WO2004042329A1

WO2004042329A1 - Liquid flow measuring apparatus

Info

Publication number: WO2004042329A1
Application number: PCT/GB2003/004803
Authority: WO
Inventors: Robin William Sadler
Original assignee: Acos Limited
Priority date: 2002-11-08
Filing date: 2003-11-06
Publication date: 2004-05-21
Also published as: GB0226087D0; AU2003286234A1

Abstract

Apparatus for measuring the flow rate of a liquid, particularly milk from milking apparatus, comprises a measuring chamber (8; 108) which receives the liquid and an outlet (24; 124) through which the liquid can drain out of the measuring chamber. The outlet is, in use, occluded by a buoyant plug (32; 132) to an extent related to the flow of liquid into the measuring chamber, and includes measuring means for measuring the height of liquid in the chamber, and hence flow rate.

Description

Title Liquid Flow Measuring Apparatus

Field of the Invention

This invention relates to apparatus for measuring the flow rate of a liquid."

Background to the Invention

The invention is particularly, but not exclusively, applicable to the measurement of animal milk yields during the milking process.

The measurement of milk yields with milking animals such as cows, goats or sheep is used fn the management of milk production.

One known type of automatic milk production measuring device uses a vessel which is filled with milk from the animal and, once full, drained under gravity. The amount of milk produced will be given by the number of times the vessel is filled, and the flow rate by the time taken for each filling. However, the production of milk is not measured while the vessel is draining so that, at high flow rates, errors can occur.

Another type of automatic milk measuring device has a tipping trough which collects the milk from the animal. When the trough is full it is tipped so that the milk empties from the trough fairly quickly. The. trough then returns to its normal position to collect further milk. However, this arrangement also gives rise to problems with high flow rates because the resultant frequent tipping of the trough can set up waves in the milk in the trough so that the trough is not filled properly between successive tripping actions.

US 5877417 shows a device which provides a continuous milk flow measurement. To that end milk is supplied to a measuring chamber through which the milk drains under gravity. The rate of draining of said of milk will be related to the amount of milk in the chamber, so that, for a given flow rate into the chamber, the milk in chamber will find an equilibrium level, in which the rate at which milk leaves the chamber is the same as the flow rate from the animal. Measurement of the level of milk in the chamber therefore provides a measurement of the flow rate. However, no milk will accumulate in the chamber if the rate at which milk enters is less than the rate at which milk leaves the sunstantially empty chamber. The apparatus is thus not able to measure low flow rates.

Summary of the Invention

According to the invention, there is provided apparatus for measuring the flow rate of a liquid, the apparatus comprising a measuring chamber having an inlet for receiving liquid and an outlet through which liquid can drain out of the chamber, the apparatus further comprising a float and plug means at least partially situated within the chamber and operable to cause the outlet to be occluded to an extent which decreases with increasing flow of liquid through the inlet, the apparatus including measuring means for measuring the height of liquid in the chamber, thereby to measure liquid flow.

When such apparatus is being used to measure low flow rates, the plug means causes the outlet to be occluded to an extent sufficient to allow liquid to accumulate in the chamber, thus enabling measurement to be made. For higher flows, however, the plug means exposes a larger area of the outlet so that liquid can drain from the chamber at a higher rate. The invention thus enables a^r wide range of flow rates to be measured.

Preferably, the plug means and outlet are of complementary shapes so that, with no liquid in the chamber, the plug means completely occludes the outlet.

Thus even a very small flow rate into the chamber will cause an accumulation of liquid until the plug means is unseated. The plug means may to an advantage be tapered from top to bottom. As a result, a given vertical movement of the plug means will cause a smaller increase of the perpendicular distance between the outlet and -the plug means. Consequently, when a low flow rate causes the plug means to be unseated, this does not necessarily immediately drain the chamber, but instead allows liquid in the chamber to reach an equilibrium level in which the flow rate into the chamber is matched by the rate of drainage.

Conveniently, the float and the plug means are incorporated into a single buoyant member.

