Field of the Invention

This invention relates to identification apparatus for reading and identifying each of a plurality of identification tags. Such apparatus may, for example, identify livestock in a milking parlour, or in an out of parlour feeding station.

Background to the Invention

In modern milking parlours, it can be important to identify which animal is in which stall of the parlour. This information can be used to monitor each individual dairy cow in a herd on a day to day basis. Furthermore, the identification of animals in the stalls of a feeding station (which may also be a milking parlour) makes it possible to ensure that the correct ration of feed is dispensed to each animal in the station.

In one known form of identification system, each cow in a dairy herd is fitted with identifying ear tag which is arranged to emit an RF signal distinctive of the tag, and hence the cow wearing it. Each tag is read by means of an antenna at the common entrance to the stalls of a herringbone milking parlour. The antenna also generates an oscillating magnetic field which induces currents within an induction coil in each ear tag as it moves into range. Those currents charge up a capacitor within the ear tag, thereby providing the tag with sufficient energy to be able to emit its identification signal. The apparatus employs a driver to supply the necessary current to the antenna to create the field.

One disadvantage of this system is that it relies upon the cattle entering the stalls in a sequence which corresponds to the order in which the cattle pass the antenna. This relationship may not always hold.

In addition, the driver is expensive to purchase.

Summary of the Invention

According to a first aspect of the invention, there is provided identification apparatus for reading and identifying each of a plurality of identification transponders arranged to emit a corresponding identification signal, the apparatus comprising a plurality of antennae (preferably three or more), each operable to supply sufficient energy to a transponder in its vicinity to enable the transponder to emit its identification signal and to receive an identification signal; and driving means for supplying sufficient power to each antenna to enable it to supply said energy to a transponder, wherein the driving means comprises a common driver connected to the antennae.

Preferably, the common driver is also operable to analyse the signal received by an antenna to identify the transponder which has emitted the signal.

Since all the antennae are connected to a common driver, the invention provides a relatively cost effective means of providing a sufficient number of antennae for each stall of, for example, a milking parlour to be fitted with a respective antenna. Thus, the invention avoids the potential problems of cattle entering stalls in a different order from that in which they entered the milking parlour.

Preferably, the common driver has an antenna circuit which, in use, is connected to each of the antenna via a respective one

of a plurality of relays which are connected to control means operable to cause the driver to address each individual antenna in turn, so that at any one time, the antenna circuit is only connected to one antenna.

Thus, the power demand on the driver is only such as to enable a single antenna to be driven.

The relay may comprise a solid state switch (such as a triac), but preferably comprises an electrically operated mechanical switch.

Preferably, each of said relays comprises a single pole change¬ over relav. Preferably, each relay is situated adjacent to its respective antenna, the apparatus including a connecting cable for connecting the relays, and hence the antennae, to the driver, said relays being connected to the cable at intervals therealong.

Conveniently, the antennae are of substantially the same impedance as each other.

This enables the same design of antenna to be used, and thus helps to cut down on the number of different designs of components needed for the apparatus.

Since the anrennae are connected to the driver along differing lengths of cable, which itself has an impedance, the impedance seen at the driver of each load constituted by the antenna being addressed and the length of cable connecting it to the driver, will vary from antenna to antenna. In particular, the smallest impedance will be for the load comprising the antenna closest to the driver, the largest being for the load comprising the antenna furthest from the driver, and the loads comprising the other antennae will have impedances lying in a

range between those extremes.

It has been found that, when selecting antennae for the system, the inductance of each antenna should preferably be less than a respective maximum, to facilitate tuning of the resonance freσuency of the circuit (which includes that antenna) to the frequency of alternating current supplied by the driver. The value of each maximum depends in part on the length of cable connecting the antenna to the common driver, the smallest maximum value being for the antenna further or furthest from the driver.

Accordingly, the design of the antennae may be such that their inductance is slightly less than the maximum for said further or furthest antenna. Tuning can then be achieved using parallel capacitors, and/or series inductors.

