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(11) | EP 0 385 651 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Sheet stacking assembly |
| (57) A sheet stacking assembly comprising a sheet stacking device including a carrier
member (1) onto which sheets are stacked, a reciprocal guide member (60) which moves
between a sheet accepting position in which a sheet can be delivered between the guide
and carrier members and a stack holding position in which sheets are held in a stack
on the carrier member by the guide member, and a motor (10) for controlling movement
of the guide member. A transport (16) supplies sheets into the space between the carrier
member and the assembly further comprising the guide member and sensing means (11)
for sensing the passage of a sheet through the transport means, the control means
of the sheet stacking device being responsive to signals from the sensing means to
cause the guide member to move to the sheet accepting position when the arrival of
a sheet is sensed. |
[0001] The invention relates to a sheet stacking assembly and a method of operating such an assembly.
[0002] Various sheet stacking assemblies have been developed in the past of which one of the most common makes use of the so-called stacker wheel. An example is shown in EP-A-0211814. This consists of a circular member having a number of radially outwardly opening slots into each of which a sheet is fed by a transport system, the sheet being carried upon rotation of the wheel from a sheet receiving position to a sheet stacking position in which the sheet is stripped out of the slot by a stripper plate and falls onto a stacker plate. One of the problems with devices of this type is that it is very important to synchronise the arrival of a sheet at the device with a slot in the wheel since otherwise the leading edge of the sheet may not enter the slot cleanly leading to jamming or incorrect feed. Another problem is the bulk of such assemblies, while a further problem is the loose manner in which sheets are held by the stacker wheel.
[0003] In accordance with one aspect of the present invention, a sheet stacking assembly comprises a sheet stacking device including a carrier member onto which sheets are stacked, a reciprocal guide member which moves between a sheet accepting position in which a sheet can be delivered between the guide and carrier members and a stack holding position in which sheets are held in a stack on the carrier member by the guide member, and control means for controlling movement of the guide member; transport means for supplying sheets into the space between the carrier member and the guide member; and sensing means for sensing the passage of a sheet through the transport means, the control means of the sheet stacking device being responsive to signals from the sensing means to cause the guide member to move to the sheet accepting position when the arrival of a sheet is sensed.
[0004] This invention avoids the need for the rotating stacker wheel previously used and has the advantages that accurate synchronisation between the arrival speed of a sheet and the motion of the guide member is not necessary, and that the device is more compact than a stacker wheel. Preferably, the transport means is adapted to grip sheets while they are supplied into the space between the carrier member and the guide member. Thus, sheets are fed directly to the stacking device in a controlled manner avoiding the looseness problems of stacker wheels.
[0005] Typically, the transport means will be provided by cooperating belts between which sheets are gripped, although a vacuum based system could be used.
[0006] Preferably, the guide member is mounted for pivotal movement between the stack holding and sheet accepting positions.
[0007] The guide member may comprise a plate but this can cause sheets to stick to it due to the generation of a vacuum upon rapid movement of the plate. Preferably, therefore, the guide member comprises a set of tines or elongate elements. This arrangement not only reduces the inertia of the member but also avoids the sticking problem.
[0008] It is particularly convenient if the guide member is made from an electrically conductive material, such as carbon fibres, since this will assist in reducing the static electricity generated during sheet movement thus also reducing the tendency of sheets to stick, while the strong but light material will minimise inertia. This is particularly important in the case of banknote handling.
[0009] Preferably, the carrier member is movable relative to the guide member from a start position towards which it is biased so that the carrier member remains substantially parallel with the guide member when the guide member is in the stack holding position. If this movement was not possible, the increasing size of the stack on the carrier member would prevent the guide member from moving to a position in which the stack was securely held which, in the case of large stacks, would be undesirable. By allowing movement of the carrier so that the carrier and guide members are maintained substantially parallel, the sheet stack is always securely held when the guide member is in the stack holding position.
[0011] The carrier member may be biased towards its start position by any conventional biasing means such as a compression spring. Preferably, however, damping means is provided to damp the action of the biasing means. This damping action prevents the carrier member from springing back to its start position whenever the guide member moves to the sheet accepting position. This prevents oscillation of the carrier member which would be undesirable.
[0013] Where the carrier member is formed of a pair of plates, the damping means preferably includes a T-shaped member which engages both plates. Typically, the T-shaped member is coupled to a piston of a piston/cylinder arrangement. In this case, the T-shaped member is preferably offset from the axis of the piston/cylinder to prevent rotation of the member.
[0014] In the preferred arrangement, the carrier guide members are pivotable together to present a stack of sheets in a selected manner.
