Milking system and a method for preventing detachment of a teat cup from a teat during a milking process

Abstract

A milking method and system for preventing detachment of a teat cup from a teat of an animal during a milking process where the milking system includes a milk line connected to the teat cup, a vacuum system that applies at least two different vacuum levels to the teat cup, a measuring device configured to measure the air flow in the milk line during the milking process, and a control unit (5) that receives information about measured air flow values and to determine if the teat cup is about to be detached from the teat by comparing the measured air flow values (q.sub.a) with an acceptable value (q.sub.a, q.sub.al/t), and when the measured air flow values are not acceptable, to control the vacuum system to apply a higher vacuum level to the teat cup than the present vacuum level.

Claims

1. A method for preventing detachment of a teat cup from a teat of an animal during a milking process performed by a milking system, wherein the milking system comprises a milk line (1b, 1c, 2) connected to the teat cup (1a) and to a milk meter (4) that measures air flow in the milk flow within the milk meter, a vacuum system that applies at least two different vacuum levels to the teat cup (1a), and a control unit (5) operatively connected to the milk meter and the vacuum system, the method comprising the steps of: while milking the animal during the milking process, the milk meter (4) making plural air flow measurements (q.sub.a) by measuring the air flow in the milk flow flowing through the milk meter; the control unit receiving the air flow measurements (q.sub.a) and comparing each of the air flow measurements (q.sub.a) to an acceptable maximum air flow value(q.sub.a, q.sub.amax/t); and when the comparing step finds that a current air flow measurement (q.sub.a) being greater than the acceptable maximum air flow value (q.sub.a, q.sub.amax/t) indicates air leakage into the teat cup and that the teat cup has started to detach from the teat, the control unit controling the vacuum system to increase the vacuum at the teat cup from i) a present vacuum level to ii) a higher vacuum level.

2. The method of claim 1, comprising the further steps of: after attaching the teat cup to the teat and during an initial phase of the milking the animal, the milk meter (4) making initial phase milk flow measurements (q.sub.m) by measuring the milk flow through the milk meter; the control unit receiving the initial phase milk flow measurements (q.sub.m) and comparing each of the initial phase milk flow measurements (q.sub.m) to an acceptable maximum milk flow value (q.sub.m, q.sub.max/t); and when the control unit finds that a current initial phase milk flow measurement (q.sub.m) being more than the acceptable maximum milk flow value (q.sub.m, q.sub.max/t) indicates a risk that the teat cup will detach from the teat, the control unit controling the vacuum system to increase the vacuum at the teat cup from i) a present initial vacuum level to ii) the higher vacuum level.

3. The method of the claim 2, wherein when the comparing step finds that the current initial phase milk flow measurement (q.sub.m) being less than the acceptable maximum milk flow value (q.sub.m, q.sub.max/t), which indicates that there is no risk of the teat cup detaching from the teat, the control unit controlling the vacuum system to decrease the vacuum at the teat cup from i) the present vacuum level to ii) a reduced vacuum level.

4. The method of the claim 3, comprising the further steps of: after the comparing step finds the current air flow measurement (q.sub.a) being greater than the acceptable air flow value (q.sub.a, q.sub.a1/t) and the control unit has increased the vacuum at the teat cup to the higher vacuum level, the milk meter (4) making milk flow measurements (q.sub.m) by measuring the milk flow through the milk meter while the high vacuum level is applied at the teat cup; the control unit receiving the milk flow measurements (q.sub.m) and comparing each of the milk flow measurements (q.sub.m) to an minimum acceptable milk flow value (q.sub.m, q.sub.m1/t); when the comparing step finds that a current phase milk flow measurement (q.sub.m) being more than the acceptable minimum milk flow value (q.sub.m, q.sub.m1/t)indicates continued milk flow from the teat, the control unit maintaining the higher vacuum level at the teat cup; and when the comparing step finds that a current phase milk flow measurement (q.sub.m) being less than the minimum acceptable milk flow value (q.sub.m, q.sub.m1/t) indicates that the teat cup has detached from the teat, the control unit controlling the milking system to stop the milking process.

5. The method according to claim 2, wherein the control unit substantially continuously receives the milk flow measurements and the air flow measurements from the milk meter during the milking process.

