GB2524528A

GB2524528A - Process for binding digitally-printed sheets

Info

Publication number: GB2524528A
Application number: GB1405354.0A
Authority: GB
Inventors: John Cracknell; Mark Firth
Original assignee: IBIS Integrated Bindery Systems Ltd
Current assignee: IBIS Integrated Bindery Systems Ltd
Priority date: 2014-03-25
Filing date: 2014-03-25
Publication date: 2015-09-30
Also published as: GB201405354D0

Abstract

A sheet binding process consisting of folding individually fed sheets along a fold line and applying glue to the fold line of selected sheets, collecting the sheets in a stack, applying pressure and separating the stack into at least two booklets. Glue is applied to the sheets so that there is one clean sheet between two glued sheets, allowing separate booklets to be formed. A process for separating a stack of nested booklets (A, B) involving moving the booklets towards a tapered blade (52) which engages with the gape of the booklets and opens the booklets as they travel along the blade (52). Two belts, the first belt (54) on the inside page of the innermost booklet (A), the second belt (56) on the outside page of the outermost booklet (B), are used to separate the booklets by driving them at different speeds, such that the two booklets (A, B) are parted.

Description

PROCESS FOR BINDING DIGITALLY-PRINTED SHEETS

This invention relates to the field of printing, in particular to a process for binding individual sheets to form a book, booklet or section of a book.

Digital printing technology allows a printed image to be changed on each consecutive sheet that is supplied to a printer without stopping the printer to fit a new printing plate. This means that the sheets of a book can be printed in sequence. Digital printing therefore offers the potential for rapid collation of consecutive printed sheets into books or booklets. As a result of the ability to combine the printing and collation stages, digital printers are able to print short and medium sized runs of printed material far more quickly and at a lower cost than previously possible.

A digital printer outputs a continuous web printed on both sides. To produce the finished book the printed web must be cut into sheets with each sheet forming two pages of the book. The individual sheets must then be folded, collated, covered, stitched and trimmed. The order of these operations may be varied, and this has led to the development of a variety of modular components, each arranged to implement one or more process steps in the various stages of book production. These components can be reordered as appropriate to the printed material or substituted with components with different performance characteristics. The use of modular components dedicated to particular aspects of the binding process has lead to a great flexibility in design of binding apparatus, making it responsive to the versatility of digital printers in printing different material.

Printing speed dictates the rate at which the printed web can be produced.

The speed of the binding process has some effect on the rate at which books are produced but, to date, binding has generally remained faster than printing. Clearly though, the fewer the number of pages in a book, the more booklets have to be bound and the disparity between printing and binding speeds is reduced. A low pagination booklet typically comprises fewer than 16 pages, the bound product therefore being produced from 4 sheets, printed on one or both sides. Printing speeds are continually increasing and now the rate at which printing equipment can produce low-pagination booklets exceeds the processing speed of equipment designed to bind the product. In order to increase the overall speed of booklet production therefore, there is a perceived need for a higher-throughput binding system that is capable of matching the processing rate of digital printers for booklets containing relatively few pages.

In the prior art, it is known to process multiple books in a single binding cycle. Such processing is often referred to as 2-up" processing and it covers both production of two booklets printed side by side on a sheet and then split and also to a method of stacking two booklets one on top of the other and processing before they are separated. In many cases however, it is only part of the overall binding process that can be run 2-up. For example, it is impossible to use the traditional saddle-stitching process on booklets stacked 2-up. In order to increase the speed of saddle-stitch binding, side by side 2-up processing must be used. Side by side processing however restricts the booklets to having the same number of pages. This constraint prevents a user taking full advantage of the range of personalised printing options available from a digital printer.

Alternative binding processes may use gluing in place of stitching. An example of an apparatus that employs a gluing process in binding digitally-printed sheets is described in WO 2005/072980. This system however only processes one booklet at a time. It employs a fixed-position sheet collector to gather folded sheets one on top of the other in the correct order. As the sheets are fed to the collator a line of glue is applied, for example, to the inside fold of all sheets except the innermost sheet. The stack of sheets is then pressed to bond the glue and then removed from the collator.

It is an object of the present invention to provide a binding apparatus that is capable of processing multiple books or booklets in a single binding cycle.

