For convenience, banknotes will be used as an example of such sheets throughout this specification. The term banknote will also be used to encompass other items of money's worth that have detectable features requiring validation, such as tickets and vouchers.

Machines that receive and handle banknotes will be referred to in this specification as host machines. Host machines typically include a validator that validates a banknote upon insertion by checking its authenticity and condition and rejecting it if it is deemed to be invalid. An example of a validator is disclosed in our International Patent Application No. PCT/GB92/01809 published as W093/07590. Once validated, the banknote typically passes from the validator into a secure long-term store, such as a removable cassette-type stacker or a cashbox within the host machine. An example of a stacker is disclosed in our European Patent Application No. 98307086.3. Once in such a long-term store, a validated banknote typically cannot be removed by or dispensed to the user: it can only be removed from the host machine when, for example, the stacker is replaced or the cashbox is emptied by a person maintaining or servicing the host machine.

The disclosures of our International Patent Application No. PCT/GB92/01809 and our European Patent Application No. 98307086.3 are incorporated herein by reference.

For various reasons, it is desirable that validated banknotes paid into host machines can be refunded, used as change or given out as a prize. However, the current practice in such machines is typically to pay out refunds, change or prizes in coins. This is due to difficulties and delays in handling banknotes within the host machine and, until the present invention, the bulk and complexity of banknote storage devices that are able to dispense as well as to receive banknotes.

For the purposes of this specification, coins are taken to include tokens that are commonly used to pay out prizes won on gaming machines.

So far as refunds are concerned, there is no problem with an invalid banknote which will simply be rejected by the validator and hence will be returned to the user rather than being validated and fed through into long-term storage. Rather, the problem relates to validated banknotes because, once validated and sent to long-term storage, a banknote is effectively lost to the user and refunds have to be given in coins. The user seeking a refund from the host machine may then be left with a bulky and heavy mass of coins, and a desire not to use that machine again if possible.

The refund problem is particularly significant when an item for sale within a host machine requires more than one banknote to match or exceed that item's purchase value, in which case the requisite banknotes are inserted one after another, usually into the same validator. If, for some reason, the user aborts the purchase after a banknote has been inserted and validated but before the transaction is complete, it is particularly desirable that the host machine should return the same notes fed into it by the user, rather than have recourse to a separate store of coins. It is similarly desirable that prizes and change can be paid out in banknotes rather than coins.

Accordingly, from one aspect, the invention resides in apparatus for handling validated banknotes in a host machine, the apparatus comprising a banknote cache, an entry path means by which a validated banknote can enter the cache, and an exit path means by which a validated cached banknote can exit the cache, the exit path means including at least one exit path along which a validated cached banknote can be dispensed on demand from the cache to a user. This aspect of the invention may also be expressed as a method of handling validated banknotes in a host machine, comprising caching at least one validated banknote and, on demand, dispensing that banknote from the cache to a user. The cached validated banknote can be dispensed by the host machine as a refund, as change or as a prize.

The invention makes it possible for the host machine to store an appropriate variety and quantity of banknotes in such a flexible and easy-to-access way that large sums can be paid out as prizes, change and refunds more quickly and easily than could be

achieved by dispensing an equivalent value in coins. Apart from pleasing the users of the host machine, the invention has commercial advantages for the operators and owners of the host machine because it helps to keep the machine in service longer by placing lesser demands upon its limited coin storage capacity, and by reducing wear.

These benefits are particularly clear in countries having relatively low-value coins.

Conveniently, the exit path means and the entry path means can share an entry/exit path communicating between the cache and the user. However, it is also possible for the exit path means to include at least one exit path leading from the cache to the user, separate from the entry path. This is an example of a preferred method concept that involves moving a cached validated banknote from one banknote-handling mechanism in the host machine to another banknote-handling mechanism in the host machine.

Another example of this method concept involves forwarding a cached validated banknote to a long-term store in the host machine from which the banknote cannot be dispensed to the user. Accordingly, the exit path means preferably includes at least one exit path leading to a long-term store. The invention therefore allows an adequate float of various banknotes to be kept for prize, refund or change purposes, and for any excess to be transferred to long-term storage such as a banknote stacker and/or a cashbox within the host machine.

