GB2170908A

GB2170908A - Sheet material thickness measuring equipment

Info

Publication number: GB2170908A
Application number: GB08501147A
Authority: GB
Inventors: Alan Walter Sills
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-01-17
Filing date: 1985-01-17
Publication date: 1986-08-13
Also published as: GB8501147D0

Abstract

Equipment for measuring the thickness of sheet material, e.g. banknotes, which comprises a fixed probe 19 and a movable probe 13 whose head 17 is in contact with the fixed probe in the absence of a banknote. Note-gripping rollers 7 and 9 drive a banknote between the probes. The movable probe is pressed back against a compression spring 21 and the amount of movement is indicated by the output of a probe coil 13'. This indication is of the thickness of the banknote. The components may be repeated in a plurality of measuring stations across the note path. <IMAGE>

Description

SPECIFICATION Measuring equipment The present invention relates to measuring equipment and in particular to equipment for measuring the thickness of sheet material.

Such equipment finds application in bank note counting apparatus. However it is emphasised that the present invention is not intended for use merely in bank note counting apparatus.

Apparatus for counting bank notes usually incorporates thickness measuring equipment in order to ensure that where two notes so adhere together as to pass through the apparatus as one note, they are not counted as one note because the thickness measuring equipment identifies them as thicker than a single note.

Conventionally bank note thickness measuring equipment comprises a mechanically complex mechanism in which notes are passed successively through rollers which are displaced from each other by the thickness of the passing notes. By their very nature, measuring as they do thicknesses of the region of 0.004" (0.10mum) these mechanisms should be very precise, but their precision has led them to be complex and hence massive. They must operate at high speed and their massiveness leads to the generation of high mechanical inertia forces during the passage of notes through them. These forces take a relatively long time to be damped out in comparison with the time taken for the notes to pass through the mechanism.Traditionally these problems of complexity and high inertia have been accommodated by ensuring that one of two rollers through which the bank notes pass remains translationally fixed in a rigid datum frame. This frame is itself a source of weight and cost for the mechanism. The other roller is moved with respect to the one by a note passing between the two rollers. A source of error can be that the actual measurement taken is that of the movement of the movable roller and inaccuracies can be introduced due to the linkages involved. Generally it has not been possible to arrange more than one pair of rollers across the width of the note path because of the need to precisely guide the other movable roller.

The object of the present invention is the provision of improved thickness measuring equipment in particular though not exclusively for bank note counting apparatus.

In my patent application No. 8414770 of 9th June 1984, 1 proposed the use in thickness measuring equipment of physical characteristics which change with the separation of two sensor elements, which elements are separated by the thickness of sheet material during passage therebetween of the sheet material.

Accordingly measuring equipment of the invention of my earlier application No. 8414770 comprises two sensor elements arranged to be mutually displaceable, for movement apart by the thickness of sheet material on passage of the sheet material therebetween, means for detecting the change in a physical characteristic acting between the sensor elements on movement apart of the sensor elements and means for guiding the sheet material through the sensor elements.

Either one of the sensor elements may be fixed and the other displaceable from though spring-biased towards the one. Alternatively they may both be displaceable though springbiased towards each other. In any case they will normally be in contact except when moved apart by the sheet material.

I have now developed further my invention.

In my patent application No. 8500228, 1 described the presently preferred embodiment of the invention of my application No. 8414770.

This embodiment includes a particularly advantageous arrangement of the guiding means with respect to a pair of sensor elements, one on each side of the note path. The guiding means comprises four rollers between which the note is nipped and guided past the pair of sensor elements, the rollers being arranged in pairs one roller of each pair being on each side of the note path and the pairs being on opposite sides of the pair of sensor elements with respect to the lateral extent of the note path through the equipment.

I have now realised that it is not necessary to employ sensing elements functioning in accordance with a change of physical characteristic between themselves to measure the distance between themselves caused by the presence of the note between themselves. A substantial improvement can be achieved in comparison with prior equipment relying on the movement apart of rollers if mechanical probes are employed, in place of the sensor elements of my earlier application No.

8500228. The movement apart of the probes in the presence of a note is measured by displacement measuring means.

One of the probes is preferably fixed to a frame of the equipment, whilst movement of the other probe is measured with respect to the frame. The frame can be considerably lighter than for a conventional equipment relying on movement of a roller guiding the note through the equipment. Reliance on a frame was one of the problems of conventional equipment because of the high inertia of the moving parts. However, in the present equipment the moving parts can be light and hence distortion of the frame can be kept within acceptable limits.

