WO2005085109A1

WO2005085109A1 - Sheet diverter

Info

Publication number: WO2005085109A1
Application number: PCT/GB2005/000663
Authority: WO
Inventors: Steven Michael Hosking; Michael Robert Formby
Original assignee: De La Rue International Limited
Priority date: 2004-03-05
Filing date: 2005-02-24
Publication date: 2005-09-15
Also published as: GB0405056D0

Abstract

Apparatus comprising a sheet diverted assembly (2, 3, 4) which is movable between first and second positions so as to divert sheets along corresponding first and second paths. At least one end stop (16) constrains the movement of the sheet diverter assembly within a predefined path, the ends of which correspond to the first and second positions. An actuator (14) is adapted to move the sheet diverter assembly, wherein the actuator is coupled to the sheet diverter assembly using a resilient coupling (19) that acts to prevent the sheet diverter assembly from rebounding when moved against the at least one end stop (16).

Description

SHEET DIVERTER

This invention relates to a sheet diverter assembly and a method for its operation. Sheet diverters for use in banknote sorting machinery, for example, banknote sorting machines and other equipment are well known. A typical diverter mechanism comprises a shaft on which are mounted one or a number of laterally spaced vanes or blades. The vanes direct each sheet to its desired destination and this destination may be changed by rotating the shaft. This rotation is typically performed by a DC motor that drives the shaft through a gear train and end stops are used to limit the extent of rotation. Rotating the shaft allows the destination for the sheet to be selected. However, there is a problem with this type of mechanism when it is operated at high speeds. Although it can be successfully used at operational speeds of up to ten notes per second, that is to say that the diverter vanes can be driven between the end stops ten times per second, it is found that at higher speeds the impact of the mechanism against the end stops causes excessive rebound of the diverter vanes and this prevents the diverter from operating at the desired speed. An alternative choice of actuator, for example a stepper motor is unsuitable in this application as a low cost solution is required. In accordance with the present invention, there is provided a sheet diverter assembly which is movable between first and second positions so as to divert sheets along corresponding first and second paths; at least one end stop that constrains the movement of the sheet diverter assembly within a predefined path, the ends of which correspond to the first and second positions; and an actuator for moving the sheet diverter assembly, wherein the actuator is coupled to the sheet diverter assembly using a resilient coupling that acts to prevent the sheet diverter assembly from rebounding when moved against the at least one end stop. In a second aspect of the invention, a method of operating the apparatus of the first aspect of the^' invention comprises a. receiving- a divert signal indicating to which of the first and second positions the sheet diverter assembly should be moved; b. applying a first drive signal of a first magnitude to the actuator to drive the actuator to move the diverter assembly to the indicated position, the first drive signal being applied for a first duration that is sufficient to ensure that the sheet diverter assembly has reached the indicated position; and, c. applying a second drive signal of a second magnitude for a second duration after the first duration has expired to drive the actuator in the same sense as the first drive signal. The resilient coupling stretches during the initial movement of the actuator before the sheet diverter assembly has started to move. This mitigates the rebound of the sheet diverter assembly when it strikes the end stop as the tension in the resilient coupling acts along with the actuator to pull the sheet diverter assembly against the end stop. When the sheet diverter assembly rests against the end stop, the actuator continues to stretch the resilient coupling thereby causing the tension to increase and preventing the sheet diverter assembly from rebounding from the end stop. Since the sheet diverter assembly does not rebound from the end stop it is not necessary to wait for the sheet diverter assembly to settle before sheets can be allowed to pass the sheet diverter assembly without the risk of them jamming on the assembly. This means the sheets can pass through the assembly with a smaller gap between them. Hence, the invention provides a high speed sheet diverter which does not suffer from excessive bounce and which can be manufactured at a low cost . In a preferred embodiment, the diverter assembly is rotatable between the first and second positions and the end stop constrains the rotation to a predefined arc. The diverter assembly may comprise a rotatable shaft on which are mounted one or more diverter vanes . The actuator may be any of various different