WO2011002297A1

WO2011002297A1 - Document separator and method for the same

Info

Publication number: WO2011002297A1
Application number: PCT/NL2010/050426
Authority: WO
Inventors: Freek Willem Laurens De Ridder; Menno Koppen
Original assignee: Buhrs-Zaandam B.V.
Priority date: 2009-07-02
Filing date: 2010-07-02
Publication date: 2011-01-06
Also published as: NL2003117C2

Abstract

Method for processing substantially flat products (4) such as, for example, documents, comprising: -providing a first transport surface (16); -providing a second transport surface (36), disposed substantially parallel and opposite to the first transport surface, so as to define a product travel path (6) having a path direction (L) between them; -moving the first transport surface and the second transport surface in the path direction (L) along the product travel path at different speeds; -feeding two or more mutually overlapping products into between the first transport surface and the second transport surface at an upstream end of the product travel path; and -conveying the products downstream along the product travel path, thereby allowing the transport surfaces to gradually decrease an overlap between successive products. Also disclosed is an apparatus (1) for executing said method.

Description

Title: Document separator and method for the same

Field of the Invention

The present invention relates to the automated handling of large volumes of documents, and more in particular, to the automated separation of individual documents from a stack of documents.

Background

Document separators, also called document feeders, serve the purpose of repeatedly separating a document from a stack of documents so as to allow for the performance of subsequent actions on each individualized document. Here the term 'document' is to be construed broadly, and intended to include substantially flat, somewhat flexible products, such as, for example, printed matter, envelopes, sheets, magazines, brochures, leaflets, newspapers etc. However, the term 'document' also includes stiff documents, i.e.

documents that are relatively inflexible.

An exemplary application of document separators is a document wrapping line for the compilation of a bundle of mixed documents (i.e.

documents of varying dimensions), such as a bundle of advertising brochures, and the wrapping thereof in a sealed plastic covering. Such a document wrapping line may comprise a main conveyor lane for transporting the document bundle in the making towards a wrapping unit, with a series of document feeders disposed alongside or above the main conveyor lane for successively adding individual documents to the bundle as it passes by. Each document feeder may comprise a document separator, the part of the feeder that individualizes documents from a document stack serving as the supply for document feeder.

Since the composition of a document bundle may vary per batch, a document separator is preferably capable of handling a variety of documents having different dimensions and made of different materials. Particularly challenging are documents that comprise multiple folded pages, possibly stapled together in the form of a booklet. The folds and/or staples in the spines of the booklets make them thicker at the spine than at the open side. Consequently, only a limited number of such booklets can be stacked on top of each other before the pile starts to slide. Such booklets typically arrive from a printer in 'compensated stacks': stacks wherein a fixed number of booklets with the spine on one side is each time alternated with an equal number of booklets with the spine on an opposite side, so as to form a stack that is level and facilitates transport. Not all types of document separators are capable of properly separating booklets from a stack. Rotary feeders, for example, which use a suction cup to pull a lead product from the stack, which product is then engaged by a gripper mounted on a rotating drum, do not handle multi-page products such as booklets well. Other document separators typically require the spines of the booklets to be aligned one way or another. This is because these document separators apply a shear force to the (lead page of the) lead booklet in order to nudge it off the stack. As the booklets include several pages, chances are that a shear force, especially when exerted in a direction towards the spine of a booklet, will shear the pages from each other causing at least the page that is acted on to buckle, crease and possibly even tear. This threat is most immediate to documents that are made of very thin and/or flexible paper. In practice, therefore, stacks of easily shearable documents are often 'decompensated' before they are fed into the document separator. By providing all documents with the same orientation, such that the shear force of the separator can always act in the most favorable direction, the risk of damaging the documents is minimized. This approach works, but it is rather labor intensive— and therefore expensive— since the

decompensation has to be carried out manually.

It is an object of the present invention to provide for a document separator and a method for separating documents from a stack, capable of reliably handling compensated stacks of easily shearable documents. Summary of the Invention

According to one aspect of the invention, a product separator for separating substantially flat products is provided. The product separator comprises a first transport surface and a second transport surface. The first and second transport surfaces extend substantially parallel and opposite to each other, defining a product travel path having a path direction between them. The first and second transport surfaces are moveable in the path direction along the product travel path at different speeds. The product separator further comprises a product supply system, configured to insert products in an overlapping manner (i.e. partially overlapping/shingled, or completely overlapping) into between the first transport surface and the second transport surface at an upstream end of the product travel path, so as to allow the transport surfaces to convey the products downstream along the product travel path, and to thereby gradually decrease an overlap between successive products.

According to another aspect of the invention, a method for processing substantially flat products is provided. The method comprises providing a first transport surface and a second transport surface, the second transport surface being disposed substantially parallel and opposite to the first transport surface, so as to define a product travel path having a path direction between them. The method further comprises moving the first transport surface and the second transport surface in the path direction along the product travel path at different speeds. The method also comprises feeding two or more mutually overlapping products into between the first transport surface and the second transport surface at an upstream end of the product travel path, and conveying the products downstream along the product travel path, thereby allowing the transport surfaces to gradually decrease an overlap between successive products. The device and method according to the present invention do not, unlike many known document separation devices and methods, attempt to separate individual documents from a stack at once. Instead, they do so in at least two stages: a first stage wherein products are successively nudged off the stack, each preferably without losing overlapping contact with either the product that preceded it or with the one that will follow behind, and a second stage wherein the overlap between successive products, separated from the stack, is gradually decreased as they are conveyed downstream along a product travel path. The second stage allows a continuous separation force to be applied over a longer period of time, instead of over a very short period. An optional third stage may be added at the downstream end of the product travel path to pull each most downstream product from the train of still partially overlapping (yet by then individually engageable products), so as to individualize them. It is noted that the removal of products from the stream of partially overlapping documents travelling downstream the product travel path to individualize these products, is truly optional for the purpose of document singulation since a sufficiently long product travel path itself will also lead to a stream of mutually separated, non-overlapping products. The third stage may be integrated or combined with a product positioning unit or action that orderly arranges the individualized products for further processing. Such a product positioning unit may thus expand the field of application of the disclosed product separator, and, for example, allow it to be employed to convert a stack of products or an irregularly shingled stream of products into a regularly arranged/shingled stream of products. The first two stages of the singulation process will now be elucidated somewhat further.