Normally the note will be rubbed by the probes on its opposite sides as it passes through the equipment. However, it is conceivable that the probes may each be equipped with its roller. Such rollers would be in addi tion to the note guiding rollers.

The note guiding rollers will preferably be driven for driving the note past the probes in addition to guiding the note. In an alternative the two guiding rollers on one or both sides of the note path may be provided as portions of a laterally continuous rotating member.

However, the area of contact of such a member with the note, whether provided on one or both sides of the note, will be discontinuous at the probes.

The measuring probes and four rollers may be provided in groups at measuring stations distributed laterally of the path of the note through the equipment.

Conventional electromechanical means may be employed for measuring the displacement of the movable one or both probes, such as an inductive displacement transducer, wherein a core moves in a coil, or strain gauges on a flexing member.

It should of course be noted that the measuring equipment may be used for measuring the thickness of sheet material other than bank notes.

To help understanding of the invention a specific embodiment thereof, and a variant, will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional end view on line I-I in Figure 2 of measuring equipment of the invention, Figure 2 is a scrap plan view of the equipment of Figure 1, and Figure 3 is a view similar to Figure 1 of a variant.

Referring first to Figures 1 and 2, the measuring equipment there shown has an aluminium frame comprised of two end plates 1-for supporting bearings for drive shafts 2,3-and sheet angles 4,5 attached by end flanges 6 to the end plates. It should be noted that in comparison with the frame described in my application No. 8500228, the frame is torsionally stiffer. In particular the webs 16,20 of the angles 4,5 have reinforcing flanges 16',20' to counter flexure of the flanges.

The drive shafts 2,3 extend between the end plates 1 (of which only one is shown) and carry drive members, those on shaft 2 being referred to as rollers 7 and those on shaft 3 as wheels 8; since the drive rollers 7 roll on notes passing through the equipment whilst the drive wheels 8 do not directly drive the notes. In the absence of a note in the equipment each drive roller 7 contacts and drives a driven roller 9. When a note is pre sent between the rollers 7 and 9, the driven rollers 9 continue to be driven by the drive wheels 8. A non-illustrated drive train and motor is provided for driving the members 7,8 in suitable directions at suitable speeds. All the drive members are provided with O-rings 10 in grooves on their circumferences for transferring their drive.

As may be seen in Figure 2, the drive rollers 7, driven rollers 9 and drive wheels 8 are provided in pairs at measuring stations. Several such stations may be provided across the path of a note through the equipment, but only one is shown and described here.

At the measurement station, the drive members are axially and rotationally fast on their drive shafts. The driven rollers 9 are rotatably mounted on opposite sides of a probe block 11 on spigots 12 fast in the block. Extending centrally of the block, between the rollers 9 and normally towards the drive shaft 2 is a displacement probe 13 for which a bore 14 is provided in the block. The probe is located in the block by a grub screw 15. The block itself is secured to the web 16 of the aluminium angle 4.

Opposite the head 17 of the core 18 of the probe, a complementary probe blade 19 is provided. It is irrotationally secured to the web 20 of aluminium angle 5. The displacement probe core 18 is urged by a core spring 21 into contact with the probe blade 19-in the absence of a note.

When a bank note 22 is introduced in the direction of the arrow A between the head 17 of probe 13 and the blade 19, the former will be displaced backwards against the spring 21 by an amount at the sensor head corresponding to the note's thickness. The probe 13, via its coil 13' will give an output indicative of the thickness of the note.

The geometry and arrangement of the components at the measurement station should be noted in two respects. Firstly, as may be seen in Figure 1, the blade 18 at 23 and the probe block at 24 are radiused with a smaller radius of curvature than respectively the drive rollers 7 and the driven rollers 9. Since the tangential contact between the rollers 7,8 and the blade at 23 and the block at 24 (if the probe head 17 is moved back flush with the radius 24 by an extraordinarily thick note) are at the same level, the radiusing to a smaller radius provides that the bank note is primarily guided by the rollers 7 and 8 and only contacts the pro be/block combination and the probe blade at the level of their normal contact. Where the O-ring tyres are provided with sufficient relisi ence, they can grip the note both upstream and downstream of the probes' contact with the note.

