Traditional printing techniques such as letterpress and offset litho deposit a thin film of ink on the surface of a stock material. The ink is absorbed by the stock material leaving an indelible mark. In contrast to traditional printing techniques, the Xerography approach used by modern digital print engines is a dry process in which a powder is deposited on the surface of the media to be printed. The powder is bonded to the surface of the media, which is commonly paper, by for example, a heating process. The control of the deposition of powder on the stock material to form words and pictures is typically performed automatically by a computer system.

Digital printing machines have several advantages over the offset litho machine. For example, the offset litho setup process is long requiring plates to be made by a skilled technician, and the printed stock requires time to dry before it can be finished.

Comparatively, digital printing machines have very short setup times, no ink drying time and require a lower level of skill to operate the digital printing process. The fastest growing area in the print industry is for on demand short runs of high quality full colour printing. This is currently best satisfied by digital printing machines The current finishing equipment available to the digital printing market sector, such as creasing and folding machines have been developed for printed matter produced by traditional printing techniques. This type of equipment is unable to handle digitally printed matter without damaging it. For example, high quality digitally produced print requires the use of specially treated paper or card stock material. This type of paper is of such a quality that it is extremely sensitive to marking when articles scrape the surface and to cracking when folded or creased. Also, the toner on the surface of the paper is a brittle layer with a

very low elastic limit that breaks when it is subjected to the tensile stresses created in the bending process by existing folding machines. When broken the toner loses its adhesion and flakes off.

In order to fold printed media cleanly, it must first be creased. Traditionally, the creasing and folding operations have been carried out separately, using different machines. This however is time consuming and inefficient, not least because the stock material must be aligned separately for each operation.

Attempts have been made to construct a combined creasing and folding machine by connecting together separate juxtaposed creasing machines and folding machines. For example, one available machine incorporates a feed system, a creasing apparatus and a buckle folding machine. The three units are arranged sequentially to feed, crease and fold paper and card stock. The feed system draws paper from a stack and delivers sheets to the input of the creasing machine. The output of the creasing machine is connected to an intermediate paper storage unit. The input of the folding machine is fed with sheets from the intermediate paper storage unit. Each of the machines has its own control system which is independent of the control systems of the other machines.

The feed system delivers the paper stock to the creasing machine from the stack. The feed system uses a basic controller which does not allow interruption of the transportation of the sheet, for example by temporarily halting the operation, once the sheet has been picked up from the stack. The creasing unit receives the sheet, stops it in the appropriate position, and performs the creasing operation. The sheet is then transported to the intermediate paper storage unit.

The creased sheet is then fed from the intermediate paper storage unit to the buckle folding machine. The buckle folding process requires the sheet to move continuously through the machine to enable folding to take place. The buckle folding machine has buckle plates for guiding the stock material through the folding machine. These are usually set at about 45 to the paper path and include an end stop. The paper is fed between the buckle plates by rollers and collides with the end stop which causes the paper to buckle towards a nip formed by a pair of fold rollers. The paper is caught in the nip between the fold rollers which exert a force on the paper to create a permanent fold. This type of folding machine causes

extensive marking on stock materials appropriate for digital print engines. This type of machine has to operate continuously at a constant speed otherwise the folding process becomes unpredictable.

The feeding-creasing-folding system thus operates in a continuous/discontinuous/ continuous manner.

In the creasing and folding system described above each of the individual feeding, creasing and folding processes has to be completed before the next process can take place since the system is not integrated. This results in an overall system having a length of at least 5 times the length of the stock being processed. A further drawback to this juxtaposition of separate machines is that the sheets of paper have to be aligned for the creasing operation and then realigned for the subsequent folding operation.

Accordingly the present invention seeks to provide a creasing and folding apparatus and method which mitigates some of the aforementioned problems.

According to one aspect of the present invention there is provided an apparatus for creasing and folding sheets of flexible sheet materials that includes a creaser mechanism, a fold mechanism, a feed mechanism for feeding sheets from the creaser mechanism to the fold mechanism ; and a control system for controlling the apparatus, wherein the fold mechanism includes a pair of rollers having a nip into which a sheet of material is inserted to create a fold, and an inserter mechanism for inserting a sheet into the nip, said inserter mechanism including a knife element having an edge that is arranged to engage a sheet along a crease and to insert said sheet into the nip to produce a fold along said crease.

The apparatus can be produced as a highly compact integrated creasing-folding machine which produces accurate folds in sheets of flexible material, such as paper and card. Forming a crease in the sheet more accurately locates the position of the fold making the folding process more predictable. Also, the arrangement of the apparatus substantially reduces the amount of marks produced on the stock material which makes the invention highly suited to the creasing and folding of digitally printed stock material. The apparatus is also very versatile. The control system can be configured by the operator to perform creasing operations, folding operations and combined creasing and folding operations.