The present invention provides a process for binding sheets together, the binding process comprising the steps of: (a) feeding successive individual sheets to a folding apparatus; (b) folding each sheet along a fold line; (c) applying glue to the fold line of selected sheets as they are passed over a supporting surface, such that at least one clean sheet is free of glue, this sheet being processed between two glued sheets; (d) collecting successive sheets into a stack in which the fold lines of each sheet are substantially aligned on top of each other; (e) applying pressure to the stack; and (f) separating the stack into at least two booklets, the stack being separable between the clean sheet and an unglued surface of its adjacent sheet.

The process of this invention is advantageous in that it provides the opportunity for processing two or more booklets simultaneously through selected stages of a binding process and then separating them afterwards.

That is, whilst the booklets are stacked, at step (e) above, they can be passed through various components of a binding or trimming process, depending on the particular requirements of a print run, before the stack is separated at step (f). This enables the overall binding process to be carried out at increased speed and therefore with higher throughput.

As stated previously, the need for increased throughput in a binding process is felt most acutely in low-pagination booklet production. It is in this scenario that print speed is beginning to exceed binding speed.

Accordingly, this invention is most suited to binding low-pagination booklets, although it is not of course so limited. Both the method and apparatus of this invention can be used to produce books, book sections or booklets of any size. Reflecting its expected utility however, this description will refer to booklet production. It is to be understood that such reference also encompasses books and book sections of any size and page number, and use of the specific term "booklet" neither carries nor implies any restriction. In fact, the capability of this invention to bind rapidly and efficiently books of any length and size is also advantageous.

Sheets stacked at the fold line, one on top of another, as with the method of this invention, are generally collected on a saddle and then stitched (saddle-bound books). One skilled in the art would not consider saddle-bound books to be amenable to stacked multi-booklet processing as they would be impossible to separate afterwards: all books would be stitched together. In the present invention however, individual sheet gluing is used as opposed to stitching, with the surprising benefit that this offers the possibility of simultaneous processing of separable books. In particular, the stacked sheets may be trimmed as a unit, prior to the booklets being separated.

Alternatively, trimming may be carried out after separation. One disadvantage of trimming books one inside another is that the inner books will be trimmed to a slightly smaller size owing to the slight inward displacement of their spine. It may not always therefore be desirable to trim the stack prior to separation. If the books are separated, then they may be restacked flat, one on top of the next and then subject to simultaneous trimming in order to regain the speed advantage.

Preferably, the trimming operation is carried out in two distinct steps. The sheets are stacked on the saddle, bound and then trimmed along the side edges, while the individual booklets remain stacked. The relative displacement of the spines has no effect on the side-edge trim. The booklets are then separated and have their fore edges trimmed individually.

This enables the increase in speed to be gained from 2-up processing, but without the disadvantage of differing booklet sizes.

The step of separating the stack may include the steps of: moving the folded stack, comprising at least two booklets, one folded inside another, in a direction parallel to its fold line onto a tapered blade positioned to engage with a natural gape in the innermost sheet of the stack; opening the stack to an acute angle as it travels along the blade; engaging one page-side of the stack between a pair of belts, one belt inside the acute angle and engaging the innermost sheet, the other belt to an opposite side of the stack and engaging the outermost sheet; driving the belts at different speeds such that an inner booklet of which the innermost sheet is a part is conveyed at a different speed and therefore moved apart from an outer booklet of which the outermost sheet is a part; removing the separated booklets from the belts; and closing both booklets.

Preferably, the closed booklets are removed from the belts and delivered in the same order as that in which they were printed.

In a second aspect, the present invention provides a method of separating a pair of folded booklets, one positioned inside another, the method including the steps of:.

moving the pair of booklets in a direction parallel to its fold line onto a tapered blade positioned to engage with a natural gape in an innermost sheet of the booklets; opening the pair of booklets to an acute angle as it travels along the blade; engaging one page-side of the booklets between a pair of belts, one belt inside the acute angle and engaging the innermost sheet, the other belt to an opposite side of the stack and engaging an outermost sheet; driving the belts at different speeds such that an inner booklet of which the innermost sheet is a part is conveyed at a different speed and therefore moved apart from an outer booklet of which the outermost sheet is a part; removing the separated booklets from the belts; and closing both booklets.

