IE900428A1 - A liquid metering apparatus - Google Patents

Abstract

An apparatus (1) and method for metering milk transferred between a farm vat (2) and a tank (3) of a milk tanker. A flexible hose (7) is inserted in the farm vat (2) and milk is delivered by a pump (28) through a milk transfer pipe (5) to the tank (3). Mounted in the pipe (5) is a buffer vessel (12) to vent entrained air from the milk prior to passing the milk through a flowmeter (10) to the tank (3). Control means regulates the flow of milk to the tank (3) in a controlled manner in response to milk conditions sensed by a number of probes (level sensors 18, 19, 20, temperature probe 21, pH probe 22, air sensor 25, and milk sensor 30). Accurate metering of milk is thus achieved.

Description

An Apparatus for Batch Metering of Milk This invention relates to an apparatus for metering a liquid transferred between two containers, and in particular where the liquid is milk.

According to the invention there is provided an apparatus for batch metering of milk transferred between two containers, namely, a milk supply container and a milk receiver container, the apparatus comprising: a milk transfer pipe having an inlet to receive milk from 10 the supply container and an outlet to discharge milk to the receiver container, a flow meter mounted in the pipe, a buffer vessel mounted in the pipe upstream of the flow meter, milk level sensing means in the buffer vessel, gas vent means for the buffer vessel, IE 90428 - 2 an air detector probe mounted in the pipe upstream of the buffer vessel, and control means for regulation of milk flow through the apparatus in response to signals received from the air detector probe and level sensing means and for adjustment of the recorded quantity of a milk batch through the flow meter having regard to the initial and final quantities of milk in the apparatus.

In one embodiment of the invention milk level sensing means 10 comprises a working level probe and a low level probe mounted below the normal working level probe in the buffer vessel.

Ideally a high level probe is also provided mounted above the working level probe in the buffer vessel.

In a further embodiment a pH sensor is provided mounted in the 15 buffer vessel. A temperature probe may be provided mounted either in the buffer vessel or in the pipe between the buffer vessel and the flow meter.

In another embodiment a discharge pipe is mounted between an outlet of the milk receiver container and an inlet of the buffer vessel, a stop valve being provided in the discharge pipe.

IE 90428 - 3 In another embodiment, a milk transfer pump is provided for delivery of milk through the pipe.

In a further embodiment, vacuum means is provided to selectively apply a vacuum to the buffer vessel to vent air from the buffer vessel.

In a preferred embodiment, means is provided to apply a vacuum to the milk receiver container.

In another embodiment an anti-vortex device is mounted at an outlet of the buffer vessel.

Alarm means may be provided, said alarm means comprising an audible and/or visual alarm to give indication when air is detected at the air detector probe. There is preferably also means to indicate invalid metering if air is detected at the flow meter, which includes an additional air detector probe located at the flow meter.

In another embodiment the metering apparatus incorporates cleaning means .

In another aspect, the invention provides a method for metering milk transferred between two containers with the apparatus described above, the method comprising the steps of; IE 90428 - 4 delivering the milk from the milk supply container to the buffer vessel, venting entrained air from the milk in the buffer vessel, and metering milk from the buffer vessel to the milk receiver container in a controlled manner in response to milk conditions sensed at the probes.

The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a diagrammatic illustration of a milk metering apparatus according to the invention, Fig. 2 is a diagrammatic illustration of another milk 15 metering apparatus, Fig. 3 is a diagrammatic illustration of a further milk metering apparatus , Fig. 4 is a diagrammatic side view of a buffer vessel forming portion of another milk metering apparatus, IE 90428 - 5 Figs. 5 and 6 diagrammatically illustrate cleaning systems for a milk metering apparatus according to the invention, and Fig. 7 is a detail side sectional view of portion of a 5 milk detector probe forming portion of the milk metering apparatus .