There may be a plurality of long-term stores to which a corresponding plurality of exit paths lead, each exit path leading to a respective one of the plurality of long-term stores. This enables the host machine to sort the banknotes it receives into different denominations, and to stack the appropriate denomination in the appropriate stack.

For optimum flexibility, some embodiments of the invention contemplate moving a cached validated banknote to different sections of a cache. That is to say, the cache can be subdivided into sections and a cached validated banknote can be moved between and among those sections. For example, each section of the cache can have an exit path leading to an entry path of another, neighbouring section of the cache. As a convenient way of sorting banknotes into respective denominations, each section can have a further exit path leading to a respective long-term store.

The apparatus of the invention can include a validator associated with the entry path for validating a banknote by reference to information carried by the banknote.

Alternatively, the apparatus can simply be adapted to work downstream of a validator so that the entry path receives only validated banknotes.

Preferably, the cache comprises at least one cache storage device mounted on a carriage for indexible movement into and out of communication with the entry path means or the exit path means. More preferably, to maximise the size and flexibility of the cache, the carriage comprises a plurality of cache storage devices each capable of storing a respective validated banknote. This plurality of cache storage devices can be arranged in various ways such as a circular, looped or rectilinear array, and the cache storage devices of the plurality can be movable along a straight or curved movement path. To deal with the latter possibility, articulated links may be provided between the cache storage devices to permit linked movement of the carriages along the path.

It is therefore possible for each cache storage device to have a respective carriage movable along the movement path. For even greater flexibility, the carriage of each respective cache storage device can be independently movable along the path.

The cache storage device contemplated by the above aspects of the invention is an invention in itself, allowing temporary storage of a banknote in a manner that is optimally compact and yet allows the banknote to be withdrawn quickly and reliably from storage in good condition when the banknote is required by other banknote- handling mechanisms within the host machine.

Specifically, from another aspect, the invention resides in a cache storage device for a banknote, comprising a support for supporting a major portion of a banknote in a collapsed configuration and a holding region for holding a minor portion of the banknote in a banknote path leading to and from the support. Preferred embodiments of the invention involve coiling the major portion into the collapsed configuration.

This aspect can similarly be expressed as a method of caching a validated banknote within a host machine, comprising advancing the banknote along a banknote path to

cause a major portion of the banknote to adopt a collapsed configuration in or on a support, and holding a minor portion of the banknote in the banknote path beside the support. In practice, the method further comprises retracting or driving back the banknote along the banknote path to recover the major portion from its collapsed configuration.

Advantageously, the support includes a roller around which the major portion can be coiled and/or a storage chamber in which the major portion can be coiled, and the holding region is a slot communicating with the roller and/or the storage chamber.

Elegantly, therefore, the storage chamber may be shaped to impart longitudinal curvature to the major portion of an incoming banknote, and where a roller is also employed, the roller is preferably within the storage chamber and the major portion is coiled around the roller between the chamber wall and the roller.

The cache storage device of the invention preferably further comprises a banknote drive means for driving the banknote into and out of the collapsed configuration in or on the support. A sensor may be associated with the holding region to control the banknote drive means in response to the passage of a leading or trailing edge of a banknote.

Where a roller is associated with the storage chamber as aforesaid, that roller conveniently serves as the banknote drive means. In preferred embodiments, the roller is offset within the storage chamber to lie close to or in contact with an internal wall portion of the storage chamber and the banknote path is positioned to lead a banknote to that wall portion to be gripped between the roller and the wall.

Optionally, the roller includes a slot or groove that can be aligned with the banknote path to engage an end portion of an incoming banknote, or the banknote can be gripped between the roller and a co-operating pinch roller.

The invention encompasses a host machine fitted with a banknote-handling apparatus or a cache storage device defined in the above aspects, or operating according to any of the related methods.

