GB2124877A - Monitoring milking - Google Patents

Abstract

Apparatus for use in monitoring milk flow comprises a set of teet cups (11-14), each connected to a manifold (15). The manifold is connected by conveying means (17) with a reservoir (18 for receiving milk. A pair of electrodes (28, 29) are disposed in an initial portion (19) of the flow path in the conveying means. A monitoring device (32) comprises means for applying an alternating voltage to the electrodes and for providing an electrical output signal representing the conductance of the circuit which includes the electrodes and the part of the milk flow path which lies therebetween. The output signal provides a measure of the rate of milk flow along the flow path. The device (32) can provide a signal for removing the teets. <IMAGE>

Description

SPECIFICATION Method of monitoring milking and apparatus for use in the method This invention relates to a method of milking animals, primarily cows.

It is desirable to monitortheprocessofmilking a cow by machine, in orderto record or respond to changes inthe rate of milkflowfrom the cowor other parameters and also to record or respond to the value ofparametersata particulartime. Forexample, itis known to include in apparatus for milking cows devices which respond to the absence of substantial flow of milk from the cow by terminating the milking process and removing the teat cups from the teats of the cow. Known arrangements which respond to the absence of substantial flow of milkfrom the cow are unsatisfactory for a variety of reasons.One of these reasons isthattheflowofmilkthrough a position at which the presence of milk is sensed is erratic and not closely related to the flow of milk from the teats of the cow. These arrangements do not provide accurate information as to the flow from the teats.

According to a first aspect of the invention,there is provided a method of monitoring milking wherein milkdischargedfrom a teat and air pass together along an initial portion and then a subsequent portion of a flow path, the milk and air in the subsequent portion ofthe flow path travelling upwardly, and wherein there is provided an output signal which is dependent on a physical property of the contents of said initial portion of the path.

Slugs of milk, each slug occupying the entire cross-sectional area ofthe path, are carried by the air up the subsequent portion ofthe path. The length of the slugs and the spacing between successive slugs varies in an unpredictable manner; whereas in the initial portion ofthe path the milk does not occupythe entire cross-sectional area ofthe path and the air present in the initial portion ofthe path lies above the milk. The respective proportions ofthe cross-section area of the initial portion oftheflow path ata selected position are related in a reproducable mannerto the rate of flow of milk along the initial portion ofthe flow path.

The physical property is preferably one which depends on the proportions of the initial portion ofthe flow path which are occupied by milk and air respectively. The property is preferably an electrical property.

In the preferred method, during a major part ofthe period forwhich a cow is milked, milkflowsfreely from the teats of the cow along the path and the amplitude of the output signal oscillates about a mean value with a frequency at which the teats are subjected to a cyclic pressure variation to induce flow of milk from theteats. When the amplitude of the oscillations ofthe output signal falls to a relatively low value, the mean value of the output signal is monitored and when the mean value then falls to a predetermined threshold, milking is terminated by allowing the pressure in the teat cups to rise to the ambient pressure and removing the teat cups from the cow.

According to a second aspect ofthe invention, there is provided apparatus for milking and comprising a manifold having an air inlet orifice, a set of teat cups connected with the manifold, a reservoir for storing milk, conveying means defining a flow path from the manifold to the reservoir and means for reducing the pressure in said reservoir to cause milktoflowfrom theteatcupsthroughthe manifold to the reservoir, wherein an initial portion of said path is more level than is a subsequent portion ofthe path and there is provided a plurality of spaced electrodes which present respective surfaces to the initial portion of the path,the electrodes being connected in an electric circuitwith meansforapplying an alternating voltage to the electrodes and responding to variations in the conductance ofthe circuit to provide an output signal.

The electrodes preferably include a pair of electrodes spaced apart along the flow path.

There is also provided in accordance with the invention, for use in the method of the first aspect or in apparatus according to the second aspect, a tube of transparent, electrically insulating material having at opposite ends means for connecting the tube in a fluid flow line, having between its end portions a pair of tubular electrodes which are spaced apart along the tube and are embraced bythetube and having respective electrical conductors extending through a wall of the tube from the electrodes.

An example of a method and of apparatus embodying the invention will now be described, with reference to the accompanying drawings, wherein: FIGURE 1 shows the apparatus diagrammatically; and FIGURE 2 represents an output signal of the apparatus.

The apparatus comprises a cluster 10 of known form comprising fourteatcups 11 to 14, each connected by a pair of flexible tubes to a manifold 15. At the underside of the manifold, there is provided a valve which can be opened to admit airfreelyto the manifold and which normally defines a relatively small orifice through which air can enter the manifold.

The manifold is connected by conveying means 17 with a reservoir 18 fo r receivi ng milk. This reservoir may be common to a number of clusters and may be remote.

