EP1444486A1

EP1444486A1 - Method and device for determining the volumetric flow rate of milk flowing during a milking process

Info

Publication number: EP1444486A1
Application number: EP02791687A
Authority: EP
Inventors: Heiner Wamhof; Marek Krasutzki; Peter Kaever; Jan-Hermann Reurik
Original assignee: WestfaliaSurge GmbH
Current assignee: GEA Farm Technologies GmbH
Priority date: 2001-11-16
Filing date: 2002-11-18
Publication date: 2004-08-11
Also published as: WO2003042637A1; US20050034518A1; US7155971B2

Abstract

The invention relates to a method and device for determining the volumetric flow rate of milk flowing during a milking process. A cross-sectional area (Ai) of the milk flow (2) is determined at a first measuring point (3) by means of a sensor (4) which is arranged outside the flowing milk. The time (ti) required by the milk flow (2) with the determined cross-sectional area (Ai), to go from the first measuring point (3) to a second measuring point (5) which is provided downstream from the first measuring point, is measured. The flow speed (vi) is derived from the measured time (ti) and the known distance (s) between the first and second measuring points (3, 5). The volumetric flow rate (V(t)) is determined on the basis of the determined cross-sectional area (Ai) and the flow speed (vi).

Description

Method and device for determining a volume flow of milk flowing during a milking process

The subject matter of the invention relates to a method and to a device for determining a volume flow of milk flowing during a milking process.

Milking an animal, especially a cow, is a complex process. The duration of a milking process is individual for each animal. The time span within which milking is carried out can also fluctuate greatly in individual animals, since this also depends on the lactation level of the animal. It has been found that the milk flow represents a relevant parameter that can be used to trigger further process sequences or to control and regulate facilities within a dairy farm. Switch-off, post-milking and / or other devices are used during the milking process in order to make the milking process economical and animal-friendly on the one hand. A prerequisite for this is the most accurate knowledge of the actual, preferably current, milk flow.

With the increasing technicalization of dairy farming, there is also an increased interest in determining the individual milk quantities and the quantity of milk released by a herd. Knowing the amount of milk dispensed during individual milking processes or over certain periods enables improved animal husbandry and herd management. A fundamental problem in determining the volume flow or the mass flow of milk is essentially to be seen in the fact that the volume or mass flow to be measured pulsates, so that there is no uniform flow. The milk is not present as a homogeneous phase during the milking process, but as a multi-phase. It consists of a liquid phase and a foam phase, whereby the foam phase in itself can be of different consistency.

Different concepts have been developed for determining the volume or the mass of the milked milk. The determination of the mass of milked milk by volume measurement is of particular importance. The devices provided for this purpose have a measuring chamber, in which either the mass of the content is determined by means of tilting scales or the volume is determined by means of a float or sensor electrodes. Devices in which the milk flow is divided into small portions, the volume or mass of which is determined, keep the inflow to the measuring chamber open at all times, and a valve only controls the emptying.

Furthermore, devices are known by means of which the mass of the milk is to be determined in free flow. These devices use ultrasound or infrared sensors and greatly narrow the cross-section of the line and / or segment the milk flow several times. A partial flow can be branched off for measurement. Then the problem of proportional separation of a partial flow occurs with high accuracy, because the accuracy of the flow determination depends on the accuracy of the separation of the partial flow. Previously available measuring devices based on a conductance measurement have a low accuracy. There are also devices that determine the fluid flow by binary evaluation of the sensor signal. The accuracy of the devices that work according to the second method depends on external parameters such as attachment, dynamics of the milk flow, pressure and other parameters. Devices that work in the flow and in which the cross-section of the line is narrowed or the milk flow is segmented several times, result in an increased susceptibility to contamination and poorer cleaning options. The current meter described, for example, in US Pat. No. 5,083,459 does carry out a contact resistance measurement, but works with a measuring chamber in which the milk jams, so that cleaning the device is complex.

