Abstract:
The invention relates to apparatus for milking animals such as cows, components of the apparatus and methods of milking animals employing the apparatus. The apparatus comprises at least two resilient membranes having a space therebetween into which the teat of the animal may be inserted. The membranes are held by a support structure under tension in a direction transverse to the direction of insertion of the teat, to protect the teat from excessive force when the membranes fall onto the teat.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of GB0716800.8, filed Aug. 29, 2007, which is incorporated herein by reference in its entirety. This application is also related to U.S. patent application Ser. No. 11/252,268, filed Oct. 17, 2005. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a milking apparatus, i.e. an apparatus for removing milk from a teat of an animal, such as a cow, sheep, goat, horse, buffalo, or camel. It also relates to a method of use of such an apparatus. 
     2. Summary of the Prior Art 
     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 partial vacuum draws milk from the teat, but also causes congestion of the teat tissues, arising from the accumulation of blood and other fluids. In order to relieve this congestion, the region between the outer body and the liner is periodically brought to atmospheric pressure. This causes the liner to collapse around 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 a periodic over pressure around the liner, rather than atmospheric pressure, the basic arrangement has stayed the same. Thus, the basic liner arrangement disclosed in e.g. GB270316, published in 1927, is not dissimilar from e.g. U.S. Pat. No. 6,427,624 published in 2002. 
     One problem associated with the liner arrangement in the conventional apparatus described above is that, when the region between the body and the liner is brought to atmospheric pressure, the liner closes in tightly around the teat end, so that the end of the teat often experiences excessive local pressure. This means that, in order to avoid damage to the teat end, only low suction forces may be applied to the teat as a whole during milking and any periodic over pressure applied to the outside of the liner must also be kept at a low level. Thus, the efficiency of the milking process is impaired by the need to avoid excessive force being applied to the teat end, so as to maintain teat health. 
     Recently, improvements have been made to the conventional apparatus described above, so that when the liner closes in around the teat in order to relieve congestion of the teat tissue, it collapses more evenly along the length of the teat. EP1647183 describes a milking apparatus in which the liner has membranes that are held under transverse tension i.e. tension in a direction generally perpendicular to the direction of elongation of the barrel of the teat. The membranes are held under this transverse tension in their normal rest state, i.e. even when the milking apparatus is not in operation and no suction or over pressure is being applied. 
     The purpose of the transverse tension is to prevent the membranes contracting too closely around the teat end when the milking apparatus is in operation. Thus, excessively high forces and damage to the teat end can be avoided, while at the same time, maintaining the suction forces experienced by the teat at sufficiently high levels to achieve efficient milking action. 
     The transverse tension in the liners allows the pressure applied to the barrel of the teat to be maintained at useful levels for milking, while at the same time preventing damage to the teat end when the liner collapses around the teat to relieve congestion within the teat. In effect, the transverse tension of the liners allows the liners to collapse more evenly along the length of the teat during milking than is the case in the conventional milking apparatus described above, and so the milking process partly mimics the sucking action of a calf. 
     In the milking apparatus described in EP1647183, transverse tension of the membranes of the liner is achieved by fixing the membranes to attachment points on the interior walls of the outer body housing the liner or onto rods fixed within the outer body. However, since these attachment points are only accessible from the interior of the body housing the liner, the process of affixing the membranes to the outer body, so that they are under transverse tension, is awkward and time-consuming. Furthermore, the outer body often includes external attachments which make it difficult to manipulate. Another problem is that the attachment of the liner membranes directly to the outer body requires the outer body, which is in general a standard component, to be specially adapted to hold the membranes. 
     SUMMARY OF THE INVENTION 
     At its most general, the present invention proposes that the milking apparatus described above, in which the membranes of the liner are held under transverse tension, be provided with a support structure which is not a fixed part of the outer body and so may be insertable into the outer body. The function of the support structure is to hold the membranes of the liner under transverse tension. As the support structure is not a fixed part of the outer body, and functions to hold the membranes of the liner under transverse tension, it will be understood that the support structure may perform this function independently of the outer body. Accordingly, during assembly of the milking apparatus, the membranes may be first mounted onto the support structure, which is then inserted into the outer body. By means of this arrangement, the membranes may be already under transverse tension when they are inserted into the outer body. 