Secondly, as may be seen in Figure 2, the head 17 is set slightly proud of both its block 11 and the driven rollers 9 whereby to ten sion the note 22 via the spring 21 as it passes in a slightly curved shape between the rollers and the sensor and blade. Where the spring is inadequately strong such that the tension in the note deflects it from the probe blade 19, the arrangement may be modified such that the blade 19 is slightly proud of the rollers 7. Similarly the head 17 is slightly set back from the rollers 8.

In the variant of Figure 3, the probe block 11" has a solid nose 17" opposite which the probe blade 19" is a resilient blade equipped with strain gauges 25 for measuring deflection of the blade from the note 17" in the presence of a note. The blade 19" is held fast in a block 26 secured to the web 20. Other components are substantially as in Figures 1 & 2 embodiment and the notes are passed through in a similar manner.

The output from the coil 13' or the strain gauges 25 is fed to analysing equipment for identifying the displacement of the core 18 or the blade 19" resulting from the presence of a note. Preferably the analysing equipment is arranged to compensate for drift due to frame deflection and consequent separation of the probe blocks 11,11" and probe blades 19,19" by comparison with an assumed zero of displacement in the absence of a note.

Other arrangements are possible, for instance two resilient probe blades equipped with strain gauges may be employed; one being on one side of the note path and the other on the other side of the note path. Figure 3 shows another feature differing from Figure 1 in that the roller 7' is of a single rotatable member machine away at 2" to provide a shaft part and space for the probe blade 19".

Claims

1. Sheet material thickness measuring equipment having at least one measuring station thereat defining a path for sheet material through the equipment, the or each measuring station comprising two pairs of material transport members, the transport members having sheet material guiding peripheral parts movable in the material path direction; a first mechanical probe at the measuring station to one side of the material path; a second mechanical probe at the measuring station to the other side of the material path and arranged opposite the first probe; at least one of the probes being adapted to move away from the other probe on passage of sheet material along the material path whereby the separation of the probes increases by an amount dependent on the thickness of the sheet material; and displacement measuring means adapted to give an output corresponding to the relative movement apart of the probes on the passage of the sheet material therebetween, both probes bearing directly on the sheet material during its presence therebetween; the pairs of transport members being provided on opposite sides of the probes transversely in the material path and the two transport members in each pair of transport members being provided opposite each other on opposite sides of the material path.

2. Equipment according to claim 1, in which one of the probes is fixed to a frame, the other probe is in contact with the fixed probe in the absence of sheet material therebetween, and the displacement measuring means measures the movement of the other probe with respect to the frame on the passage of sheet material therebetween.

3. Equipment according to claim 2, in which the material transport members are rollers, and the fixed probe has a head with a radius of curvature less than the radius of the material transport rollers on its side of the material path.

4. Equipment according to claim 2 or 3, in which the other probe is spring-biassed towards the one fixed probe.

5. Equipment according to claim 4, in which the spring-biassed probe is a leaf spring with a curved head.

6. Equipment according to claim 2,3,4 or 5, in which the fixed probe stands proud of the guiding parts of the material transport members on its side of the material path, whereby the probes and the transport members impose a curve on the sheet material transversely in the material path.

7. Equipment according to claim 4, in which the spring-biassed probe is a rectilinearly movable member.

8. Equipment according to claim 7, in which the spring-biassed probe stands proud of the guiding parts of the material transport members on its side of the material path when in contact with the fixed probe, whereby the probes and the transport members impose a curve on the sheet material transversely in the material path.

9. Equipment according to claim 7 or 8, in which the material transport members are rollers and the spring-biassed probe is within a fixed probe block having a head with a radius of curvature smaller than that of the transport roller on its side of the material path.

10. Equipment according to any preceding claim, in which the transport members are rollers and the probes bear on material therebetween substantially in a plane including the axes of rotation of the transport rollers on both sides of the material path.

11. Equipment according to any preceding claim, in which the material path through the equipment is substantially flat in the direction of material transport.

12. Equipment according to any preceding claim, in which a plurality of pairs of mechanical probes is provided in a corresponding plurality of measuring stations across the width of the material path.

13. Sheet material thickness measuring equipment substantially as hereinbefore particularly described with reference to Figures 1 and 2 or Figure 3 of the accompanying drawings.