In a third aspect, the present invention provides apparatus for separating a pair of folded booklets, one positioned inside another, the apparatus including: a wedge-shaped plough guide, oriented with its tapered end towards a direction from which the pair of booklets are conveyed; a first belt with surface holes, the interior of which is connected to a vacuum generator; a first motor connected to the first belt; a second belt with surface holes, the interior of which is connected to the vacuum generator; and a second motor connected to the second belt; wherein the first and second belts are located one above the other and separated by a gap, the gap being arranged to receive one page-side of the booklet pair after opening by the plough guide; and the first and second motors are arranged to drive the respective belts at different speeds.

The invention will now be described, by way of example only, and with reference to the accompanying drawings, in which: Figure 1 illustrates a first stage in the binding process of the present invention in which a flat printed sheet is folded along a central line; Figure 2 illustrates a second stage in the binding process of the present invention in which glue is applied to a folded sheet; Figures 3a, 3b and 3c illustrate various steps of a third stage in the binding process of the present invention in which glued sheets are collected on a sheet collector to form a stack of booklets; Figure 4 is an end on view of a glue application station for use in the process of the present invention; Figure 5 is a schematic diagram of sheet collection apparatus that is operated in accordance with the process of the present invention; Figure 6 is an illustration of apparatus for separating bound booklets in accordance with the present invention.

A typical in-line book assembly apparatus is one in which printed sheets leaving a digital printer are carried by a conveyor, or other transport system, through assemblies adapted for the various stages of book production. In a process in accordance with this invention, and with reference to Figures 1 to 3, the assemblies are adapted to carry out the processes outlined below. For the reason given previously, this invention will be described as processing sheets into booklets.

Printed material generally leaves the printer in one of two formats. If paper is pre-cut before printing, printed sheets of the correct size are output directly from the printer. Alternatively, the printer outputs a web or roll of printed material, which has to then be cut into sheets for onward processing. Either way, correctly-sized sheets, which may be printed on one or both sides, as required, are input to the binding apparatus assembly.

Each sheet 2 is scored and folded along a central fold line, as illustrated in Figure 1.

With reference to Figure 2, sheets are then conveyed to a glue applicator 23. The applicator 23 applies glue to the fold line of most, but not all, of these sheets. In a preferred embodiment of this invention, glue, if applied to a sheet, is applied to the inside of the fold line. For high speed processing in this embodiment, glue is not applied to sheets that are to form the innermost (centre) pages of each booklet.

The sheets then pass to a collector 15, as shown in Figures 3a, 3b, 3c.

The collector 15 includes an arrangement of front and back stops that halt the motion of the sheets as they are conveyed into the collector. This ensures that as they stack in the collection area, the sheets are in registry with each other. For 2-up processing, the sheets that are to make up two booklets are stacked in the collection area. The first sheet of a subsequent (third) booklet is held up and prevented from falling onto the stack until the current stack, comprising two booklets, is pushed out. In this embodiment this process is facilitated by the action of a movable finger 17 mounted on the collector 15 downstream of the direction of travel. As the folded sheets 2 enter the collection area, the finger 17 is oriented (Figure 3a) such that it catches the downstream edge of each sheet 2, holding it up for a pre-set period (Figure 3b). As this sheet is held up by the finger 17, the stacked booklet pair currently on the collector 15 is pushed out. Once the stacked booklet pair has been removed, and the sheets of the subsequent booklet pair are held by the finger 17, the finger 17 is moved away. This allows the retained sheets to fall under gravity to the collector (Figure 3c), ready to be pushed out for further processing. The finger 17 then moves back to its original (Figure 3a) position.

The process described in this embodiment of the invention relates to 2-up processing. That is, two booklets have been gathered in the collector, one inside the other. By leaving the inner sheet of the upper booklet free of glue, this sheet will not be bound to that below it, and the two booklets are not bound together. Of course, this collection process is not limited to two booklets. Two, three or more booklets may be formed into a single stack in the collection area. All that is required is to ensure that the inner sheet of one booklet cannot be bound to the outer sheet of the booklet stacked immediately beneath it. This is readily achieved in a binding process that is based on selectively gluing individual sheets.

