NZ208931A - Diaphragm valve which admits air to milk conduit of teat cup or teat cup claw - Google Patents

Description

2089 31 Priority Date(s): J.^.

Complete Specification Filed: Class: 'dPMrJOpj'.AQtJR/QG,.

.......... Publication Date: . . 2 .0. FEB.M.... P.O. Journal, No: o N.Z. PATENT OFFICE 18 JUL 1984 neCEIVEO Patents Form No. 5 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION "AIR INLET VALVE FOR ADMITTING AIR TO THE MILK DRAIN CONDUIT OF A TEAT CUP OR COLLECTOR PIECE" "I", WE BIOMELKTECHNIK HOEFELMAYR & CO., of Steinwichslenstr. 20 CH-9052 Niederteufen AR/Switzerland, a Corporation working under the Laws of Switzerland, hereby declare the invention, for which-i-/we pray that a patent may be granted to me/us, and the method by which it is to be performed, to be particularly described in and by the following statement | (followed by page * •808331 1 Air Inlet Valve for Admitting Air to the Milk Drain Conduit of a Milking Cup or Collector Piece D_e_s c rip t i_o n The present invention relates to an air inlet valve for admitting air to the milk disdiargc* conduit of a milkirg cup or collector piece, comprising a housing secured to said j^q milking cup or collector piece, a diaphragm clamped within said housing, a valve poppet secured to said diaphragm so • as to project from one side thereof,, and a valve seat cooperating with said valve poppet to form a valve therewith, said valve being adapted to periodically open and close in response to pulsator pressure acting on the other side of said diaphragm so as to admit in its . opened state atmospheric air through a connecting conduit to said milk discharge conduit, particularly to the interior of a rubber teat cup.

- An air inlet valve of the type defined above is generally known in the trade and. has been found to operate in a highly satisfactory manner. The air inlet valve itself is ' of relatively small size with a diaphragm diameter of aboafe^|^) mm. Its individual parts are permanently secured to . another. fm4DECl986 U.S. Patent Specification 3482547 describes an air inlet valve for a milking' cup in which the valve itself is secured to a head portion of the rubber teat cup so as to periodically admit air under atmospheric pressure to the head portion of the rubber teat cup. A valve chamber communicating with the atmosphere through a first passage, with a pulsator through a second passage and with the head cavity of the rubber teat cup through a third passage, contains a valve body in the form for instance of a ball or a cylinder. In operation of a valve of this type, as a vacuum is generated in the pulsator passage, the valve body is aspirated against the action of gravity towards the outlet end of the pulsator 14. 2 208931 1 passage so as to simultaneously obstruct the latter passage and the third passage connected to the head cavity of the rubber teat cup. As the vacuum subsequently disappears, the valve body finally drops down by the force 5 of gravity, whereby the passage;leading to the head cavity of the teat-cup is opened, permitting atmospheric air to enter the teat cup through this passage communicating with the exterior of the valve. Due to the inertia of the valve body, valves of this type operate relatively sluggish 10 without properly defined opening and closing times. In addition, the atmospheric air admitted to the. head' portion of the rubber teat cup is not readily capable of promoting the draining of the milk body located below the teat, as the teat, at least in its tightly full state, completely 15 closes the suction nozzle of the; teat cup, so as to . least strongly retard the. passage of the air therethrough.

An air inlet valve has been proposed having a valve member in the form of a diaphragm having one side 20 exposed to atmospheric air while the other side communicates with the pulsator cavity of a milking cup via a passage opening in the valve, seat surface . In addition, the side of the diaphragm facing towards the pulsator cavity communicates with the interior of the head cavity of a rubber 25 teat cup via a further connecting passage.' As soon as a vacuum is created within the pulsator cavity, the communication between the pulsator cavity and the interior of the head cavity of the teat cup is interrupted. As the pressure, within the pulsator cavity subsequently rises to atmospheric" 30 pressure, the diaphragm is lifted from the valve seat, permitting air under atmospheric pressure to enter the head cavity of the rubber teat cup from the pulsator cavity through the connecting passage. Valves of this type suffe^ ,4 V from substantially the same disadvantages as the valves >(& 35 discussed in the first place. t " 4 DEC/936 Canadian Patent Specification 956593 describes a diaphragm air" inlet valve one side of which communicates with the puis- ft • ! ■'•t-v\ | ■•:.> ''-.c ■ [ • '-.'v"' - '. v 1' '\ v.- <* 203931 3 1 ator cavity of a milking cup, while the other aide of the diaphragm carries a valve poppet adapted in response to the position of the diaphragm to open and close the entry of; atmospheric air from the exterior of the- milking cup via 5 a passage communicating with the head cavity of the rubber teat cup. .

