Flow apparatus

In a flow apparatus for adding liquid additive to drinking water for cattle, a drinking trough (13) is supplied with treated water from a header tank (18) topped up from a mains supply (15) in response to changes in level in the trough (13). A siphon (19) delivers water from the header tank (18) to the trough (13) down a primary tube (20) which is joined by a secondary tube (25) leading from an additive tray (22). Additive is sucked into the primary tube (20) without any substantial venturi effect, and is sucked at least predominately by the effect of displacement of liquid in the primary tube (20) below the junction (27), to ensure accurate dosage of additive. Preferably the primary tube (20) runs full substantially immediately after flow commences in the primary tube (20).

The present invention relates to flow apparatus for, and a method of, 
combining two liquids, and is concerned in particular, but not 
exclusively, with apparatus for adding to a water supply for animals a 
small, regulated quantity of a liquid additive. 
The practice of adding supplements and drugs to the water supply of 
livestock and poultry has been in use commercially for a number of years. 
Examples of such applications are the feeding of coccidiostats at low 
levels to chicks and turkey poults during part of the rearing period, the 
use of anit-foaming agents ("Pluronics") in drinking water in New Zealand 
for control of bloat, and feeding magnesium acetate in the water supply to 
control hypomagnesaemia in cattle. Usually these additives have been 
combined with the water supply manually, but there has recently been 
proposed a proportioning device for metering magnesium acetate solution 
into a drinking trough by use of a venturi effect. In this known device a 
ballcock controls the level of water in a drinking trough, the ballcock 
valve being supplied with water from the mains. In the ballcock valve 
there is included a venturi which draws a liquid additive from an adjacent 
container and mixes the additive with the water entering into the trough 
whenever the ballcock valve is open. Because of the nature of such a 
venturi arrangement, the quantity of additive combined with the main water 
supply is not accurately controlled and is dependent upon the rate of 
water flow past the venturi. This rate of flow may vary with water 
pressure, and the amount of air entrained in the venturi. Furthermore the 
proportion of additive combined at the beginning and end of each flow of 
water when the ballcock opens will be imprecise as the venturi effect will 
vary at the beginning and end of the flow of water. However the addition 
of magnesium acetate to drinking water for cattle requires a proportion in 
the region of 1 to 80. The amount of additive to be combined is not 
critical, and the consequences for the cattle are not severe if the amount 
of additive varies slightly. 
However there are other liquid additives which have been proposed for 
combining with drinking water for cattle but which would require very 
accurate metering of the additive into the drinking water, in order to 
avoid detrimental effects which would arise from an overdose. One example 
is the proposed use of copper sulphate in drinking water for controlling 
either simple or induced copper deficiency in cattle. The use of such an 
additive has not proved possible in practical circumstances since no 
suitable device has been available for metering the additive with 
sufficient accuracy. 
Copper deficiency is widespread in the U.K. and also in many countries 
overseas which depend on pastoral economies. The methods of control of 
copper deficiency in grazing cattle which have been used previously have 
been unsatisfactory for a variety of reasons. Free choice mineral 
supplementation gives inadequate control, as demonstrated by a recent 
trial in which observations showed that 40% of the animals in the trial 
did not consume sufficient of the mineral to bring blood coppers to a 
level which would be considered adequate. This trial confirmed reports 
from farmers that the free choice supplementation system was not 
controlling the problem of copper deficiency. The injection of copper 
complexes is unsatisfactory because this method requires the injection to 
be repeated at intervals at a frequency depending upon the factors which 
have caused the deficiency. The repeated injections in turn involve 
individual handling of the animals, which handling is expensive, time 
consuming and on some occasions impracticable. Up to the present date, 
there has not been available any metering device having sufficient 
accuracy to be practicable for adding a liquid copper sulphate additive to 
drinking water. 
According to the present invention there is provided flow apparatus 
comprising supply means for providing a supply of a primary liquid, a 
primary tube communicating with the supply means for delivering primary 
liquid from an inlet of the primary tube to an outlet of the primary tube, 
the said outlet being situated at a lower level than the said inlet, a 
container for a secondary liquid, and a secondary tube leading from an 
inlet thereof communicating with the said container to a junction of the 
secondary tube with the primary tube for sucking secondary liquid from the 
container in the primary tube upon flow of primary liquid through the 
primary tube, the said junction being situated between the inlet and the 
outlet of the primary tube and at a level higher than the inlet of the 
secondary tube, the arrangement being such that in operation the rate of 
flow of primary liquid past the junction is less than that required to 
cause any substantial venturi effect, and the secondary liquid is sucked 
into the primary tube at least predominantly by the effect of displacement 
of the liquid in the primary tube below the said junction. 