In figure 2, glue is shown being applied to the inside of the fold line. It can equally be applied to the outside of the fold line, but the inside fold is preferred for two reasons. First, at the inside of the fold the risk is significantly reduced of the glue accidentally being wiped by an adjacent sheet. The reason for this is that the glue on the underside of an upper sheet will only contact the sheet below when the spine of the upper sheet settles on top of the spine of the lower sheet. Secondly, if the process is interrupted for some reason, glue on the outside of the uppermost sheet would remain exposed and begin to dry. This would weaken the bond with a subsequent sheet, severely reducing the quality of the bound booklet.

Glue on the inside fold however, can be bonded to the lower sheet during a process interruption, should one arise.

The binding apparatus includes a microprocessor that is connected to a series of sensors and also to motors and other operational components of each of the stations within the binding apparatus. One sensor, position at an upstream end of the binding apparatus, includes a barcode reader and each sheet is, in addition to its content, also printed with a barcode. In this way, the microprocessor can identify the sequence of sheets from the start and track each sheet's position up until the point that the sheets are collected on top of each other. Additional readers may be located adjacent alternative paths for covers or inserts to identify and locate these sheets.

The microprocessor can therefore control the machinery at each station to start, stop, or perform some optional operation, in response to a reading received from a particular sensor.

As an alternative to a barcode reader, the sensors may be responsive to 2D codes or other machine-readable characters that may be printed and used to identify individual sheets.

In this embodiment, the binding apparatus includes a buffering device.

This device optionally, under control of the microprocessor, delays output of each or of selected sheets to the conveyor. This delay may be to leave a gap between selected sheets in which to add one or more separately-fed cover sheets or inserts. Alternatively, it may be for the purpose of optimising the rate of arrival of the sheets at the collector 15. For example, if the number of pages in each booklet varies from one to the next, it can be beneficial to change the flow rate of sheets in preference to changing the cycling rate of the binder. Alternatively, the buffering device may be used to avoid a situation in which a thin book is processed inside a very thick book, which would result in the thin book having a significantly smaller spine to fore-edge dimension. In any case, the processor ensures that the sheets and any covers or inserts are sequenced in the correct order and also, if required, are ideally spaced on the conveyor for downstream processing equipment.

A suitable binding process that may be adapted for use with this invention in described in WO 2005/072980. One skilled in the art will readily appreciate that those parts of the process that relate to cutting the sheets, folding, scoring, and feeding separate cover sheets, if required (for example if a cover is of a different material and so originates from a different printer), will apply equally to the process of this invention, and so they will not be described in any great detail here. The result of these initial stages is that individual, printed folded sheets are carried sequentially by a conveyor towards successive stages of processing. The innermost, centre sheet leads the sequence as this sheet will be stacked first upon the collector. Successive outer sheets follow until the final cover sheet of that first booklet. The cover is then succeeded by the innermost sheet of the second booklet. The way in which these conveyed sheets are further processed in order to produce the printed, bound product will be described in more detail, such that differences from the prior art are highlighted.

The conveyor takes the form of a belt that supports the inside fold line of each sheet. The pages therefore extend downwards, to each side of the belt, flaring outwards at their edges, as shown in the figures.

With reference to Figure 4, a glue application station 20 is illustrated. Each folded sheet 2 is fed to the glue application station 20 after folding. Here, glue is applied to the inside of the fold line for every sheet, except the first sheet, of each booklet. The glue application station 20, which is similar in structure to a saddle, incorporates two low friction support surfaces 21 and 22 that are separated along their upper edges by a slot 40 and arranged at an angle to each other such that they depend downwardly and outwardly from each other to form a broken inverted V-shape, in section. The glue application station 20 also includes inner rotating rollers 44 and 45 and outer rotating rollers 44a and 45a which drive each sheet through the station 20 and guide each sheet 2 so that the fold line of each sheet passes over the slot 40.

The glue applicator 23 is provided between the support surfaces 21 and 22 and is aligned with the slot 40 such that the nozzle 23a of the glue applicator 23 is positioned to apply cold glue along the inside of the fold line of the sheet 2. Glue application is controlled by a solenoid valve (not shown). When the solenoid is activated, the valve opens and glue is supplied through the nozzle 23a. Selective activation of the solenoid therefore allows glue to be applied to selected sheets. The glue is preferably applied as a line of individual dots of glue. It is to be understood, though, that hot glue or a continuous line of glue may be applied in the alternative. Each folded sheet is then passed to the sheet collector 15.

