MILKING DEVICE AND METHOD FOR AUTOMATICALLY MILKING ANIMALS

Abstract: The invention relates to a milking device for automatically milking animals, and in particular to the milk cooler (5) which is used to cool the collected milk before it is stored in a milk tank. The milk cooler (5) comprises a vessel filled with cooling liquid which is cooled by an evaporator (2) and a milk line which is cooled by the cooling liquid. According to the invention, the milk cooler (5) is provided with a storage vessel having means for storing the cooling liquid in the storage vessel during the internal cleaning of the milk line. The invention also relates to a method in which the milk which has been collected in a first milk vessel is pumped into the milk cooler, and in which, after a variable time, the milk from a following milk vessel is pumped into the milk cooler.

Description: Milking device and method for automatically milking animals The invention relates to a milking device as described in the preamble of claim 1. A milking device of this type is known from US 4,932,222, Adam. The drawback of the known device is that the cooling liquid has to be pumped around the milk line, with the result that unnecessary energy is imparted to the cooling liquid, and consequently additional cooling is required. To avoid this drawback, the device is designed as described in the characterizing clause of claim 1. As a result, during use the milk line is surrounded by cooling liquid without having to supply additional energy, while during its internal cleaning the milk line is surrounded by air, so that the washing liquid is not cooled. According to one refinement, the device is designed as described in claim 2. As a result, all the milk which has been collected from a cow can remain in the milk cooler for a certain time in order to cool. Consequently, it is easy to cool the milk to the storage temperature. According to one refinement, the device is designed as described in claim 3. This prevents material from being deposited on the inner side of the wall in the milk cooler, so that this wall is easier to clean. According to one refinement, the device is designed as described in claim 4. This makes it easy to empty the milk cooler. According to one refinement, the device is designed as described in claim 5. This makes the milk cooler of simple design. According to one refinement, the device is designed as described in claim 6. This further simplifies the internal cleaning of the milk line while ensuring uniform cooling of the milk. The invention also comprises a method as described in claim 7. This has the result that, before being stored in the milk tank, the milk remains in the milk cooler for a certain time for cooling purposes. According to one refinement, the method is carried out as described in claim 8. This ensures that the milk is sufficiently cooled. The invention is explained below with reference to a number of exemplary embodiments and with the aid of a drawing, in which: Figure 1 shows a diagrammatic cross section through a milk cooler, and Figure 2 shows a circuit diagram of the lines running between the various components of a milking device. Figure 1 shows a cooling unit 5 for cooling milk. The cooling unit 5 comprises a cylindrical shell 3 with a base 16 and an upper wall 11, which may be removable if appropriate. Insulation 4 is fitted around the outer shell 3, the base 16 and the upper wall 11. In the outer shell 3 there is an evaporator 2 for cooling the cooling liquid which is present in the cooling unit 5. A bundle of lines 19 are positioned inside the cooling unit 5. The bundle of lines 19 is arranged around a supporting pipe 10 and comprises an uninterrupted tube of constant cross section. The tube is coupled to a feed line 12 and is wound in a coil 21 from the support pipe 10 to the outer diameter. The coil 21 runs downwards on a slope in a descending plane and comprises, for example, 6 windings. At the outer diameter, the coil 21, via a connection 20, runs through to the next coil 21, which runs towards the support pipe 10 and likewise runs downwards on a slope and, on the inner side, is in turn connected, via a connection 20, to the next coil 21. This structure is repeated a number of times, and the line runs downwards on a slope without interruption, ending at an outlet line 15, where the line leaves the cooling unit 5. The coils 21 are attached in a known way to the support pipe 10. The support pipe 10 stands on the base 16. Around the bundle of lines 19 there is a guide plate 1 with openings 17 at the bottom. During use, the cooling unit 5 is filled with a cooling liquid, such as for example "Pekasol". The cooling liquid must be suitable to transfer heat from the bundle of lines 19 to the evaporator 2. If water is used, it will be possible for a layer of ice to form around the evaporator 2, this ice forming, as it were, a cold buffer but also impeding the transfer of heat to the evaporator 2. By using a liquid which does not freeze, such as "Pekasol", and also does not form ice on the evaporator 2, it is possible for the evaporator 2 to reach a temperature which lies below the freezing point of the milk when the cooling liquid is at a temperature of 0° - 2°C. The milk will not freeze at this temperature yet the surface area of the evaporator 2 can remain limited. The level of the cooling liquid lies above the guide plate 1 extending approximately to the top of the