In the first stage, a main surface of a substantially flat lead product of the stack may be engaged by means of a shear force that pushes it into between the first and second transport surface. As soon as the product makes frictional contact with at least one of the transport surfaces, it is not only pushed but also pulled in the direction of the product travel path. The pulling action of the transport surfaces in the transport direction helps to prevent buckling of the product that might result from the shearing push action. Furthermore, the lead product may preferably be pushed off the stack before it loses overlapping contact with its predecessor. Consequently, the lead product is clamped between the supply stack on the one side, and the last product (i.e. the previous lead product) of a train of shingled products on the other. This clamping configuration counteracts a tendency of the product to buckle under the applied shear force. This is even more so in case the stack is oriented vertically and lead products are fed from the top, such that a lead product is always carrying part of the weight of its predecessor, which weight presses down on the lead product thereby preventing its deformation.

The second stage of the separation process takes place between the two parallel transport surfaces that define the product travel path between them. To allow for an effective separation, the two transport surfaces are preferably spaced apart closely, possibly such that they contact each other where no products are present between them, and that they are parted by products where present. Consequently, each inserted product typically contacts at least one of the first and the second transport surface. (This is different only for so-called multi-feeds comprising three or more products that completely overlap each other, and wherein only the outer products contact the transport surfaces.) The transport surfaces both move in a downstream direction of the product travel path, yet at different speeds. The speed of the slowest transport surface is preferably close to the speed with which the lead product is nudged off the stack in the first stage, promoting a smooth transition from the stack into between the transport surfaces. Due to the difference in speed between the two transport surfaces, the at least partially overlapping products clamped between them are gradually separated as they move along the product travel path. The separation process is somewhat erratic, but observed to be very effective. The erratic nature of the process may be explained by the continuously changing interaction between the products on the one hand and the fast- and slow-moving transport surfaces on the other. A product typically moves with the speed of one of the transport surfaces. Which one of the transport surfaces effectively dictates the speed with which a product moves along the product travel path may change any time, depending on the frictional inter-product forces between the product and its neighbors, and the surface area of its main surfaces across which it is in frictional contact with either transport surface.

Because the products travel along the product travel path in an at least partially overlapping manner, typically shingled, the transition between the main surfaces of successive products— viewed in the path direction— is stepwise, in particular when the products have a certain non-negligible thickness. The transport surfaces may preferably be flexible to enable them to follow the contours of the stream of mutually overlapping products, ensuring optimal frictional contact between the transport surfaces and the main surfaces of the products present there between. Two-sided clamping of the products across their main surfaces by— in effect— the two transport surfaces additionally prevents buckling of the products in the direction of the product travel path.

Indeed, the force responsible for the gradual separation of the products as they move along is a shear force, generated by the difference in speed between the two transport surfaces that engage the products from opposite sides. Nevertheless, the products hardly deform as a result of the shearing action. Apart from the clamping action of the transport surfaces, this is partly because the separation takes place gently, over a relatively long product travel path. In a preferred embodiment, the product travel path is long enough to accommodate at least 1.5 products (i.e. the product travel path is at least 1.5 longitudinal - longitudinal being the direction of the product travel path— product dimensions long). By virtue of the minimum length, the graduality of the separation process is optimized. The gradual decrease of the mutual overlap causes the products to progressively take up more path length along the product travel path. To enable a continuous separation process on a finite product travel path, path length between the transport surfaces must be freed continuously, for example by periodically removing the most downstream product from the stream at the end of the product travel path. Removal of downstream products may be performed before the documents have been separated from each other completely; downstream products having only a modest partial overlap with the products that follow them are individually engageable, and may therefore be quickly pulled from the stream.

The device and method according to the invention thus allow vulnerable shearable documents, such as for example the above- described paper booklets, to be reliably separated from a stack without damaging them. Shear forces are applied gently, and measures are taken to prevent buckling at every stage.

It is noted that some known document processing apparatus and methods employ two oppositely disposed, moving transport surfaces to singulate a stack or stream of documents. United States patent 6,135,341, for example, discloses a singulating apparatus including a singulator having a retard assembly and a feed assembly disposed opposite to each other along a document feed path. The retard assembly and the feed assembly co-operate on a stream of documents being transported along the document feed path. As the documents arrive at the feed assembly and the retard assembly, they are separated and transported, one by one, downstream along the document feed path. The method disclosed by US'341 is quite different from the method proposed by the present invention.

The method according to the invention effects a gradual decrease in overlap between successive products by enabling two substantially parallel transport surfaces to act on the overlapping products inserted between them. In doing so, the transport surfaces move in the same direction so as to shear the products relative to each other while transporting them downstream. Even in case the faster transport surface does not get a (static) hold of a product, it is still transported downstream by the slower transport surface, making way for the insertion of new lead products at an upstream point of the product travel path. This is all in contrast to US'341, in which the retard assembly and the feed assembly run in opposite directions, so as to prevent shingled products from being inserted between them. In US'341, the separation of products is not gradual, but to take place at a defined location and before any of the products makes contact with both assemblies. To this end, a first, upstream section of the retard assembly is disposed at an angle with the feed assembly, thereby defining a wedge-shaped document entry opening. As a shingled stack of documents approaches the document entry opening, documents other than the lead document are fed upstream relative to the document feed path due to frictional contact with the retard assembly, while the lead document is fed downstream through frictional contact with the feed assembly. A distinct drawback of this way of separating shingled documents is that it does not work satisfactorily for shearable documents, as is acknowledged by the publication itself (see col.7, In.10-53). Also, the spine must be leading. The effect achieved by the present invention is thus not achieved by US'341 and similar devices and methods.

According to an elaboration of the invention, at least one of the transport surfaces has a dimension, transverse to the path direction, that is smaller than a transverse dimension of the products.