Preferably there is provided in the primary tube a restriction or choke 
extending along the primary tube over a region including the junction of 
the secondary tube with the primary tube. Preferably the restriction is 
such as to reduce the radius of the primary tube in the said region to a 
value lying in the range of one-half to three-quarters of the radius of 
the primary tube outside the said region. 
Preferably the said outlet of the primary tube is arranged during operation 
to be open to atmospheric pressure, and preferably the capacity of the 
primary tube below the said junction is greater than the capacity of the 
secondary tube. Where a constriction is provided, it is preferred that the 
capacity of the primary tube below the said junction is greater than the 
sum of the capacity of the secondary tube and the capacity of the 
restricted region of the primary tube. 
Preferably the junction of the secondary tube with the primary tube 
comprises an extension of the secondary tube which extends into the 
interior of the primary tube, preferably at right angles to the primary 
tube. Preferably the secondary tube extension terminates substantially at 
the centre of the interior of the primary tube, and preferably the end of 
the secondary tube extension has an end face at an angle, preferably 
45.degree., to the axis of the secondary tube extension. Conveniently the 
secondary tube extension may comprise a hypodermic needle. 
Preferably the container for the secondary liquid (the secondary container) 
is open to the atmosphere at its top and has the inlet of the secondary 
tube positioned at or near the bottom of the secondary container at a 
level below the level of secondary liquid in the secondary container 
maintained during normal operation. Preferably there is provided a 
secondary liquid reservoir with a metering device arranged to maintain the 
level in the secondary container at a substantially constant level during 
operation. 
In a convenient arrangement according to the invention, the said supply 
means includes control means for flowing along the primary tube a 
predetermined quantity of primary liquid, the dimensions of the primary 
and secondary tubes and the general arrangement of the apparatus being 
selected to be such that when the control means passes down the primary 
tube the said predetermined quantity of primary liquid the primary tube 
runs full substantially immediately that the control means begins to pass 
the primary liquid. In particular, where a restriction (sometimes called a 
choke) is provided in the primary tube, the restriction is preferably 
sufficiently narrow to ensure that suction commences immediately through 
the secondary tube upon flow of primary liquid in the primary tube, and 
yet is sufficiently wide to allow enough flow down the primary tube to 
ensure that the primary tube runs full as soon as a flow of primary liquid 
commences down the primary tube. 
Preferably the said supply means comprises a container for primary liquid 
(the primary container) positioned with the inlet of the primary tube 
communicating with the primary container at or near the bottom of the 
primary container, and having control means for allowing a controlled flow 
of primary liquid from the primary container down the primary tube by 
means of gravity. Preferably the control means comprises a self-priming 
syphon arranged to syphon at intervals a predetermined quantity of primary 
liquid down the primary tube. Conveniently the syphon may be arranged to 
operate whenever the level of primary liquid in the primary container 
rises to a predetermined level. Primary liquid may be fed to the primary 
container continuously or under a further flow control means. 