devices. For example, a double acting solenoid or a pair of opposed solenoids may be used. Preferably, however, the actuator is a motor, such as a DC motor. In this case, the resilient coupling may comprise a resilient band, such as a rubber O-ring, stretched around two pulleys, one of which is mounted on the motor and one of which is mounted on the sheet diverter assembly. An alternative is that the resilient coupling may form part of a more complicated drive train between the actuator and sheet diverter assembly. For example, a gear reduction, gearing-up, or other mechanism may be situated between the actuator and resilient coupling or between the resilient coupling and the sheet diverter assembly or in both locations. The at least one end stop may have a resilient surface, for example a covering made of rubber or other resilient material. This has the advantage of reducing the noise generated as the diverter strikes the at least one end stop. Typically, the pulley mounted on the sheet diverter has an arcuate slot through which the end stop protrudes . The ends of the slot then correspond to the ends of the predefined arc. As previously mentioned, the diverter assembly can be operated at high speeds . The rate at which the diverter assembly moves between the first and second position is typically 20 sheets per second. Normally, the apparatus further comprises a controller that a. receives, in use, a divert signal indicating to which of the first and second positions the sheet diverter assembly should be moved; b. applies a first drive signal of a first magnitude to the actuator to drive the actuator to move the diverter assembly to the indicated position, the first drive signal being applied for a first duration that is sufficient to ensure that the sheet diverter assembly has reached the indicated position; and, c. applies a second drive signal of a second magnitude for a second duration after the first duration has expired to drive the actuator in the same sense as the first drive signal . In one embodiment, the second drive signal is lower in magnitude than the first drive signal, although it could be the same magnitude or even higher in magnitude than the first drive signal . In this way, the motor is driven at high speed such that the diverter assembly moves quickly between the first and second positions but then the magnitude of the drive signal is reduced so that the actuator is still driven such that it drives the diverter assembly against the end stop but without causing damage to the actuator. Typically, the second duration is such that the second drive signal is applied until such time as the diverter is required to move to the other of the first or second position from its current position. The second drive signal may be removed if a machine incorporating the sheet diverter assembly is switched to a standby mode in order to save the power required to apply the second drive signal. Similarly, if the machine is switched off, the drive to the actuator is removed completely. In an alternative embodiment, the second magnitude is zero and the first duration is such that the actuator stops before the sheet diverter assembly has reached the indicated position, or as it reaches the indicated position. The tension in the resilient coupling is released to carry the sheet diverter assembly to the indicated position or, if the sheet diverter assembly was already in the indicated position the tension continues to act on the sheet diverter assembly, keeping it in the indicated position and hence, in contact with the end stop without the need to continue to drive the actuator. Typically in these situations, the actuator is prevented from moving in reverse for example by its own inertia or a clutch. The invention has many applications, for example in document and banknote sorting. A typical banknote sorter may have a plurality of output pockets for storing banknotes, each output pocket receiving banknotes diverted from a transport path by respective sheet diverter assemblies, although, typically, the last pocket adjacent the transport path will not have an associated diverter assembly, bank notes being placed in this pocket by default if they have not already been diverted when they reach it. The banknotes are typically sorted on the basis of note facing, note orientation, denomination, condition, currency or whether or not they are counterfeit, for example. The invention will now be described with reference to the accompanying drawings, in which: - Figure 1 shows a side view of part of a banknote sorting machine incorporating three sheet diverter assemblies according to the invention; Figure 2 shows a perspective view of the diverter assembly, actuator and coupling; Figure 3 shows a side view of the diverter assembly in the first position; Figure 4 shows a side view of the diverter assembly in a second position; Figure 5 shows a timing diagram of the drive signal applied to the motor; and, Figure 6 shows schematically a control system for driving the motor. Figure 1 shows the