Abstract:
Apparatus for removing milk from a teat of an animal comprising an outer body having an opening into which the teat is insertable into a space defined by two or more resilient membranes. A pressure difference is applied between the space between the resilient membranes and a region outside the membranes to cause the membranes to ball on to the teat, thereby massaging it to extract milk. To avoid exerting excessive force on the end of the teat yet retain a useful massage pressure, the resilient membranes are under tension in a direction transverse to the direction of teat insertion before the provision of any pressure difference (before the insertion of the teat).

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of GB Application No. 0423132.0, filed Oct. 18, 2004, which is incorporated herein in its entirety.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a milking apparatus, i.e. an apparatus for removing milk from a teat of an animal. It also relates to a method of use of such an apparatus.  
         [0004]     2. Summary of the Prior Art  
         [0005]     In a conventional milking apparatus, a cylindrical liner of resilient material is housed within an outer body, and the liner is tensioned along the axis of the cylinder. The teat of the animal is then inserted through an opening in the body into the cylindrical liner, and then suction is applied to another opening in the body, at the other end of the cylindrical liner to that in which the teat is inserted, to create a partial vacuum. This causes the liner to contract around the teat, and so causes milk to be expressed from the teat. Because of the suction, the liner closes on the teat, so providing relief from the suction. Such milking apparatuses have been known for around 100 years, and although many modifications to the basic arrangement have been suggested, such as the application of an over pressure around the liner, as well as suction, the basic arrangement has stayed the same. Thus, the basic liner arrangement disclosed in e.g. GB270316, published in 1927, are not dissimilar from e.g. U.S. Pat. No. 6,427,624 published in 2002.  
       SUMMARY OF THE INVENTION  
       [0006]     However, in all the time that such milking apparatuses have been used, little thought seems to have been given to the precise effect of the forces that are generated. The liner is the only part of the milking apparatus that applies forces to the teat, and while these forces are low, they are repeated many times and therefore have a significant effect on the teat. However, the forces are complicated as both the liner and the teat are resilient. The forces are therefore complex.  
         [0007]     Initially, the teat is exposed to the suction of the milking apparatus, and this exerts a downward force on the teat, particularly the teat end. As a result of this, the tissue of the teat can fill excessively with fluid, since the suction forces are around −40 kPa relative to atmospheric pressure. Then, as the liner closes around the teat, the liner will exert a pressure on the teat. However, basic membrane theory indicates that the tension in a membrane is equal to the pressure exerted by that membrane multiplied by its radius of curvature, and that means that the teat contact pressure is equal to the tension in the liner divided by the radius of curvature of the liner. Since the liner will conform to the teat, its radius of curvature is minimum at the end of the teat, so the membrane contact pressure is maximum at that end. Away from the teat end, the curvature is less, and therefore the contact pressure is less.  
         [0008]     Thus, in the known arrangements, the maximum teat contact pressure is exerted at the teat end, and therefore it has been realised that the existing milking apparatuses involve a compromise. If the tension is large, the forces generated at the teat end may damage the teat. However, if the tension is low, to avoid such damage, then the pressure applied on the teat away from the teat end (along the teat ‘barrel’) is small. In practice, since it is important to avoid damage to the teat, existing arrangements have, in fact, exerted only a small pressure on the teat, except at the teat end.  
         [0009]     Therefore it has been realised by the inventor that the milking action is almost entirely governed by pressure at the teat end. Thus, the milking action of the known apparatuses do not make use of the full length of the teat which is inserted within the liner.  
         [0010]     As has been mentioned above, existing liner arrangements put the liner under axial tension, the liner being stretched within the outer body.  
         [0011]     At its most general, the present invention proposes that milking apparatus be provided with membranes which are placed under transverse tension, i.e. tension in a direction generally perpendicular to the direction of elongation of the barrel of the teat. It has been found that such an arrangement with transverse tension enables pressure (pressing into the teat barrel) to be applied to the part of the teat other than the end, without pressure at the teat end being excessive.  