In order that the invention can be more readily understood, reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 is a schematic sectional side view of a storage device comprising a storage chamber having an offset roller disposed within, with a banknote entering the storage chamber; Figure 2 corresponds to Figure 1 but shows the banknote partially within the storage chamber and coiling around the roller within the chamber, the roller being driven clockwise in this instance to draw the banknote into the chamber ; Figure 3 corresponds to Figures 1 and 2 but shows the banknote in a stored configuration, with a major portion of the banknote coiled around the roller within the chamber and a minor portion of the banknote lying in a holding region outside the chamber; Figure 4 corresponds to Figures 1 to 3 but shows the banknote exiting the chamber, the roller being driven anti-clockwise in this instance to uncoil the banknote and expel it from the chamber; Figure 5 is a schematic sectional side view showing an alternative embodiment of a storage device in which an additional roller is positioned to engage a banknote; Figure 6 is a schematic sectional side view showing a further alternative embodiment of a storage device in which the roller has a slot that receives and engages a banknote; Figure 7 is a schematic side view of a possible set of storage devices as shown in any of Figures 1 to 6, the devices being grouped in a flexible loop with each device being akin to a link of a chain forming the loop; Figure 8 is a schematic side view of another possible set of storage devices as shown in any of Figures 1 to 6, the devices being distributed around the

circumference of a drum or carousel and hence being disposed in a circular array; Figure 9 is a schematic side view of a further possible set of storage devices as shown in any of Figures 1 to 6, the devices being disposed in-line as a rectilinear cassette; Figure 10 is a schematic side view of a grouped plurality of sets of storage devices, the sets in this instance being of the drum or carousel type shown in Figure 8 although other set configurations or formats such as those shown in Figure 7 or Figure 9 are also possible; and Figure 11 is a sectional side view of a practical embodiment of the invention in the form of a cassette that integrates a banknote stack, a banknote entry path and a banknote payout path with a single carousel-type set of storage devices interposed between the paths and the stack.

Referring firstly to Figures 1 to 4 of the drawings, a storage device 1 comprises a structure 2 defining a cylindrical chamber 3 and a slot 4 that intersects and communicates with the chamber 3. The chamber 3 is capable of receiving a banknote 5 inserted into the device through the slot 4, for which purpose the slot 4 and the chamber 3 are approximately 90mm long when measured parallel to the central longitudinal axis of the chamber 3, orthogonal to the direction of insertion. This dimension slightly exceeds the typical width of a banknote.

It will also be noted that the slot 4 has a significant length parallel to the direction of insertion. The slot 4 thereby defines a holding region for an end portion of a stored banknote 5, as will be explained later. It will also be explained later how one or more storage devices 1 can be arranged and grouped in various ways within a host machine, but for present purposes it can be assumed that the incoming banknote 5 has just been validated by a validator (not shown) upstream of the storage device.

A roller 6 lies within and extends along the chamber. The roller 6 can turn in either direction about an axis of rotation that is parallel to, but offset from, the central

longitudinal axis of the chamber 3. For this purpose, the roller 6 is driven by a reversible drive means (not shown) such as a stepper motor that optionally drives the roller 6 through a transmission for reduction and/or reversal purposes. Designing such a drive means and its control electronics will be within the compass of the skilled reader and so their layout need not be described here.

The cross-sectional diameter or radius of the roller 6 and its degree of offset with respect to the central longitudinal axis of the chamber 3 are such that the roller 6 slidingly contacts the inner cylindrically-curved wall of the chamber 3. Moreover, the roller 6 is preferably biased into contact with the chamber wall 3 as shown by the force arrow within the roller 6 in Figures 1 to 4. The roller 6 has a resilient surface that conforms to the chamber wall 3 and so defines an elongate area of contact between the roller 6 and the chamber wall 3, in the form of a narrow strip or band extending along the chamber 3 and the roller 6.

