The present invention relates to apparatus for com _b ining liquids and is particularly concerned with such apparatus for delivering a metered quantity of an additive liqui _d into a carrier liquid. Such apparatus has advantage in many fields, including especially in agriculture _f or diluting liquid chemical additives such as medications, nutrients, fertilisers, weed killers and pesticide concentrates in water or other diluent.

It is most advantageous to be able to automatically supply additives to a carrier liquid such as water proportionally to the flow of the carrier liquid and it has been known to introduce an additive to water by means of a venturi suction device. A venturi nozzle is located in a pipe containing a flow of water to create a pressure difference which draws a flow of the additive into the venturi. However, accurate metering of the additive is not possible in such a device and the additive must be supplied in a relatively diluted form in order to minimise variations in the rate of dilution by this apparatus.

AU 18435/76 proposes improving the venturi control by using the pressure difference created by a venturi or other restrictor in a water supply pipe to drive a positive displacement reciprocating fluid motor which directly mechanically operates a positive displacement reciprocating fluid pump for the additive. Because this arrangement relies on the pressure difference to drive a diaphragm piston in the fluid motor and relies on only part of the flow in the water supply pipe accurate metering of the additive is again not possible. In addition, contamination by the additive of the motor an _d

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pump makes repair and cleaning hazardous.

AU 49789/90 proposes a device for applying plant- protecting compositions in which a high pressure water feed pump and an additive metering pump are connected in series in a water supply pipe so that the whole of the water flow is used to drive the metering pump. The flow of water through the metering pump displaces a control piston to adjust a series of valves, and a hollow metering piston connected to the control piston draws the additive through the metering piston into the stroke chamber of the metering pump where the additive is mixed with the water. A setting device associated with the hollow metering piston facilitates the ready adjustment of water/additive ratio but contamination of the hollow metering piston and the stroke chamber by the additive makes repair and cleaning of the device hazardous.

AU 19115/88 proposes a positive displacement pump having a plurality of inlets for mixing two or more liquids, but the pump is driven by a separate power source which is not always convenient. Similarly, EP 201981 proposes an electric control means for controlling the mixing amounts of additive and carrier liquid. This is for use with apparatus which is carried by a tractor. Such electric control means is not appropriate for use where there is no convenient power supply, such as in many agricultural . situations.

GB 2185539 proposes a peristaltic pump which delivers water from a reservoir to an irrigation channel. The pump is driven by a rotor which comprises a water wheel partly located in a river or other flow of water. The water wheel delivers the water to the reservoir.

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US 2703256 and 3807605 both disclose portable sprayers in which the liquid is sprayed by a peristaltic pump driven by displacement of a wheel of the sprayer. None of the proposals in these US specifications or in GB 2185539 provides for mixing of liquids.

It is an object of the present invention to alleviate some of the disadvantages of the prior proposals.

According to the present invention there is provided apparatus for delivering a metered quantity of additive liquid to a carrier liquid, the apparatus comprising means to supply a flow of carrier liquid, a fluid motor driven by the flow of the carrier liquid, a pump driven by the fluid motor and having inlet means for the additive liquid whereby the additive liquid is supplied by the pump proportionally to the flow of the carrier liquid, and outlet means from the pump for delivering the supplied additive liquid to the flow of carrier liquid, wherein the pump is a peristaltic pump whose outlet means to the flow of carrier liquid is downstream of the fluid motor.

Peristaltic pumps are well known and comprise a length of tubing having a resilient wall which is repeatedly gradually compressed along part of its length by displacement of a head of the pump. The recovering compressed wall part acts to draw additive liquid through the tubing and a further gradual compression of the tubing carries the additive liquid along the tubing.

By the present invention, the additive liquid does not pass through the fluid motor and contamination of the apparatus by the concentrated additive liquid is restricted to the length of resilient-walled tubing and

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the inlet and outlet means of the peristaltic pump, allowing for simple cleaning of the apparatus and ready replacement of the tubing for use of the apparatus with a different additive liquid, as well as non-hazardous repair of the apparatus. For any one head of the peristaltic pump, the metering of the additive liquid is controlled by the diameter of the peristaltic pump tubing and the rate of displacement of the peristaltic pump head relative to the fluid motor drive, both of which may be advantageously preset for any one additive.

If a mixture of additive liquids is required, the peristaltic pump may have respective inlet means for each additive liquid or respective peristaltic pumps may be driven by the fluid motor, for example on a common drive shaft, each peristaltic pump having outlet means for delivering the respective additive liquids to the flow of the carrier liquid downstream of the fluid motor.

