GB2243580A - Verifying print position setting of marking elements - Google Patents

Abstract

A marking assembly has a movable mark carrying member (1) which can be moved to bring any mark (2) thereon to a marking position and which has a magnetic attribute constituted by at least one North-South magnetic polarisation whose orientation can be sensed by mangetorestrictive sensors (1, 2) to monitor the absolute position of the member substantially continuously. As described a print wheel is indexed past a pair of magnetic sensors arranged in quadrature. <IMAGE>

Description

MARKING ASSEMBLY The invention relates to a marking assembly having a movable mark carrying member which can be moved to bring any mark thereon to a marking position; and monitoring means for monitoring the position of the mark carrying member. Such assemblies are hereinafter referred to as of the kind described.

Marking assemblies of the kind described are used in a wide variety of fields but find particular application as numbering boxes for applying serial numbers to security documents such as bank notes.

Many security documents are marked serially as in banknotes, or in batches as in some types of lottery ticket. Conventionally this is done by letterpress action of individual numbers selected from a set of regularly spaced numbers at the periphery of a metallic or plastic numbering wheel, held in a number printing box apparatus.

The numbering box is generally affixed to a numbering press which may be part of a printing press. The mechanical linkage between the press and the numbering box is actuated as each new document arrives, causing the box's advance mechanism to present the next serial number for printing.

Serial numbering normally occurs as the final printing process on security printed documents. That is it occurs on otherwise completely finished documents.

Despite the deceptive simplicity of the numbering process it is extremely important that serial numbers are printed with a high degree of accuracy so that every single document in a series is correct. If the equipment malfunctions, perhaps because a numbering wheel has stuck because of accumulated printing swarf or mechanical failure during a long number printing run, a wrongly printed document or series of documents may occur. Elimination of this wrongly numbered document and substitution with another is relatively expensive and time consuming; production of a new batch of security printed documents might even be required.

Such faults can be compounded if two numbering boxes are used to place numbers on banknotes, both having to print the same number each time. One box coming out of phase with the other can have an adverse effect on productivity.

A serial mark is generally composed from separate numbers and letters.

Most numbering boxes generally contain between four and twelve integer printing wheels, each having a sequential series of integers e.g. the numbers 0 to 9.

Individual numbering wheels usually have the same numbering font style but different wheels can be mixed. Roman figures, Gothic figures, Arabic figures, optically readable characters and bar codes may be employed. For example it is common to use a combination of wheels to mix letters and numbering for banknote serial numbering.

Bank cheques for example will generally have a serial marking number, a bank identification code number, the account number and transaction information e.g. the value of the cheque.

Such numbering need not be applied all at the one time; the transaction information is normally added later when the cheque is undergoing clearance. The bank identification code and the account numbers will not be changed for every cheque, rather for groups of cheques.

Such numbers are also applied by numbering boxes although the control of the numbers is not serial. The font style used for cheques is of the optical or magnetic character reading type.

In multiform booklets of, say, tickets the same serial number must be applied to each of the forms and only changed when the next booklet is being numbered.

An alternative form of marking may be used on certain security documents, that is bar coding. In bar coding a series of parallel lines are printed, often of two different thickness. Optical reading means records the bar sequence and/or spacing and this is then related to a unique number.

Numbering boxes may be used for sequential, repeat or skip numbering purposes. Special check digit numbering boxes may be associated with serial number boxes.

Generally the check digit is a single number.

Occasionally where the same characters have to be repetitively printed on thousands of documents, there may be a separate reciprocating plunger which carries these characters. This will be mounted beside the numbering wheels in the numbering box.

The actuating drives to the numbering box may rely solely on mechanical linkages or they may be connected to stepper motors to allow electronic control of the numbering.

Generally the boxes are available for printing parallel or at right angles to the print cylinder. These are often referred to as "straight" and "convex" boxes.

For some applications a number of individual numbering boxes may be attached to the circumference of a larger cylinder for example to permit mounting on rotary presses.

The surface of the character faces is flat and smooth with perhaps a slight curvature to match the radius of the printing cylinder.

In other equipment a series of character wheels may be mounted in tandem along a central shaft to allow the printing of bank check code lines. Other arrangements may be used for skip numbering purposes such as where multiple copies of numbered documents are printed simultaneously yet the individual documents produced by each cycle must be numbered in a single overall sequence.

For the purposes of this present invention the various styles will be described under the heading of "numbering".

In order to improve reliability electronic sensing means was introduced to make error detection automatic.

