Mechanisms for banding stacks of sheets are known to exist. For example US 3842572 describes a combined document stacking and banding machine in which the stack of documents formed in the banding station in front of a continuous banding strip, is then urged directly from the stack forming position across the path of a continuous banding strip extending across the banding station such that a portion of the strip is deflected out of its path around the front of the stack, the strip is then reunited along the path at the rear of the stack such that portions of the strip overlap and bonding of the overlapped portion is undertaken. The bonding means is such that the strip is at least partially severed into a pair of joined edges such that the banded stack of sheets can be detached from the strip without destroying the continuity of the strip. The problems with this arrangement are that it is not particularly tolerant to variations in thickness of the stack of sheets, having to be set up for the minimum anticipated stack thickness which then causes deformation of the stack sheets if the stack thickness exceeds an upper limit and it requires use of a strip material and a bonding technique reliably able to provide at the bond the partial severance characteristic described above.

US4539789 describes a banding mechanism in which the stack of sheets is transferred from a lowered backup plate

onto a carriage provided with an auxiliary clamp mechanism to stop the stack collapsing and align the stack as the carriage carrying the stack is moved to the bundling position. The band is wrapped about the stack of sheets by the combined operation of moving the carriage into the bundling position and the rotation of a winder assembly which includes the catcher holding the end of the band.

The band has previously been fed by feed rollers from a roll of tape, into the catcher to then be clamped by the catcher whilst the winder is in a predefined position in the banding cycle. When the carriage has stopped within the bundling position the winder continues to rotate until the catcher is at the band seal position where the stack is further clamped before the band feeder pulls back on the band to tension it about the stack, the heater block is moved towards its tape bonding position whilst the tape stopper is moved to hold the tape against the stack, then the tape is cut, the heater block completes its move to the bonding position and the heat sealing operation is undertaken. This specification further describes means for stamping specified data on the band wound around the stack and means for ejecting the banded stack from the carrier as the carrier is moved beyond and the back to its start position.

A similar mechanism, with embellishments, is described in EP-0540134-A2, US4126983 and US4111116, which predate US4539789, again describing bundling mechanisms for wrapping the tape around the stack of sheets. However, the specifications describe a mechanism for inserting the initially free end of the band in between sheets of the stack at the start of the wrapping cycle.

The banding means whereby the initially free end of the banding tape is, at the end of the banding cycle sandwiched between sheets of the stack is also described in US4374463. This specification, however, describes the use of a former consisting of two unit sheet stack guide members and a centrally positioned tape guide member all

mounted on a rotatable disc, being used to pre-form in a circle loops of tape into which the stack of sheets is inserted, such that approximately one half of the stack is on each side of the tape guide. The given length of tape, fed by feeding rollers forming part of a roller receiving member, is guided into the tape guide, after which the roller receiving member is returned'to its original position before rotation of the former, whilst the tape is again fed by the feeding rollers, to wrap the tape around the edges of the two unit sheet stack guide members.

Rotation of the former and the tape feeding is stopped at a position in which, by an operation including the use of an intermediate mechanism, the sheet stack is pushed into the formed circle of tape, guided by the unit sheet stack guide members and split by the tape guide. By a sequence of withdrawing the former from within the circle of tape surrounding the stack, tensioning the tape, clamping the stack, pasting the tape, squeezing the tape to itself and cutting the tape, the banding operation is completed. The problems with the banding mechanism described in this specification are that it is complex, uses more tape than is necessary to retain the stack, is likely with its mechanism for getting the free end of the tape into the stack to cause damage to the sheets within the stack, and is unreliable.

In accordance with a first aspect of the present invention, a method of banding a stack of sheets comprises pre-forming a loop of band material; inserting a stack of sheets into the loop, the loop being preformed to a size such that opposite ends of the loop extend beyond the stack; bringing the opposite ends of the loop together; and bonding the opposite ends, whereby the stack is securely held in the closed band.

