Animal drench

There is provided a transducer arranged to identify the body weight of each animal, the transducer providing a voltage signal which is amplified to drive a motor of an electrically operated pump which pumps drenching chemical to a handpiece, the handpiece having a discharge tube which is inserted in an animal's mouth.

This invention relates to a device which is useful for the "drenching" of 
an animal, that is, assisting an operator to apply the correct quantity of 
medication to an animal by injecting it into the animal's mouth. 
BACKGROUND OF THE INVENTION 
It is often required to provide an oral drench to livestock to control 
internal parasites and other maladies. Sheep are usually drenched twice 
per year, and goats about four times per year. 
It is necessary that the drench chemical should be administered in a volume 
which varies according to the weight of the animal, and in most instances 
is approximately proportional to that weight. Because the hand-operated 
drenchers which are presently used require to be preset for any one 
volume, it becomes necessary to muster and separate the flock into size 
groups (sheep, lambs, etc.) before drenching. 
In some instances however an operator will rely upon his judgement and not 
separate the flock, but give a reduced amount from the drenching gun to a 
smaller animal by not fully operating a control lever on the handpiece 
(sometimes called a "gun"). This often results in an inappropriate dose, 
and either an ineffective drench or, if excessive drench chemical is 
applied, the possibility of damaging or even killing the animal. 
In flocks of angora goats for example, the size variation is very evident 
for various age groups, and there is a large variation in weight between 
young kids and adult goats. 
Hand-operated drench guns as presently used cause hand fatigue, as a strong 
return spring is required in order to pump the thick solution of drench 
chemical into the gun before the gun trigger is operated, and this spring 
pressure must be overcome by hand. 
The main object of this invention is to provide means whereby a flock of 
mixed animals can be appropriately drenched without first separating the 
animals into weight/size groups, and to be able to administer the correct 
amount of drench chemical per animal. This will not only be effective in 
controlling parasites, but also avoid overdrench and possible damage to 
the animal. 
It is a second object of the invention to provide improvements whereby 
operator fatigue can be reduced, and to provide a means whereby little 
effort only is required to operate a pump mechanism of a drenching gun or 
other handpiece. 
It is a still further object of the invention to provide means whereby an 
animal's weight and drench dosage is recorded so as to assist in effective 
livestock management. 
BRIEF SUMMARY OF THE INVENTION 
In this invention, there is provided a transducer arranged to identify the 
body weight of each animal, the transducer providing a voltage signal 
which is amplified to drive a motor of an electrically operated pump which 
pumps drenching chemical to a handpiece, the handpiece having a discharge 
tube which is inserted in an animal's mouth. 
There is also provided a regulating circuit which limits the dosage of 
drenching chemical administered by the pump, by stopping the pump motor 
when a dosage is administered which is a proportion of the animal's 
weight. 
More specifically, in this invention an animal drench device consists of 
animal support means, a weight responsive transducer at least partly 
supporting the weight of an animal, a drenching handpiece having a 
discharge tube, a drench dosage pump, a hose between the drenching 
handpiece and the dosage pump, an electric motor coupled to the dosage 
pump and operable to actuate the pump to force a dosage of drenching 
chemical to and through the discharge tube of the drenching handpiece, a 
switch on the drenching handpiece, and an electrical circuit 
interconnecting the transducer, switch and motor, the electrical circuit 
comprising amplifier means which amplify a transducer signal responsive to 
increase of weight imposed on the transducer, said amplified signal 
driving the motor, the electric circuit also comprising regulating means 
which control said motor drive to limit said dosage in response to said 
weight increase. 
In one embodiment of the invention, coupling means couple the weighing 
means and the drenching means into an electronic memory for information 
retrieval by a computer system. 