Where the power supplied to each antenna is in the form of an electrical current of a predetermined frequency, the apparatus is preferably so arranged that said frequency is the resonance frequency of a circuit comprising the driver and any one of a number of loads, each comprising a respective one of the antennae.

Preferably, each load also comprises a tuning capacitor connected in parallel with its antenna.

Preferably, the capacitance of each tuning capacitor is such as to compensate for the effects that the cable connecting the respective load to the common driver would otherwise have on the resonance freσuency.

Preferably, the antennae are connected by a common cable to the driver, the antennae being connected to the common cable at intervals therealong.

Preferably, the cable is one of a plurality of such cables, each connecting a respective group of relays and associated antennae to the common driver.

Preferably, the or each cable is formed from oxygen-free copper.

It has been found that this sort of cable provides a particularly good connection between the driver and each of the relays.

Preferably, the apparatus includes an inductor connected to the common driver in parallel with the antennae.

This enables antennae of a greater inductance (i.e. with a greater number of windings, if the antennae are coil antennae) to be used. This in turn allows a higher voltage to be applied tc the antennae by the driver, and hence increases the range of the antennae.

The invention also lies in a station at which one or more activities are carried out by or on farm animals, the station comprising a plurality of stalls each for accommodating one animal at a time, a plurality of transponders each arranged to be carried by a respective animal, and identification apparatus, preferably as aforesaid, wherein each said antenna is mounted in or adjacent a respective stall, so as to identify an animal therein, by reading and decoding the identification signal emitted by the transponder carried by the animal.

The station may with advantage comprise a milking parlour for cattle, each transponder being housed in a respective ear tag.

Brief Description of the Drawings

An identification apparatus in accordance with the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a block circuit diagram of the apparatus;

Figure 2 is a plan view of a herringbone milking parlour with an identification apparatus installed therein;

Figure 3 is a plan view of an out of parlour feed station which can be fitted with identification apparatus according to the invention;

Figure 4 is a block circuit diagram of part of a modified version of the apparatus;

Figure 5 shows part of an ear tag which houses a transponder for use with the apparatus; and

Figure 6 shows the ear tag fitted to a cow.

Detailed Description

The apparatus shown in Figure 1 is for use in identifying cattle having ear tags each of which contains a transponder. The apparatus comprises fourteen antennae 1-14, each of which comprises a coil of multicore wire and, in use, emits an oscillating magnetic field for energising a pick-up coil of a transponder in its range so that the transponder can then emit an RF identification signal which is picked up by the antenna.

One such transponder is housed in the ear tag shown in Figure 5. The tag comprises a cylindrical body 220 from the rear of which a shank 222 projects. The end of the shank 222 has a

socket 224 for receiving a retaining stud (not shown) for holding the tag on a cow's ear. Figure 6 shows the tag on a cow's ear, the shank 222 extending through a hole in the ear. The stud is attached to the socket 224 after it has been pushed through said hole, so that the ear is sandwiched between the body 222 and the stud.

The currents needed to drive each of the antennae 1-14 are provided by a common driver 16, which in this example comprises a TIRIS 2000 reader supplied by Texas Instruments and which also reads signals received by the antennae from transponders so that the transponders (and hence the cattle wearing the tags) can be identified. The driver has a transmit freσuency of 134.2kHz.

The driver 16 has an RF module for generating an AC current to be fed to the antennae, and a control module which modulates the AC current from the RF module with a pulse εignal so that the AC current is supplied in intermittent bursts. The control module also controls the operation of the RF module, decodes and checks data received from the transponders, converts the data into a format suitable for feeding to a serial port of a computer and controls various input and output lines of the reader. The RF module includes an antenna circuit which has a variable inductance tuning coil for enabling an installer to tune the RF circuit to a given antenna.