In this aspect of the invention, the loop is preformed in order to provide the"right"tension about the banded stack. The length of band to be preferred can be based on

the determined condition of the notes as well as the known number and size of the notes to be banded.

In accordance with a second aspect of the present invention, a method of banding a stack of sheets comprises locating a band support carrying a web of band material adjacent a band gripper with a free end of the web projecting beyond the support; causing the free end of the web to be held securely by the band gripper; moving the band support away from the band gripper and supplying further band material to the support whereby a length of band material extends across a gap defined between the band gripper and the band support; supplying a stack of sheets into the gap so that the band extends about the stack; bonding the ends of the band together so that the stack is held securely in the closed band; and separating the bonded section of the band from the remainder of the web.

This provides a simple way of pre-feeding the free end of the band.

We also provide apparatus for carrying out the methods of the invention.

The sheet stack banding methods and apparatus can either form part of a free standing stack banding module having its own independent control system, or may form part of a larger system designed to automatically process security type documents.

An example of apparatus and a method according to the present invention will now be described with reference to the accompanying drawings, in which:- Figure 1 is a side view of a sheet stack bander module; Figure 2 is a part sectional side view of a sheet stack bander shown by Figure 1 showing the area concerned with the feeding of the tape, its being sealed to form a complete band about the sheet stack and its cutting once the complete band has been formed but with the tape omitted;

Figure 2A is a cross sectional view of the lower anvil shown in Figure 2 in the direction AA-AA; Figure 3 is an end view of a sheet stack bander module in the direction A, with the spine and stack gripper mechanism removed for clarity; Figure 4A is a side view of the lower anvil assembly, viewed in direction B on Figure 3; Figure 4B is an end view of the lower anvil assembly; Figure 5A is a side view of the lower and upper anvil assemblies, viewed in direction B on Figure 3, showing the position just before the stack to be banded is moved into the banding position; Figure 5B is a side view of the lower and upper anvil assemblies, viewed in direction B on Figure 3, showing the position as the stack reaches the banding position; Figure 6 is a side view of the lower and upper anvil assemblies, viewed in direction B on Figure 3, showing the position as the formed band is cut; and, Figures 7A-7D are side views of the upper anvil assembly in various positions, viewed in direction B on Figure 3.

The sheet stack bander assembly 1, as shown in Figures 1 to 3, comprises a spine 10 on which are mounted a moveable sheet stack transport arrangement 20, of which only clamp fingers 21,22, a driving timing belt 23 and a drive pulley 24 are shown in figure 2, and a rotatably mounted tape spool arrangement 30. The sheet stack transport arrangement 20 is movably mounted to a track 25 which is in turn mounted to the spine 10. The sheet stack transport is moved along the drive track under the control of a bander control system (not shown), a drive motor (not shown), the driving timing belt 23 and a drive pulley 24.

Clamp fingers 21,22 are opened and closed through an intermediate linkage arrangement (not shown) by the linear motor 27 and are also operated under the control of the bander control system.

A front plate assembly 100 is attached to the front edge 11 of spine 10 while, spaced away from the spine, is a support plate assembly 40. The support plate assembly 40 consists of support plate 41 on which are mounted band tape guide 50, which is also attached at one end to spine 10, yoke assemble 60 attached to the support plate by screws (not shown), ink tape and print head support 42, fixed band guide 43 and band tension roller assembly 70 which is rotatably mounted on shaft 44 extending between support plate 41 and mounting block 110 attached to the face of front support plate 101. Band tension roller assembly 70 consists of an arm 71 rotatably mounted about shaft 44 and a roller 72 rotatably mounted on a shaft 73 fixed to the arm 71. The assembly 70 is biassed by a torsional spring 74 in a clockwise direction about shaft 44 such that roller 72 contacts one surface of the band 3 passing between the roller 72 and a tape drive roller 65 of the yoke assembly 60. Tape drive roller 65 is non-rotatably mounted on a drive shaft 63 rotatably mounted between a yoke 61 and a removable support 62 mounted to the yoke by screw 64, the shaft 63 being rotated by a timing belt (not shown) locally meshing with a timing belt pulley (not shown) non-rotatably mounted to the shaft where it extends rearwards through a clearance hole in the support plate 41. This timing belt (not shown) is controllably driven by a motor 45 mounted on the rear face of the support plate 41. Also forming part of the yoke assembly 60 is a print roller assembly 80 which consists of print roller 82 rotatably mounted on a shaft 83 fixed in a link arm 81 rotatably mounted on a shaft 66 also mounted between yoke 61 and the removable support 62.