Using transport surfaces that are narrow relative to the products conveyed between them, especially when the transport surfaces are set up to engage center portions of the products, improves control over the motion imparted to the products. Transport surfaces that extend over the full transverse dimension of the products may engage them at many different, difficultly controllable positions across their main surfaces. This may cause a product to experience a moment that works to turn it around an axis perpendicular to the product travel path. Such rotation causes misalignment of the respective product, which misalignment may then propagate along the product travel path and give rise to jams and damaged products. Relatively narrow transport surfaces that centrally engage the products' main surfaces (e.g. along a line extending over their centers) prevent this.

According to a further elaboration of the invention, the products are conveyed along the product travel path in a transversely bent condition relative to the path direction.

The shear forces exerted on the products by the transport surfaces act in a direction parallel to the product travel path. Bending the products in a direction transverse to the direction of the shear forces/product travel path (i.e. such that (at least a directional component of) an axis of curvature extends parallel to the path direction), significantly increases their stiffness and resistance to buckling due to the shear forces. The products do not need to be bent much to achieve the advantageous stiffening effect. The bending of the products may be effected in any suitable manner, and for example include the use of curved transport surfaces, product bending guides alongside the product travel path, or gravity to pull the product sides protruding sideways from between the transport surfaces downwards.

Allowing gravity to bend the products is perhaps easiest. By using first and second transport surfaces that, viewed in a direction transverse to the path direction, extend substantially horizontally, and of which at least the lower one has a transverse dimension (i.e. the dimension perpendicular to the path direction of the product travel path) that is smaller than a

transverse dimension of the products, gravity is enabled to bend the sideward protruding edges of the products downwards, around said lower transport surface.

It is noted that the bending of products may not be restricted to the second stage of conveying the products along the product travel path, but may to the same effect be applied to the first stage during which products are inserted into between the transport surfaces. To this end, the product supply system of the product separator may be configured to insert the products in a transversely bent condition. In a constructionally simple yet effective embodiment, for example, this may mean that a vertically oriented stack of products is supported by a transversely bent support plate, whereby the products— thus held in a bent conditions— are nudged off the top of the stack.

These and other features and advantages of the invention will be more fully understood from the following detailed description of certain embodiments of the invention, taken together with the accompanying drawings, which are meant to illustrate and not to limit the invention.

Brief Description of the Drawings

Fig. 1 schematically illustrates a longitudinal cross- sectional view of a first embodiment of an exemplary document separator according to the present invention;

Fig. 2 schematically illustrates a longitudinal cross-sectional view of a second embodiment of an exemplary document separator according to the present invention;

Fig. 3 schematically illustrates a perspective view of a document separator similar to the one shown in Fig. 2; and

Figs. 4-7 schematically illustrate three transversal cross-sectional views of a product being conveyed in a transversely bent condition between two transport surfaces.

Detailed Description

Fig. 1 schematically illustrates a longitudinal cross- sectional view of a first embodiment of an exemplary product separator 1 according to the present invention. The product separator 1 includes a first belt conveyor 10, a second belt conveyor 30 disposed opposite the first belt conveyor, and a product supply system 50 that is disposed at an upstream location relative to the belt conveyors 10, 30. In the embodiment of Fig. 1, the product supply system 50

comprises an elevator 52 that supports a stack 2 of products 4. The elevator 52 is controlled by a central control unit 8 that aligns the top of the stack 2 with the product travel path 6 extending between the first and second belt conveyors 10, 30. The depicted product supply system 50 further comprises a nudge wheel 54 that rests on the top of the stack 2. The nudge wheel 54 is bearingly mounted to a motorized arm 56 that, under the control of central control unit 8, periodically moves the nudge wheel from left to right, and back. When the nudge wheel 54 is moved from left to right, its rotational motion relative to the arm 56 is restrained by a freewheel assembly (not shown).

Accordingly, the nudge wheel 54 makes frictional contact with the lead product 5, and pushes it sideways into between the first belt conveyor 10 and second belt conveyor 30. After such a nudge stroke the arm 56 is retracted to the left. The nudge wheel 54 thereby rolls back across the top of the stack 2, from the just nudged lead product 5 onto the next, to subsequentlymake a new nudge stroke, and so on. A new nudge stroke is preferably initiated before the last-nudged product clears the stack 2 completely, so as to ensure an overlapping insertion of products between the belt conveyors 10, 30.

For reasons of clarity, the document separator 1 shown in Fig. 1 is depicted at the start of a new batch process. Because of this, no products 4

(other than the lead product 5) are present along the product travel path 6. In full operation though, these further downstream products play an important role in preventing buckling of the lead product 5 as is it nudged off the stack. This is because the products 4 are inserted into between the first and second belt conveyors 10, 30 in an overlapping manner, such that each product at least partially rests on the product following it. Accordingly, the tendency to buckle under the action of the nudge wheel 54 is effectively counteracted by the weight of the preceding product(s). This is clearly visible in Fig. 3, which shows a perspective view of an alternative embodiment of the document separator 1 to be discussed below. One skilled in the art will recognize that various modifications may be made to the product supply system 50 just described. The nudge wheel 54, for example, may be replaced by an elongate roller possessing a larger surface area to contact the products 4 than the nudge wheel. Such a roller may allow the force required to nudge a product 5 off the stack to be distributed over a larger portion of a main surface 4b of the product, so as to minimize the chance of damaging it.

Alternatively, the nudge wheel 54 may be replaced by a topfeed belt conveyor (not shown). Such a topfeed belt conveyor may be structurally similar to and oriented in line with the second belt conveyor 30 (to be discussed below). In addition, it may be independently operable, for example under the control of the central control unit 8. The topfeed belt conveyor may be disposed at least partly above the product stack 2, such that the elevator 52 may push a top product 4 of the stack in frictional contact with a (lower) belt run of the topfeed belt conveyor that provides for a (third) transport surface. The lower belt run of the topfeed belt may extend up to above the upper belt run 14 of first belt conveyor 10, such that a downstream portion of the (third) transport surface of the topfeed belt conveyor is disposed opposite to an upstream portion of the first transport surface 16. Indeed, this implies that the second belt conveyor 20, as shown in Fig. 1, would become a little shorter (seen in the path direction L). During operation, the transport surface of the topfeed belt conveyor may be moved in the path direction L, preferably at a velocity approximately equal to that of the first transport surface 16. Such a topfeed belt conveyor configuration may aid in smoothly and overlappingly inserting products 4 into between the first and second belt conveyors 10, 20, preventing immediate and erratic product 4 separation upon insertion between them due to the difference in speed between transport surfaces of the first and second belt conveyors 10, 20.

