BACKGROUND TO THE INVENTION In many regional country town water supplies the only economical way that hazardous chemicals can be delivered to water treatment plants is by portable chemical containers (20 to 40 litre capacity). More often than not, a chemical metering pump, which accurately meters the required amount of chemical into the water, needs many times the capacity of a single container and therefore a vat is used in which the chemical is stored.

The main problems associated with manually handling the chemical from the portable containers to the vats is that it is a slow, laborious and hazardous task for treatment plant operators. Whilst a number of methods have been introduced to reduce the time and risks involved, the exercise of"double handling"of the liquid chemical still remains a significant problem.

Other users of hazardous liquid chemicals, such as farmers, who also have a need to accurately meter a wide range of chemicals into water, also have major problems with this "double handling"process. Here again, a number of initiatives have been proposed to reduce the time and risks involved in transferring hazardous chemicals from portable containers into vats and tanks. These initiatives include battery-operated transfer pumps, purpose-built stands with special chemical syphons and innovative vortex systems, all of which improve the process, but do not remove the"double handling"problem.

SUMMARY OF THE INVENTION The present invention was developed with a view to providing a chemical metering pump that can substantially eliminate the problem of"double handling"by enabling the chemical metering process to take place directly from the portable container in which the chemical is delivered, rather than from a storage vat or tank.

Throughout this specification the term"comprising"is used inclusively, in the sense that there may be other features and/or steps included in the invention not expressly defined or comprehended in the features or steps subsequently defined or described.

What such other features and/or steps may include will be apparent from the specification read as a whole.

According to one aspect of the present invention there is provided a chemical metering pump for metering a liquid chemical from a container, the pump comprising: a discharge adaptor for connecting the pump to an outlet of the container, said discharge adaptor having an intake port adapted to be in fluid communication with the liquid in the container and a discharge port adapted to be in fluid communication with a discharge tube leading to a flowstream; a diaphragm housing connected to said discharge adaptor and having a diaphragm driven by a reciprocating member therein for alternately drawing liquid by suction into said intake port and pushing the liquid by compression out through said discharge port; and an actuator provided in connection with said diaphragm housing for driving said reciprocating member in a reciprocating motion in response to a control signal received from a remote controller whereby, in use, liquid chemical in the container can be metered by the pump from the discharge port.

Preferably both said intake port and discharge port are provided with a one way valve for controlling the flow of liquid into said intake port and out through said discharge port respectively. Typically said one way valves are gravity ball valves.

In one embodiment of the invention the whole pump is designed to be fully submersible in the liquid chemical within the container. Preferably said discharge adaptor, diaphragm housing and actuator are arranged end to end in an elongate, cylindrical configuration having an outer diameter sufficiently small to allow the whole pump to be inserted through

an outlet aperture of the container.

Preferably said discharge adaptor also includes a vent port extending into said diaphragm housing for venting a space behind said diaphragm to atmosphere. Advantageously said vent port also extends through said diaphragm housing to the actuator and provides a path through which a connector for connecting the actuator to said remote controller can pass.

Preferably said actuator is an electrical solenoid actuator.

Preferably the chemical metering pump further comprises a remote electronic controller for generating and transmitting said control signal to the actuator in the pump.

Preferably the chemical metering pump further comprises a calibration device for calibrating the rate at which liquid chemical is metered from the pump.

BRIEF DESCRIPTION OF THE DRAWINGS In order to facilitate a more comprehensive understanding of the nature of the invention several embodiments of the chemical metering pump in accordance with the present invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which: Figure 1 illustrates a prior art electronic chemical metering pump ; Figure 2 illustrates a first embodiment of a chemical metering pump according to the present invention in situ ; Figure 3 is an enlarged section view of the chemical metering pump of Figure 2; Figure 4 illustrates in section view a second embodiment of a chemical metering pump according to the present invention in situ, Figure 5 illustrates the chemical metering pump of Figure 4 in a typical application;