6. The method of the claim 1, comprising the further steps of: after the comparing step finds the current air flow measurement (q.sub.a) being greater than the acceptable maximum air flow value (q.sub.a, q.sub.amax/t) and the control unit has increased the vacuum at the teat cup to the higher vacuum level, the milk meter (4) making milk flow measurements (q.sub.m) by measuring the milk flow through the milk meter while the high vacuum level is applied at the teat cup; the control unit receiving the milk flow measurements (q.sub.m) and comparing each of the milk flow measurements (q.sub.m) to an minimum acceptable milk flow value (q.sub.m, q.sub.m1/t); when the comparing step finds that a current phase milk flow measurement (q.sub.m) being more than the acceptable minimum milk flow value (q.sub.m, q.sub.m1/t) indicates continued milk flow from the teat, the control unit maintaining the higher vacuum level at the teat cup; and when the comparing step finds that a current phase milk flow measurement (q.sub.m) being less than the minimum acceptable milk flow value (q.sub.m, q.sub.m1/t) indicates that the teat cup has detached from the teat, the control unit controlling the milking system to stop the milking process.

7. The method according to claim 6, wherein when said comparing step finds that the current phase milk flow measurement (q.sub.m) is more than the acceptable minimum milk flow value (q.sub.m, q.sub.m1/t), the control unit continues to maintain the higher vacuum level at the teat cup and repeats said comparing step of finding the current air flow measurement (q.sub.a) being greater than the acceptable maximum air flow value (q.sub.a, q.sub.amax/t) and the control unit controlling the vacuum system to maintain the vacuum at the teat cup to the higher vacuum level.

8. The method according to claim 1, wherein the step of comparing each of the air flow measurements (q.sub.a) to the acceptable maximum air flow value (q.sub.a, q.sub.amax/t), includes i) calculating a value of present air flow increase per unit time (q.sub.a/t) by using the plural air flow measurements, and ii) comparing the calculated present value of air flow increase per unit time to the acceptable maximum air flow value expressed as a maximum allowable value of air flow increase per unit time (q, q.sub.amax/t) to determine that the teat cup (1a) is about to be detached from the teat (1a) and have the control unit control the vacuum system to increase the vacuum at the teat cup from i) the present vacuum level to ii) the higher vacuum level.

9. The method according to claim 8, wherein the maximum air flow increase per unit time (q.sub.amax/t) is calculated for a time less than one second.

10. The method according to claim 1, wherein, said step of the milk meter (4) making plural air flow measurements (q.sub.a) by measuring the air flow in the milk flow flowing through the milk meter, comprises the further step of the milk meter (4) making plural milk flow measurements (q.sub.m) by measuring the milk flow through the milk meter, said step of the control unit receiving the air flow measurements (q.sub.a) and comparing each of the air flow measurements (q.sub.a) to the acceptable maximum air flow value (q.sub.a, q.sub.amax/t), comprises the further step of the control unit receiving the phase milk flow measurements (q.sub.m) and comparing each of the phase milk flow measurements (q.sub.m) to an acceptable maximum milk flow value (q.sub.m, q.sub.max/t), and the comparing step determines when the teat cup is about to be detached from the teat based on both i) whether the current air flow measurement (q.sub.a) is greater than the acceptable maximum air flow value (q.sub.a, q.sub.amax/t), and ii) whether a current phase milk flow measurement (q.sub.m) is more than the acceptable minimum milk flow value (q.sub.m, q.sub.m1/t).

11. The method according to claim 1, wherein, said step of the milk meter (4) making plural air flow measurements (q.sub.a) by measuring the air flow in the milk flow flowing through the milk meter, further comprises the milk meter (4) making plural milk flow measurements (q.sub.m) by measuring the milk flow through the milk meter, said step of the control unit receiving the air flow measurements (q.sub.a) and comparing each of the air flow measurements (q.sub.a) to the acceptable maximum air flow value (q.sub.a, q.sub.amax/t), further comprises the control unit receiving the phase milk flow measurements (q.sub.m) and comparing each of the phase milk flow measurements (q.sub.m) to an acceptable maximum milk flow value (q.sub.m, q.sub.max/t), and the comparing step determines when the teat cup is about to be detached from the teat based on both i) the air flow measurements (q.sub.a) and ii) the phase milk flow measurements (q.sub.m).