     The support structure is not a fixed part of the outer body, so in other words may be a discrete component of the apparatus and adapted to be removable from the outer body. By providing such a separate support structure onto which the membranes may be mounted e.g. before they are inserted into the outer body, it is possible to design a support structure that is easy to manipulate and which allows the membranes to be placed under transverse tension more easily than is the case for the apparatus of the prior art. Note, however, that the present invention does not exclude the possibility that the support structure is positioned within the outer body before the membranes are mounted thereon. 
     Furthermore, the use of a support structure allows the milking apparatus to be assembled using a standard outer body component, which does not need to be adapted to hold the membranes of the liner under transverse tension. 
     Thus, in one aspect 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 a first and a second resilient membrane, the first and second membranes being held within the outer body, the membranes forming a space therebetween into which the teat is receivable when it is inserted into the opening;   a support structure on which the membranes are mounted, which support structure maintains the membranes under tension in a direction transverse to said first direction when there is the same pressure across the membranes, wherein the support structure is housed within the outer body and maintains the membranes under said tension independently of the outer body; and   a pressure generating device for providing a pressure difference across said membranes.       

     In some embodiments, 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 a first and second resilient membranes, the first and second membranes being held within the body and forming a space therebetween into which the teat is receivable when it is inserted into the opening; 
     a support structure held within the body, the support structure having a first tensioning element having two spaced-apart attachment points and a second tensioning element having two spaced-apart attachment points, the first membrane being attached to the first tensioning element of the support structure at the two spaced-apart attachment points, so that the first membrane is under tension in a direction transverse to said first direction when there is the same pressure across the membranes, the second membrane being attached to the second tensioning element of the support structure at the two spaced-apart attachment points, so that the second membrane is under tension in a direction transverse to said first direction when there is the same pressure across the membranes; and 
     a pressure generating device for applying a pressure difference across the membranes. 
     As discussed above, the support structure is not a fixed part of the apparatus. Accordingly, in another aspect, the present invention may provide a kit of parts for constructing an apparatus for removing milk from the teat of an animal, the kit comprising:
         an outer body having an opening therein into which the teat is insertable in a first direction;   at least a first and a second resilient membrane holdable within the outer body;   at least a first tensioning element having two spaced-apart attachment points and a second tensioning element having two spaced apart attachment points for constructing a support structure, the support structure being housable within the outer body; and   a pressure generating device for providing a pressure difference across said membranes,
 
wherein the first membrane is attachable to the first tensioning element at the two spaced-apart attachment points so that the first membrane is under tension in a direction transverse to said first direction when there is the same pressure across the membranes and wherein the second membrane is attachable to the second tensioning element so that the second membrane is under tension in a direction transverse to the first direction when there is the same pressure across the membranes,
       

     wherein the tensioning elements of the support structure are capable of maintaining the membranes under said tension independently of the outer body. 
     The support structure is not a fixed part of the apparatus and so may hold the membranes under transverse tension independently of the outer body of the milking apparatus. Accordingly, in another aspect, the present invention may provide a component of an apparatus for removing milk from the teat of an animal, the component having an elongate shape defining a first direction along its direction of elongation, the component comprising at least a first and a second resilient membrane, and a support structure on which the first and second membranes are mounted, the support structure having a first tensioning element having two spaced-apart attachment points and a second tensioning element having two spaced-apart attachment points, 
     wherein the first membrane is attached to the first tensioning element of the support structure at the two spaced-apart attachment points, so that the first membrane is under tension in a direction transverse to said first direction when there is the same pressure across the membranes, and the second membrane is attached to the second tensioning element of the support structure at the two spaced-apart attachment points, so that the second membrane is under tension in a direction transverse to said first direction when there is the same pressure across the membranes. 
     Similarly, in a further aspect, the present invention may provide a kit of parts for constructing a component of an apparatus for removing milk from the teat of an animal, the kit comprising 
     at least a first and a second resilient membrane; and 
     at least a first tensioning element having two spaced-apart attachment points and a 
     second tensioning element having two spaced-apart attachment points, 
     wherein said membranes and said tensioning elements are attachable together to form a component having an elongate shape and defining a first direction along its elongation direction, 
     and wherein the first membrane is attachable to the first tensioning element at the two spaced-apart attachment points so that the first membrane is under tension in a direction transverse to said first direction when there is the same pressure across the membranes and wherein the second membrane is attachable to the second tensioning element so that the second membrane is under tension in a direction transverse to the first direction when there is the same pressure across the membranes. 
