MILKING DEVICE PROVIDED WITH A MILK FILTER

Abstract

An automatically cleanable milk filter includes a cylindrical housing with an outer wall, a first end with a first liquid connection, and above a second end with a second liquid connection. A concentric cylindrical filter part and a cylindrical core placed concentrically within the filter part are accommodated in the housing. The filter part includes wire having a tapered cross-sectional profile in a spiral shape or as a series of parallel rings or rods, and a frame for keeping them spaced apart, thereby forming a plurality of filter openings. The filter part divides the filter volume into a first volume part which is directly connected to the first liquid connection, and a second volume part which is directly connected to the second liquid connection. The second volume part includes a cylindrical part, as well as a top part which narrows at a transition to the second liquid connection.

Claims

1. An automatically cleanable milk filter for filtering milk that is obtained in a milking device for milking dairy animals, comprising: a cylindrical housing with a longitudinal direction and with a cylindrical outer wall, a first end with a first liquid connection, and a second end with a second liquid connection, wherein, during use of the filter, the second end is situated above the first end; a substantially concentric cylindrical filter part containing a plurality of filter openings with a smallest diameter of between 60 and 100 ?m; and a cylindrical core placed concentrically within the filter part, the filter part and the cylindrical core being accommodated in the housing, the filter part comprising wire with a unilaterally tapering cross-sectional profile and a frame, which wire is provided in a spiral shape with a plurality of windings or in a series of individual parallel rings or rods, wherein the frame is configured to keep the windings or the rings or the rods at a mutual distance, as a result of which the plurality of filter openings is provided between the windings or the rings or the rods, wherein the filter part divides the filter volume into a first volume part which is directly connected to the first liquid connection, and a second volume part which is directly connected to the second liquid connection, wherein the second volume part comprises a cylindrical part, as well as a top part which narrows at a transition to the second liquid connection, wherein said cylindrical part, viewed in a direction towards the second liquid connection, extends at least a predetermined distance beyond the plurality of filter openings in the filter part, and wherein said first volume part, viewed in a direction towards the second liquid connection, does not extend beyond the filter part.

2. The milk filter as claimed in claim 1, wherein the second volume part has a radial thickness, wherein said predetermined distance is at least ten times said radial thickness.

3. The milk filter as claimed in claim 1, wherein an average radial thickness of the first volume part and an average radial thickness of the second volume part are virtually equal at a location of the plurality of filter openings.

4. A milking device for milking dairy animals, comprising: milking means for obtaining milk from the dairy animals, a milk tank for storing of obtained milk, a milk line for transporting the obtained milk from the milking means to the milk tank, and an automatically cleanable milk filter provided in the milk line for filtering milk, as claimed in claim 1, a cleaning device for the milk filter, a control unit for controlling the milking device, wherein the cleaning device comprises a cleaning liquid supply which is controllable by the control unit and has an inlet valve, and which is connectable to the second liquid connection of the milk filter, and a cleaning liquid discharge with an outlet valve which is controllable by the control unit, and which is connectable to the first liquid connection, wherein the cleaning device is configured to clean the milk filter under control of the control unit by passing cleaning liquid through the milk filter in countercurrent via the cleaning liquid supply, and to discharge the cleaning liquid via the cleaning liquid discharge.

5. The milking device as claimed in claim 5, wherein the cleaning supply is configured to supply the cleaning liquid to the milk filter in pulses during a cleansing.

6. The milking device as claimed in claim 4, further comprising a compressed air connection which is controllable by the control unit and is configured to supply air at excess pressure to the cleaning liquid before the second supply of liquid.

7. The milk filter as claimed in claim 1, wherein said first volume part, viewed in a direction towards the second liquid connection, does not extend beyond a highest filter opening of the filter part.