         [0012]     Thus, the present invention may provide apparatus for removing milk from the teat of an animal, comprising: an outer body having an opening therein into which the teat is insertable in a first direction; at least two resilient membranes within the body, the membranes forming a space therebetween into which the teat is receivable when it is inserted into the opening, the membranes being arranged to be under tension in a direction transverse to said first direction when there is the same pressure across the membranes; and  
         [0013]     a pressure generating device for applying a pressure difference across the membranes. The transverse tension is therefore present before the teat is inserted. In this way, the primary mechanism for providing the massage force to the teat is by membrane theory through the transverse tension experienced by the membranes. Other effects, such as bending etc., may be important but are small. The pressure generating device may apply a pressure difference by creating a pressure gradient through the plane of each membrane.  
         [0014]     Preferably, the space formed by the membranes is a closed space sealed within the outer body. For example, the membranes may extend between fixed attachment points within the body. The attachment points are preferably spaced transverse to the first direction away from the interior walls of the outer body. This enables the closed space defined by the membranes to surrounded by a common region, i.e. the pressure in the common region will be the pressure experienced by the outer surface of all membranes.  
         [0015]     The fixed attachment points may be rods extending in the first direction, the resilient membranes being transversely stretched between rods to put them under transverse tension. Accordingly, in another independent aspect of the invention, there may be provided apparatus for removing milk from the teat of an animal, comprising:  
         [0016]     an outer body having an opening therein into which the teat is insertable in a first direction;  
         [0017]     at least two membranes forming a space therebetween into which the teat is receivable when it is inserted into the opening; and  
         [0018]     a pressure generating device for applying a pressure difference across the membranes, wherein the membranes extend between attachment rods which are mounted within the outer body and extend substantially in the first direction, the rods being spaced transversely away from i.e. not in sealing contact with, the interior walls of the outer body along the majority or all of the axial extent (length in the first direction) of the rods. The rods may be attached to or mounted on the outer body at either or both of their ends.  
         [0019]     The resilient membranes may be put under axial tension (i.e. tension in the first direction), as well as transverse tension, if it is found that there needs to be a greater pressure on the teat end than on the part of the teat remote from the end. Each membrane can therefore effectively be tuned to the shape of a teat. Such tuning allows improved control over the pressures (forces) exerted on the teat and therefore may be used to ensure that teat health is kept to an optimum.  
         [0020]     It is possible for the present invention to be embodied using only two resilient membranes, arranged generally parallel to each other. However, preferably there are three membranes, joined together to form a triangular cross-section. The teat is then inserted between the membranes, perpendicular to the plane of such triangle. Then, the pressure difference closes the membranes on the teat. Four or more membranes may be used.  
         [0021]     The membranes may be part of a one piece liner mounted inside the outer body. For example, there may be three upstanding rods mounted in the outer body on which a liner is moulded such that three membranes stretch between the rods to form a triangle when viewed in cross section.  
         [0022]     Normally, the space between the membranes will be subject to suction, in a way similar to the interior of known liners. However, it is possible in addition to provide an over-pressure between the outside of the membranes and the interior of the body into which the membranes are received, since it is believed that such a positive pressure is of beneficial effect. Where a common region surrounding the membranes is used as described above, the same pressure can easily be applied to the outside of all membranes. Furthermore, it is possible to use only over pressure without suction being applied to the interior of the liner.  
         [0023]     Whilst the membranes may be of uniform thickness, it is possible for their thickness to vary, since that will vary the tension and hence the pressure exerted on the teat, along the length of the teat. Preferably, the transverse tension in the liner is relatively low, so that when the liner closes on the teat, it mimics the action of a suckling calf. Preferably, the membranes are made from a low modulus rubber. The average wall thickness is preferably low, e.g. less than 1.5 mm, preferably less than 1.3 mm. Additionally or alternatively, the modulus of the material (preferably rubber) of the membranes may also be low, in order achieve the desired low tension. Preferably, the shear modulus of the material is 0.8 MNm −2  or less.  
         [0024]     Preferably, the thickness and/or shear modulus value of the membranes varies in the axial (first) direction. The pressure distribution effected by the membranes on the teat depends on membrane thickness and shear modulus, so the pressure distribution can be matched to the shape of a teat. Thus, liners tailored to specific shapes of teat may be made. For instance, cows can have conical teats, parallel teats and barrel shaped teats. Goats and sheep also have shapes where more or less tension may need to be applied to a particular part of the teat. Also, a cow may have three teats of one shape and of another a different shape, all on the same udder. The present invention may allow teat liners to be designed to deal with such situations.  