The fluid motor must provide drive to the or each peristaltic pump proportionally to the flow of the carrier liquid and may take any of a variety of forms in which positive displacement is provided, for example a mutating disk drive, an oscillating piston drive or a rotary drive unit such as a lobed impeller or a sliding or retracting vane rotary fluid motor. In a preferred embodiment, the flow of carrier liquid through a fluid motor housing oscillates a piston in an eccentric path around a working chamber with each stroke of the piston representing the passage of a predetermined volume of the carrier liquid. The displacement of the piston is translated into rotation of an output drive which may be transmitted to the peristaltic pump head by any of a variety of means such as a reduction gear assembly.

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The apparatus may comprise a feed pump between a source of the carrier liquid and the fluid motor to pressurise the carrier liquid. However, the apparatus advantageously operates at low pressure, for example a 5 maximum pressure of 30psi where the additive liquid is delivered to a continuous flow of carrier liquid, for example in a mixing chamber, or 45psi for intermittent flow. Thus, a feed pump is not necessary and the means to supply the flow of the carrier liquid may be, for

10 example, a mains water supply pipe or other pressurized remote source or a reservoir for the carrier liquid arranged such that there can be a head of the carrier liquid in the reservoir. Means may be provided to positively pressurise the head in the reservoir.

•15

Any limitation on the maximum pressure in the apparatus is likely to be due to the pressure limits of the flexible-walled tubing in the peristaltic pump. If the carrier liquid is at a substantially greater pressure

20 than the limit of the tubing this can be transmitted back to the tubing through the delivery point of the additive liquid to the carrier liquid, with possible resultant distending or bursting of the tubing. However, this possibility can be alleviated by providing an appropriate

25 pressure drop at the delivery point, for example by providing a large hose outlet from the delivery point. Alternatively pressure control means may be provided upstream of the delivery point and/or to apply a counter- pressure to the exterior of the flexible-walled tubing of

30 the peristaltic pump.

In one embodiment, the counter-pressure may be achieved by locating the flexible-walled tubing, or at least the relevant part of it, within means which may be 35 pressurized according to the pressure of the carrier

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liquid. Such means may comprise a pressurized reservoir of the carrier liquid whereby the exterior of the flexible tubing is pressurized directly. Alternatively, such means may comprise a housing filled with oil or other pressurizable fluid (liquid or gas) with a diaphragm or other pressure transmitting means communicating on opposite sides with the carrier liquid (or a head of the liquid) and the pressurizable fluid. An increase in pressure in the carrier liquid will deform the diaphragm which pressurizes the pressurizable fluid to apply the counter-pressure to the tubing.

Upstream of the fluid motor there may be provided any of a filter to remove particulate matter from the carrier liquid, a restrictor or other device to reduce or control the carrier liquid pressure, an on/off valve to control the carrier liquid flow and a flow control valve to alleviate seepage of carrier liquid which may not be sufficient to drive the fluid motor and which would otherwise affect the concentration of previously combined additive and carrier liquids. The combined carrier and additive liquids may be dispersed directly on combination, for example by spraying or pouring at the carrier liquid pressure, or may be collected in a tank or otherwise stored. Where the combined liquids are collected in a tank, a control device, such as a float, for the aforementioned on/off valve may be associated with the tank to allow for automatic replenishment of the combined liquids in the tank.

One embodiment of 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 schematic representation of the

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embodiment of the apparatus;

Figure 2 is an elevational view of the peristaltic pump in the embodiment of Figure 1;

Figure 3 illustrates the working chamber and piston of the fluid motor in the embodiment of Figure 1; and

Figure 4 is a cross-sectional view of a preferred embodiment of the apparatus incorporating features shown in Figures 1 to 3.

The apparatus 10 in Figure 1 is adapted to provide a metered quantity of concentrated pesticide from a container 12 into a dip 14, for example for sheep or cattle.

A pressurised source of water, not shown, delivers a flow of water to supply pipe 16. The pressure water source may comprise the mains supply, a feed pump or a reservoir in which there is a head of water which may, if necessary, be positively pressurised.

The pressurised water passes through the pipe 16 to a fluid motor 18 by way of a filter 20 to remove any particulate matter from the water, an on/off valve 22 and a flow control valve 24. The on/off valve may take any suitable form, such as a spool valve, and is controlled by a float 26 in the dip 14. As the level of liquid in the dip 14 drops, the corresponding displacement of the float acts to open the valve 22 and allow automatic replenishment of the liquid. The connection 23 between the valve 22 and the float 26 may take any well known form based on any of mechanical, electrical or, for example, hydraulic control. The particular forms of control and on/off valve do not form part of the present invention.