Advantageously the control system is arranged to synchronise the operation of the feeding mechanism with the creaser and fold mechanisms. Preferably the control system includes means for sensing the sheet material at at least one position along its feed path through the apparatus, and means for determining the instantaneous position of the sheet material as it is transported along the feed path. It is also preferred that the control system is constructed and arranged to control operation of the creaser and fold mechanisms according to the determined position of the sheet material.

Advantageously, the control system is programmable, and is constructed and arranged to control the placing and number of folds and/or creases produced by the apparatus according to predetermined requirements.

Preferably the creaser mechanism includes a pair of creasing elements, wherein at least one of said elements is moveable towards the other element to produce a crease in a sheet located between the elements, and a drive mechanism for driving the moveable element.

The creaser mechanism can produce creases at predetermined locations in the sheet and is capable of automatic operation. It can thus be used to crease a batch of documents relatively rapidly. Further, it can be reprogrammed relatively easily to produce a different set of creases. It is therefore highly adaptable. There is no necessity to manufacture a new die for each creasing job and accordingly it is economical in use, even for short production runs.

Advantageously the drive mechanism includes an incremental control device. The incremental control device may be controlled by said control system. In one embodiment the incremental control device is a clutch assembly. Using a clutch assembly allows the drive motor for the creaser mechanism to run continuously. There is no need therefore for the motor to accelerate up to speed, and this provides for fast operation. Further, because the running motor has considerable inertia, which assists operation of the creaser mechanism, the motor does not need to be as powerful as it would otherwise have to be. In another embodiment the incremental control device is a stepper motor.

Preferably the apparatus includes a transport drive motor and a pair of input rollers for transporting sheets of material into said creaser mechanism. The apparatus may further include an encoder constructed and arranged to generate an output signal indicating the

rotational position of at least one of said input rollers, and a sensor, such as an optical sensor, for sensing the leading edge of a sheet as it passes between the input rollers, said control system being connected to said encoder and said sensor to receive signals therefrom.

This enables the control system to monitor the position of the sheet of material continuously as it passes through the creaser mechanism, which enables it to place the creases correctly.

Advantageously the feed mechanism is constructed and arranged to control the position of said sheet material throughout its movement from the creaser mechanism to the fold mechanism. Preferably the feed mechanism is arranged to grip said sheet material throughout its movement from the creaser mechanism to the fold mechanism. For example, the feed mechanism includes a pair of output rollers for removing sheets of material from said creaser mechanism and a pair of input rollers for transporting the sheet to the fold mechanism that grip the sheet until it is engaged by the fold mechanism. Consequently, no realignment of the sheet is required as it moves from the creaser mechanism to the fold mechanism.

In normal operation, the fold mechanism folds sheet materials dynamically and the knife acts as a dynamic deflector. In particular, the feed mechanism controllably feeds the sheet of paper along a feed path where it can be engaged by the knife element. The dynamic folding process significantly reduces the amount of damage caused to the sheet materials by avoiding the dragging action of some traditional devices.

Advantageously, the inserter mechanism is constructed and arranged to insert the sheet into the nip while the sheet is positively engaged by the feed mechanism.

Advantageously the inserter mechanism is constructed and arranged such that during the insertion operation there is substantially no relative movement between the knife edge and the region where it contacts the sheet. Preferably this is achieved by matching the position of the knife edge with the rotational position of the rollers, and hence the position of the sheet of paper. The position of the sheet and the position of the knife edge are controlled by the control system which takes into account the geometry of the paper feed path, the rollers and the knife to ensure that there is no substantial relative movement between the knife edge and the sheet of paper, in the region of contact, when the knife edge is engaged with the sheet. This arrangement leads to a reduction in the amount of damage to the paper as it passes through the folder.

Advantageously in one embodiment the knife element moves in a direction having a component of movement in the feed direction of the sheet material. Preferably the knife element moves rotationally and translationally. For example, the knife edge moves in a curved path and preferably the centre of curvature of the curved path is adjustable. In general, the knife edge follows a path such that the distance between the knife edge and a first fold roller decreases as the knife edge inserts the sheet into the nip.

Preferably the pairs of rollers in the feed mechanism and the fold mechanism are arranged such that the sheet material is gripped by rollers throughout the folding process to accurately control the position of the sheet. It is also preferred that the control system matches the speed ofthe feed mechanism to the fold mechanism rollers. Optionally the speed of the feed mechanism is matched to the creaser mechanism input rollers.

The fold mechanism also includes a sensor for sensing the position of a sheet, which is preferably an optical sensor, and an encoder constructed and arranged to generate an output signal indicating the position of the sheet according to the rotational position of the rollers, the control system being connected to said encoder and said sensor to receive signals therefrom. The control system controls the rotation of the rollers, and hence the position of the sheet of paper, via an incrementally controlled motor, for example, a stepper motor, servo motor or brushless DC motor.