Referring to the drawings, and initially to Fig. 1 thereof, there is illustrated a milk metering apparatus according to the invention indicated generally by the reference numeral 1 for metering milk transferred between a milk supply container such as a farm vat 2 and a milk receiver container such as a tank 3 on a milk tanker vehicle. The apparatus 1 comprises a milk transfer pipe 5 having an inlet 6 to which is attached a flexible hose 7 for insertion into the farm vat 2. An outlet 8 of the milk pipe 5 discharges into the tank 3. A flow meter is mounted in the pipe 5. Upstream of the flow meter 10 is a buffer vessel 12 having vent means which in this case comprises a vent pipe 13 closed by a vent valve 14, the vent pipe 13 having an inlet 15 within the vessel 12 and an outlet 16 adjacent a top of the tank 3. In some cases the outlet 16 may be open to atmosphere. A number of milk level detector probes are' mounted in the vessel 12, namely a high level probe 18, a normal working level probe 19 and a low level probe 20. Downstream of the vessel 12 a temperature probe 21 is mounted in the pipe 5. A pH probe 22 is provided in the vessel 12.

IE 90428 - 6 An anti-vortex device 24 is mounted at an outlet 23 of the vessel 12. An entrained air detector probe 25 is mounted in the milk pipe 5 upstream of an inlet 26 to the vessel 12. A pump 28 is provided for delivery of milk through the milk pipe . A milk detector probe 30 is mounted in the pipe 5, downstream of the flow meter 10. A number of valves 31 to 35 are provided on the milk pipe 5, these valves being automatically operable by a control means (not shown) in response to signals received from the probes (18, 19, 20, 21, 22, 25, 30) to regulate the flow of milk through the apparatus 1.

It will be noted that a discharge pipe 37 communicates between an outlet 38 of the tank 3 and the inlet 26 of the vessel 12. The valve 35 is located in the discharge pipe 37. The valve 34 downstream of the meter 10 communicates through a return pipe 41 with the inlet 6 of the milk pipe 5. Also the valve 33, when open, allows delivery of milk back to the inlet 6 from the outlet 23 of the vessel 12.

It will be noted that the flow meter 10 is a magnetic flow meter fitted close to the outlet 23 of the vessel 12 so that it fills with milk when the vessel 12 is filled. It will be appreciated that any other suitable type of flow meter may be used such as for example, a turbine or a rotary piston flow meter.

IE 90428 - 7 In use, the vent valve 14 and the stop valve 31 are opened, all the other valves being closed. Milk is pumped into the vessel 12 by starting the pump 28 and running it initially at low speed. When the high level probe 18 in the vessel 12 detects milk the pump 28 is stopped and valve 14 is closed. After a delay period a pH reading is taken by the pH probe 22 and a temperature reading is taken by the temperature probe 21. If the milk is not within the required limits of acidity and temperature, the milk collection is aborted by opening the valve 33 to dump the milk back into the farm vat 2. If the acidity of the milk is acceptable and milk is detected at the milk detector probe 30, after opening the valve 32 the pump 28 is restarted at low speed initially for a short period and then at full speed. Milk is thus delivered through the vessel 12 and meter 10 which will record the volume. If entrained air is detected at the air detector probe 25 the pump 28 is stopped and an audible alarm is actuated. After a delay period, typically of a couple of seconds, the pump 28 is restarted at full speed. If air is again detected, the same cycle is followed. If the problem occurs again the control means records the metered amount as being possibly incorrect and the milk transfer is resumed if requested by the operator.

Should the milk level in the vessel 12 drop to the working level probe 19, the valve 32 is closed, the pump 28 is reduced to low speed, and the vent valve 14 is opened until the milk level rises again to the high level probe 18. Then the valve IE 90428 is closed and after a delay of one or two seconds the valve 32 is opened. The pump 28 is again increased to full speed. If the milk level does not rise to the high level probe 18 after a fixed time period, the control means recognises the end of the milk collection. Then the pump 28 is operated at full speed for a fixed period to scavenge the inlet portion of the milk pipe 5. Then the pump 28 is again dropped to low speed and the vent valve 14 is closed and the valve 32 opened until the level drops to the low level probe 20, the control means then stopping the pump 28. Alternatively, the pump may be operated until no milk is detected at the probe 30 downstream of the flow meter 10 for two or three seconds.