         [0025]     In a development of the present invention, the apparatus is adapted to reduce the forces experienced by parts of the animal adjacent the opening in the outer body caused by the pressure difference between the space for the teat and the region outside the membranes. In particular, this development aims to mimic more closely the forces a teat would experience from a suckling calf.  
         [0026]     Thus, the membranes are preferably divided into two or more sub-membranes so that the membranes form a set of chambers surrounding said space, each chamber having one or more sub-membranes facing said space. The pressure generating device may be arranged to provide an independently controllable pressure difference for each chamber. The chambers may therefore be independently operable, e.g. in a user-determined sequence. This therefore allows different parts of the membrane surface to press against the teat at different times.  
         [0027]     Preferably, the membranes are divided to form a set of two or more chambers along the first direction.  
         [0028]     To form the chambers, the membranes are preferably divided into sub-membranes by dividing the region outside the membranes, e.g. between the membranes and the inside of the outer body. The dividing may be achieved by transverse resilient webs extending between each membrane and the inside surface of the outer body. In the triangular cross section arrangement described above, each chamber may extend completely around the membranes. Alternatively or additionally, dividing webs extending in the first (axial) direction may also be provided, so that the separate walls of each chamber may be individually controllable.  
         [0029]     The transversely extending webs may be integral with or attached to the membranes. Preferably, the webs are attached to the inside surface of the outer body by a clamp or other attachment.  
         [0030]     The pressure generating device is preferably arranged to provide an overpressure to each chamber, to increase the control of pressure exerted on the teat.  
         [0031]     There may be two or more chambers. Preferably, the chambers are pressurised in sequence e.g. along the first direction. This mimics the peristaltic action of a suckling calf. The more chambers there are, the more peristaltic the sequential action becomes. Other sequences of pressurising the chambers are also possible.  
         [0032]     Although, the present invention has been discussed above in terms of apparatus for removing milk from the teat of an animal, the present invention also relates to a method of removing milk, in which the teat is inserted between the resilient membranes of the apparatus and a pressure difference generated across those membranes that cause the membranes to fall onto the teat. The method aspect may include ways of sequentially pressurising the independent chambers defined above. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0033]     Embodiments of the present invention will now be described in detail, by way of example, with reference to the accompanying drawings, in which:  
         [0034]      FIGS. 1A and 1B  are the first embodiment of the present invention, before the application of suction,  FIG. 1A  being the transverse section along the line A to A in  FIG. 1B ,  FIG. 1B  being a longitudinal section along the line B to B in  FIG. 1A ;  
         [0035]      FIGS. 2A and 2B  illustrate the first embodiment, when suction is applied;  
         [0036]      FIGS. 3A and 3B  show the second embodiment of the present invention,  FIG. 3A  being a transverse sectional view along the line B to B in  FIG. 3B , and  FIG. 3B  being a longitudinal sectional view on the line A to A in  FIG. 3A ;  
         [0037]      FIGS. 4A and 4B  also show the second embodiment of the invention, when suction is applied,  FIG. 4A  being a transverse sectional view along the line B to B in  FIG. 4B , and  FIG. 4B  being a longitudinal sectional view along the line A to A in  FIG. 4A ;  
         [0038]      FIGS. 5A  to  5 D show a third embodiment of the invention,  FIG. 5A  being a transverse sectional view along the line A to A in  FIG. 5B ,  FIG. 5B  being a longitudinal sectional view along the line B to B in  FIG. 5A ,  FIG. 5C  being a close up view of the membrane attachment in  FIG. 5B , and  FIG. 5D  being an transverse sectional view of the liner separated from the outer body;  
         [0039]      FIGS. 6A and 6B  show transverse sectional views of a fourth embodiment of the invention,  FIG. 6A  showing a state where there is no pressure difference, and  FIG. 6B  showing a state where there is a pressure difference; and  
         [0040]      FIGS. 7A, 7B  and  7 C show a fifth embodiment of the invention,  FIG. 7A  being a transverse sectional view along the line A to A in  FIG. 7B ,  FIG. 7B  being a longitudinal cross-section along the line B to B in  FIG. 7A , and  FIG. 7C  being a close-up view of the membrane attachment in  FIG. 7B . 