US -PS 3,255,732 describes an air inlet valve in which • an air inlet passage directly communicates with the suction 10 nozzle of the rubber teat cup below the teat via the milking cup. The air inlet passage is adapted to be selectively closed and opened to atmosphere by a diaphragm valve controlled in response to the pulsator pressure. This control is carried out in such a manner that the presence of a 15 vacuum in the pulsator results in atmospheric air being admitted to the suction nozzle of the rubber teat cup, while the presence of atmospheric pressure in the pulsator results in the connecting passage being closed so as to obstruct the flow of atmospheric air to the suction nozzle " 20 of the rubber teat cup. As a result, atmospheric air is always admitted to the suction nozzle of the rubber tea; cup at the beginning and during the suction cycle.

U.K. Specification 1106329 describes an air inlet valve 25 in which the lower end of the milking cup is provided with a clamping member for clamping the lower end of the suction r4sia : nozzle of the rubber teat cup, which is in the form of a gabled roof surface. The obliquely downwards extending opposing faces of the gabled portion ar„e formed with open-30 ings communicating with the milk discharge conduit. These openings are closed by the rubber teat cup when the latter is in its collapsed state, i. e. when the pressure within the pulsator passage is somewhat higher than that in the milk drain conduit. In this state, however, the pollapsed 35 rub.ber teat cup uncovers openings formed in the lateral end walls of the clamping member and communicating with the exterior, i.e. with air under atmospheric pressure. As a result, atmospheric air is admitted in this state to the suction nozzle below the teat. During the suction cycle, 208931 1 i.e. when the pulsator pressure substantially equals the" milking vacuum, the rubber teat cup returns to its substantially tubular state, resulting in the milk discharge passages of the clamping member being uncovered and the 5 openings communicating with the exterior being closed. A valve of this type suffers from the disadvantage,' however, that its control is fully dependent on the movements of the rubber teat cup. As a resultthe control times may widely vary in response to the flow of milk, i.e. in the case of 10 reduced milk flow, the control timing will be more extended, while in the case of increased milk flow, the control timing intervals will be shorter. In addition, a valve of this type does not operate abruptly, which is an essential prerequisite for optimizing the milking cycle, but opens 15 and closes rather slowly. Further undesirable variations of. the control timing are caused by ageing of the rubber and the resultant loss of its elasticity.

A modified valve of the type discussed above is described -in 20 n~.\S. Patent .Specification .4441454. In contrast to the valve discussed above, this valve is effective to periodically open and close only the openings communicating with the exterior of the milking cup, i.e. with atmospheric air, while the space below the teat remains in constant commun- ___ ication with the mil}c discharge conduit so that the milk is continuously discharged. In addition to the disadvantages f(N: il5» set forth above, the valves of this type suffer from the| further disadvantage that milk may enter the air inlet passages, resulting in the danger that residual- amounts 30 of milk may remain in the passage, particularly towards the end of the milking operation. As these passages are very thin, the cleaning thereof is rather difficult, and it frequently happens that milk coagulates in the air inlet passage without this occurrence being noticed. If however '35 the entry of air is obstructed or reduced, the vacuum adjacent the tip of the teat tends to fluctuate in a completely uncontrolled and biotechnically undesirable manner, as will be discussed below with reference to fig. 1 of the _ . 208931 ■if! 1 drawings. There exists thus an increased demand for a valve adapted to be readily cleaned, or rather, to operate alii ready in such a manner, if possible, that the formation I of residual milk deposits in the valve is prevented from | 5 occurring from the outset. A valve of this type would on ] the one hand ensure reliable operation under all practical conditions, and would on the other hand meet the strict cleanliness requirements in the field o.f food processing. j 10 Proceeding from a valve of the type defined in the intro- | duction, in a preferred embodiment of which the connecting ! /7 conduit opens into a viewing glass: component below the i - ■, ■ ■ - • milking cup in the form of a drip nose, it had for a long time been a matter of speculation how it were possible that O 15 milk residue deposits were able to form in the upwards extending connecting conduit and possibly also in the even higher located valve communicating therewith. Initially it was assumed that this phenomenon might be brought about by the fact that the end of the connecting conduit formed with the drip nose were not properly installed accurately perpendicular to the milk flow, but rather at a small angle in the direction of the milk flow, so that the milk would be forced into the connection- conduit by kinetic energy. To counter this effect, the valve has been designed with the end of the connecting conduit projecting into the milk flow being cut at an angle, with the thus formed bevelled surface being located downstream of the milk flow. This design did not, however, result in any improvement.

A further assumption as to the cause of the contamination of the valve with milk was based on the following phenom-enon:At the end of the pressure relief phase, as the valve closes against the spring force due to the creation of a vacuum in the pulsator cavity, which occurs already at a ■ 35 pressure of about 10 kPa, the further increase of the vacuum in the pulsator cavity up to a value of about ^5 kPa auses the elastic rubber diaphragm to bulge towards the "lulsator cavity, with the result that the volume of the u 1 :rN' ■ - 203931 1 space between the already closed valve poppet and the diaphragm increases in size and exerts a suction•effect. For eliminating this suction effect, extensive experiments were carried out with diaphragm materials of varying 5 elasticity and with stiffening disks for the side of the diaphragm facing towards the pulsator cavity. None of these experiments led to any appreciable results, however, with regard to the milk aspiration phenomenon.