Description

[0035] FIG. 1 shows a diagrammatic view of a milking device according to the invention,

[0036] FIG. 2 shows a diagrammatic sectional view of the milk filter 8 with various connections,

[0037] FIG. 3 diagrammatically shows a detail of the milk filter 8, in particular of an upper part thereof,

[0038] FIG. 4 diagrammatically shows a perspective view of a filter part, and

[0039] FIG. 5 shows a diagrammatic sectional view of the filter part from FIG. 4.

[0040] FIG. 1 shows a diagrammatic view of a milking device 1 according to the invention, comprising a milking cup 2, a milking glass 3, a vacuum pump 4, a milk line 5-1, 5-2, 5-3, a milk pump 6, a milk tank 7, and a milk filter which is denoted overall by reference numeral 8, with a diagrammatic cleaning liquid connection 9 and a diagrammatic discharge connection 10. With 11 a control unit is indicated and with 12 an optional milking robot with a robot arm 13 is indicated. With 100 furthermore a dairy animal, with teats 101, is indicated.

[0041] Here, the milking device 1 is a fully automatic milking robot system, but the invention can also be applied in conventional milking systems. By means of its robot arm 13, the milking robot 12 of the milking device 1 can attach milking means, here a milking cup 2, to a teat 101 of the dairy animal under the control of the control unit 11. To this end, components which are known per se, such as a teat-detecting system, are provided, which, however, do not relate to the invention and are therefore not illustrated here and will not be explained in any more detail.

[0042] By means of the milking cup attached to the teat 101 and using, inter alia, the vacuum pump 4, the milking device is able to extract milk, which ends up in the milking glass 3. From there, the milk can be passed to the milk tank 7 by means of the milk pump 6 via the milk line, comprising parts 5-1, 5-2 and 5-3, together also denoted below by the number 5, in particular at the end of a milking operation. In the case of very large farms, the fixed milk tank 7 may also be replaced by the tank of a tanker.

[0043] The milked milk is filtered by means of the milk filter 8 provided in the milk line 5. This filter serves to filter foreign material, such as hairs, sand, bedding material and the like, from the milk. In this case, the milk flows through the milk filter from the bottom to the top in the illustrated example. Inevitably, the milk filter will gradually become more soiled and will therefore have to be cleaned regularly. According to the invention, this takes place at every main cleaning service of the entire milking device, as will be explained in more detail below. Furthermore, a pressure-drop meter or the like may also be provided (not shown here), which measures the pressure drop across the milk filter 8 and which emits a signal to the control unit 11 if the pressure drop exceeds a threshold value in order to subject the milk filter 8 to an interim cleaning service.

[0044] Cleansing may be performed, for example, by passing cleaning liquid through the filter in the same direction as the milk, that is to say from the milking cups 2 and via the milk line 5 through the milk filter 8 to the milk tank 7. The hot, acid or alkaline liquids to be used may efficiently dissolve, for example, fat residues, protein residues or calcium residues. Less advantageous is the fact that hairs, sand and the like are pressed further against the filter without being removed or dissolved. However, a counterflow cleansing may be performed in order to remedy this, in which cleaning liquid is supplied in the reverse direction, in particular from cleaning liquid supply 9, via the milk filter 8 to cleaning liquid-discharge 10, such as a sewer.

[0045] All this is explained in more detail in FIG. 2, which shows a diagrammatic sectional view of the milk filter 8 with various connections. In this case, similar components are denoted by the same reference numerals throughout the drawing.

[0046] The milk filter 8 comprises a housing 23 with a first end 15 with a milk supply opening 18, a cylindrical part 16 and a second end 17 with a milk discharge opening 19. A core 20 and a filter part 21 comprising filter openings are accommodated in the filter volume in the housing 23 and divide this into a first volume part 24 and a second volume part 22.

[0047] A first three-way valve 25 is connectable to the cleaning liquid-supply 9 from a holder 29 or the like and to a compressed air line 26 which is closable by a valve 27, to a compressed air generator 28. A second three-way valve 30 is connectable to the cleaning liquid discharge 10 to a sewer 31 or the like.