Similarly, the slot 4 is parallel to the central longitudinal axis of the chamber 3 but intersects the chamber 3 along a chord offset from that axis. As shown in the drawings, this chord is above the central longitudinal axis of the chamber 3 and is also above the axis of rotation of the roller 6, which in turn is above and to the right of the central longitudinal axis of the chamber 3. The area of contact 7 between the roller 6 and the chamber wall 3 is therefore defined between respective upper right portions of the chamber wall 3 and the roller 6.

It is emphasised that these various directions and relative dispositions are given solely for the purpose of describing the drawings and that the orientation of the device does not matter in practice. For example, it is equally true to say that the plane in which a banknote 5 is inserted through the slot 4 lies between the axis of rotation of the roller 6 and the area of contact 7 between the roller 6 and the chamber wall 3.

Sensor means 8 such as a photocell pair are disposed in the structure 2 above and below the slot 4 as illustrated, to be responsive to the presence and movement of a banknote 5 within and through the slot 4.

Referring specifically now to Figures 1 and 2, an incoming banknote 5 has an end portion which, during its insertion into the slot, 4 defines a leading or downstream edge 9. The presence of the leading edge 9 in the slot 4 is detected by the sensor means 8 which, via control electronics, causes the drive means to turn the roller 6 clockwise as shown in Figure 2. As the plane of the incoming banknote 5 intersects the chamber 3 above the axis of rotation of the roller 6, the first end portion of the banknote 5 is guided upwardly around the roller 6 with assistance from the clockwise movement of the roller 6.

During this movement as the banknote 5 is pushed further into the slot 4, the leading edge 9 of the banknote is increasingly confined in the narrowing, tapered space between the roller 6 and the chamber wall 3 as it approaches the area of contact 7 between the roller 6 and the chamber wall 3. Eventually, the first end portion is gripped between the roller 6 and the chamber wall 3 and the banknote 5 is then progressively drawn into the chamber 3, being driven by the roller 6, with the assistance of its resilient surface, to slide around the chamber 3 in a coiling or furling action. In particular, it will be noted that if and when the first end portion of the banknote 5 completes a circuit of the chamber wall 3 and returns to the region of the slot 4 as shown in Figure 2, it is steered back toward the roller 6 by the incoming upstream web portion of the banknote 5 that approaches the roller 6 at a tangent, and hence is eventually trapped between that upstream web portion and the roller 6.

Clockwise movement of the roller 6 and hence continued coiling of the banknote 5 within the chamber 3 continues until the trailing edge 10 at a second end portion of the banknote passes the sensor means 8. The control electronics then immediately stop the roller 6. The banknote 5 is then in the stored configuration shown in Figure 3, in which all of the banknote 5 is contained within the structure 2 (it will be noted that the trailing edge is buried in the slot 4) and a major downstream portion of the banknote 5 is coiled within the chamber 3.

Significantly, the minor second end portion of the banknote 5 at the upstream end that defines its trailing edge 10 remains within the aforementioned holding region that is defined by the length of the slot 4 in the direction of insertion. The significance of this will be clear upon considering Figure 4, in which the control electronics effect a

request to retrieve the banknote 5 from the storage device 1 by driving the roller 6 anti-clockwise to expel the banknote 5. The pre-engagement of the second end portion of the banknote 5 in the slot 4 reliably guides the uncoiling or unfurling banknote 5 back out of the chamber 3 through the slot 4, effectively peeling the banknote 5 off its own coil.

Were the second end portion of the banknote 5 allowed to enter the chamber 3 during insertion of the banknote 5 and hence to fall out of engagement with the slot 4, it would be a major and quite unnecessary technical challenge reliably to locate the trailing edge 10 and to lift it back out of the chamber 3 into the slot 4 when required.

The technical challenge would be all the greater given the variable quality of banknotes in public circulation.

During expulsion of the banknote 5 from the chamber 3, the second end portion of the banknote 5 becomes the leading end and when that end emerges from the slot 4 to a sufficient extent, it can be gripped by other banknote-handling mechanisms within the machine, or indeed by a person using the machine who has, for example, called for a refund of a banknote just inserted and validated. In this way, the banknote can be withdrawn from the slot 4 even when the first end portion, now the trailing end, is no longer gripped and driven by the roller 6. The sensor means 8 detects the trailing edge 9 of the banknote as it passes back out through the slot 4 and signals the control electronics to stop the motor and await insertion of another banknote, whereupon the sequence of Figures 1 to 4 can start over again.