With the aid of high-speed cinematography, carried out, in fact for a quite different purpose, namely for investigating the so-called backflow or backspray phenomenon, respectively adjacent the tip of the teat, with the aid of a transparent teat cup, it was discovered for the first 15 time that at the end of the suction, phase, the milk, tends to shoot into the connecting conduit leading to. the valve, and frequently also into the valve itself, and to flow back therefrom after an interval of only about 5 - 15 milliseconds. The rapid backflow of the milk through the con-20 necting conduit is obviously caused by the opening of the valve at the beginning of the pressure relief phase and the resultant entry .of air. By adjusting the air inlet valve to an earlier opening time it was possible to achieve a noticable reduction of the backflow of the milk, 25 a particularly early opening of the air inlet valve even resulting in the backflow being wholely avoided. On the/^'qp*' (t other hand, however, a long opening time of the valve, «'v and particularly an early opening instant results in ai| DEC 198$ unacceptable impairment of the function of the entire \» ' 0 periodic air inlet system. Now the vacuotechnical and bio^> technical optimum, which is very sharply defined, lies in. the range of a later opening time.' For this reason, an adjustment of the valve to an earlier opening time was not conducive to a solution of the problem under discussion.

There remains the problem as to how the backflow of the milk into the air inlet valve might be explained. In a milking apparatus with periodic admission of air, if the 7 203931 1 four air inlet valves are locked in their closed state, the milking vacuum adjacent the tip of the teat develops substantially as shown in fig. 1 of the accompanying drawings, such milking vacuum being represented in this 5 figure in synchronized relationship to the development of the vacuum in the pulsator cavity. Of interest for an explanation of the backflow of the milk into the air inlet. conduit is only the configuration of the two curves (tip of teat.and pulsator cavity) in the cross-hatched areas G 10 and G'. At the end of the suction phase B, the rated vacuum (in this case 0.5 x 10^ Pa) prevails in the pulsator cavity, with substantially the same vacuum prevailing at the tip of the teat. Under these conditions, there is no significant pressure difference acting on the wall of the 15 rubber teat cup, so that the. latter remains in its expanded state due to its elasticity. The vacuum below the tip of the teat propagates through the connecting conduit into the air inlet valve itself. At the beginning of the relief phase C, the rapid disappearance of the vacuum in the 20 pulsator cavity causes the rubber teat cup to collapse and to thus compress the teat milk channel, so that the flow of milk is stopped.,The collapse of the rubber teat cup additionally results in the space below the tip of the teat to decrease in zize. Due to its inherent inertia, however,- the milk contained in the various passages of ,,N the milking apparatus is unable to follow this pumping I effect sufficiently fast by flowing off at an increased » rate. This results in a temporary pressure rise or vacuum .loss, respectively, below.the tip of the teat and in the 30 connecting conduit. With respect to the air connection conduit this implies that the high vacuum (about 0^5x10 Pa) of the suction phase B still prevails in the valve and the adjacent' end of the conduit, while a vacuum of only about 0.15.x 10"* Pa prevails at the drip nose end portion. If at 35 this time there is any milk in the vicinity of the drip nose, it will be aspirated in the direction of the higher vacuum, i.e. towards the valve. The force, of this suction effect depends on the pressure differential and on the ' 208931 8 1 volume of the "vacuum source", that is, mainly on the volume of the interior of the valve with the valve poppet closed. Elimination of the backflow effect thus requires the volume of the "vacuum source" to be reduced to a mini-5 mum or to be, at best, completely reduced to zero.

The requirement that the valve volume be'made as small as possible is opposed, however, by other important reasons.

There is thus always the danger of cow's hairs entering 10 the valve. In order to retain the operability of the valve even in this case, the interior of the valve has to be of • a corresponding size. It is further to be taken into account that the entire milking apparatus is normally cleaned by passing a cleaning liquid therethrough. Under 15 this aspect it is disadvantageous to include small spaces in the flow path, as this cleaning process is better suited for cleaning greater cavities or spaces. Finally, extensive experiments under laboratory conditions and short- and, §f long-time investigations carried out on a great number of 20 animals of all races have clearly shown that the air- inlet valve should open towards the end of the venting phase and close again at the beginning of the evacuation phase. In a poppet valve the implementation of this actuation timing depends primarily on the effective diaphragm area, on the 25 biasing force and - with regard to the opening time - on the relationship between the effective diaphragm area and ^\ the valve poppet area. If this relationship is selected t<^. * /V o be 1 : 1, the opening vacuum and the closing vacuum are U equal irrespective of any vacuum developed in the valve 1986 during the closed phase between the valve poppet and the diaphragm. The smaller the valve poppet diameter is selected in relation to the effective diameter of the diaphragm, the earlier is the opening time of the valve, while the size of the valve poppet does not have any effect on the closing: of the valve. If the.valve poppet were very small, and if the vaccum in the connecting conduit leading to the air inlet valve were practically equal to the vacuum in the pulsator cavity, the spring acting on the diaphragm would open pv -V ^ -• -. / / 208931 o 1 the valve, as the closing pressure acting on the valve poppet would be substantially less. This could lead so far that the valve opens by itself at the instant at which it closes. By properly selecting the valve poppet diameter in 5 relation to the force of the compression spring and the effective diaphragm area it is possible to accurately adjust the opening time independently of the closign time. . From all these considerations' it appears evident, however, that the valve poppet has to be of relatively great size.. 10 This implies, however, that the requisite sealing between the valve poppet and the valve seat is difficult to achieve due to the large sealing area and a correspondingly low engagement pressure per unit area, particularly in view of the always present danger of contamination. Under 15 these conditions, the parts of the valve have to be finished with high accuracy for ensuring proper operability over an extended period of time. A valve of this type would therefore be very delicate in operation. Finally there is a relatively great volume between the valve poppet and 20 the diaphragm capable of aspirating the milk. It is this particular effect, however, which should be avoided.