Further, although a top feed assembly 50 as shown in Fig. 1 is preferable because it limits the inter-product frictional forces that must be overcome when a product 5 is nudged from the stack 2, a bottom feed assembly is conceivable as well. In that case, however, the weight of the stack 2 is likely to press on the lead (bottom) product, and to be too large to allow the product to be nudged from the stack without significant shear forces. Of course, in a bottom feed assembly an elevator 52 to lift products may be omitted. As an intermediate alternative, the orientation of the stack 2 may be changed. The stack 2 may, for example, extend horizontally with the products 4 having a vertical orientation. Other orientations are possible as well. It is also contemplated that the product supply system 50 may not feed products 4 off a stack 2. It may, for example, include a supply conveyor feeding an irregularly shingled stream of products into between the first and second belt conveyors 10, 30.

An advantageous alternative embodiment of the product supply system 52 may comprise two elevators that are moveable upwards within a vertically extending elevator shaft. The shaft may snugly accommodate the stack of products to prevent the products from accidentally sliding relative to each other, while the elevators may move the products upwards through the shaft. The elevator shaft may not be closed all-around, and may for example comprise a series of horizontally spaced, upright bars that define its cross- section (seen from above or below). Each of the elevators, in turn, may include a forklift whose fork teeth reach through the bars of the shaft to support and lift a stack of products. At any one time only one of the elevators is intended to support the stack of products from below. As the stack is slowly depleted due to the continuous removal of products off the top, and the stack- supporting elevator moves upwards to keep the top of the stack in alignment with the product travel path, room is created in the shaft for the other elevator to bring in a new supply of products. The new supply may be inserted into the shaft from an underside thereof, and be moved upwards by the other elevator so as to connect it to the stack held by the stack- supporting elevator. Upon connection, the stack-supporting elevator may be retracted sidewards from the shaft, passing its load on to the other forklift, which at that moment becomes the stack-supporting elevator. Outside of the shaft, the retracted elevator may be reloaded with a supply of the products, from which point on the cycle may start all over again. Two (or more) forklifts may thus 'leapfrog' over one another to provide a continuous supply of products.

Referring again to the embodiment of Fig. 1. The elevator 52 may comprise a support surface 53 to support and lift the stack 2 of products 4. The support surface 53 may be continuous (e.g. a plate, as shown) or discontinuous, including several sub-surfaces that together define the support surface (e.g. a number of teeth of a forklift). In either situation, the support surface may be transversely bent, such that products supported by the elevator 52 are curved with respect to an axis of curvature that has a least a directional component parallel to the direction in which the shear force, exerted by the nudge wheel 54, is applied to the lead product 5. In the case of the continuous support surface 53, such a situation may be achieved by bending the support surface accordingly. In the case of the discontinuous support surface, the sub-surfaces may be thought of as selected portions of a transversely bent continuous support surface. The transversely bent condition of the products 4, 5 has a stiffening effect, and counteracts the tendency of the products to buckle under any shear force applied in a direction parallel to the axis of curvature.

As the lead product is nudged from the stack, it is received between the first belt conveyor 10 and the second belt conveyor 30. Each of the belt conveyors 10, 30 features a flexible belt 12, 32 that is wrapped around a number of pulleys 18, 38. At least one of the pulleys 18, 38 of each belt conveyor 10, 30 may be driveable by a motor (not shown) that is under the control of the central control unit 8; the other pulleys may be idler pulleys, possibly spring loaded to keep the respective belt taut. The belt conveyors 10, 30 are disposed opposite to each other, on opposite sides of a product travel path 6. The immediately opposing belt runs 14, 34 of belts 12, 32 define this product travel path 6 between them. It is clear that, in the embodiment of Fig. 1, the product travel path 6 is straight and extends entirely in a path direction L. Furthermore, the path direction L at the point where products 4 are inserted into between the belt runs 14, 34 is substantially parallel to the direction in which the nudge wheel 34 pushes the products 4 off the stack 2. Although this latter relation is preferably preserved, it is contemplated that the product travel path 6 may not be straight in other embodiments. The product travel path 6 may for example be curved around a rotating drum, a circumference of which may provide for the first transport surface. It is further understood that, for reasons of clarity, the (vertical) distance that separates the belt runs 13 and 24 is somewhat exaggerated; in practice, the belt runs may even abut each other in case no products are present between them. It is also contemplated that different embodiments of the product separator according to the invention do not include belt conveyors 10, 30, but instead different conveying devices, such as, for example series of separate, juxtaposed (driveable) wheels, to define the product travel path, and to receive the products and carry them forward.

The belt runs 14, 34 provide a first transport surface 16 and a second transport surface 36 respectively. Viewed in both the path direction L and the transverse direction T (i.e. the two mutually perpendicular directions that define the plane of the transport surfaces), the transport surfaces 16, 36 extend in a substantially horizontal plane. In other embodiments, however, the orientation of the transport surfaces may be chosen differently.

The two belt conveyors 10, 30 are driven such that the belt runs 14, 34 both move in the path direction L, but at different speeds. In the embodiment of Fig. 1, the speed of the first, lower transport surface 16 is close to the speed with which a lead product 5 is nudged off the stack 2 by the nudge wheel 54. This promotes a smooth, buckle-free transition of the lead product 5 from the stack 2 into between the transport surfaces 16, 36. The speed of the second, upper transport surface 36 is preferably higher than that of the first, lower transport surface 16. In some embodiments, however, the lower transport surface 16 may move faster than the upper transport surface 36.