Figures 5 and 6 show alternative embodiments of the storage device that operate in much the same sequence as the embodiment of Figures 1 to 4 but grip a banknote differently. Like numerals are used for like parts.

The embodiment of Figure 5 provides an auxiliary pinch roller 11 situated largely outside the chamber 3. The pinch roller 11 co-operates with a main roller 6 in the chamber 3 to grip a banknote 5 and to drive its coiling or uncoiling movement within the chamber 3. As contact between the chamber 3 and the main roller 6 is no longer necessary to drive the banknote 5, it will be noted that the main roller 6 is not offset within the chamber 3 to the extent shown in Figures 1 to 4 and that there is continuous

clearance all round the main roller 6 between the main roller and the chamber wall 3.

Instead, the axes of rotation of the main and auxiliary rollers 6,11 are offset from each other to the extent that their combined radii match the distance between their axes of rotation. This brings the main and auxiliary rollers 6,11 into rolling contact with one another along an area of contact parallel to their axes of rotation.

The area of contact between the main and auxiliary rollers 6,11 is analogous to the area of contact 7 between the roller and the chamber wall of Figures 1 to 4, and is correspondingly positioned with respect to the chamber 3, the main roller 6 and the slot 4. Similarly, one or both of the main and auxiliary rollers 6,11 preferably has a resilient surface so that the theoretical line of contact between them is widened into a strip, in which case their combined uncompressed radii can be slightly greater than the distance between their axes of rotation. The skilled reader will appreciate that either or both of the main and auxiliary rollers 6,11 can be driven by suitable drive means, and will also appreciate that either or both of those rollers 6,11 can be biased toward the or each other. The force arrow in Figure 5 shows that the auxiliary roller 11 is biased toward the main roller 3 in the illustrated embodiment.

Figure 6 shows an embodiment that, again, has a roller 6 in the chamber 3 to drive the coiling and uncoiling movement of a banknote 5 within the chamber 3. However, in contrast to the previous embodiments, the leading end portion of a banknote 5 is not initially gripped by the outer surface of the roller 6 but instead is gripped by being received in a retaining slot or groove 12 within the roller 6. Specifically, the roller 6 shown in Figure 6 is penetrated by a planar retaining slot 12 whose plane is a chord situated above the axis of rotation of the roller 6 and so asymmetrically bisects the cross section of the roller 6.

In the start position shown in Figure 6, the roller 6 lies with its retaining slot 12 opposed to and aligned with the slot 4 that communicates with the chamber 3 and defines a banknote path in and out of the chamber 3. It will be appreciated that the leading end portion of an incoming banknote 5 on the banknote path will enter the retaining slot 12, for which purpose the end of the retaining slot 12 that receives the banknote 5 has outwardly-splayed wall portions 13. Once the banknote 5 has reached the full depth of the retaining slot 12, which event can be sensed by additional sensors

associated with the roller 6 (not shown), the roller 6 is turned clockwise to trap the banknote 5 between the roller 6 and the chamber wall 3. The minimal clearance between the roller 6 and the chamber wall 3 prevents the banknote 5 being withdrawn from the retaining slot 12 until the roller 6 is wound back to its start position, and so enables the roller 6 to draw a major portion of the banknote 5 into the chamber 3 in a coiled configuration in the same way as the previous embodiments.

In the embodiment of Figure 6, the roller 6 acts like a spool around which the banknote 5 is wound or rolled-up, whereas the embodiments of Figures 1 to 5 are subtly different in that the roller 6 pushes the banknote 5 around the curved wall of the chamber 3 to impart coiling curvature to the banknote 5. Nevertheless, this difference is indeed subtle because in all of the illustrated embodiments, the banknote 5 ends up coiled around the roller 6 by virtue of the position of the roller 6 within the chamber 3.