outer shell 3. One or more agitators 9, which are driven by an agitator motor 8, are positioned above the bundle of lines 19. A coolant is expanded in the outer shell 3, specifically in the evaporator 2, with the result that the outer shell becomes very cold and the liquid in the cooling unit 5 is cooled. As a result, and on account of the agitators 9, a flow which rises upward through the bundle of lines 19 and runs downward along the evaporator 2 is formed in the cooling unit 5. The liquid which is to be cooled, such as milk, reaches the feed line 12 into the cooling unit 5 at a temperature of approximately 38 °C, is cooled to the temperature of the cooling liquid and emerges from the cooling unit 5 at the outlet line 15 at this temperature . The evaporator 2 is provided, in a known way, with a thermostatically controlled valve which ensures that, through evaporation of coolant, the liquid which circulates in the cooling unit 5 is kept at a temperature of approximately 0°C. Consequently, the milk, when it leaves the cooling unit 5 via the outlet line 15, is also at a temperature of approximately 0°C. The dimensions of the bundle of lines 19 are such that the volume of the milk which is present in the bundle of lines corresponds to the maximum amount of milk which is to be yielded by one cow is one milking session. This means that the internal volume of the bundle of lines 19 corresponds, for example, to 15 liters, which means that, if the milk tube has an internal diameter of 12 mm, the tube length of the bundle of lines 19 is 150 m. If the external diameter of the coil 21 of the bundle of lines 19 is approximately 500 mm and the support pipe 10 has a diameter of 100 mm, it is possible to make approximately 6 windings per coil 21, so that approximately twenty-five coils 21 are required and the total bundle of lines 19 has a height of approximately 1 m. In another embodiment, in which the bundle of lines 19 is designed with a tube with an internal diameter of 18 mm, a tube length of 65 m is required and the height of the bundle of lines 19 is approximately 650 mm. The lines through which the milk flows are preferably made from thin-walled stainless steel . At A, the milk flows into the cooling unit 5 and passes through the bundle of lines 19 via the feed line 12. The milk leaves the cooling unit 5 via the outlet line 15 at B. To empty the bundle of lines 19, a valve 14 with an air inlet 13 is provided at the top of the cooling unit 5. When the valve 14 is opened, air flows into the milk line and the bundle of lines 19 can empty. During cleaning of the milk line, hot washing liquid is flushed through the milk line. To prevent all the cooling liquid which is present in the cooling unit 5 from having to be heated, so that the washing liquid is unnecessarily cooled, it is provided that the cooling liquid can run out of the cooling " unit 5 via an outlet 18 and a valve 27 to an inlet 23 of an insulated vessel 22. There is a vent 28 in the insulated vessel 22. When the cooling unit 5 is to be returned to use after the milk line has been cleaned, the cooling liquid, after the valve 27 has been closed, is pumped out of the vessel 22 back into the cooling unit 5 via a non-return valve 26 and the outlet 18, using a pump 25. After the cooling liquid has been allowed to run out of the cooling unit 5, hot washing liquid is flushed through the milk line, during which process the milk line can heat up to the temperature of this liquid, for example 50°C, while no energy is lost through unnecessary heating and cooling of the cooling liquid. After the cleaning, the cooling liquid is returned to the cooling unit 5 and the milk line is cooled back to approximately 0°C. The fact that the bundle of lines 19 is designed as an uninterrupted line of constant cross section allows it to be cleaned by pumping an elastic object, such as a foamed plastic ball, with the washing liquid which circulates through the line. This ball exerts a gently rubbing or scraping action on the inner side of the line, so that deposits or undesired growth of bacteria are removed. In this case, the installation is provided with means (not shown) for introducing the ball into the line and for removing it again. Figure 2 diagrammatically depicts an exemplary embodiment of a milking device in which the cooling unit 5 is used. The milking device comprises four milking stalls, each with a set of milking cups 30 which are connected, in a known way, to a milk vessel 31. During the milking, a vacuum is applied in the milk vessel 31 by opening a valve 32, so that the milk vessel is connected to a vacuum line 33 which is connected to a vacuum pump 34. After the milking has ended, the cow which has been milked will leave the milking stall and the milk is pumped out of the milk vessel 31 to a tank 41, for storage until the milk is collected by a milk tanker. Before the milk is stored in the milk tank 41, this milk, which is at a temperature of approximately 38 to 39 °C in the milk vessel 31, is cooled to a temperature of approximately 0 to 2°C in the cooling unit 5. After the milking cups 30 have been removed, the valve 32 is closed and the valve 36 is opened, and the pump 38 is started, so that the milk flows via the nonreturn valve 35, the valve 36 and the collection line 37 to a pump 38. The pump 38 pumps the milk into the cooling unit 5 via a non-return valve 39. Since the volume of the bundle of lines 19 in the cooling unit 