[0048] Furthermore, FIG. 2 shows the path of the milk during milking with a few single arrows, and the path of the cleaning liquid during a countercurrent cleansing with double arrows.

[0049] The housing 23 may have any desired cylindrical shape, with a first end 15 and a second end 17 which both narrow towards a supply and discharge, respectively. It should be noted that this supply or discharge does not necessarily have to be provided centrally and/or in the longitudinal direction. Thus, it may also be provided tangentially, in the manner of a kind of cyclone. In this case, the housing may have, for example, an entirely or partly transparent cylindrical part 16, so that the filter part 21 may be inspected without having to remove the filter 8. Obviously, non-transparent materials, such as metals, are also possible.

[0050] The core 20 is provided in order to make the duct for the milk and the cleaning liquids, which is formed by the first and the second volume part 24 and 22, respectively, not unnecessarily large, which would render the flow velocity of, in particular, the cleaning liquid unnecessarily and undesirably low. It should be noted that a large surface area of the filter part 21 is indeed desirable, in order to have space for a large number of filter openings and therefore to impede the flow of the milk as little as possible.

[0051] In this case, the filter part 21 is a cylindrical metal plate containing a large number of filter openings. Although it is not imperative for the part 21 to be cylindrical, it has advantages if it is, with regard to an even filter action and cleaning, due to symmetry.

[0052] The filter openings are not illustrated individually. The smallest dimension is advantageously between 60 between 60 and 80, increasing to for example 120 ?m, for example on the basis of, in particular, the dimensions of the fat globules in the milk. The filter openings taper, advantageously from the milk supply side to the milk discharge side, in order to further assist in detaching dirt during counterflow cleansing. The number of filter openings is preferably as large as possible and, in one embodiment, is at least a few hundred thousand, such as a few hundred.

[0053] One possible action of the milk filter is as follows. During milking, milk flows from the milk line part 5-2, via the milk inlet opening 18, into the first end 15 of the milk filter 8 from below. In this case, the milk ends up in the first volume part 24 and then flows to the second volume part 22 via the filter openings of the filter part 21, foreign material remaining behind on the filter part 21. Thereafter, the milk is forced onwards via the second end 17 and will leave the milk filter 8 via milk discharge opening 19, in order to then be pumped to the milk tank (not shown here) via the first three-way valve 25 and the milk line part 5-3.

[0054] If a main cleaning service of the milking device is performed after a milking operation, cleaning liquid will be able to follow at least a part of the same path through the milk filter 8. However, it is advantageous to start with a countercurrent cleansing in order to already remove at least part of the filtered-out foreign material from the milk filter 8, so that this will not impede the flow of cleaning liquid any further, and to render, in particular, the filter part 21 more easily cleanable. For this countercurrent cleansing, for example, cleaning liquid, such as water, may be supplied by switching the first three-way valve 25 in such a way that it connects the cleaning liquid supply 9 and the milk filter 8, and subsequently supplying it from a holder 29, which may also be a water pipe. If desired, an additive (or an additive mixture) may be added from the additive storage reservoir 28 and additive line 26 by switching the valve 27. An additive is for example an acid, a base or a surfactant.

[0055] The cleaning liquid to be supplied in countercurrent 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 part 22, the filter part 21, the first end 15 and the milk inlet opening 18, and carry along foreign material in the process. The cleaning liquid can then run away to the sewer or a collecting receptacle via the milk line part 5-2 and the now switched second three-way valve via the cleaning liquid discharge 10. As a result thereof, the dirty cleaning water does not have to flow through the rest of the milking device.

[0056] In this case, it should be noted that, during milking, the milk will fill the filter volume (parts 22 and 24) from below. Any parts floating on the milk will, in theory, then also end up mainly in the upper filter openings of the filter part 21. Furthermore, with a standard construction of the milk filter 8, the cleaning action has been found often to be insufficient in particular for these upper filter openings. The solution according to the invention will be explained below on the basis of FIG. 3.