Each storage device of Figures 1 to 6 can hold only one banknote 5 and yet can act as a basic cache enabling that banknote 5 to be refunded or to be held in the host machine until it is paid out as change or as a prize or is eventually sent to long-term storage such as a stack. However, the need for host machines to handle different denominations and larger multi-note amounts means that it will usually be desirable for such machines to hold more than one banknote 5 in a cache. Accordingly, Figures 7 to 9 show various ways in which a plurality of storage devices 1 can be grouped in a set to create a cache that can hold a corresponding plurality of banknotes.

The embodiments of Figures 7 to 9 have two main features in common. The first common feature is a source of banknotes for cache storage, being an entry point or path to the cache, and a receiver of banknotes from cache storage, being an exit point or path from the cache. Both functions are performed in these simplified examples by a validator 14 acting as both a source and a receiver, although different entry and exit points (for example, a validator and a stacker) and, indeed, multiple entry and exit points (for example, a separate validator and a separate stacker for each respective denomination of banknotes) are also contemplated by the invention. Of course, a validator 14 will tend to be both an entry and an exit point in practice, as expulsion back through the validator slot is probably the simplest way of refunding a validated

note immediately after validation. However, a dedicated refund mechanism could of course be provided as a separate exit point if desired.

The second common feature in the embodiments of Figures 7 to 9 is a carriage that supports one or more storage devices for relative indexible movement with respect to the validator 14 so as to align the slot of a selected storage device with a banknote path 15 of the validator 14. This movement can be driven and controlled by drive means and control electronics (not shown), whose design is within the compass of the skilled reader. Whilst all of the embodiments of Figures 7 to 9 have at least one carriage, they diverge in the arrangement of the carriage and in the disposition of the storage device (s) on the carriage. This diversity arises from different operational requirements in which limitations of space within the host machine, both in shape and size, the number of storage devices required and the position of the source and/or the receiver can vary enormously.

For example, Figure 7 shows a set of storage devices 1 grouped in a flexibly articulated closed loop 16 in which the storage devices 1 are akin to the links of a chain or the carriages of a train. Within the confines of the host machine, the loop 16 can be of any length or shape, open or closed, as determined by a path or track 17 along which the storage devices 1 are guided. It is also possible for the storage devices 1 not to be linked to one another but to shunt one another along the track 17 or to be movable independently along the track 17 in the manner of individual trains.

This raises the further possibility of having multiple, branching tracks and means akin to points between the tracks for steering storage devices 1 onto an appropriate track to reach a desired destination within the host machine, such as the banknote path 15 of the validator 14.

The embodiment of Figure 8 is a simpler arrangement in which a set of storage devices 1 are equi-angularly spaced around the circumference of a circular carousel or drum 18. The slot 4 of each storage device is angled with respect to the diameter of the drum 18 on which that storage device 1 lies. Under control of suitable electronics, the drum 18 can be indexed in appropriate angular steps to bring a desired storage device 1 into alignment with the banknote path 15 of the validator 14 when the storage device 1 is required to receive or dispense a banknote. The embodiment of

Figure 9 is still simpler in that a set of storage devices 1 is disposed in-line in a rectilinear array 19 that can simply be moved stepwise in a straight line, namely up and down with reference to Figure 9, to bring the appropriate storage device 1 into registration and communication with the banknote path 15 of the validator 14.

Both the drum 18 of Figure 8 and the rectilinear array 19 of Figure 9 are apt to be embodied in removable cassette form for easy maintenance and servicing of a host machine to which they are fitted. The cassette can include or be attached to other banknote handling mechanisms such as a stacker, a validator and entry and payout paths, as will be explained later with reference to Figure 11.

Turning for now to Figure 10, this illustrates how sets of storage devices 1 can themselves be grouped to form a large and very flexible cache. Here, each set of storage devices is a drum 18 as illustrated in Figure 8 and there are four such drums 18 in an array that may be described with equal accuracy as a square array or a circular array. There is a single entry point to the cache in the form of a validator 14 whose banknote path 15 communicates with one of the drums 18A, but each drum 18 is associated with its own exit point 20 to another banknote mechanism or store (not shown), for example to a respective stacker or cashbox that is dedicated to a particular denomination of banknote.

