Milking device

Abstract

A milking device (1) is provided with: a milking tool; a control unit (11); a milk line (5) for conveying milk from the milking tool to a milk tank (7); a milk filter (8) for filtering milk passing through the milk line (5); and a cleaning device for cleaning the milk filter (8) using a cleaning liquid (42). The milk filter (8) comprises: a housing (23) surrounding a filter (8) volume and having a milk inlet and a milk outlet; and a filter (8) component in the filter (8) volume. The filter (8) component comprises a circumferential plate portion (21) having filter holes (40), and the filter component divides the filter volume into a central inner filter volume (22) and an outer filter volume (24) surrounding the central inner filter volume. The milk filter (8) is configured to be flushed by milk to be filtered from the milk inlet to the milk outlet in use. The cleaning device is configured to clean the milk filter (8) by passing a cleaning liquid (42) through the milk filter (8) in successive pulses in a countercurrent direction, in such a way that: in each pulse, during a first pulse phase, more cleaning liquid (42) is supplied than is discharged; and subsequently, during a second pulse phase, at least an amount of cleaning liquid (42) equal to the amount of cleaning liquid (42) flowing out of the filter (8) volume is supplied. As a result, the amount of cleaning liquid (42) collected in the filter (8) volume rises to a liquid level surrounding at least some of the plurality of holes (40). The next pulse causes the cleaning liquid to collide with this liquid level, thereby improving the cleaning of the filter (8).

Description

Technical Field

[0001] The invention relates to a milking device for milking dairy animals, the milking device being provided with: a milking tool; a control unit for the milking device; a milk line for conveying milk from the milking tool to a milk tank; a milk filter for filtering milk passing through the milk line; and a cleaning device for cleaning the milk filter with a cleaning liquid; wherein the milk filter comprises a housing enclosing a filtration volume and comprising a milk inlet portion having a milk inlet, a milk outlet portion having a milk outlet, and a circumferential outer wall between the milk inlet portion and the milk outlet portion, wherein the milk filter is configured to be flushed in use by milk to be filtered in a first direction, the first direction extending from the milk inlet to the milk outlet, wherein the cleaning device is configured to clean the milk filter by passing the cleaning liquid through the milk filter in a countercurrent direction opposite to the first direction. Background Art

[0002] Milking dairy animals requires filtering of the milk being expressed. In this case, dirt such as feces and litter particles, hair and small cell clusters and debris are filtered out of the milk before it is transferred to the milk tank. Over time, the filters become very dirty. Until now, filter cartridges have been used, which have to be replaced at least three times a day.

[0003] NL C 1037403 discloses a milking device with a stainless steel milk filter which can be cleaned by backwash cleaning. As a result, the filter can continue to be used without replacement. In this way, labor-intensive replacement of the filter sleeve and excessive use of the substrate can already be prevented in an efficient manner. No further details are given on any aspect of the milk filter in this case.

[0004] However, in practice it has been found that such cleaning of milking apparatuses is unsatisfactory, which may lead to a reduction in the quality of the milk and to more rapid clogging of the milk filter, which may result in a standstill of the milking apparatus. This is an undesirable situation which may largely offset these advantages. Summary of the invention

[0005] It is therefore an object of the invention to improve the cleanability, in particular of known milking apparatuses.

[0006] To this end, the present invention provides a milking device, in particular a milking device for milking dairy animals, the milking device is provided with: a milking tool; a control unit for the milking device; a milk line, the milk line is used to convey milk from the milking tool to a milk tank; a milk filter, the milk filter is used to filter the milk passing through the milk line; and a cleaning device, the cleaning device is used to clean the milk filter with a cleaning liquid; wherein the milk filter comprises: a housing, the housing surrounds a filter volume and comprises a milk inlet portion with a milk inlet, a milk outlet portion with a milk outlet, and a circumferential outer wall between the milk inlet portion and the milk outlet portion; a filter component, the filter component is arranged in the filter volume and comprises a circumferential plate portion, the circumferential plate portion comprises a plurality of filter holes, and the filter component divides the filter volume into a central inner filter volume and an outer filter volume The invention relates to a milk filter comprising a central inner filtration volume, the central inner filtration volume being connected to one of a milk inlet and a milk outlet, the outer filtration volume surrounding the central inner filtration volume and being connected to the other of the milk inlet and the milk outlet; wherein the milk filter is configured to be flushed in use by milk to be filtered in a first direction, the first direction extending from the milk inlet to the milk outlet, wherein the cleaning device is configured to clean the milk filter by passing a cleaning liquid through the milk filter in at least two consecutive pulses in a counter-flow direction opposite to the first direction, in such a way that in each pulse: during a first pulse phase, more cleaning liquid is supplied than discharged; and subsequently, during a second pulse phase, at least an amount of cleaning liquid is supplied as much as that flowing out of the filtration volume, such that the amount of cleaning liquid collected in the filtration volume rises to a liquid level surrounding at least a part of the holes of the plurality of holes.