In a particular application of the invention, for example for adding a 
liquid additive to drinking water for cattle, there is provided a third 
container for receiving the mixture of primary and secondary liquids, the 
third container being open to the atmosphere at its top, and being 
positioned to receive the mixture of liquids from the outlet of the 
primary tube, the third container being provided with a further control 
means, for example a ballcock, for passing a flow of primary liquid from a 
source, such as mains water, to the said primary container whenever the 
level in the third container falls below a predetermined minimum. In such 
a preferred arrangement, the further control means is arranged to feed 
primary liquid to the primary container when the level in the third 
container falls below the said minimum level, and continues to pass 
primary liquid to the primary container until the first mentioned control 
means passes a charge of primary liquid down the primary tube to restore 
the level in the third container above the said minimum level. In this way 
at intervals the third container is replenished from time to time as 
necessary with the required mixture of primary and secondary liquid. In 
the application of the present invention to the adding of a liquid 
additive to drinking water for cattle, the third container constitutes a 
drinking trough, the primary liquid is constituted by water, and the 
secondary liquid is constituted by the liquid additive. Thus in accordance 
with a particularly preferred arrangement according to the invention the 
said supply means comprises a primary container for primary liquid and 
there is provided a third container for receiving the mixture of primary 
and secondary liquids from the outlet of the primary tube, the said 
primary container being provided with first control means for allowing a 
controlled flow of primary liquid from the primary container down the 
primary tube, the said first control means being arranged to operate 
whenever the level of primary liquid in the primary container rises above 
a predetermined level, and the said third container being provided with 
further control means for passing a flow of primary liquid from a source 
of primary liquid to the primary container whenever the level of liquid in 
the third container falls below a predetermined level, the further control 
means being arranged to continue to pass primary liquid to the primary 
container until the first mentioned control means passes a charge of 
primary liquid down the primary tube to restore the level in the third 
container above the said minimum level. Again where such an arrangement is 
used for the adding of a liquid additive to drinking water for cattle, the 
third container constitutes a drinking trough, the primary liquid is 
constituted by water, and the secondary liquid is constituted by the 
liquid additive. 
There is also provided in accordance with the present invention a method of 
combining two liquids comprising the steps of flowing down a primary tube 
a primary liquid past a junction of the primary tube with a secondary 
tube, sucking through the secondary tube into the primary tube a secondary 
liquid from a container for secondary liquid, and delivering at an outlet 
of the primary tube a mixture of the two liquids, the said primary liquid 
being flowed past the said junction at a rate of flow which is less than 
that required to cause any substantial venturi effect, and the secondary 
liquid being sucked into the primary tube at least predominantly by the 
effect of displacement of the liquid in the primary tube below the said 
junction. 
Preferably the said primary liquid is flowed down the primary tube by 
gravity, and preferably the said outlet of the primary tube is open to 
atmospheric pressure. Preferably the step of flowing the primary liquid 
past the said junction comprises flowing the liquid through a restriction 
or choke extending along the primary tube over a region including the 
junction. 
Preferably the primary liquid is flowed down the primary tube at a rate 
such that the primary tube runs full substantially immediately after 
commencement of the flow. Preferably the suction effect at the secondary 
tube is arranged to be sufficient for the suction tube to run full 
substantially immediately after the commencement of primary flow past the 
said junction.

Referring initially to FIGS. 1 to 3, a flow apparatus 11 suitable for 
example for adding copper sulphate in the form of a liquid additive to 
drinking water for cattle, comprises a main frame 12 supporting a number 
of liquid containers and flow tubes. At the base of the frame 12 a 
drinking trough 13 is fitted with a Garston-type ballcock for controlling 
a supply of water passing into the valve of the ballcock 14 from a pipe 15 
coupled to the mains water supply. An outlet from the ballcock valve 16 
passes up a further pipe 17 to a header tank 18 supported at the top of 
the main frame 12. 
In the header tank 18 is provided an automatic self-priming syphon (which 
may be for example an Enfield Automatic Urinal Syphon BS 1876) having an 
outlet coupled to the top of a primary tube 20. The primary tube 20 has 
its inlet coupled to the syphon 19 and has an outlet 21 leading to the 
drinking trough 13 but positioned at a height greater than the maximum 
level of liquid in the drinking trough 13 during normal operation. 
The main frame 12 also supports at about the middle of its height a tray 22 
arranged to contain a liquid additive, for example copper sulphate. Above 
the additive tray 22 is provided an additive reservoir 23 having in its 
base a control device 24 arranged to maintain the level of additive in the 
tray 22 at a predetermined substantially constant level. 
Associated with the additive tray 22 is a secondary tube 25 which leads 
from an inlet 26 of the tube 25 to a junction 27 of the tube with the 
primary tube 20. The inlet 26 of the tube 25 is positioned close to the 
bottom of the additive tray 22 and is arranged to be always below the 
level of liquid additive in the tray 22. 
Referring now to FIG. 4 the primary tube 20 includes a restriction or choke 
28 coupled into the tube 20 by an upper compression cap nut 29 and O-ring 
seal 30 and by a lower compression cap nut 31 and lower O-ring seal 32. In 
this description the primary tube 20 is taken to be the entire tube 
including the components of the choke 28. 