Significantly, the grouped array of drums 18 also enables banknotes to be transferred from one drum 18 to another neighbouring drum 18, when a storage device 1 of one drum 18 is moved into alignment, registration and communication with an opposing storage device 1 of a neighbouring drum 18. It will be noted in this respect that each drum 18 has two such neighbours in this square array, as would a triangular array of three drums 18 or any other circular or otherwise looped array or five or more drums 18, although even more neighbouring drums would be possible in a hexagonal array of drums 18 disposed around an identical central drum 18. A further benefit of the illustrated array involving neighbouring drums 18 is that the slots 4 of communicating storage devices 1 complement one another, in that their equal opposite angles define a straight banknote path between the respective co-operating slots 4.

The facility for transferring banknotes between different storage devices 1, whether they are grouped in sets or otherwise, means that banknotes can be routed within the cache to any appropriate destination in the host machine. Mention has already been made of separate stacks according to denomination, but with suitable control programming it is also possible to shift banknote resources within the cache so as to be optimally ready for expected demands. For example, it may be deemed appropriate to have a relatively large number of empty chambers 3 on the drum 18 that is fed by the validator 14, so as to be ready to receive however many notes a user might normally wish to insert into the host machine. It would also be useful to maintain a good mix of different banknote denominations on each neighbouring drum 18 so that if a note has to be fetched for payment of change to the user, it will not take long to do so. Conversely, in a gaming machine that pays out prizes using only one particular denomination of banknote, a drum 18 that communicates with a prize payout mechanism would advantageously contain mainly banknotes of that denomination.

Nevertheless, it would in any event be advantageous to maintain at least one empty chamber 3 on each drum 18 so that every drum 18 always has space to receive a banknote from its neighbours before passing that banknote on to an appropriate destination, such as a stacker.

It is envisaged that tracking software would track the location of each and every banknote in the host machine, so as to know exactly what denomination of banknote is where and to plot the path of any banknote through the cache to its desired destination.

Whilst Figure 10 shows a group of the drums 18 illustrated in Figure 8, it will be evident to the skilled reader that other set formats such as those of Figure 7 or Figure 9 could be used instead and that the formats could be mixed within a group of sets so that, for example, a loop 16 as shown in Figure 7 communicates with a drum 18 as shown in Figure 8 and also with a rectilinear array 19 as shown in Figure 9.

Referring finally to Figure 11 of the drawings, a practical embodiment of the invention takes the form of a cassette 21 that, when empty, can be fitted within the host machine as a direct swap for a counterpart cassette 21 that is already full of banknotes or otherwise needs servicing. The cassette 21 is elongate and generally

cuboidal, and is divided into four main functional zones, namely a set of storage devices 1 arranged on a carousel 22 that fills one end of the cassette 21, a banknote stack 23 that occupies much of the remainder of the length of the cassette 21, and broadly parallel banknote entry and payout paths 24,25 that lie beside and run parallel to the length of the note stack 23. The carousel 22 communicates directly with each of the stack 23, the entry path 24 and the payout path 25, for which purpose their respective entry/exit apertures 26,27,28 are angularly spaced around the carousel 22.

In turn, the stack 23, the entry path 24 and the payout path 25 can communicate with each other but only via the carousel 22, which is responsible for routing banknotes between them as well as providing cache storage of the banknotes that it contains.

In use, a validated banknote entering the cassette along the entry path 24 is driven by a sequence of rollers 29 to the carousel 22, whereupon it is taken up by an empty storage device 1 aligned with the aperture 27 of the entry path 24 as described in detail previously. The carousel 22 can then index to whatever other angular position may be required for other operations, notably to align another empty storage device 1 with the aperture 27 of the entry path 24 so as to be ready to receive another banknote.

