GB2180678A - Magnetic identification system - Google Patents

Abstract

The system comprises a reader (3) having a magnet (8) and Hall effect generator means (9). A flag (1) is attached to or forms part of each item to be identified or a carrier therefor, and is adapted to pass adjacent to said generator means (9) during travel of the item. The flag (1) is of substantially non-magnetic material having at least one pin (5) of magnetically sensitive material extending through the flag (1), whereby, on passage adjacent the generator means (9), the presence of the pin (5) increases the magnetic field strength in the vicinity of the generator means (9) and is thereby detected and the flag identified by its unique pattern of pins (5). <IMAGE>

Description

SPECIFICATION Magnetic identification system The present invention relates to a magnetic identification system. One particular, but not exclusive, use of the invention relates to a magnetic identification system useful in dirty and harsh environments.

Many methods of magnetic identification are known in which a magnetic code is applied to the item to be identified, and the code sensed by a suitable reader. Oneform is a magneticstriptype system. Howeverthis suffers from the disadvantages that it is not sufficiently robust for some environments. An example of this type of system is disclosed in British Patent Specification No. 1086298 where a stationary magnetic strip can be read by its effect between a magnet and reed relays. It cannot easily be used with irregularly moving magnetic strips.

Another method is the use of permanent magnets to form the code, which is sensed with reed relays.

However, this suffers from the disadvantage that the magnets lose their magnetism with time and rough handling. Furthermore, in orderto provide an acceptable number of codes, there needs to be a large space available for placing the magnets and this is notalways convenient.

Other methods are known, for example from British Patent Specifications Nos. 1459185 and 2081949, where the identifying code is provided in a magnetic screening area so that each cutout allows passage of a magneticfield. However, this is insufficiently robust for many uses and again cannot always be used when the code is moved irregularly, as by hand.

Other systems for example British Patent Specification No.2006497 rely on balanced inductive circuits, which become unbalanced on passage of a coded strip orthe like. These are, however, not always reliable.

It is an object ofthe present invention to provide a magnetic identification system which overcomes the above disadvantages and allows reliable identification of items in a wide range of environments.

According to the present invention there is provided a magnetic identification system comprising a reader means having a magnet and Hall effect generator means, and a flag attached to orforming part of each item to be identified or a carriertherefor, the said flay being adapted to pass adjacent to said generator means during travel ofthe item and being of substantially non-magnetic material having at least one pin of magnetically sensitive material extending through the flag, whereby, on passage adjacent the generator means, the presence ofthe at leastone pin increasesthemagneticfieldstrength inthevicinityof the generator means and is thereby detected.

Preferably there are provided a plurality of pins, arranged on said flag in a predetermined pattern which serves to identify positivelythatflag.

Advantageouslythe Hall effect generator means comprises a plurality of individual generators arranged across the path of travel ofthe flag, and the pins oftheflag are disposed in one or more of a corresponding plurality of rows each adapted for align mentwith a respective one ofthe generators.

Each row may have a number of possible positions for a pin spaced therealong.

At least one pin of every flag may be positioned in a predetermined location whereby its passage can be used to determine the position relative thereto in the direction offlag travel of any remaining pins.

The at least one fixed pin may be in addition to the one of more pins used for identification purposes.

The reader may be enclosed in protective material with at least the portion adjacent the generator means being of magnetically sensitive material.

Embodiments of the present invention will now be more particularly described by way of example and with reference to the accompanying drawings, in which: Figure lisa diagrammatic cross-sectional view of a flag passing through a reader; Figure2isa planviewofaflag; Figure3 is a partial cross-sectional view through a reader; Figure 4 is a plan view of a reader casing; Figure 5is a front view ofthe casing; Figure 6is a cross-sectional view taken along the lineVI-VI of Figure 5; Figure 7 is an end view of the reader casing; Figure 8 is a plan view of a preferred embodiment offlag; and Figure 9 is a cross-section through an alternative embodimentofflag and reader.

Referring now to the drawings, a flag 1 comprises a T section piece of non-magnetic material. The preferred material is non-magnetic stainless steel although plastics or other materials may be used. The cross piece ofthe T section is adapted to be fixed to the item to be identified. The stem ofthe T section forms a flat plate 2 which is adapted to be passed through a reader3. In the embodiment shown, looking at Figure 2,the plate 2 has twelve positions 4arranged in three rows of four. Certain of these positions may be drilled out and a pin Sofa magnetically sensitive material is placed in each such hole to be an interfer ence fit. The preferred material is a different grade of stainless steel known as magnetic stainless steel.

Each flag in the system has a number of pins 5 inserted in a unique arrangement for each flag. As can be calculated, with twelve pin positions, it is possible to have upto 4095 uniquely coded flags. If more are required, then the number of pin positions must be increased. The pins are preferably3mm in diameter and the pin positions are at 5mm centres. The pins have a length dimension equal to that of the plate 2 sothatthefinal surface ofthe plate is smooth.

Another embodiment of flag is shown in Figure 8.

In this embodiment, the pin positions 4 are arranged as three rows of five, with the positions in alternate rows staggered by halfthe distance separating the pin positions. This allows more accurate sensing by the Hall effect generators, hereinafter referred to as sensors. In addition, to these fifteen pin positions, there are three marker pins 12 aligned with three of the pin positions in at leastone row. Thethree marker pins 12 have a constant position in every flag ofthe system and allow the sensing equipment to locate accurately which pin position is occupied by a pin.