The problem with determining the mass of the milk is that milk is a highly foaming fluid, so that there is a relatively high measurement uncertainty with regard to the mass of the foaming milk. This problem is known and is described in EP 0 315 201 A2.

To solve this problem, it is proposed according to EP 0 315 201 A2 that the entire profile of the foaming liquid is determined, taking into account that the specific density of the liquid-air mixture changes depending on the height. In order to measure the specific density of the foaming liquid at the different height levels, a reference value is measured on a reference measuring section containing essentially degassed liquid. Depending on whether a corresponding measured value measured in air is greater or smaller than the reference value obtained on this reference measuring section, a ratio number is formed for each altitude level in accordance with the ratio of the reference value and the measured value at this altitude level or the reciprocal of the ratio. Possibly. In accordance with a predefined calibration, a corrected ratio number can be formed which is one for degassed liquids and essentially zero for air. Each ratio is multiplied by the specific gravity of the degassed liquid. The result of this multiplication provides the specific density of the foaming liquid. To determine the mass of a With the liquid, the volumes of the individual phases are determined, and these volumes are multiplied by the specific density of the foaming liquid.

The problem of determining the volume flow has also been described in DE 41 10 146 AI. According to this document, a method for measuring the milk flow during the intermittent removal of the milked milk in the form of milk plugs is described via at least one riser section. Here, a value corresponding to a mass of each milk stopper is determined taking into account a predetermined stopper speed by scanning the length of time of each milk stopper inside the riser section at a distance from the inner wall of the riser. From this, an average milk flow value is formed by averaging successive milk plugs over time. The prerequisite for this procedure is that the milk is transported in the form of milk plugs in the riser.

The milk does not flow in the form of a continuum during the milking process, but in the form of milk plugs. From DE 41 10 146 AI a method for measuring the milk flow is known, in which the removal in the form of milk plugs takes place intermittently. The milked milk is transported away via at least one riser section. For this purpose, it is proposed that a value corresponding to the mass of each milk stopper be determined by scanning the length of each milk stopper in the interior of the riser section at a distance from the inner wall of the riser pipe, and an average milk flow value is formed therefrom by averaging over successive milk stoppers. This Veifalirensführung is based on the consideration that, by suitable measurement of the milk plug, a statement about the mass contained in a milk plug and from this a statement about the Milk flow can be obtained. The assumption here is that a milk plug as such is homogeneous.

In today's milking parlors with a lower milk line and a lower vacuum level, it is not always ensured that the milk is transported using milk plugs. This is necessary for the functioning of the method described in DE 41 10 146 AI. Riser sections in milking plants are disadvantageous due to the higher vacuum loss and with regard to a remaining amount of milk. In addition, milk is a food, so certain minimum hygienic requirements must be met. This requires that the components of the milking system can be cleaned safely and reliably. In the device for measuring a value corresponding to the mass of a milk plug during the intermediate removal of the milk, in the form of milk plugs, sensors are provided according to DE 41 10 146 AI in the riser and at a distance from the inner wall thereof. These can lead to increased susceptibility to contamination. Cleaning is therefore not without problems. In addition, the cross-section of the riser pipe is changed by these sensors.

Proceeding from this, the present invention is based on the objective of specifying a method and a device by means of which a determination of the volume flow independent of the mode of transport of the milk is made possible.

This object is achieved according to the invention by a method with the features of claim 1 or by a device with the features of claim 13. Advantageous further developments and refinements are the subject of the respective subclaims. The method according to the invention for determining a volume flow of the milk flowing during a milking process is characterized in that a cross-sectional area of the flow cross-section of the milk flow or a parameter proportional to the cross-sectional area is determined at a first measuring point. This provides information about the cross-sectional area occupied by the milk flow in the line. The cross-sectional area is the area that is essentially perpendicular to the outflow direction. In a further step, the time or a characteristic measure of the time that the milk flow with the determined cross-sectional area requires in order to get from the first measuring point to a second measuring point located downstream of the first measuring point is determined. The distance between the first and the second measuring point is known, so that the current flow rate can be determined from this. The volume flow is determined on the basis of the determined cross-sectional area under flow velocity.