Figure 6 illustrates in section view a third embodiment of a chemical metering pump according to the present invention; Figure 7 illustrates the chemical metering pump of Figure 6 in a typical application; Figure 8 illustrates in section view a fifth embodiment of a chemical metering pump incorporating a first embodiment of a calibration system; Figure 9 illustrates in section view a fifth embodiment of a chemical metering pump according to the present invention; Figure 10 is a plan view of the chemical metering pump of Figure 9; Figure 11 is a front section view of the chemical metering pump of Figure 9 with an integrated calibration system fitted; Figure 12 is a front view of the chemical metering pump of Figure 9; Figure 13 illustrates a second embodiment of a calibration system for the chemical metering pump of Figures 6 and 7; Figure 14 illustrates the calibration system of Figure 13 in situ ; Figure 15 illustrates another embodiment of a cradle for holding a container containing chemicals for metering; Figure 16 illustrates a multi-head chemical metering pumping system in accordance with the present invention; Figure 17 illustrates a preferred embodiment of an auto-refill system for use in conjunction with the chemical metering pump of the present invention;

Figure 18 illustrates banked and tiered chemical containers incorporating the auto-refill system of Figure 17, mounted in a cradle system; and, Figures 19 (a), (b) and (c) illustrate a third embodiment of a calibration system for the chemical metering pump according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS A prior art electronic chemical metering pump 10 illustrated in Figure 1 has an inlet 12 which draws liquid chemical from a vat 14 and a discharge valve 16 through which liquid chemical is metered to a flowstream 18. The pump 10 includes a built-in electronic controller 20 for controlling the operation of the pump 10 so that it accurately meters the required volume of liquid chemical into the flowstream 18. The liquid chemical held in the vat 14 may be, for example, liquid chlorine which is metered into the water supply flowstream 18 at the rate of between 0.05 to 10 litres/hour.

As noted above, one of the problems with this type of prior art metering system, is that the vat 14 must be periodically refilled with liquid chemical. This task is done manually, and in addition to being laborious and time consuming, may also be dangerous, particularly when handling hazardous chemicals.

Figure 2 illustrates a first embodiment of a chemical metering pump 24 in accordance with the present invention. Instead of having an electronic controller built-in to the pump, a remote electronic controller 26 is provided (in this case shown as a wall-mounted unit), which is connected by cable to the chemical metering pump 24. The electronic controller 26 performs essentially the same function as the conventional electronic controller 20 of Figure 1, however it differs from the prior art controller in that it is capable of safely transmitting a low voltage, variable, control signal to one or more chemical metering pumps via suitably screened cable (s). Furthermore, as it is preferably mounted in a separate, wall-mounted unit, it can be positioned in a more convenient environment, such as a plant control room, where it can be viewed (at eye level) and adjusted in total safety and isolation from the pumping installation.

The chemical metering pump 24 of the present invention overcomes the problem of "double handling"by being itself adapted to be connected directly to an outlet of a chemical transport/storage container 28. For this purpose, the pump 24 comprises a discharge adaptor 30 for connecting the pump to an outlet of the container 28, the discharge adaptor 30 having an intake port 32 (see Figure 3) adapted to be in fluid communication with the liquid chemical in the container 28, and a discharge port 34 adapted to be in fluid communication with a discharge tube 36 leading to a flowstream 38.

As can be seen more clearly in Figure 3, the chemical metering pump 24 of this embodiment is in the form of a"micro submersible"pump capable of being submerged in the liquid chemical within the container 28. As shown in Figure 3, the discharge adaptor 3G has a substantially cylindrical body adapted to be received in the outlet aperture 40 of the container 20, in which it is held in sealing relationship by a suitable screw-threaded connector 42. Once the cable 25 from controller 26 and the discharge tube 36 are connected, the container 28 is laid on its side as shown in Figure 3. The pump 24 further comprises a diaphragm housing 44 connected to the discharge adaptor 30 and having a diaphragm 46 provided therein for alternately drawing liquid by suction into the intake port 32 and pushing the liquid by compression out through the discharge port 34. The diaphragm 46 is driven by a reciprocating member 48 which is coupled to an actuator 50.