In summary it can be said that the milk may enter the air inlet valve primarily due to one . of the following causes: 25 ' If at the end of the milking operation the milking, cup does not hang vertically downwards, as is usually the case, but is at. a more or less inclined position, residual, milk flowing back from the collector piece or from the short milk 30 hose may enter the air inlet conduit, if the latter is not provided with a drip nose.

The same may occur in the case of a very bad - although frequently encountered - milking practice, in which at th 35 end of the mechanical milking operation the residual, milk is manually milked into the milking cup removed from the teat. This practice frequently leads to the formation of a kink in the milk hose between the milking cup and the collector piece. As a result, the milk is retained in the 0 208931 £ $ o no longer vacuum-connected milking cup and escapes to the exterior through the air inlet conduit and the valve, whereby the air inlet system is contaminated unless it is immediately rinsed with water.

Finally it is possible, as discussed above, that milk is temporarily aspirated into the air inlet valve during the normal milking operation due to the vacuum in the interior of the valve.

It is therefore an object of the present invention to provide an air inlet valve of the type defined in the introduction which is capable of being kept clean in the simplest possible manner.

To attain this object in an air inlet valve of the type specified in the introduction, the invention provides the solution that the connecting conduit opens into the valve seat surface. In this manner it is possible, and 20 that irrespective of the size of the interior space between the valve poppet and the diaphragm, to safely prevent milk spray from entering this space, as the valve poppet itself keeps the connecting conduit closed during the full closed phase of the air inlet valve. As the end of 25 the connecting conduit is thusr kept, closed for the period during which a vacuum is generated in the pulsator cavity, there is no corresponding vacuum generated in .the interior of the valve itself during the same period', so that the pressure differential between the exterior of the valve, 30 i. e. atmospheric pressure, and the interior of the valve does practically not vary. In this embodiment of the .valve the interior space thereof can thus not act as the vacuum source referred to above. With regard to the design of the valve poppet it is only of importance to achieve a good 35' sealing action between the valve poppet and the valve seat around the opening of the connecting conduit. The valve ■ seat is therefore preferably designed in such a manner that^-the valve seat surface is solely formed by a sectional ^ <s o m # 11 208931 1 surface of the connecting conduit. The seating of the valve poppet on the outlet end of the connecting conduit in the closed state of the valve results in an additional closing force being exerted on the valve. As a result, the valve 5 opens at a later time than it closes. The timing relation between the opening and closign of the valve may be varied by varying the contact area between the valve poppet and the end surface of the connecting conduit.

The particular design of the valve results in a number of particular advantages. As the valve poppet is preferably of conical shape, a cleaning liquid entering the air inlet; valve from the connecting conduit will at first impinge on the lower surface of the cone and is thereby diverted 15 downwards in the direction of the diaphragm of the valve. This results in an improved cleaning of the diaphragm and of the interior of the valve. A further advantage is to be seen in the fact that in 'the closed position of the valve the valve poppet has to cover only a small hole. This 20 results on the one hand in a high engagement pressure per unit area, and on the other, in a fast closing response of the valve. Since there is only a small opening to be sealed, engagement of the valve poppet with this opening results in the valve itself being sealingly closed. This enables the 25 valve and the timing thereof to be even more accurately controlled. With regard to the service life of the valve it is also of importance that the valve poppet formed as a valve cone has to seal only against.a relatively small area. As the valve poppet itself is rotatable, and will usually 30 be rotated on disassembly and reassembly of the valve, the opening to be closed will always be covered by a new surface portion of the valve poppet. As a result, a punching effect of the valve seat is avoided even if a soft rubber is used for the valve poppet. The use of a soft rubber 35 material is in itself of considerable importance for'the sealing properties of the valve. j I According to A. V f S * isSSK1 \ -* r ■ Vat»/ 20S931 ■«** <£ 12 3 a preferred feature of the invention -the valve poppet is releasably secured to the diaphragm. This permits the valve poppet to be readily dismounted, so that the diaphram and the space between the valve poppet and the diaphragm are readily 5 accessible for particularly effective cleaning. In an embodiment found to be particularly advantageous, the valve poppet, is releasably retained by a snap engagement retaining means secured to the diaphragm. , _ further In a/preferred embodiment the snap engagement retaining means extends through .the diaphragm and is formed with a through opening, and a plunger connected to the valve poppet extends through the snap engagement retaining means so as to project beyond the side of the diaphragm facing 15 towards the pulsator cavity. In this case the valve poppet may be readily dismounted by separating the complete valve with its housing from its connection to the milking cup or collector piece, whereupon the valve poppet is ejected by exerting'pressure on the plunger from the side of the 20 diaphragm facing towards the pulsator cavity.