[0007] Without considering that it is subject to a specific explanation or description, the applicant believes that the cleanability of the filter in particular is improved by the present invention, because the amount of cleaning liquid collected in the filter volume forms a kind of wall due to its incompressibility, against which the cleaning liquid of the next pulse hits. This impact forms additional turbulence, thereby increasing the turbulence intensity both in the top layer of the liquid layer formed and in the new cleaning liquid that hits this top layer. These turbulences improve the cleaning action in particular at these turbulent locations. In practice, it has been found that a lot of dirt in milk filters occurs in or on holes located higher up, which may be because these dirt particles and substances float on the surface of the milk in the milk filter. In particular, the known cleaning methods that only use countercurrents do not clean these holes located higher up enough. In particular, by providing a liquid level and a greater turbulence associated with the subsequent pulses, the cleaning of these holes located higher up is greatly improved. Therefore, the focus is on combining the liquid level with the liquid flowing to the liquid level.

[0008] In this case, it should be noted that the first pulse phase of the subsequent pulse succeeds the second pulse phase of the previous pulse. In the second pulse phase, the cleaning liquid has time and opportunity to sink in the filter volume under the action of gravity, and thus forms a liquid level. Then, the new cleaning liquid of the first pulse phase of the next pulse collides with this liquid level. In this case, the second pulse phase must be long enough to allow this liquid level to form. This duration depends in particular on the geometry of the filter volume, but in most cases, one tenth of a second or a few tenths of a second is enough. There is no point in waiting for a longer time, because the cleaning effect of the static liquid is relatively small. Partly for this reason, the duration of the second pulse phase should not be too long either. All of this will be explained in more detail below.

[0009] It should furthermore be noted that the plurality of filter holes does not extend in a plane perpendicular to gravity when the milking device is in use. This is because otherwise all holes would be located either below the liquid level or above the liquid level, which is detrimental to the cleaning action, in particular because the liquid would then not be able to arrange itself efficiently relative to the holes of the filter element. In practice, the plurality of holes will usually extend in a vertical plane, at least in a surface comprising the vertical plane.

[0010] Specific embodiments of the invention are described below and are explained in more detail hereinafter.

[0011] Advantageously, the liquid level is located in the upper half of the plurality of holes, in particular during at least a portion of the second pulse phase. As already mentioned above, it has been found in practice that in particular the upper holes are the dirtiest and (partially for this reason) these upper holes are the most difficult to clean. By selecting and setting the liquid level so that it is located in the upper half of the holes, the holes located at and above the liquid level will be cleaned more thoroughly. In addition, it is possible to determine which holes are difficult to clean based on tests and to select a suitable liquid level based on the test results.

[0012] In a particular embodiment, the cleaning device is configured to change the liquid level between pulses, particularly to raise the liquid level between pulses. This increases the ratio of the holes that are cleaned very thoroughly, because there is greater turbulence at the position of these holes, thereby making the velocity fluctuation greater and therefore making the fluctuation of the local wall shear stress greater. In this way, in principle, the entire filter element can be cleaned more thoroughly. The liquid level does not necessarily change between every two pulses. Therefore, for example, the same liquid level can also be maintained in two or more pulses, and then the liquid level is changed. The liquid level can also be changed in different small steps, or even alternately the liquid level is raised and reduced. Therefore, for example, the most difficult-to-clean part of the hole / filter element can be cleaned with the most pulses.

[0013] In an embodiment, the pulses have a frequency greater than 0.5 Hz. Advantageously, the second pulse phase is shorter than 1 second, more advantageously at most 0.5 seconds. In this case, the usual rounding rules apply. The inventors have found that a pulsed flow of cleaning liquid is more efficient than a constant flow of cleaning liquid, and that the pulses themselves create additional turbulence near the wall, so that providing a greater number of pulses in a short period of time may be advantageous.

[0014] The number of pulses during the cleaning operation is not particularly limited. In particular, the number of pulses is between 2 and 20, more particularly between 10 and 20. This is a good compromise between the duration of the cleaning operation and the use of water and the cleaning effect.