In one embodiment the feed mechanism includes a fold roller that co-operates with a feed roller. This is an efficient arrangement which reduces the number of components required.

Preferably the sheet feed direction and the insertion direction for each fold mechanism are substantially perpendicular.

Preferably the folder includes a first fold mechanism for producing folds in one direction (i. e. on one side of a sheet), and a second fold mechanism for producing folds in a second direction (i. e. on the second side of a sheet), which is constructed and arranged to receive a sheet fed to it from the first fold mechanism. The folder can also include subsequent fold mechanisms which are preferably arranged in series with the first and second fold mechanisms. For example, a folder having four fold mechanisms can be arranged such that

the first and third fold mechanisms produce folds in a first direction and the second and fourth fold mechanisms produce folds in a second direction.

According to another aspect of the present invention there is provided a method of creasing and folding sheets of flexible sheet materials that includes the following steps: feeding a sheet to a creaser mechanism; forming at least one crease in the sheet with the creaser mechanism; feeding the sheet to a fold mechanism having a pair of fold rollers which form a nip and an inserter mechanism, said inserter mechanism having a knife element including a knife edge ; moving the knife element such that the knife edge engages the sheet along the crease and inserts the sheet into the nip; and folding the sheet material along the crease with the fold rollers.

Advantageously the method may include the additional step of gripping the sheet by rollers throughout the creasing and folding process.

Advantageously the method may include the additional step of detecting the sheet by a first sensor at a known position and preferably the sensor detects at least one of the leading and trailing edge of the sheet.

Advantageously the method may include the additional step of determining the position of the sheet within the creaser mechanism according to the distance the sheet has been fed relative to the known position.

Advantageously the method may include the additional step of controlling actuation of the creaser mechanism according to the position of the sheet material within the apparatus.

Advantageously the sheet is controllably fed from the creaser mechanism to the fold mechanism.

Preferably there is no substantial relative movement between the knife edge and the sheet in the region of contact during insertion of the sheet into the fold mechanism.

Advantageously the method may include the additional step of detecting the sheet by a second sensor at a second known position and preferably the second sensor detects at least one of the leading and trailing edge of the sheet.

Advantageously the method may include the additional step of determining the position of the sheet within the folding apparatus according to the distance the sheet has been fed relative to the second known position.

Advantageously the method may include the additional step of controlling actuation of the inserter mechanism according to the position of the sheet material within the folding apparatus.

An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which like references indicate equivalent features, wherein : Figure 1 a is a schematic side view of an embodiment of the present invention; Figure lb is an isometric view showing internal components of the creaser mechanism; Figure 1 c is an isometric view at an enlarged scale, showing components of the creaser mechanism; Figure ld is a left-hand sectional end view, showing components of the creaser mechanism; Figure le is a partial sectional front view, showing components of the creaser mechanism; Figure If is a partial left-hand end view showing components of the creaser mechanism ; Figures 2 to 7 are schematic side views showing the consecutive steps of a first folding operation; and Figures 8 to 11 are schematic side views showing the consecutive steps of a creasing operation and first and second folding operations.

Figure 1 a is a schematic of an integrated creasing-folding machine according to the current invention, which includes a creasing mechanism generally indicated by reference numeral 1,

a folding mechanism generally indicated by reference numeral 100 and an a microprocessor control system (not shown) which controls the operation of the whole machine.

The creasing mechanism 1 includes a pair of input rollers 3 and a pair of output rollers 5, arranged to transport a sheet of paper 7 through the mechanism. Both pairs of rollers 3, 5 are driven by a stepper or servo motor 9 through a step-down gear 11 and a belt drive 13, which is arranged so that the rollers all rotate synchronously (see Figure lb).

The document creasing mechanism 1 also includes a feed mechanism (not shown) of a conventional kind, for example of the type known as a"suction bottom feed system". This feed mechanism, which will not be described in detail, feeds sheets of paper 7 or card one at a time from a stack into the paper transport mechanism of the creasing mechanism.

A through beam infrared sensor 15 is arranged just behind the nip of the input rollers to detect the leading edge of a sheet 7 passing between those rollers 3. An encoder 17 is provided on one end of the upper input roller (see Figure ld). The sensor 15 and the encoder 17 are connected to the microprocessor control system. By sensing the leading edge of the paper and the rotary position of the upper input roller, the microprocessor is able to monitor the exact position of the sheet of paper 7 as it passes through the creasing mechanism.

The lower input roller is connected to the feed mechanism, to ensure that a sheet of paper 7 is not fed into the creasing mechanism 1 while the input rollers 3 are stationery.