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The flow control valve 24 is spring biased to close at a minimum water flow which is sufficient to drive the fluid motor so that there will be no seepage of water through the fluid motor at a level which is insufficient to actuate the fluid motor, thereby avoiding unwanted reduction of the concentration of the pesticide in the dip. Such minimum fluid flow will vary for different fluid motors but in the preferred embodiment is 0.35 litres per minute. The flow control valve may also act as a one-way valve preventing backflow of water which has been mixed with pesticide.

The fluid motor 18 drives a peristaltic pump 28 through reduction gears 30, 32. The peristaltic pump 28 has a length of resilient-walled tubing 34 (shown schematically in Figure 1), for example of Norprene, silicon rubber, or fluro-elastomer (Norprene is a trade mark), extending therethrough and having an inlet end portion 36 in the container 12 and an outlet end portion 38 in a mixing chamber 40 into which the output water from the fluid motor 18 is also conveyed by pipe 42. The concentrated pesticide from the container 12 and the water output from the fluid motor 18 are mixed in the mixing chamber 40, which may take any suitable form, and the output therefrom is delivered to the dip 14 by means of outlet pipe 44.

The fluid motor 18 converts the kinetic energy of the pressurised water in pipe 16 to mechanical energy by means of an oscillating hollow piston 46 which is displaceable in a chamber 48 having an inlet port 50 from the pipe 16 and an outlet port 52 to the pipe 42 in the base 54 of the chamber, as shown in Figure 3. Each oscillatory stroke of the piston 46 is a measure of the volume of water passing through the chamber 48 and water

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meters incorporating such an arrangement are well known as described in Van Norstrand\'s Scientific Encyclopedia, Fifth Edition, pp 1070-1.

Referring to Figure 3, the hollow piston 46 is mounted for reciprocating oscillating movement on a shutter 56 in the chamber 48 which prevents direct communication between the inlet and outlet ports 50 and 52. The hollow piston 46 is permitted some swinging movement about the shutter 56 as it moves from a top dead centre position in which it overlaps both the inlet port 50 and the outlet port 52, through a bottom dead centre position in which it overlaps neither of the ports 50 and 52, back to the top _d ead centre position. The swinging movement of the piston is caused by the guidance of an axial shaft 58, in a circular path between a guide post 59 and an annular wall 60. The shaft 58 is relatively rotatably engaged with a paddle rotor 61 (not visible in Figure 3) which is rotatable with a shaft 62. The shaft 62 drives the peristaltic pump 28 through the gears 30 and 32. Thus, the swinging oscillating movement of the piston 46 about the chamber 48 causes the rotor 61 to be rotated by virtue of its engagement with the piston, and suc ^h rotation is translated to the shaft 62.

In the top dead centre position, pressurised water from the inlet port 50 is present within the corresponding side of the piston while exhaust water in communication with the outlet port 52 is present within the other side of the piston, on respective sides of the shutter 56, and neutral water extends around the piston 46 within the chamber 48.

The increased pressure within the side of the piston 46 in communication with the inlet port 50 causes the piston

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to be displaced along the shutter 56, such displacement causing part circular displacement of the shaft 58 through the position shown in Figure 3, the corresponding swinging movement of the piston maintaining it in contact with the wall of the chamber 48. In this position, pressurised water in communication with the inlet port 50 exists within the majority of the piston and within the chamber 48 between the piston and the shutter 56. Fluid pressure from the inlet port 50 on the external wall of the piston 46 causes it to move through the bottom dead centre position, when the interior of the piston is closed to the inlet and outlet ports 50 and 52, to a position opposite that shown in Figure 3 when the interior of the piston 46 once again begins to open communication with the inlet port 50. As soon as the piston moves out of the bottom dead centre position the water within the piston 46 is open to communication with the outlet port 52 so that a specified volume of water passes through the piston 46 and chamber 48 during each oscillatory stroke of the piston.

The rotation of the shaft 62 rotates a shaft 64 engaged with a head 66 of the peristaltic pump through the reduction gears 30 and 32. The head 66 comprises a plate 68 on which are mounted for independent rotation three rollers 70, 72 and 74. More rollers may be used, and six are preferred. The rollers are equally spaced from each other and from the axis of the shaft 64 and the length of tubing 34 extends through the pump housing 76 between the rollers 70, 72 and 74 and a part circular housing wall

78. The spacing between the rollers and the housing wall 78 is substantially less than the external diameter of the tubing 34 and sufficiently small that each portion of the tubing compressed between the respective roller and the wall 78 is closed off. The housing 76 has a neck 80

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from which the tubing 34 projects and, between the rollers, the length of tubing within the housing 76 expands to at least substantially its full diameter due to the resilience of the tubing wall.