Print roller assembly 80 is actuated to be moved to a band printing position (shown in figure) from a normal position to which it is spring biassed, by a solenoid (not shown).

Also forming part of the yoke assembly 60 are band guides 67,68.

Front support plate assembly 100 consists, as shown in Figure 3, of the front support plate 101 having a profiled

opening 105 through which pre-stacked sheets gripped within a gripper mechanism are pushed towards the viewer, three side plates 108,109,111 and mounted between side plates 108,109, upper anvil support assembly 200. On the rear face of the front support plate 101, as seen in Figure 3, is mounted, as can be seen in Figure 2, on a support 102, a lower anvil linear drive assembly 130. A lower anvil support plate assembly 140 is slidably mounted between a pair of laterally spaced guide blocks 103 (only one shown) at the lower end and cut out 105 in the support plate 101 having edges 106,107 locating in grooves 147 in the side edges of the lower anvil guide plate 146, as shown in Figure 2A.

The assembly 140, Figure 4, is made up of the lower anvil plate 141 having side members 142,143 attached by screws 144 to the bracket 145 which is slidably located within the guide blocks 103 and, on an extension which passes through a clearance groove on the underside of support 102, torsion spring 175 mounted about a pillar 176.

Attached to the top of plate 141 is the lower anvil guide plate 146 to which the profiled lower anvil 149, having cutter slot 153, is attached by screws 148, and stack stripper 170.

Resting on the surface of plate 141 is a tape guide plate 160 which slidably locates at its upper end on the face of lower anvil guide plate 146 within the band slot 150 in the lower anvil 149. At its lower end, which is formed 161 at right angles to the surface 162, the plate 160 is mounted on pillars 163,164 which pass through clearance slots in the bracket 145, and are fixed to a collar 134 which itself is fixed to a drive bush 135 of the linear drive assembly 130. Holes 151,165 in the bracket 145 and surface 161 respectively, are clearance holes about a linear drive screw 132. A compression spring 152 between the collar 134 and the bracket 145 provides the drive to bracket 145 when the drive bush is moved in the upwards direction, the continued movement of the drive bush moving

the collar 134 and hence the tape guide plate, against the compression force of the spring 152 when movement of the bracket 145 is stopped when the lower anvil comes into contact with the upper anvil, and, when the drive bush is moved in the downwards direction ensures bracket 145 and hence the lower anvil commences downwards movement as soon as the surface 161 meets the bracket 145.

Linear drive assembly 130 is a commercially available drive arrangement consisting of a drive bush 135 on lead screw 132 which is rotated by a stepping motor 131. The action of the linear drive is assisted by the spring 175, the ends 177,178 of which react against pillars suitably mounted on the front support plate 101.