The creasing mechanism 1 includes a pair of creasing components mounted between the two sets of rollers 3, 5, comprising an upper creasing component 19 that is normally fixed (although its position is adjustable when the machine is not in use) and a lower creasing component 21 that is mounted for vertical movement. In the arrangement shown in Figure la, the upper creasing component comprises a blade and the lower creasing component comprises an anvil. The positions of the blade and the anvil can however be swapped, so that, for example, the blade is the fixed lower creasing component 21 and the anvil is the moving upper creasing component 19. Both creasing components 19,21 comprise elongate metal bars having a substantially rectangular cross-section, the blade having a profiled rib 23 on its lower edge and the anvil having a profiled recess 25 on its upper edge into which

the rib fits. The profile of the rib 23 and the recess 25 can be changed, according to the desired form of the crease.

Each of the creasing components 19,21 includes at each of its ends a pair of pins 27a, 27b that engage a vertical slot in the creaser frame (see Figures le and If). The inner pins 27b are eccentric and can be adjusted to adjust the lateral positions of the creasing components.

The upper creasing component is locked in position by an adjusting mechanism 28 provided at each end of the component. This allows the vertical position and alignment of the component to be adjusted. The lower creasing component can only be adjusted laterally, but can move vertically, the pins 27a, 27b being guided by the slot 36.

The lower component 21 is driven by a motor 29 (see Figure 1 b), for example an induction motor. The motor is connected through a drive belt 31 to an incremental control device 33 (for example a clutch) that is mounted on a crankshaft 35. Operation of the control device 33 is controlled electronically by the microprocessor. Two power links (or con rods) 37 are mounted on eccentric cranks 39 at the ends of the crankshaft and are connected at their upper ends to the lower creasing component 21. The motor 29 operates continuously but as the control device 33 is normally disengaged, it does not normally drive the crankshaft 35. When the control device 33 receives an"engage"signal from the microprocessor, it closes and the crankshaft is driven through one complete rotation. This drives the lower creasing component 21 upwards against the upper creasing component 19, thereby producing a crease in a sheet of card or paper located between those components, before returning it to its original bottom position. A microswitch 41, located beneath the lower creasing component 21, detects that it has returned to the bottom position and sends a signal to the microprocessor, which then disengages the clutch so that no further movement of the creasing component 21 takes place until the next crease is to be formed.

The incremental control device 33 is not limited to a clutch arrangement, for example, the incremental control device 33 can be a stepper motor that is arranged to drive the crankshaft directly to perform creasing operations, and which is controlled by the microprocessor control system.

The entire creasing mechanism can be tilted relative to the feed table, using a tilt lever 43.

This allows the angle of the crease to be adjusted, so that it is always perpendicular to the lay edge of the paper.

The microprocessor control system may be programmed to produce a plurality of creases at predefined positions. Once the microprocessor control system has been programmed, operation of the machine is fully automatic, the machine taking sheets from the feed table, creasing them as required and delivering them to the folding mechanism input rollers 101, 103.

The folding mechanism 100 has upper and lower contra-rotating input rollers 101, 103 arranged in parallel and in close proximity to one another such that the curved surfaces of the input rollers 101, 103 form a first nip 105. The input rollers 101, 103 are arranged to receive a sheet of paper 7 directly from the creasing mechanism 1 and to feed the sheet of paper 7 horizontally along a feed path to the folding mechanism 100.

Downstream of the first nip 105 is a sensor 109 which detects the leading edge of a sheet of paper 7 as it travels along the feed path. Alternatively, the sensor 109 can be arranged to detect the trailing edge of a sheet of paper 7. Preferably the sensor 109 is an optical sensor having a light transmitting element below the paper feed path and a light detecting element above the paper feed path.

Downstream of the sensor 109 are first, second, and third fold rollers 111, 113, 115 and a fold input roller 117.

The first fold roller 111 and the fold input roller 117 are arranged in parallel and in close proximity such that the curved surfaces of the rollers 111, 117 form a second nip 119 which is arranged to receive a sheet of paper 7 from the input rollers 101, 103 and then feed the sheet of paper 7 substantially horizontally towards a first inserter mechanism 121. The diameter of the fold input roller 117 is typically in the range 30-60mm.

The first and second fold rollers 111, 113 are arranged in parallel and in close proximity such that the curved surfaces of the fold rollers 111, 113 form a third nip 123, which is arranged to feed a sheet of paper 7 vertically towards a second inserter mechanism 125. The second and third fold rollers 113, 115 are arranged in parallel and in close proximity such that the

curved surfaces of the fold rollers 113, 115 form a fourth nip 127, which is arranged to feed a sheet of paper 7 horizontally. The diameters of the first, second and third fold rollers are substantially equal and are preferably in the range approximately 50 to 80mm, for example 60mm.

The distance between the operational pairs of rollers (commonly known as'roller gap') at each nip 105, 119, 123, 127 is in the range 0-3mm, and is determined by the thickness and number of layers of the paper 7 expected to pass through each particular nip.