[0015] In an embodiment, the milking device comprises a pressure device configured to provide a pressurized cleaning liquid to the milk filter. The pressure device is not particularly limited, but the pressure device advantageously comprises an accumulator for the cleaning liquid. By providing a pressurized cleaning liquid, a stronger turbulence can be formed in the liquid, thereby making the cleaning effect better.

[0016] Here, it should be noted that the cleaning liquid can be supplied via the milk outlet and discharged via the milk inlet, and in this case, the cleaning liquid is allowed to follow the same path as the milk. In some cases, it may be advantageous that the cleaning liquid flows (almost) only to the milk filter, for which a separate supply connection is provided near or at the milk outlet, and a discharge connection leading to a collection container or a sewer is provided at or near the milk inlet. Thus, the cleaning liquid can act and the impact on the rest of the milking device (e.g., the impact on the temperature of the pipeline during cleaning) is negligible. This can also provide optimal control of the cleaning liquid because the path to be traveled is very short. In this case, the cleaning liquid can be circulated, collected for subsequent reuse, or discharged to a sewer, etc. In addition, a valve device (particularly a three-way valve) that can control the flow of the cleaning liquid (more particularly, separate the flow of the cleaning liquid from the previous or subsequent milk flow) can also be provided at the supply connection and / or the discharge connection.

[0017] In an embodiment, the milking device comprises a compressed air supply port for supplying compressed air to the cleaning liquid before the cleaning liquid enters the filter volume. Supplying compressed air to the cleaning liquid flow further increases the turbulence intensity, thereby further improving the cleaning. The compressed air supply port can be arranged on or near the supply connection of the cleaning liquid, but is not limited thereto.

[0018] Here, it should be noted that, in particular when using compressed air, it is useful not to make the duration of the second pulse phase too long and to advantageously limit it to less than 3 / 4 seconds, more advantageously to at most 1 / 2 seconds, but this duration slightly depends on the geometry of the milk filter. The inventors believe that a longer duration (such as 3 / 4 seconds) leads to the formation of large bubbles in the cleaning liquid collected in the filter volume by the introduced compressed air. As a result, the air / liquid mixture as a whole becomes compressible and therefore less active than a fixed liquid surface or "wall" against which the new pulsed cleaning liquid can hit to generate additional turbulence. In the case of shorter times (such as at most 1 / 2 seconds), the formation of bubbles is greatly reduced to small bubbles, which have been found to have a greatly reduced effect on the compressibility and thus form a turbulent structure. Furthermore, it should be noted here that "cleaning liquid" is also understood to mean liquid mixed with compressed air.

[0019] In an embodiment, the milking device comprises: an inlet valve device, which can be controlled by the control unit to control the supply amount of cleaning liquid; and / or an outlet valve device, which can be controlled by the control unit to control the discharge amount of cleaning liquid. Then, the inlet valve device is for example arranged in, on or near the milk discharge port, and the outlet valve device is arranged in, on or near the milk supply port, but it is also possible to arrange the corresponding valve device in a pipeline section intended only for cleaning liquid, such as in or near the cleaning liquid reservoir. The inlet valve device can be configured to control the supply amount of pulsed cleaning liquid and comprises, for example, an electromagnetically actuated or otherwise actuatable valve operated by the control unit. It may be sufficient to fully open the valve for a desired time and then close it again. The valve can also have a controllable channel, which can be adjusted by the control unit. For example, the control unit can open the inlet valve device to a certain extent so that during the first pulse phase, the cleaning liquid supplied to the filter volume is greater than the cleaning liquid discharged from the filter volume, and the inlet valve device can be closed to a sufficient extent so that during the second pulse phase, the supply is less than the discharge. All of this obviously depends on the geometry of the discharge port, but in practice can be easily controlled and adjusted, for example, using a proportional valve. Alternatively or in addition, the discharge can be controlled accordingly by means of an optional outlet valve device, now by throttling the discharge to a certain extent so that the discharge is less than the supply in the first pulse phase (so at this time, the supply may not be zero), and so that the discharge is at least equal to the supply during the second pulse phase (the supply can be zero in this case). Obviously, the combination of two valve devices can provide more control over the supply and discharge of the cleaning liquid.