The driver 16 has a terminal through which said currents are supplied, and through which received signals are fed to the driver, and that terminal is connected to two 16 amp signal pole change-over (ΞPCO) relays 18 and 20 through a cable 22 which forms a two-core bus. Each of the relays 18 and 20 is, in turn, connected to a respective branch cable 24 and 26. The cables 22, 24 and 26 are multi-strand cables formed from oxygen-free copper. The cables are therefore similar to

certain types of high quality loud speaker cables.

Each of the antennae 1 to 7 is located in a respective stall, and the antennae are thus connected to the cable 24, at regular intervals therealong, through corresponding relays 28-34. Similarly, relays 35 to 41 each connect a respective one of the antennae 8 to 14 to the cable 26 at intervals therealong. The relays 28-41 are all of the same type as the relays 18 and 20, and all the relays are connected to a control unit 44 by control lines 45 and 47, which is also connected to the driver 16. Each antenna is connected to its relay by a tail (for example) of 550mm of the same wire as is used for the antenna coil.

The control unit 44 controls the operation of the relays in such a way that, at any one time in the operation of the apparatus, only one of the antennae 1 to 14 is connected in circuit with the driver 16. The driver 16 supplies a burst of current to that antenna only, and after the burst of current, monitors that antenna for any identifying RF signal from an energised transponder, within the range of the antenna.

Any such signal is read by the driver 16, which then sends a signal, identifying the transponder concerned to the control unit 44 which can correlate that information with the identity of the antenna which received that signal. The process is then repeated for each other antenna of the apparatus in turn.

In this way, the apparatus not only identifies the transponders in the ranges of the antennae, but also determines which transponder is in the range of which antenna, and hence which cow is in which stall. Furthermore, the apparatus enables the operator to spot any cow which is not wearing a tag since such a cow, when in a stall, will not be identified.

In the embodiment of apparatus shown in Figure 1, all the antennae 1-14 have an inductance of approximately 22 micro Henrys.

In order to set up the driver, the relays 18 and 34 are closed so that the antenna circuit of the driver 16 is in circuit with the antenna 7 only, and the inductance of the tuning coil is altered until the peak to peak voltage in the circuit is at its maximum. This corresponds to the circuit having a resonance frequency of 134.2kH, i.e. the frequency of the alternating current supplied by the RF module in the driver 16. In this particular example, the inductance seen at the input/output of the antenna circuit when the antenna 7 is connected is 27 micro Henrys, and the inductance of the tuning coil is set at or near the middle of the range of inductances of the tuning coil.

Fine tuning of the antenna 7 is then achieved by connecting a capacitor, not shown, of a suitable capacitance to the circuit, in parallel with the antenna 7.

The circuits containing the antennae 1-6 are then tuned by connecting corresponding capacitors in parallel with those antennae. The capacitance of those capacitors progressively increases from the antenna 7 to the antenna 1 to compensate for the variations (resulting from the circuits having differing lengths of cable) in effect of the cable 24 on the impedance of the circuits containing the antennae.

Thus, the appropriate choice of tuning capacitor for any antenna enables that antenna to be used at any position on the cable 24.

In addition, a respective variable tuning inductor may be connected in series with each antenna to allow the antenna to be individually tuned. Furthermore, the tuning inductors

and/or capacitors can obviate the need to tune the system with the tuning coil.

The apparatus shown in Figure 1 is for installation in a milking parlour, each of the antennae 1-14 being located at one end of a respective stall so that each antenna can receive an identifying signal from a transponder on a cow in its stall. The apparatus therefore determines which cows are in which stalls, enabling, for example, the productivity of a dairy cow to be monitored or for each cow to be automatically provided with an amount of feed appropriate to that particular cow.

The milking parlour shown in Figure 2 has sixteen stalls 61-76 arranged in two rows, each of eight stalls. Access to each row of stalls is gained via a respective one of a pair of corridors 50 and 51 which are situated one on either side of a central operator's pit 53. In use, sixteen cows pass through either one of two entry gates 52 and 54, each cow then walking into one of the stalls. After milking, the cows leave the stalls and exit the parlour through exit gates 56 and 58.