However, if a particular denomination of banknote-or indeed a particular banknote- is requested for refund, the carousel 22 is indexed to bring the appropriate full storage chamber 1 into alignment with the aperture 28 of the payout path 25, whereupon that banknote is ejected from the storage device 1 into the payout path 25, which conveys the banknote to the user.

Refunds aside, a validated banknote can be held in the carousel 22 for as long as it is needed for cache purposes. If required to pay change or a prize, the banknote can be ejected via the payout path 25 in the same manner as a refund. Eventually, however, it may be that sufficient other banknotes of that denomination are cached in the carousel 22, in which case the carousel 22 can be indexed until the appropriate storage device 1 is aligned with the entry aperture 26 to the stack 23, whereupon that banknote is ejected from the storage device 1 and then stacked by stacking means akin to those described in our aforementioned European Patent Application No. 98307086.3. This indexing, ejection and stacking operation can be repeated for each full storage chamber 1 in turn if it is desired to empty the carousel 22 into the stack 23 when

servicing the host machine, or the carousel 22 can be removed with the rest of the cassette 21 and replaced by another cassette 21 that includes a fresh carousel 22.

Validation means can be integrated into the entry path 24, in which case a rejected, non-validated banknote can be returned to the user by being reversed back up the entry path 24 without ever reaching the carousel 22. Alternatively, separate validation means can be situated upstream of the entry path 24, so that only validated banknotes reach the entry path 24.

Although not shown in Figure 11, it would be possible to define other apertures at appropriate angular locations around the carousel 22 for interfacing with other banknote-handling mechanisms, notably other sets of cache storage devices 1 as outlined above with reference to Figure 10.

Many other variations are possible within the inventive concept. For example, if it is desired to avoid the frictional effects of sliding contact between the roller 6 and the chamber wall 3 in the storage device 1 of Figures 1 to 4, that device 1 could be adapted to work without direct contact between the roller 6 and the chamber wall 3.

Instead, there could be extremely small clearance between the roller 6 and the chamber wall 3 at their closest approach, no wider than the thickness of a banknote 5, so that the banknote 5 is assuredly gripped between the roller 6 and the chamber wall 3 in such a way that the roller 6, when turning, forces the banknote 5 to slide around the chamber wall 3.

Also, in a broad sense, the invention is not limited to a roller 6 within a chamber 3, although such a roller 6 is currently preferred for its elegant combination of drive, guide and support functions. For example, drive means outside the chamber 3, such as a co-operating pair of drive rollers in the slot 4, could be used to push a banknote 5 into the chamber 3 and to pull the banknote 5 out of the chamber 3, provided always that an end portion of the banknote 5 stays outside the chamber 3 in the slot 4, where it can be gripped by the drive rollers. Indeed, reliance can be placed solely upon the curvature of the chamber wall 3 and its relationship with the slot 4 to impart a desirable curvature to a banknote 5 stored within. It could even be left to chance as to how a banknote 5 collapses into the chamber 3, for example not necessarily by coiling

but perhaps by random longitudinal buckling that retains a straight cross-section, provided always that the banknote 5 can be withdrawn from the chamber 3 in a reasonably flat and crease-free state. Nevertheless, coiling is much preferred for its optimally compact and crease-free storage, important in typical applications where space is very much at a premium.

Nor is the invention limited to having a substantially continuous chamber 3 around the roller 6. Whilst it is preferred that the chamber wall 3 defines a continuous smoothly curved surface around the roller 6 for coiling the banknote 5 and for supporting the banknote 5 once coiled, one or more other curved members such as loops or guides of wire or plastics could substitute for the curved wall of the chamber 3, which could for example take the appearance of an open basket. It is even possible for there to be no structure surrounding the roller 6 at all, it being left largely or entirely to the roller6 to grip and support the banknote 5 in a coiled configuration by means such as the retaining slot 12 of Figure 6.

Many other variations will be apparent to the skilled reader within the inventive concept. Accordingly, reference is to be made to the accompanying claims and other conceptual statements herein rather than to the foregoing specific description as indicating the scope of the invention.