     
    
     DETAILED DESCRIPTION  
       [0041]     Referring first to  FIGS. 1A and 1B , a milking apparatus comprises an outer body  10 , the interior of which is hollow and which contains two membranes  12 ,  14 . As can be seen from  FIG. 1A , the membranes  12 ,  14  are generally parallel to define a space  16  therebetween, and respective spaces  18 ,  20  between the membranes  12 ,  14  and the body  10 . The body  10  has an opening  22  at its upper end, aligned with the space  16 , into which a teat  24  of e.g. a cow may be received. At the end of the body  10  remote from the opening  22  is a suction outlet  26  which is connected to a vacuum apparatus for generating a reduced pressure within the space  16 .  
         [0042]     The membranes  12 ,  14  are put under transverse tension, i.e. tension in the plane of the view of  FIG. 1A . This can be achieved by providing ribs  12   a ,  14   a  on the longitudinal edges of the membranes  12 ,  14 , those ribs  12   a ,  14   a  being received in corresponding bores  28  in the body  10 , to hold the membranes  12 ,  14  in place. If the separation of the bores  28  in the transverse direction is slightly greater than the relaxed transverse separation of the ribs  12   a ,  14   a  the membranes  12 ,  14  will be under tension when the ribs  12   a ,  14   a  are mounted in the bores  28 .  
         [0043]     When suction is applied to the outlet  26 , thereby reducing the pressure in the space  16  relative to the spaces  18 ,  20 , the membranes  12 ,  14  will be deformed onto the teat, as illustrated in  FIGS. 2A and 2B . The space  16  is closed around the teat, thereby causing milk to be expressed from the teat. The milk then passes out of the outlet  26 . Due to the fact that the membranes  12 ,  14  are under transverse tension, they will close around the barrel of the teat, as well as the end of the teat itself. Thus, unlike the known liner arrangement, the present invention exerts pressure on the teat barrel.  
         [0044]     The teat is thus massaged all over, not just at its end, making the action more like the sucking of the calf.  
         [0045]     In the second embodiment, illustrated in  FIGS. 3A, 3B ,  4 A and  4 B, there are three membranes  40 ,  42 ,  44  within a hollow triangular body  46 . As can be seen from  FIG. 3A , the membranes  40 ,  42 ,  44  are joined at their longitudinal edges to define a space  48  therebetween which is triangular in transverse section. Beads  50  are provided along the longitudinally extending joins of the membranes,  40   42 ,  44 , which beads  50  are received in corresponding recesses  52  in the body  46 . Again, as in the first embodiment, by making the spacing of the recesses  52  greater than the relaxed spacing of the beads  50 , the membranes,  40 ,  42 ,  44  will be put under transverse tension when they are mounted in the body  46 .  
         [0046]     Again, as in the first embodiment, the body  46  has an opening  54  into which the teat is received so that the teat lies within space  48 . An outlet  56  is provided at the end of the body  46  remote from the opening  54  to which suction is applied.  
         [0047]     Note that in this second embodiment the structure defined by the membranes  40 ,  42 ,  44  has an upper flange  58  which fits over the top of the body  46 , and the suction outlet  56  is integral with the membranes  40 ,  44 ,  44  and has a further flange  60  fitting over the bottom of the body  46 . Thus, in such arrangement it is possible for the membranes  40 ,  42 ,  44  to be under longitudinal tension (i.e. in the axial direction of the teat) as well as under transverse tension. Moreover, in the second embodiment, there is an inlet  62  communicating with the spaces  64  between the membranes  40 ,  42 ,  44  and the body  46 , to enable an over-pressure to be applied to the outsides of the membranes  40 ,  42 ,  44 . Indeed, it may be possible for this embodiment to be operated only on over-pressure. In such a case no suction is applied to the outlet  56 .  
         [0048]     Again,  FIGS. 4A and 4B  illustrate the second embodiment when a teat  66  is inserted into the structure shown in  FIGS. 3A and 3B , suction applied to the outlet  56 , and an over-pressure applied to the inlet  62 . The membranes,  40 ,  42 ,  44  close around the teat  66 , closing the space  48 . Thus, again, pressure is applied to the teat not only at the teat end, but along the barrel of the teat.  
