EP0575608A1

EP0575608A1 - Automatic milking device

Info

Publication number: EP0575608A1
Application number: EP19930904384
Authority: EP
Inventors: Pieter Adriaan Oosterling; Erik Arnoldus Aurik
Original assignee: Prolion BV
Current assignee: Prolion BV
Priority date: 1992-01-13
Filing date: 1993-01-13
Publication date: 1993-12-29
Also published as: JP2761808B2; JPH06506363A; NL9200051A; WO1993013651A2; WO1993013651A3

Abstract

Dispositif de traite comportant un emplacement (1a, 1b) de traite sensiblement rectangulaire et destiné à l'animal à traire, une auge (2) située sur un côté, une barrière (3) limitant ledit emplacement (1a, 1b) le long d'au moins un côté, un bras (4) de traite servant à supporter un gobelet trayeur (5) et un bras de détection (7) pourvu d'au moins un détecteur (8) et servant à détecter le pis de l'animal à traire. La barrière (3) possède une partie (11) battante et commandée, de façon à constituer l'entrée de l'emplacement (1a, 1b) de traite, ainsi qu'une deuxième partie battante (12) constituant la sortie dudit emplacement. Un groupe amélioré de gobelets trayeurs (5) est guidé par trois détecteurs (8, 81, 82) servant à déterminer le pis de référence, ainsi que la position des trois autres pis par rapport au pis de référence.Milking device comprising a substantially rectangular milking location (1a, 1b) intended for the milking animal, a trough (2) located on one side, a barrier (3) limiting said location (1a, 1b) along '' at least one side, a milking arm (4) serving to support a teat cup (5) and a detection arm (7) provided with at least one detector (8) and serving to detect the udder of the animal to milk. The barrier (3) has a hinged and controlled part (11), so as to constitute the entrance to the location (1a, 1b) for milking, as well as a second hinged part (12) constituting the exit from said location. An improved group of teat cups (5) is guided by three detectors (8, 81, 82) for determining the reference udder, as well as the position of the other three udders relative to the reference udder.

Description

AUTOMATIC MILKING DEVICE

The invention relates to a milking device provide * 5 with a substantially rectangular milking location for the animal for milking, a feed trough arranged on one side, a fence bounding the milking location along at least one side, a milking arm for supporting a teat cup and a sensor arm provided with at least one sensor for detecting the teat of

10 the animal for milking.

Such a device is used for automatic milking of dairy cattle, in particular cows, wherein the animal is constrained at the milking location into the correct position, whereafter the correct position of the or each

15 teat is determined by means of the sensors for automatic arranging of the teat cups. The animal is lured to the milking location by supplying feed into the feed trough. If however the animal may not be milked, it may obstruct access to the milking location for other animals. It also occurs

20 that after milking the cow remains standing at the milking location and thereby blocks the milking location for an unnecessarily long time.

The invention has for its object to obviate the above stated drawbacks and provides for this purpose a

25 milking location which is distinguished in that the fence has a driven swingable part to form the entrance to the milking location in addition to a second swing-away part to form the exit thereof. Thus is achieved that holding the fences constantly open results in a walk-through system so

30 that when the cow is not allowed entry it can again leave the milking location unobstructed. The swinging fence part can moreover serve to compel the cow out of the milking location again.

According to a feature of the invention the floor

35 of the milking location is moreover divided into portions having an unequal height in order to place the cow in the correct milking position. According to another feature the feed trough at the milking location is provided with holding and constraining means for respectively positioning and pushing away the head of the cow.

The invention also relates to an improved disposition of the sensor means, wherein the invention proposes to place two sensors on the sensor arm for determining a reference teat in addition to a third sensor movable independently thereof for determining the position of the remaining teats relative to the reference teat.