12. A milking system for preventing detachment of a teat cup from a teat of an animal during a milking process, the milking system comprising: a milk meter (4) that measures air flow in milk flow within the milk meter during milking the animal during the milking process; a milk line (1b, 1c, 2) connected to the teat cup (1a) and to the milk meter (4); a vacuum system that applies at least two different vacuum levels to the teat cup (1a); and a control unit (5) operatively connected to the milk meter and the vacuum system, wherein, while milking the animal during the milking process, the milk meter (4) makes plural air flow measurements (q.sub.a) by measuring the air flow in the milk flow flowing through the milk meter, when the control unit receives the air flow measurements (q.sub.a) and compares each of the air flow measurements (q.sub.a) to an acceptable maximum air flow value (q.sub.a, q.sub.amax/t); and when the control unit finds that a current air flow measurement (qa) being greater than the acceptable maximum air flow value (q.sub.a, q.sub.amax/t), which indicates air leakage into the teat cup and that the teat cup has started to detach from the teat, the control unit controls the vacuum system to increase the vacuum at the teat cup from i) a present vacuum level to ii) a higher vacuum level.

13. The milking system of claim 12, wherein, during an initial phase of the milking process, the milk meter (4) makes initial phase milk flow measurements (q.sub.m) by measuring the milk flow through the milk meter, the control unit receives the initial phase milk flow measurements (q.sub.m) and comparing each of the initial phase milk flow measurements (q.sub.m) to an acceptable maximum milk flow value (q.sub.m, /t), and when the control unit finds that a current initial phase milk flow measurement (q.sub.m) being more than the acceptable maximum milk flow value flow value (q.sub.m, q.sub.max/t) indicates a risk that the teat cup will detach from the teat, the control unit controls the vacuum system to increase the vacuum at the teat cup from i) a present initial vacuum level to ii) the higher vacuum level.

14. The milking system of claim 13, wherein when the control unit finds that the current initial phase milk flow measurement (q.sub.m) being less than the acceptable maximum milk flow value (q.sub.m, q.sub.max/t) indicates that there is no risk of the teat cup detaching from the teat, the control unit controls the vacuum system to decrease the vacuum at the teat cup from i) the present vacuum level to ii) a reduced vacuum level.

15. The milking system of claim 14, wherein, after the control_unit finds the current air flow measurement (q.sub.a) being greater than the acceptable air flow value (q.sub.a , q.sub.a1/t) and the control unit controls the vacuum system to increase the vacuum at the teat cup to the higher vacuum level at the teat cup, the milk meter (4) making milk flow measurements (q.sub.m) by measuring the milk flow through the milk meter while the high vacuum level is applied at the teat cup, the control unit receives the milk flow measurements (q.sub.m) and compares each of the milk flow measurements (q.sub.m) to an minimum acceptable milk flow value (q.sub.m, q.sub.m1/t), when the control unit finds that a current phase milk flow measurement (q.sub.m) being more than the acceptable minimum milk flow value (q.sub.m, q.sub.m1/t) indicates continued milk flow from the teat, the control unit maintains the higher vacuum level at the teat cup; and when the control unit finds that a current phase milk flow measurement (q.sub.m) being less than the minimum acceptable milk flow value (q.sub.m, q.sub.m1/t) indicates that the teat cup has detached from the teat, the control unit controls the milking system to stop the milking process.

16. The milking system of claim 12, wherein, after the control unit finds the current air flow measurement (q.sub.a) being greater than the acceptable maximum air flow value (q.sub.a, q.sub.amax/t) and the control unit controls the vacuum system to increase the vacuum at the teat cup to the higher vacuum level at the teat cup, the milk meter (4) makes milk flow measurements (q.sub.m) by measuring the milk flow through the milk meter while the high vacuum level is applied at the teat cup, the control unit receives the milk flow measurements (q.sub.m) and compares each of the milk flow measurements (q.sub.m) to an minimum acceptable milk flow value (q.sub.m, q.sub.m1/t), when the control unit finds that a current phase milk flow measurement (q.sub.m) being more than the acceptable minimum milk flow value (q.sub.m, q.sub.m1/t) indicates continued milk flow from the teat, the control unit maintains the higher vacuum level at the teat cup; and when the control unit finds that a current phase milk flow measurement (q.sub.m) being less than the minimum acceptable milk flow value (q.sub.m, q.sub.m1/t) indicates that the teat cup has detached from the teat, the control unit controls the milking system to stop the milking process.