Using the setup shown in Fig. 1 a continuous stream of overlapping, typically shingled products 4 may be inserted between the two transport surfaces 16, 36. As mentioned, such a stream of shingled products is clearly illustrated by Fig. 3. The continuity of the stream contributes to a high throughput capacity, but is not a strict requirement otherwise. As the products 4 travel downstream along the product travel path 6, their main surfaces 4a, 4b are in contact with the transport surfaces 16, 36: the lower main surfaces 4a of the products are, at least partially, in frictional contact with the first transport surface 16, while the upper main surfaces 4b are, at least partially, in frictional contact with the second transport surface 36. Due to the flexibility of the belts 12, 32, the transport surfaces 16, 36 are capable of following the step-wise transitions between the main surfaces 4a, 4b of adjacent products 4 so as to ensure optimal frictional contact between the transport surfaces 16, 36 and the main surfaces 4a, 4b of the products. As can be seen in Fig. 3, the degree of mutual overlap between the inserted products 4 is relatively large at the upstream side of the product travel path 6. It is even possible that occasional multi-feeds occur: two or more products 4 having a one hundred percent overlap, incidentally fed from the stack 2 as a whole due to relatively high inter-product frictional forces. Such multi-feeds do not present a problem to the apparatus and method according to the invention and may, in some embodiments, even be inserted purposefully.

Due to the difference in speed between the two transport surfaces

16, 36, which are in contact with the overlapping products 4 as described above, the products are gradually separated as they move along the product travel path 6. It is conjectured that the difference between the dynamic and static friction coefficients of the transport surfaces 16, 36 plays an important role in the gradual separation process. A transport surface 16, 36 that drags a product 4 along does so under static friction; the product does not move relative to that transport surface. At the same time, the product 4 will move relative to the other transport surface 16, 36 under dynamic friction.

Both the static and dynamic friction experienced by a product 4 depend on the normal contact force, i.e. the force with which a main surface 4a, 4b of a product 4 is pressed against a transport surface 16, 36. The larger the surface area of a main surface 4a, 4b contacting the respective transport surface 16, 36, the larger the frictional force between the product and said transport surface is. The size of the contacting surface area is, of course, dependent on the overlap between successive products 4. Due to the continuous interaction between the transport surfaces 16, 36 and the main surfaces 4a, 4b of the products 4, the amount of surface area through which a product contacts either one of the transport surfaces changes over time. Accordingly, a product 4 may at one moment favor being dragged under static friction by the first transport surface 16, while at the next it may have made sufficient areal contact with the second transport surface 36 to attach thereto, or vice versa. The underlying frictional force balance for each product may tip back and forth as the products travel along the product travel path 6, causing the products 4 to move relative to each other, thereby gradually diminishing their mutual overlaps.

Referring again to Fig. 1. Downstream of the belt conveyors 10, 30 a product positioning unit 70 is disposed. By the time the products 4 reach the product positioning unit 70, the separation process is in a sufficiently advanced phase to ensure that possible multi-feeds have been rectified, and that the overlap between successive products 4 has become small enough to allow a most-downstream product to be quickly extracted from the stream. This is what the product positioning unit 70 does. The unit 70 may comprise two rollers 72 or other rotational elements, disposed on opposite sides of the product travel path 6. The rollers 72 may be disposed at fixed mutual positions, so as to define a certain gap between them of approximately the thickness of a single product. Alternatively, at least one of the rollers 72 may be (spring-) biased into contact with the other, so as to allow for a flexible gap size between them. At least one of the rollers 72 is driveable, preferably at a relatively high speed compared to the speeds of the belts 12, 32. In the embodiment of Fig. 1, both rollers 72 are driveable under the control of the central control unit 8. Extraction of products 4 from the stream of products requires that the driveable rollers 72 rotate in the directions indicated in Fig. 1: clockwise for the lower roller 72 and counter-clockwise for the upper roller 72. As soon as a lead edge of a most- downstream product 4 comes into frictional contact with the rotating rollers 72, the product will be pulled into between them and be accelerated in the path direction L. The fast

acceleration draws the most-downstream product loose from any remaining overlap with the product following it, and effects its definitive separation from the stream.

Downstream of the product positioning unit 70, a further belt conveyor or another product handling unit may be disposed to accept the individualized products for further processing. In the case of a further belt conveyor, for example, the product positioning unit 70 may arrange the individualized products in a regularly shingled manner on a belt thereof, so as to transport them to a further processing station.

The product separator 1 according to the invention may be fitted with a control unit 8 that controls one or more of the product supply system 50, the first belt conveyor 10, the second belt conveyor 30 and the product positioning unit 70. The control unit 8 may be configured to gear the operations of these components towards one another, enabling a smooth operation of the separator 1 as a whole. To this end the control unit 8 may for example provide an adjustable master clock signal, from which clock signals for driving the other components, such as the product supply system 50 and the conveyor belts 10, 30, may be derived through a fixed multiplier.

Additionally, the control unit 8 may comprise a number of sensors, disposed at various locations in or around the separator 1, to provide the control unit with operational information, e.g. about the number of inserted and extracted documents, the occurrence of multi-feeds, extraction timing information, normal pressure applied to the transport surfaces 16, 36, etc. The control unit 8 may further include an operator control panel through which an operator can monitor and adjust the performance of the product separator 1. It is understood that conventional technology, e.g. Siemens' SIMATIC product range, may be used to implement the control unit and its functionality.