side view of part of a banknote sorting machine 1. The banknote sorting machine 1 comprises three diverter assemblies 2,3,4, each of which is disposed adjacent a transport path 5 and is operable to divert notes from the transport path 5 into respective pockets 6,7,8. Any banknotes that are not diverted from the transport path 5 are deposited in a cull pocket 9. A more detailed view of one of the sheet diverter assemblies 2,3,4 is shown in Figure 2 as a perspective view. The diverter assembly comprises a shaft 10 that is journalled in bearings 11a, lib that are housed in opposite sides of the banknote sorting machine. A plurality of diverter vanes 12 are non-rotatably mounted on the shaft . The diverter vanes 12 are typically made from a lightweight but strong material, for example glass-reinforced plastic. Alternative materials include carbon-fibre-reinforced plastic or aluminium. These materials can be useful, as they are electrically conductive, for dissipating static charge from a bank note . At one end of the shaft 10, there is mounted a diverter shaft pulley 13 which is coupled to a DC drive motor 14 via a resilient drive belt 15 and a drive motor pulley 19. The resilient drive belt 19 is typically a rubber O-ring stretched over the diverter shaft pulley 13 and the drive motor pulley 19. An end stop 16 is mounted on a fixed stop plate 17 such that the end stop 16 protrudes through a slot 18 in the diverter shaft pulley 13. In this way, the rotation of the shaft 10 is constrained to an arc defined by the size of slot 18. As such, the end stop 16 in conjunction with the slot 18 defines first and second positions of the diverter vanes 12. Alternatively, the end stop 16 could be mounted on a sub-plate that can be moved relative to the rest of the assembly. As such, the position of the end stop 16 can be adjusted, for example to compensate for variability in the positioning of a note by the rest of the transport as it is directed at the sheet diverter assembly 2, 3, 4. By rotating these diverter vanes 12 to the first of two positions the note can be diverted from the transport path 5 whilst in the second position the note continues on the transport path 5. Figures 3 and 4 show side views of the diverter assembly in the first and second positions respectively. In Figure 3, the diverter shaft pulley 13 and hence, diverter shaft 10 and diverter vanes 12 have been rotated as far clockwise as possible such that the right hand end of slot 18 is pressing against end stop 16. The diverter vane 12 is positioned such that a sheet passing through aperture 20 (which forms part of transport path 5) is diverted along the top edge of diverter vane 12 into the respective one of the diverter pockets 6,7,8 associated with the diverter. Conversely, in Figure 4 the diverter shaft pulley has been rotated as far anti-clockwise as possible such that the left hand end of slot 18 is pressing against end stop 16. A sheet document passing through aperture 20 will then be diverted by the bottom edge of diverter vane 12 such that it continues along guide plate 21 which also forms a path of transport path 5. In this way, the note is not diverted from the transport path 5 and continues onto the next diverter assembly 3,4 or to the cull pocket 9. The operation of the diverter assembly will now be described with reference to Figure 5. In this Figure, a timing diagram showing the relative timing of a divert signal and the motor current is shown. The diagram shows the signals for only one of the three diverters but the operation is identical for the other two. A controller (not shown) is used to control the operation of the diverters and this will typically be responsive to signals received from various sensors located at other parts of the transport of the banknote sorting machine. These sensors and the signals received from them will not be described further as their understanding is not germane to this invention. In Figure 5, a decision has been made by the controller to divert a particular note from the transport path 5 into a pocket. As a result, the divert signal is asserted at T₀ and this causes a motor driver incorporated within the controller to drive the motor 14 at a current I_MΛX- For example, 1^ may be 1.5 amperes. After a time ΔT, the motor current is reduced to I_HOLD which for example may be 0.5 amperes. The time ΔT is chosen to guarantee that the diverter vanes 12 can move from one position to the other position before the current is reduced from 1^ to I_HOLD- By driving the motor 14 in this way, the diverter vane is moved into position 1 as shown in Figure 3 and the note is diverted into the respective pocket . The actual time taken for the diverter vane 12 to move from one position to the other will typically depend on several factors, for example the friction in the bearings 11a and lib and the inertia of the motor and diverter assembly. Thus, ΔT is chosen to be significantly larger than this actual time to guarantee that the diverter vanes has sufficient time to change position. At time