The invention further relates to an improved teat cup which can be supported by the milking arm for pivoting in all directions. It is thereby possible to guide the teat cup more accurately to the teat. If use is made of four teat cups for the four teats of a cow, each teat cup can be controlled independently. According to a feature of the invention, when a teat cup is driven it is first locked in a horizontal plane relative to the milking arm, wherein only the vertical movement of the teat cup relative to the arm remains possible. Above mentioned and other features of the invention will be further elucidated in the figure description hereinbelow of a number of embodiments. In the drawing:

Fig. 1 shows a perspective side view of two milking locations situated in line with one another, each provided with an associated milking arm and provided with a common sensor arm, fig. 2 is a top view of a milking location with fences according to the invention disposed therearound, fig. 3 is a standing front view of the feed trough along the line III-III in fig. 2 provided with constraining means according to the invention, fig. 4 shows a perspective view of the floor in the milking location according to the invention, fig. 5 shows a perspective view of a group of teat cups on the milking arm according to the invention, and provided with a connection diagram thereto, fig. 6a and b show respectively a top and side view of the suspension of each parallel arm of a teat cup to the milking arm, fig. 7 is an upright section of a teat cup according to the invention suspended from a parallel guide, fig. 8 is a section through the valve block along the line VIII-VIII in fig. 5, fig. 9 shows a perspective view of the sensor arm according to the invention applied in the device of fig. 1, fig. 10 shows a preferred disposition of the sensors on the sensor arm in fig. 9 in relation to a reference teat, fig. 11 is an upright section through a third sensor on the sensor arm of fig. 9, fig. 12 is an upright section of a second embodiment of the teat cup according to the invention, fig. 13 is a perspective view of an IC foil sensor for a teat cup, fig. 14 shows a perspective view of another teat cup connection, fig. 15 is an upright front view of another feed trough.

Shown in fig. 1 are two milking locations la and lb, into each of which the cow can step freely and walk away, wherein the associated control determines whether the cow will be milked or not. In the latter case the cow will also not receive any feed lure in the feed trough 2 belonging to each location. Forming part of each milking location is a fence 3, the details of which are further elucidated in fig. 2. It is noted that the feed trough 2 is arranged reciprocally movable in the direction of arrow Pi relative to the milking location, the function of which will be further explained hereinbelow.

Each milking location is embodied with a milking arm 4 which is provided on the free end with a milking rack with teat cups 5. A carriage 6 can travel along both milking locations la and lb, on which carriage is placed a sensor arm 7 provided with sensors 8 in addition to a gripper which can grip the free end of milking arm 4 and place it in the correct position relative to the cow. The carriage 6 is dis- placeable and lockable on the associated rail 9 as soon as it has arrived in the correct position in relation to the milking location la respectively lb. The above mentioned coupling and guiding of the milking arm 4 takes place in the locked situation.

Milking at the milking location takes place by means of a teat cup for placing on each teat, which with a pneumatic control system (not shown) ensures that the teat is massaged, whereafter the milk can be carried away into a milk discharge system provided with filters, cooling and such components, this being further elucidated hereinbelow. It is recommended to arrange an ultrasonic presence sensor at each milking location in order to detect the presence of the cow. Such an ultrasonic presence sensor has the advantage that the feature of ultrasonic reflection is used, contrary to for instance light reflection. This results in less malfunction due to pollution or dirt and moisture. Contrary to the usual way of ultrasonic detection, the lack of reflection will be detected, as the cow being in the beam of rays will absorb that beam, so hindering that objects, as a metal fence, reflecting the sound very strong, will reflect a signal to the sensor. The lack of such a reflection is the detection of the presence of a cow.

Shown in fig. 2 is a preferred embodiment of a fence 3 round the milking location 1, which fence 3 consists of a fixed part 10 along at least one side which adjoins the feed trough 2 and a side opposite the feed trough 2. Arranged along the second long side is a central fixed part 10• , wherein the front and rear portion have respectively a swing fence 11 and an articulated fence 12. Each movable fence part is fastened hingeably to the central portion 10' and can be carried by means of cylinders 12 from an open position to a closed position. It is specifically the case for the swinging fence part 11 that not only can it be placed in the closed position but it can also be swung through into the space bounded by the fence and to a position over the floor part of the milking location, see position A.

Arranged opposite the swinging fence part 11 is a pivotable fence part 13 which can be carried by means of a gas spring 14 or the like from a position parallel to the fixed fence 10 to a position more above the floor of the milking location. This position is bounded by an adjustable stop. This ensures that the hind portion of the cow is pres¬ sed to the side such that the hind legs of the cow come to stand on the rear floor portion, which is indicated with 14 in fig. 4. Ensured in this manner is that when the milking arm swivels inward from the nominal position it comes as close as possible to the udder for further localisation therefor. Subject to the milking period, it is determined by the recognition transmitter of the cow whether the exit fence 12 remains in the closed position, if milking is required, or whether it must be opened according to arrow P2 by energizing the associated cylinder in order to provide the cow with the opportunity to walk out of the milking location.