     The apparatus provided by the present invention is useful for milking animals. Accordingly, in a still further aspect, the present invention may provide a method of removing milk from the teat of an animal, comprising:
         inserting the teat into a space formed between at least a first and a second resilient membrane housed in an outer body; and   generating a pressure difference across said membranes to cause the membranes to fall onto the teat,
 
wherein the membranes are mounted on a support structure, and maintained under tension in a direction transverse to the teat insertion direction by the support structure before the pressure difference is generated across the membranes, wherein the support structure is housed within the outer body and maintains the membranes under said tension independently of the outer body.
       

     Accordingly, the present invention provides a support structure which holds the membranes of the liner under transverse tension. As will be understood from the discussion above, it may be preferable that the support structure has a first tensioning element having two spaced-apart attachment points and a second tensioning element having two spaced apart attachment point. The first membrane may be attached or attachable to the first tensioning element of the support structure at the two spaced apart attachment points so that the first membrane is under tension in a direction transverse to the first direction. Similarly, the second membrane may be attached to the second tensioning element of the support structure at the two spaced-apart attachment points so that the second membrane is under tension in a direction transverse to the first direction when there is the same pressure across the membranes. This tensioning effect may be achieved by making the relaxed distance between attachment points on, for example, the first tensioning element of the support structure greater than the relaxed length of the first membrane which is to span these points and similarly for the second membrane and corresponding tensioning element. The attachment points of the support structure are spaced radially inward from the outer body. 
     The tensioning elements may be elongate structures extending substantially along the length of the liner, each tensioning element having a plurality of further pairs of spaced-apart attachment points located along the length of the tensioning elements. The pairs of spaced-apart attachment points on each tensioning element may in fact be merged to form a pair of spaced-apart attachment regions, possibly extending along the edges of the tensioning elements. In other words, the attachment points may actually be lines, possibly extending along the edges of the tensioning elements. 
     Preferably, the tensioning elements are themselves resilient. This means they may be flexed in order to facilitate mounting of the membrane. 
     The section between the two attachment points on each tensioning element may be either straight or curved, or have a peak. When curved or peaked elements are used, attachment of the membranes becomes easier, since the elements are capable of being flexed more easily than straight elements in order to bring the distance between the attachment points closer to the relaxed length of the membrane. Furthermore, using curved or peaked tensioning elements, particularly peaked elements, it is easier to tension the membranes at the low transverse stress levels preferred for milking, since the elements will tend to bend to relieve some of the tension in the membrane. 
     Preferably, the tensioning elements of the support structure to which the membranes are attached are joined to form a tube enclosing the membranes. The tensioning elements of the support structure may be held together by the membranes themselves or may be connected directly to each other. 
     The membranes may be tensioned by being clipped onto the support structure at the attachment points. Otherwise, they may be attached to the support structure by means of protrusions formed on the membranes, the protrusions being capable of engaging with slots present at the attachment points of the support structure. The protrusions may be ribs extending along the edges of the membranes. The protrusions can also be beads present on the edges of the membranes. 
     Preferably, the space formed by the membranes is an enclosed space sealed from the outer body. 
     To facilitate the use of the support structure in apparatus with a standard outer body component as discussed above, the membranes or the support structure may have an engagement portion attached thereto, for engaging with the outer body to support the membranes and support structure in the outer body. Preferably the engagement portion is a flange which fits over the top of the body, possibly attached to the membranes. 
     The resilient membranes may be put under axial tension (i.e. tension in the first direction), as well as transverse tension, in order to tune the membranes more effectively to the shape of the teat. In this case, it may be useful for the level of axial tension to be adjustable. Such tuning allows improved control over the pressures (forces) exerted on the teat and therefore may be used to ensure effective milking action, while optimizing teat health. 
     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. In a further alternative, four or more membranes may be used. 
     In the case that there are three or more membranes, joined together to form a polygonal cross-section, the membranes may be attached to the support structure at the joins between the membranes. 
     The membranes may be part of a one piece liner mounted inside the outer body. 
     Normally, the space between the membranes will be subject to suction, in a way similar to the interior of known liners, while the region between the outside of the membranes and the interior of the body into which the membranes are received is periodically brought to atmospheric pressure in order for the liner to close around the teat, thus providing temporary relief from the suction forces and reducing teat congestion. However, it is possible instead to provide a periodic overpressure to the region between the membranes and the outer body, since it is believed that such a positive pressure is of beneficial effect, as it matches the internal pressure of the teat more closely. Furthermore, it is possible to use only over pressure without suction being applied to the interior of the liner. 
