GB2240093A - Sheet sensing apparatus - Google Patents

Abstract

A sheet sensing apparatus comprises two pairs of laterally spaced rollers (28, 29; 26, 27) which are separated on passage of a sheet. Each pair of rollers (26, 27; 28, 29) is coupled to respective arms (8, 18) via styli (13, 20). Arm (18) is in the form of a see-saw plate fixed to the stylus (20) and moves in the opposite direction to the arm (8). In response to passage of a sheet between either pair of rollers an output signal is produced by relative movement between ferrite rod (21) and an inductor (10 Fig. 1) independently of the orientation of the sheet fed in. <IMAGE>

Description

SHEET SENSING APPARATUS The invention relates to sheet sensing apparatus of the kind comprising two laterally spaced pairs of co-operating guide surfaces wherein the passage of a sheet between a pair of the guide surfaces causes the surfaces to separate. Such apparatus is hereinafter referred to as of the kind described.

Apparatus of the kind described finds particular use in cash dispensing and document handling machines in which the apparatus is used to determine whether or not the documents are being incorrectly fed in an overlapped manner. This is to avoid dispensing or counting a pair of documents as a single document which would result in error. The separation of two pairs of guide surfaces is monitored since a metal thread is present in most currency.

There are several systems in current use which perform this function. Some of these systems employ rollers to provide the guide surfaces, arranged as pairs in contact with each other such that when a note passes in between the rollers, the rollers are forced apart.

This movement is detected by various sorts of transducers to enable a signal to be obtained which relates to the thickness of the note.

One problem with known apparatus of the kind described is that each pair of the co-operating guide surfaces is monitored independently and thus it is necessary to calibrate the different sensor systems prior to operation.

In accordance with the present invention, sheet sensing apparatus of the kind described further comprises a sensor including first and second co-operating members which, upon relative movement between the members, generate a corresponding output signal relating to the relative movement, wherein the first member is mechanically coupled with one of the guide surface pairs such that separation movement between the guide surfaces of that pair causes movement of the first member in one sense relative to the second member, and wherein the second member is mechanically coupled to the other of the guide surface pairs such that separation movement between the guide surfaces of that pair causes movement of the second member in the opposite sense relative to the first member.

We have devised a new sheet sensing apparatus in which a common sensor is provided for the two pairs of guide surfaces each of which is linked mechanically with respective members of the sensor. This avoids the calibration problems mentioned above since in practice only one of the first and second members needs to be adjusted during a setting up procedure. The invention also leads to a much cheaper system having very few (low cost) components and the ability to construct a modular cartridge containing the sensor which is easily replaceable.

In one example, the first and second members of the sensor comprise a ferromagnetic core and co-operating electrical coil. Such an arrangement is described for example in EP-A-344967.

Preferably, the first member is mounted to a pivoted lever on one side of the pivot, the other side of the pivot being coupled mechanically to one pair of the guide surfaces. In this arrangement, the apparatus preferably further comprises spring means for urging the lever in the direction opposite to that in which it moves upon seperation of the guide surfaces.

The second member may be similarly mounted but is preferably mounted on a cantilever coupled mechanically to the other pair of guide surfaces.

In the preferred arrangement, in which the members of the sensor comprise a co-operating coil and core, the cantilever is preferably provided by a printed circuit board carrying the coil. This considerably simplifies the construction of the device.

The guide surfaces could be provided by belts and the like but are preferably defined by pairs of rollers which are normally urged into engagement with one another.

The invention is particularly suitable for use in document handling machines such as cash dispensing and counting machines.

An example of a sheet sensing apparatus according to the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a schematic, plan view of the apparatus when dismantled; and, Figure 2 is a partial, side elevation of the apparatus in conjunction with two pairs of feed rollers.

The apparatus shown in Figure 1 comprises a sheet metal holder 1 or cartridge which contains and supports the main elements of the device. The cartridge 1 has a U-shaped section with folded up flanges 2 which have holes 3 for mounting within a machine structure. Two apertures 4,5 are provided spaced apart along the cartridge 1 which also has two pairs of holes 6,7.

A flexible printed circuit board 8 is positioned within the cartridge 1 to which it is fixed via rivets (not shown) extending through the holes 7 and corresponding holes 9 in the board 8. The electronic components are mounted in an area 8' coincident with the aperture 4 so that the components are isolated from the cartridge 1.

An inductor 10 is formed from a track on the PCB8 which winds in a spiral on both sides of the board round the central hole 11. The board 8 also has a hole 12 into which is glued a plastic stylus 13 (see also Figure 2).

A thin sheet metal leaf spring 14 is fixed to the back of the cartridge 1 by rivets (not shown) extending through the holes 6 and corresponding holes in the spring 15. Further holes 16 are provided on the spring 14 for attaching the spring to a see-saw plate 18 which has mating holes 17. The see-saw plate 18 has a hole 19 in which is glued a plastic stylus 20 similar to the stylus 13. A ferrite rod 21 is adjustably mounted via a screw thread in hole 22 in the see-saw plate 18. When the apparatus is assembled, the ferrite rod 22 projects through the central hole 11 of the spiral inductor 10.