The flow path defined by the conveying means 17 includes an initial portion 19 adjacentto the manifold 15 and a subsequent portion 20 which extends upwardly from the initial portion to a level above the teat cups 11 to 14. Generally, the subsequent portion 20 will extend to a level approximatelytwo metres above the surface on which the cow being milked stands and, towards its upper end, the subsequent portion 20will be substantially vertical. In contrast with this, the initial portion 19 is relatively level.

Usually, the initial portion will slope downwardly from the manifold 1 towards the portion 20 but the initial portion may be substantially horizontal.

When the apparatus is in use, the teat cups 11 to 14 receive and act on the teats of the cow in the usual manner and air is drawn from the reservoir 18 bya pump 21 to maintain the pressure in the reservoir substantially below the ambient pressure. Milkwhich is discharged from the teats drains down to the manifold 15 and then along the initial portion 19 of the path defined by the conveying means. Air enters the manifold through the air bleed orifice and also passes along the initial portion 19 ofthe path, where the air occupies an upper part ofthe path and the milk occupies a lower part.

The respective proportions of the cross-sectional area ofthe path occupied by the milk and airwill vary along the initial portion 19 ofthe path and, atany selected position along the path, will depend upon a number offactors, including the geometry ofthe path, the rate at which air is admitted to the manifold and the rate at which milk is discharged from the teats of the cow. lntermittently,the milk occupies the entire cross-sectional area of the path at least at a position where the initial portion 19 merges with the subse quentportion 20 of the path . A slug of milk occupying the entire cross-sectional area ofthe path which is formed in this way is acted upon by the pressure within the initial portion 19 ofthe path orwithin the manifold 15.This pressure exceeds that in the reservoir 18 sothatthe slug of milk is driven up the portion 20 ofthe pathtothe reservoir. Airflowsfrom the manifold through the initial portion 19 and up the portion 20 ofthe path behind the slug of milk until furthermilkaccumulates in the initial portion 19to occupy the entire cross-sectional area once more and form a second slug.

There is associated with the initial portion 19 of the flowpath meansfor providing an outputsignal which is dependent on a physical property of the contents of the portion 19. The physical property is one which is differentfor milk and air, so thatthevalue ofthe output signal will depend upon the respective proportions of the initial portion 19 occupied by milk and by air. The property is preferably an electrical property and, in the example illustrated, is conductance.

The initial portion 19 oftheflow path is defined, in part, by a tube 22 formed of a transparent plastics material. There protrude from opposite end portions ofthis tube connectors 23 and 24for connecting the tube respectively with the manifold 15 via a short length 25 offlexible tube and with a long flexible tube 27 which definesthe subsequent portion 20 oftheflow path. The connectors 23 and 24may be formed of metal,for example stainless steel.

There is disposed within the tube 22 between the connectors 23 and 24 a pair of electrodes 28 and 29 which are spaced apart so that a part ofthe initial portion 1 9 of the flow path extends between them. In the particular example illustrated, each ofthe electrodes is oftubularform, defines the circumferential boundary of a part ofthe flow path and is tightly embraced bythetube 22. The electrodes are spaced apart along the flow path, typically by a distance of at least 1 Omm. Particularly in a case where the connectors 23 and 24 are formed of electrically conductive material, the electrodes 28 and 29 are spaced along the flow path from the connectors. The material of which the tube 22 is formed is an electrical insulator and is rigid, relative to the tube 27.

At least the electrode 28 which is nearer to the manifold 15 has a length which is at leasttwice the internal diameter of the electrodes. This diameter is typically 15mm. This electrode can be the connector 23. Electrically conductive leads 30 and 31 extend from the electrodes 28 and 29 respectivelythrough the wall of the tube 22 to an electronic monitoring device 32 which may be mounted remotelyfromthetube22.A suitable electrically conductive material from which the electrodes may be formed is stainless steel. If required, a larger number of electrodes may be provided and these may be spaced apart along the flow path or at least some electrodes may be spaced aparttransversely ofthe flow path.

The monitoring device 32 comprises means for applying to the electrodes 28 and 29 an alternating voltage, typically having a peak value of three volts, and for providing an electrical output signal represent ing the conductance of the circuit which includes the electrodes 28 and 29 and the part ofthe milkflow path which lies between them. The electrode 28 is maintained at or close to earth potential.

Atypical example ofthe electrical output signal during milking of a cow is represented in Figure 2. The teats of the cow are subjected to a cyclic pressure variation at a frequency which is typically one cycle per second. Usually, the flow of milk varies cyclically at the same frequency so that the depth of the layer of milk in the tube 22 increases and decreases with the samefrequencyandthevalueoftheoutputsignal varies in a corresponding manner. It can be seen in Figure 2 that, during the major part ofthe period which is represented the output signal oscillates about a mean value with a frequency in the region of one cycle per second. When the discharge of milkfrom the teats ceases or almost ceases, the amplitude ofthe oscillations of the output signal falls to a relatively small value.However, the mean value of the output signal does not fall immediately to a level indicating absence of milk from the flow path because a significant period elapses before all milk has drained from the tubes and manifold and has been carried to the reservoir 18.