Each stall also contains a respective antenna, for example, the antenna 60 in the stall 62. Each antenna forms part of an identification apparatus which is identical to the apparatus shown in Figure 1 in all details other than the number of antennae connected to each branch cable: eight in this case. One of the branch cables connects the antennae 61-68 to a TIRIS 2000 reader, the other connects antennae 69-76 to the same reader. Each antenna is mounted at its respective stall in such a position that, when a cow enters the stall, its head is adjacent to the antenna.

For the sake of clarity, the components of the identification apparatus other than the antennae have been omitted from Figure 2.

The antennae 61-76 all have the same inductance (18.5 micro Henrys in this example). Individual tuning (with parallel capacitors and/or series inductors) compensates for the effect of the differences in lengths of branch cable connecting the antennae to the reader.

The respective circuit containing each antenna is tuned so that the reader sees an inductance of between 26 and 28 (preferably 27) micro Henrys.

In the system shown in Figure 2, parallel capacitors, not series inductors, are used for tuning. The antennae (68, 76) furthest from the reading head are connected in parallel to capacitors of the largest capacitance, whilst the capacitors for the antennae (61, 69) closest to the reading head have the smallest capacitance. The capacitances of the parallel capacitor for the antennae 61 to 68 are 10.4nF, 9.2nF, 8.0nF, 6.8nF, 5.6nF, 4.4nF, 3.2nF and 2nF respectively. Each of the capacitors for antennae 69 to 76 has the same capacitance as the corresponding capacitor for the corresponding one of the antennae 61 to 68.

Identification apparatus according to the invention can be used in much larger milking parlours, for example parlours having forty stalls arranged in two rows each of twenty stalls.

Apparatus according to the invention can also be fitted to an out of parlour feed station, one example of which is shown in Figure 3. Reference Nos 150 to 153 each denote a respective stall, each of which is fitted with its own manger, respectively referenced 154, 156, 158 and 160 which is supplied with feed from a respective one of four feed dispensing hoppers 162, 164, 166 and 168 fitted above the manger. Each stall is fitted with a respective antenna.

In use, as a cow enters a stall of the feed station, its ear tag is read and a suitable portion of feed is supplied by the dispenser to the cow in that stall. Usually the cow's daily feed ration is divided into portions so that a cow may only receive, for example, a maximum of one quarter of its daily ration in each six hour period.

Figure 4 shows a TIRIS 2000 reading head 200 which is identical to the reading head 16 and is connected to 8 antennae 201-208 by a single branch cable 210 of 11.6 metres length.

The system includes an arrangement of a control unit, relays and a control line to connect each antenna to the reading head 200 in turn. The control unit relays and control lines are similar to those used in the system of Figure 1, and have been omitted from Figure 4 for the sake of clarity.

Each of the antennae 201-208 is connected in parallel to a respective capacitor of a capacitance indicated below the antenna. The apparatus includes an inductor 212 cf 50 micro Henrys which is connected in parallel with the antennae 201- 208. The inductor 212 reduces the contribution to the load (seen by the head 200) made by the inductance of whichever of the antennae 201-208 is in circuit with the head 200. In fact, the inductance of the load, L _τ , is given by the following formula:

L _τ "

( ^L ι ^L

Where L, is the inductance of the inductor 212 and L ₂ is the inductance of the antenna.

As a result, each of the antennae 201-208 can have a higher inductance, and hence more turns, than the corresponding antennae of the svstem shown in Figure 1.

As a result, higher voltages can be developed across each of the antennae 201-208 by the head 200 (values have been recorded in excess of lOOv (peak voltage)), and the range of each antenna is increased.

In fact, it has been found that a parallel inductor such as the inductor 212 enables an antenna to operate at a distance of over 50 metres from a reading head with a read range of about 600 mm, which is as good as the read range of a single antenna of inductance of 18.5 micro Henrys at a distance of 11.5 metres from the RF unit in the absence of a parallel inductor.