17. The milking system of claim 12, wherein when the control unit compares each of the air flow measurements (q.sub.a) to the acceptable maximum air flow value (q.sub.a, q.sub.amax/t), the control unit further i) calculates a value of present air flow increase per unit time (q.sub.a/t) by using the plural air flow measurement, and ii) compares the calculated present value of air flow increase per unit time to the acceptable maximum air flow value expressed as a maximum allowable value of air flow increase per unit time (q.sub.amax/t) to determine that the teat cup (1a) is about to be detached from the teat (1a) and have the control unit control the vacuum system to increase the vacuum at the teat cup from i) the present vacuum level to ii) the higher vacuum level.

18. The milking system of claim 12, wherein when said control unit finds that the current phase milk flow measurement (q.sub.m) is more than the acceptable minimum milk flow value (q.sub.m, q.sub.m1/t), the control unit continues to maintain the higher vacuum level at the teat cup and when the control unit repeatedly finds the current air flow measurement (q.sub.a) being greater than the acceptable maximum air flow value (q.sub.a, q.sub.amax/t), the control unit controls the vacuum system to maintain the vacuum at the teat cup to the higher vacuum level.

19. The milking system of claim 12, wherein, said milk meter (4) makes plural milk flow measurements (q.sub.m) by measuring the milk flow through the milk meter, said control unit receives the phase milk flow measurements (q.sub.m) and compares each of the phase milk flow measurements (q.sub.m) to an acceptable maximum milk flow value (q.sub.m, q.sub.max/t), and the control unit determines when the teat cup is about to be detached from the teat based on both i) whether the current air flow measurement (q.sub.a) is greater than the acceptable maximum air flow value (q.sub.a, q.sub.amax/t), and ii) whether a current phase milk flow measurement (q.sub.m) being more than the acceptable minimum milk flow value (q.sub.m, q.sub.m1/t).

20. The milking system of claim 12, wherein, said milk meter (4) makes plural milk flow measurements (q.sub.m) by measuring the milk flow through the milk meter, said control unit receives the phase milk flow measurements (q.sub.m) and compares each of the phase milk flow measurements (q.sub.m) to an acceptable maximum milk flow value (q.sub.m, q.sub.max/t); and the control unit determines when the teat cup is about to be detached from the teat based on both i) the air flow measurements (q.sub.a) and ii) the phase milk flow measurements (q.sub.m).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is now to be explained more closely by means of preferred embodiments, which are disclosed as examples, and with reference to the attached drawings.

(2) FIG. 1 shows a milking system according to an embodiment of the invention,

(3) FIG. 2 shows a graph illustrating the milk flow as a function of the time during a milking process and

(4) FIG. 3 shows a block diagram of a method according to an embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

(5) FIG. 1 shows a milking member 1 in the form of a cluster. The cluster comprises four teat cups a. The teat cups 1a are connected to a claw 1c by means of a respective short milk tube 1b. A milk line 2 is configured to transport milk from the claw 1c to a main milk line 3. The main milk line 3 may receives milk from a plurality of milking members 1. The main milk line 3 is connected to a vacuum source applying a high vacuum level, which may be of about 50 kPa, to the milk line 3. The milk is transported in the main milk line 3 by means of the vacuum source to a not shown milk storage device in the form of a milk tank or the like. A milk meter 4 is arranged in the milk line 2. The milk meter 4 is configured to measure the milk flow q.sub.m in the milk line 2. The milk meter 4 is also able to measure the air flow q.sub.a in the milk line 2.

(6) A control unit 5 is configured to receive substantially continuously information from the milk meter 4 about the milk flow q.sub.m and the air flow q.sub.a in the milk conduit 2 during a milking process. The vacuum system comprises a vacuum line 6. The vacuum level in the vacuum line is a high vacuum level, which may be of about 50 kPa. Thus, the vacuum line 6 and the main milk line 3 have the same high vacuum level. A vacuum regulating valve 7a is connected to the vacuum line 6 via a first vacuum conduit 8a. A control valve 7b is arranged in the milk line 2. The control valve 7b is connected to the vacuum regulating valve 7a via a second vacuum conduit 8b. The milk line 2 comprises a first part 2a arranged upstream of the control valve 7b and a second part 2b arranged downstream of the control valve 7b with respect to the intended milk flow direction in the milk line 2. The control valve 7b has a design such it provides the same vacuum level in the first part of the 2a of the milk line as in the second vacuum conduit 8b.