[0015] The control means preferably comprises a reciprocating motor and a coupling member extending between the motor and the guide member such that the reciprocating motion of the motor is coupled with the guide member.
[0016] The coupling member could be provided by a solid coupling rod or the like but preferably the control means further comprises means to accommodate a lesser degree of movement of a guide member from the sheet accepting position to the stack holding position than in the opposite direction. This accommodation means may comprise a spring loop incorporated in the coupling member.
[0017] In accordance with a second aspect of the present invention, a method of operating a sheet stacking assembly comprising a sheet stacking device including a carrier member onto which sheets are stacked, a reciprocal guide member which moves between a sheet accepting position in which a sheet can be delivered between the guide and carrier members and a stack holding position in which sheets are held in a stack on the carrier member by the guide member, and control means for controlling movement of the guide member; comprises sensing the arrival of each sheet at the stacking device; and, upon sensing a sheet, causing the guide member to move to the sheet accepting position and thereafter causing the guide member to move to the stack holding position whereby the sheet is stacked on the carrier member.
[0018] With this arrangement, the guide member is normally held against the stack but upon the arrival of a sheet, the guide member will move to the sheet accepting position. The guide member can be arranged to return to the stack holding position a fixed time after moving to the sheet accepting position or when the presence of a sheet between the carrier and guide members is sensed.
[0019] The invention is applicable to any form of sheet feeding system but is particularly useful with banknote handling apparatus.
[0020] Some examples of sheet stacking devices according to the invention will now be described with reference to the accompanying drawings, in which:-
Figure 1 is a schematic, perspective view of one example of the device with the tines in the sheet accepting position;
Figure 2 is similar to Figure 1 but with the tines in the stack holding position;
Figure 3 is a schematic, side elevation with some parts cut away;
Figure 4 is a view similar to Figure 3 but with the note support plate in a different position;
Figure 5 illustrates a first modified form of damper;
Figure 6 illustrates a second modified form of damper;
Figure 7 illustrates the bristles shown in Figure 1 in more detail;
Figure 8 illustrates the coupling between the motor and the tines in more detail;
Figure 9 is a plan of the spring coil shown in Figure 8; and,
Figure 10 is a perspective, cut-away view of a second example of the device.
[0021] The device shown in Figure 1 comprises a U-shaped note plate 1 having a slot 2. As shown in Figure 2, the upper end of the note plate 1 is pivoted to a frame (not shown) by a pivot 3 so that its lower end can pivot about the pivot 3. The lower end of the plate 1 has a laterally extending foot 4 which engages a stop 5 when the support plate 1 is in its initial position (Figure 3).
[0022] A guide member 60 is formed by a set of six carbon fibre tines 6. The tines are fixed to a shaft 7 which is supported by respective frame members, one of which 8 is shown in Figures 1 and 2. The shaft 7 can rotate so that the tines 6 pivot between a sheet accepting position shown in Figure 1 and a stack holding position shown in Figure 2. The tines extend through respective slots 9 in the foot 4 of the note plate 1.
[0023] The position of the shaft 7 is controlled by a motor 10 mounted to the frame member 8 and controlled by signals from a sensor 11 (to be described below) so that a crank arm 12 connected to the motor can take up one of two positions. The crank arm 12 is connected via a crank rod 13 to a crank arm 14 mounted non-rotatably to the shaft 7.
[0024] Mounted generally above the plate 1 and tines 6 is a set of nylon bristles 15. As can be seen from Figures 1 and 7 the bristles extend between an adjacent pair of the tines 6.
[0025] In operation, banknotes to be stacked are fed along a transport system comprising rollers and belts part of which 16 is shown in Figure 7. A typical feed rate is 800 mm/sec. The sensor 11, which is aligned with a light source 11′, is positioned to detect the arrival of a banknote in the part 16 of the transport and issues a signal to the motor 10. This causes the motor 10 to rotate the crank arm 12 and hence the arm 14 to move the tines 6 from the position shown in Figure 2 to the sheet accepting position shown in Figure 1. This rotation takes about 20 ms and is completed before the arriving note begins to leave the transport. A banknote 17 is then delivered by the transport 16 into the space defined between the tine 6 and the plate 1, the note entering underneath the set of bristles 15 as indicated by an arrow 18 in Figure 7 and falling under gravity until it engages the foot 4. Operation of the motor 10 is timed such that the return stroke occurs at a predetermined time interval after the note has cleared the transport 16, sensed by a suitably placed sensor 71 aligned with a light source 70. The return stroke of the motor 10 causes the crank 12 to rotate in an opposite direction so as to bring the tines 6 towards the note plate 1 in a period of about 20ms. During this movement, the tines guide or push the note 17 towards the note plate 1 and, as can be seen in Figure 7, the bristles 15 are displaced upwardly during this motion until they clear the note 17 at which point the bristles flex downwardly. The bristles 15 thus act to prevent any possibility of the note 17 returning to its initial position.