The rollers 101, 103,111, 113, 115, 117 are interlinked by a gear mechanism and are driven by a stepper motor to rotate with the same tangential speed at the curved surfaces of the rollers. The stepper motor is controlled by the microprocessor control system which receives infonnation from a rotary encoder that is mounted on either the motor or one of the rollers to monitor the true rotational position of the rollers. The upper input roller 101, the first fold roller 111 and the third fold roller 113 rotate in a first direction (clockwise in Figure I a), while the lower input roller 103, the fold input roller 117 and the second fold roller 113 all rotate in a second direction (anti-clockwise in Figure l a). The drive direction of the rollers can be reversed, for example, to clear miss-feeds or paper jams, but this is not done during normal operation. Use of a stepper motor and the associated control system enables the exact rotational position of the rollers, and hence the sheet of paper 7, to be known.

Use of a stepper motor and the microprocessor control system facilitates better control of different thicknesses of sheets 7. This is particularly advantageous since changes in humidity have significant effect upon stock materials that are used for digital print engines.

The first inserter mechanism 21 is arranged to insert a sheet of paper 7 into the third nip 123 formed by the first and second fold rollers 111, 113. The second inserter mechanism 125 is arranged to insert a sheet of paper 7 into the fourth nip 127 formed by the second and third fold rollers 113, 115.

The first inserter mechanism 121 includes a blade 129 having a substantially triangular section, a blade edge 131 and two concave guide surfaces 133 and 135 which extend from the blade edge 131 towards a convex base 137. Preferably the blade 129 has a high stiffness and a low inertia.

At each end, the blade 129 is attached to a blade carrier 139. The blade carrier includes an L shaped plate which extends from the knife base 137 beyond the blade edge 131. Each blade carrier 139 is supported by two pins 141, 143. The first pin 141 is positioned towards the rear edge of the blade carrier 139 and is located for free sliding movement in a blade slide 145, which is positioned below the second fold roller 113. The second pin 143 is located on the blade carrier 139 ahead of the blade edge 131 and is attached by means of a pivot link to the free end of a rotatable blade drive 147.

The blade drive 147 is mounted at its opposite end for rotation about an axis of rotation that is located slightly below the axis of rotation of the first fold roller 111 such that when the blade drive 147 rotates, the blade edge 131 follows a curved path into the third nip 123 formed by the first and second fold rollers 111, 113, convergingtowards apoint substantially equidistant between the first and second fold rollers 111, 113.

The second inserter mechanism 125 is similar to the first inserter mechanism 121 and includes a blade 149 having concave guide surfaces 151 and 153 and a blade edge 155, a blade slide 157, a blade carrier 159 having a first pin 161 located in a longitudinal slot in the blade slide 157 and having a second pin 163 rotatably attached to a blade drive 165. The second inserter mechanism 125 is arranged such that the blade edge 155 follows a curved path into the fourth nip 127 formed by the second and third fold rollers 113, 115.

The components in the second stage folding apparatus are substantially the same as equivalent components in the first folding stage.

The first and second inserter mechanisms 121, 125 are driven simultaneously by a blade drive stepper motor. Operation of the first and second inserter mechanisms 121,125 is 180 degrees out of phase such that as the blade edge 31 of the first inserter mechanism 121 moves towards the third nip 123 formed by the first and second fold rollers 111, 113 from the home position, the blade edge 155 of the second inserter mechanism 125 moves away from the fourth nip 127 formed by the second and third fold rollers 113, 115. The blade drive stepper motor does not rotate continuously in one direction but rather reverses direction to alternately drive the blade edge 131 of the first inserter mechanism 121 towards the third nip 123 and the blade edge 155 of the second inserter mechanism 125 towards the fourth nip 127.

The sensor 109, the roller drive stepper motor and the blade drive stepper motor are linked to the microprocessor control system (not shown) which controls the speed and direction of rotation of both motors, and synchronises the operation of the inserter mechanisms with the rotation of the rollers 101, 103, 111, 113, 115, 117 and with the operation of the creasing components 19,21 and the rotation of the creasing mechanism input and output rollers 3, 5.

Additionally, the folding machine includes a number of guide plates. These include, a first pair of guide plates 167 located beneath the second fold roller 113 to receive, guide and support a sheet of paper 7 fed through the first nip 105 formed by the first fold roller 111 and the fold input roller 117. A second pair of guide plates 169 is located above the third nip 123 formed by the first and second fold rollers 111, 113 to receive, guide and support a sheet 7 fed between the rollers 111, 113.

Optionally, the folding machine may also include additional sensors to sense paper jams and, if necessary, to re-synchronise operation of the inserter and fold rollers. For example, in the mechanism shown in Figure 1 a, additional sensors 171 are provided along the paper feed path after the first inserter mechanism 121 and after the second inserter mechanism 125.

The operation of the creasing and folding machine will now be described with reference to Figures 2 to 11.

During set-up, the operator enters the positions of each of the folds in the microprocessor control system, using a keypad. The microprocessor control system can, for example, store the positions of up to nine folds in nine separate memory locations.

