GB2077473A - Improved switch and stock monitoring system - Google Patents

Abstract

An acceleration sensitive switch (18) is such that its contacts are closed in response to a predetermined acceleration of the switch. The switch is especially suited to use in a stock monitoring system, the arrangement being such that the acceleration sensitive switch connects power to a transmitter unit (4) to enable transmission of an alarm signal following a disturbance of the stock. <IMAGE>

Description

SPECIFICATION Improved switch and monitoring apparatus This invention relates to an acceleration sensitive switch and a stock monitoring apparatus incorporat ing the switch.

A problem with which farmers have been con cerned is the loss by theft or damage to stock caused by wild dogs, foxes or other predators. The object of the present invention is to provide a stock monitor ing system which will generate an alarm signal when farm stock begin to run which may be indicative of an attack by a predatory animal. Once the alarm signal has been received, the farmer can investigate the cause of the disturbance to the stock.

The invention also provides a new form of acceler ation sensitive switch which is especially suited for mounted on stock animals and in preferred forms can be adjusted so that it will be activated in response to a predetermined movement of the animal. For instance, the switch can be arranged so that when mounted on a particular location of the animal its contact will close when the movement of the animal changes from a walk to a trotting pace or a running pace.

More specifically, the invention provides an acceleration sensitive switch comprising a body within which is mounted an elastically deformable member, said body having a first electric contact associated therewith, the deformable member hav ing a second electric contact associated therewith and normally not engaging the first electric contact, the arrangement being such that when the switch is subjected to a predetermined acceleration, the mem berelastically deforms to a sufficient extent whereby the second contact engages the first contact.

The invention also provides a stock monitoring system comprising a transmitter unit adapted to be mounted on an animal, a receiver station for receiv ing signals transmitted from the transmitter unit, and an acceleration sensitive switch for mounting on the animal and coupled to the transmitter unit, the arrangement being such that the transmitter unit transmits an alarm signal when said switch has been activated.

The stock monitoring system may include a num ber of the transmitter units which are located on selected animals in various areas. The transmitter unit can be arranged to transmit signals which are representative of the identity of the transmitter unit so that on receipt of an alarm signal, the farmer will know the location of the stock which has been disturbed. Due to bandwidth restrictions, the systems of the invention would probably need to operate at the same base frequency and therefore it would be desirable to discriminate between adjacent systems to avoid the possibility of a transmitter unit from one system inadvertently activating the receiv er station of an adjacent system.This can be effected by arranging for the transmitter units of a particular system to transmit a characteristic code for a particular system and the receiver unit of the system being responsive to that information.

The invention will now be further described with reference to the accompanying drawings, in which: Figure 1 is a schematic view of a stock monitoring system of the invention, Figure 2 is a longitudinal section through the novel acceleration switch of the invention, Figure 3 is a block diagram of a transmitter unit of the system, and Figure 4 is a block diagram of the receiver unit of the invention.

The system schematicaily shown in Figure 1 comprises a receiver station 2 which is arranged to receive radio signals from a transmitter unit 4 mounted on farm stock such as a sheep 6. The system may include any convenient number of receiver units so that these can be mounted on selected animals in selected paddocks to enable a farmer to monitor substantially all of his stock. The arrangement is such that when the stock has been disturbed say by an attacking predatory animal, the transmitter unit carried by disturbed stock will transmit an appropriate alarm signal to the receiver station. The farmer can then take the appropriate action.

The receiver station comprises an antenna 8 receiver circuitry 10 and visual and audio alarms 12 and 14. The circuitry 10 is illustrated in more detail in Figure 4.

A typical transmitter unit 4 comprises an antenna 16, acceleration sensitive switch 18 and circuitry and battery 20. The antenna, switch and circuitry are preferably connected to the sheep 6 by means of a harness which may simply comprise a belt 22. The antenna 16 preferably comprises a flexible wire coil antenna embedded in silicon rubber. The antenna is preferably mounted on the belt 22 near the animal's shoulder and extends rearwardly along the animal's back. The switch 18 can be mounted at any convenient location on the animal but it is preferred to mount the switch somewhere near the shoulder of the animal since it has been found that this location gives a good activation for the switch when the sheep moves from a walking pace to a trotting pace.

The preferred form of acceleration switch of the invention is illustrated in Figure 2. It comprises a metallic tube 24 within which is coaxially mounted a flexible strand 26. An insulating plug 28 is mounted in one end of the tube and it has a bore 30 through which the strand 26 passes. A screw 32 is set into the side of the plug 28 and it provides an adjustable fixing means between the end of the strand 26 and the plug 28.-Thus, the effective length of the strand 26 within the tube 24 can be varied by loosening the screw 32 and moving the strand thus altering the sensitivity of the switch. In the preferred arrangement the strand 26 is metallic and its free end 34 comprises a contact for the switch. It may be provided with a bead of silver to improve its performance.Electric leads 36 and 38 are connected to the strand 34 and tube respectively so as to enable connection of the switch 18 to the battery and circuitry 20.

The arrangement of the switch is such that on acceleration of the switch in directions which are transverse to its axis, the strand 26 will tend to resiliently deflect and at a predetermined accelera tion its free end 34 will contact the inner surface of the tube 24 and this closure of the switch is used to generate an alarm signal for the monitoring system of the invention. It will be appreciated that engagement of the contact 34 with the tube would depend upon the magnitude and direction of acceleration of the sheep, the modulus of elasticity of the strand 26, the length of the strand and the diameter of the tube 24. It has been found that a particularly satisfactory switch can be constructed where the internal diameter of the tube is about 14mm and the length of the tube is about 11 Omm.The strand preferably comprises a wire made up of a number of wound strands of spring steel wire. In particular the wire may comprise a length of wire similar to that used in speedometer cables.