[0020] It is important to note that not allowing too much cleaning liquid to be discharged from the filter volume may be sufficient to ensure that the net supply can be achieved to be greater than zero during the first pulse phase and less than or equal to zero during the second pulse phase while still retaining sufficient available liquid level when using only the inlet valve device. As long as the liquid level in the filter volume remains available for a time, such as in the order of 0.1 seconds to at most 3 / 4 seconds or less (e.g. at most 0.5 seconds), the enhanced turbulence effect can be maintained around the wall at the liquid level above the bottom end of the filter element. Advantageously, these pulses do not last too long. Therefore, short pulses that follow each other relatively quickly produce local wall shear stress peaks, which are conducive to spreading dirt. In practice, it is relatively easy to reduce the amount discharged from the filter volume to achieve this purpose.

[0021] Furthermore, it should be noted here that the expression "liquid level" does not necessarily refer to a time-independent level. The liquid level can vary not only between pulses (as already mentioned above) but also during a pulse, as long as there is a more or less recognizable cleaning liquid level during the second pulse phase. In this context, the initial level can also be referred to as "liquid level".

[0022] The change in the liquid level between the pulses can be achieved by changing the balance between the supply and discharge of the cleaning liquid. As already described above, in this case, the inlet valve device and / or the outlet valve device can be used in such a way that the opening time of these valve devices is changed. For example, it is also possible to change only the duration of the closure of these valve devices while the passage remains unchanged, so that the pulses follow each other more quickly. This can also increase the amount of cleaning liquid in the filter volume and thus change the liquid level. Optional combinations with other alternatives are not excluded.

[0023] In an embodiment, the inner filter volume is connected to the milk outlet. This means that the milk flows into the outer filter volume concentrically outward, then through the filter element and finally out of the milk filter via the inner filter volume and the milk outlet. As a result, foreign material that has been filtered out will remain on the outside of the filter element. When the milk filter is subsequently cleaned in countercurrent, the cleaning liquid will flow from the inside to the outside. Therefore, foreign material will then be discharged more efficiently than in the reverse direction, but this is not excluded.

[0024] In particular, the outer wall of the housing of the milk filter is transparent. In this way, the filter element can be viewed from the outside in order to see whether it has become (too) dirty and to visually assess whether the filter element has been cleaned well enough. Obviously, the outer wall can also be non-transparent, for example made completely of metal or plastic.

[0025] In an attractive embodiment, the housing is substantially cylindrical and the filter element is a metal plate concentric with the outer wall. The shape of the housing and the filter element itself is not particularly limited, but advantageously the housing and the filter element are concentric so that good control of the flow of the cleaning liquid through the housing and through the filter element can be ensured. Furthermore, the cylindrical shape of the filter element contributes to the cleanability of the unit, since corners where the flow is much slower and the velocity fluctuations are smaller, which are difficult to clean, are thereby prevented.

[0026] Advantageously, the holes in the filter element are produced by means of a laser. The laser forms a substantially conical hole. It may be useful to have the smallest diameter of the hole facing the dirty side (that is to say the side on which the milk flows in) and therefore the largest diameter of the hole facing the outflow side. As a result, foreign material in the milk to be filtered out will be retained by the filter element, but will not get stuck in the gradually narrowing holes. If the cleaning liquid then passes through the filter element in the countercurrent direction, this will be able to better remove any foreign material that is still present due to the gradual narrowing of the holes in the countercurrent direction, because the flow rate and the optional turbulence intensity will increase with the narrowing holes. In practice, the size of these holes is largely determined by the properties of the milk. An example of the smallest usable diameter is about 60 µm, while the diameter towards the other side is, for example, up to 120 µm. Obviously, other sizes are also possible.

[0027] A particular embodiment comprises a core in the inner filter volume, which is concentric with the outer wall and therefore also with the filter element. This core serves to prevent that at the start of cleaning there is still too much milk in the filter, which would be lost, and to prevent that the filter volume available for the cleaning liquid is too large, which could result in a too low velocity of the cleaning liquid. In particular, this core ensures that the net available conduit for the cleaning liquid becomes thinner, thereby reducing the water consumption during cleaning. Advantageously, the core extends integrally along the plurality of holes, so that the flow velocity of the cleaning liquid is increased along all of these holes.