It will be noted that the facility to run the pump 28 at high and low speeds as described above is optional and the pump 28 may in some cases only be operated at one speed.

It will be appreciated that the amount of milk in the milk pipe 5 between the low level probe 20 and the meter 10 is known. This amount is added on to the collection amount for the first collection and the milk is left in the milk pipe 5 until the next collection. If the milk is alternatively flushed out of the pipe 5 then this amount is added to the amount for every collection. Metering stops if the milk probe 30 detects air and is resumed as soon as the milk probe 30 detects milk again. If the milk probe 30 detects entrained air an alarm is sounded to indicate an invalid collection and IE 90428 the pump 28 is stopped. The operator may re-start the milk collection but the control means will register the metered amount as being incorrect.

The control algorithm for operation of the milk metering 5 apparatus 1 will now briefly be described.

Initially all probes should register no milk.

(A) FILL.

Open vent valve 14 and operate the pump 28 at low speed until milk is registered at the working level probe 19 for n seconds, where n is calculated as: % [(volume above probe 19) 4- Flowrate] or until milk is detected at the high level probe 18, then go to FULL.

If there is no milk at the air detector probe 25 for n seconds (say 5), then go to EMPTY-PAUSE.

(B) FULL.

If there is no milk at the low level probe 20 or the milk detector probe 30 then stop pump 28 and alert operator. Close vent valve 14. If no milk at working level probe 19 go to FILL. Operate pump 28 at low speed for a short period (say 1 second) to pressurise the buffer vessel 12 to prevent backflow when valve 32 is opened. Go to FLOW.

IE 90428 - 10 (C) FLOW.

Operate pump 28 at fast speed. When no milk is detected at the working level probe 19 go to REFILL. If bubbles are detected at the air detector probe 25 or milk detector probe , alert operator. Register an invalid milk collection if no milk is detected at the empty level probe 20 or the milk detector probe 30.

(D) REFILL.

Close the valve 32 then open the vent valve 14 after 1 second 10 (to prevent backflow). Go to FLOW when milk is detected at the working level probe 19 for n seconds (calculation of n see FILL) or when milk is detected at the high level probe 18.

If no milk is detected at the air detector probe 25 for n seconds (say 10 seconds) then go to EMPTY-PAUSE.

(E) EMPTY-PAUSE.

Operate pump 28 at low speed. Close vent valve 14 and valve 32. It will allow pressure to build up in the buffer vessel 12 for 1-2 seconds. Then goto EMPTY.

(F) EMPTY.

Open valve 32 and meter at low pump speed until no milk is detected at the low level probe 20. If no milk is detected at the milk detector probe 30 register invalid collection. Add prime quantity to metered amount (equal to volume in pipe IE 90428 between the low level probe 20 and the valve 32). Go to FLUSH.

(G) FLUSH.

Open valve 32 until no milk is detected at the milk detector 5 probe 20 for a preset time, long enough to ensure milk pipe 5, at least to valve 32, is empty. Close all valves and stop pump 28 after 1 second (to prevent backflow).

Note that the milk detector probe 30 prevents the flowmeter 10 from counting when there is no milk in the pipe 5. The flow meter 10 can count backwards or forwards so that any backflow will be compensated out.

An alternative end to the milk transfer is to meter until there is no milk in the pipe 5. The downstream milk detector probe 30 stops the flowmeter 10.

A further end to the milk transfer is to stop the pump, close valve 32 and open valve 14 when no milk is detected at low level probe 20. At this point the prime quantity, which will equal the amount of milk between low-level probe 20 and valve 32 is added onto the metered amount. In this case the next collection of milk will start with milk in the metering pipe between low-level probe 20 and valve 32 and will end in the same state, so that the prime quantity does not need to be added onto the metered amount. The apparatus has means to •E 90428 detect an un-primed system either by detecting no milk at milk probe 30 at the start of the collection or by recognising the first collection from an initialised state or by instruction from the operator.