[0057] FIG. 3 diagrammatically shows a detail of the milk filter 8, in particular of an upper part thereof. In this case, arrow A indicates the upright vertical direction of use.

[0058] The milk filter 8 again comprises the second end 17 with the milk discharge opening 19, the cylindrical housing or outer wall 23, the core 20 and the filter part 21, internally comprising the first volume part 24 and the second volume part 22. In addition, some of the filter openings 31 are indicated diagrammatically together with a part of the cleaning liquid stream running through them, by the double arrow, as well as a bend 32 and a straight piece 33 with length/in the second end 17, and an O-ring 40 and a securing part 41.

[0059] When cleaning liquid, optionally with added compressed air or the like, enters the milk filter 8 via the milk discharge opening 19, it will first flow into the conically widening part of the second end 17, over the (optionally rounded) top side of the core 20. It should be noted that it is desirable to widen, in order to make a larger diameter of the filter part 21 possible, which is in turn desirable in order to obtain a sufficiently large total filter surface without the filter being inconveniently long.

[0060] Subsequently, the cleaning liquid reaches the bend 32 which is desirable in order to be able to use a cylindrical filter part 21. After the bend, the liquid first passes through the straight piece 33 with length/before reaching the upper filter openings 31 of the filter part 21. Here, the cleaning liquid starts to flow out of the filter part and clean it.

[0061] The reason for first making the cleaning liquid pass through the straight piece 33 has already been given above. In short, it is presumed, without the Applicant considering itself to be bound to a specific explanation or illustration, that the cleaning liquid does not have a clear direction after the bend, and that the boundary layer on the walls is initially laminar and grows until the accelerated stream which has been made to run parallel to the housing wall is able to make the laminar boundary layer turbulent. The fluctuations in the velocity and the wall sheer stress near the walls are then so large that the cleaning action of the liquid is sufficient.

[0062] Although it is possible to increase the velocity of the cleaning liquid, as a result of which the latter develops a turbulent boundary layer even sooner, this not only requires more energy, but, due to the associated pressures and flow rates, also means that the milking device has to meet other, more elaborate regulations. According to the invention, an alternative solution is provided which does not require said increased velocity and does therefore not fall under these regulations by first passing the cleaning liquid through the straight part 33. In that straight piece 33, the stream will develop, the cleaning liquid in the central duct being made to run parallel to the housing wall, the boundary layer will grow and will change from laminar to turbulent (in time). Due to the fact that the boundary layer will then already have changed to being turbulent at, at least closer to, the start of the filter openings 31, the filter openings 31/the filter part 21 will be cleaned more thoroughly. From the detached part of the filter part 21, the geometry of the entire duct changes and a stream of cleaning liquid with a new boundary layer will pass to the other side. But because there is now no bend, the velocity distribution of the cleaning liquid is actually optimal and sufficiently quick to render the (new) boundary layer turbulent almost immediately.

[0063] It should be noted here that the straight piece 33 is formed in the second end 17. In theory, it is also possible to form it by not providing the filter part 21 itself over a corresponding length on the top side with filter openings 31. However, this may possibly result in the upper part of the first volume part 24 behind this part of the filter part without filter openings being cleaned less thoroughly, which is undesirable, or in the part without filter openings having to be pressed against another structural part of the milk filter, such as an outer wall of the housing. In effect, this part without filter openings then forms a part of the housing and does not have a filtering or other effect. In FIG. 3, this could be illustrated as an alternative by extending the filter part 21 along the wand of the second end 17 in at least a bottom part of the straight piece 33. It is therefore clarified here that, according to the invention, the first volume part 24 does not substantially extend beyond the upper filter openings 31.