[0028] In particular, the radial distance between the outer periphery of the core and the inner surface of the filter element is at most 5 mm, for example between 2 mm and 3 mm. In addition, in particular, the radial distance between the outer periphery of the filter element and the inner periphery of the outer wall is at most 5 mm, for example between 2 mm and 3 mm. This provides attractive flow speeds and associated turbulence intensity in the filter volume. Obviously, other sizes and distances are not excluded, such as in the case where the milk of a larger milking device must be filtered, a larger filter surface is required accordingly. More particularly, the two distances are roughly equal, that is to say within 15%. Therefore, the filter element will be in the center of the pipeline formed almost between the core and the outer wall, where an overall favorable flow speed and turbulence intensity can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The invention will be explained in more detail below based on some non-limiting exemplary embodiments and the accompanying drawings and their description, in which:

[0030] Figure 1 shows a schematic view of a milking device according to the invention,

[0031] Figure 2 shows a schematic cross-sectional view of a milk filter 8 with various connections,

[0032] Fig. 3a shows a schematic cross-sectional view of the bottom part of the milk filter under a first pulse, and Fig. 3b shows a schematic cross-sectional view of the bottom part of the milk filter under a second pulse, and

[0033] FIG. 4 a gives an example of the cleaning liquid flow over time, and FIG. 4 b shows the associated liquid level in the milk filter. DETAILED DESCRIPTION

[0034] Figure 1 A schematic view of a milking device 1 according to the invention is shown, comprising a milking cup 2, a milking measuring glass 3, a vacuum pump 4, milk lines 5-1, 5-2, 5-3, a milk pump 6, a milk tank 7, and a milk filter, generally indicated by reference numeral 8, with a schematic cleaning liquid connection 9 and a schematic drain connection 10. Reference numeral 11 denotes a control unit, and reference numeral 12 denotes an optional milking robot with a robot arm 13. Furthermore, reference numeral 100 denotes a dairy animal with a teat 101.

[0035] Here, the milking device 1 is a fully automatic milking robot system, but the present invention can also be applied to conventional milking systems. The milking robot 12 of the milking device 1 can attach the milking tool (here the milking cup 2) to the teat 101 of the dairy animal by its robot arm 13 under the control of the control unit 11. For this purpose, components known per se (such as a teat detection system) are provided, however, these components are not relevant to the present invention and are therefore not shown here and will not be explained in detail.

[0036] By attaching a milking cup to the teat 101 and in particular using a vacuum pump 4, the milking device is able to extract milk, which eventually enters a milk measuring glass 3. From this milk measuring glass, the milk can be transferred to a milk tank 7 by means of a milk pump 6, in particular at the end of a milking operation, via a milk line comprising a section 5-1, a section 5-2 and a section 5-3, which are also denoted together below with the reference numeral "5". In the case of very large farms, the fixed milk tank 7 can also be replaced by a tank of a tanker.

[0037] The expressed milk is filtered by means of a milk filter 8 provided in the milk line 5. This filter serves to filter foreign material (such as hair, sand, bedding material etc.) out of the milk. In this case, in the example shown, the milk flows through the milk filter from bottom to top. Inevitably, the milk filter will gradually become dirtier and regular cleaning of the milk filter will therefore be required. According to the invention, the cleaning takes place during each major cleaning service of the entire milking apparatus, as will be explained in more detail below. Furthermore, a pressure drop meter or the like (not shown here) may also be provided, which measures the pressure drop over the milk filter 8 and sends a signal to the control unit 11 when this pressure drop exceeds a threshold value, so that the milk filter 8 is temporarily serviced for cleaning.

[0038] For example, cleaning can be performed by passing the cleaning liquid through the filter in the same direction as the milk, that is to say from the teat cup 2, via the milk line 5, through the milk filter 8 to the milk tank 7. Hot, acidic or alkaline liquids can dissolve, for example, fat residues, protein residues or calcium residues with high efficiency. Less advantageously, hair, sand etc. are further pressed against the filter without being removed or dissolved. However, a counter-current cleaning operation can be performed in order to remedy this, in which the cleaning liquid is supplied in the reverse direction, in particular from the cleaning liquid supply 9, via the milk filter 8 to the cleaning liquid discharge 10 (e.g. a sewer).

[0039] All of these in Figure 2 1, which shows a schematic cross-sectional view of a milk filter 8 with various connections. In this case, similar parts are indicated by the same reference numerals throughout the drawings.

[0040] The milk filter 8 comprises a housing 23 having a first end 15 with a milk supply opening 18, a cylindrical portion 16, and a second end 17 with a milk discharge opening 19. A core 20 and a filter plate 21 comprising holes are accommodated in a filtration volume in the housing 23 and divide the filtration volume into a first volume portion or outer filtration volume 24 and a second volume portion or inner filtration volume 22.

[0041] The first three-way valve 25 may be connected to the cleaning liquid supply port 9 from a holder 29 or the like, a compressed air line 26 which may be closed by a valve 27, and a compressed air generator 28. The second three-way valve 30 may connect the cleaning liquid discharge port 10 to a sewer 31 or the like.