The device will preferably be designed in such a way that the cleaning of the milk-carrying components of the milking system is not influenced or is influenced only to a small extent. The volume flow in a line with a predetermined geometry is preferably determined.

The basic procedure of the method according to the invention makes it possible to determine the volume flow in the milk line without it being important that the shape of the milk transport, for example in the form of a plug, be known. The process can also be carried out in today's milking parlors with a lower milk line and a low vacuum level.

The determination of the flow velocity of the milk flow can be done by modeling the flow dynamics of the milk flow, for example by a Differential equation can be refined. In particular, flow laws and a special design of the milk route can include the determination of the flow rate. These can also be used to determine the cross-sectional area in order to introduce the dependence of the cross-sectional area on the milk flow at the measuring point into the measuring equation. The milk route can in particular be designed so that a determination of the speed is particularly favorable.

Knowing the volume flow as a function of time, according to a further proposal, a total volume flow is determined by integrating the volume flow over time.

A parameter proportional to the cross-sectional area can be formed by forming the relationship between the cross-sectional area and a free flow cross-section of the line. The parameter can have two extreme values, namely 0 and 1. If the parameter is zero, no milk flow flows in the milk line. If the parameter corresponds to the value 1 or if this value is close to 1, there is complete or almost complete filling of the line by the milk flow. In the case of such an almost completely filled line, the speed can be interpolated in order to obtain an average speed of the milk flow under these conditions. The interpolation preferably extends from the beginning of the milk section of the almost completely filled line to the end thereof. This means that a value for the speed can also be specified for so-called milk plugs.

The determination of the time it takes a slice of the milk flow to flow from one measuring point to another measuring point is an essential parameter for determining the milk flow. The method proposed here is to obtain this information from a combination of the measured values at the two measuring points.

To further improve the determination of the flow velocity, it is proposed that at least one further measuring point be provided downstream of the second measuring point. By using a larger number of measuring points, the speed can also be determined with the aid of an estimator based on weighted least squares, in particular with knowledge of the underlying flow conditions. The evaluation of the sensor data by means of Cayman filtering is done in post-processing. All data and observations flow simultaneously into a Cayman filter for an optimal estimate of the state of the system. The Cayman filter, as a recursive least-squares estimation algorithm, takes into account a priori knowledge of the dynamic behavior of the milk flow or the milking system. In addition to observation equations, the Cayman filter therefore also uses system equations that describe the dynamic behavior of the system. A new state vector is predicted from the initial state or previous state. The predicted state vector is then corrected using the observations made at one point in time. This correction is evaluated using a matrix which results from the covariance matrices of system and measurement noise. The matrix determines whether the state vector should be estimated primarily from the prediction or from the observations.

If the method is implemented with less powerful processors, the speed can also be determined by forming correlations over the time series of the various sensor signals. In a special, still further simplifying embodiment, the extraction of certain features in the signal stream of the sensors is provided. The speed results in simply from a temporal assignment of the characteristics of the sensory signal currents. For example, particularly high or particularly low sensory values can be used as characteristics, in particular in combination with high positive or negative changes over time in these values.

In order not to influence the flow through sensors and to achieve the simplest possible cleaning through the line and other components of a milking system, a contactless measurement is proposed. It is preferred to carry out the method with sensors which determine the conductivity of the milk. In particular, it is proposed that the conductivity of the milk be measured at at least one measuring point by means of a ring electrode. Stick electrodes are another preferred embodiment. Alternatively or additionally, the milk flow can be optically recorded.

The determination of the speed of the milk flow can also be determined on the basis of the verification of random local inhomogeneities which move with the speed of the milk flow. The inhomogeneities can be, for example, gas bubbles that are enclosed in the milk flow.