In this embodiment, the actuator 50 is an electrical solenoid actuator, in which a solenoid 52 causes the reciprocating member 48 to move in a reciprocating motion in response to a control signal from the controller 26. A coil spring 54 provided within the housing of the electrical actuator 50 pushes the diaphragm 46 via member 48 to a normally closed position in which it compresses liquid within the discharge port 34 through a discharge valve 56. However, when an electrical pulse activates the solenoid 52, the reciprocating member 48 is drawn backwards against the force of the spring 54 to move the diaphragm 46 to the open position in which it simultaneously draws fresh liquid chemical through an intake valve 58, which is in fluid communication with the liquid chemical in the container 28, and into the intake port 32. With each reciprocating movement of the diaphragm 46, a precise volume of liquid chemical is metered from the container 28. The flow rate can be controlled by adjusting the rate at which electrical pulses are transmitted to the solenoid

actuator 50 from the controller 26.

The discharge valve 56 and intake valve 58 are one way valves for controlling the flow of liquid out through the discharge port 34 and into the intake port 32 respectively. In this embodiment both the intake valve 58 and discharge valve 56 are ball valves, in which a small ball bearing is normally held in the closed position by gravity or by a small spring.

Discharge valve 56 prevents the liquid chemical from being drawn back into the discharge port 34 when the diaphragm 46 moves backwards to its open position, and intake valve 58 prevents the liquid chemical from flowing back out through the intake port 32 when the diaphragm 46 moves forward to its closed position. Clearly, other suitable one way valves may be used to control the flow of liquid chemical through the intake and discharge ports.

Advantageously the discharge adaptor 30 also includes a vent port 60 which extends into the diaphragm housing 44 for venting a space behind the diaphragm 46 to atmosphere.

This allows the free movement of the diaphragm 46 between its open and closed positions.

Preferably the vent port 60 also extends through the diaphragm housing 44 to the electrical actuator 50 and provides a path through which an electrical connector for connecting the actuator 50 to the remote controller 26 can pass. A wire 62 which passes through the vent port 60 connects the solenoid 52 to the cable 25. If the diaphragm 46 ruptures the vent port 60 allows the fluid to be vented to atmosphere, so that fluid does not flow into the actuator 50 and provides an indication that the diaphragm 46 has failed.

As can be seen in Figure 3, the discharge adaptor 30, diaphragm housing 44 and electrical actuator 50 are all arranged end to end in an elongate, cylindrical configuration having an outer diameter sufficiently small to allow the whole pump 24 to be inserted through the outlet aperture 40 of the container 28. Advantageously the whole of the submersible pump assembly is encased in a chemically resistant shroud so as to be protected from the corrosive properties of the liquid chemical. In this manner, liquid chemical solution can be pumped directly from within the container 28 and metered through the discharge tube 36 to a flowstream in a most efficient manner.

Figure 4 illustrates in section view a second embodiment of the chemical metering pump

which is similar to the first embodiment illustrated in Figure 3 except in this case the pump is not submerged in the chemical solution within the container 28. The like parts in the pump 64 of this embodiment have been identified with the same reference numerals as in the pump 24 of Figure 3 and will not be described in detail again. The principal difference in this embodiment is that the discharge adaptor 30 is provided with a secondary location adaptor 66 for connecting the pump to the outlet aperture 40 of the container 28. Secondary location adaptor 66 is formed with an inlet port 68 for connecting the intake port 32 in the discharge adaptor 30 in fluid communication with the liquid chemical in the container 28.

The secondary location adaptor 66 is also provided with a vent tube 70 adapted to extend upwards into the container 28 to a point above the level of liquid chemical within the container 28 (when inverted). Vent tube 70 allows air from the atmosphere to enter the container 28 so as to avoid the formation of a vacuum within the container during metering of chemical solution via pump 64. Optionally, a filter member 72 may be provided in the inlet port 68 so as to prevent any sediment which may settle to the bottom of the container 28 from entering the flowstream via the chemical metering pump 64. A handle bracket 74 is provided for supporting the pump 64 from the handle of the container 28 in its inverted position.