The secondary tube 25 joins the primary tube 20 at the junction 27 by way 
of a secondary tube extension 33 which enters the choke 28 at right angles 
to the axis of the choke conduit. Conveniently the secondary tube 
extension 33 comprises a hypodermic syringe needle. Conveniently the 
syringe needle 33 terminates substantially at the centre of the interior 
of the choke 28, and has an end face 34 at 45.degree. to the axis of the 
syringe needle 33, facing downwardly. 
There will now be described a summary of the operation of the embodiment 
shown in the Figures. When the level of water in the drinking trough 13 
falls as the animals drink, the float of the ballcock 14 falls and allows 
water to flow up the pipe 17 to the header tank 18. This water continues 
to flow until the level in the header tank 18 is sufficient to prime the 
automatic syphon 19 which then discharges an approximately predetermined 
quantity of water down the primary pipe 20 into the drinking trough 13. It 
is not necessary that this quantity of water passing is accurately 
regulated. As the water flows through the restriction 28, the liquid 
additive is sucked up the secondary tube 25 from the additive tray 22 and 
is added to the liquid passing down the lower part of the primary tube 20 
into the drinking trough 13. 
The feature of the construction and method of operation of the device 
described which embodies the invention is that the rate of flow of liquid 
past the junction 27 is arranged to be less than that required to cause 
any substantial venturi effect at the end face 34 of the needle 33, and 
the arrangment is such that the additive from the tray 22 is sucked into 
the primary tube at least predominantly by the effect of displacement of 
water in the primary tube 20 below the junction 27. Examples of the 
dimensions of the elements, and the materials for construction, which may 
be used will be given hereinafter, but these factors are chosen in the 
example shown in such a manner as to produce substantially no venturi 
effect at the junction 27, and to effect the suction in the secondary tube 
25 substantially wholly by displacement of liquid in the primary tube 20 
below the junction 27. It is important to the working of the system that 
the water in the primary tube 20, having passed through the choke 28, is 
in sufficient volume to fill completely and instantly the part of the 
primary tube 20 below the junction 27. This is to ensure that the column 
of water dropping down the lower part of the primary tube 20 produces 
negative pressure in the choke conduit 28 so that the liquid additive in 
the tray 22 is immediately sucked into the choke 28 along the tube 25. The 
balance between the capacity of the primary tube 20 below the junction 27 
and the capacity of the sum of the choke 28 and the secondary tube 25 must 
be carefully selected. Too narrow a choke 28 will not allow the lower part 
of the primary tube 20 to fill quickly enough to act in the manner of a 
piston of a displacement pump. Too large a diameter of the choke 28 will 
not create sufficient suction to prime the secondary tube 25 immediately 
the flow through the primary tube 20 commences. Since the proportion of 
additive added to the drinking water depends upon the flow in the 
secondary tube 25 in relation to the flow in the primary tube 20, this 
relationship can only be maintained constant if both the lower part of the 
primary tube 20, and the secondary tube 25, both run full immediately a 
downflow of water through the primary tube 20 commences. The operation of 
the liquid falling in the primary tube 20 as the "piston" of a 
displacement pump contrasts with the effect which occurs in known additive 
metering devices where the additive is added to the main flow by a 
venturi. Where a venturi is used the main tube does not run full, and the 
amount of additive sucked into the main tube varies with flow through the 
venturi, with the result that considerable variation in the proportion of 
additive added occurs. In the embodiment of the invention shown, where it 
is arranged that both the primary tube 20 and the secondary tube 25 run 
full immediately a flow starts through the primary tube 20, ensures that 
the proportions of additive flowing up the tube 25 to the main liquid 
flowing down the tube 20 are maintained constant. 
The fact that the secondary tube 25 draws the additive from the additive 
tray 22 at a lower level than the junction 27 ensures that no additive can 
reach the drinking trough 13 unless the primary tube 20 is running full. 
This provides a fail-safe feature of the system in that the concentration 
of additive cannot rise above the predetermined level. The required 
concentration of additive in the trough 13 is conveniently adjusted by 
altering the concentration of the solution in the additive reservoir 23. 