In a particularly simple design of the snap engagement retainer means, the plunger is formed with an annular recess adapted in the assembled state to be engaged by an annular 25 projection on the interior surface of the through-opening.

In order to facilitate the snap engagement and disengage- ; • ment, the tubular portion of the snap engagement retaining means projecting towards the pulsator cavity is preferably 30 formed with one or several axially extending slots effective to improve its resiliency.

As the valve poppet.is preferably made of a material, for instance rubber, different from that of the plunger, so as 35 to improve its sealing' properties, it may advantageously be formed as a frustoconical member, with the plunger ijT.„the form of a bolt extending axially therethrough. 0 208931 13 1 The accessibility of the space between the valve poppet and the diaphragm is still further improved by the fact that the valve seat surface is formed by the sectional surface of the connecting conduit.

The diaphragm is preferably clampingly retained along its outer edge. This clamping retention is facilitated by providing the diaphragm with an annular bead along its outer edge, so that the diaphragm may be releasably secured by 10 clamping the annular bead.

In this case, a particularly simple retention of the diaphragm is achieved by forming the housing with a first annular groove, and a retainer member releasably secured 15 to the housing with a second annular groove. Optimum sealing properties of the diaphragm and the possibility of readily cleaning the parts retaining the diaphragm ma.y be achieved by forming' the first and second annular grooves as V-shaped key grooves. In this manner it is possible to 20 alway achieve optimum positioning of the diaphragm without any constraint.

In a particularly advantageous embodiment, the retainer member comprises a retainer head cooperating with the housing to form a bayonet coupling and offering the puis- v ation medium access to the diaphragm, and an annular member mounted on the retainer head for rotation about .the axis prior to mounting in trie housing of the bayonet coupling/and formed with the second annular groove.

In order to prevent any shear forces from acting on the diaphragm on closing the retainer head, the annular member..^, is non-rotatable/mounted in the housing for longitudinal^P'^ displacement along the axis of rotation of the bayonet IH .. ■' m..' coupling.

In order to enable the operator to disassemble the air i valve, such as for cleaning purposes, by simple means, for 4 DEC1986*, V 1 instance with the aid of a coin, a further embodiment of the invention provides that the side of the retainer head facing away from the diaphragm is formed with a diametrally extending slot adapted to be engaged by a flat metal object 5 for facilitating rotation of the retainer head.

For permitting the valve to be completely disassembled with a minimum of manual operations, the retainer head is preferably formed with a central opening whereinto the 10 plunger connected to the valve poppet projects to such a degree that the insertion of a flat metal object into; the slot of the retainer head causes the valve poppet to be released from the snap engagement retaining means through the plunger. In this manner it is possible to release the 15 valve poppet from the snap engagement retainer means by the insertion for instance of a coin- into the slot of the retainer head, subsequent rotation of the coin immediately resulting in the diaphragm being, release-d from- its retained state. During this operation the spring continues to be 20 retained either by the diaphragm or by the lower portion.

The invention shall now be explained in detail with refer-ance to an embodiment shown by way of example in the accompanying drawings, wherein: fig. 1 shows a diagram of the vacuum development in the pulsator cavity and adjacent the tip of the teat during two pulse cycles (2 seconds). The lower curve drawn in solid lines represents the case in which ho 30 air is admitted to the milking apparatus and the vacuum in the milk collectign receptacle or in the milking conduits, respectively, is kept constant. The curve drawn in phantom lines represents the vacuum development resulting from the employ of an 35 air inlet valve controleld.in an optimum manaer.