The measuring means may directly measure the level of liquid in the chamber, but preferably measures the distance of at least part of the buoyant member above a reference level.

To that end, the measuring means may to an advantage comprise a magnetic field source carried by the buoyant member and a magnetic field measuring device in a position fixed relative to the chamber.

Preferably, the field source comprises a permanent magnet, conveniently rare earth magnet.

The magnet may to advantage be fully contained within the buoyant member.

This avoids any contact of the liquid with the magnet, and therefore reduces the chance of contamination of the liquid.

Preferably, the measuring chamber is defined by a housing^' which also defines a further chamber beneath the measuring chamber outlet, said outlet constituting an inlet to the further chamber, the further chamber also having an outlet and a receptacle for receiving a sample of the liquid flowing through the further chamber. The receptacle can be used to collect a sample of liquid passing through the apparatus. Since the receptacle and flow measuring apparatus are within a common housing, both can be cleaned in the same cleaning operation.

Preferably, the apparatus includes diversion means for diverting a portion of the liquid flowing out of the measuring chamber into the receptacle, whilst allowing the rest of the liquid to reach the outlet of the further chamber.

The sample thus collected by the receptacle will be representative of all of the liquid flowing through the apparatus.

The diversion means conveniently comprises one or more formations, such as fins, on the plug means.

The housing may include an outlet valve allowing the receptacle to be drained and hence the sample to be collected.

The buoyant member may to advantage be one of a plurality of such members, the members being interchangeable so that any one member can be situated in the measuring chamber, and having different shapes, thereby to enable the sensitivity of the apparatus to be altered by changing the buoyant member.

The apparatus preferably includes a deflector plate between the inlet of the measuring chamber and the float, the deflector float being arrange to separate entrained gas from the flow of liquid into the measuring chamber.

Preferably, the apparatus is a milk meter for measuring the yield of milk from an animal.

Brief Description of the Drawings The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: -

Figure 1 is an exploded isometric view of a milk flow meter in accordance with the invention;

Figure 2 is a cutaway, simplified diagrammatic side view of the meter when no milk is flowing therethrough;

Figure 3 is a corresponding view showing the position of various components of the meter when milk is flowing;

Figure 4 is a view, corresponding to figure 2, of a second embodiment of meter in accordance with the invention; and

Figure 5 is a cutaway plan view of the meter of figure 4.

Detailed Description

With reference to figures 1 and 2, a milk flow meter has an annular housing 1 having a slightly domed lid 2 attached to the top of the main body portion 4 to the bottom of which a base 6 is attached. The housing defines an upper, annular measuring chamber 8 and a further chamber 10 immediately below the measuring chamber 8, and has an upper inlet 12 for connection to a milking claw. Milk leaves the housing 1 through a lower outlet 14 in the base 6.

The lid 2 has a screw threaded portion (not shown) which engages with a correspondingly screw threaded portion (not shown) in the top of an upper cylindrical portion 16 of the body 4 to retain the lid 2 on the body 4. The body has a further cylindrical portion 18, of a smaller diameter than the portion 16, which is connected to the portion 16 via an upper frusto-conical part 20 and a lower frusto-conical part 22 which meet at neck 24 and thus divide the interior of the body 4 into the upper, measuring chamber 8 and the lower chamber 10. The neck 24 therefore constitutes an outlet for the chamber 8.

The upper chamber 8 contains an upper dispersal plate 30 which is situated immediately beneath the inlet 12 and is removably attached to the wall of the measuring chamber 26 via suitable formations (for example bosses) extending in from the chamber wall. The plate 30 is situated immediately above a buoyant member 32 having an upper float portion 34 which leads to a frusto-conical shoulder 36, from the bottom of which a frusto-conical plug (with a smaller degree of taper than the portion 36) 38 depends. As can be seen from figure 2, the plug 38 extends through the neck 24. Since the neck 24 is annular, the plug 38 (being of a circular cross section) is of a complementary shape to the neck 24. The member 32 is open at its top, is hollow and includes a lower aperture 39 (Figs 2 and 3).