If several measuring points are provided, switching between different measuring points can be advantageous to increase the accuracy of the speed determination. In the case of closely located measuring points, filtering can be carried out over several measuring points in order to improve the signal noise behavior for the cross-section of the line covered with milk. In order to simplify the milk flow sampling, the cross section of the path that the milk takes is largely kept constructively constant. The device according to the invention for determining a volume flow during a milking process of milk flowing in a line with a predetermined geometry is characterized in that a first measuring point with at least one sensor arranged outside the flowing milk and a second measuring point arranged downstream with at least one outside the flowing one Milk arranged sensor are provided. The signals generated by the sensors are evaluated in an evaluation unit. This configuration of the device does not change the flow cross-section of the line, so that there is the risk of contamination of the component projecting into the flow cross-section.

As an alternative to this, the milk line can be shaped in such a way that the milk flow is shaped in a manner that particularly favors scanning by electrodes. In particular, the utilization of the centrifugal acceleration by cyclones or cyclone-like milk line sections or correspondingly curved sections of the milk line is contemplated. Changing the cross-sectional shape to cross-sections that are no longer nearly round can also improve the execution of the measurement. In particular, cross-sections are contemplated which are elliptical, rectangular, approximately triangular or shaped as a parabolic section.

An embodiment of the device is preferred in which at least one further measuring point with at least one sensor is provided downstream of the second measuring point. The device is preferably designed such that each sensor can be switched against each other in order to achieve a maximum yield of measured values.

An embodiment of a device is preferred in which at least one sensor is a conductivity sensor. In particular, it is proposed that the sensor in Form of a ring electrode is formed. The line between two conductivity sensors is preferably formed from an electrically insulating material, so that the conductivity of the line has no influence on the results of the measurement.

Alternatively or additionally, at least one sensor can be provided, which is a capacitive or inductive sensor. The sensors can also be photo detectors.

According to yet another advantageous embodiment of the device, it is proposed that the evaluation unit has at least one Cayman filter.

The inventive design of the device ensures that the volume flow of milk is determined by means of inexpensive sensors. By evaluating at least two measuring points, the flow of milk, which can fluctuate due to different pressure conditions in the milking installation and from milking stall to milking stall, is significantly more robust. This applies particularly to higher milk flows.

In a preferred development of the method according to the invention for determining a volume flow of milk flowing during a milking process, a characteristic variable characteristic of the capacity of the flowing milk is determined at essentially every sampling time. A value for the capacity can be derived from this. The characteristic parameter can characterize a capacity of the flowing milk or a parameter proportional to the capacity within a predetermined measurement volume. The characteristic parameter or the capacity of the milk or a parameter proportional to the capacity is used to determine the actual milk volume within the measuring volume using known capacities or known parameters compared. Furthermore, the speed of the milk flow is determined and the volume flow of the milk is determined from these data.

The characteristic capacity parameter is a parameter that is characteristic of the capacity of the milk in the measurement volume. The capacity of the milk in the measurement volume can be derived from the characteristic capacity parameter. The characteristic capacity parameter can, for example, be proportional to the capacity. A quadratic, logarithmic, exponential, empirically determined or other connection is also possible.

According to a development, it is proposed that a characteristic capacity parameter of the flowing milk or a parameter proportional to the capacity within a predetermined measurement volume is determined at each sampling time. The characteristic capacity parameter or a parameter proportional to the capacity is compared with previously known parameters in order to determine the milk mass actually located within the measuring volume. The speed of the milk flow is also determined. The mass flow of milk is determined from the data obtained in this way.

By determining the characteristic capacity parameter of the milk, it is avoided that conductive connections to the milk are formed, as is the case with the known methods, which work according to the transition resistance principle. The capacity is determined without contact.

