MILKING SYSTEM AND METHOD FOR CIRCULATING WASHING LIQUID FIELD OF INVENTION

The present invention relates generally to milking systems and particularly it relates to a milking system adapted to perform milking operations of animals as well as cleaning operations of the milking system itself. It also relates to a method for circulating cleaning liquid in the milking system.

BACKGROUND

Modern milking systems comprise milking stations able to milk animals, such as cows, and transfer the milk to a storage tank, while waiting for transport to a dairy plant. The milk is a vulnerable food product with high demands for cleanliness and handling temperatures, and it is important to protect it from micro organisms and prevent chemical reactions. Thus, the equipment, including conduits, pumps, valves etc, of such a milking system has to be cleaned regularly. A way to wash the equipment is to empty the system from milk and feed a cleaning liquid into the system and pump it through to efficiently remove milk remains .

EP0626130 describes a construction for milking animals, wherein milk are drawn from the animal to a collecting glass 6, and further to a milk tank 3, via a pump 9 [see column 3, line 6-17 and fig.]. The construction can be cleaned by circulating cleaning fluid via reservoir 17 through teat cups back to the collecting glass 6, by means of the pump 9 [column 3, line 53 — column 4, line H]. Thus, the same pump 9 is used for milking as well as for cleaning. However, milk is an emulsion of butter

fat in water and is vulnerable to dynamical pressures and flows and rough mechanical treatment.

SUMMARY OF THE INVENTION

An object of the present invention is to solve the problems mentioned above and provide a milking system handling milk carefully and also being able to provide a sufficient washing of the system itself. The invention provides an improvement of a milking system for extracting milk from a milk producing animal and transferring the milk to a milk tank, comprising milk extracting means, an intermediate container and milk transferring means, wherein the extracting means is arranged to extract milk from the animal to the intermediate container, and the transferring means is arranged to provide a first pump capacity to transfer the milk from the intermediate container to the milk tank, the system further comprising a return line for circulating washing liquid in the system. The system according to the invention is characterised in that it is arranged to provide a second pump capacity to circulate the washing liquid, and this second pump capacity is higher than the first pump capacity. In this way milk can be carefully transferred by the first lower pump capacity and a suitable higher second pump capacity can provide sufficient flushing of cleaning liquid through the system.

In an embodiment of the invention the first pump has a variable power and is arranged to provide a higher pump capacity to circulate the washing liquid than to transfer the milk, thereby reaching the second pump capacity. In this way only one pump is needed to provide

both low power milk pumping and higher power washing liquid pumping.

In an embodiment of the invention the first pump is arranged to provide the first pump capacity to circulate the washing liquid, and the system further comprises a second pump arranged in the return line for providing additional circulation power for the washing liquid, thereby reaching the second pump capacity. By including a second pump and arranging it in the return line, lesser demands for the mechanical and dynamical influence on the milk and the cleanness of this pump are present since it only pumps cleaning liquid and not milk. Preferably, an additional container is also arranged in the return line, and it is connected to a vacuum source arranged to transfer washing liquid from the transport line to the additional container. This vacuum source can lower the pressure on the high pressure side of the first pump and, if the intermediate container is connected to a vacuum source, can neutralize a vacuum in the intermediate container. Also, since lowering the pressure on the high pressure side of the first pump, it reduces the risk of washing liquid leaking and blending with the milk.

In another embodiment, the milk extracting means comprises a plurality of teat cups fluidly connected to the intermediate container, and a vacuum source that is arranged to selectively provide, and inactivate, a suction vacuum in the intermediate container. Preferably, the milking system inactivates the suction vacuum during the transfer of the milk from the intermediate container, so that the pressure in the

intermediate container is kept at atmospheric pressure. By keeping the pressure at atmospheric pressure the pumping power can be kept low, which facilitates a gentle transfer of the milk.

A gentle transfer is also facilitated in an embodiment of the invention where the milking system is arranged to transfer the milk from the intermediate container to the milk cooling tank before the milk is cooled, so that the milk is transferred near its original temperature, where it is less vulnerable.