The motor can be a rotary electric motor, and the dosage pump a piston pump 
coupled to the motor shaft by a screw-and-nut assembly, but in another 
embodiment the motor can be a stepping motor, the number of revolutions 
being proportional to animal weight. Alternatively, the transducer signal 
can control time of motor operation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring first to FIG. 1, an animal to be drenched is placed on a weighing 
platform 10 which is at least partly supported by a transducer 11, the 
transducer 11 providing an electrical output which is dependent upon, and 
in this embodiment proportional to, the increase in apparent weight of the 
platform 10. Amplifier 12 amplifies the transducer output and produces a 
signal voltage between 0 and +5 volts over the desired weight range. Power 
supply 52 (FIG. 1a) supplies -5 V, 0 V, and +5 V to the correspondingly 
marked elements of the circuit of FIG. 1. Similarly power supply 53 (FIG. 
1b) supplies -12 V, 0 V, and +12 V to the correspondingly marked elements 
of the circuit of FIG. 1. 
The amplified signal voltage is transferred to capacitor 13 via switch 14, 
this being a normally closed switch. The voltage on capacitor 13 will 
therefore smooth the fluctuating weight transducer output and follow the 
voltage signal proportional to the weight as detected by the transducer 
11. The capacitor 13 is of the low internal leakage type. 
Amplifier 15 is a voltage follower, producing a high impedance to the 
voltage across capacitor 13, and therefore reproducing the signal voltage, 
and its output goes into a variable control potentiometer 16, as well as 
driving the calibrated weight meter. The output of potentiometer 16 is a 
proportion of the signal voltage, enabling a scaling of the control 
voltage as a proportion of the weight range. The potentiometer 16 setting 
therefore sets the dose rate (0.0 to 0.2 ml/Kg). Amplifier 17 produces a 
high impedance to potentiometer 16, buffers the output of potentiometer 
16, and drives the dose rate meter (which may have a low impedance). The 
two meters provide an immediate visual check. 
The output voltage of amplifier 17 is proportional to the weight and is fed 
to a normally open switch 18 which is an interconnecting switch. When 
closed, switch 18 will transfer the control voltage to servo-amplifier 19, 
which is configured as a conventional input-summing amplifier, that is, 
the output voltage will swing in such a polarity and amplitude as to cause 
a return current to flow back into its input so as to cancel any current 
caused by an input voltage impressed across the input resistor 20. In this 
configuration the return current is limited, and the amplifier output 
voltage swing is unable to impress enough current to cancel out the input 
current, causing the output voltage swing to reach its maximum possible 
value. 
This output voltage will cause the motor 21 (a DC servo motor) to rotate in 
one direction. Without further control, the motor 21 would keep running, 
however its shaft is coupled to a screw thread 22 in turn coupled to a 
linear potentiometer 23. 
The rotation of motor 21 will therefore cause the output voltage of 
potentiometer 23 to rise, as it is moved by the screw thread 22. 
The voltage of the linear potentiometer 23 is transferred by the buffer 
amplifier 24 through a resistor to the input of servo-amplifier 19, in 
such a polarity as to cause a cancellation of the input voltage across the 
input resistor 20. 
As the movement of the motor, in driving the linear potentiometer 23, 
causes the output voltage of the servo-amplifier 19 to decrease, the motor 
slows, until a point of stabilisation is reached at which the output 
voltage of servo-amplifier 19 is insufficient to rotate the motor. 
The motor 21 will then have moved the mechanical screw thread nut 25, and 
thereby the wiper of linear potentiometer 23, by such a distance as to 
cause the output voltage to be sufficient to cancel the input voltage 
across the resistor 20. 
The voltage across resistor 20 will therefore control the travel position 
of the nut 25 on the screw thread 22. 
When the voltage across input resistor 20 is returned to zero, the voltage 
from the linear potentiometer 23 will have correspondingly increased and 
will cause the servo-amplifier 19 to reverse its output voltage, causing 
the motor to return the potentiometer 23 to its original position where it 
has an output of zero volts. 
The output of servo-amplifier 19, in moving the motor and the feedback 
potentiometer 23 in response to an input signal, is a conventional 
servo-control mode. 
When an animal is placed on the weighing platform 10, it will at times 
cause an erratic reading of the weight due to its movement. Switch 14 is 
opened at such a time that the animal is reasonably still and thereby the 
voltage across the capacitor 13 is held at its then value, irrespective of 
further movement of the animal on the platform. This voltage will be held 
quite constant since a capacitor 13 has low leakage, and amplifier 15 has 
a high input resistance. 