Figure 2 illustrates the arrangement of the apparatus in conjunction with two pairs of laterally spaced guide rollers 26,27 and 28,29. The rollers 26,28 are mounted on a shaft 30 while the rollers 27,29 are mounted on a shaft 31. The shaft 30 is urged towards the shaft 31 so that the rollers define a pair of nips 32,33 between which sheets pass in use. As can be seen in Figure 2, the two style 13,20 engage the surfaces of respective rollers 26,28. When a sheet passes between the nips 32,33 it will cause the rollers 26,28 to move radially relative to the shaft 30. This radial movement will cause a corresponding upward movement of the styli 13,20. When the stylus 13 is moved upwardly, it will cause the PCB8 to flex to a position 34 through a distance indicated by 35.This flexure takes place about the pivot defined by the holes 7,9 by which the PCB8 is fixed to the cartridge 1.

Radial movement of the roller 28 causes upward movement of the stylus 20 which in turn causes the see-saw plate 18 to twist about its central axis to a deflected position 26 resulting from movement through a distance indicated at 36. This twisting action causes the ferrite rod 21 to move downwardly.

The mechanical advantages of the PCB8 and the see-saw plate 18 (the distances of the ferrite rod 21 and the stylus 13 from the respective pivots) are arranged so that a document thickness between either pair of rollers 26,27 or 28,29 produces exactly the same signal from the ferrite-coil interaction. If required, the ferrite rod 21 can be adjusted on assembly so that it gives an optimum initial signal, after which the relative movements of the coil and the ferrite are summed mechanically.

The plate 18 is made from light weight composite material while the PCB8 may be made from fibreglass board material which gives the system a low inertia of moving parts and hence a very fast frequency response. That is, by keeping the mass of moving parts to a minimum the system is made more sensitive.

It should be noted that the leaf spring 14 is preloaded so that when fixed to the cartridge 1 it exerts a downward pressure of the stylus 20 on the roller 28.

The interaction between the ferrite rod 21 and the coil 11 is exactly the same as described in more detail in our copending European patent application mentioned above the content of which is incorporated herein by reference. A detailed discussion of this interaction and the signals produced will not therefore be given.

The main advantages of the arrangement shown in the drawings are that it is cheaper than other systems having very few and low cost components; it is modular with the cartridge being easily replaceable; deflections are mechanically summed so electrical variations between separate sensors are avoided; high sensitivity is achieveable by using low mass parts; only a single adjustment (of the ferrite rod 21) is needed during the setting up procedure; there is minimum lost motion or play since the leaf spring and cantilever have no moving parts which may accumulate errors and by using the printed circuit board to mount the components and act as a dynamic component, fewer moving parts are required.

Claims (8)

1. Sheet sensing apparatus comprising two laterally spaced pairs of co-operating guide surfaces wherein the passage of a sheet between a pair of the guide surfaces causes the surfaces to separate, the apparatus further comprising a sensor including first and second co-operating meinbers which, upon relative movement between the members, generate a corresponding output signal relating to the relative movement, wherein the first member is mechanically coupled with one of the guide surface pairs such that separation movement between the guide surfaces of that pair causes movement of the first member in one sense relative to the second member, and wherein the second member is mechanically coupled to the other of the guide surface pairs such that separation movement between the guide surfaces of that pair causes movement of the second member in the opposite sense relative to the first member.

2. Apparatus according to claim 1, wherein the first and second members of the sensor comprise a ferromagnetic core and co-operating electrical coil.

3. Apparatus according to claim 1 or claim 2, wherein the first member is mounted to a pivoted lever on one side of the pivot, the other side of the pivot being coupled mechanically to one pair of the guide surfaces.

4. Apparatus according to claim 3, further comprising spring means for urging the lever in the direction opposite to that in which it moves upon separation of the guide surfaces.

5. Apparatus according to any of the preceding claims, wherein the second member is mounted on a cantilever coupled mechanically to the other pair of guide surfaces.

6. Apparatus according to claim 5, when dependant on claim 2, wherein the cantilever is provided by a printed circuit board carrying the coil.

7. Apparatus according to any of the preceding claims, wherein the guide surfaces are defined by pairs of rollers which are normally urged into engagement with one another.

8. Sheet sensing apparatus substantially as hereinbefore described with reference to the accompanying drawings.

8. Sheet sensing apparatus substantially as hereinbefore described with reference to the accompanying drawings.

Amendments to the claims have been filed as follows 1. Sheet sensing apparatus comprising two laterally spaced pairs of co-operating guide surfaces wherein the passage of a sheet between the pairs of guide surfaces causes the surfaces to separate, the apparatus further comprising a sensor including first and second co-operating members which, upon relative movement between the members, generate a corresponding output signal relating to the relative movement, wherein the first member is mechanically coupled with one of the guide surface pairs such that separation movement between the guide surfaces of that pair causes movement of the first member in one sense relative to the second member, and wherein the second member i8 mechanically coupled to the other of the guide surface pairs such that separation movement between the guide surfaces of that pair causes movement of the second member in the opposite sense relative to the first member.

2. Apparatus according to claim 1, wherein the first and second members of the sensor comprise a ferromagnetic core and co-operating electrical coil.

3. Apparatus according to claim 1 or claim 2, wherein the first member is mounted to a pivoted lever on one side of the pivot, the other side of the pivot being coupled mechanically to one pair of the guide surfaces.

4. Apparatus according to claim 3, further comprising spring means for urging the lever in the direction opposite to that in which it moves upon separation of the guide surfaces.

5. Apparatus according to any of the preceding claims, wherein the second member is mounted on a cantilever coupled mechanically to the dther pair of guide surfaces.

6. Apparatus according to claim 5, when dependant on claim 2, wherein the cantilever is provided by a printed circuit board carrying the coil.

7. Apparatus according to any of the preceding claims, wherein the guide surfaces are defined by pairs of rollers which are normally urged into engagement with one another.