[0042] also, Figure 2 The path of the milk during milking is shown with a single arrow, and the path of the cleaning liquid during the backflow cleaning operation is shown with a double arrow.

[0043] The housing 23 can have any desired cylindrical shape, with a first end 15 and a second end 17, which are narrowed towards the supply opening and the discharge opening, respectively. It should be noted that the supply opening or the discharge opening does not have to be centered and / or arranged in the longitudinal direction. Therefore, the supply opening or the discharge opening can also be arranged tangentially in a cyclonic manner. In this case, the housing can, for example, have a completely or partially transparent cylindrical portion 16, so that the filter plate 21 can be inspected without removing the filter 8. Obviously, non-transparent materials (such as metals) are also possible.

[0044] The core 20, in this case a cylindrical core, is provided so as not to make the ducts for the milk and the cleaning liquid (formed respectively by the first volume 24 and the second volume 22) unnecessarily large, so as not to make the flow rate, in particular of the cleaning liquid, unnecessarily and undesirably low. It should be noted that in practice it is desirable that the filter plate 21 has a large surface area, which filter plate obviously contains a proportional number of holes, so as to hinder the flow of milk as little as possible.

[0045] In this case, the filter plate 21 is a cylindrical metal plate containing a large number of holes. Although the plate does not have to be cylindrical, a cylindrical plate is advantageous for uniform filtering and cleaning due to its symmetry. The holes are not shown separately. For example, the diameter of the holes is advantageously between 60 μm and 120 μm, especially based on the size of the fat globules in the milk. For example, the holes are produced by a laser so that the holes are advantageously tapered from the milk supply side to the milk discharge side to further promote dirt dispersion during the countercurrent cleaning operation. The number of holes is preferably as large as possible, and in one embodiment, the number of holes is at least several hundred thousand, such as one million.

[0046] One possible function of the milk filter is as follows. During milking, milk flows from the milk line section 5-2 from below through the milk supply opening 18 into the first end 15 of the milk filter 8. In this case, the milk eventually enters the first volume 24 and then flows through the holes of the filter plate 21 to the second volume 22, leaving foreign material behind the filter plate 21. Thereafter, the milk is forced to proceed via the second end 17 and will leave the milk filter 8 via the milk discharge opening 19 in order to then be pumped to a milk tank (not shown here) via the first three-way valve 25 and the milk line section 5-3.

[0047] If a main cleaning service of the milking device is performed after a milking operation, the cleaning liquid will be able to pass through the milk filter 8 along at least a portion of the same path. However, it is advantageous to start a countercurrent cleaning operation in order to remove at least a portion of the foreign material that has been filtered out of the milk filter 8, so that this portion will no longer further hinder the flow of the cleaning liquid and in particular make the filter plate 21 easier to clean. For such a countercurrent cleaning operation, for example, a cleaning liquid (such as water) can be supplied by switching the first three-way valve 25 in such a way that it connects the cleaning liquid supply port 9 and the milk filter 8, and then the cleaning liquid is supplied from the supply 29, which can also be a water pipe. If desired, compressed air from a compressed air generator 28 can be added via a compressed air line 26 by switching a valve 27. As known per se, compressed air can contribute to a greater turbulence intensity of the cleaning liquid and thus to a better (mechanical) cleaning operation of the milk filter 8. Incidentally, the supply 29 can also be configured to provide pressurized cleaning liquid. For example, the supply 29 comprises an accumulator (not shown) by means of which a pressure can be built up which will slowly decrease as the cleaning liquid is dispensed, in a manner similar to an expansion vessel in a central heating installation. A pump may also be provided, or gravity may simply be provided by placing the supply at the desired height.

[0048] The cleaning liquid to be supplied in the backflow enters the milk filter 8 via the milk discharge opening 19 of the second end 17 and will flush the milk filter 8 through the second volume portion 22, the filter plate 21, the first end 15 and the milk supply opening 18 and carry away foreign material in the process. The cleaning liquid can then flow via the milk line portion 5-2 and the second three-way valve that has just been switched, via the cleaning liquid discharge 10 to a sewer or a collecting container. As a result, dirty cleaning water does not have to flow through the rest of the milking apparatus.

[0049] In this case, it should be noted that during milking, the milk will fill the filter volume (portion 22 and portion 24) from below. In theory, any part of the milk floating on top will then also end up entering mainly into the upper holes of the filter plate 21. Furthermore, it has been found that in the case of a milk filter 8 of standard construction, the cleaning action, in particular for these upper holes, is often insufficient. The solution according to the invention will be explained below based on FIG. 3 and other figures.