(7) The vacuum regulating valve 7a is settable in at least two different regulating positions. The vacuum regulating valve 7a is settable in a high vacuum position in which it does not reduce the vacuum in the vacuum line 6 at all. Consequently, the high vacuum level in the vacuum line 6 is applied unchanged, via the first vacuum conduit 8a and the vacuum regulating valve 7a, to the second vacuum conduit 8b and to the control valve 7b. In this case, the control valve 7b does not reduce the vacuum level in the first part 2a of the milk line 2 in relation to the vacuum level in the second part 2b of the milk line 2 and the main milk line 3.

(8) The vacuum regulating valve 7a is settable in at least one vacuum reducing position in relation to the high vacuum position. When the vacuum regulating valve 7a is in the vacuum reducing position, a low vacuum level, which may be about 42 kPa, in the second vacuum conduit 8b in relation to the high vacuum level of about 50 kPa. In this case, the control valve 7b reduces the vacuum level in the first part of the milk line 2a to the low vacuum level. Thereby, the vacuum level in the first part of the milk line 2a is lower than the vacuum level in the second part of the milk line 2b. The control unit 5 is able to set the vacuum regulating valve 7a in the high vacuum position and in the vacuum reducing position by means of information about measured air flow values q.sub.a and milk flow values q.sub.m from the milk meter 4 in the milk line 2.

(9) During a milking process, vacuum is applied to the teat cups 1a. A first object of the vacuum in the teat cup 1a is to transport the milk from the teat cup 1, via the milk line 2, to the main milk line 3. A second object of the vacuum is to provide a substantially air tight connection between the teat cups 1a and the teats such that the teat cup 1a obtains an attachment to a teat by means of a suction force. The vacuum level in the teat cups 1a during a milking process depends on, for example, the milk flow and air flow through the teat cup 1a. A high milk flow decreases the vacuum level in the teat cups 1a. A high air flow also decreases the vacuum level in the teat cups 1a. If the vacuum level in a teat cup 1a decreases, such as for example of an extremely high milk flow, the suction force between the teat cup 1a and the teat decreases. There is here a risk that air starts to leak into the teat cup 1a. An air leakage increases the air flow in the milk line 2 and the vacuum level in the teat cup 1a is further decreased. If the vacuum level in the teat cup 1a becomes too low, the teat cup 1a falls off from the teat. Usually, this process occurs rapidly within some seconds.

(10) FIG. 2 shows how the air flow may vary with the time during a milking process. The teat cups la are attached to the teats of a cow at the time t.sub.0. Initially, an increased air flow q.sub.a may obtain in connection with the attachment of the teat cups 1a to the teats. When the teat cups 1a have been fixedly attached to the teats, a small relatively constant air flow q.sub.a is sensed by the milk meter 4 in the milk line 2 during a large part of the milking process. The teat cup 1a or the short milk tubes 1b comprises one or several inlet openings for air in order to guarantee a relatively small air flow through the milk line 2 in order to ensure the transportation of milk. However, at the time t.sub.1, the air flow q.sub.a is suddenly increased. The air flow q.sub.a is here increased to a higher value than a maximum allowable air flow q.sub.amax. The control unit 5 determines, in view of received measured air flow values q.sub.a from the milk meter 4, that one of the teat cups 1a is about to be detached from a teat. The control unit 5 sets the regulating valve 7a in the high vacuum position such that a higher vacuum level is applied to the teat cups 1a than the present vacuum level. The higher vacuum in the teat cups 1a results in an increased suction force between teat cups 1a and the teats. Usually, this measure reduces the air leakage into the teat cup la and the air flow q.sub.a is relatively quickly decreased to the preceding air flow level. Due to the quickly applied higher vacuum level to the teat cup 1a at the time t.sub.1, the teat cup 1a was, in this case, prevented from being detached from the teat. The initially used vacuum level may be restored in the teat cups 1a as soon as the control unit 5 receives information indicating that air flow has been reduced to a normal flow level. During the following part of the milking process, a small relatively constant air flow q.sub.a is sensed by the milk meter 4. The milking process is finished at the time t.sub.2 and the teat cups are removed from the teats. A temporarily increased air flow q.sub.a may occur when the teat cups 1a are removed from the teats.