Fig. 2 schematically illustrates a second exemplary embodiment of a product separator 1 according to the invention. Relative to the embodiment shown in Fig. 1, both the product supply system 50 and the belt conveyors 10, 30 have undergone some modifications. Fig. 3 depicts a perspective view of an embodiment of a product separator 1 similar to the second embodiment shown in Fig. 2, but in some more detail and in an advanced phase of operation. Together, the figures clearly illustrate the modifications of the second embodiment relative to the first embodiment of Fig. 1

The product supply system in Figs. 2 and 3 does not make use of a nudge wheel 54 that executes discrete nudge strokes to push products 5 off the top of the stack 2. Instead, the belt 32 of the second, upper belt conveyor 30 has been extended with a belt run 42 that extends up to above the top of the vertically oriented stack 2. The elevator 52 forces the top of the stack in contact with this belt run 42, which provides a third transport surface 44. As the second belt conveyor 30 is driven, the third transport surface 44 moves (in unison with the second transport surface 36) in the path direction L, and products 5 forced in contact with the third transport surface 44 will be successively nudged off the stack in a shingled manner. Again, the flexibility of the belt 32, and hence of the belt run 42, is important. Due to its flexibility, the third transport surface 44 is able to follow the step-wise transitions between the main surfaces 4b of successive lead products 5, and thus to engage a following product before a certain preceding product is fully clear of the stack 2. This aspect is well illustrated by Fig. 3.

The belt conveyors 10, 30 of the embodiment of Fig. 2 have additionally been adapted to include a number of pressure pulleys 20, 40. A first series of pulleys 20 is associated with the first belt conveyor 10, such that belt run 14, and hence the first transport surface 16, is supported from below at a series of discrete points along the product travel path 6. A second series of pulleys 40 is associated with the second belt conveyor 30, such that belt runs 34, 42, and hence the second transport surface 36, are pressed on from above at a series of discrete points above the stack 2 and along the product travel path 6. The pulleys in each series may be disposed

equidistantly from each other, whereas the two series may be shifted relative to each other in the path direction L, so that the pulleys of the first series 20 and the second series 40 are alternatingly and non-opposingly disposed along the product travel path 6, as shown in Fig. 2. Here the phrase 'alternatingly and non-opposingly' is intended to convey that the idea that, viewed along the path direction L, a number of pulleys 20 of the first series disposed on a first side of the product travel path 6 is alternated with a number of pulleys 40 of the second series disposed on a second side of the product travel path, and so on, such that the pulleys of the first and second series do not immediately oppose each other. Along the product travel path 6, the pressure pulleys 20, 40 gently force the first and second transport surfaces 16, 36 towards each other, whereby their alternating, non-opposing placement distributes the overall pressing force. It has been observed that a finer distribution of the pressing force leads to more efficient separation of products. The pressing force exerted by the pulleys 20, 40 is preferably non-progressive in the sense that thicker products 4 would cause the transport surfaces 16, 36 to be pressed together harder. This is because a larger normal pressing force increases the inter-product frictional forces between overlapping products 4 conveyed along the product travel path 6, and thus renders separation of these products through shearing more difficult. An alternative approach to applying normal forces between products 4 and transport surfaces 16, 36 may employ vacuum belt conveyors. An advantage of using vacuum belts it that they barely affect the inter-product frictional forces. This is because they do not force overlapping products 4 onto each other, but merely suck the products against the belts (indeed often diminishing inter-product frictional forces).

In the embodiment of Fig. 1, the stack 2 is not supported from its sides; as a result it might tip over or start to slide. To prevent this, the product supply system 50 may be provided with a substantially vertically extending product guide. Such a product guide may be static, e.g. an upright wall structure or the like, and be provided on a downstream side of the stack 2 so as to balance the stack 2 when the top product 5 is nudged off. A drawback of a static structure, however, is that products 4 that reside in the stack 2 may have downstream edges that frictionally abut the guide, causing the edges to bend or curl downward as the stack 2 is moved upwards relative to the guide. Such curled edges may make it more difficult to nudge the products 4 off the top of the stack 2 one by one. To overcome this problem, the product supply system 50 may be provided with a substantially vertically extending, dynamic guide, capable of moving along with the products 4 in the stack 2 in the vertical direction; see Fig. 2. The dynamic guide may, for example, take the form of a substantially vertically oriented guide belt conveyor 58. The guide belt conveyor 58 may feature a flexible guide belt 64 that is wrapped around a number of pulleys 60, 62. At least one of the pulleys may be driveable by a motor (not shown) that is under the control of the central control unit 8; the other pulleys may be idler pulleys, possibly spring loaded to keep the guide belt 64 taut. The guide belt conveyor 58 may be powered and/or controlled such that the guide belt run 66 facing and abutting the side of the stack 2 is moved in the vertical direction, preferably at a speed approximately equal to or slightly greater than an average upward speed of the products 4 in the stack 2. If the speed of the guide belt run 66 is chosen slightly greater than the average upward speed of the stack 2, e.g. plus about 0-10% of the average speed, the downstream edges of the products 4 may curl somewhat upwards. The upwardly curled edges have been found to facilicate the separation of the products 4 from the stack 2.

The dynamic guide belt conveyor 58, and in particular the upper pulley 62 thereof, may further facilitate the separation of (single) products 4 from the stack 2 as it allows the upper products to gradually assume a mutually shingled state. That is: seen in the upward direction of the stack, the products 4 are allowed to lean/extend increasingly in the downstream direction L (see Fig. 2). As soon as a product reaches the top of the stack 2, it may extend over the radius of the upper pulley 62, and be taken along by the third transport surface 44. A force exerted by a pressure pulley 40 opposite to upper pulley 60 of the guide belt conveyor may be adapted to ensure that only one product 4 is allowed to pass between said two pulleys.

Fig. 3 illustrates an embodiment of the document separator 1 that is similar to that shown in Fig. 2, this time in a perspective view. Some aspects illustrated by Fig. 3 have already been referred to above, but are summarized here briefly for the sake of completeness. Firstly, the figure elucidates the gradually diminishing overlap between successive products 4 as they travel down the product travel path 6. As can be seen, most upstream products 4 overlap with their neighbors and the transitions between the main surfaces 4a, 4b of these overlapping products are step-wise. The flexibility of belts 12 (not visible) and 32 enables them to follow these transitions, thereby promoting proper frictional contact between the main surfaces and the belts. Fig. 3 also illustrates how gravity mildly bends the products 4 in a transverse direction as they are conveyed. This manner of bending the products 4 to counteract buckling is further discussed in relation to Fig. 5.