This departure is stimulated by pressing the cow outward with the swinging fence part 11 so that the efficient occupancy of the milking location can be increased. When the milking location is empty the fence part 11 then swings back into the position B in order to open the entrance for the following cow.

If the cow has to be milked the fence part 12 remains closed and the feed trough 2 will be made accessible to the head of the animal such that this is held fast between a holding member 15 and a constraining member 16. The space between these two members is such that the cow can feed freely from the trough. During this period the cow is milked, which is further elucidated hereinafter. When milking is completed, the cow has to be removed from the feed trough, whereby the holding member 15 is swivelled upward round the pin 17 in the direction of arrow P3 and the constraining member 16 is swivelled to the left round, pin 18 as according to the arrow P4, see fig. 3. The head of the cow can swing outward to the left in the direction of the fence 12, while the feed trough is closed off by the grating-like end portion 19 of the constraining member 16. The feed trough is simultaneously moved forward whereby the outflow opening is made as large as possible. Forcing the cow out of the milking location can take place in the above described manner by means of the swing fence 11. In the meantime the fence 12 is then opened. In fig. 15 an improved embodiment of the feed trough as described hereabove is shown _r wherein the guiding 122 is added, in order to force the head of the cow upwardly out of the feed trough, and during the eating is locked up between the guiding 122 and the constraining member 16. In order to improve the position of the cow in the milking location so that the udders become easily accessible, the front floor portion 20 on which the front legs of the animal come to stand is set higher than the rear floor portion 14 , see fig. 4. It can be advantageous to adjust the height of the front floor portion 20, either to a height adjusted beforehand for a certain cow, or to a height adjusted afterwards during the positioning of the cow in the event that the installation of the milking rack is difficult due to a bad accessibility of the udder.

It can occur that the cow places its hind legs on the central floor portion 21 which lies at the same level as the rear floor portion 14 during the entry phase. During milking the floor portion 21 can be carried downward in a manner not further specified, whereby the cow will automatically place its hind legs on the portion 14. At the end of the milking period the floor portion 21 can be returned again to the position drawn in fig. 4 in full lines. It is noted that the floor portion 14 is profiled to form two discrete places 14' for supporting the hooves of the animal. The position of these places 14' is such that an optimum milking position of the animal is obtained. To preventing that the cow is touched or damaged by the installation mechanismes for the teat cups, a safety sensor can be arranged, signaling whether the cow has placed

^•f her leg on an unsafe location, for instance the intermediate 5 floor portion at the side of the installation mechanismes. When the sensor signals the leg on such a place the installation of the teat cups is retarded and the cow is stimulated to relocate her legs for instance to moving the feed trough 2 back and forth in the direction PI.

10 It is remarked that the holding member 15 is formed such that the cow is compelled to bend its back slightly, whereby the udder becomes better accessible.

The locking up of the cow above the feed trough is necessary to prevent that the cow is looking backwards, so

15 bending her back whereby the direction of the udder is not in line of the milking box. However, locking up a cow in this position is very disadvantageous, as nervous animals can damage the fence. It is better to arrange the holding member 15 yieldably, such that the cow is able to push the

20 member away and to withdraw her head. In practice additional measures are necessary, as the cow is not able to reach the food again and she will be agitated. Therefore it is necessary to adapt the control of the holding member 15 opening said member as the cow has withdrawn her head.

25 Hereupon the cow has the opportunity to bring back her head in the feed trough again, whereupon she will be locked up again by the holding member 15, and the location of the teat cups can be continued.

It is further noted that on the side opposite the

30 feed trough a manure plate 25 can be arranged which prevents dirtying of the adjacent area. The manure plate is provided with a manure gutter 26 which leads to the grating at the rear of the floor portion of the milking location.

In the context of forcing out the cow, this manure 35 plate 25 can moreover be provided with spray nozzles for directing an air flow onto the hind parts of the cow in order to stimulate it to leave the milking location. There now follows a description with reference to fig. 5 onward of the milking rack with the teat cups which is arranged on the free end of the milking arm 4. In the figure the milking arm 4 is shown schematically but can be an articulated arm with the purpose of carrying the milking rack 5 into the correct position under the cow above the floor of the milking location.