Figure 3 illustrates a preferred arrangement for the circuitry 20 of the transmitter unit 4. The circuitry includes a radio frequency transmitter 36 which receives its power via a line 38, the line 38 is not connected to the battery via a power switch 40 which in turn is dependent upon the acceleration switch 18.

In general terms, the line 38 is not connected to the battery unless the acceleration switch 20 has been activated and then the appropriate signals are radiated from the antenna 16. It is desirable to arrange for the transmitter 16 to send coded signals so that more meaningful information is received at the receiver station 2. In particular, the arrangement of Figure 3 includes circuitry which will enable discrimination of signals from other systems, discrimination of signals generated by different units, generation of signals indicative of correct operation of a particular receiver unit 4 and of battery check signals for each unit 4. To this end, the circuit includes a code converter 42 which is arranged to generate 16-bit digitally encoded signals.The first 11 units can be used as an identification of the system and this can be used to discriminate against signals which might be received by the receiver station from a transmitter of a different system.

The next digital bit of the signal frame may comprise a signal which is generated during a test transmission of the unit and if the receiver unit 20 does not receive a signal with the test transmission bit present within a predetermined time, it will know that one of the transmitter units is not functioning correctly. The next digital bit may comprise a bit which is also transmitted with the test transmission and indicates whether the battery of the unit is sufficiently charged. The final 3 digital bits may be for transmitting identification of the particular unit.

Thus, the system can accommodate 8 transmitter units.

The circuit includes a timer 44 the output of which is connected to the power switch 40 and to the code converter 42. The arrangement is such that the timer produces a periodic output which enables connection of the line 38 to the battery and generation of a signal in the code converter indicating that a test transmission is being performed. The circuit includes a test circuit 46 for monitoring the voltage of the battery and its output is connected to the code converter42 so that during the testtransmission an appropriate bit of information is included which indicates that the battery is sufficiently charged.

Output from the code converter 42 is connected to a modulator 48 the output of which is connected to the transmitter 36. The modulator 48 may take any convenient form such as a frequency modulator or circuitry arranged to produce pulse width modulation or frequency shift modulation. The power switch 40 functions as a bistable circuit so that momentary closure of the acceleration switch 18 will produce a continuous output of the switch 40. A counter 50 is therefore provided to reset the switch 40 afterthe desired information has been transmitted. Output of the counter 50 is connected to the code converter to provide sequential address information.

The circuitry 10 at the receiver station comprises a radio receiver 52, demodulator 54, signal decoder 56 which reproduces the transmitted signal in the form of digital frames corresponding to the output signals of the code converter 42 of the receiver units 4.

Output from the decoder 56 is coupled to a microprocessor 58 which interprets the received signals.

Output from the microprocessor is connected to the visual display 12 and the audio alarm 14. The circuit includes a PROM store 60 which stores a user code which is unique to a particular system and therefore allows discrimination against unwanted signals. The circuit further includes a switching array 62 which inputs information to the microprocessor 58 according to which of the 8 transmitter units 4 is being used at any particular time.

The preferred form of output from the microprocessor 58 is such that it will cause a first LED 64 to be activated and simultaneously sound the audio alarm 14 when it receives a signal indicating that one of the acceleration switches 18 has been activated.

Simultaneously the identity of the unit will be displayed in a 7 segment visual display 68 thereby enabling the farmer to know the location of the stock disturbance. The display 12 further includes a second LED device 68 which will be activated during the test transmission indicating that the particular transmitter unit undergoing the test transmission is performing satisfactorily, the number of that unit being displayed in the display 66. A fhird LED display 70 is provided and this will be activated during the test transmission period when the battery of a unit undergoing test transmission is below a predetermined level.

Many modifications will be apparent to those skilled in the art without department from the spirit and scope of the invention.

For instance, the antenna could be connected to a housing which contains the transmitter circuit 4 and battery.

Claims (11)

1. An acceleration sensitive switch said switch comprising a body within which is mounted an elastically deformable member, said body having a first electric contact associated therewith, the deformable member having a second elastic contact associated therewith, and normally not in contact with the arrangement being such that when the switch is subjected to a predetermined acceleration the manner elastically deforms to a sufficient extent whereby the second contact engages the first contact.

2. Aswitch as claimed in claim 1 wherein the member comprises a strand of flexible material connected at one end to said body.

3. A switch as claimed in claim 2 wherein the strand comprises wound wire.

4. A switch as claimed in claim 3 including mounting means for adjustably connecting one end of the wire to the body.

5. A switch as claimed in claim 2, 3 or 4 wherein the body comprises a metallic tube and the strand extends generally coaxially within the tube, the inner surface of the tube constituting said first electric contact.

6. Astock monitoring system comprising a transmitter unit adapted to be mounted upon an animal, a receiver station for receiving signals transmitted from said transmitter unit, and an acceleration sensitive switch for mounting on the animal and coupled to the transmitter unit, the arrangement being such that the transmitter unit transmits an alarm signal when said switch has been activated.

7. A system as claimed in claim 6 wherein the switch comprises a switch as defined in any one of claims 1 to 6.

8. A system as claimed in claim 6 or 7 wherein transmitter unit includes encoding means for producing signals representative of the identity of the transmitter unit, working status of the unit and said alarm signal, and wherein the receiver station includes decoding means for interpreting said signals.

9. A system as claimed in claim 8 wherein said encoding means additionally produces identification signals representative of the system and the decoding means includes stored information representative of the identity of the system.

10. An acceleration sensitive switch substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

11. A stock monitoring system substantially as hereinbefore described with reference to and as shown in the accompanying drawings.