T_1; the controller makes a decision that another note is not to be diverted but is to continue on the transport path 5 and the divert signal is correspondingly negated. As a result of this the motor current polarity is reversed and set to a magnitude of ^_I _MAX- This causes the diverter to revert to position 2 as shown in Figure . Again, at a time ΔT after T_x the motor current is reduced to -I_HOLD# at which value it continues to flow. It is important to realise that the time ΔT could, in fact, be different for each direction of operation of the diverter. This method of motor control allows the diverter vanes 12 to change position quickly but the motor current is then reduced to a level, I_HOD. that holds the diverter shaft pulley 13 against the end stop 16 but which will not be sufficient to overheat and hence, damage the motor 14. This reduced current, I_HOLD' can be applied to the motor indefinitely. A surprising advantage of reducing the motor current to a holding current in this way is that the reaction speed of the diverter is increased when the motor current polarity is changed because the magnetic field associated with the holding current, I_HOLD> is lower than that of the maximum current, I_MA , and so there is a lower magnitude magnetic field to overcome. Thus, the diverter responds quickly when the diverter vane 12 is required to change position. In a typical example, the value of 1^^- is 1.5A and this is applied for 20ms (i.e. ΔT=20ms) before reducing the motor current to a value of I_HOLD = 0.5A. Furthermore, the act of continuing to drive the motor 14 prevents the drive belt 15 from relaxing and allowing the diverter vane 12 from being inadvertently moved. The motor 14 does not continue to rotate but instead is stalled and as such applies a constant torque to the drive motor pulley 19 thereby holding the diverter vane 12 firmly in place. When the diverter vane 12 is required to change position, the resilient drive belt 15 is placed under tension since the motor 14 begins to move before the inertia of the diverter assembly 2,3,4, has been overcome. For example, if the motor 14 is rotated in an anti-clockwise direction to change from position 1, as shown in Figure 3, to position 2, as shown in Figure 4, then the drive belt 15 will be tensioned on its left hand side. As a result of this, the drive belt 15 stores energy during rotation of the diverter. shaft 10 and diverter vane 12 and this energy is . input into the system after the left hand end of slot 18 strikes, end stop 16 and mitigates the rebound of diverter vane 12 from the end stop 16. In essence, the energy stored in the drive belt 15 attempts to pull the diverter shaft pulley 13 past the end stop 16 and this prevents the diverter shaft pulley 13 from rebounding from the end stop 16. Figure 6 shows a schematic view of a controller 30 for driving the motor 14 along with motors 114,214 for driving the other two diverter assemblies 4,5 in the banknote•^• sorting machine 1. On assertion of signal DIVERT #1, the controller 30 causes output driver 31a to drive motor 14 at current 1^ for ΔT such that the diverter vanes 12 are moved so as to divert banknotes from transport path 5. After ΔT, controller 30 causes output driver 31a to reduce the motor 14 current to I_HOLD- This holding current is maintained, as previously described, until DIVERT #1 is negated when controller 30 causes output driver 31a to drive motor 14 at current -I_MAX fo ΔT thereby returning the diverter vane 12 to the default position such that it does not divert banknotes from the transport path 5. After ΔT, the current is reduced to -I_HOLD ^at' which value it remains until DIVERT #1 is again asserted. Controller 30 controls motors 114 and 214 via output drivers 31b and 31c in the same way in response to signals DIVERT #2 and DIVERT #3. The signals DIVERT #1, DIVERT #2 and DIVERT #3 are normally received from a transport controller (not shown) which receives and processes signals from sensors (not shown) on the banknote sorting machine 1. This transport controller may incorporate controller 30. Whilst the use of a motor actuator has been discussed above, it will be- appreciated that one or more solenoids could be used as the actuator. Therefore, in a further example, the drive motor pulley 19 may be coupled directly to a solenoid so as to move the drive motor pulley 19 between two positions which, in turn, cause movement of the diverter vane 12 between the respective diverter positions. A single solenoid (biased towards a non-energised position) may be used for this purpose, or two solenoids could be used, working in a complementary manner. In another example, rather than using a pulley arrangement, one or more solenoids could be coupled directly to the diverter assembly (such as to the vanes 12 or a modified part of the shaft 10) . In this case, the resilient coupling could take the form of a spring or piece of resilient material such as rubber, either being arranged to transmit the force of the solenoid(s) to the diverter assembly.