Fig. 2 shows an axially sectioned view of an air inlet valve according to the invention, in which the sectional i:.-v ■™*r^-».»gfla^tiS»¥ErwjF»eor^ ■iT % 208931 plane in the lefthand half of the figure extends substantially perpendicular to the sectional plane in the righthand half thereof. r Shown in fig. 1, as already referred to above, are two curves above one another representing,-in bar, the development of the vacuum-in relation to time (in seconds). The upper curve represents the development of the vacuum in the pulsator cavity. The operating cycle is shown to include 10 four different phases, namely an evacuation phase A, a vacuum phase B, a venting phase C and a pressure phase D. Phases A and B together constitute the suction phase, while phases C and D together constitute the relief phase. Shown in the lower part of fig. 1 in solid lines is the develop-15 ment of the milking vacuum adjacent the tip of the teat. The erratic and biotechnically highly undesirable cyclical fluctuations of the vacuum adjacent the tip of the teat are caused by the uncontrolled back and forth pendulum flow of a body of milk in the riilkign conduits resulting from the 20 -pumping action of the rubber teat cup, and the resultant alternating action of kinetic energy and potential energy. The dotted line K represents the constant vacuum maintained in the collecting bucket for draining the milk from the milking cups. The dotted line H finally shows the controlled 25 and biotechnically desirable development of the milking vacuum adjacent the tip of the teat brought about by the employ of an air inlet valve controlled in an optimum manner. The points E and F on the upper curve indicate the times at which the air inlet valve is opened and closed, 30 respectively. Both points are situated immediately before and beyond respective points at which atmospheric pressure is attained and at which atmospheric pressure is abandoned, respectively. At the same time it is indicated that the air inlet valve preferably opens and closes at a somewhat lower 35 vacuum. The more accurately it is possible to determine the location of the points at which the air inlet valve opens and closes, respectively, and the more abrupt this opening and closing operation is carried out, the more accurately ■fr' 16 203931 1 it is possible to approach the dotted curve in the lower part of fig. 1, this curve representing the development of the milking vacuum adjacent the tip of the teat resulting from the use of an air inlet valve. n Generally indicated at 1 in fig. 2 is an air inlet valve disposed in a housing 2. Housing 2 is adapted to be inserted into a suitably shaped opening formed in the sidewall of a milking cup shell in the direction of arrow A. 10 On such insertion of housing 2, an 0-ring seal not shown in the drawing insertable into a groove 3 is brought into contact with the outer surface of a valve mounting member, in the present case the milking cup shell, while a nose 4 enters the opening of the milking cup shell for engagement 15 with the interior wall surface thereof so as to fixedly retain the housing on the milking cup shell.

Disposed within housing 2 is a diaphragm 5 having a central, opening 6 and provided with an annular bead of square cross-20 sectional shape along its outer edge. Annular bead 7 may of course be of any other cross-sectional shape, for instance a circular shape. A hub-shaped member 8 of a snap engagement retaining means 9 for a valve poppet 10 extends through central opening 6 of diaphragm 5. One end of hub-shaped 25 portion 8 is formed with an annular flange 11. The outer surface'of hub-shaped portion 8 is formed with a shallow annular groove 13 extending up to annular flange 11. For securing diaphragm 5 to snap engagement retaining member 9, central opening 6 of diaphragm 5 is pushed over hub-shaped 30 portion 8 into engagement with annular flange 11, and secured in this position by an annular plate member 14 pushed onto hub-shaped portion 8 into lockingly seated engagement with annular groove .13- In this manner, diaphragm X 5 is securely retained between annular flange 11 and 35 annular plate member 14, so that central opening 6 of diaphragm 5 is sealed in a gas-tight manner after insertion of plunger described below into the snap engagement retainer 203031 17 1 The side of annular plate member 14 facing away from diaphragm 5 is formed with an annular projection or seat 15 for centering a coiled spring 16 to be described.

A valve poppet is formed as a substantially frustoconical member 12 consisting for instance of rubber or the like for improved sealing properties. Frustoconical poppet member 12 is formed with an axially extending center bore 17 and a coaxial counterbore 18 of larger diameter. Inserted through bores 17 and 18 and a further coaxial bore 19 extending . through hub-shaped portion 8 is a plunger-in the shape of a bolt generally indicated at 40. A head portion 41. of plunger bolt 40 is received in counterbore l8.of valve poppet 10. The end 42 of plunger 40 facing towards the pulsator cavity projects beypnd hub-shaped portion 8.

Hub-shaped portion 8 is formed with one or several slots extending in the axial direction to a point or points closely adjacent annular flange 11, only one of these slots being indicated at 43- Slot or slots 43 serve to divide hub-shaped portion 8 into a plurality of axially . extending fingers for improved flexibility of the snap engagement retainer member 9. The interior wall surface of hub-shaped portion 8 is formed with an annular project-44 ion/projecting into bore 19. In the assembled state of th^«^ o valve, projection 44 engages with an annular recess 45 fN formed in plunger 40. OfCI966 In the drawing,- valve poppet 10 is shown in its upper end xa&Lay position, in which a space 20 above diaphragm 5 and a 30 lateral tubular portion 21 opening into space 20 comr)Tunica^e" with the atmosphere. In the lowered position of poppet valve 10, an annular surface 22 the limits of which are indicated by four vertical lines in the cross-sectional view of the drawing, comes into contact with a valve seat 35 23 formed by a surface surrounding the outlet opening 47 of a connecting conduit 48 opening into space 20, annular surface 22 being formed on the frustoconical outer wall 46 of valve poppet 10. As valve poppet 10 is lowered from the 18 208931 1 position shown in fig. 2, it is thus effective to merely interrupt communication of connecting conduit 48 with the atmosphere, while the space 20 within the valve remains at atmospheric pressure.