The plug 38 carries a pair of downwardly inclined, radial fingers 40 and 42 which act as deflector fins for deflecting a sample of the milk passing through the meter into a receptacle (as described below). The plug 38 also contains a permanent rare earth magnet 41 wholly encapsulated within the plug. The cylindrical portion 18 of the body 4 has a side aperture 44 through which a cylindrical sensor housing 46 extends radially into the lower chamber 28. The housing 46 is sealed to the inner surface of the aperture 44 by, for example, a suitable adhesive and may have . a screw threaded portion (for engaging a corresponding portion on the body, and an elastomeric annular seal). The housing 46 also contains a Hall Probe which provides an output voltage representative of the distance of the probe from the permanent magnet in the plug 38, and hence the vertical position of the buoyant member 32 within the housing 1.

The lower chamber 28 also contains an insert 48 having an upstanding cylindrical wall 50, which is co-axial with the chambers 26 and 28, projecting upwardly from the top of a cylindrical base 52 having a top circular plate 54 formed with a central aperture 56 in registry with the cylindrical portion 50. The cylindrical base 52 includes an aperture for accommodating a multi position valve 58. The valve communicates through an aperture 60 in the plate 54 with the annular receptacle defined by the wall 50, plate 54 and the portion 4 of the body 2.

In figure 1, the body 4 and housing 46 are shown angularly displaced (about the central vertical axis of the meter) by 180° compared with figures 2 and 3. Thus the housing 46 is, in the assembled meter, in a position diametrically opposed to that shown in figure 1.

The operation of the device will now be described.

The inlet 12 of the milk meter is connected to the claw of the milking equipment, whilst the outlet is connected to the rest of the milking system so that, in use, the interior of the housing 1 is subjected to a partial vacuum. In use, a mixture of milk and air flows into the inlet 12 from a milking claw attached to the animal. Air is entrained into the milk flow by means of an air bleed in the claw, and ensures that the milk flows away from the teat cups attached to the claw. However, the air does need to be separated from the milk before the volume of milk can be measured.

Before the flow starts, the measuring chamber 8 is empty, so that the plug 38 seats against, and seals, the circular opening defined by the neck 24 between the chambers 8 and 10.

Because the chamber 8 is initially empty, the buoyant member 32, which acts as a loose plug within the chamber 8, initially seals against the neck 24, thus sealing the annular chamber 8 from the chamber 10. Milk flowing into the inlet 12 first hits the dispersal plate 30 which causes air to be separated from the milk, and then drops towards the bottom of the space between the measuring chamber 8 and the outside of the portion 36. ^' Since the chamber 8 is sealed, the milk will accumulate until the buoyant member 32 begins to float. This will unseat the plug portion 38 from the neck 24, for example, as shown in figure 3, so that there is an annular gap between the plug and neck. Milk can then flow through that gap, whilst the increase in height in the buoyant member 32 is detected and measured by the Hall Probe in the housing 46. If the rate of milk flow into the chamber 8 increases, the buoyant member will rise within the chamber 8 so that the annular gap through which milk can leave the chamber 8 increases in size, thus allowing an increased flow of milk out of the chamber 8.. Air separated from the milk can travel through the aperture 39 in the member 32 to rejoin the main flow of milk below the measuring chamber 8.

The rate of flow is directly related to the height of the buoyant member above its lowest position, i.e. the position in which no milk is flowing, and the output of the Hall Probe therefore provides an indication of milk yield. Because the size of the opening through which the milk leaves the chamber 8 varies roughly in proportion to the flow of milk into the chamber, a wide range of flow rates can be measured. The range of flow rates can be further increased by replacing the buoyancy member 32 with another, similar buoyancy member in which the taper of the fruto-conical plug 38 is different so that a given vertical movement of the buoyant member causes a different change in the area of opening through which milk can exit.