Alternatively, the glue applicator 23 may be positioned between and above -12-the support surfaces 21, 22 and aligned so as to apply glue to the outside of the fold line of the sheet 2. It may also be desirable to incorporate two glue applicators in this glue application station 20: one above and one below 23 the slot 40 between the support surfaces. This enables glue to be applied to either (or both, or neither) the inside or the outside of the fold line, as required. For example, the final sheet before the cover may have glue applied to the outside of the fold line in order to bind an (unglued) cover sheet.

The velocity of the sheets emerging from the glue application station 20 is selected so as to be sufficient for the momentum of the sheets to cause the sheets to travel to the collection or stacking area of the collector 15 without any further drive means or externally applied force.

With reference to Figure 5, the collection area extends downstream of the glue application station 20 and terminates at a back-stop 41 (see Figure 3c). The back-stop 41 is preferably in the form of an upstanding plate which intersects the transport direction of the folded sheets and acts to stop the movement of the leading edge of the sheet as the sheet is delivered to the collection area. The back-stop 41 is manually adjustable to permit the collection area to accommodate different booklet spine lengths.

Alternatively, the position of the back-stop downstream of the carrier may be adjusted automatically under the control of the microprocessor.

The movable downstream finger 17 is mounted on the back-stop 41. The finger 17 can be set to protrude (figure 3b) or to stand flat (figure 3c).

When it protrudes, the finger 17 collects the leaded folded edge of selected sheets and prevents these sheets from dropping down onto the collector 15. When standing flat, the finger 17 is clear of the path of the sheets onto the collector 15 and so either allows sheets to stack on the collector unhindered or allows previously-collected sheets to drop. Operation of the moveable finger 17 and its function in holding up one stack whilst a previous stack, which comprises two (or more) booklets, is removed from the collector 15 has been described previously.

The back-stop 41 is provided to halt the forward motion of the folded sheet and to locate the leading edge of the folded sheet in the desired stacking position. Similarly, a front-stop 42 is provided to locate the trailing edge of the folded sheet to ensure that as the sheets are stacked in the collection area, the sheets are in registry with one another.

A collection blade 16 on which the individual sheets are stacked, is located in the collection area, below the downstream finger 17. A knock-up finger 43 is also provided on the back-stop 41 which acts to maintain the downstream registration of the sheets during stacking. Once the stack of sheets is complete, a pusher flight 29 on a conveyor 19 engages with the upstream edge of the completed stack of sheets on the collection blade 16 and displaces it at least slightly downstream before the first sheet of the new stack arrives in the collection area. The trailing edge of this new sheet is free to fall under gravity onto the vacated upstream end of the collection blade 16, whilst its leading edge is supported by the protruding downstream finger 17. The sheet remains in this position as the pusher flight 29 completes removal of the earlier stack from the collection area towards the book finishing assemblies. Downstream movement of the stack of sheets causes the knock-up finger 43 to move so as to permit passage of the stack. At this point, the finger 17 is moved as before and the sheets of the new stack complete their drop onto the collection blade 16.

Timing of the operation of the movable finger 17 and pusher flight 29 are governed by the microprocessor. Barcodes are applied to the printed sheets and may, in one embodiment, identify each sheet by its position in the book and also which booklet the sheet is a part of. In alternative embodiments, it may only identify position in the booklet. In either case, the final sheet of each stack is recognised by the microprocessor either -14-from its unique code or from it being the second such final sheet in a sequence of two booklets that comprise a single stack (or third of three booklets, and so on). When a final sheet of a stack is identified by the barcode reader, the microprocessor tracks this sheet to the collector 15.

When this sheet reaches the collector 15, the finger 17 is immediately moved to its standing position to allow the set of sheets to drop and then returned to its original position to catch the first sheet of the next stack whilst the existing stack of sheets is moved out of the collection area.

Cover sheets, if used, simultaneously pass through the various stages of the process in a similar manner, either on top of one of the sheets 2 or in the gaps between sheets 2. Each cover sheet may also have glue applied to the inside of its fold, and arrives in a position so that it can be laid over the top of the stack of sheets in the sheet collector 15.