In a further development, one further pin (not shown) may be provided, spaced somewhat from the others, to allowthe equipmentto determinethe dir- ection oftravel oftheflag.

In a first embodiment, a reader3 comprises anon- magnetic casing 6, which in use is sealed, having a channel 7 extending therethrough. The channel 7 is dimensioned to allowthe plate 2 of the flag 1 to pass through itasa close, butnottight,fit.The ends ofthe channel 7 are flared to lead in any slightly misaligned flags.

At an approximately mid way point of the channel and disposed either above or below the channel is a magnetorelectromagnet8. Disposed on the im- mediately opposite side ofthe channel 7 to the elec tromag net 8 are three sensors 9. They are arranged so that, when the end of the plate 2 is substantially in contact with the end of the channel 7, each ofthe sensors 9 is aligned with a row of pin positions 4. Amagnetically sensitive pin 10 is located in the casing of the readeradjacenteach sensor.

The reader is mounted by means of springs orthe like to provide give in both vertical and horizontal directions to allow for differences in flag mounting heights and horizontal positioning. The important criteria to be arranged when mounting a reader is thatthe end ofthe plate 2 will always substantially contact the end of the channel 7.

In the absence of aflag,the magneticfieldstrength in the vicinity of the sensors is constant. When a flag passes through the reader, the presence of a mag netically sensitive pin 5 adjacent a particular sensor 9 will increase the magnetic field strength in the region ofthatsensorand cause a change inthevoltagein the connections to the generator, whereby each pin5 is noted. Such voltage change is detected and it is a matter of com pa ratively sim ple electronics to integrate the signals from the various sensors and thereby identify the flag.

Another type of reader is shown in Figure 9. This type is particularly, but not exclusively, intended to identify "flags" concealed in the lip at the upper edge ofatray,carrying for example, machine parts orthe like.

As shown in Figure 9, the "flag" comprises an area ofthe lip 13 in which, say, thirty pin positions are provided in two rows of fifteen. The lower row com- prises fifteen marker pins 14 equidistantly spaced along the lip 13. The upper row may have between one and fifteen pins 15in anyorderof pins and nonpins.

In this embodiment, a channel cannot be provided and therefore, the sensors 9 are mounted between the zone of passage ofthe "flag" and the magnet 8.

The effect produced in this case by passage of a pin 14,15 is less marked than in the previous embodiment, butthere is still a detectable change in output voltage from the sensors and this can serve to identify each uniquely coded tray. A signal amplifier 16 may be provided to aid the detection of changes.

One use envisaged for the system is the identification of items, e.g. carcases, in a food processing factory. In this case, each flag will be fixed to a gambrel intended to carry a carcase along a rail. Such gam brews are generally manually moved and thus the flags may move at an irregular speed through each reader which is immaterial to the above described system. In a food processing factory, all the apparatus is regularly cleaned, possibly by steam cleaning.

The system is particularly advantageous in this re spect since each reader is totally enclosed and the flags have no holes or cracks where dirt, blood and fats could be trapped. The flags and readers are of stainless steel so that such cleaning does not cause corrosion.

Any temporary build-up offats, blood or grease on theflagsisimmaterial.The passageoftheflags through the channel effects a wiping cleaning action which removes any thick build-up, while the pres ence ofa thin layerwill not affectthechanges in magneticfield concentration which form the basisforthe detection method.

As stated above, the second embodiment is suited for identification of trays and the like. Either embodiment may be modified to identify pallets or other containers.

Claims (10)

1. A magnetic identification system comprising a reader means having a magnet and Hall effect gener ator means, and a flag attachedto orforming partof each item to be identified or a carriertherefor, the said flag being adapted to pass adjacent to said generator means during travel ofthe item and being of substantially non-magnetic material having at least one pin of magnetically sensitive material extending through the flag, whereby, on passage adjacent the generator means, the presence ofthe at least one pin increases the magnetic field strength in the vicinity of the generator means and is thereby detected.

2. Asystem as claimed in claim 1,wherein plurality of pins are arranged on said flag in a predetermined pattern which serves to identify positively that flag.

3. Asystem as claimed in either claim 1 orclaim 2, wherein the Hall effect generator means comprises a plurality of individual generators arranged across the pathoftravel oftheflag,andthepinsoftheflag are disposed in one or more of a corresponding plurality of rows each adapted for alignment with a respective one of the generators.

4. Asystem as claimed in claim 3,wherein each row has a number of possible positionsfora pin spaced therealong.

5. A system as claimed in any one ofthe preceding claims, wherein at least one pin of every flag is positioned in a predetermined location whereby its passage can be used to determine the position relative thereto in the direction offlag travel of any remaining pins.

6. A system as claimed in claim 5, wherein the at least one fixed pin is additional to the one or more pins used for identification purposes.

7. Asystem as claimed in any one ofthe preceding claims, wherein the reader is enclosed in protective material with at least the portion adjacent the generator means being of magnetically sensitive material.

8. A system as claimed in any one of the preced ing claims, wherein the magnet and the generator meansofthereaderareseparated byachannel through which each flag is adapted to pass.

9. A system as claimed in any one of claims 1 to 7, wherein each flag is adapted to pass adjacent the generator means, the magnet being mounted adja centthe generator means remotefrom the flag passage zone.

10. A magnetic identification system substantially as described herein with reference to the Figures ofthe accompanying drawings.