The gap between each operational pair of rollers, for example, the pair of input rollers 3 in the creasing mechanism 1 and the first and second fold rollers 111, 113 or the first fold roller 111 and the fold input roller 117 in the folding mechanism 100, is typically set before the creasing and folding processes begin and may be set manually or by automatic means.

Alternatively, the gap between operational pairs of rollers may be altered dynamically during the folding process by detecting the thickness of the stock material 7 being fed into the apparatus and adjusting the gap between the rollers automatically. In any case, the gap between the rollers is such that operational pairs of rollers can grip the paper 7 without damaging the printed surface of the paper 7.

A sheet of paper 7 or card is fed from the feed mechanism into the nip between the input rollers 3, which then take over transport of the sheet (see Figures 8 to 11). Immediately the leading edge of the sheet exits from the input rollers 3 it is sensed by the infrared sensor 15.

The signal from the sensor 15 is recorded by the microprocessor control system together with a rotary position signal from the encoder 17 mounted on the upper input roller. At this point, the sheet 7 is considered to be registered and throughout its continuing journey through the creasing and folding mechanisms 1,100 its exact position is always known.

Having registered the position of the sheet 7 the microprocessor control system matches the feed speed of the creasing mechanism rollers 3, 5 and the folding mechanism rollers 101, 103, 111, 11-), 115, 117, and synchronises the operation of the creasing components 19,21 and the inserter mechanism 121 to the position of the sheet 7.

As the sheet 7 approaches the position of the first crease 7a, the stepper motor first slows down and then stops the rollers 3, 5 (and hence rollers 101, 103, 111, 113, 115, 117) with the sheet 7 in exactly the right place for that crease 7a to be formed (to within an accuracy of, for example, 0.09mm or better). At this point the incremental control device is activated and the crankshaft is driven through one complete rotation, driving the lower creasing component 21 towards the upper creasing component 19 and trapping the sheet to form a crease 7a. The lower creasing component 21 then drops back to its original home position and the sheet 7 is accelerated back up to full speed towards the next pre-set crease position.

The same procedure is carried out for all subsequent creases. This procedure is repeated for each of the subsequent sheets 7, as they are fed one-by-one into the creasing mechanism 1 from the feed mechanism.

Whilst the sheet 7 is stopped so that the creasing components 19,21 can form creases in the sheet 7, the operations of the inserter mechanisms 121, 125 and the rollers 101, 103, 111, 113, 115,117 are paused. When the sheet 7 starts to move again, operation of the inserter mechanisms 121, 125 and the rollers 101, 103, 111, 113, 115, 117 is resumed. If during the creasing operation a sheet 7 is located in the folding mechanism, the folding operation is not adversely affected, and nor is the quality of the fold affected, by reason of the interruption. This is due to the arrangement of the folding mechanism and the control system.

As the trailing edge of the sheet 7 exits from the nip of the input rollers 3, the sheet sensor 15 detects the trailing edge and signals the microprocessor control system to feed another sheet 7 from the stack of documents in the feed system.

The sheet of paper 7 having at least one crease 7a therein is fed from the creasing mechanism 1 by the output rollers 5 to the input rollers 101, 103 of the folding mechanism 100. Operation of the folding mechanism 100 will now be described with reference to Figures 2 to 7, which show a simplified version of the folding mechanism having only one pair of fold rollers 111, 113 and one inserter mechanism 121. The input rollers 101, 103 and the paper sensor 109 have been omitted for clarity.

A sheet of paper 7 is received by the upper and lower input rollers 101, 103 from the creasing mechanism output rollers 5 and is controllably fed along a horizontal feed path to the second nip 119 via the sensor 109. The sensor 109 detects the leading edge of the sheet of paper 7 and sends a signal to the microprocessor control system to re-synchronise the rotation of the rollers, and operation of the inserter mechanism 121, to the position of the sheet of paper 7.

The sheet of paper 7 is received at the second nip 119 by the first fold roller 111 and the fold input roller 117 before it is released from the grip of the upper and lower input rollers 101, 103, to ensure that the position of the sheet 7 is known as it moves through the mechanism. The first fold roller 111 and the fold input roller 117 feed the sheet of paper 7 along a horizontal path which is below the first and second fold rollers 111, 113 and is substantially perpendicular to axes of rotation of the first and second fold rollers 111, 113.

Initially, the blade 129 of the inserter mechanism 121 is in a home position which is located below the paper feed path. In this position the blade drive 147 is at the anti-clockwise limit of its range of movement. The blade edge 131 is arranged parallel to the axes of rotation of the first and second fold rollers 111, 113.