As is show in Figures 5 to 7, upper anvil support assembly 200 comprises a plate 201 to which are mounted left and right support plates 202 (only one shown) both of which have a shaped slot 204 having a section 205 parallel with the mounting edge of the support plate and a section 206 angled from section 205. Mounted between the plates 202 is a shaft 207. Pivoting on shaft 207, between the plates 202 is an upper anvil drive assembly 210 comprising of a drive motor mounting plate 211, a base plate 212, a link pivot plate 213 and a cutter carriage assembly 300 made up of a plate 301 mounted to a bearing block 302 attached to a bearing block 303. The block 303 is attached to the driven collar 214 of a linear drive assembly 215 the drive motor 216 of which is mounted on the plate 211. A linear drive lead screw 217 is supported in a bush 218 mounted in the link pivot plate 213. Also attached by screws 311 to the cutter carriage assembly plate 301 is a knife block 310 to which a knife 312 is attached by screws 313. The block 310 also mounts a latch pin 314 and, mounted on a pivot 224 in a mounting block 225 attached to the end of the base plate 212, is a clamp 315 which has pivoted to its upper end pivot 316, link 317 which slidably links with pivot 219 on the link pivot plate 213. A spring

220 biases the upper end of clamp 315 away from link pivot plate 213.

A latch 320, has, in the unlatched state, a bearing edge 321 resting on the latch pin 314, a latch position 322 and arm 323 extending through slot 226 in base plate extension 223, is pivoted on pin 324 on the lower end of clamp 315 and is biassed by a extension spring 221 connected between arm 323 and a pin 222 mounted to the base plate extension 223 to cause the latch to act against the latch pin 314. The base plate extension 223 is mounted on an anvil heating block 230 which is mounted to base plate 212. Also mounted on the anvil heating block 230 are anvil heater 231, upper anvil 232 and fixed clamp plate 233.

Extension springs 235 attached to the base plate extension 223 by bracket 234 and the plate 201 bias the upper anvil drive assembly 210 clockwise about the shaft 207. In some Figures guard 250 is not shown.

Mounted to bearing blocks 302,303 are bearings 304, 305, bearings 304 running on the upper surface of the base plate 212 and 305 within the shaped slots 204 in the support plates 202,203.

A typical sheet stack banding cycle is as follows: The start of the banding cycle which is to be described occurs in the period a pre-formed stack of sheets S is lowered on a stacking platform (not shown) into a position in the general area 4 shown in Figure 1, to then be gripped within grippers 21,22 which are controllably moved to transport the gripped stack of sheets into the stack banding position. The banding apparatus is such that the end of the tape band is held within the clamp arrangement 315,233 of the upper anvil support assembly 200 (Figure 7D) and lower anvil support plate assembly 140 is at the position shown in Figure 5A. At this stage, the latch 320 is unlatched and bearings 305 are at the left hand end of the section 205 of slots 204 and base plate 212 substantially parallel with the plate 201.

Under control of the motor 45, the tape drive roller 65 is rotated to feed a predetermined length of the band tape to form a loop of tape 5, Figure 5A, between the lower and upper anvils, the length of tape fed being determined by a tape drive motor control system (not shown) coupled to the motor 45 from parameters based on the condition, for example soiled, mint, or good used, and number and width of the sheets to be banded and required prearranged banded tape tension characteristics.

The control system effecting the forming of the loop of tape may be a"stand alone"system or may be included either partially or fully within the control arrangements of any parent equipment. The control system will typically use either the sheet parameters, the sheet stack parameters, or a combination of both of these, when forming the tape loop. In this case, before commencement of the banding process, the sheet and/or sheet stack parameters are input into the control system.

In one example the parameters may include: a) The height of the sheets to be banded.

This information could be provided from a look-up table containing details of the security document's dimensions, including a nominal thickness; and the type of document (e. g. denomination, print series, country). The information may be provided by a manual operator or it may be determined from automatic analysis of the sheets by the processing equipment. b) The number of sheets contained within the stack. c) The condition of the sheets within the stack to be banded.

As can be appreciated the condition of the sheets can vary from"mint"condition (as printed) through to "rag"condition ; and a stack of such sheets from "brick"condition (comprising sheets in"mint" condition) to a stack of 100% rag sheets. d) The anticipated mix of conditions of the sheets in the stack to be banded.

It is appreciated that, for example, in sorting banknotes to be put back into public circulation from those unsuitable for circulating, the sheet condition accepted as being suitable for re-circulation is adjusted to suit bank service criteria.