Examples will now be given of dimensions of, and materials used for, the 
various elements of the embodiment described. The frame 12 is conveniently 
of a size such as to provide 6 foot head of water which can be provided by 
a mains pressure above 21/2 lbs p.s.i. Provided the mains pressure is 
above this limit, the system is independent of variations in the pressure 
of the incoming water. This is in contrast to a known venturi type of 
additive injector where the amount of additive injected by the venturi is 
dependent upon variations in the pressure of the incoming water. The main 
parts of the primary tube 20 are conveniently constructed of 3/4 inch 
polythene piping and the choke portion 28 of the primary tube 20 is 
conveniently a 3 inch long (external dimension) nylon tube having an 
internal restricted diameter of about 10 mm, for example 10.3 mm. The 
included angle at the top and bottom of the choke 28 in the internal 
profile may be 60.degree., and the needle 33 conveniently enters the choke 
28 at a distance 3/4 inch above the beginning of the restricted portion, 
that is to say at the lower edge of the chamferred part of the profile. 
The total length of the effective part of the choke 28, that is to say 
between the beginnings of the chamferred inlet and outlet, is conveniently 
21/2 inches. It is found that in general the junction 27 should be 
positioned lower than half way down the choke and higher than a quarter 
way up the choke. As shown an optimum position is two-thirds of the way 
down the effective length of the choke. 
Conveniently the hypodermic needle may be a standard 18 s.w.g. needle and 
the secondary tube 25 is conveniently a Portex 800/000/150 pick-up tube. 
Such a tube has an internal diameter of 1.4 mm. Conveniently the lower 
portion of the primary tube 20 below the choke 28 is formed of standard 
1/2 inch polythene tubing of British Standard BS 1972 type C. The upper 
portion of the primary tube 20 is conveniently of standard 3/4 inch 
polythene tubing of British Standard BS 1972 class C. The additive tray 22 
is supplied conveniently from a 5 gallon additive reservoir 23 which is 
inverted over the tray and feeds it through a 1/4 inch hard plastic tube 
sealed by a rubber grommet into the conventional screw cap of such a 5 
gallon additive reservoir. In such a case the said metering device 24 for 
keeping a constant level in the tray 22 merely consists of the said hard 
plastic tube. The tube allows additive liquid to flow from the reservoir 
23 into the tray 22 only when the level in the tray 22 falls below the end 
of the tube 24. 
By way of example the embodiment shown is suitable for adding up to 2 
microgrammes per milliliter of copper to the drinking water of grazing 
cattle, which level has been shown experimentally to be adequate for 
controlling induced copper deficiency in cattle on a semi synthetic diet. 
Where daily small supplements of cobalt and selenium are required it is 
also possible to provide these with a similar apparatus. The system can 
also be used for low level drug or trace element supplementation for 
housed animals, using the trough as a supply tank for water bowls or 
constant level drinkers. The addition of nutrient solutions to irrigation 
water in glasshouse crops (e.g. tomatoes) may also be effected by an 
embodiment of the invention. 
When tested with additive solutions giving a mean copper concentration in 
the drinking trough of 0.85 microgrammes per milliliter, the standard 
deviation of copper in successive fillings of the trough was .+-.0.02 
microgrammes per milliliter. 
In an alternative embodiment the following values of concentrations were 
obtained in a test using a 23/64 inch choke with a 16 s.w.g. needle at the 
junction of the primary and secondary tubes. Duplication of concentration 
of copper in the drinking water was found to be excellent. 
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Additive Concentration 
Drinking Water Concentration 
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200 microgrammes per ml. 
1.44 microgrammes per ml. 
1.44 microgrammes per ml. 
1.43 microgrammes per ml. 
1.45 microgrammes per ml. 
1.44 microgrammes per ml. 
1.42 microgrammes per ml. 
1.80 microgrammes per ml. 
1.78 microgrammes per ml. 
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Thus embodiments of the present invention can be constructed which provide 
a system to ensure that animals using the system are forced to ingest the 
required additive element at the correct level, the system being simple 
and cheap. The system requires virtually no maintenance other than filling 
the additive reservoir, and includes a fail-safe feature to prevent excess 
proportions of additive being added to the drinking water. Furthermore the 
system requires no external power supply, permitting it to be used in most 
field conditions.