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(11) | EP 0 249 496 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Liquid mixing apparatus |
| (57) Liquid mixing apparatus for continuously mixing and delivering a concentrate with
a diluent comprises a first reservoir (1, 21) for a first liquid, at least one further
reservoir (11, 31) for another liquid which is to be mixed with the first liquid and
continuous dosing means (5, 6, 7, 8, 9, 10; 25, 26, 27, 28, 29, 29ʹ, 30, 35, 39) comprising
a delivery duct (5, 6, 7, 8; 25, 26, 27, 28) through which the first liquid may be
discharged from the first reservoir and at least one branch duct (9, 10; 29, 29ʹ,
30, 35, 39) leading from the or each further reservoir and joining the delivery duct
at a point intermediate its ends enabling in use the entrainment of the other liquid(s)
by the first liquid and mixing thereof within the delivery duct whenever the first
liquid is caused to flow from the first reservoir through the dosing means which may
be a syphon or venturi system. The apparatus is useful for preparing and delivering
sheep dip, insecticides, or other liquid mixtures requiring careful control of concentration
and regulated delivery. |
[0001] This invention relates to a device for mixing at least one liquid with another, particularly a concentrate with a diluent. The invention is especially useful for continuously topping up a treatment bath, such as a sheep dip.
[0002] When treating sheep to control parasites the most convenient way to carry out the treatment is to cause the sheep to enter a treatment bath. During the course of treatment the bath must be topped up at intervals with insecticide and water to replace that carried off by treated sheep. Conventionally, methods involving topping up lead to fluctuations in concentration. This means that some sheep receive a higher concentration of insecticide than is actually required, and some may receive insufficient treatment. In order to compensate for these fluctuations, it is necessary to add excessive quantities of concentrate in an effort to maintain a level of concentration which does not fall below that required to treat a sheep effectively. This is not cost efficient. Additionally, handling of heavy containers of concentrated insecticide during topping up is wearisome and occupies at least some of the time of a worker, who might be more usefully employed on flock control.
[0003] A known device which is intended to automatically top up a sheep dip with an aqueous solution of insecticide at the correct concentration comprises a pair of balanced pans located beneath an overhead central water supply and each connected to a reservoir of concentrated insecticide. The operation of the device is such that after an initial manual priming of the device with insecticide, the water supply is continually switched from one pan to the other by the action of the heavier filling pan falling to a discharge position whilst the lighter discharged pan rises. The falling pan is also used to pump a measured quantity of concentrate into the rising empty pan.
[0004] This device, which is a constant replenishment device, has advantages over the traditional methods in that a particular concentrate can be delivered in a diluent at an effectively constant level. However, it has several moving parts which could fail if the device did not receive adequate maintenance and it does require manual priming. Further, it is not readily adaptable to deliver different concentration levels, or to operate at different delivery rates.
[0005] An object of this invention is to obviate or mitigate the disadvantages of traditional methods and provide a simple but effective liquid mixer, which can replenish the dipping bath continuously.
[0006] Accordingly this invention provides liquid mixing apparatus which comprises a first reservoir for a first liquid, at least one further reservoir for another liquid which is to be mixed with the first liquid and continuous dosing means comprising a delivery duct through which the first liquid may be discharged from the first reservoir and at least one branch duct leading from the or each further reservoir and joining the delivery duct at a point intermediate its ends enabling in use the entrainment of the other liquid(s) by the first liquid and mixing thereof within the delivery duct whenever the first liquid is caused to flow from the first reservoir through the dosing means.
[0007] Preferably, the first reservoir has a liquid supply inlet provided with liquid supply control means to provide for automatic filling of the first reservoir with liquid to a predetermined maximum level. Conveniently, a float operated valve is used to regulate filling of the first reservoir,
[0008] It will be appreciated that the said further reservoir(s) may or may not contain the same liquid. Therefore the apparatus of this invention is suitable for mixing of two or more liquids.
[0009] According to a preferred form of the invention the apparatus comprises a syphon conduit having an inlet end opening into the first reservoir at a level intermediate the predetermined maximum level and the minimum level of liquid in the first reservoir, said syphon conduit forming part of the duct for delivering liquid from the first reservoir and having a looped portion to which a further liquid is introduced from a further reservoir via a branch duct connected between the said further reservoir and said syphon conduit, the arrangement in use providing for the induction of a further liquid through the branch duct into an upper part of the looped portion of the syphon conduit whilst the first liquid is syphoned from the reservoir thereby introducing the further liquid into the first liquid and causing mixing thereof in the syphon conduit.
[0010] Preferably, the looped portion of the syphon conduit is positioned in said first reservoir in a generally upstanding manner such that the upper part of the looped portion is substantially level with the inlet of the said syphon conduit.