Most milk exiting the chamber 8 flows along the surface of the plug 38 and through the centre of the upstanding cylinder 50 and then out of the housing through the exit 14. Some of the milk, however, is deflected by the projections 40 and 42 into the annular receptacle 62 for collection as a sample representative of the milk produced the animal. In order for this to happen, the valve 58 needs to be closed so that no milk can flow out of the aperture 60. The valve 58 can be moved from the closed position into any of three other positions. In the first position. The aperture 60 communicates with an external air inlet port (not shown), so that the partial vacuum in the housing causes air to be injected into the receptacle 62 to agitate the sample. In the second further position the same inlet port communicates with a short rising tube (not shown) in the receptacle 62, whilst the aperture 60 communicates with an outlet port (not shown). Air is thus admitted into the receptacle 62 at a point above the level of milk therein. This allows milk to drain out and through the outlet, so that a small amount of milk can be drawn from the annular receptacle 62 into a small sample bottle (not shown). The fourth position allows the remainder of the milk in the receptacle 62 to be drained through the outlet 14, via aperture 60. A modified version of meter has a simplified, two position valve instead of the valve 58. The modified valve has just two ports, the aperture 60 and an external port (not shown) which includes a connector for connecting the port to a connecting tube leading to a sealed collection bottle (not shown), so that when connected the bottle and tube are hermetically sealed from the external environment, but can communicate with the interior of the housing when the valve is opened.

When the valve is opened, with the bottle connected, air is initially drawn from the bottle and into the housing until the pressure in the bottle matches that in the housing. If the valve is opened again, when milk has been collected, milk drains from the receptacle 62 into the bottle. If, however, the valve is opened when the bottle is not connected and when milk is in the receptacle 62, air enters the housing through the aperture 60 to achieve the aeration function mentioned above.

Since there is no interruption in the flow of milk through the meter, measurement is a continuous process, and the rate of flow can be checked frequently (possibly many times per second). The apparatus also allows a wide range of flow rates, from in excess of a maximum of 12 litres per minute (relating to dairy cows) to less than one litre per minute (which can be expected from other animals) to be measured, if necessary by selecting a suitably tapered buoyant member.

Since the sample is collected in a receptacle 62 progressively during the course of the operation of the meter it can be truly representative of all the milk collected. Since the sampling facility is inherent in the meter, any elaborate, further apparatus for sampling the milk is not required.

The meter is relatively simple, and can therefore be cheaply produced.

The second embodiment of meter has many features which are similar to those of the first embodiment. In figures 4 and 5, such features are therefore denoted by the reference numerals of figures 1 to 3, raised by one hundred. Thus, the second embodiment of meter comprises an annular housing 101 having a body portion 104 and a base portion 106. The body portion 104 is itself constituted by upper and lower cylindrical portions, respectively referenced 116 and 118 connected by frusto- conical portions 120 and 122 which meet at a neck 124.

In the second embodiment, the lid 102 has a tangential inlet 112 and, instead of a circular planar dispersal plate, the second embodiment has a plate 130 having an upwardly directed central frusto-conical portion 131 rising from a flat annular peripheral portion 133. The plate has a series of apertures, for example aperture 135 through which milk can fall. Since the inlet 112 is tangential, the portion of the chamber 108 above the plate 130 acts as a swirl chamber, which dissipates kinetic energy of milk flowing into the device (before the milk impinges on the float below) and separates entrained air from the milk.

The chamber 108 contains an annular deflector wall 137 which deflects milk dropping from the swirl chamber towards the inner peripheral wall of chamber 108. The wall 137 includes apertures (not shown) through which milk flows towards the buoyant member 132, which is substantially identical in form and function to the buoyant member 32 of the first embodiment. In the second embodiment, however, the magnet 141 is not wholly encapsulated within the plug, but instead is suspended in a protective casing below the member 132 on the bottom of a rod 143 the top of which is attached to the base of the float portion 134. With this arrangement, the stability of the member 134 is improved, and the Hall Probe sensor is in a casing 146 in an externally accessible position at the centre of the underside of the meter.