     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. 
     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. 
     Although the present invention has been discussed above in terms of apparatus for removing milk from the teat of an animal, such as a cow, sheep, goat, horse, buffalo, or camel, 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 periodic pressure difference generated across those membranes causes the membranes to fall onto the teat. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will now be described in detail, by way of example, with reference to the accompanying drawings, in which: 
         FIGS. 1A ,  1 B, and  1 C are a first embodiment of the invention,  FIG. 1A  being the transverse section along the line A to A in  FIG. 1B ,  FIG. 1B  being the transverse section along line B to B in  FIG. 1A , and  FIG. 1C  showing the liner element  16  of  FIG. 1A  in detail. 
         FIGS. 2A and 2B  show the liner and support structure according to second and third embodiments of the invention. 
         FIG. 3  shows the liner and support structure according to a fourth embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring first to  FIGS. 1A ,  1 B, and  1 C, a milking apparatus comprises an outer body  10 , the interior of which is hollow and which contains a support structure  12 , into which is mounted a liner  16 . The support structure has three tensioning elements  14   a ,  14   b ,  14   c  corresponding to the three resilient membranes  18   a ,  18   b ,  18   c  of the liner  16 . The three membranes  18   a ,  18   b ,  18   c  of the liner  16  are joined at their longitudinal edges to define a space  20  therebetween which is triangular in transverse section and further spaces  22   a ,  22   b ,  22   c , which are each bounded by one of the membranes  18   a ,  18   b ,  18   c  and the corresponding tensioning element  14   a ,  14   b ,  14   c  of the support structure  12 . Locks  24   a ,  24   b ,  24   c  at the longitudinal joins of the membranes  18   a ,  18   b ,  18   c  allow each membrane to be clipped at its edges to tensioning elements  14   a ,  14   b ,  14   c  of the support structure. 
     In this embodiment, each lock  24   a ,  24   b ,  24   c  is clipped to two tensioning elements  14   a ,  14   b ,  14   c  of the support structure  12  and thus brings the edges of the tensioning elements of the support structure together. However, this is not essential, and further embodiments may be possible in which each lock provided on a membrane clips onto only one tensioning element of the support structure. 
     The body  10  has an opening  26  at its upper end, aligned with the space  20 , into which a teat  28  of e.g. a cow may be received. At the end of the body  10  remote from the opening  26  is a suction outlet  30  which is connected to a vacuum apparatus for generating a reduced pressure within the space  20 . 
     In this embodiment, the support structure  12  is independent of the outer body  10 . However, the support structure may also be attached to the outer body, e.g. to hold the support structure  12  and hence the liner  16  in place. 
     Each of the resilient membranes  18   a ,  18   b ,  18   c  is held under transverse tension, i.e. tension in the plane of the view of  FIG. 1A , when mounted in the corresponding tensioning element  14   a ,  14   b ,  14   c  of the support structure  12 . This is achieved by making the relaxed spacing of the edges of the tensioning elements  14   a ,  14   b ,  14   c  greater than the relaxed spacing of the locks  24   a ,  24   b ,  24   c.    
     When suction is applied to the outlet  30 , thereby reducing the pressure in the space  20  relative to the internal pressure of the teat, milk is expressed from the teat and passes out of the outlet  30 . The spaces  22   a ,  22   b ,  22   c  experience cyclic pressure induced by a pulsator (not shown) attached to the inlet  36 . The lowest level of the pressure cycle induced by the pulsator corresponds to the pressure induced in the space  20 , while the highest level of the pressure cycle corresponds to atmospheric pressure. 
     When the pressure in the spaces  22   a ,  22   b ,  22   c  is greater than the pressure in the space  20 , the membranes  18   a ,  18   b ,  18   c  are deformed onto the teat and the space  20  closes around the teat, thereby providing temporary relief from suction and reducing congestion of the teat tissue. By holding the membranes  18   a ,  18   b ,  18   c  under transverse tension, they are unable to become wrapped too closely around the teat end during the process of collapse of the liner onto the teat. Thus, the local forces acting on the teat end are prevented from reaching excessive levels that might impair teat health. At the same time, substantial pressure may be applied to the barrel of the teat, in order to relieve congestion of the teat tissue, arising from the build-up of blood and other fluids, and a good balance is achieved between the requirements of teat health and milking efficiency. Indeed, the maximum pressure induced by the pulsator may be raised above atmospheric pressure, so as to match more closely the internal pressure of the teat. 