Figure 5 illustrates the chemical metering pump 64 of Figure 4 in a typical application in which liquid chemical is metered from the container 28 to a flowstream 38 under the control of a remote electronic controller 26. In this case, the container 28 is held in a specially designed cradle 76 with built-in bunding tray. Cradle 76 enables the container 28 to be rotated from an upright position, in which the pump 64 can be fitted to the outlet aperture of the container in the manner illustrated in Figure 4, to an inverted position as shown in Figures 4 and 5 ready for metering. Cradle 76 reduces the time and labour involved in replacing an empty container with a full container of liquid chemical, since the full weight of the container 28 is at all times supported in the cradle 76 while the pump 64 is being fitted to the outlet aperture.

Figure 6 illustrates in section view a third embodiment of the chemical metering pump 80

in accordance with the present invention. This embodiment is substantially identical in construction to the first embodiment illustrated in Figure 3, and therefore the like parts have been identified with identical reference numerals as in Figure 3, and will not be described again in detail. This embodiment of the pump 80 is also designed to be fully submersible but in this case is suspended by means of a support member 82 within a large chemical storage container, for example, a 200 litre drum as illustrated in Figure 7. A support member 82 is adapted to hold the pump assembly 80 within close proximity to a floor of the drum 84 and is fixed at its top end to the outlet aperture of the drum 84.

Support member 82 may be, for example, a hollow PVC conduit, and the discharge tube 36 from the discharge port 34 is carried upwards within the hollow confines of the conduit 82. Cable 25 is also supported by the support member 82 and is lead out through the drum outlet aperture to controller 26. In other respects, the operation of the submersible chemical metering pump 80 of this embodiment is substantially identical to that of Figure 3.

Figure 8 illustrates in section view a fourth embodiment of a chemical metering pump 150 in accordance with the present invention. This embodiment of the chemical metering pump 150 is of more compact construction and incorporates several additional innovative features compared to the previous embodiment. As in the previous embodiment, a reciprocating member 152 is adapted to be driven by a solenoid 154 which causes the reciprocating member 152 to move in a reciprocating motion in response to a control signal from the controller (not illustrated). A diaphragm 156, driven by the reciprocating member 152, is provided within a diaphragm housing 158.

In this embodiment, the diaphragm housing is formed by a pair of removable diaphragm housing inserts 160A and 160B that are held in sealing relationship in a chamber formed partly within the discharge adaptor 162 and partly within the solenoid housing 164. The removable inserts 160A and 160B together define the internal volume of the diaphragm housing 158, and thereby the capacity of the pump. Furthermore, inserts 160A and 160B can also be formed with a variety of configurations of inlet and outlet ports depending on the particular application of the pump. Thus, for example, in the embodiment of Figure 8, insert 160B is formed with a discharge port 166 that aligns with a discharge port 168

provided in the discharge adaptor 162. Insert 160B is also formed with an intake port that is in fluid communication with a pump reservoir 172 via one-way ball valve 174. The pump reservoir 172 is in fluid communication with liquid chemical in the container via transfer port 176 (suction). The transfer port 176 can be closed off by means of a transfer valve 178, which is slidably moveable between an open position (as shown in Figure 8) and a closed position. The pump reservoir 172 is also in fluid communication with a sight tube 180 (see Figure 11) of the calibration system via sight tube connecting port 182. A by-pass port 184 is provided within the body of the discharge adaptor 162 and is provided with a by-pass control valve 186. By-pass port 184 provides fluid communication between the discharge port 168 and the bottom of the sight tube by-pass tube 188 (see Figure 11).

The sight tube by-pass tube 188 is open to atmosphere at its upper end and overflows into the sight tube 180.

As can be seen most clearly in Figure 10, the discharge adaptor is provided with a screw- threaded connector 190 adapted to screw onto the threaded outlet aperture in the wall of liquid container 192. The operation of this embodiment of the pump 150 is similar to that of the previous embodiments, and will not be described again.