In order to enable the Hall Probe sensor to be positioned on this part of the meter the milk outlet 114 is offset to one side of the base portion 106.

It will be seen that the annular wall 150 of the sample receptacle 162 is flared from bottom to top. The plug 138 also carries fingers (not shown) having the same nature and function as the fingers 40 and 42 of the first embodiment. The member 132 is hollow, open topped and has a lower aperture (not shown) which performs the same function as the aperture 39. Thus air separated from the milk in the swirl chamber can pass through the member 132 and into the outlet 114 to join the flow of the milk from the meter. The meter also includes a valve (not shown) similar to the valve 58. The top of the lid 102 includes a port 103 for connection to the vacuum source to enable the meter body to be flooded when being washed.

Claims

1. Apparatus for measuring the flow rate of a liquid, the apparatus comprising a measuring chamber having an inlet for receiving liquid and an outlet through which liquid can drain out of the chamber, the apparatus ^• further comprising a float and plug means at least partially situated within the chamber and operable to cause the outlet to be occluded to an extent which decreases with increasing flow of liquid through the inlet, the apparatus being so configured as to enable the height of liquid in the chamber to be measured, thereby to measure liquid flow.

2. Apparatus according to claim 1, in which the plug means and outlet are of complementary shapes so. that, with no liquid in the chamber, the plug means completely occludes the outlet.

3. Apparatus according to claim 1 or claim 2, in which the plug means is tapered from top to bottom.

4 Apparatus according to any of the preceding claims, in which the float and the plug means are incorporated into a single buoyant member.

5. Apparatus according to any of the preceding claims, in which the apparatus includes measuring means operable to measure the distance of at least part of the buoyant member from a reference level, thereby to measure liquid flow.

6. Apparatus according to claim 5, in which the measuring means comprises a magnetic field source carried by the buoyant member and a magnetic field measuring device in a position fixed relative to the chamber.

. Apparatus according to claim 6, in which the field source comprises a permanent magnet.

8. Apparatus according to any of the preceding claims, in which the float is connected to a weight suspended from the float so as to stabilise the float.

9. Apparatus according to claim 8, when appended to claim 7, in which the weight comprises the magnet.

10. Apparatus according to any of the preceding claims, in which the measuring chamber is defined by a housing which also defines a further chamber beneath the measuring chamber outlet, said outlet constituting an inlet to the further chamber, the further chamber also having an outlet and a receptacle for receiving a sample of the liquid through the further chamber.

11. Apparatus according to claim 10, in which the apparatus includes diversion means for diverting a portion of the liquid flowing out of the measuring chamber into the receptacle, whilst allowing the rest of the liquid to reach the outlet of the further chamber.

12. Apparatus according to claim 11, in which diversion means comprises one or more formations, such as fins, on the plug means.

13. Apparatus according to any of the preceding claims, in which the buoyant member is one of a plurality of such members, the members being interchangeable so that any one member can be situated in the measuring chamber, and having different shapes, thereby to enable the sensitivity of the apparatus to be altered by changing the buoyant member.

14. Apparatus according to any of the preceding claims, in which apparatus includes a deflector plate between the inlet of the measuring chamber and the float, the deflector plate being arranged to separate entrained gas from the flow of liquid into the measuring chamber.

15. Apparatus according to any of the preceding claims, in which the milk inlet is tangential to the measuring chamber so as to create a rotational flow of milk entering meter thereby to reduce the kinetic energy of the milk before it impinges on the float.

16. Apparatus according to any of the preceding claims, in which the apparatus is a milk meter for measuring the yield of milk from an animal.

17. Apparatus according to any of the preceding claims, in which the apparatus includes a bypass passage for enabling air separated from the liquid entering the apparatus to bypass liquid accumulated in measuring chamber and rejoin the liquid flowing through the outlet.

18. Apparatus according to claim 17, when appended to claim 4, in which the buoyant member is hollow and has upper and lower openings, thereby defining said passage.