[0026] When the tines 6 have reached the position shown in Figure 3, they are then held in this position by continued actuation of the motor 10 for a recovery period of about 15ms to allow the note to settle and sandwich the note 17 against the note plate 1. When the next note is sensed by the sensor 11 this process is repeated so that a stack of notes is built up as shown, for example, in Figure 4.
[0027] As has previously been mentioned, the note plate 1 itself is pivoted at 3. The note plate 1 is urged towards the position shown in Figure 3 by a rod 19 connected to a piston 20 in a dash pot 21. A compression spring 22 is mounted in the dash pot 21 to urge the piston towards the note plate 1 while the dash pot is filled with oil to damp movement of the piston 20. An orifice 23 is provided in the piston 20 through which oil can pass. In the initial position shown in Figure 3, the compression spring 22 urges the note plate 1 into its start position in which the foot 4 engages the stop 5.
[0028] During operation, the force with which the tines 6 engage the plate 1 (via the stack of notes) causes the plate 1 to pivot in a clockwise direction as seen in Figure 3 about the pivot 3 against the bias of the compression spring 22. This will cause the note plate 1 to take up an orientation which is generally parallel with the orientation of the tines 6 (as shown in Figure 4). When the next note is to be accepted, the tines 6 will be rotated in a clockwise direction (Figure 4) thus removing the urging force from the note plate 1. The note plate 1 will thus be urged under the influence of the compression spring 22 towards its start position. However, due to the damping action of the dash pot, this return movement of the note plate 1 will be slow relative to the time during which the tines 6 move to the sheet accepting position and back to the stack holding position so that in general the note plate 1 will not have moved fully back to the position shown in Figure 3 by the time the tines 6 return to the stack holding position. Thus, a significant oscillation of the note plate 1 is prevented.
[0029] Initially, the position of the stop 5 is adjusted so that the tines 6 lie flat on the note plate 1. This ensures that when the first note is brought over by the tines, it is flattened and held in a positive pinch to allow all energy it may have to be dissipated. By permitting the expansion movement of the note plate 1, the flat contact of the tines against the notes already in storage is maintained. It is this flat contact of one note on top of the next which makes it possible to squeeze out any air film and "stun" the note against the rest of the stack.
[0030] Figure 5 illustrates a modified form of the device in which the dash pot 21 shown in Figures 3 and 4 has been replaced by a rotary dash pot 24 which dampens movement of an L-shaped arm 25 the free end of which engages the note plate 1 and which is urged towards the note plate 1 by a tension spring 26.
[0031] Figure 6 illustrates a modified dash pot 21′ in which in addition to the orifice 23 a check valve 27 is provided. This generates a dual rate damper in which clockwise movement of the note plate 1 under the influence of the tines 6 is relatively easy while return or anti-clockwise movement is much slower.
[0032] The connecting rod 13 joining the drive motor 10 with the shaft 7 has been made with a spring loop 28. This is equivalent to inserting a short tension spring into the connecting rod. The motor 10 can push the tine shaft 7 over with the connecting rod 13 acting as a solid piece of wire since the spring coil 28 is normally closed up with no load and therefore acts as a solid rod. This ensures that the tines 6 reach their desired position with no time lag.
[0033] Upon returning to the note stack, the tines 6 can accommodate the change in angle made due to the increase in thickness of notes in the stack since the spring coil 28 opens up. This enables the motor 10 always to regain its original position without stalling. The motor torque is higher than the force supplied by the opening spring loop 28, which can thus be overcome by the motor.
[0034] The stack of notes once completed can then be handled in any conventional manner and conventionally is transported to an outlet opening. The device is particularly suitable, however, for use in a dispensing system of the type described in our copending European patent application of even date entitled "Sheet Stacking Apparatus" (Agents Ref: 30/2818/02) claiming priority from British Patent Application No. 8904566.0 incorporated herein by reference.
[0035] A second example of a sheet stacking device is illustrated in Figure 10 where a solenoid replaces the stepper motor. The device is positioned between a pair of side plates 100 which are fixed relative to each other by aluminium tie bars such as tie bar 102, while a pair of side plates 103, held by a tie bar 101, are pivoted between the side plates 100 about the axis of a shaft 104.