         [0049]     Thus, by putting the membranes under transverse tension, the pressures applied to the teat can be controlled so that pressure is applied over substantially the whole length of that part of the teat within the apparatus, thereby achieving an improved milking action, without exerting excessive forces on the end of the teat.  
         [0050]      FIGS. 5A  to  5 D illustrate a third embodiment of the invention. In this embodiment, the liner is attached within the outer body  70  in such a way that there is no contact between the inside side surfaces of the outer body  70  and the liner. Similar to  FIGS. 3 and 4 ,  FIG. 5B  shows that the liner in the third embodiment has three membranes  721 ,  722 ,  723  arranged in a triangular cross section. The membranes,  721 ,  722 ,  723  extend between upstanding rods  74  which are mounted in notches  79  formed on the base of the outer base  724  and extend up into corresponding notches  81  in the liner itself. In  FIG. 5 , the liner is moulded in one piece, i.e. the membrane is joined and moulded around each rod  74 , as shown in  FIG. 5C , where a skin  77  of resilient material surrounds the rod  74  and attaches to the membrane  721 ,  722 . The membranes therefore define a space  73  within them in which the teat (not shown) is receivable through opening  76 . As before, suction can be applied to space  73  through tube  80 .  
         [0051]     By spacing the membranes  721 ,  722 ,  723  away from the inside side surfaces of the outer body  70 , a common region  75 , i.e. a region having the same pressure, surrounds all of the membranes. This makes it easier to apply a constant overpressure, since whatever pressure is applied through inlet  84  will be experienced throughout common region  75  and therefore on all of the outer surfaces of the membranes  721 ,  722 ,  723 . Similarly to  FIG. 4 , the common region  75  is sealed at the top and bottom of the outer body by a flanges  78 ,  82  on the outer body  70 .  
         [0052]      FIGS. 6A and 6B  illustrate a fourth embodiment, which is a development of the third embodiment. Features in common with  FIG. 5  have been given the same reference numerals and are not described again. In addition,  FIGS. 6A and 6B  divide the common region  75  into separate regions  75   a ,  75   b . This division is achieved by providing a transverse webbing  86  around the outer surface of the liner (i.e. the outer surfaces of the membranes  721 ,  722 ,  723 ). The transverse webbing  86  is then attached to the inner surface of the outer body  70  using a clamp  88 . When attached in this way, the transverse webbing  86  separates (seals) the common region  75  shown in  FIG. 5  into two axially separated chambers  75   a ,  75   b . Whilst  FIGS. 6A and 6B  illustrate two chambers  75   a ,  75   b , three or more chambers may be used. Each chamber is provided with its own pressure input. Thus, chamber  75   b  may be pressurised via inlet  84 , whereas chamber  75   a  is pressurised by a separate inlet  85 . As before, suction is applied to the interior space  73  defined by the membranes,  721 ,  722 ,  723  via tub  80 .  
         [0053]     In the arrangement shown in  FIGS. 6A and 6B , the action of each chamber  75   a ,  75   b  on the inserted teat  24  may be independently controllable.  
         [0054]     Thus, in use, the teat  24  is inserted when no pressure is applied to the chambers  75   a ,  75   b , as shown in  FIG. 6A . Then, pressure is applied via inlet  85  to the upper chamber  75   a , which closes on the teat  24 . This closes the liner around the upper part of the teat  24  and in doing so protects the part of the teat outside the opening  76  from experiencing large pressure differentials.  
         [0055]     Subsequently, the lower chamber  75   b  is given an overpressure and closes around the lower part of the teat  24 . Both chambers  75   a ,  75   b  may then be released simultaneously. This sequence is then repeated to simulate the peristaltic motion effected by a suckling calf.  
         [0056]      FIGS. 7A  to  7 C show a fifth embodiment of the invention, which resembles the embodiment shown in  FIGS. 5A  to  5 D. The same reference numbers are used for corresponding parts, and these are not described again.  FIG. 7C  shows a different type of attachment at the top (upper) end of rod  74 . A protruding jaw  71  extends radially inwards from the interior wall of the outer body  70  and captures the rod  74 , thereby holding it securely in place.