Figure 9 illustrates a fifth embodiment of the chemical metering pump 200 which in many respects is similar to the pump 150 of the previous embodiment. However, pump 200 is also provided with a stroke adjuster 202 for adjusting the stroke of the reciprocating member 152, and thereby providing another means for adjusting the volume of liquid metered by the pump 200. Stroke adjuster 202 comprises a solenoid stroke limiter 204 which is pivotally mounted at the rear of the solenoid 154. The position of the solenoid stroke limiter can be varied by turning a stroke adjuster knob 206 provided on the front face of the pump 200. In other respects, the pump 200 is substantially identical to the pump 150 of the previous embodiment, and the similar parts have been identified with the same reference numerals.

In order to determine the rate at which chemical solution is metered from the container 28 to a flowstream 38, an integrated calibration system 90 has been developed for use in connection with the chemical metering pumps 150 and 200 illustrated in Figures 8 and 9.

As can be seen most clearly in Figures 11 and 12, the calibration system 90 includes the transfer valve 178, (shown in Figure 8 in the open position). When the transfer valve 178 is in the open position, the pump reservoir 172 is flooded with liquid chemical from the container 28. The calibration system 90 operates in the following manner. With both transfer valve 178 and bypass control valve 186 fully open (maximum), chemical solution transfers from the container into the calibration system via transfer port 176 and into the reservoir 172, filling the calibrated sight tube 180 via the sight tube connecting port 182 (see Figure 11). The level of the chemical solution in the sight tube 180 will be the same as the level of chemical solution within the container 28 (sight tube 180 extends the full height of the container 28). The electronic controller 26 is then switched on and the pulse rate set to maximum so that the pump 150 or 200 will commence circulating liquid chemical into the sight tube 180 via by-pass tube 188.

The transfer valve 178 is then moved to the fully closed position, (and where additional containers are connected, an auxiliary valve is also closed), and by-pass control valve 186 is partially closed until the product level in sight tube begins to fall. This indicates that liquid chemical is now being discharged into the flowstream 38 via discharge tube 36. To determine the rate at which product is being discharged into the flowstream, the rate at which the level of product in the sight tube 180 descends is timed against the calibration scale (millilitres per minute). If the discharge rate is lower than the rate required, the by- pass control valve 186 can be adjusted and calibration repeated until the desired rate is achieved. Once the desired rate is achieved, the transfer valve 178 is opened and the pump is ready for operation.

The above described calibration system 90 can be readily adapted to a standard S/C and MIS pump. It is ideal for either multiple chemical or single control use and also has the facility to eliminate vapour lock (where gaseous chemicals are used).

Figures 13 and 14 illustrate a second embodiment of the container calibration system 110, which can be used in connection with the submersible pump 80 illustrated in Figure 6.

The calibration system 110 replaces the support member 82 of Figures 6 and 7 and

includes a threaded bracket 112 which is linked to the intake port 32 of the pump 80 by means of a flexible tube 114. The calibration system I10 comprises three concentric members, a hollow outer casing 116, a hollow inner valve stem 118 and a calibration indicator rod 120.

A float 122 is provided at the lower end of the calibration indicator rod 120 which is free to slide up and down within the inner valve stem 118. A series of connecting ports 124 are provided adjacent to the lower end of the inner valve stem 118 to allow the transfer of liquid chemical from within the outer casing 116 to within the inner valve stem 118. A calibration valve 126 is provided at the upper end of the inner valve stem 118. Attached to and supported by the outer casing 116 is the pump discharge tube 36, a pump vent tube 128 and the pump power supply/control signal cable 25. The pump discharge tube 36 is in fluid communication with the chamber formed within the outer casing 116 by means of a by-pass control valve 130. The pump discharge tube 36 is connected to the by-pass control valve 130 via a T-junction which connects to a controlled discharge line 132 that connects to the flowstream 38.