A proportion of the weight signal is set by the control potentiometer 16 in 
order to control the required dose rate, since the amplitude of the 
control voltage will result in controlling the distance the motor moves 
the threaded nut 25, and thereby the resultant amount of drench which is 
administered. 
Normally open switch 18 is then closed for a set period (in this embodiment 
one second) during which time the motor will move to a corresponding 
position set by control voltage. 
At the end of this time period, when the switch 18 opens, the motor will 
return to its zero position. 
Therefore the weight of the animal on the platform will cause the motor to 
move the screw thread nut 25 by a distance which is proportional to the 
animal's weight, the proportion being set by the control potentiometer 16. 
Reference is now made to the mechanical pump which is diagrammatically 
illustrated in FIG. 2. 
In order to facilitate the movement and cause the correct amount of drench 
to be injected orally into the animal, the threaded nut 25 is coupled to 
piston rod 29 of a piston pump 30 as shown in FIG. 2. 
The DC servo motor 21 has its shaft 22 threadably engaged by the nut 25 as 
described above. Rotation of the shaft therefore causes the nut 25 to move 
in a linear movement. The finger 31, extending through a slot in a support 
sleeve 32, prevents the nut from rotating. The finger 31 also drives the 
wiper of feedback potentiometer 23 as described above. The piston rod 29 
is coupled to nut 25 which axially moves the piston 33 inside a cylinder 
34. The cylinder 34 is directly in fluid flow communication with the pump 
head 35, the head 35 comprising an inlet non-return valve 36 and an outlet 
non-return valve 37. 
The control voltage developed by transducer 11 due to the weight of an 
animal will cause the motor 21 to rotate in such a direction as to drive 
the piston into the cylinder, lift the valve 37, and drive the drench 
chemical into the handpiece 40, through hose 41. A return to zero control 
voltage will cause the piston 33 to retract, producing a vacuum and 
drawing more drench through valve 36 into the pump head 35, from the 
reservoir 42. 
For the purposes of livestock control, the circuit of FIG. 1 embodies logic 
and data storage facilities. A small microprocessor 44 of known type is 
used to facilitate the timing control of the switches 14 and 18, when 
required by the switch 45 located on the drench handpiece handle in a 
sequence previously decribed. 
In addition, the microprocessor is used to store information relative to 
the drenching operation for future recall and analysis by a livestock 
management programme. The computer records the weight output of the 
amplifier 15 and the dose setting of the amplifier 17, by using an 
analogue to digital converter, in response to the trigger switch 45 being 
activated. 
In addition, three ten-position switches 47, 48 and 49 selectively produce 
one of ten voltages to three respective analogue inputs of the computer 
44, allowing a "3 digit" number to be read by the computer. 
When the drench handpiece trigger switch 45 is closed, the computer 44 will 
record the weight, the relative dose setting and the code number set up by 
the three switches 47, 48 and 49. This information is then transferred to 
a portable memory unit 51 to facilitate later recall. At the same time, 
the computer 44 causes closure of switch 18 to activate the 
servo-amplifier 19 as described above. 
A remote key pad 50 can be used also to enter other numerical data relative 
to each animal, the computer correlating all the data, referring it to 
that animal. 
Other automatic numeral entry can also be used, for example "bar code" 
words etc. to automatically read an animal's ear tag number. 
It is clearly an equivalent of the above device to substitute a pneumatic 
cylinder for the electric DC servo motor, controlled however in a similar 
manner, or for the switch 45 to be a pneumatic switch which remotely 
controls an electrical slave switch. 
The device herein has been described as an "animal drench", since this 
application is its primary use. However, it will be clear to those skilled 
in the art, that by merely changing the setting of the dosage 
(potentiometer 16), and having an appropriate head on the handpiece (for 
example the discharge tube being a hypodermic syringe), the device can be 
used for ruminant injection through the stomach wall of cattle, for 
innoculation, and for external applications for control of lice.