Claims

1. Apparatus comprising a sheet diverter assembly which is movable between first and second positions so as to divert sheets along corresponding first and second paths; at least one end stop that constrains the movement of the sheet diverter assembly within a predefined path, the ends of which correspond to the first and second positions; and an actuator for moving the sheet diverter assembly, wherein the actuator is coupled to the sheet diverter assembly using a resilient coupling that acts to prevent the sheet diverter assembly from rebounding when moved against the at least one end stop.

2. Apparatus according to claim 1, wherein the diverter assembly is rotatable between the first and second positions and the end stop constrains the rotation to a predefined arc .

3. Apparatus according to claim 1 or claim 2 , wherein the sheet diverter assembly comprises a rotatable shaft on which are mounted one or more diverter vanes.

4. Apparatus according to any of the preceding claims, wherein the actuator is a motor or one or more solenoids.

5. Apparatus according to claim 4, wherein the resilient coupling comprises a resilient band stretched around two pulleys, one of which is mounted on the actuator and one of which is mounted on the sheet diverter assembly.

6. Apparatus according to claim 5, wherein the pulley mounted on the sheet diverter has an arcuate slot through which the end stop protrudes, the ends of the slot corresponding to the ends of the predefined arc.

7. Apparatus according to any of the preceding claims, wherein the rate at which the diverter assembly moves between the first and second positions is greater than twenty times per second.

8. Apparatus according to any of the preceding claims, wherein the apparatus further comprises a controller that: a. receives, in use, a divert signal indicating to which of the first and second positions the sheet diverter assembly should be moved; b. applies a first drive signal of a first magnitude to the actuator to drive the actuator to move the diverter assembly to the indicate position, the first drive signal being applied for a first duration that is sufficient to ensure that the sheet diverter assembly has reached the indicated position; and, c. applies a second drive signal of a second magnitude for a second duration after the first duration has expired to drive the actuator in the same sense as the first drive signal .

9. A method of operating the apparatus of any of claims 1 to 7, the method comprising: a. receiving a divert signal indicating to which of the first and second positions the sheet diverter assembly should be moved; b. applying a first drive signal of a first magnitude to the actuator to drive the actuator to move the diverter assembly to the indicated position, the first drive signal being applied for a first duration that is sufficient to ensure that the sheet diverter assembly has reached the indicated position; and, c. applying a second drive signal of a second magnitude for a second duration after the first duration has expired to drive the actuator in the same sense as the first drive signal .

10. A method according to claim 9, wherein the second drive signal is lower in magnitude than the first drive signal .

11. A method according to claim 9 or claim 10, wherein the second duration is such that the second drive signal is applied until such time as the diverter is required to move to the other of the first or second position from its current position.

12. A document sorter comprising apparatus according to any of claims 1 to 8, operated according to the method of any of claims 9 to 11.

13. A banknote sorter comprising apparatus according to any of claims 1 to 8, operated according to the method of any of claims 9 to 11.

14. A banknote sorter according to claim 13, the sorter having a plurality of output pockets for storing sorted banknotes, each output pocket receiving banknotes diverted from a transport path by respective sheet diverter assemblies.