As mentioned previously, once all sheets of a pair of booklets (including separately fed covers, if applicable) are in place on the collection blade 16 or saddle, the conveyor 19 moves forward and the pusher flight 29] projecting upwardly from the conveyor 19, engages the edge of the stack of sheets and pushes the stack forward to the next stage of the assembly process.

The back-stop 41 and front-stop 42 in the sheet collector 15, plus the reciprocating knock-up finger 43 ensure the sheets within each stack are registered, preferably within 0.2 mm. The back-stop 41 is adjustable so that its position may be altered to accommodate different sheet and cover lengths.

The conveyor 19 moves the completed stack of sheets 2 forward to a book presser 31 (also shown in Figure 5) which presses the stack of sheets together along the spine of their aligned fold lines. After pressing, the stack of sheets 2, now glued to form two booklets, one inside the other, are conveyed forward from the presser 31. The booklet-pair is then lifted off the conveyor 19, spine first, and rotated through 90° to a flat position. That is, the pair of booklets, one inside the other, are now lying flat and conveyed spine-first towards a trimming assembly. Here the booklets are trimmed to ensure full alignment of page edges and so a neater finished product.

In the process of this invention, two booklets are conveyed together through the trimming process. Generally, two cutting movements are required as three knives trim the edges of the book. A variety of trimming apparatus are known and this invention can be used with any one of these.

Typically two trimming stations are used: one for both side edges to be trimmed and the second for the front edge. The stack must be transported to the first station and aligned at the correct location, cut with one knife movement; transported and aligned at the second station and then cut with a second knife movement. A significant fraction of process time is spent at the trimming stations and the ability to double the number of booklets trimmed in this time by processing books 2-up is a significant advantage provided by this invention. Moreover, if the binding apparatus is operated such that three or more booklets are collected in a single stack, the time saving is yet more significant.

It is known to be difficult to speed up the movement of books between trimming stations, whilst maintaining stop accuracy. Processing books 2-up doubles the throughput without increasing the cycling speed of the machine. One cycle of operation of a trimming machine involves moving the book into position and trimming it. Although such machines can be run at higher speeds, a machine that cycles twice as fast will have heavier components that have to be moved faster and so it consumes more power.

By processing 2-up therefore, this invention offers the potential for the same (doubled) throughput, but without resorting to a more powerful machine. It therefore offers a more efficient use of an existing trimming -16-machine.

In addition to the obvious advantages to be gained from 2-up trimming, even just 2-up transportation contributes to the overall throughput efficiency of binding apparatus. That is, for the same transport speed, or rate of stack processing, the book output rate is doubled. For three or more booklets in a single stack, the output rate is increased correspondingly further.

The in-line binding apparatus and process described above enables the pages within each booklet to be securely held together by means of glue.

Adjacent surfaces of pages from separate booklets are free of glue and so remain unstuck. This, of course, is an essential requirement for multi-book processing.

The next requirement is to separate the booklets and an example of an in-line separator module 50 is shown in Figure 6. The separator 50 receives two booklets A, B, which exit the trimmer travelling spine first with booklet A inside booklet B. The separator 50 includes a first bump turn conveyor that changes the direction of motion of the booklets A, B such that they travel parallel to the spine; a plough guide 52; upper 54 and lower 56 vacuum belts and a second bump turn conveyor. The plough guide 52 is a wedge-shaped blade with a tapered end 52a that is oriented towards the direction from which the booklets A, B approach. The upper vacuum belt 54 is a looped belt in which a series of holes connect the upper surface to a hollow interior. The belt 54 is driven by means of a motor over a shoe to which a vacuum is applied by a vacuum pump. This arrangement essentially results in vacuum suction through the holes in the belt. A valve, under the control of the binding apparatus microprocessor, allows the vacuum to be switched on or off at the shoe. The motor controlling belt motion is also under the control of the microprocessor. The lower vacuum belt 56 is identical to the upper belt 54, with its own respective shoe and motor, but located directly beneath it and separated by a small, variable-sized gap 58.

The microprocessor drives the motor of the upper belt 54 at a higher speed than it drives that of the lower one 56.

The sheets making up the booklets A, B are not closed tightly by the folding process and they therefore have a natural gape 60 in the centre.