Itwill be appreciated that, particularly when the rate offlow of milk is low, milkwill tend to drain down the portion 20 oftheflowpath alongthewallsofthetube 22 without occupying the entire cross-sectional area ofthattube so thattheflow of airfrom the manifold 15 to the reservoir will not be very effective in transferring milkto the reservoir and a significant depth of milk may remain in the tube 22 after all flowfrom the teats ofthe cow has ceased.

The monitoring device 32 is adapted to respond to a significant fall in the amplitude ofthe oscillations of the output signal by commencing to monitorthe mean value of the output signal. If, when the amplitude of the oscillationsfalls substantially, the mean value commencestofall andcontinuestofalltoa predetermined threshold value,the monitoring device 32 provides a signal which initiates removal of the teat cups 11 to 14 mechanically from the teats of the cow by known equipment (not illustrated).

The monitoring device 32 is also adapted to respond in a different way, for example by providing visual or audible warning signal, to other changes in the output signal. Examples of such other changes include significant fall in the amplitude of the oscillations aboutthe mean value without the mean value then falling to the threshold value, a substantial change in the frequency of the oscillations about the mean value and a substantial change in the mean value without substantial change in the oscillations about the mean value.

The monitoring device 32 may be adapted to delay by a predetermined period, for example 25 seconds, response to a change in the output signal, in orderthat a change which is reversed within a shorter period will not cause the monitoring device to respond. The monitoring device would normally be set in operation bythe herdsman. For example, when automatic apparatus for removing the teat cups 11 to 14 is used, the herdsman operates an electrical switch to instruct that apparatus to release the teat cups in order that he can apply them to the cow. A signal from that switch may be passed to the monitoring device 32 to set the device in operation, after a predetermined delay, for example of 120 seconds.

Claims (12)

1. A method of monitoring milking wherein milk discharged from a teat and air pass together along an initial portion and then a subsequent portion of a flow path, the milk and air in the subsequent portion of the flow path travelling upwardly, and wherein there is provided an outputsignalwhich is dependent on a physical property ofthe contents of said initial portion of the path.

2. A method according to Claim 1 wherein the physical property depends on the proportions ofthe initial portion ofthe flow path which are occupied by the milk and air respectively.

3. A method according to Claim 2 wherein said physical property is an electrical property.

4. A method according to any preceding claim wherein milk discharged from a plurality of teats passes concurrently along the initial and subsequent portions of said path.

5. A method according to any preceding claim wherein, when the milkflows freely from the teat or teats along said path, the amplitude of the output signal oscillates about a mean value at a frequency at which the teat orteats are subjected to a cyclic pressure variation,when the amplitude ofthe oscillations of the output signal falls to a relatively low value, the mean value oftheoutputsignal is monitored and when the mean value then falls to a predetermined threshotd, milking is terminated.

6. Apparatus comprising a manifold having an air inlet orifice, a set of teat cups connected with the manifold, a reservoir for storing milk, conveying means defining a flow path from the manifold to the reservoir and means for reducing the pressure in said reservoirto cause milk to flow along the path from the manifold to the reservoir, wherein an initial portion of said path is more level than is a subsequent portion of the path and there is provided a plurality of spaced electrodes which present respective surfaces to the initial portion of the path,the electrodes being connected in an electriccircuitwith means for applying an alternating voltage to the electrodes and responding to variations intheconductanceofthe circuitto provide an output signal.

7. Apparatus according to Claim 6 wherein the electrodes include a pair of electrodes spaced apart along the flow path.

8. Apparatus according to Claim 7 wherein that one of said pair of electrodes which is nearer to the manifold is a tube having a length of at leasttwice its internal diameter.

9. Apparatus according to any one of Claims 6 to 8 wherein the part ofthe conveying means which defines a space between the electrodes is transparent.

10. For use in apparatus according to any one of Claims 6 to 9 or in a method according to any one of Claims 1 to 5, a tube of transparent electrically insulating material having at opposite ends meansfor connecting the tube in a flow line, having between opposite end portions a pair oftubular electrodes which are spaced apart along the tube and are embraced by the tube and the tube having respective electrical conductors extending through a wall ofthe tube from the electrodes.

11. Apparatus substantially as herein described with reference to and as illustrated in Figure 1 of the accompanying drawings.

12. Any novel feature or novel combination of features disclosed herein or in the accompanying drawings.