A hose or tube 49 having one of its ends inserted into tubular portion 21 connects connecting conduit 48 to- a viewing glass tube or the like (not shown.) disposed for instance below the milking cup (mot shown) and wherethrough 10 the milk obtained from the respective teat is drained towards the milking bucket. F.or accurately adjusting the amount of air entering the milk drain conduit through connecting conduit 48 during the opening phase of valve 1, hose or tube 49 is provided with a. calibrated restriction 15 50. For limiting the flow rate of the air through ttee.: narrowest passage 51 of restriction 50, the latter is designed in the form of a venturi nozzle. This nozzle should nevertheless be located as closely as possible to valve 1 , so that the flow rate of the air is reduced as far as possible 20 before the air flow combines with-the milk to be drained. This may be of importance with regard to the milk's content of free fatty acids and thus for the overall quality of the milk.

Diaphragm 5 is secured by having its annular bead 7 clamped within housing 2. provided for this purpose is a retainer head 25 designed in the form of an annular dish-shaped member having a central opening 26. Formed around opening 26 is a plurality of projections 27 directed in-30 wards in opposition to diaphragm 5, only one such projection being shown in the drawing. The outer surfaces of pro-• jections 27 preferably serve for coaxially guiding the already mentioned coiled spring 16. In the embodiment shown in fig. 2, however, the end of the substantially conical '35 coiled spring.16 facing away from diaphragm 5 is seated in an annular groove 52 formed in the bottom of dish-shaped 208931 19 1 In the embodiment shown, retainer head 25 is formed in the manner of a bayonet coupling. To this purpose retainer head 25 is integrally formed with radially outwards projecting lugs 28 only one of which is shown in the drawing. 5 in the locked position of retainer head 25, lugs 28 are adapted to engage projections 29 formed in housing 29. The. retainer head may of course also be formed with exterior threads for engagement with interior screw' threads formed in the housing. • Supported on the rim 30 of retainer head 25 facing towards diaphragm 5 is an annular member 31 having an annular extension wall 32 facing away from diaphragm 5 and formed - with a radially outwards directed annular projection 33 for engagement with a corresponding annular recess 34 formed. in the interior wall surface of retainer head 25. In this manner annular member 31 is rotatably supported on the before mounting in the housing upper rim 30 of retainer head 25/ The outer periphery of annular member 31 is formed with at least one longitudin- ally extending, lug-shaped projection 35 received in a slot 36 formed in the interior wall surfa.ee of housing 2, so wnen mounted in the housing that annular member 31/is prevented from rotating about its axis of symmetry while being axially displaceable within housing 2.

Annular member 31 is further formed with an annular key groove 37 of V-shaped cross-sectional configuration for receiving annular bead 7 of diaphragm 5 therein. Facing this first annular key groove is a corresponding annular 30 key groove 38 formed in housing 2. The two key grooves 37 and 38 serve to retain annular bead 7 of diaphragm 5 therebetween .

For facilitating opening and closing the retainer head 25 35 with the aid for instance of a coin, the side of retainer head 25 facing away from diaphragm 5 is formed With a diametral ly extending slot 39 shown only in the lefthand portion of fig. 2 due to the 90° offset angle of the two sect- - V : ■V". • ' : V 'S i' \■ > ^ - -■l: ■■ 7; «. >/ " ■ ■ v;.. 308981 . /■ 'fe: o 0 1 ional planes.

The end portion 42 of plunger 40 projects into the path of slot 39 to such a degree that a coin or the like in-5 serted into slot '39 is operable to exert a pressure on end portion 42 for shifting plunger 40 upwards so as to be released from snap engagement retaining member 9.

O For cleaning purposes the described air inlet valve may be disassembled in the following manner: Proceeding from the assembled state of the valve shown in fig. 2, sufficient pressure may be exerted on lower end portion 42 of plunger 40 to release the plunger itself and thus the complete valve poppet 10 from its engagement with snap engagement 15 retainer member 9- Plunger 40 may then- be lifted out of housing 2 together with valve poppet 10. This gives access to space 20 above diaphragm 5 and to the interior of connecting conduit 48 with tubular portion 21 from inside of housing 2, so that the valve components exposed to atmo--20 spheric air can be thoroughly cleaned.

If the air inlet valve is to be completely disassembled, a coin or the like inserted into slot 39 may be used for rotating retainer head 25 about its. symmetry axis so that 25 lugs 28 become disengaged from projections 29- In this manner retainer head 25 is rotated relative to both housing 2 and annular member 31 - Lug-shaped projections 39 prevent annular member 31 itself from being rotated, so that diaphragm 5 is not subjected to any shearing forces. As soon 30 as lugs 28 of retainer head 25 are disengaged from projections 29, the complete retainer head 25 together with annular member 31 may be withdrawn downwards from housing 2, with lug-shaped projections 35 of annular member 31 being guided in slots 36. As a result of the described operation, annular 35 bead 7 of diaphragm 5 is released from its clamped state, so that diaphragm 5 may now be removed from housing 2 together with snap engagement retaining member 9 and annular plate member 14 securing the retaining member t V ■ ' > V • >* 208^31 21 1 the diaphragm.