However such electronic sensing means relied merely on detecting that an indexing movement of a numbering wheel had occurred. No absolute position information was provided. If no movement had occurred then a fault indication was subsequently given. The method may be achieved by checking the movement of a component associated with indexing. An example of this is a system where the movement of a magnetic sensor at the end of a pawl was detected, rather than movement of the wheel itself.

Despite this improvement, there are still disadvantages; for example the detecting means only detects that movement has occurred; there is no direct correlation with the actual number being printed. Thus if the numbering box were accidentally set wrongly, then the sensing means would not indicate a fault condition as only positive indications of relative stepping actions would be given.

One prior electronic method of detecting number position was to mount a series of North, South and Zero magnetic poles into the periphery of a wheel. The order in which these arrive at the sensor determines the orientation. Here directional sensors would be used i.e.

no pole or N or S. A minimum of three sensors is required to detect this configuration; the circuitry would be accordingly complex. These are semi-analogue sensors i.e.

they only detect the presence of a pole or not and the polarity.

Another method was to use magnets, orientated purely North and South placed alternately between all printing faces of the wheel. Here only one digital sensor capable of measuring North and South need be employed. Other versions have been employed where magnets of only one polarity are used; in one version magnets are placed at every position. Thus no unique code would be received until the mechanism moved some other part of the printing wheel. In another version only one magnet was used providing positive information only when the wheel had incremented through one revolution. In these examples using only one polarisation of magnetism, the sensor may be very simple. One example would be a digital output Hall effect switch. In one further example of wheel positioning sensing mechanism two sensors were used for one wheel.One sensor indicated that the wheel was accurately in position and the other sensor that the wheel was approximately in position. The latter sensor did not specify where the wheel was precisely but simply that the wheel was within a given arc. This was achieved by having two discs with holes attached to the wheel, each disc being associated with a sensor and each disc having the same number of holes as printing positions. As the holes in one disc were larger than the holes in the other disc the first disc could give the approximate wheel positions and the second disc the accurate wheel positions.

In all the above prior methods the information received from the sensors is only valid at certain positions of the printing wheel. For example when the wheel is properly aligned a pattern of sensors may indicate that the correct facet is aligned for printing. However while the wheel is moving to the next printing position the information received may only indicate that the wheel is not ready for printing.

A further prior method of detecting number position is described in GB2213939, GB2213940 and GB2213941. Here a printwheel designed for postal franking, containing a flux conducting spiral ring moulded onto a plastic inner bearing surface, is mounted on a non-ferrous metal shaft which typically contains a magnet and a Hall effect sensor. As the printwheel rotates on the shaft the flux conducting spiral ring acts as a varying flux modifier to give readings of flux magnitude at the Hall effect sensor which relate to the position of the printwheel at any given instant. The printwheels described by these three documents are used mainly for postal franking purposes and so the various non-ferrous components can be made of relatively soft materials such as aluminium, brass and plastics since the pressure applied to the wheels in the franking process is relatively light.Security printing presses, e.g. letterpress apparatus, however demand much higher pressures. Not only would commonly available nonferrous shafts not be strong enough to withstand these higher pressures but also composite printwheels of the type described would be liable to distortion upon subjection to heavy radial pressure. Such wheel distortion could result in the highly undesirable situation where security printed serial numbers are printed out of sequence. A suitable shaft material for working this invention is non-magnetic stainless steel.

The magnet and Hall effect sensor in these documents are usually mounted as a pair within the shaft, about which the franking printwheel rotates, so that they are surrounded and shielded by the franking printwheel to prevent tapering Since the size of the shaft limits the space available for the Hall effect sensor and magnet the magnet used will necessarily be limited to a relatively low field strength. Hence the shaft is made of a non-ferrous material to eliminate possible shielding which would lower the field strength still further. In a security press environment however there is typically a high level of background magnetism from magnetic ink debris used in magnetic ink character recognition systems and therefore a low strength magnetic field would not be detectable over the background level.

In accordance with the present invention, a marking assembly has a movable mark carrying member which can be moved to bring any mark thereon to a marking position; and monitoring means for monitoring the position of the mark carrying member characterized in that the mark carrying member has a magnetic attribute constituted by at least one North-South magnetic polarisation whose orientation can be sensed by the monitoring means to enable the monitoring means to monitor the absolute position of the member substantially continuously.

Monitoring the or each North-South polarisation means that the absolute position of the member can be substantially continuously sensed. This can be achieved by using continuous, i.e. analog sensing or multi-level digital sensing in which the number of positions sensed is a multiple of the numbers of printing positions.

Furthermore, the invention enables a tough assembly to be constructed which can also withstand background magnetism caused by swarf. Thus the marking member can be mounted on a conventional, metallic shaft which may or may not be ferromagnetic.