It is also an object of the invention to provide a method for circulating washing liquid in the milking system. This method is characterised by circulating washing liquid by means of a pump capacity that is greater than the pump capacity used for transferring milk from the intermediate container to the milk tank.

Further preferred embodiments are defined by the dependent claims.

BRIEF DESCRIPTION OF DRAWINGS The invention is described below, by way of example, with reference to the accompanying drawings, in which:

figure 1 illustrates parts of a milking system during milking,

figure 2 illustrates parts of a milking system during transfer of milk from a milking station to a milk tank,

figure 3 illustrates an embodiment of a milking system during washing of the system,

figure 4 illustrates another embodiment of a milking system during washing of the system, and

figure 5 illustrates a milking system comprising a plurality of milking stations.

The figures illustrate the main parts of a system in accordance with the invention schematically and they are not drawn to scale.

DETAILED DESCRIPTION OF EMBODIMENTS

In the following a detailed description of embodiments of the present invention will be given. The figures 1-4 illustrate the milking system during different operations, figure 1 during milking, figure 2 during transfer of milk and figure 3 and figure 4 different embodiments during washing of the system.

Figure 1 illustrates a milking station 1 for extracting milk from milk producing animals, such as cows. The station comprises milk extraction means in the form of four teat cups 3, a vacuum source 4 and teat cup conduits 5 illustrated as one bundle 5 of conduits. The teat cups are connected to an intermediate container 6 via the teat cup conduits 5. The vacuum source 4 is connected to and arranged to selectively apply a low suction pressure to the intermediate container 6. During milking of an animal, the teat cups 3 are attached to the teats of the animal, and milk is sucked through the conduits 5 to the intermediate container 6 by means of the low pressure provided by the vacuum source 4 to the intermediate container. Thus, the intermediate container is connected to the vacuum source on one side and to the

teats of the animal, via the teat cups and conduits, on the other side during milking. The intermediate container is designed to contain at least the amount of milk produced during milking of one animal. It is also suitable to provide milk testing equipment in association with the intermediate container so that the quality of the milk can be tested.

Figure 2 illustrates a milk transferring system for transferring the milk from the intermediate container to a milk tank 2, such as a milk cooling tank. The transferring system comprises a pump 8 and a transport conduit 9 forming a transport line from the intermediate container to the milk tank. The transferring system is arranged to transfer milk from the container to the tank after an animal has been milked. During this transfer the vacuum source (4 in figure 1) is preferably inactivated and the intermediate container 6 is, preferably, brought to atmospheric pressure by, e.g., opening the container to the surrounding air by a pressure relief valve, indicated by 7. The pump is adapted to provide a suitable pumping power so that the milk is transferred by a pump capacity high enough to overcome flow resistance in the transferring system and differences in height levels, but should be kept low to prevent affecting the milk in a negative way, such as risking to increase the levels of free fatty acids in the milk due to high pumping speed and power. For a gentle transfer, the milk can be held at its original temperature, ca 35-38° C, in the intermediate container 6, which can be insulated, and be cooled firstly when arriving in the milk tank. During the transfer of the milk the milked animal can be replaced by an animal to

be milked and this further animal is suitably cleaned before it is milked. The milking station can be an automatic milking station provided with means for cleaning at least the teats of the animal prior to applying the teat cups and extracting milk from the further animal. However, the cleaning of the animal is not discussed since it is not a major aspect of the inventive system.

The milk extracting means and the transferring system are also used for washing its individual parts by flushing a washing liquid, such as water, through them. This washing operation is performed by supplying washing liquid to the teat cups 3, e.g. by placing them in a trough or connecting them to cleaning liquid supplying nozzles 21 in a cleaning shelf 11, and drawing the liquid by means of the vacuum source, through the teat cups 3, the conduits 5 and into the intermediate container 6. The washing liquid is transferred further by being pumped from the intermediate container 6 by the pump 8 through the transferring system. Instead of supplying the washing liquid to the milk tank 2, it is transferred back to the milking station by means of a return line, which will be discussed in detail below referring to Fig. 3 and 4, or to a drain outlet.