After the first bump turn conveyor, the booklets A, B approach the plough guide 52. The tapered end 52a of the plough guide is inserted into the natural gape 60 between the centre pages of the inner booklet A. As the booklets A, B travel further, the increasing size of the guide 52 forces them into a more open orientation, such that one side remains flat upon the conveyor and the other is opened to an acute angle. In this orientation, the booklets A, B are moved to the vacuum belts 54, 56 such that the side that is lying flat on the conveyor passes into the gap 58 between the belts, in the vicinity of its spine. At this point, the vacuum generated by the pump pulls the inner booklet A such that it is held by the upper belt 54 and the outer booklet B such that it is held by the lower belt 56. As a result of the differential speeds at which the motors are driven, inner booklet A is accelerated forwards by the upper belt 54, whilst outer booklet B is decelerated by the lower belt 56. The booklets A, B, of course, separate at the pages where glue is absent: between the cover sheet of the inner booklet A and the inner sheet of the outer booklet B. Booklet A is therefore separated and moved ahead of booklet B. The same process is applied to subsequent booklets and so the booklets are now conveyed in the order in which they were printed. Of course, the separation could equally be achieved with the lower belt 56 being driven faster, but this would result in the outer booklet B leading the inner booklet A, which is not the order in which they were printed. Maintaining print order can be important if different booklets are printed in a single print run.

It can be seen that the size of gap 58 between the belts is variable in order to enable the separation apparatus to process the various thicknesses of booklet that may be bound by this apparatus. For very thin booklets, the gap should be in the range 0.5 mm to 1 mm. In order to allow intermingled single books to pass through the apparatus, obviously without any attempt to separate, the gap will however need to extend a larger distance than its processing range. Ideally therefore, it will likely be variable between 0 and 5mm.

In order to be compatible with other modules of binding apparatus, or if it is simply required to deliver booklets in a spine-leading shingle, the second bump turn conveyor collects the booklets A, B as they leave the vacuum belts 54, 56 and change their direction of travel to spine leading. That is, the booklets A, B leave the separator 50 travelling in the same direction and orientation as they entered it, but separated such that successive booklets are ordered as printed.

It is thought that the principle behind this design of separator can be applied to separate three or more booklets that have been trimmed together. This will likely involve a first stage of separation, such as that described above followed by a means of identifying whether the first stage has advanced one or two booklets. If two booklets, then the leading pair will be input to a second separation stage; if one booklet, then the trailing pair will undergo a second separation stage. The single booklet will simply pass through the second separation stage.

In an alternative embodiment of the invention, the trimming and separation processes are reversed. That is, the combined booklet-pair is conveyed first through the separator, where they exit as individual glued booklets, one following the other. The booklets are then conveyed through the trimming stations, although separately in this embodiment. Although this obviously increases the overall time to complete the binding process, in comparison with other embodiments of this invention, it overcomes the problem of finished booklets having slightly different dimensions if they are trimmed one within another. As stated previously, there is some efficiency to be gained in transporting booklets 2-up, even if they do not undergo simultaneous trimming.

A modified separator may be used in this embodiment. The stacked booklets are pushed out from the collector 15 travelling in a direction parallel with the spine. If travel direction is maintained whilst the booklet pair is rotated to a flat position, the booklet pair is ideally oriented for the plough guide 52 and the bump turn conveyor is unnecessary.

In any version of the separator with a bump turn conveyor, an alternative to switching the direction of travel is simply to rotate the booklets. That is, one or more bump turn conveyors may be replaced by some means of achieving a flow turn.

In a further refinement, the booklets are separated as above, being output lying flat on a front or back cover, ready for trimming. Instead of being fed singly into the trimmer, they are first stacked again, but this time in their flat orientation and then conveyed to the trimmer. As the booklets are stacked one above the other, rather than one inside the other, the gain in processing speed is maintained by multi-booklet trimming without the disadvantage of inconsistent booklet dimensions.

Book stacking order can alternatively be reversed. This may be desirable in order to deliver the booklets after all processing stages in their printed order.

In another variation, side-edge trimming only is carried out prior to separation. Booklets are then input singly to a fore-edge trimming station, which ensures that they are a consistent size. This therefore allows booklets to be processed 2-up through at least a part of the trimming stage.