The invention is applicable to the monitoring of a single mark carrying member even if this is incorporated in a marking assembly having more than one such member but in general each mark carrying member, if there is more than one provided, will be monitored.

The (non-repetitive) magnetic attribute may be achieved by applying an overall magnetic polarisation to the mark carrying member, or by applying a local magnetisation for example by incorporating into the mark carrying member magnetisable material such as barium ferrite or barium titanate or other ferromagnetic material, for example in a ceramic composite.

In most applications, the mark carrying member will be movable in a cyclic manner and will typically comprise a rotatable wheel. The wheel may be made of high grade steel, hard plastic, sintered compositions or rubber over steel. Such wheels may be provided with magnetisable inserts on the periphery or core.

In one example, a stainless steel wheel having a magnetised ferrite annular insert may be magnetised to give it a planar North-South magnetisation. Thus for example in a ten segment wheel which prints from 0 to 9, 0 may be made North and 5 South. The wheel may have an annular insert or a core made of a different material to the rest of the wheel. In this case the annular insert or core can be magnetisable and magnetised to give it a planar North-South magnetisation whilst the rest of the wheel is made of a non-magnetisable material. For example the core can be made of a ferromagnetic metal and the rim of the wheel made of a non-ferromagnetic metal. Another possibility is for the core to be made of one kind of steel whilst the rim of the wheel is made of a different steel; the core steel being more magnetisable than the rim steel.The core can be of a variable size, in some cases being almost as large as the wheel itself. In another example, a steel or other wheel may have incorporated in it magnetic material of different planar North-South magnetisation orientations.

Thus for example there may be inserts of a magnetisable material such as barium ferrite ceramic plugs. A similar quantity of ferrite may be incorporated on each segment but each can be magnetised to a unique polarisation orientation. In a third example, provided the wheel is of sufficient diameter, it is possible to place the magnetisable material inside a land of the wheel.

While the core may be of ferromagnetic material surrounded radially by the magnetisable material it is important not to place ferromagnetic material between the magnetisable material and the sensor because shielding would occur.

In still further examples, different magnets may be mounted on the periphery of the mark carrying member.

These magnets may be mounted by locating them between the mark faces.

A further aspect of the invention is a numbering wheel for use in a serial numbering printing box in which the wheel has a series of regularly spaced numbers on its periphery and associated with one or more of these numbers is/are respective unique marking/s which when sensed define a specific orientation of the wheel which in turn defines the number at that place on the periphery of the wheel.

The markings are of material producing a detectable magnetic field allowing the use of an analogue magnetoresistive or Hall effect detector. Magneto resistive devices are preferred because of their greater sensitivity. They may be used to sense the wheel position while it is stationary and while it is moving.

The monitoring means will typically comprise one or more sensors capable of generating an analogue output signal so as to indicate substantially continuously the absolute position of the mark carrying member. Thus, the monitoring means may comprise one or more Hall effect sensors or most preferably one or more magnetoresistive devices. Such devices have the advantage of compactness and durability rendering them very suitable for the intended application.

In one application, the monitoring means comprises two magnetoresistive sensors spaced apart along the path of movement of the mark carrying member. For example, in the case of a wheel, the sensors may be positioned at about 900 to each other. This is particularly suitable in the case where the wheel is magnetised to give it a single, overall planar North-South orientation. Each sensor will generate a sinusoidal output signal, the signals being in quadrature and the relative values of the two signals defining uniquely the orientation of the wheel.

In all applications, the monitoring means will in general be connected to a processor which compares the output signals from the monitoring means with a predetermined reference so as to identify the position of the mark carrying member.

Typically, the monitoring means will be positioned adjacent the periphery of the mark carrying member but in the case of a wheel, sensors of the monitoring means could be mounted in, but protrude from, a shaft about which the wheel is rotatably mounted. The sensors may be potted in place and will allow reading of magnetic markings either in an internal land of the wheel, which land is co-cylindrical with the shaft or in the bore of the wheel.

Typically, the assembly will be incorporated in a document numbering press which further includes fault indicating means coupled with the monitoring means of the marking assembly to indicate when a fault occurs. The fault indicating means may include visible or audio alarms, press power interrupters, document fault marking indicators such as ink jet markers and fault printouts.

The marks on the mark carrying member may have any conventional form and may include for example a number or a letter or other shape or symbol or any combination of these. Generally the marks will be solid shapes but striated marks and bar codes may be employed.