     In effect, the action of the resilient membranes, when placed under transverse tension, partly mimics the sucking action of a calf, by applying pressure over substantially the whole length of the teat within the milking apparatus, without exerting excessive forces on the end of the teat. 
     By mounting the membranes  18   a ,  18   b ,  18   c  of the liner  16  onto the tensioning elements  14   a ,  14   b ,  14   c  of the support structure  12  and inserting this structure into the outer body  10 , the assembly of the milking apparatus is greatly simplified, as the tensioning elements  14   a ,  14   b ,  14   c  of the support structure  12  are easier to manipulate than the outer body  10 . In addition to this, no special attachment points for tensioning the membranes are necessary in the outer body  10 , and thus a standard component may be used. 
     In this first embodiment, the liner  16  has an upper flange  32  which fits over the top of the outer body  10 . The suction outlet  30  is integral with the membranes  18   a ,  18   b ,  18   c  and has a further flange  34  fitting over the bottom of the body  10 . Thus, in this arrangement, it is possible for the membranes to be under longitudinal tension (i.e. in the axial direction of the teat) as well as under transverse tension. This allows the balance between the barrel pressure and the teat end pressure to be optimized by adjustment of the transverse and axial tension. 
     Further embodiments of the invention are possible, in which the liner has two resilient membranes or over three membranes. Preferably, the liner has either two or three membranes. Most preferably, it has three membranes. 
     The tensioning elements  14   a ,  14   b ,  14   c  of the support structure  12  shown in  FIG. 1A  are curved. However, other geometries are possible. For example, a second embodiment of the invention, shown in  FIG. 2A , has a support structure  40  with tensioning elements  42   a ,  42   b ,  42   c  that are peaked in shape and hold the membranes  46   a ,  46   b ,  46   c  of the liner  44  under tension. As in the case of the first embodiment, the membranes  46   a ,  46   b ,  46   c  are clipped onto the tensioning elements  42   a ,  42   b ,  42   c  of the support structure  40  by means of locks  48   a ,  48   b ,  48   c  provided at the longitudinal joins of membranes  46   a ,  46   b ,  46   c.    
     In a third embodiment of the invention, shown in  FIG. 2B , the support structure  50  has tensioning elements  52   a ,  52   b ,  52   c  that are straight, and hold the membranes  54   a ,  54   b ,  54   c  of the liner  56  under tension. As in the case of the first and second embodiments, the membranes  54   a ,  54   b ,  54   c  of the liner  56  are clipped onto the tensioning elements  52   a ,  52   b ,  52   c  of the support structure  50  by means of locks  58   a ,  58   b ,  58   c  provided at the longitudinal joins of membranes  54   a ,  54   b ,  54   c.    
     In general, it is easier to mount the resilient membranes of a liner onto tensioning elements that are themselves resilient. This is because these tensioning elements may be flexed in order to attach the membranes to the attachment points on each element. This process is further simplified by using tensioning elements that are already curved or peaked, particularly peaked, in their unloaded state. Furthermore, by using curved or peaked tensioning elements, particularly peaked elements, it is easier to tension the membranes at the low stresses required by this application, since these elements will tend to bend in order to relieve some of the tension in the membrane. 
     In the first, second, and third embodiments of the invention described above, the support structure is arranged so that the tensioning elements are held together by the locks provided on the liner, when the liner is mounted onto the support structure. However, a fourth embodiment of the invention is possible in which the tensioning elements are directly connected to form a shell. This embodiment is shown in  FIG. 3 , in which the liner  60  has a plurality of membranes, two of which,  62   a  and  62   b  are shown in this Figure. The membranes  62   a ,  62   b  are joined at their longitudinal edges. The liner  60  is mounted in an inner shell  66  by means of beads  64   a ,  64   b  provided along the longitudinally extending join of the membranes  62   a ,  62   b.  The inner shell  66  has openings  68   a ,  68   b  through which the beads  64   a ,  64   b  may be threaded in order to mount the liner in the shell. 
     Alternatively, the longitudinally extending joins of the membranes may be provided with ribs having enlarged outer ends. The membranes are mounted in the inner shell by sliding the ribs into slots provided in the inner shell.