referring first to fig1 a 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 fig1 a , 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 . the membranes 12 , 14 are put under transverse tension , i . e . tension in the plane of the view of fig1 a . 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 . 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 fig2 a 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 . the teat is thus massaged all over , not just at its end , making the action more like the sucking of the calf . in the second embodiment , illustrated in fig3 a , 3 b , 4 a and 4 b , there are three membranes 40 , 42 , 44 within a hollow triangular body 46 . as can be seen from fig3 a , 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 . 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 . 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 . again , fig4 a and 4b illustrate the second embodiment when a teat 66 is inserted into the structure shown in fig3 a 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 . 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 . fig5 a to 5d 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 fig3 and 4 , fig5 b 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 fig5 , the liner is moulded in one piece , i . e . the membrane is joined and moulded around each rod 74 , as shown in fig5 c , 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 . 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 fig4 , 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 . fig6 a and 6b illustrate a fourth embodiment , which is a development of the third embodiment . features in common with fig5 have been given the same reference numerals and are not described again . in addition , fig6 a 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 fig5 into two axially separated chambers 75 a , 75 b . whilst fig6 a 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 . in the arrangement shown in fig6 a and 6b , the action of each chamber 75 a , 75 b on the inserted teat 24 may be independently controllable . thus , in use , the teat 24 is inserted when no pressure is applied to the chambers 75 a , 75 b , as shown in fig6 a . 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 . 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 . fig7 a to 7c show a fifth embodiment of the invention , which resembles the embodiment shown in fig5 a to 5d . the same reference numbers are used for corresponding parts , and these are not described again . fig7 c 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 .
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 .