In this case, repeatable metering will only be obtained if the response of the equipment is instantaneous (low level probe 20, valves 32 and 14 and pump 28). However, in practise there is a finite response time from the milk probes, valves can take over a second to close and pumps may take several seconds to stop. In a practical situation, therefore, the level will drop below low-level probe 20 and this amount will vary due to variations in the pumping rate and response times of the probe and valves.

The prime quantity will therefore be the amount of milk between valve 32 and some level below low-level probe 20. Providing that the pump flow-rate, valve and probe response do not vary between collections, the metering system will give repeatable measurements .

In practise there is always a variation due to rotor wear in the pump, pump speed variations, variation in the air pressure or spring pressure in the valves etc. An error will therefore be introduced which may not be obvious in a small series of tests, but which may become significant over time.

IE 90428 This invention compensates for this variation as follows: The control means contains two electronic counters Cl and C2 associated with the flow meter 10 which are switched by the low-level probe 20. When probe 20 detects milk, milk is metered by Cl. When no milk is detected at probe 20, milk is metered by C2. Cl and C2 are set to zero at the start of every collection. At the start of the first collection or if milk probe 30 detects no milk at the start of a collection the Prime Quantity (PQ) is set equal to the amount of milk between probe 20 and valve 32. At the end of each collection, when no milk is detected at probe 20, valve 14 is opened, valve 32 is closed and the pump 28 stopped. Sufficient time is given for the valves and pump to stop (typically 1 or 2 seconds), during which time any milk flowing through the meter is metered by C2. The amount of milk collected is then set equal to the metered amount in Cl plus the prime quantity PQ. The PQ is then set equal to C2. This means that for the first collection the prime quantity will be the amount between probe 20 and valve 32 and for the second and subsequent collections the prime quantity will be the volume between probe 20 and the actual level of milk below probe 20 as at the end of the previous collection (ie the amount metered into C2 during the previous collection).

IE 90428 - 14 The metered quantity of milk is thus calculated as follows:PQ = volume between probe 20 and valve 32 Cl = metered quantity while milk is above probe 20 C2 = metered quantity when milk is below probe 20 Ml = milk for 1st farmer (buffer vessel 12 empty at start) Mn = milk for 2nd, 3rd..... farmers Ml = Cl + PQ Mn = Cl + C2 Note that C2 is the metered quantity below probe 20 for the previous collection, whereas Cl is the metered quantity while milk is above probe 20 for this collection.

This method compensates for pump or valve response times or variations in these response times. It does not compensate for variations in the response time of probe 20 which should therefore be a fast-acting probe with a response time of better than .02 seconds, plus or minus 10%, which would give a repeatability of plus or minus .1 litres at a flow rate of 3000 litres per minute. It is also essential that the probe does not measure milk foam. Switching between counters Cl and C2 must be repeatable within .01 seconds to give an overall repeatability of plus or minus .15 litres at a flow rate of 3000 litres per minute (or better than .01 litres at a flow rate of 500 litres per minute).

IE 90428 It will be appreciated that the apparatus also allows milk to be transferred from the tank 3 to the farm vat 2 or any other suitable holding tank. This can be done by gravity feed where the farm vat 2 or holding tank is lower than the tank 3 or alternatively, by means of the pump 28, where necessary. Milk can be delivered directly between the two tanks through valves 35 and 31 or alternatively, through valves 32 and 34. Advantageously however the milk can be directed back through the meter 10 if desired, for example, by opening valves 32 and 33, all the other valves being closed. The milk can also be delivered between the tanks through the buffer vessel 12 by opening valves 35 and 34, the other valves being closed. Alternatively the hose 7 may be coupled to an outlet flange 36 on the pipe 5 and milk delivered through the valve 32 and flow meter 10.