As the head 66 of the peristaltic pump is rotated in a clockwise direction by the shaft 62, the roller 74 gradually compresses successive portions of the fixed tubing in the housing 76 and as the tubing is released following passage of the roller it sucks the pesticide additive in through the inlet end portion 36. With continued rotation of the head 66 the roller 70 engages the tubing to positively displace therealong a predetermined volume of the pesticide which has been previously drawn up from the reservoir. Thus, an accurate volume of pesticide is drawn up by the peristaltic pump for each revolution of the head 66 and, for a fixed diameter of tubing 34, size of head 66 and gearing between the fluid motor 18 and the peristaltic pump 28, a predetermined volume of pesticide is drawn through the pump for each stroke of the piston 46 in the fluid motor 18.

Peristaltic pumps have the advantage over all other pump types of being able to pump small volumes per unit time, for example as low as 0.001 ml/min and have the best self priming capacity of all pumps. Peristaltic pumps have good viscous fluid pumping characteristics as well as the ability to pump particulate matter in fluids, whether colloidal or otherwise, unlike piston, centrifugal, gear, vane and flexible impeller pumps. This is because the only portion of the pump with which the additive liquid comes into contact is the tubing which apart from being radially compressed and relaxed is fixed in place. Furthermore, because of this feature the tubing can run

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dry without damaging the pump. In place of the described peristaltic head, a peristaltic head of the over-centre cam type or of an interchangeable occlusion cartridge pump type, for example moulded in chemically resistant polycarbonate and glass filled nylon, may be appropriate.

It has been found that the described apparatus is reliable and accurate to within 5% of the desired concentration. This accuracy has the potential to allow the use of an increased concentration of additive liquid with consequent reduction in packaging volume, storage space and transport costs. Furthermore, the apparatus can eliminate the need for specialised holding tanks for individual diluted concentrates prior to use and subsequent environmental contamination when these tanks are cleaned after use. The mixing of several concentrates or additive liquids that are incompatible in a single formulation can be readily achieved by providing a plurality of peristaltic pumps, and in the described apparatus it has been found that up to four peristaltic pump heads may be driven by the fluid motor 18.

In the described apparatus, the fluid motor, filter, on/off valve, flow control valve and peristaltic pump may be provided in a single module sealed against dust and dirt but with ready access to the peristaltic tubing in case of mechanical failure. The mixing chamber may form part of the module but any downstream pipes may be detachable from such a module to allow easy decontamination. The module, with or without the mixing chamber, may be attached into an existing diluent line by means of, for example, pressure snaplock fittings.

Figure 4 illustrates a practical embodiment of the apparatus described with reference to Figures 1 to 3

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which, accordingly, will not be described in detail. In the following description the same or similar parts to those in Figures 1 to 3 will be given the same reference numeral followed by a "\'".

Referring to Figure 4, the metering and mixing apparatus 100 comprises a water inlet pipe 16\', a fluid motor 18\' and an outlet pipe 42\' incorporating a mixing chamber 40\'.

The inlet pipe 16\' receives relatively low pressurized water, for example at less than 24psi and from a mains supply or a header tank. A spool valve 22\' provides the primary control on the water flow through the fluid motor 18\' , the spool valve being controlled by the float 26 in dip 14 as described with reference to Figure 1. Thus, when the dip is below a predetermined level the spool valve 22\' is opened to replenish it.

A pressure valve 24* is opened by the flow of water provided the pressure of the water is above a predetermined level sufficient to drive the fluid motor 18\'. The pressure valve 24\' comprises a pressure plate 102 which is biased by a spring 104 against a mounting plate 106 located in the pipe 16\'. The mounting plate

106 has openings therethrough for the flow of water which are closed by the pressure plate when the water pressure is insufficient to overcome the spring bias. The spring 104 is in the form of a compression spring disposed about a rod 108 extending from the pressure plate 102 through the mounting plate 106. The rod 108 has a screw-threaded remote end with which an adjusting nut 110 in abutment with the compression spring is engaged, to vary the biasing pressure. By this arrangement, the valve 24\' also acts as a one-way valve.

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The water passing through the pressure valve 24\' then encounters a filter 20\' in the form of stainless steel mesh. The mesh is introduced to the pipe 16\' through an access branch 112 which is closed by a cap 114, and can be withdrawn from the branch 112 for cleaning.