According to the invention the milking rack 5 is provided with four teat cups 26, the upright section of which is shown in further detail in fig. 7.

According to the invention each teat cup is supported by two tubular rods 27 and 28 lying one above the other, which tube 27 serves to carry away the milk and which tube 28 serves to apply vacuum in the teat cup. Close to the teat cup 26 the tubes are mutually connected by a rubber coupling piece 29 which forms an all-directional hinge within determined limits so that the opening of the teat cup can orient itself to the position of the teat, see also fig. 7. The milking rack 5 is provided with supports 30 lying one above another which have a V-shaped form and in which can be received the swivel pin 31 of a fork 32 which is fixed to the end of each tube 27 respectively 28, see fig. 6a and 6b. The pin 31 can be pressed into the apex of the V by means of the piston rod 33 of a pneumatic cylinder 34 which is received in the milking rack 5.

The lower rod 27 can be moved up and downward in the direction of arrow P5 by a pneumatic cylinder 35.

When the cylinder 34 is not energized the piston rod 32 will retract and the pin 31 can swing freely in the horizontal plane in the V-shaped suspension bracket 30 as according to the arrow P6. This ensures that each teat cup is freely movable in both the horizontal and vertical planes. Should a cup have to placed on a teat, however, the cylinder 34 is temporarily energized and the parallel guide 27, 28 of the teat cup is temporarily locked in the horizontal plane in a position which is shown with a full line in fig. 6b. With the movement of the milking rack 5 the teat cup 26 can thus be placed in the correct position, the teat located and received in the opening of the teat cup by lifting the teat cup 26 due to energizing of the cylinder 35, whereby the parallel guide moves upward.

As soon as the teat is received in the teat cup 26 the cylinder 34 are reversed whereby the pins 31 can again move freely in the V-shaped bracket. When the milking rack is displaced a teat cup therefore remains suspended freely movable on a teat.

Due to this construction the moving parts hanging on the udder are kept as light as possible whereby the cups can follow well the movements of the udder and the teat.

It is noted that the milking arm 4 is supported by means of a gas spring 87 so that the cow, if necessary, can kick away the milking rack 5 in the case of distress without this resulting in damage to the components.

As stated above, the tubular parallel rods 27, 28 lead to the teat cup 26 via the intermediate rubber hinge 29.

As is known, the teat cup consists of a metal cylinder 40 which is built up of different mutually fitting cylindrical parts. On the inside a rubber sleeve 41 is arranged for receiving the teat. The space between the rubber sleeve 41 and the cylinder 40 forms the vacuum space which is connected to the top connecting tube 28 so that a pulsating vacuum can be applied in this space, which is assumed to be known. As a result of this vacuum the sleeve 41 undergoes a deformation which exerts a massaging action on the teat, whereby milking is initiated. The milk is collected in the space located inside the sleeve 41 and communicates with the lower tube 27 of the parallel guide. Placed in the bottom of the space under the teat cup is a temperature and conductivity sensor 42 which is used to establish whether any of the udder quarters is infected with mastitis. This sensor is connected to the control circuit of the device via cable 43.

Close to the opening in the upper part of the teat cup 26 an inductively operating detecting sensor 44 is placed which consists of an IC foil which can be bent easily round the rubber sleeve 41. This IC foil sensor is connected to the machine control system via cable 45. The selected induction frequency is adapted to the object for measuring and is set here at roughly 1MHz. The rubber sleeve 41 continues above the intake opening of the teat cup 26 as a downward oriented collar 46 which at the same time fixedly holds a protective sleeve 47. This latter is provided in axial sense with a channel through which can be passed a conduit 48 which debouches in an opening 49 at the intake of the teat cup 26. This conduit 48 can be connected to an air pressure system as well as a flushing liquid system, on the one hand to release the teat from the inner wall of the sleeve 41 when the teat cup is disengaged and on the other to flush and therefore clean both the teat and the inside of sleeve 41 when the cup is arranged. It will be apparent that this flushing system can only be set into operation when the approach sensor 44 detects the presence of a teat. To encourage the delivery of milk the flushing water is pre-heated to about body temperature. A circulation system coming close to the teat cups is necessary for this purpose, otherwise there is not sufficient warm flushing water within a few seconds.