[0050] Fig. 3a shows a schematic cross-sectional view of the bottom part of the milk filter under a first pulse, and Fig. 3b shows a schematic cross-sectional view of the bottom part of the milk filter under a second pulse.

[0051] Fig. 3a shows the bottom part of the milk filter 8, which comprises the outer wall 23, the filter plate 21 with holes 40 and the bottom wall 41, the core 20, and the first volume part 24 and the second volume part 22. The bottom part contains cleaning liquid 42 up to the level h0. Furthermore, the incoming flow of the first pulse of cleaning liquid plus compressed air 43 is schematically shown. The arrows indicate the flow direction therein.

[0052] New fresh cleaning liquid enters from above together with compressed air 43, initially via the inner filter volume or second volume 22. This fresh cleaning liquid also almost immediately enters the outer filter volume or first volume 24 through the holes 40. At the bottom, the cleaning liquid flow including the compressed air 23 hits the bottom wall 41 of the filter plate 21 and the previously collected amount of cleaning liquid 42, which is indicated by the reverse hatching and reaches the liquid level h0. The fresh cleaning liquid 43 hits the collected cleaning liquid 42 and / or the inner wall 41 at this position (that is to say at the liquid level h0), as a result of which a lot of turbulence occurs both in the fresh cleaning liquid 43 and in the upper layer of the previously collected cleaning liquid 42, even in the case of local counterflow. This is schematically shown by the rotating arrows. Due to these turbulences, the cleaning liquid will have a greater cleaning effect on the holes 40 of the filter plate 21 at this position. This is probably why the bottom part is usually cleaned very thoroughly in the case of using milk filters known in the prior art. It should be noted that turbulence already exists in or around the filter without impact with the liquid surface. For the sake of clarity, these turbulences are not shown.

[0053] FIG3 b shows a schematic cross-sectional view of the bottom part of the milk filter during the second pulse. In this case, it should be noted that at the end of the previous pulse (here referred to as the first pulse for convenience), a certain amount of cleaning liquid 42 ′ up to the level h1 has been collected in the milk filter 8. This cleaning liquid can be collected because, in net terms, less liquid can flow out than enter. In this case, for example, the cleaning liquid can be completely or partially closed during the first pulse. Figure 2 The valve 30 in the embodiment of the invention can also be made to flow a cleaning liquid greater than the discharge capacity, so that the liquid level in the milk filter will rise during the first pulse in both cases.

[0054] If a second pulse of cleaning liquid is then provided, as in the case of FIG. 3 b here, the cleaning liquid will not collide with the bottom wall 41 of the filter plate 21, but will impact the previously collected cleaning liquid 42 at the liquid level h. This means that turbulence will now be generated around this liquid level h, and subsequently, turbulence will be generated at a corresponding higher liquid level under a later pulse. This in turn means that the holes at the liquid level h and subsequently the holes at the corresponding higher liquid level will be thoroughly cleaned.

[0055] Obviously, the subsequent pulses can in each case at a higher liquid level provide good cleaning of the filter plate 21. It is also possible to clean higher parts of the filter plate 21 by generating more pulses starting at a higher liquid level at these higher parts.

[0056] To this end, as already briefly mentioned above, the three-way valve 30 or any other valve in the discharge of the cleaning liquid, or in the supply of the cleaning liquid, or in a combination thereof, is controlled by the control unit in such a way that the desired liquid level in the milk filter is reached at the end of the discharge between two pulses. Thus, the passage of a possible valve in the discharge, the flow rate of the cleaning liquid, as well as the pulse time and the discharge time etc. are available as variables.

[0057] Figure 4a gives an example of the cleaning liquid flow over time. Figure 4b gives the associated liquid level h in the milk filter.

[0058] In this example, six equal pulses of cleaning liquid are provided, wherein the duration is t and the repetition rate is T, i.e. the frequency is 1 / T. For example, the experimental values ​​are: t = 0.5 s and T = 0.75 s, but of course they can vary. In practice, it has been found that in this case it is particularly advantageous to keep the discharge time (i.e. the duration between two pulses) short, such as 0.25 seconds. This is particularly applicable to the case where compressed air injection occurs in order to generate peak shear stresses in the wall, because the injected air does not have time to form large air bubbles in this short time, and in this case the effect of the incompressibility of the cleaning liquid will be lost.