Referring now to Fig. 2 there is illustrated another milk metering apparatus 50. This is largely similar to the milk metering apparatus described with reference to the previous drawing and like parts are assigned the same reference numerals. The essential difference with this apparatus 50 is that instead of a pump to deliver milk through the milk pipe 5, a partial vacuum in the tank 3 sucks milk through the milk pipe 5, and also removes air from the buffer vessel 12 through the vent valve 14.

IE 90428 - 16 Operation of the milk metering apparatus 50 is similar to operation of the milk metering apparatus described previously.

The control algorithm for vacuum collection will now be described briefly.

(A) At start up all probes should register no milk.

(B) FILL.

Open vent valve 14 until milk is detected at the low level probe 19 for n seconds (where n is calculated as 1/2 (volume above probe 19/flowrate) or until milk is detected at the high level probe 18. Then go to FULL.

If there is no milk at the air detector probe 25 for n seconds (say 5), then go to EMPTY-PAUSE.

(C) FULL.

Wait for n seconds for bubbles to come out of milk, then go to FLOW. Alert operator if there is no milk at the milk detector probes 30 or the low level probe 19. If there is no milk at low level probe 19, then go to FILL.

(D) FLOW.

Close vent valve 14 then open valve 32 after one second (to prevent the backflow) . When no milk is detected at the low level probe 19 go to REFILL. If bubbles are detected at the air detector probe 25 or the milk detector probe 30 or empty IE 90428 - 17 level probe 20, alert operator. Register invalid collection if no milk is detected at the milk detector probe 30 or the empty level probe 20.

(E) REFILL.

Close valve 32 then open vent valve 14 after 1 second (to prevent backflow) . Go to FLOW when milk is detected at the low level probe 19 for n seconds (n calculated as at Fill above) or when milk is detected at the high level probe 18. If there is no milk at the air detector probe 25 for n seconds (say 5) then go to EMPTY-PAUSE.

(F) EMPTY-PAUSE.

Close vent valve 14 and valve 32. Wait 1 or 2 seconds to prevent backflow then go to EMPTY. Alternatively a longer pause may be allowed to let the vacuum build up.

(G) EMPTY.

Open valve 32 and meter until no milk is detected at the low level probe 20. If no milk is detected at the milk detector probe 30 register invalid collection. Add prime quantity to metered amount (equal to volume in pipe between the low level probe 20 and the valve 32). Go to FLUSH. If the low level probe 20 does not go dry for n seconds (say 10) then go to REFILL.

IE 90428 - 18 (H) FLUSH.

Open valve 32 until no milk is detected at the milk detector probe 30 for 2 seconds.

Note that the milk detector probe 30 prevents the flow meter 5 10 from counting when there is no milk in the pipe 5. The flow meter 10 can count forwards or backwards so that any backflow will be compensated out.

An alternative end to the milk transfer is to meter until the pipe is dry (ie. meter during FLUSH). The milk detector probe stops the flowmeter 10.

The control algorithm for delivery of milk from the tank 3 to a storage or holding tank will now be briefly described. (i) GRAVITY DELIVERY/SUCKED OFF DELIVERY (A) At start all probes must register no milk.

(B) Initially all valves are closed. Open valve 32 and vent valve 14 until milk is detected at the working level probe 19 then close vent valve 14. Start metering as soon as milk is detected at low level probe 20. Open valve 33. As soon as working level probe 19 detects no milk, close valve 33 and open vent valve 14 and leave it open until the working level probe 19 detects milk again. If the working level probe 19 IE 90428 does not detect milk after a timeout, open valve 33 and meter, until no milk is detect at probe 20.

(C) Adjust delivered amount by volume in vessel 12 up to low level probe 20.

Note that if bubbles or no milk are detected at the milk detector probe 30 or low level probe 20 then an invalid delivery is indicated.