Numbering wheels, which may be mounted in numbering boxes, can be used for printing characters of one or more font type or can be varied in some way, for example, to allow patterning of individual number shapes or to allow printing with one or more graded colours across any single character or serial numbering character set.

The numbering boxes may be used to print character sets in which one character is presented above the next one so as to be read vertically downwards. Such character dispositions are taught in EP160504A and EP334930A.

Additionally pairs of boxes (or further multiples) may be employed with number printing comparison means provided in the controlling microcomputer to allow serial numbers to be printed twice on a document, such as a bank note.

Such paired numbering boxes may have one of the pair operating in accordance with the invention but preferably both are. Such numbering boxes may be used to print the following styles of number, in an combination, by way of illustration: a horizontally readable number with all characters being of a single type of font; a horizontally readable number with the characters comprising two types of character font; a horizontally readable number with the characters comprising more than two types of character font, preferably in which three or more of the characters which are adjacent are in progressively varying character fonts, for example, regularly increasing or decreasing in size; and a vertically readable number having any of the above characteristics.

The styles may be presented in any colour or combination of colours which may vary between the pair of serial numbers. The styles may be pointed in parallel to one edge of the document. Preferably one identification number will be presented such that is reading direction is the same as the normal viewing direction of the document and most preferably for a bank note both numbers are presented such that they are readable in the normal vicinity direction of the note.

The numbering box of the invention may be used in conjunction with an ink-jet or other electronic imaging printer instead of a further numbering box of the invention, in order to allow a serial number to be provided twice on a give authenticable or security printed item such as a bank note.

Examples of numbered security-printed documents, whether on paper, plastic or other substrates, include bank cheques, travellers' cheques, share certificates, bonds, deeds, banknotes, airline tickets, ferry tickets, entrance tickets, lottery tickets, passports, driving licences, and identity cards.

Cheques for example may have a serial number, a bank identification code number, the account number and a transaction value number.

Generally numbering wheels print one character per face but some types of lottery ticket have a few small letters flanking the main number. The small letters and the large numbers are applied during one printing impression of the face.

An example of a mark carrying member in the form of a wheel and apparatus for monitoring movement of the wheel in accordance with the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a schematic view of the wheel and a pair of sensors; Figure 2 is a block diagram illustrating the processing equipment coupled to the sensors; Figure 3 illustrates the analogue waveform outputs from the sensors of Figure 1; Figure 4 shows a section through a second example of a printwheel; Figure 5 shows a section through a third example of a printwheel; Figure 6 illustrates a fourth example of a printwheel; and, Figure 7 is of a section through the axis 34,35 of the fourth example of a printwheel shown in Figure 6.

Figure 1 illustrates a steel wheel 1 which is mounted on a non-ferromagnetic shaft 1A in use in a numbering box of conventional form (not shown) alongside a number of other similar wheels. The outer surface of the wheel 1 carries a number of raised marks 2 around its circumference which define indicia such as letters or other symbols. The wheel 1 also has a magnetisable core 3 surrounded by a nonferromagnetic metallic cover 3A. In use, a document 4 is brought alongside the numbering box at a marking position and the wheel 1 is indexed by rotating it about its shaft 1A until the required mark 2 is also at the marking position whereupon the document and wheel are pressed together causing an impression of the mark to be printed onto the document. In general1 the indexing of the wheel or wheels will be automatically controlled via mechanical linkages or by controlling stepper motors. The wheel thicknesses will generally be in the range 1.5 mm to 3 mm or beyond. It is important that the wheels do not distort.

A pair of magnetoresistive sensors 5, 6 (labelled A and B in Figure 1) are mounted adjacent the periphery of the wheel 1 with an angle between them of about 900. The core of the wheel 3 is made of magnetic steel and is magnetised to define North (N) and South (S) magnetic poles as shown in Figure 1. The metallic cover 3A may be made of stainless steel.

As the North (N) magnetic pole passes the sensor 5, the output signal from the sensor will reach a maximum as shown at 7 in Figure 3. In this case the sensor signal at 0 corresponds to the N-S poles vertically aligned with N at the top in Figure 1. Further clockwise rotation of the wheel 1 will cause the strength of the magnetic field sensed by the sensor 5 to fall to zero and thereafter to increase but in the opposite sense as the South (S) pole 8 approaches the sensor until a point 8 is reached. Further clockwise movement causes the output signal to return to zero and then for the cycle to repeat.

The output signal from the sensor 6 is similar to that from the sensor 5 but is offset by 900 as shown in Figure 3. As can be seen in Figure 3, at any point during rotation of the wheel 1, the output signals from the sensors 5, 6 will have a unique pair of values so that the rotational position of the wheel 1 can be absolutely determined.