[0036] Two note plates 105 are pivoted to the side plates 103 via nylon pivot pads 106 riveted to the note plates 105 which can pivot freely about pivots 107 fixed to the plates 103. The note plates 105 are urged to the position shown in Figure 10 by a piston/cylinder damping system 108 fixed to the side plates 100 (by means not shown) and having a piston connected to a T-shaped push bar 109 which is urged against the underside of the note plates 105. This is similar to the piston 20/dash pot 21 arrangement described earlier.
[0037] A set of six carbon fibre tines 110 overlie the note plates 105 and are connected to the shaft 104 so that rotation of the shaft 104 will cause the tines 110 to pivot between the position shown in Figure 10 and a note receiving position similar to that shown in Figure 1. The position of the tines 110 is controlled by an electrically operated solenoid 111 mounted to one of the side plates 103 and having a rod 112 coupled with a bracket 113 pivoted to the side plate 103 and coupled via a rod 114 to a bracket 115 fixed to the shaft 104. Linear movement of the rod 114 causes rotation of the shaft 104.
[0038] In operation, the stacking device of Figure 10 is similar to that of the previous example. Thus, when the arrival of a note is sensed, the solenoid 111 is activated to retract the piston rod 112 to cause the tines 110 to rotate away from the note plates 105 to their note receiving position. The note then enters between the tines and the note plates and as soon as the note leaves the upstream transport system, the solenoid 111 is deenergised to allow the piston 112 to be pulled back out, under the influence of a torsion spring 120, which causes rotation of the tines 110 to the position shown in Figure 10.
1. A sheet stacking assembly comprising a sheet stacking device including a carrier
member (1) onto which sheets are stacked, a reciprocal guide member (60) which moves
between a sheet accepting position in which a sheet can be delivered between the guide
and carrier members and a stack holding position in which sheets are held in a stack
on the carrier member by the guide member, and control means (10) for controlling
movement of the guide member; transport means (16) for supplying sheets into the space
between the carrier member and the guide member; and sensing means (11) for sensing
the passage of a sheet through the transport means, the control means of the sheet
stacking device being responsive to signals from the sensing means to cause the guide
member to move to the sheet accepting position when the arrival of a sheet is sensed.
2. An assembly according to claim 1, wherein the guide member (60) is mounted for
pivotal movement between the stack holding and sheet accepting positions.
3. An assembly according to claim 1 or claim 2, wherein the guide member (60) comprises
a set of tines (6) or elongate elements.
4. An assembly according to any of the preceding claims, wherein the guide member
(60) is made from an electrically conductive material.
5. An assembly according to any of the preceding claims, wherein the carrier member
(1) is movable relative to the guide member (60) from a start position towards which
it is biased so that the carrier member remains substantially parallel with. the guide
member when the guide member is in the stack holding position.
6. An assembly according to claim 5, wherein the carrier member (1) is pivoted to
a support.
7. An assembly according to claim 6, when dependant on claim 2, wherein the carrier
member (14) is pivoted to the support at a position (3) remote from the pivotal mounting
(7) of the guide member (60).
8. An assembly according to any of claims 5 to 7, further comprising damping means
(19-23) to damp the action of the bias.
9. An assembly according to claim 8, wherein the carrier member (1) is formed of a
pair of plates, and wherein the damping means includes a T-shaped member (109) which
engages both plates.
10. An assembly according to any of the preceding claims, wherein the carrier member
(1) has an L-shaped section, wherein sheets locate against the short arm (4) of the
"L" during operation.
11. An assembly according to any of the preceding claims, wherein the control means
comprises a reciprocating motor (10) and a coupling member (13) extending between
the motor and the guide member (60) such that the reciprocating motion of the motor
is coupled with the guide member.
12. An assembly according to claim 11, wherein the control means further comprises
means to accommodate a lesser degree of movement of the guide member from the sheet
accepting position to the stack holding position than in the opposite direction.
13. An assembly according to claim 12, wherein the accommodation means comprises a
spring loop incorporated in the coupling member (13).
14. An assembly according to any of the preceding claims, wherein the transport means
is adapted to grip sheets while they are supplied into the space between the carrier
member and the guide member.
15. A method of operating a sheet stacking assembly comprising a sheet stacking device
including a carrier member (1) onto which sheets are stacked, a reciprocal guide member
(60) which moves between a sheet accepting position in which a sheet can be delivered
between the guide and carrier members and a stack holding position in which sheets
are held in a stack on the carrier member by the guide member, and control means (10)
for controlling movement of the guide member; the method comprising sensing the arrival
of each sheet at the stacking device; and, upon sensing a sheet, causing the guide
member to move to the sheet accepting position and thereafter causing the guide member
to move to the stack holding position whereby the sheet is stacked on the carrier
member.
16. A method according to claim 15, wherein the assembly is constructed in accordance
with any of claims 1 to 14.