(11) FIG. 3 shows a block diagram illustrating a process and a method which may be performed by the use of the milking system in FIG. 1. The process starts, at 12, and a milking animal in the form of a cow enters a milking stall or the like provided with a milking member 1 of the milking system. The teat cups 1a are attached to the teats of the cow manually or by means of a milking robot. The control unit 5 receives substantially continuously information from the milk meter 4 about the milk flow qm and the air flow qa in the milk line 2. At 13, the control unit 5 compares measured milk flow values qm with a maximum milk flow value q.sub.max. If the milk flow qm is higher than a predetermined maximum milk flow value q.sub.max, the control unit 5 determines that there is a risk that the teat cups will be detached. The control unit 5 sets the vacuum reducing valve 7a in the high vacuum position such that a high vacuum level is applied to the teat cups 1a.

(12) The process starts again at 12 and the control unit 5 receives again information of measured milk flow values qm. At 13, the control unit 5 compares the measured milk flow values qm with the maximum milk flow value q.sub.max. If the milk flow qm now is lower than the predetermined maximum milk flow value q.sub.max, the control unit 5 determines that there is no risk that the teat cups will be detached from the teats. Mostly, the control unit 5 determines, at 13, that the milk flow qm is lower than the maximum allowable value q.sub.max. The control unit 5 sets the vacuum regulating valve 7a in the vacuum reducing position, at 15, and the control valve 7b provides a reduced vacuum level to the first part of the milk line 2a.

(13) The milking process is continued at 16. The control unit 5 compares here measured air flow values q.sub.a with a maximum allowable air flow q.sub.amax. A too high air flow q.sub.a in the milk line 2 indicates in air leakage into a teat cup 1a and that one of the teat cups 1a has started to detach from the teat. If the air flow q.sub.a is lower than the maximum allowable air flow q.sub.amax, the control unity 5 determines that no teat cup 1 has started to detach from a teat. In this case, the process starts again, at 12. Alternatively or in combination, the control unit 5 may, at 16, calculate a value of the air flow increase per unit time q.sub.a/t and if this calculated value is higher than a maximum allowable such value q.sub.amax/t, to control the vacuum system such that it applies a higher vacuum level to the teat cup 1a than the present vacuum level. The unit time t is, for example, less than one second.

(14) If the control unit instead determines, at 16, that air flow q.sub.a is higher than the maximum allowable air flow q.sub.amax, at least one of the teat cups 1 seems to have started being detached from the teat. The air leakage from the surrounding to this teat cup 1a results in a sudden and rapid increase of the air flow in the milk line 2. Something has to be done in order to prevent that the teat cup 1a comes loose from the teat. The control unit 5 sets, at 17, the vacuum regulating valve 7a in the high vacuum position such that the control valve 7b applies the high vacuum level to the teat cups 1a. The suction force between the teat cups 1a and the teats increases. The air leakage between the teat cup 1a and the teat is reduced. The control unit 5 compares again, at 18, measured air flow q.sub.a values with the maximum allowable air flow q.sub.amax. If the measured air flow q.sub.a now is lower than the maximum allowable air flow q.sub.amax, the control unit 5 determines that the teat cups 1 will not come loose from the teat. The process starts again at 12.

(15) If the air flow q.sub.a is still higher than the maximum allowable air flow q.sub.amax, the applied high vacuum has not reduced the air flow q.sub.a to a lower value than the maximum allowable air flow value q.sub.amax. The control unit 5 compares, at 19, measured milk flow q.sub.m values with a minimum allowable milk flow q.sub.m1. A too low milk flow indicates that at least one of the teat cups la have been detached from a teat. If the milk flow q.sub.m is higher than the minimum allowable milk flow q.sub.m1, the control unit 5 determines that the milk line 2 still receives milk from all teat cups 1a. Thus, none of the teat cups 1 have fallen off yet. The process continues, at 17, with an unchanged high vacuum. If instead the milk flow q.sub.m is lower than the minimum allowable air flow q.sub.a1, the control unit 5 determines that one of the teat cups has been detached from a teat. In this case, it is possible to stop the milking process at 20.

(16) The invention is not restricted to the described embodiments of the invention but may be varied freely within the scope of the claims. In the above mentioned embodiments, a milk line receives milk from four teat cups. It is of course possible to use one milk line for each teat cup and measure the air flow and the milk flow from each teat cup separately by means of a separate milk meter 4.