An actual milk volume or the milk mass within the measurement volume is determined by comparing the derived capacity parameter capacity with already known capacities or capacity parameters. Possible changes in the dielectric constant of the milk are taken into account. The proposed procedure also has the advantage that a determination of the volume flow or mass flow is achieved, although the milk is not only a pure liquid phase, but also a mixture of a liquid phase and at least one foam phase. The foam phase, or the proportion of the foam phase, finds its way into the dielectric constant of the milk and thus into the capacity of the milk. The determination of the relationships between the milk volume or the mass of the milk and the capacity which is to be provided for comparison purposes is preferably carried out empirically. If there is a sufficiently large amount of data, a mathematical description of the relationship between the capacity and the consistency of the milk with the volume or the mass of the milk can be made.

The capacity of the flowing milk is preferably measured at specified time intervals. From this, the temporal change in the volume flow or the mass flow and the course of the volume flow and the mass flow during the milking process can be determined. The measured frequency can also be used to control the measurement frequency, e.g. in the case of high milk flows is measured at a higher frequency. This data can also serve as control and / or regulating variables for further devices or process sequences. If the mass flow falls below a certain level, the post-milking process and further a milking process can be started.

Preferably, more scans of a milking process are carried out if these are used to determine a total volume flow or a total mass flow. This data is of particular interest for macroscopic observation of the herd. The speed is preferably determined optically. For this purpose, for example, transmitting and receiving elements which are arranged at a distance from one another are provided.

According to a further advantageous embodiment of the method, it is proposed that the capacitance be determined at at least two spaced-apart locations and that the time offset of the signals associated with the capacitances is used to determine the speed. The characteristic capacity parameter is then derived from these measurements.

If the capacitance is measured at at least two spaced-apart locations, it is proposed according to yet another advantageous embodiment of the method that the capacitance takes place at at least two different frequencies. As an alternative to the frequencies or additionally, the capacitance can be determined at at least two different temperatures. This procedure has the advantage that an even greater measurement certainty is achieved. This is particularly the case when determining the capacitance at at least two different temperatures, since this allows the influence of the temperature on the capacitance to be taken into account and compensated for.

According to a further inventive idea, a device for determining a mass flow of milk flowing during a milking process is proposed. The device has a measuring device for determining a characteristic capacitance parameter. A device for determining the speed of the milk is also provided. The data supplied by the measuring devices are evaluated by an evaluation unit with regard to relevant quantities with previously known data. The device has a control unit, which is connected to the evaluation unit and the measuring device. gen connected, wherein the control unit controls the measuring device at predetermined time intervals, so that a sequential determination of the capacity and the speed is carried out.

The capacitance is preferably determined by means of plates arranged at a distance from one another, which are preferably a component of the measuring device. The arrangement and shape of the plates can also be carried out in other ways. This is to be optimized experimentally. It is also conceivable here to have opposing metal surfaces around a circular cross section.

The plates are preferably arranged in the milk flow path in such a way that the milk can at least partially be washed around them. However, the plates can be provided electrically insulated from the milk. The plates are preferably arranged parallel to one another.

According to yet another advantageous embodiment of the device, it is proposed that it have two measuring devices arranged one behind the other in the direction of flow of the milk for determining the characteristic capacity parameter, which are connected to a correlation unit. The correlation unit will also determine the speed of the flowing milk.

The two measuring devices arranged one behind the other are preferably operated at different frequencies or different temperatures.

Further advantages and details of the method according to the invention and the device according to the invention are explained with reference to the exemplary embodiments shown in the drawing, without the subject matter of the invention being restricted to these exemplary embodiments. Show it:

1 schematically shows a first exemplary embodiment of the device according to the invention,

Fig. 2 shows schematically a second embodiment of the device for

Determination of a volume flow of a flowing milk and

Fig. 3 shows schematically a process flow.

Fig. 4 shows a third embodiment of the measuring devices for determining a capacitance and the speed

5 schematically shows the circuit diagram of the measuring devices for determining a capacitance and the speed

6 shows a fourth exemplary embodiment of a device for determining a volume or mass flow,

Fig. 7 schematically shows a device for determining a volume or mass flow of a flowing during a milking process

milk

8 shows schematically in a diagram the course of the mass flow over time,

Fig. 9 schematically shows the course of the change in voltage over time 10 shows the course of the voltage of the measuring device for determining the speed of the milk

FIG. 1 schematically shows a first exemplary embodiment of a device for determining a volume flow of a milk 2 flowing into a line 1 with a predetermined geometry during a milking process.