Figs. 4-7 schematically illustrate, in transverse cross-sectional views, four alternative approaches to transversely bending products 4 as they are conveyed downstream along the product travel path 6. In the embodiment of Fig. 4, two bending guides or rails 80 are used to bend the products 4. The bending guides 80 extend in the path direction L, parallel to the product travel path 6. For symmetry, one guide or rail is disposed on either side of the product travel path 6. The guides or rails 80 are configured to engage a side portion of the products 4 so as to bend them around an axis of curvature C, parallel to the path direction L. To minimize friction between the products 4 and the guides 80, the guides may for example be provided with small, interfacing rollers (not shown). In the embodiment of Fig. 5, gravity is used to bend the products 4. This is made possible by using first and second transport surfaces 16, 36 that, viewed in the transverse direction T, extend

substantially horizontally, while at least the first, lower transport surface 16 has a transverse dimension that is smaller than a transverse dimension of the products 4. The products 4 thus protrude from between the transport surfaces 16, 36, which allows gravity to bend them transversely, relative to an axis of curvature C. In the embodiment of Fig. 6, the transport surfaces 16, 36 themselves are curved relative to an axis of curvature C.

Consequently, the products 4 clamped and conveyed between them are too. In the embodiment of Fig. 7, a table 82 may be provided on either lateral side of the product travel path 6 and extend in the direction L thereof. Each table 82 may provide for a smooth, upper support surface 83 for supporting portions of the products 4 that protrude laterally from between the transport surfaces 16, 36. The tables 82 may be movably arranged, in particular to allow them to be tilted/rotated to include a suitable angle with the horizontal. In one embodiment, the tables 82 may for example be movable between a first position in which their support surfaces 83 extend substantially horizontally and/or in the plane of the lower transport surface 16, and a second position in which their support surfaces 83 include an angle with the horizontal, as shown in Fig. 7. Furthermore, product bending guides 80 may be provided. In the embodiment of Fig. 7 the product bending guides 80 need not be fixedly or statically arranged; instead they may rest on the (lateral edges of) upper main surfaces of the products 4. Gravity may thus force the product bending guides 80 in contact with the products 4 at a defined and constant force that is determined by the weight of the bending guides 80. This may in turn force the products 4 in contact with each other (where they overlap) and with the supporting surfaces 83 of the tables 82. While the bending of the products 4 may increase their resistance to buckling, pressing the products 4 against the tables 82 may additionally results in their flattening, which reduces the risk of creasing. It will be appreciated that the illustrated manners of bending products are merely exemplary, and that other approaches may be

implemented to the same effect.

Although illustrative embodiments of the present invention have been described above, in part with reference to the accompanying drawings, it is to be understood that the invention is not limited to these embodiments. Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, it is noted that particular features, structures, or characteristics of one or more embodiments may be combined in any suitable manner to form new, not explicitly described embodiments. List of elements

1 product separator

2 stack of products

4 product

4a,b first, lower (a) and second, upper (b) main surface of product

5 lead product of stack

6 product travel path

8 central control unit

10 first belt conveyor

12 belt of first belt conveyor

14 belt run defining first transport surface

16 first transport surface

18 pulleys of first belt conveyor

20 pressure force distributing pulleys

30 second belt conveyor

32 belt of second belt conveyor

34 belt run defining second transport surface

36 second transport surface

38 pulleys of second belt conveyor

40 pressure force distributing pulleys

42 belt run defining third transport surface

44 third transport surface

50 product supply system

52 elevator

53 elevator support surface

54 nudge wheel

56 motorized arm

58 guide belt conveyor

60 upper pulley of guide belt conveyor

62 lower pulley of guide belt conveyor

64 guide belt

66 stack facing guide belt run

70 product positioning unit

72 wheel or roller

80 product bending guide

82 υroduct suυυort table 83 support surface of product support table

C axis of curvature

L path direction

T transverse direction relative to path direction

Claims

Claims We claim:

1. A product separator (1) for separating substantially flat products (4, 5) such as, for example, documents, comprising:

- a first transport surface (16) and a second transport surface (36),

whereby the first and second transport surfaces extend substantially parallel and opposite to each other, defining a product travel path (6) having a path direction (L) between them, and whereby the first transport surface and the second transport surface are moveable in the path direction along the product travel path at different speeds; and

- a product supply system (50), configured to insert products in an

overlapping manner into between the first transport surface and the second transport surface at an upstream end of the product travel path, so as to allow the transport surfaces to convey the products

downstream along the product travel path, and to thereby gradually decrease an overlap between successive products.

2. The product separator according to claim 1, wherein at least one of the transport surfaces (16, 36) has a dimension, transverse to the path direction (L), that is smaller than a transverse dimension of the products (4).

3. The product separator according to claim 2, wherein said at least one of the transport surfaces (16, 36) is configured to centrally engage main surfaces of said products (4).

4. The product separator according to any of the claims 1-3, wherein a first belt conveyor (10) provides for the first transport surface (16), and wherein a second belt conveyor (30) provides for the second transport surface (36).

5. The product separator according to any of the claims 1-4, wherein the product supply system (50) is configured to insert the products (4) in a transversely bent condition relative to the path direction (L).

6. The product separator according to any of the claims 1-5, wherein the first and second transport surfaces (16, 36), viewed in a direction transverse to the path direction (L), extend substantially horizontally.

7. The product separator according to any of the claims 1-6, configured to convey the products (4) in a transversely bent condition relative to the path direction (L) along the product travel path (6).

8. The product separator according to any of the claims 1-7, wherein at least one of the first transport surface (16) and the second transport surface (36) is transversely curved relative to the path direction (L).

9. The product separator according to any of the claims 1-8, further comprising at least one product bending guide (80), disposed alongside the product travel path (6) and configured to engage the products (4) being conveyed between the transport surfaces (16, 36) so as to bend them

transversely relative to the path direction (L).

