinder. Further, this avoids problems with air pockets being trapped under the sleeve. Such air pockets could result in damage to the creasing plate <NUM> or the elastic layer <NUM> when the respective sleeve is put under pressure in operation.

<FIG> show an additional aspect of the creasing machine.

In this embodiment, a sleeve of a shape memory material <NUM> is used on counter cylinder <NUM> instead of elastic layer <NUM>. Shape memory material layer <NUM> is plastically deformed by means of creasing plate <NUM>.

In <FIG>, creasing plate <NUM> has been mounted to creasing cylinder <NUM> while layer <NUM> having in a starting condition with a flat surface is mounted to counter cylinder <NUM>.

For shaping layer <NUM>, the two cylinders <NUM>, <NUM> are advanced towards each other so that creasing projections <NUM> on creasing plate <NUM> penetrate into layer <NUM> (please see <FIG>).

After increasing the distance between cylinders <NUM>, <NUM> (and after curing, if necessary), layer <NUM> has the shape of a counter die to creasing plate <NUM> (please see <FIG>).

Subsequently, creasing cylinder <NUM> with creasing plate <NUM> and counter cylinder <NUM> with layer <NUM> can be used for creasing sheets <NUM> (please see <FIG>).

After a certain creasing job has been finished, layer <NUM> is restored to its original condition. To this end, layer <NUM> can be heated (schematically indicated with reference numeral H in <FIG>) so that the depressions in layer <NUM> are "erased".

When layer <NUM> has been restored to its original flat shape (please see <FIG>), the creasing machine is ready for the next creasing job which starts by creating a new counter die by deforming layer <NUM> with the new creasing plate <NUM>.

<FIG> shows the creasing cylinder <NUM> in more detail.

The clamping mechanism <NUM> has clamping pins <NUM> which are moveable between a clamping position (shown in <FIG>) and a release position (shown in <FIG>).

In the release position, the clamping pins <NUM> are spread apart as compared with the clamping position. Looking at <FIG>, the distance between the clamping pins <NUM> in the clamping position is less than in the release position. In other words, a creasing plate <NUM> having holes into which the clamping pins <NUM> engage, is pulled to the outer circumference of the creasing cylinder when the clamping pins are in their clamping position.

The clamping pins <NUM> are mounted to sliding elements <NUM> which are arranged in a groove <NUM> formed in the creasing cylinder <NUM>. The sliding elements <NUM> are biased by means of schematically shown springs <NUM> towards the center of the groove <NUM> and thus towards each other (and into the clamping position).

A release mechanism is provided for moving the clamping pins <NUM> from the clamping position into the release position. The release mechanism is here formed as a cam mechanism.

The cam mechanism has a plurality of cams <NUM> which are mounted non-rotatably on a shaft <NUM>. The shaft is mounted rotatably in groove <NUM>. Cams <NUM> are symmetrical with respect to the center of shaft <NUM>. Thus, there are two apexes spaced by <NUM>°.

Shaft <NUM> is provided with a bore for receiving an actuating tool <NUM> which can be a simple rod. The actuating tool <NUM> allows rotating the shaft and thus the cams <NUM> from the rest position shown in <FIG> to the spreading position shown in <FIG>.

In the rest position, the cams <NUM> do not exert notable forces on the sliding elements <NUM> so that they are urged by springs <NUM> towards each other into the clamping position.

In the spreading position, the cams urge the sliding elements <NUM> apart into the release position, against the force of the springs <NUM>.

The amount of rotation of shaft <NUM> for transferring the cams <NUM> from the rest position into the spreading position is approx. It can be seen that in the spreading position, the cams <NUM> are moved "beyond" the dead center position in which the two apexes are arranged horizontally when looking at <FIG>, ensuring that the release mechanism reliably remains in the speading position with the clamping pins <NUM> in the release position.

For mounting a creasing plate, the clamping pins <NUM> are brought into their release position. Then, the creasing plate is mounted at the creasing cylinder <NUM> such that the clamping pins engage into holes provided close to the edges of the creasing plate which are arranged opposite each other. Then, the release mechanism is returned into the rest position such that the clamping pins <NUM>, under the effect of springs <NUM>, pull the creasing plate <NUM> tight against the outer circumference of the creasing cylinder.

The clamping pins <NUM> are in the form of hooks so there is a slight undercut into which the creasing plate engages. This ensures that the creasing plate is mechanically held "under" the clamping pins <NUM> and cannot disengage axially outwardly when being clamped to the ceasing cylinder.

<FIG> show the same clamping mechanism <NUM> which is known from the creasing cylinder.

Claim 1:
A method of creasing sheets (<NUM>) by using a creasing tool (<NUM>, <NUM>, <NUM>) cooperating with a counter element (<NUM>, <NUM>), comprising the following steps:
- a creasing plate blank (<NUM>') is provided with at least one creasing projection (<NUM>) by plastically deforming the material of the blank (<NUM>') so as to form a creasing plate (<NUM>),
- the creasing plate (<NUM>) is mounted to a creasing tool (<NUM>, <NUM>, <NUM>) by clamping the creasing plate (<NUM>) to the cylindrical surface of a creasing cylinder (<NUM>),
- the counter element (<NUM>) comprises a counter cylinder (<NUM>) used for cooperating with the creasing cylinder (<NUM>), wherein
- a layer (<NUM>) made from a shape memory material is clamped to the counter cylinder (<NUM>) and is plastically deformed by means of the creasing plate (<NUM>), by advancing the creasing cylinder (<NUM>) and the counter cylinder (<NUM>) towards each other so that the creasing projection (<NUM>) on creasing plate (<NUM>) penetrates into said layer (<NUM>), then, after increasing the distance between said cylinders (<NUM>, <NUM>),
- sheets (<NUM>) to be provided with at least one crease are advanced through a gap between the creasing tool (<NUM>, <NUM>, <NUM>) and the counter element (<NUM>, <NUM>).