The device has a first measuring point 3. This measuring point 3 contains at least one sensor 4 arranged outside the flowing milk. In the exemplary embodiment shown, the sensor 4 is formed by a ring electrode which is arranged on the outer jacket of the line 1.

A second measuring point 5 is provided downstream of the first measuring point 3 at a distance s. The second measuring point 6 also has a sensor 6, which is designed in the form of a ring electrode. The ring electrode is arranged on the outer jacket of line 1. The signal line 7 connects the sensor 4 to the evaluation unit 8. This unit is also coupled via signal line 9 to the sensor 6 of the second measuring point 5. To output the determined data in the evaluation unit 8, an output device 10 is provided, which is connected to the evaluation unit 8 via a connecting line 11. The evaluation unit 8 can comprise a computer.

Figure 2 shows a second embodiment of a device. The basic structure of the device according to FIG. 1 corresponds to the device according to FIG. 1, with a further measuring point 12 with a sensor 13 being provided downstream of the second measuring point 5. The sensor 13 is connected to the evaluation unit 8 via a signal line 14. The sensors are designed so that they can be switched against each other in order to achieve a maximum yield of measured values. The sensor 6, which is designed in the form of a ring electrode, can be used as a common electrode and the gaps between measuring points 1, 2 and 2, 3 represent the sampling points.

FIG. 3 schematically shows the process sequence for determining a volume flow of milk flowing in a line with a predetermined geometry during a milking process.

The line in which the milk flows is shown schematically. Several sensors are coupled to the line, which detect the milk flow in the line. The signals from the individual sensors are subjected to filtering and possibly amplification.

Corresponding sensor values are generated from the signals, which are used to determine the cross-sectional area A (t). The cross-sectional area A (t) represents the flow cross-section of the milk flow in the line.

In addition to the sensor values from which the cross-sectional area of the flow cross-section of the milk are determined, a time offset determination is carried out, so that the speed of the milk flow in the line can be determined from these values.

Knowing the cross-sectional area and the flow velocity of the milk can determine the volume flow. By integrating the volume flow over time, the amount of milk or the total volume of milk flowing in a predetermined time interval can be determined.

FIG. 4 schematically shows a third exemplary embodiment of the measuring devices for determining the capacity and the speed of a flowing milk. The measuring devices are connected to a capacitor 101 through which milk flows. The direction of flow of the milk is indicated by arrow 102.

A measuring device is provided for determining a capacity of the flowing milk or a parameter proportional to the capacity. For this purpose, the measuring device 106 has two capacitor plates 103, 104 arranged at a distance from one another. The plates 103, 104 are arranged parallel to one another. They each have a height h. The free flow cross section between the plates 103, 104 is designated by the reference number 105.

Behind the measuring device for determining the capacity of the flowing milk, the measuring device 107 for determining the speed of the milk is viewed in the flow direction of the milk. The device 107 comprises two optical transmission and reception elements 108, 109 which are arranged at a distance from one another. In the exemplary embodiment shown, the transmission and reception elements 108, 109 are arranged at a distance x from one another. The optical transmitting and receiving elements can be light barriers (e.g. infrared).

FIG. 5 schematically shows a circuit diagram of the measuring devices according to FIG. 4. The measuring device 106 for determining the capacitance has the capacitor plates 103, 104. Each capacitor plate 103, 104 is connected to a measuring amplifier 112 via a signal line 110, 111. The signal 113 of the measuring amplifier supplies the course of the voltage of the capacitor as a function of the volume flow of the milk.