[0059] In this case, the number of pulses is 7, but in principle any desired number greater than or equal to 2 is possible. Here, the pulses are all equal, but this is not mandatory and, for example, the pulse duration t can also be increased or the flow rate during the pulses can also be increased in order to increase the liquid level in the milk filter at the end of the discharge time or, if desired, to lower it or at least bring it to the desired level. Furthermore, it is not mandatory that the level h of the cleaning liquid in the milk filter at the end of the discharge time be increased between pulses. As in the case of the example shown, it is also possible in each case to increase the liquid level h after the first x pulses to a maximum liquid level h 最大 (that is to say the level reached when the milk filter was filled to the maximum extent during the previous pulse after the discharge in the discharge time has taken place), and then in each case completely filling the milk filter during the remaining pulses and allowing it to drop to the maximum level h 最大 In this way, the upper part of the milk filter can be cleaned very thoroughly.

[0060] The illustrated exemplary embodiments are not intended to be limiting in any way. Rather, the scope of protection of the present invention is determined by the appended claims.

Claims

1. A milking device for milking dairy animals, the milking device comprising: - milking tools, - a control unit for said milking device, - a milk line for conveying milk from the milking tool to a milk tank, - a milk filter for filtering the milk passing through the milk line, and - a cleaning device for cleaning the milk filter using a cleaning liquid, in, The milk filter comprises: - a housing enclosing the filtration volume and comprising a milk inlet portion with a milk inlet, a milk outlet portion with a milk outlet, and a circumferential outer wall between the milk inlet portion and the milk outlet portion, - a filter member, which is arranged in the filter volume and comprises a circumferential plate portion, which comprises a plurality of filter holes and which divides the filter volume into a central inner filter volume, which is connected to one of the milk inlet and the milk outlet, and an outer filter volume, which surrounds the central inner filter volume and is connected to the other of the milk inlet and the milk outlet, wherein the milk filter is configured to be flushed, in use, by milk to be filtered in a first direction, the first direction extending from the milk inlet to the milk outlet, wherein the cleaning device is configured to clean the milk filter by passing a cleaning liquid through the milk filter in at least two consecutive pulses in a counter-flow direction opposite to the first direction, in such a way that in each pulse: - during the first pulse phase, more cleaning fluid is supplied than is discharged, and - Subsequently, during a second pulse phase, at least an amount of cleaning liquid equal to that flowing out of the filtration volume is supplied so that the amount of cleaning liquid collected in the filtration volume rises to a liquid level surrounding at least a portion of the plurality of filtration holes.

2. The milking apparatus according to claim 1, wherein: The liquid level is located in the upper half of the plurality of filter holes.

3. The milking device according to claim 1 or 2, wherein: The cleaning device is configured to vary the liquid level between pulses.

4. The milking apparatus according to claim 3, wherein: The cleaning device is configured to raise the liquid level between pulses.

5. The milking device according to claim 1 or 2, wherein: The frequency of the pulses is higher than 0.5 Hz.

6. The milking device according to claim 1 or 2, wherein: The second pulse phase is shorter than 1 second.

7. The milking apparatus according to claim 6, wherein: The second pulse phase is at most 0.5 seconds.

8. The milking apparatus according to claim 1 or 2, wherein: The number of pulses is between 2 and 20.

9. The milking apparatus according to claim 1 or 2, wherein: The milking device comprises a pressure device configured to provide a pressurized cleaning fluid to the milk filter.

10. The milking apparatus according to claim 9, wherein: The pressure device comprises an accumulator for the cleaning fluid.

11. The milking apparatus according to claim 1 or 2, wherein: The milking device comprises a compressed air supply port for supplying compressed air to the cleaning fluid before the cleaning fluid enters the filtration volume.

12. The milking apparatus according to claim 1 or 2, wherein: The milking device comprises an inlet valve device and / or an outlet valve device, wherein the inlet valve device can be controlled by the control unit to control the supply amount of the cleaning liquid; and the outlet valve device can be controlled by the control unit to control the discharge amount of the cleaning liquid.

13. The milking apparatus according to claim 1 or 2, wherein: The inner filtration volume is connected to the milk outlet.

14. A milking apparatus as claimed in claim 13, wherein: The outer wall is transparent.

15. The milking apparatus according to claim 1 or 2, wherein: The housing is generally cylindrical and wherein the filter element is a metal plate concentric with the outer wall.

16. The milking apparatus according to claim 1 or 2, wherein: The milking device comprises a core in the inner filtration volume, the core being concentric with the outer wall.

17. A milking apparatus as claimed in claim 16, wherein: The core extends along the entirety of the plurality of filter holes.

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