-20 -The microprocessor is designed to receive input from a user, either over a network or directly, in addition to monitoring barcodes and to exercising control over the various motors and operational controls of the binding apparatus. Use of a microprocessor with this binding apparatus lends itself to the redesign and construction of many different modules in different orders. For example, the separators can be before or after the trimming process and their numbers adapted in accordance with the number of complete booklets that are allowed to form in the collector stack. Different designs of trimming modules may also be used. The particular trimming apparatus used, whether a separate cover feeder is employed and arrangement of separators will all affect the timings of binding apparatus throughput.

It is a further advantage of this invention that the microprocessor can be pre-programmed with algorithms that allow it to calculate timings in response to a user input of information pertaining to the construction and processing of booklets that is to be carried out by the apparatus. With this information, the microprocessor can calculate the rate at which booklets are cycled through the modules following the collator. From this information, it can deduce the ideal rate of input of sheets to the collator and operate the buffering device accordingly.

In detecting barcodes of sheets as they pass a certain point of the binding apparatus, the order in which the sheets are being processed can be followed and checked against the required ordering. If a sheet is detected out of sequence, the microprocessor can calculate and identify which booklet it will be a part of. That booklet can be identified and rejected at a suitable stage subsequent to separation. The microprocessor can additionally calculate the track of booklets through the binding process and monitor and report successful completion and delivery. -21 -

Claims

CLAIMS1. A process for binding sheets together, the binding process comprising the steps of: (a) feeding successive individual sheets to a folding apparatus; (b) folding each sheet along a fold line; (c) applying glue to the fold line of selected sheets as they are passed over a supporting surface, such that at least one clean sheet is free of glue, this sheet being processed between two glued sheets; (d) collecting successive sheets into a stack in which the fold lines of each sheet are substantially aligned; (e) applying pressure to the stack; and (f) separating the stack into at least two booklets, the stack being separable between the clean sheet and an unglued surface of its adjacent sheet.
2. A process according to claim 1 wherein the step of separating the stack is preceded by a step of trimming at least one edge of the stacked sheets.
3. A process according to claim 1 or claim 2 wherein the step of separating the stack is followed by a step of trimming at least one edge of the booklets.
4. A process according to claim 3 wherein the booklets are restacked one on top of another after separation and before subsequent trimming.
5. A process according to any preceding claim wherein the step of separating the stack delivers the booklets in the same order as that in which they were printed.
6. A method of separating a pair of folded booklets, one positioned inside another, the method including the steps of: -22 -moving the pair of booklets in a direction parallel to its fold line onto a tapered blade positioned to engage with a natural gape in an innermost sheet of the booklets; opening the pair of booklets to an acute angle as it travels along the blade; engaging one page-side of the booklets between a pair of belts, one belt inside the acute angle and engaging the innermost sheet, the other belt to an opposite side of the stack and engaging an outermost sheet; driving the belts at different speeds such that an inner booklet of which the innermost sheet is a part is conveyed at a different speed and therefore moved apart from an outer booklet of which the outermost sheet is a part; removing the separated booklets from the belts; and closing both booklets.
7. A process according to any one of claims 1 to 6 wherein the step of separating the stack involves the steps of: moving the folded stack, comprising at least two booklets, one folded inside another, in a direction parallel to its fold line onto a tapered blade positioned to engage with a natural gape in the innermost sheet of the stack; opening the stack to an acute angle as it travels along the blade; engaging one page-side of the stack between a pair of belts, one belt inside the acute angle and engaging the innermost sheet, the other belt to an opposite side of the stack and engaging the outermost sheet; driving the belts at different speeds such that an inner booklet of which the innermost sheet is a part is conveyed at a different speed and therefore moved apart from an outer booklet of which the outermost sheet is a part; removing the separated booklets from the belts; and closing both booklets.-23 -
8. Apparatus for separating a pair of folded booklets, one positioned inside another, the apparatus including: a wedge-shaped plough guide, oriented with its tapered end towards a direction from which the pair of booklets are conveyed; a first belt with surface holes, the interior of which is connected to a vacuum generator; a first motor connected to the first belt; a second belt with surface holes, the interior of which is connected to the vacuum generator; and a second motor connected to the second belt; wherein the first and second belts are located one above the other and separated by a gap, the gap being arranged to receive one page-side of the booklet pair; and the first and second motors are arranged to drive the respective belts at different speeds.