When the sheet of paper 7 has reached the position where a fold is to be formed (i. e. where the crease 7a is located) the blade drive 147 rotates clockwise, drawing the blade edge 131 into the third nip 123 between the fold rollers. The rotation of the rollers, and hence the movement of the sheet of paper 7, is synchronised with the movement of the blade 129, and

the blade edge 131 is driven into engagement with the sheet of paper 7 along the predetermined fold line 7a. This is achieved by controlling the position of the paper 7 and /or the position of the blade 129. In particular, the position of the blade edge 131 is matched to the position of the paper 7, and hence the rotational position of the rollers, to ensure that there is substantially no relative movement between the blade edge 131 and the paper 7 in the region of contact 7a. This avoids marking the printed surface of the paper.

This can be achieved, for example, by reducing the speed of the rollers, and hence the paper feed speed, as the blade 129 accelerates such that when the blade edge 131 engages the paper 7, the blade edge 131 is travelling at substantially the same speed as the paper 7. The relationship between the paper speed and blade speed is however dependent only on the geometrie of the blade and roller and once established does not subsequently have to be adjusted for that particular blade and roller combination.

The blade edge 131 travels along an accurate path that converges with the third nip 123 formed by the first and second fold rollers 111,113. The motion of the blade 129 is accommodated by linear reciprocating motion ofthe pin 141 along the slot in the blade slide 145 and by rotation of the blade 129 about pin 141 (see, for example, Figure 4).

As the blade 129 rotates anti-clockwise the blade edge 131 rises above the feed path of the paper, engaging the sheet 7 along the crease 7a, and lifting the sheet 7 upwards towards the third nip 123. As the blade 129 rotates the sheet of paper 7 starts to fold about the blade edge 131.

The combined effect of the linear and rotational motion of the blade 129, locates the blade edge 131 in a position substantially in line with the third nip 123 and substantially perpendicular to the direction of the paper feed path as indicated by the arrow A, wherein the blade edge 131 is adjacent to the third nip 123 and equidistant between the first and second fold rollers 111, 113. This position represents the maximum height position of the blade edge 131 (see Figure 6). The distance between the blade edge 131 and the first and second fold rollers 111, 113 in the maximum height position can be controlled according to properties of the paper 7 being folded, in particular the thickness dimension of the paper 7, and the gap between the first and second fold rollers 111, 113.

When the blade edge 131 reaches, or substantially reaches, the maximum height position the sheet of paper 7 is engaged by the first and second fold rollers 111, 113 and is drawn into the third nip 123 (see Figure 7). The first and second fold rollers 111,113 create a permanent fold 7b in the paper 7 substantially along the crease 7a. The crease 7a has the effect of more accurately locating the position of the fold, in particular, ensuring that the fold is perpendicular to the appropriate edges of the sheet 7.

Whilst the blade edge 131 remains engaged with the sheet of paper 7 the position of the blade edge 131 is matched to the rotational position of the rollers, and hence the position of the paper 7, by the control system via the stepper motors such that there is no relative movement between the sheet of paper 7 and the blade edge 131 in the region of contact 7a.

The blade edge 131 moves continuously with the paper 7 and thus provides a dynamic folding process. This has the effect of considerably reducing the amount of damage caused to the surface of the paper 7 compared with traditional folding machines.

The relationship between the position of the blade edge 131 and the rotational position of the rollers, and hence the position of the paper 7, is dependent upon the geometry of the paper feed path, the rollers and the knife.

Since position of the blade 129 is matched to the position of the paper 7 by the control system it is possible to change the paper feed speed without affecting the folding process.

This includes fully stopping and restarting the process without adversely affecting the outcome. This is because the rollers grip the sheet of paper 7 throughout the folding process and thereby accurately control the position of the paper 7, and since the knife position is matched to the position of the sheet 7, if the paper feed speed is increased or decreased, the knife speed is increased or decreased in proportion.

After passing between the first and second fold rollers 111, 113 the paper 7 can be fed to a stacking unit and the blade 129 is returned to the home position by reversing the direction of the knife stepper motor and hence the rotational directions of the blade drive 147 and the blade 129.

In the home position, the blade 129 awaits reactivation by the detection of subsequent sheets of paper 7 by the sensing device 109. The rollers are still driven in their respective original

directions during the blade 129 reversing operation since they are driven by a separate stepper motor.

Alternatively, after the sheet of paper 7 passes between the first and second fold rollers 111, 113, the paper 7 can be fed to a second (or subsequent) folding station to produce a second (or subsequent) fold 7d in the opposite direction (i. e. on the opposite side of the paper 7). This embodiment is shown in Figures la and 8 to 11. The second folding process is performed by the second and third fold rollers 113, 115. The folded sheet of paper 7 is guided into the fourth nip 127 by the second inserter mechanism 125.

The components of the second inserter mechanism 125 are described above, and the operation of the second inserter mechanism 125 is substantially in accordance with the first inserter mechanism 121. Therefore the remainder of this description will focus upon the operation of an embodiment of the present invention having two folding stages with reference to Figures 8 to 11.