The calibration system 110 operates as follows. With the calibration valve 126 open, liquid chemical product flows through the valve seat orifice 127 and reservoir ports 119 flooding the pump reservoir via flexible tube 114. Both the outer casing 116 and the chamber within the inner valve stem 118 are flooded with liquid chemical product. This causes the calibration indicator rod 120 to rise upwards within the valve stem chamber 118 to the same level as the liquid content of the vat/drum. By reading the right hand calibrated scale (litres) marked on the rod 120 the volume of liquid chemical in the container can be measured. To calibrate the pump, by-pass control valve 113 is turned to the fully open position, and the electronic controller 26 is set with the pulse rate to maximum. The pump will then commence circulating liquid chemical product through the calibration system. The calibration valve 126 is then shut and the by-pass control valve 130 is partially closed until the indicator rod 120 starts to fall, The liquid chemical product is now being discharged into the flowstream. In order to determine the rate at which the product is being discharged, the rate at which the rod 120 descends is timed using the left hand scale in millilitres per minute. If the discharge rate is lower than the

rate required, the setting of the by-pass control valve 130 is adjusted and the calibration process is repeated until the precise rate required is achieved. Once the desired discharge rate is achieved, the calibration flow valve is fully opened and the system is ready for normal operation.

Figure 15 illustrates an alternative embodiment of a cradle for holding a liquid chemical container that may be used in conjunction with the chemical metering pump 24 as illustrated in Figures 2 and 3. The cradle 136 has a first pivotable support frame 138 that is pivotably connected to a base 140 by means of hinges 142. With the support frame 138 in the upright position (as shown), two containers 28 can be loaded into the support frame (only one container illustrated). The container may be held in place by a spring loaded bracket 144 or other suitable retaining means. When the pump 24 is fitted in the outlet aperture of the container 28, the whole support frame 138 is pivoted to its horizontal position on the base 140 and the product is then ready for metering from the containers 28.

Figure 16 illustrates a multi-head chemical metering pumping station which employs all three embodiments of the chemical metering pump in accordance with the invention. The two different types of cradle for supporting the liquid chemical container 28 are also illustrated. All four chemical metering pumps illustrated are controlled by a single electronic controller 26 which is remotely located as a wall-mounted unit. The cradle 136 is shown holding two containers connected to the one pump to operate in bank fashion to increase the capacity of liquid that can be pumped by the pump.

Figure 17 illustrates a preferred embodiment of an auto-refill system for use in conjunction with the chemical metering pump of the present invention. The auto-refill system comprises a container drain tap 210 adapted to be fitted to the spout of any chemical container 212, which enables the container to be safely laid on its side to facilitate the syphoning of its contents. The drain tap 210 comprises a scavenger tube 214 that extends into the container 212 with its opening close to the bottom of the volume of liquid in the container when laid on its side. Scavenger tube 214 ensures maximum fluid drainage during syphoning. A lever 215 can be manually operated to open and close the drain tap 210. An expandable spout attachment 216 is provided to connect the other end of the

scavenger tube 214, external to the container 212. Spout attachment 216 extends into the top of the sight tube 180, fitted to the pump 200 provided in connection with a liquid chemical container 218 provided below the container 212. The drain tap 210 also comprises an air-inducer outlet 220 which passes through the drain tap into the liquid chemical in container 212, and permits air to be induced into the container 212 under certain conditions (to be described below).

Container 218 is fitted with an auto-refill valve 222 adapted to be fitted into a purpose- built aperture in the side of the chemical container 218. Auto-refill valve 222 comprises a level signalling device 224 at its upper end, an upper chamber 226 and a lower chamber 228. A spindle 230 extends from the level signalling device 224 down through the upper chamber 228 into the lower chamber 228 where it connects to a float 232 provided within the lower chamber 228. A ball float 234 is provided adjacent the lower chamber 228. A plurality of fluid ports 227 are provided near the top of the upper chamber 226 where liquid enters of the auto-refill valve. The auto-fill system operates as follows.

With container 18 already laid on its side in its cradle 236, the liquid chemical in the container will be at the high mark 238. The chemical metering pump 200 is connected to a controller 240 ready to operate, and the auto-refill valve 222 is installed into the threaded aperture in the side of container 218. A 4mm connecting tube 242 is attached at one end to the level signalling device 224, and at its other end to the air inducer outlet 220 of the drain tap 210 for the back-up container 212. The drain tap 210 is fitted to the outlet of the container 212 before the container 212 is laid on its side on the upper tier of the cradle 236. Spout attachment 216 is arranged so that liquid chemical drawn from container 212 via the scavenger tube 214 drains directly into the sight tube 180 of container 218.