The filtered water then enters the fluid motor 18\' through inlet port 50\' . The fluid motor has been described in detail with reference to Figure 3 and will not be described further. However, for convenience corresponding reference numerals have been included in Figure 4. Water from the fluid motor passes through the outlet port 52\' into the outlet pipe 42\' .

Rotary displacement of the paddle rotor 61\' by the flow of water through the fluid motor 18\' rotates the shaft 62\' which drives the reducing gear train conveniently referenced 30\', 32\' although four gears are shown in the train. The intermediate gears 116 and 118 are mounted on a shaft 120, all of the gears being rotatably supported in a cage 122. Shaft 64\' of gear 32\' is in driving engagement with the peristaltic pump head 66\' .

The peristaltic pump 28\' has been described in detail with reference to Figures 1 to 3 and will not be described again. It will be noted that only two of the head rollers, 70\' and 74\' are visible in the section of Figure 4 and that the rollers are supported for rotation between spaced plates 68\' and 124 which are rotatable with a head axle 126 which is effectively an extension of the shaft 64\' .

The outlet end portion 38\' of the flexible tubing 34\' which passes through the peristaltic pump head 66\' engages a nipple 128 on the wall of the outlet pipe 42\'

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_f rom t _h e fluid motor 18\', adjacent the entry to the mixing chamber portion 40\' of the outlet pipe. The mixing c _h am _b er 40\' is defined by a turbulence-inducing formation in the outlet pipe which as shown is in the form of a ribbon of material 130 having a corkscrew configuration. The material must be inert to the liquids in the outlet pipe, for example polypropylene or stainless steel.

_A one way valve 132 is provided in the tubing 34\' between the peristaltic pump 28\' and the inlet end 36\' to ensure there can be no back flow of water through the tubing 34\' into the container 12 of additive, for example due to increased water pressure in the outlet pipe 42\' . The peristaltic pump 28\' operates at a maximum pressure of about 24psi, above which the flexible tubing 34\' is liable to distend or burst. In order to minimise the risk of this should there be an unexpected pressure increase in the outlet pipe 42\', means is provided in the embodiment shown in Figure 4 to provide a counter- pressure to the exterior of the tubing 34\' downstream of the one-way valve 132.

The counter-pressure means comprises a housing 134 ⁽ shown schematically in dashed lines) within which the pump 28\', the gear cage 122 and the flexible tubing 34\' downstream of the one way valve 132 are enclosed. The housing is filled with a hydraulic fluid, conveniently an oil or, for example, a viscous liquid such as glycol. The outlet pipe 42\' from the fluid motor 18\' forms part of one wall of the housing 134 and a resilient diaphragm 136 in the wall of the outlet pipe 42\' upstream of the mixing chamber 40\' communicates on opposite sides with the water in the outlet pipe and the hydraulic fluid in the housing 134. The diaphragm and hydraulic fluid are provided in

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such a way that with an increase in pressure above about 24psi in the outlet pipe 42\' the diaphragm deforms into the housing 134 to pressurise the hydraulic flui ^d therein. The increased pressure of the hydraulic flui ^d around the flexible tubing 34\' counters the increase in pressure internally of the tubing which is transmitted from the outlet pipe 42\'. By this means, the apparatus 100 may be readily operated at pressures greater than the normal maximum operating pressure of the peristaltic pump.

_A t sea _l a _bl e opening (not shown) should be provided in t ^h e housing 134 to allow the hydraulic fluid to be dra ⁱ ned for access to the pump 28\' .

In a modification where the carrier liquid is supplied from a pressurized reservoir, the peristaltic pump, and particularly the flexible tubing therefor, may be disposed in the reservoir so that the reservoir pressure is applied automatically to the exterior of the tubing as we _l l as to the interior of the tubing through its connection with the outlet pipe from the fluid motor. This arrangement eliminates the need for the enclosed housing 134 containing hydraulic fluid and the diaphragm 136, although these may be provided if it is desired to avoid direct access for the carrier to the exterior of the tubing. The diaphragm would then be acted on by the carrier liquid in the reservoir or the head of the carrier liquid.

T _h ose s _k illed in the art will appreciate that many modifications and variations may be made to the desire ^d apparatus and all such modifications and variations should be considered as falling within the scope of the present invention. In particular, it will be appreciated

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that the described fluid motor may be replaced by one in which a hollow piston reciprocates in a chamber of known volume such as of the type commonly used in drench guns or by a bellows type metering device.

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