Suck off pump should be centrifugal type located at a level below tank 3 so that it will prime. (ii) PUMPED DELIVERY - BUFFER VESSEL EMPTY Initially all valves are closed and probes should detect no milk. Open valve 35 and valve VI and start pump 28. Close valve 14 when working level probe 19 detects milk. Open valve 34 and start metering. When probe 19 detects no milk, close valve 34 and open valve 14 until probe 19 detects milk again and then resume metering with valve 14 closed and valve 34 open. If probe 19 detects no milk after a timeout, close valve 14 and open valve 34, metering until no milk is detected at probe 20. Adjust metered amount by quantity of milk between probe 20 and valve 34. Stop pump and close valves where no milk is detected at probe 30.

IE 90428 - 20 (iii) PUMPED DELIVERY - BUFFER VESSEL PRIMED This is as for a collection with buffer vessel 12 primed, except that valves 35 and 34 are operated instead of valves 31 and 32. (iv) SUCKED-OFF DELIVERY NO PUMP OR PUMP BYPASSED As for (ii) or (iii) - Centrifugal-type suck-off pump should be on for the whole delivery and located below level of tank 3 so that it will prime.

Referring now to Fig. 3 there is illustrated another milk metering apparatus 60. This is largely similar to the milk metering apparatus described with reference to Fig. 2 and like parts are assigned the same reference numerals. A vacuum pump (not shown) is provided to apply a vacuum through a vacuum line 61 to the vessel 12 through the vent valve 14, and to the tank 3 through valve 63. An interceptor vessel 65 is provided in the vacuum line 61 to prevent any carry over of milk which may be entrained in air extracted from the vessel 12 or tank 3. The interceptor vessel 65 is a cylindrical container with a level probe 66 at a top of the container. The vacuum pipe 61 projects downwardly through a top of the vessel 65 and has an outlet end 67 adjacent a lower end of the interceptor vessel 65. An air pipe 68 communicates between a top of the interceptor vessel 65 and the vacuum pump. The interceptor IE 90428 - 21 vessel 65 causes a sudden change of direction of fluid flow through the interceptor vessel 65 and this causes milk entrained in air passing through the interceptor vessel 65 to be deposited in the interceptor vessel 65. An automatic valve 69 is provided at an outlet 70 on the milk pipe 5 downstream of the vessel 12.

Operation of the milk metering apparatus 60 is similar to operation of the milk metering apparatus described with reference to the previous drawings.

Referring now to Fig. 4 there is illustrated an alternative arrangement of buffer vessel for use with the milk metering apparatus, indicated generally by the reference numeral 80. In this case a milk outlet pipe 81 from the vessel 80 in which the flow meter 10 is mounted, is inclined at 80° to the vertical in order to facilitate a flow of air from milk in the pipe back into the vessel 80 during initial filling of the vessel 80 and during operation of the milk metering apparatus.

Referring now to Fig. 5 there is illustrated a cleaning system for the milk metering apparatus described previously. Like parts are assigned the same reference numerals. In operation the vent pipe 13 doubles as a cleaning line and the hose 7 is coupled to the vent line 13. Cleaning fluid is delivered to the vent line 13 for delivery back through the vent valve 14 and hose 7 to the vessel 12, and for delivery to the tank 3.

IE 90428 - 22 A spray ball is fitted at the inlet 15 of the vent pipe 13 within the vessel 12. The outlet of the vent pipe 13 within the tank 3 is also fitted with a number of spray heads for distributing cleaning fluid within the tank 3. It will be noted that the vent valve 14 is pulsed on and off during the cleaning process in order to ensure that both the hose 7 and vessel 12 are thoroughly cleaned. Manual valves 85 are provided.