The measuring device 107 for determining the speed of the milk has a first and a second pair of optical transmission and reception elements 108, 109 on. The optical transmission elements 108 are each connected to an amplifier 116 via two lines 114. The optical receiving elements 109 are each connected to the measuring amplifier 116 via two lines 115. The measuring amplifier delivers an output signal 117 that can be used to determine the speed of the milk.

FIG. 6 shows a fourth exemplary embodiment of the measuring devices 106, 107 for determining the volume flow or measuring current and the speed of a milk flowing during a milking process.

The structure of the measuring device 106 corresponds to the structure of the measuring device 106, as shown in FIG. 10 or in FIG. 5.

Viewed in the flow direction of the milk, the device for determining the capacity is followed by the measuring device 107 for determining the speed of the milk. The structure of the measuring device 107 for determining the speed of the milk corresponds to the structure of the measuring device 106 for determining a capacity. The measuring device 107 for determining the speed also has two plates 103, 104 which are parallel and spaced apart.

FIG. 7 schematically shows the device for determining a mass flow of milk flowing during a milking process. The device has a measuring device 106 for determining a capacity of the flowing milk or a characteristic variable proportional to the capacity. Furthermore, a measuring device 107 is provided for determining the speed of the milk. The measuring device 106 and the measuring device 107 are connected to an evaluation unit 118. The device also has a control unit 119, which is connected to the evaluation unit 118 and the measuring device gen 106, 107 is connected, wherein the control unit 119 controls the measuring devices at predetermined time intervals.

The evaluation of the actual data follows, in particular in the evaluation unit 118, in particular the measuring device for determining the capacity with regard to relevant variables.

At each sampling time, the capacity of the flowing milk or a characteristic capacity parameter is determined within a given measurement volume. The measurement volume is predetermined by the free flow cross section 105 and the height of the plates 103, 104. The measuring device 106 supplies a voltage at predetermined sampling times, which is proportional to the capacity of the milk. The temporal change in the voltage U (C) at specific sampling times t _k is shown in FIG. 9.

The evaluation of an appropriate capacity or characteristic variable proportional to the capacity follows in the evaluation unit 118. With this evaluation, the actual milk volume within the measurement volume can be determined.

The speed of the milk is determined by the measuring device 107. Due to the spaced-apart transmission and reception elements, two measuring points are given, each of which detects the start of a milk stopper with a time offset Δt. From this offset .DELTA.t, the speed can be determined at the known distance of the optical transmitting and receiving elements. FIG. 10 shows the course of the voltage signal of the measuring device for determining the speed and the associated delay times Δt at certain sampling times t. From the knowledge of the volume and the speed, the volume flow of a milk flowing during a milking process can be determined.

Knowing the capacity of the milk or a parameter proportional to the capacity can be used to determine a milk mass that is actually within the measurement volume. Knowing the speed of the milk, the mass flow of milk can be determined from the data thus determined.

LIST OF REFERENCE NUMBERS

management

Milk first measuring point

Second measuring point sensor

sensor

signal line

evaluation

signal line

output device

Connection line third measuring point

sensor

signal line

capacitor

arrow

plate

Plate free flow cross section

measuring device

Sending and receiving device

signal line

measuring amplifiers 113 measuring amplifier

114 line

115 line

116 measuring amplifier

117 output signal

118 evaluation unit

119 control unit

Claims

claims

1. A method for determining a volume volume of milk flowing during a milking process, comprising the following steps:

a) determining a cross-sectional area (Ai) of the flow cross-section of the milk flow (2) or a parameter proportional to the cross-sectional area (Ai) at a first measuring point (3);

b) Measurement of the time (ti) that the milk flow (2) with the cross-sectional area (Ai) determined in step a) takes to get from the first measuring point (3) to a second measuring point (5) provided downstream of the first measuring point ;

c) determining the flow velocity (vi) from the measured time (ti) and the known distance (s) between the first and second measuring points (3, 5);

d) Determination of the volume flow (V (t)) on the basis of the determined cross-sectional area (Ai) and the flow velocity (vi).