The sheet of paper 7, having permanent fold 7b, is drawn between the first and second fold rollers 111, 113 and the knife stepper motor is reversed driving the first stage blade 129 toward the home position and the second stage blade 149 into engagement with the sheet of paper 7 via the blade drive 165. The blade 149 engages the paper 7 with the blade edge 155 along a second crease 7c wherein a second (or subsequent) permanent fold 7d will be produced in the opposite direction by the second and third fold rollers 1 l 3, 115. The blade edge 155 engages the paper 7 such that there is no substantial relative movement between the paper 7 and the blade edge 55 in the region of contact 7c.

The blade 149 rotates in a clockwise direction driven by the blade drive 165 which rotates in an anti-clockwise direction. As the blade 149 rotates, the paper 7 folds about the blade edge 155 and is guided towards the fourth nip 127 formed by the curved surfaces of the second and third fold rollers 113, 115. The sheet of paper 7 is guided by the blade 149 substantially in accordance with the principle of operation of the blade 129 described above.

The blades 129 and 149 can provide a guiding function. This is achieved by the control system activating the blade so as to engage the sheet of paper 7 at or adjacent its leading edge (i. e. as though it were trying to place a fold on the leading edge of the sheet). The

system works in the same manner as described above except that, due to the relative positions of the leading edge of the sheet and the blade edge 131, 155, a fold is not formed.

Instead, the knife 129,149 simply guides the leading edge of the sheet into the nip 23, 27 so that the sheet passes between the fold rollers without forming a fold in the sheet 7. For example, if only one fold is required, the blade 129 of the first inserter mechanism 21 can simply guide the sheet 7 through the first fold rollers 111, 113, without creating a fold, to the second inserter mechanism 125 which can insert the sheet 7 into the nip 127 so that the second and third fold rollers 113, 115 create a fold in the sheet.

The guide surfaces 133, 135, 151,153 of the blades 129,149 are concave shaped to provide a guiding function as the sheet 7 travels through the folding mechanism 100. For example, when the apparatus is used to create a letter fold (in which two folds are provided on the same side of the sheet 7), a flap is created after the first permanent fold 7b has been made in the sheet 7. During the second stage folding operation the concave guide surface 151 directs the flap towards the fourth nip 127 to ensure that the first fold 7b is not undone.

Figure 10 shows that the first stage blade 129 is in its home position when the second stage blade edge 155 is in its maximum height position. Therefore a second sheet of paper 7 can travel through the first stage folding process as the first sheet of paper 7 is engaged by the second and third fold rollers 113, 115 at the fourth nip 127. As the first stage blade 129 moves from the home position towards engagement with the sheet of paper 7 the second stage blade 149 moves from the maximum height position towards its home position.

Additional folding mechanisms can be included in the folding apparatus, for example, the folding apparatus can be arranged to have three or four folding mechanisms. In general, the invention can include any practicable number of folding mechanisms.

The folding apparatus can be arranged for folding sheet material in a number of ways such as the so called'Z'shape,'V'shape,'letter'and'gate'folding techniques.

The control system is microprocessor based. In one embodiment the control system uses artificial intelligence techniques to set up and run the machine from data relating to the different types of fold that will normally be required by the operator. Advantageously, this reduces the skill level required to operate the folding apparatus, bringing the skills required

by the operator in line with the skills required to operate other machines within digital print rooms.

The operation of the whole creasing-folding apparatus is controlled by the microprocessor control system. The creasing-folding apparatus operates continuously. Creases are formed in sheets of paper 7 by the creasing elements 19, 21 which are then transported directly from the creasing mechanism 1 to the folding mechanism 100. Since the control system pauses the folding mechanism 100 when the sheet 7 is stopped in the creasing mechanism 1 so that the creasing components 19,21 can form creases in the sheets of paper 7, an important aspect of the current invention is the ability of the folding mechanism 100 to pause the folding process mid-operation without adversely affecting the folding process, or substantially affecting the quality of the folds formed in the sheets 7. This feature allows the creasing-folding apparatus to operate continuously with the paper 7 being fed directly from the creasing mechanism to the folding mechanism.

It will be appreciated that alterations can be made to the embodiment described above without departing from the spirit of the present invention. For example, rollers can be arranged to rotate in opposite directions, the shape of the blade can be altered and the sheet material folded is not restricted to paper.

Also, the path of the blade 129 (and/or 149) can be changed from a curved path to a linear path. For example, the blade 129 can move diagonally towards the first and second fold rollers 111, 113 at some angle relative to the direction of flow of the paper 7 as indicated by arrow A. Preferably the blade 129 has a component of motion in the direction of movement of the sheet of paper 7 indicated by the arrow A, however, the invention is not limited to this feature, since the blade 129 can be arranged to move vertically into the third nip 123 with the first fold roller 111 and the fold input roller 117 feeding the sheet of paper 7 synchronously with the movement of the blade edge 131.