[0011] Preferably also, said branch duct adjoins said syphon conduit at the uppermost part of the looped portion and is most preferably located slightly downstream of the highest point in said looped portion so that liquid introduced to said syphon loop tends to fall into the downstream part of the syphon loop.
[0012] Advantageously, the further reservoir is a vessel of high liquid surface area to low liquid depth ratio which is located within the first reservoir at a position substantially level with the uppermost part of the looped portion of the syphon conduit so that gravity plays little or no part in the introduction of the further liquid from the further reservoir to said syphon loop. Preferably, the branch duct has a curved portion rising above the level of connection with the further reservoir and the said syphon loop to avoid the possibility of draining of the further liquid into the syphon conduit should it become filled with air as a result of a break in the syphon effect should the first liquid supply fail, for example. Alternative branch ducts of larger or smaller diameter may be substituted to vary concentration of mixed liquids.
[0013] In further preferred embodiments of the invention, the delivery duct comprises a venturi tube connected to the first reservoir at a suitable location to provide at least part of the delivery duct for drainage of liquid from the first reservoir and at least one branch duct connected to the further reservoir(s) and communicating with the venturi tube via at least one orifice adjacent to, and downstream of the vena contracta whereby a liquid contained in the further reservoir(s) will be caused to mix with a first liquid flowing through the venturi at a sufficiently high flow rate. The flow rate required will depend on the liquids used and may be predicted from knowledge of the specific gravity of the respective liquids or determined by elementary trial and experimentation. The first reservoir will normally contain a bulk volume of diluent whilst the further reservoir(s) will contain concentrate. At extremely low flow rates, say up to 5 litres per minute of mixture it may be necessary to create a head of concentrate. This would normally be necessary using water as the diluent with concentrates of lesser specific gravity but would probably be unnecessary where the diluent had a specific gravity of less than 1 or in any case less than that of the concentrate(s). Thus the invention is particularly useful in the preparation of aqueous solutions but is also applicable in the preparation of organic mixtures and solutions such as in the mixing of insecticide with diesel as a fogging agent, for example.
[0014] A convenient way of providing the head required at low flow rates is to provide a flotation chamber within the first reservoir to which the reservoir(s) for the other liquid(s) together with appropriate levelling and stabilising means may be attached whereby the reservoir(s) may be caused to maintain a constant head by floating upon and following the level of the first liquid in the first reservoir.
[0015] One way of controlling concentration of the mixture is by varying the orifice through which the second or further liquids pass into the dosing means, which may be achieved by providing exchangeable orifice plates or a manifold feeding multiple orifices.
[0016] The apparatus may include a plurality of venturi tubes to provide additional flexibility in control of mixture flow rates and concentration.
[0017] Inclusion of metering valves at appropriate points in the branch ducts may in some instances be desirable.
[0018] The invention will now be described by way of example with reference to the accompanying drawings in which:-
Fig. 1 shows a schematic representation of an embodiment of the invention, as described in Example 1;
Fig. 2 is a side sectional view of a further embodiment of the apparatus of this invention which is described in Example 2;
Fig. 3 is an end view of the embodiment of the apparatus of this invention shown in Fig. 2.
Fig. 4 is a graph showing the results of trials of the apparatus of this invention at various flow rates; and
Fig. 5 is a graph showing results of further trials of the apparatus of this invention at various flow rates.
Example 1
[0019] This embodiment is designed to supply concentrated sheep dip from a shallow planar-configuration reservoir to be diluted with water held in a larger bulk reservoir. The apparatus comprises a suitably supported water reservoir (1) having an inlet (2) in an upper region through which a water supply is controlled by means of float operated valve (3, 4) such as a ball cock, and a drain (12). In the reservoir (1) there is provided an upstanding syphon pipe (5) having a looped portion (15), an inlet end (6) opening into the reservoir (1) at a level beneath the surface of the water normally maintained in the reservoir in use and an outlet end (7) including a tap (8) providing a duct for delivering mixed sheep dip solution from the apparatus. The looped portion (15) of the syphon pipe (5) is connected to a shallow second reservoir (11) by a replaceable narrow bore duct or tubing (9) including a tap (10). The tubing (9) feeds into an upper part (16) of the looped portion (15) so that water syphoning off through the pipe (5) from reservoir (1) entrains or sucks in concentrate from the reservoir (11) whilst the respective taps (8,10) are open. The mixture will continue to vent from the outlet (7) as long as the water level remains above the inlet (6) of the syphon pipe (5). When the water level drops lower than the inlet (6) the apparatus automatically shuts down.