2. The method according to claim 1, wherein a total volume flow is determined by a plurality of samples and preferably by integration of the volume flow (N (t)) over time.

3. The method of claim 1 or 2, wherein an average flow rate is determined, at least if the ratio between the cross-sectional area (Ai) and a free flow cross-section of the line corresponds essentially to one.

4. The method according to claim 1, 2 or 3, in which downstream of the second measuring point (5) at least one further measuring point (12) is provided, which is used to determine the flow rate.

5. The method according to at least one of claims 1 to 4, in which at least one of the measuring points (3, 5, 12) the conductivity, the capacitance or the inductance of the milk is measured.

6. The method according to claim 5, wherein the conductivity of the milk is measured by means of a ring electrode.

7. The method according to at least one of the preceding claims, in which the cross-sectional area (Ai) is optically recorded at at least one of the measuring points (3, 5, 12).

8. The method according to at least one of the preceding claims, in which at each sampling time (t _k ) a characteristic capacity parameter of the flowing milk is determined within a predetermined measurement volume, the characteristic capacity parameter of the milk is used to determine the actual milk volume within the measurement volume with known capacities or previously known parameters compared and the speed of the milk flow determined and the milk flow determined from this data.

9. The method according to claim 8, in which the characteristic capacity parameter is determined by measuring at least two capacitance values, the at least two capacitance values taking place at at least two spaced-apart locations and the time offset (Δt) of the signals associated with the capacitances for determining the speed is used.

10. The method according to at least one of the preceding claims, wherein the determination of the speed is carried out optically.

11. The method according to at least one of the preceding claims, in which the determination of the capacitance takes place at at least two different frequencies and / or temperatures.

12. The method according to at least one of the preceding claims, in which the mass of milk is derived from the measured values.

13. Device for determining a volume flow of milk flowing during a milking process, characterized by a first measuring point (3) with at least one sensor (4) arranged outside the flowing milk, a second downstream measuring point (5) with at least one outside the flowing milk arranged sensor (6), and an evaluation unit (8) to which the sensors (4, 6) correspond

Deliver signals.

14. The apparatus according to claim 13, characterized in that at least one further measuring point (12) with at least one sensor (13) is provided downstream of the second measuring point (5).

15. The device according to claim 13 or 14, characterized in that at least one sensor (4, 6, 13) is taken from a group of sensors which comprises a conductivity sensor, a capacitance sensor, an inductance sensor, a photodetector and the like.

16. The apparatus according to claim 15, characterized in that the sensor (4, 6, 13) is designed in the form of a ring electrode.

17. The apparatus according to claim 15 or 16, characterized in that the line between two conductivity sensors is formed from an electrically insulating material.

18. The device according to at least one of claims 13 to 17, characterized in that the evaluation unit (8) has at least one Cayman filter.

19. The device according to at least one of claims 13 to 18, wherein at least one of the at least one sensor (106) is a measuring device (6) for determining a capacity (C _κ ) of the flowing milk or a characteristic variable proportional to the capacity (C), and a measuring device (107) for determining the speed of the

Milk is provided, and wherein in the evaluation unit (118) the actual data are evaluated with respect to relevant quantities using previously known data, and with a control unit (119) which is connected to the evaluation unit (118) and the measuring devices (106, 107), the control unit (119) activating the measuring devices at predetermined time intervals.

20. The apparatus according to claim 19, characterized in that the measuring device (106) for determining the capacitance (C has two spaced plates (103, 104).

21. The apparatus according to claim 20, characterized in that the plates (103, 104) are arranged in the flow path of the milk so that they can be at least partially washed around by the milk.

22. The apparatus according to claim 21, characterized in that the plates (103, 104) are arranged parallel to each other.

23. Device according to one of claims 19 to 22, characterized in that it has two measuring devices (106) arranged one behind the other in the direction of flow of the milk for determining a capacity (CJ of the flowing milk or a parameter proportional to the capacity (C), which has a correlation unit (120) are connected.