This determination can be checked by a microprocessor 9 (Figure 2) connected via a pair of analogue-to-digital convertors 10, 11 to the sensors 5, 6 respectively. The microprocessor 9 includes a look-up table which defines the magnitudes of the signals from the sensors 5, 6 at a number of closely spaced increments and also receives a signal corresponding to the indexing control signal. In response to an indexing signal, the microprocessor 9 determines which pair of values it expects to receive from the sensors 5, 6 and compares the actual received values with the expected values. As a result of this comparison, the microprocessor 8 generates a "wheel correct" or "wheel not correct" signal and also generates a signal derived from the actual received signals indicating the actual angular position of the wheel 1.

Where more than one wheel 1 is provided, a single microprocessor can be used to receive the signals from each pair of sensors.

The sensors themselves can have any conventional form, for example the sensors known by the code number KMZ 10.

These sensors have small dimensions, for example being 4 mm square and 2 mm thick.

Figure 4 shows a number printing wheel 12 mounted on shaft 13 and having evenly spaced print faces 14 on the circumference. The wheel is made of stainless steel and two diametrically opposed bar magnets 15 and 16 are inserted as shown. The wheel is mounted in association with sensors 17 and 18. On the under side of the wheel is a machined ratchet 19 to allow stepping.

Figure 5 is as Figure 4 except that there is a variety of magnetic inserts 20 to 27 which provide a continuous gradation of the external magnetic field which would be sensed as the wheel rotates.

In Figure 6 a stainless steel numbering wheel 28 is mounted on a non-ferromagnetic shaft 29. An annular slot has been machined into the stainless steel and this has been filled with a magnetisable ferrite or titanate ceramic or similar composition 30. This has been diametrically magnetised to provide North and South poles as shown. This magnetic field is in a fixed position relative to the position of the numbering faces on the perimeter of the wheel. The use of a strong ceramic or similar insert serves to provide strength to the slotted wheel.

Sensors 31 and 32 are fixed at 90 degrees relative to the centre of the wheel. Paper 33 is also shown.

Figure 7 is a section along 34,35. Projection 34 is toothed to provide a ratchet actuating movement of the wheel. In a numbering box a series of these wheels would be mounted on the central shaft.

The numbering wheels of the invention may be employed to carry letterpress ink to the substrate. Alternatively between the numbering face and the substrate may be placed a transfer film on a carrier sheet such when the face is brought into contact with the substrate, that portion of the transfer film which has the shape of the numbering face is transferred to the substrate. The transfer film carrier then is moved forward to present a new area of transfer film ready for the next number printing action.

The ability which this invention offers to sense the position of a wheel accurately, allows the possibility for numbering wheels having angular separations between adjacent faces which are not identical to be employed.

Thus for example a wheel may be made having a single letter character, with each representation of that letter having a different height. Such characters would generally be arranged of differing heights in an incremental series of smallest to largest with the angular intervals with the radius between adjacent pairs varying accordingly.

Claims (10)

1. A marking assembly having a movable mark carrying member which can be moved to bring any mark thereon to a marking position; and monitoring means for monitoring the position of the mark carrying member characterized in that the mark carrying member has a magnetic attribute constituted by at least one North-South magnetic polarisation whose orientation can be sensed by the monitoring means to enable the monitoring means to monitor the absolute position of the member substantially continuously.

2. An assembly according to claim 1, wherein the magnetic attribute is constituted by a single, overall North-South magnetic polarisation applied to the mark carrying member.

3. An assembly according to claim 1, wherein the mark carrying member has one or more discrete amounts of magnetisable materials spaced around the member, each amount being magnetised to give a North-South magnetic polarisation.

4. An assembly according to any of the preceding claims, wherein the monitoring means comprises one or more sensors constituted by magnetoresistive devices.

5. An assembly according to any of the preceding claims, wherein the monitoring means comprises a pair of magnetic sensors offset along the path of the mark carrying member.

6. An assembly according to any of the preceding claims, wherein the mark carrying member comprises a rotatably mounted wheel.

7. An assembly according to claim 6, when dependent on claim 5, wherein the sensors are offset by 900 about the axis of rotation of the wheel.

8. A marking device including a number of marking assemblies according to any of the preceding claims, each movable mark carrying member of the device being associated with a respective one of the monitoring means.

9. A device according to claim 8, wherein the device comprises a numbering box.

10. An assembly according to any of claims 1 to 8 or a device according to claim 9 or claim 10, wherein the monitoring means is connected to processing means for providing an indication of the position of the or each mark carrying member.