[0064] The length/of the straight piece 33 is not particularly limited, albeit that the stream of cleaning liquid has to have sufficient opportunity to develop. To this end, the length/is advantageously at least ten or even more times greater than the radial thickness a of the second volume part 22. In order to keep the flow properties of the cleaning liquid broadly the same on both sides of the filter part 21, the radial thickness is preferably approximately equal to the radial thickness b of the first volume part 24. FIG. 4 diagrammatically shows a perspective view of a filter part 21. It comprises a frame of supporting wires 50 surrounded by rings 51 and with the filter openings 40 therebetween. FIG. 5 shows a diagrammatic cross-sectional view of the filter part from FIG. 4, more particularly through a plane which extends through the left-most supporting wire and the right-most supporting wire 50. Reference numeral 52 denotes connecting points and reference numeral 53 denotes the longitudinal direction of the filter part 21.

[0065] For the sake of simplicity, the filter part 21 shown here consists of eight rings 51 around a frame of six supporting wires 50, thus producing forty-two openings 40. In practice, in view of the often-desired dimensions of the filter openings 40, many more such openings will have been produced and accordingly a plurality of supporting wires 50 and rings 51 are illustrated in FIGS. 4 and 5. Furthermore, for the producibility of the filter part 21, it is often easier to not provide individual rings 51, but one long wire which is wound around the supporting wires 50 in spiral-shaped windings. Finally, it is also possible to reverse the function of the supporting wires 50 and the rings 51. In this case, this means that precisely the vertical elements or rods 50 will have a tapering cross-sectional profile and will be held together by the rings 51. Obviously, the respective numbers will be very different in the case of such a reversal of function, such as for example sixty rods 50 and three or four rings 51. This does not affect the further explanation.

[0066] In the example, the widest side of the wire/windings 51 is situated on the outer side of the filter element 21. This allows milk to pass from the outside to the inside through the filter element 21, so that cleaning liquid in counterflow direction, i.e. from the inside to the outside, will be able to efficiently detach the filtered-out dirt and carry it along. In order to keep the disturbance of the flow of milk or cleaning liquid, respectively, as minimal as possible, the supporting wires 50 are situated on the inner side of the rings 51. However, it is also possible to attach supporting wires 50 on the outer side. In addition, it is possible to fit the rings 51 precisely with the thinnest side facing outwards, in particular when the milk has to flow through the filter part from the inside to the outside.

[0067] The filter openings 40 have a width d1 and a length d2. In practice, the width d1 will be relatively smaller than the width d2, for example by one or more orders of magnitude. For milk filters, a suitable width is, for example, between 50 and 90 ?m, such as 60-80 ?m. The length may be, for example, 5 or 10 mm, or even more. Since such lengths allow hairs of dairy animals parallel to the opening 40 to pass through the latter, it is important to choose the width d1 to be not much greater than the thickness of a hair. Cattle hair has a thickness of approximately 60-100 ?m, but will almost never be entirely straight. A width d1 will then preferably not have to be much greater than those 60 ?m, such as for example between 60 and 80 ?m.

[0068] The cross section shown in FIG. 5 shows the tapering cross-sectional profile of the wire, that is to say the rings 51. Here, the profile is triangular, with the largest side facing outwards, and the thinnest side facing inwards on the filter part 21. On this thinnest side, the rings are attached to the supporting wires 50 by means of an attachment point 52, for example with a resistance weld, such as a spot weld. It should be noted that the cross-sectional profile may also be less tapering or acute and may be, for example, rounded, semi-elliptic, semi-circular, or even frustoconical. This still retains the advantage of filter openings widening in the direction of the milk flow, but there are other possibilities of attaching the wire to the frame.

[0069] On the (straight) outer side, the width of the opening is d1, while the width increases to d3 towards the thin side. Where d1 is determined by wishes with regard to the material to be filtered out, the width d3 is not limited thereby. The latter is more likely to be determined by the width of the rings 51, and the degree of tapering of the cross-sectional profile. It may be advantageous to opt for a relatively gradually tapering profile, in other words a relatively flat wire, so that d3 is not very much smaller than d1. For example, d3 is between 120 and 160 ?m.

[0070] The illustrated exemplary embodiments are by no means intended to be limiting. Rather, the scope of protection of the invention is determined by the attached claims.