Because the only source of air into the interior of container 212 (via air inducer outlet 220) is closed by the level signalling device 224, no liquid chemical will drain from container 212 at this stage.

Until the liquid within container 218 reaches the low mark 244, chemical metering pump 200 draws liquid exclusively from the lower container 218. Both the upper chamber 226 and lower chamber 228 of the auto-refill valve 222 are filled with liquid at this stage.

However, when the liquid chemical reaches the low mark 244, the ball float 234 in the auto-refill valve 222 drops from its seat allowing the fluid within the upper chamber 226 and lower chamber 228 to escape from within the auto-refiil valve 222. As pump 200 continues to discharge liquid from the container 218, the level of liquid within the auto- refill valve 222 will gradually fall until it reaches the lower chamber 228. At that point, float 232 begins to fall whereupon the level signalling device 224 is caused to pivot by means of spindle 230, allowing the free flow of air into the connecting tube 242. The flow of air via air inducer outlet 220 into container 212 releases the air lock within that container, and liquid begins to drain out by the scavenger tube 214, spout attachment 216 and sight tube 180 into the lower container 218, where the liquid gradually accumulates until the upper container 212 is completely empty.

Because the volume of liquid (between the high mark and the low mark) in container 218 is already known, liquid from the upper 20 litre refill container 212 should never fill to the fluid ports 227 where liquid enters the upper chamber 226 of the auto-refill valve.

However, should the liquid level rise about the fluid ports 227, the auto-refill valve will fill with liquid, causing the float 232 to rise and closing off the air supply to the upper container 212 via connecting tube 242. When the contents of the upper container 212 have fully drained, it can be replaced, whilst the pump continues to operate from the now refilled lower container 218.

Advantageously, a bank of 20 litre refill containers 212 can be provided in a cradle system as illustrated in Figure 18. Only the refill containers 212 on the upper level of the cradle need ever be replaced, on a rotating system.

In Figure 19, a third embodiment of a calibration system for the chemical metering pump according to the present invention is illustrated. Figure 19 (a) illustrates a manual calibration system, whereas Figure 19 (b) illustrates an auto calibration system. In both cases, the calibration system is designed to suit the application of the pump to a 200 litre drum, similar to that described above and illustrated in Figures 6 and 7. The manual calibration system shown in Figure 19 (a) is therefore similar to the second embodiment of the calibration system 110 illustrated in Figures 13 and 14, and therefore the similar parts

shown in Figure 19 are identified with the same reference numerals.

Both the auto and manual versions of the calibration system 250 shown in Figures 19 (a) and (b) respectively, are in cartridge form and are housed in a shroud 252 having a flange 254 to which a chemical metering pump in accordance with the present invention is mounted. Both the manual and auto calibration options are provided in a cartridge housing 256, that is similar to the outer casing 116 of the second embodiment illustrated in Figure 13. Within the cartridge housing 256 of the manual option, there is provided a hollow inner valve stem 118 and a calibration indicator rod 120 similar to that of the system illustrated in Figure 13. A float 122 is provided at the lower end of the calibration indicator rod 120, which is free to slide up and down within the inner valve stem 118. A valve 258 provided at the lower end of the valve stem 118 seats on a drum connector port 260 in its close position. With valve 258 in its open position (as shown in Figure 19 (a)), liquid chemical floods both the interior of the hollow inner valve stem 118 and the annular volume between the cartridge housing 256 and the valve stem 118. However, when the valve stem 118 is lowered manually so that valve 258 seats against the drum connector port 260, liquid chemical can be drawn from within the hollow valve stem 118 only. The manual calibration system 250 illustrated in Figure 19 (a) is operated in a similar manner to the system 110 illustrated in Figures 13 and 14 and will not be described again here. As with the embodiment illustrated in Figures 13 and 14, the main function of the manual calibration system is to enable a user to measure the rate at which the chemical metering pump discharges liquid chemical into a flow stream. It also allows the user to see the volume of liquid remaining in the drum from which the pump is discharging, ie a 200 litre dangerous goods drum-commonly known as a Mousser.