An example of a system having a return line for the washing fluid is illustrated in figure 3. The return line comprises a return conduit 12 connecting the transport conduit 9, at the milk tank 2, from a valve arrangement 10a, 10b, selectively connecting the transport conduit 9 to the milk tank 2 and the return conduit, respectively, to the milking station 1. Thus,

the return line provides a circulation loop for the washing fluid from the cleaning shelf 11 and the teat cups 3, through the teat conduits 5, the intermediate container 6, the transferring system and back to the nozzles 21 in the cleaning shelf 11 through the return line. Means for supplying washing liquid is also provided, illustrated as two water pipes with supply valves 22, and arranged to supply liquid to the cleaning shelf 11. During washing of this system the pump 8 is arranged to provide the pump capacity necessary to circulate the washing liquid. In this system the pump 8, as mentioned in accordance with fig. 2, is adapted to provide a pumping capacity, when transferring milk, which does not adversely affect the milk. To be able to achieve this the pump 8 is a pump having a variable power so that it can provide a first sufficiently low capacity when pumping milk, without affecting the milk negatively, and a second higher capacity when pumping washing liquid, so that the washing provides a suitable washing force when flushing the system. The pump is, for example, a variable frequency pump, and is also of a type suitable for the high cleaning demands for treating food. This system is also suitably equipped with a control unit 13 for the pump, and a sensor 17 measuring the flow in the transferring system, between the intermediate container and the pump 8, so that the control unit controls the pumping capacity, during milk transfer, based on flow speed measurements provided by the sensor. In this way the system can automatically adjust the low power level for milk pumping depending on varying resistance and milk levels in the system. During pumping of washing liquid, the pump 8 is controlled to

provide a second higher capacity, such as a maximum pumping capacity, of the pump. A second flow sensor 18 measuring outputted flow from the pump 8 is also illustrated.

As an alternative to a pump with variable speed a two- speed pump can be used, with low milk transferring speed and a higher cleaning speed. As an alternative to the flow sensors, the flow can be controlled by registering the electric current of the motor and controlling its frequency.

Another example of a system and a return line for the washing fluid is illustrated in figure 4. The return line comprises a return conduit 12 and a second pump, or return pump, 14. The return line is here also connected at the milk tank 2, by the valve arrangement 10a-b, to the transport conduit 9 and the other end of the return line 12 is located at the milking station 1, so that a circulation circuit is provided for the washing liquid. As in the embodiment in figure 3 there are means for supplying washing liquid into the system, illustrated as two water pipes with supply valves 22, and arranged to supply liquid to the cleaning shelf 11. Preferably, the return line is also provided with a variable vacuum source 15 arranged at and connected to a return line container 16 between the transport conduit 9 and the return pump 14. The vacuum provided with the vacuum source 15 in the return line is preferably stronger, during the washing operation, than the vacuum provided by the vacuum source 4 in the intermediate container 6. In this way the first pump 8 is further helped by a positive pressure gradient from the intermediate

container to the vacuum source in the return line. The vacuum source 15 in the return line also prevents washing liquid from entering into the milk tank by- providing a suction pressure at the selective valve arrangement 10.

It is, however, possible to drive the washing liquid with the first pump 8 being assisted by the second pump 14 in the return line, without flow increasing devices, such as the second container 16 and vacuum source 15 combination, in the flow direction between the two pumps 8, 14.

The two embodiments of figures 3 and 4 can also be combined providing a first pump adapted to provide a first pumping power during transfer of milk and a higher power during washing in combination with a second pump providing additional pumping power for the washing liquid in the return line.

Figure 5 illustrates a milking system comprising a plurality of milking stations fluidly connected to a common transport conduit 9. The system comprises a plurality of intermediate containers 6a-c selectively connectable via respective transport lines 9a-c to the common transport conduit 9, by means of local valves 20a-c connecting each intermediate container to a respective local pump 8a-8c in the respective transport line, and connecting valves 19a-c at the common transport conduit 9.

The invention has been described in embodiments primarily for milking cows, but can be used for other kinds of milk producing animals, where the system

suitably is adapted for the type of animal, e.g. in size, in power levels and number of teat cups and so on. A person skilled in the art realises that the inventive system could be further varied within the scope of the appended claims.