[0020] The position of the reservoir (11) in this embodiment is within the reservoir (1) at a level adjacent the upper part (16) of the looped portion (15) of the syphon pipe (5). This reduces the effect of syphoning or gravity effects on the liquid concentrate in the reservoir (11). However, the positioning is not critical if a metering device were to be incorporated in the tubing (9). Such a metering device would avoid the need to replace the tubing (9) with tubing of a different bore in order to vary the concentration of the mixture produced within the syphon pipe (5).
[0021] It is preferred to locate the tubing (9) in a particular manner to obtain the optimum result. In this embodiment the concentrate tubing (9) firstly curves upwards from the reservoir (11) and then downwards to enter the syphon loop (15) at the upper part (16). In the tested prototype movement of the connection thereof away from a position slightly forward (downstream) of the uppermost part (16) by say 1/8" either upstream or downstream results in reduced concentrate entrainment effect.
Example 2
[0023] This second embodiment of the invention is also intended to supply concentrated sheep dip from at least one relatively shallow reservoir which is diluted during delivery with water held in a larger bulk reservoir. This embodiment is capable of delivering a controlled concentration of sheep dip continuously at higher delivery rates than that of Example 1.
[0024] The apparatus comprises a suitably supported water reservoir (21) having an inlet (22) in an upper region of the water reservoir through which a water supply is controlled by means of a float operated valve (23, 24) such as a ball cock. In the base of the reservoir there is located a sheep dip delivery duct which has an inlet end (26) opening into the reservoir (21), a central mixing and dosing portion (25) and an outlet end (27) provided with a valve (28) for controlled discharge of mixed sheep dip. The central portion (25) houses a venturi tube to which there is connected a branch duct (29) which includes a valve (30) and an exchangeable dilution control orifice (39) for feeding concentrated liquid sheep dip from a smaller reservoir (31). The branch duct (29) connects at one end with the venturi tube within the central portion (25) at a suitable point adjacent to, and downstream of the vena contracta to ensure that concentrate is entrained and mixed with water discharging through the delivery tube by the effect created by the flow of water through the venturi tube. The other end passes through the wall of the reservoir (21) and continues with a with a flexible portion (29ʹ) which is connected beneath the flotation chamber (32) to a conduit (35) communicating with the reservoir (31).
[0025] In this embodiment the diluent is water and in order to ensure that the correct amount of concentrate is entrained whenever the apparatus is to be operated at relatively low flow rates when the venturi effect will be negligible, a buoyancy or flotation chamber (32) is provided beneath the reservoir (31) to support same above the water level in the bulk diluent reservoir (21). The concentrate reservoir (31) is provided with appropriate stabilising members (33,33ʹ) and guide lugs (34,34ʹ) allowing the concentrate reservoir (31) to rise and fall with the water level in the bulk diluent reservoir (21) so as to provide a pre-determined constant head of concentrate thereby ensuring a positive feed of concentrate into the delivery duct for mixing with diluent.
[0026] The flotation chamber (32) is of course simply an optional feature which is unnecessary at the higher flow rates which this embodiment is intended operate at. Less favourable but acceptable operation of the invention can be obtained without the flotation chamber (32) at low flow rates if the concentrate reservoir(s) (31) are located outside the bulk diluent reservoir (21) and so mounted as to provide a head of concentrate as required in consideration of the relative specific gravities of concentrate and diluent.
[0027] A further optional feature which is not shown in the drawings is that of providing linkages for ganged operation of the valves (28, 30) which enables the automatic turning on of concentrate feed whenever the delivery valve (28) is turned on. Similarly the dilution control orifice (39) may be replaced by multiple orifices in a manifold arrangement and multiple venturi assemblies may be incorporated in the delivery duct to provide increased delivery rates and/or control over the delivery and mixing of concentrate/diluent.
[0028] The embodiment illustrated also includes a baffle (36) which surrounds the inlet (26) to the delivery duct and reduces the possibility of any foreign matter being drawn into the delivery duct.
[0029] The following test data relate to the performance of this embodiment.
The apparatus was run at various flow rates, increasing the flow rate every 30 minutes and simultaneously drawing off a sample of delivered mixture for analysis. Two trial runs were carried out and the average of the two runs was represented graphically against a plot of the theoretically predicted performance of the apparatus. The outcome of the trials was considered to be very favourable.
Further trials at various flow rates up to 20 litres per minute were carried out and are reported in the table below and represented in a further graph (See Fig. 5).
Thereafter trials were also carried out at constant flow rates for periods of 30 minutes using the same dip (Cora) as before and sampling at 10 minute intervals. The following table shows the results obtained which were considered to be quite satisfactory.
Comparative tests were then carried out by using a conventional method to provide a dip for 400 sheep and the continuous method of this invention using an apparatus similar to that described in Example 2 to deliver Cora (Trade Mark) sheep dip for dipping a further 400 sheep. The following table shows the results of the dip bath wash analysis. Both sets of washes were taken from the same dip bath.