5 is greater than the volume of the milk collected in the milk vessel 31, all the milk remains in the cooling unit 5 after it has been pumped through the pump 38. After the milk has remained in the cooling unit 5 for a variable time of, for example, at least 60 seconds, and preferably 90 seconds, it has been sufficiently cooled. After this variable time has ended, the milk from a following milking stall can be pumped to the cooling unit 5. In the situation in which the time required for cooling the milk is approximately 90 seconds, it is on average possible, when using four milking stalls, for the milk from a milk vessel 31 to be pumped to the cooling unit 5 every 6 minutes. The milking device is controlled in such a manner that the milk can remain in the cooling unit 5 for approximately 90 seconds each time and that the entire contents of the milk vessels 31 are successively pumped into the cooling unit 5. The cooling unit 5 is provided in a known way with a cooling installation 40, which comprises, for example, a compressor and a condenser. The condenser may, if appropriate, be air-cooled or water-cooled. Milk quantity meters, as well as filters and the like, may be incorporated in a known way in the line between the milk vessels 31 and the cooling unit 5. To periodically clean the system, the milking cups 30 are connected to sprayers 29, which are provided with washing water via a flushing line 47 and a flushing pump 46. A flushing vessel 44 is filled with hot water via a hot-water source. If appropriate, detergents are added to the water. The temperature of the washing water is, for example, approximately 50°C. The washing water is sprayed into the milking cups 30 via the sprayers 29 and flows to a flushing port 42 via the collection line 37 and the cooling unit 5. The flushing port 42 is designed in such a manner that, during the milking, the milk flows out of line 15 into the milk tank 41. During cleaning, there is a sealed connection between the line 15 and the flushing line 43. An example of a connection of this type is described in patent application NL 1012552, in the name of the same applicant. To prevent the flushing water in the cooling unit 5 from cooling excessively, the cooling liquid is removed from the cooling unit 5 in the manner described above. Also, the bundle of lines 19 is emptied first, in the manner described above, so that no milk remains therein. The drawing shows that one set of milking cups 30 is cleaned via sprayers 29, but it is obvious that there are features which also allow the other milking cups 30 to be cleaned by means of sprayers. If appropriate, it is in this case possible for all the milking systems to be cleaned simultaneously, but also for each system to be cleaned separately while milking can continue uninterrupted in the other milking systems.

Claims: Claims : 1. A milking device comprising milking stalls for automatically milking animals, with a milk vessel (31) for collecting milk in each milking stall, means (38) for pumping the milk which has been collected in a milk vessel (31) to a milk tank (41), and a milk cooler (5) for cooling milk which has been collected in the milk vessel (31) , the milk cooler comprising a vessel (3,11,16) filled with cooling liquid which is cooled by an evaporator (2) and a milk line (19) which is cooled by the cooling liquid, characterized in that the milk cooler is provided with a storage vessel (22) with means for storing the cooling liquid in the storage vessel (22) during the internal cleaning of the milk line (19) . 2. The milking device as claimed in claim 1, characterized in that the internal volume of the milk line (19) which is cooled by the cooling liquid is greater than the volume of the maximum amount of milk which is to be collected from each cow in a milk vessel (31) . 3. The milking device as claimed in claim 1 or 2, characterized in that the milk line (19) lies on a slope in the milk cooler (5) . 4. The milking device as claimed in claim 3, characterized in that the milk line (12) is provided, at the highest point of the milk cooler (5) , with a switchable air inlet (13) . 5. The milking device as claimed in one of the preceding claims, characterized in that the evaporator (2) forms part of a wall (3) of the vessel . 6. The milk line as set forth in one of the preceding claims, characterized in that the milk line (19) in the milk cooler (5) has a cross section which is more or less constant. 7. A method for automatically milking animals, in which the milk is cooled using a milk cooler (5), of which the volume of the milk present in the cooler is greater than the volume of the maximum amount of milk which is to be collected from each cow in a milk vessel (31) , the milk, after the milking, being pumped out of a first milk vessel (31), via the milk cooler (5), to a milk tank (41), and in which method the milk from a following milk vessel (31) is only pumped in after a variable time has elapsed, the variable time being dependent on the time which is required to cool the milk which is present in the milk cooler (5) to the desired temperature. The method as claimed in claim 7, characterized in that the variable time is more than 60 seconds. ?.

Inventors: DESSING JACOBUS PETRUS MARIA, DESSING, JACOBUS, PETRUS, MARIA
Applicants: DESSING JACOBUS PETRUS MARIA, PROLION BV, DESSING, JACOBUS, PETRUS, MARIA, PROLION B.V.
Application year: 2001
Main classification: A01J9
IPC codes: A01J9