Reassembly of the thoroughly cleaned air inlet valve is accomplished by carrying out the above steps in inverse 5 sequence. ' In a preferred embodiment of the described valve, restriction 50' is located as closely as possible to the outlet openign 47 of connecting conduit 48, so as to reduce the 10 volume of the connecting conduit 48 between its outlet opening and the restriction to a minimum.

For preventing valve poppet from coming into contact with the valve seat surface only at a single point, which might 15 otherwise result in undesirable tilting of the valve. poppet, the interior space 20 of the valve is preferably provided with one or two axially extending partitions 53 only one of which is shown in the figure in dotted lines, each partition being formed with a seat surface 54 for 20 engagement with the surface 46 of valve poppet 10. /<* ^ ' 0\ 1 .\ t"- ..-a ■ W 22 S08931

Claims (18)

WHAT WE CLAIM IS: © o

1. An air inlet valve for admitting air to the milk discharge conduit of a teat cup or collector piece, comprising a housing secured to said teat cup or collector piece, a diaphragm clamped within said housing, a valve poppet secured to said diaphragm so as to project from one side thereof, a valve seat cooperating with said valve poppet to form a valve adapted to open and close in response to pressure produced by a pulsator and acting on the other side of said diaphragm and a conduit connecting the milk discharge conduit with an opening provided on said one side of the diaphragm and bounded by said valve seat, and in which the pulsator pressure is arranged to open the valve to admit atmospheric air into the milk discharge conduit via said connecting conduit.

2. A valve according to claim 1, characterized in that said valve seat surface is formed by a sectional surface of said connecting conduit.

3. An air inlet valve as claimed in claim 1 or 2 in which said valve poppet is releasably secured to said diaphragm.

4. A valve according to claim 3, characterized in that said valve poppet is releasably retained in a snap engagement retainer means secured to said diaphragm.

5. A valve according to claim 4, characterized in that said snap engagement retainer means extends through said diaphragm and is formed with a through-opening, and in that a plunger connected to said valve poppet projects through said snap engagement retainer means beyond the side of said diaphragm facing towards a pulsator cavity.

6. A valve according to claim 5, characterized in that said plunger is formed with an annular recess adapted in the retained state to be engaged by an annular projection on the inner surface of said through-opening of said snap engagement retainer means. 23 203931

7. A valve according to claim 6, characterized in that a hub-shaped portion of said snap engagement retaining means projecting on the side towards said pulsator cavity is formed with one or more axially extending slots for increasings its resiliency.

8. A valve according to any of claims 5 to 7, characterized in that said valve poppet is formed as a substantially frustoconical member with said plunger in the form of a bolt extending axially therethrough.

9. A valve according to any of claims 3 to 8, characterized in that said valve poppet consists of a rubber material.

10. A valve according to any of claims 3 to 9, characterized in that said diaphragm is clampingly retained along its outer edge.' . . I'r:'l

11. A valve according to claim 10, characterized in that said diaphragm has its outer edge formed with an annular bead and is releasably retained in said housing by having said annular bead clamped therein.

12. A valve according to claim. 10 or 11, characterized in that said housing is formed with a first annular groove and a retainer member releasably secured to said housing is formed with a second annular groove for retaining said diaphragm.

13. A valve according to claim 12, characterized in that said first and second annular grooves are formed as V-shaped key grooves.

14. A valve according to claim 12 or 13, characterized in that said retainer member comprises a retainer head cooperating with said housing to form a bayonet coupling therewith and permitting the access of a pulsation medium to said diaphragm, and an annular member mounted on said retainer head such as to be rotatable about the axis of said bayonet coupling whe^fTw^ . : //% ^ not coupled with said housing and formed with said secon^, annular groove. _ ■4DSCW ...... . - " " y >- --A,.. ~. 24 203931

15. A valve according to claim 14, characterized in that said annular member when mounted in said housing is non-rotatable and capable of longitudinal displacement along the axis of rotation of said bayonet coupling.

16. A valve according to claim 14 or 15, characterized in that the side of the retaining head facing away from said diaphragm is formed with a diamterally extending slot adapted to be engaged by a flat metal object for facilitating rotation of said retaining head.

17. A valve according to claim 16, characterized in that said retainer head is formed with a central opening whereinto the plunger connected to said valve poppet projects to such a degree that the insertion of a flat metal object into said slot of said retainer head causes said valve poppet to be released from said snap engagement retaining means through said plunger.

18. An air inlet valve for admitting air to the milk discharge conduit of a teat cup or.collector piece substantially as herein described with reference,to Figure 2 of the accompanying drawings..