The entered parameters can then be used to access look-up tables which provide an estimate of the sheet stack thickness for the given conditions. In this manner the lengths of tape used can be optimised. Known control techniques can be used to cause the required processed length of tape to be formed.

It will however be realised that the control system may operate using any suitable input data if appropriate look-up tables are used.

At approximately the same time as the loop of tape is formed, data concerning the stack of sheets to be banded is printed by the print head onto the face of the tape. Then, whilst the stack of sheets is being gripped within clamp fingers 21,22, during the operation to grip the stack in the area 4 and transport it into the banding position, controllably driven by a motor (not shown) via timing belt 23 and drive pulley 24, motor 216 on the upper anvil assembly is activated to rotate lead screw 217 clockwise as viewed in the direction of the arrow C such that the bush 214 together with the cutter carriage assembly 300 moves to the left. Bearings 305 enter the angled section 206 of slots 204, which causes the upper anvil drive assembly 210 to be lifted to the position shown in Figure 7A by the extension springs 235. This is also the position of the upper anvil support assembly 200 shown in Figure 5A. As can be seen, this provides clearance in the way of the document stack being moved into the preferred tape loop.

The gripped stack of sheets S is transported by the grip means 21,22, between the upper and lower anvil assemblies into the pre-formed loop 5 of band tape to the banding position (Figure 5B).

Motor 216 is then controlled to rotate the lead screw 217 anticlockwise back to the position shown in Figure 7c whilst the motor 131 on the lower anvil linear drive assembly 130 is controllably activated to lift the lower anvil support plate assembly 140 upwards to the lower anvil band forming position 140'shown pictorially by the dotted profile of the stripper fingers 170 in Figure 5. The motor 45 rotates the tape drive roller 65 anticlockwise as seen in Figure 2 to finely adjust the tension of the band about the stack of sheets S (although the tension should be substantially correct because the band was preformed into a loop according to the properties of the stack S so that a desired tension would result). Drive signals to the motor 131 on the lower anvil drive assembly and the motor 45 driving the tape are stopped as the lower and upper anvils 149,233 grip the two layers of tape and the heated upper anvil welds the two layers of tape together to form the band.

Upon completion of the band forming operation, the lead screw 217 is again rotated anticlockwise moving the cutter carriage 300 to the right relative to the rest of the drive assembly 210, causing the cutter 312 to cut the band tape (Figure 7B and Figure 6) as its cutting edge enters the slot 153 in the lower anvil 149, and the latch pin 314 to move along the surface 321 of the latch 320 against the action of extension spring 221. The latch 320 latches when the pin 314 enters latch point 322. Whilst this latter operation takes place, the stack gripper mechanism 21,22 opens before moving back, in the opposite direction to arrow C, into a position to collect the next stack of sheets to be banded, the action causing the sheet stack just banded to be stripped by strippers 170 from the gripper fingers 21,22 and to fall from the stack banding position.

The drive to the lead screw 217 is then reversed to move the cutter carriage assembly 300 to the left causing the cutter to move away from the band tape and, under the

influence of the latched latch, the clamp arm 315 to rotate clockwise about pivot 224 and move away from the fixed clamp 233 whilst tape drive roller 65 is rotated clockwise to feed the now free end of tape. The motor 131 is activated to lift the tape guide plate 160 against the action of spring 152 to position the free end of the tape within the open gap between 315 and 233. Rotation of the tape drive roller 65 is then stopped. The carriage 300 is then moved to the left to cause the latch arm 323 to meet the end of slot 226 in the extension 223 and with further movement of the carriage, the latch to de-latch and the clamp arm to rotate anticlockwise to close the band tape clamp (Figure 7D) and grip the band. The motor 131 is then reversed to cause the tape guide plate 160 to be lowered and a length of the band to extend between the plate 160 and the clamp across the opening 500. Figure 7C shows the upper anvil support plate arrangement at the point in the procedure when the latch arm touches the end of slot 226.