Advantageously, a simple wrap-around removable filter screen 262 is incorporated into the base of the cartridge housing 256. When the cartridge housing is inserted into the shroud 252 the screen 262 is received within a screen chamber 264 provided within the bottom of the shroud 262 adjacent the pump flange 254. Filter screen 262 prevents any contaminants from entering into the pump suction port, thus ensuring that the chemical metering pump can remain submerged in the drum at all times and minimising operator contact with hazardous liquid chemicals.

In the auto calibration option illustrated in Figure 19 (b), a solenoid actuator 266 operates a valve 268 via a valve connecting rod 270. When an actuating signal is received by the solenoid actuator 266 from controller 240, connecting rod 270 moves the valve 268 downwards so that it seats against and seals off the drum connector port 260. A slidable float 272 is provided on the valve connecting rod 270 and is free to move up and down depending on the liquid level within the cartridge housing 256. An optical detector 274 is provided near the bottom of the cartridge housing 256 for detecting the position of the float 272. The auto calibration system 250 operates as follows.

During normal operation when the chemical metering pump is running, the connecting rod 270 remains in its up position and liquid is drawn into the system through the drum connector port 26. However, when a signal is transmitted from the controller 240 to commence the calibration cycle, solenoid actuator 266 is activated and connecting rod 270 forces valve 268 to seal off the drum connector port 260. In this position, the chemical metering pump will draw liquid directly from within the cartridge housing 256. As the liquid level descends, the float 272 also moves downwards and will eventually interrupt the light beam of optical detector 274. At the same time that solenoid actuator 266 is actuated, a first timer within the controller 240 is activated. When the float 272 is detected by the detector 274, a detection signal is transmitted to the controller 240 which stops the first timer and records the total time elapsed from commencement. It also triggers a second timer. Once the float 272 drops below the light beam of detector 274, the second timer also stops and controller 240 records the time elapsed from its commencement. At this point, solenoid actuator 266 is deactivated, causing the valve 268 to be lifted from the drum connector port 260. This enables the liquid chemical from the drum to re-fill the cartridge housing 256 until it reaches the same level as the contents of the drum Controller 240 uses the time elapsed from the first timer, together with the frequency of the chemical metering pump, to calculate the volume pumped and transmits this data to a data logger or interface computer. Using the volume pumped and the time recorded from the first timer, the controller is also able to calculate the volume of liquid remaining in the drum and also relays this information to a sight bar indicator, and/or the data logger or interface computer. Controller 240 is also able to monitor the operation of the auto calibration system 250, and to detect the following operating conditions: 1 1 1 I . 1_ Float remains idle or fails to Pump failure: Alarm Switch to standby interrupt the beam within a predetermined time Float interrupts the beam before a Excessive Alarm Shut down predetermined time is reached discharge Float fails to interrupt the beam Failed to reach Adjust Up/down; outside a set band of time set point recalibrate Float interrupts beam instantly Low volume Alarm Switch to standby

From the above description of several embodiments of the chemical metering pump it will be apparent that it provides a number of significant advantages over prior art chemical metering pumps. In particular, it substantially eliminates the need for"double handling" as it enables liquid chemical to be metered directly from the transport/storage containers in which it is delivered to the water treatment plant. The pump can be readily modified to suit different sized containers. In addition, multiple pumps can be controlled using a single remote electronic controller.

Numerous variations and modifications will suggest themselves to persons skilled in the arts relating to chemical metering pumps, in addition to those already described, without departing from the basic inventive concepts. For example, any suitable actuator may be employed in the chemical metering pump for driving the diaphragm in a reciprocating motion, for example, an hydraulic or pneumatic actuator. All such variations and modifications are to be considered within the scope of the present invention, the nature of which is to be determined from the foregoing description and the appended claims.