10. The product separator according to any of the claims 1-9, further comprising at least one table (82) that extends alongside the product travel path (6) and that provides for an upper support surface (83) configured to support portions of the products (4) that protrude laterally from between the first and second transport surfaces (16, 36), said table (82) being movably arranged so that it is tiltable to different angles in order to support the products (4) at varying degrees of curvature.

11. The product separator according to any of the claims 1-10, wherein the product supply system (50) includes a top feed assembly that feeds products off the top of a substantially vertically oriented stack (2).

12. The product separator according to claim 11, wherein the product supply system (50) includes a guide belt conveyor (58), having a guide belt (60) that is configured to abut a substantially vertically oriented side of the stack (2) and to move in the same direction as the stack at a speed that is

substantially the same or greater than the speed of the stack.

13. The product separator according to at least claims 4, 6 and 11, wherein the second transport surface (36) is disposed above the first

transport surface (16), wherein the second belt conveyor (30) further provides a third transport surface (44) that is substantially in line with the second transport surface (36) and that is disposed above the vertically oriented stack (2), and wherein the product supply system (50) is configured to continuously position the stack such that a top of the stack is in contact with said third transport surface, which is configured to move in unison with the second transport surface.

14. The product separator according to at least claims 4, 6 and 11, wherein the second transport surface (36) is disposed above the first

transport surface (16), wherein a topfeedbelt belt conveyor provides a third transport surface that is substantially in line with the second transport surface (36) and that extends from above the vertically oriented stack (2) to above the first transport surface (16), and wherein the product supply system (50) is configured to continuously position the stack such that a top of the stack is in contact with said third transport surface, which is configured to move in unison with the first transport surface.

15. The product separator according to any of the claims 1-14, further comprising:

- a first series of pulleys (20) associated with the first belt conveyor (10); and

- a second series of pulleys (40) associated with the second belt

conveyor (30);

wherein the first and second series of pulleys are configured to respectively force the first transport surface (16) and the second transport (36) surface towards each other, whereby the pulleys of the first series and the pulleys of the second series are non-opposingly disposed along the product travel path (6).

16. The product separator according to any of the claims 1-15, further comprising a product positioning unit (70), located at a downstream end of the product travel path (6) and including two rollers (72), said rollers being disposed in parallel, on opposite sides of the product travel path, and each roller having an axis of rotation that extends substantially transverse to the path direction (L), such that a product (4) reaching the downstream end of the product travel path is receivable between the rollers, and wherein at least one of the rollers is driveable to accelerate a received product.

17. The product separator according to at least claim 2, wherein at least one of the first belt conveyor (10) and the second belt conveyor (30) is a vacuum belt conveyor.

18. The product separator according to any of the claims 1-17, wherein the operation of one or more of the product supply system (50), the first belt conveyor (10), the second belt conveyor (30) and the product positioning unit (70) is controlled by a control unit (8), which is configured to gear their operations to one another.

19. Method for processing substantially flat products (4) such as, for example, documents, comprising:

- providing a first transport surface (16);

- providing a second transport surface (36), disposed substantially

parallel and opposite to the first transport surface, so as to define a product travel path (6) having a path direction (L) between them;

- moving the first transport surface and the second transport surface in the path direction (L) along the product travel path at different speeds;

- feeding two or more mutually overlapping products into between the first transport surface and the second transport surface at an

upstream end of the product travel path; and

- conveying the products downstream along the product travel path, thereby allowing the transport surfaces to gradually decrease an overlap between successive products.

20. The method according to claim 19, wherein the product travel path

(6) is long enough to accommodate at least 1.5 products (4).

21. The method according to claim 19 or 20, wherein the products (4) are fed into between the transport surfaces (16, 36) in a transversely bent condition relative to the path direction (L).

22. The method according to any of the claims 19-21, wherein the products (4) are conveyed along the product travel path (6) in a transversely bent condition relative to the path direction (L).

23. The method according to any of the claims 19-22, wherein at least one of the transport surfaces (16, 36) has a dimension, transverse to the path direction (L), that is smaller than a transverse dimension of the products (4).

24. The method according to any of the claims 19-23, wherein the first and second transport surfaces (16, 36), viewed in a direction (T) transverse to the path direction (L), extend substantially horizontally.

25. The method according to claims 23 and 24, wherein the lower one of the first and second transport surfaces (16, 36) has a dimension, transverse to the path direction (L), that is smaller than a transverse dimension of the products (4), allowing gravity to bend the products around said lower transport surface.

26. The method according to any of the claims 19-25, wherein the feeding of two or more mutually overlapping products (4) comprises:

- providing a vertically oriented stack (2) of substantially flat products;

- continuously positioning the stack such that a top product (5) is

aligned with the product travel path (6) defined by the first and second transport surfaces (16, 36); and

- repeatedly engaging the top product and inserting it into between the first transport surface (16) and the second transport surface (36).

27. The method according to claim 26, wherein a third transport surface (44) is provided above the vertically oriented stack (2), and wherein the stack is continuously positioned such that the top product (5) of the stack is forced into contact the third transport surface (44), which third transport surface is moved in the path direction (L) of the product travel path (6) to insert the top product into between the first and second transport surfaces (16, 36).

28. The method according to any of the claims 19-27, further

comprising:

- forcing the first transport surface (16) towards the second transport surface (36) at a first series of locations along the product travel path

(6); and

- forcing the second transport surface towards the first transport surface at a second series of locations along the product travel path, whereby the locations of the first series and the second series respectively are non-opposingly disposed along the product travel path.

29. The method according to any of the claims 19-28, further

comprising:

- engaging a product (4) conveyed to a downstream end of the product travel path (6), and accelerating said engaged product so as to withdraw it from any remaining overlap with a following product, thus individualizing said engaged product.

30. The method according to claim 29, further comprising:

- rearranging the engaged and individualized products (4) according to a predetermined ordering.

31. The method according to any of the claims 19-30, wherein at least one of the first, the second and the third transport surface (16, 36, 44) is flexible.

32. The method according to any of the claims 19-31, wherein at least one of the first transport surface (10) and the second transport surface (30) is provided with perforations, and wherein a vacuum is applied to the perforations to suck products (4) against said at least one transport surface.