Referring now to Fig. 6 there is illustrated an alternative 10 cleaning system for the milk metering apparatus which operates on the vacuum system. In this case an inlet 91 to the vessel is blanked off and a flushing line 92 connected into the vent pipe 13. In use cleaning fluid is delivered in through the flushing pipe 92 for delivery through the vent pipe 13 to the spray balls in the vessel 12 and tank 3. Run off is discharged through the hose 7 . The vent valve 14 is pulsed on and off during cleaning. Note this system is not suitable for the metering apparatus which incorporates a pump upstream of the inlet 91 or having a sampler upstream of the inlet 91.

Referring now to Fig. 7 there is illustrated portion of the milk detector probe 30 used with the milk metering apparatus described previously with reference to the drawings. The milk detector probe 30 has a stainless steel probe 95 sheathed in an insulating sleeve 96. An outer end of the insulating sleeve 96 projects through a sidewall of the milk pipe 5 and IE 90428 is housed within the milk pipe 5. A free end 97 of the probe 95 is exposed. This exposed portion has a surface area of less than 3 mm2 . Response time of the probe 95 is less than 10-4 seconds; that is it should detect the transition from no milk to milk (or vice versa) in less than 104 seconds. In use the probe 95 measures the conductivity of milk between the free end 97 of the probe 95 and the stainless steel milk pipe 5. The probe 95 should not detect water or milk foam (unless these contain conductive additives such as salt).

The invention is not limited to the embodiments hereinbefore described which may be varied in both construction and detail.

IE 90428

Claims (10)

1. An apparatus for batch metering of milk transferred between two containers, namely, a milk supply container and a milk receiver container, the apparatus comprising; 5 a milk transfer pipe having an inlet to receive milk from the supply container and an outlet to discharge milk to the receiver container, a flow meter mounted in the pipe, 10 a buffer vessel mounted in the pipe upstream of the flow meter, gas vent means for the buffer vessel, milk level sensing means in the buffer vessel, an air detector probe mounted in the pipe upstream 15 of the buffer vessel, and control means for regulation of milk flow through the apparatus in response to signals received from the air detector probe and level sensing means and for adjustment of the recorded quantity of a milk 20 batch through the flow meter having regard to the initial and final quantities of milk in the apparatus. IE 90428

2. 5

3.

4. 10 5. 6. An apparatus as claimed in claim 1 wherein the liquid level sensing means comprises a normal working level probe and a low level probe mounted below the normal working level probe in the buffer vessel. An apparatus as claimed in claim 2 wherein a high level probe is provided, mounted above the working level probe in the buffer vessel. An apparatus as claimed in any preceding claim wherein a pH sensor is provided mounted in the buffer vessel. An apparatus as claimed in any preceding claim wherein a temperature sensor is provided mounted either in the buffer vessel or in the pipe between the buffer vessel and the flowmeter. An apparatus as claimed in any preceding claim wherein a discharge pipe is mounted between an outlet of the milk receiver container and an inlet of the buffer vessel, a stop valve being provided in the discharge pipe. An apparatus as claimed in any preceding claim wherein a milk transfer pump is provided for delivery of milk through the pipe. IE 90428 - 26 8. An apparatus as claimed in any preceding claim wherein vacuum means is provided to selectively apply a vacuum to the buffer vessel to vent air from the buffer vessel. 9. An apparatus as claimed in any preceding claim wherein

5. Means is provided to apply a vacuum to the milk receiver container.

6. 10. An apparatus as claimed in any preceding claim wherein an anti-vortex device is mounted at an outlet of the buffer vessel. 10

7. 11. An apparatus as claimed in any preceding claim wherein alarm means is provided to give indication when air is detected at the air detector probe.

8. 12. An apparatus substantially as hereinbefore described with reference to the accompanying drawings. 15

9. 13. A method for metering milk transferred between two containers with the apparatus claimed in any preceding claim, the method comprising the steps of; delivering the milk from the milk supply container to the buffer vessel, IE 90428 - 27 venting entrained air from the milk in the buffer vessel, and metering milk from the buffer vessel to the milk receiver container in a controlled manner in response to milk conditions sensed at the probes.

10. 14. A method substantially as hereinbefore described with reference to the accompanying drawings.