As can be seen from the data presented in the table above, the continuous method provides less violent swings of concentration in the bath.
[0030] The following advantages are found with use of the apparatus of this invention:
1) Only one moving part is required in operation of the apparatus: a simple ball cock can be used.
2) It is a failsafe device, in that if water supply fails the apparatus continues to supply wash at the correct concentration until the working water-head runs out to below the syphon intake, or in the absence of flow the venturi effect stops, when the apparatus shuts down and does not permit flow of dip concentrate.
3) It has a self-priming capability.
4) Consistency in dip concentrate is obtained by use of a reservoir designed to be long, wide and shallow, thus negating gravity/syphon effects since bottom of reservoir is at same height as syphon inlet. Use of a venturi also contributes to consistency in concentration.
5) The apparatus may be used with more than one dip concentrate (ie, does not depend on the percentage of insecticide in the dip concentrate) simply by increasing or decreasing the diameter of the concentrate inlet pipe.
6) It is independent of mains water pressure.
7) It is able to introduce an air-lock into the syphon when concentrate reservoir is depleted, thus shutting down the apparatus.
8) It is reliable and consistent being operated by partial vacuum rather than by gravity, ie, there is no need to maintain a head of concentrate.
9) A further significant advantage of this invention is that whereas the known constant replenishment device tops-up the bath continually with aliquots of dip, this invention continuously delivers a constant flow of dip at the correct concentration.
1. Liquid mixing apparatus which comprises a first reservoir (1, 21) for a first liquid,
at least one further reservoir (11, 31) for another liquid which is to be mixed with
the first liquid and continuous dosing means (5, 6, 7, 8, 9, 10; 25, 26, 27, 28, 29,
29ʹ, 30, 35, 39) comprising a delivery duct (5, 6, 7, 8; 25, 26, 27, 28) through which
the first liquid may be discharged from the first reservoir and at least one branch
duct (9, 10; 29, 29ʹ, 30, 35, 39) leading from the or each further reservoir and joining
the delivery duct at a point intermediate its ends enabling in use the entrainment
of the other liquid(s) by the first liquid and mixing thereof within the delivery
duct whenever the first liquid is caused to flow from the first reservoir through
the dosing means.
2. Apparatus according to claim 1 wherein the first reservoir has a liquid supply
inlet (22) provided with liquid supply control means (23, 24)to provide for automatic
filling of the first reservoir with liquid to a predetermined maximum level.
3. Apparatus according to claim 1 or claim 2 wherein the delivery duct comprises a
syphon conduit (5) having an inlet (6) opening into the first reservoir at a level
intermediate the predetermined maximum and minimum levels of liquid in the first reservoir,
said syphon conduit having a looped portion (15) into which another liquid contained
in a further reservoir (11) is introduced via a branch duct (9) connected between
the further reservoir and an upper part (16) of the looped portion of the syphon conduit.
4. Apparatus according to claim 3 wherein the looped portion of the syphon conduit
is positioned in the first reservoir in a generally upstanding manner such that the
upper part of the looped portion is substantially level with the inlet of the syphon
conduit.
5. Apparatus according to claim 4 wherein the branch duct joins the syphon conduit
at the uppermost part of the looped portion at a point slightly downstream of the
highest point in the looped portion so that liquid introduced to the syphon loop through
the branch duct tends to fall into the downstream part of the syphon loop.
6. Apparatus according to any one of the preceding claims wherein the or each further
reservoir is a vessel of high liquid surface area to low liquid depth ratio to minimise
the effect of having a head of liquid in the said further reservoir(s)
7. Apparatus according to claim 6 wherein the further reservoir is located within
the first reservoir at a position substantially level with the uppermost part of the
looped portion of the syphon conduit and the branch duct has a curved portion rising
above the level of connection thereof with the further reservoir.
8. Apparatus according to claim 1 or claim 2 wherein the delivery duct comprises a
venturi tube (25) connected to the first reservoir (21) at a suitable location (26)
to provide for delivery of liquid from the first reservoir and at least one branch
duct (29, 29ʹ) connected to the further reservoir(s) (31) and communicating with the
venturi tube via at least one orifice (39) adjacent to, and downstream of the vena
contracta.
9. Apparatus according to claim 8 wherein a flotation chamber (32) is provided within
the first reservoir to which the further reservoir(s) (31) for the other liquid(s)
together with levelling and stabilising means (33, 33ʹ, 34, 34ʹ) are attached whereby
a head (35) of said other liquid(s) can be maintained in use.
10. Apparatus according to claim 2 wherein the liquid supply control means comprises
a float operated valve (3, 4; 23, 24).