Fig. 12 and 13 show an improved embodiment of the teat cup, in which the amendments comprise a variant of the IC foil sensor, the application of a common cup sleeve and use of other materials. The common cup sleeve 102 having axis 103 is mounted by means of an extension 116 in the teat cup 105, wherein the upper edge 101 is placed in a usual way around the upper edge. The cup sleeve has possibly some adaptions, as a tube fitting 113 similar to the earlier described tube 48. Also a sound barrier 104, assuring that no hissing noise will occur by preventing air leaking along the teat can be arranged as additional on the common cup sleeve. Said sound barrier can be integrated with a cover over the whole upper part of the teat cup, so protecting all tubes and electronics against corrosive influences.

The teat cup 105 is adapted to the combination with the IC foil sensor 106, 115. It has appeared that for a correct functioning of the sleeve 102 sufficient space is arranged around said sleeve, for instance at least 2mm, such that during massaging of a short or thin teat the sleeve can deform without contacting the inner wall of the teat cup or the sensor. It has appeared also that it is disadvantageous to place the IC foil sensor 106, 115 in the vacuum space, as it is detrimental to expose said foil to humid and aggressive circumstances due to said vacuum. In the improved embodiment the IC foil sensor 106, 115 is located around the thin outer wall of the teat cup, wherein the teat cup 105 is made from plastic being electro-magnetic neutral, so allowing an undisturbed emission of electro-magnetic radiation from the sensor surfaces 114 to the teat. In order to protect the surrounding against said radiation, a metal ring 107 is arranged around the IC foil sensor 106. It has appeared that the sensor will function only when the ring 107 is connected to the electronic circuit of the IC foil sensor. The sensor itself functions only while the sensor surfaces 114 act as capacitive electrodes, inbetween the teat tissue is placed. The capacitive electrodes are charged with an alternative current having 40 kHz frequency. The electronic circuit connected to the IC foil detects the chains in the dielectrical constant of the medium inbetween the sensor surfaces 114. The electronic circuit is connect by means of a cable 110 with a control system.

The IC foil sensor is placed and casted inbetween the metal ring 107 and the plastic cover, wherein the casting 111 assures that the sensor will not be in contact with the aggressive circumstances in the vacuum space. The teat cup is connected to the milking system in the way as described above, wherein the lower tube 29 having the exit passage 108 is connected to the extension 116. Said extension 116 is provided with a temperature and conductivity sensor 112, similar to the sensor 42. The upper tube 28 is connected to the vacuum space by means of a connection 109. In fig. 14 an improved mounting of the teat cup is shown, wherein flexible connection means 117 and 118 are connected to the rectangular connecting pieces 120 and 121 provided with a resilient pin 119.

A further advantage of the plastic teat cup 105 is the lower weight, whereby the teat cup will not easily disconnect from the teat when during milking the teat will be more flaccid. To provide the teat sensor 106 with two sensor surfaces it is possible to detect the lowering of the teat cup with respect to the teat and to replace the cup in the way as described herebelow. It is remarked that during milking the teats can change shape, whereby the teat cups have a tendency to slide off them. To prevent this the teat cups can be pushed upward each time by energizing the cylinder 35 of the parallel guide 27, 28. Since both milk and flushing liquid are discharged via tube 27, this has to be separated in the milk processing system. To this end the milking rack 5 carries a valve block 50, see fig. 5, which is shown in cross section in fig. 8. Each teat cup 26 communicates via tube 27 and flexible con- duit 51 with two chambers in the valve block 50. The two chambers 52 and 53 respectively each have an outlet opening 54 and 55 which are in communication with a manifold conduit 56 and 57 on either side of the milking rack 5 which leads to a collection tank for the milk 58 and a collection tank for the flushing liquid 59.

The chamber 52, 53 is in each case divided by a diaphragm valve 60 which is embodied here as a continuous web with eight valves for the four teat cups, which web is clamped in suitable manner between an upper and lower shell of valve housing 50. Each chamber is therefore divided into a liquid part on the underside of the diaphragm valve 60 and a gas side on the upper side thereof. Through pneumatic operation of the valves by means of the feed conduit 61, which communicates via electrically operated valves 62 and branch lines 63 with the gas side of chambers 52 and 53, each diaphragm valve 60 can be periodically placed under pressure, respectively released. The valve can therefore periodically close the respective openings 54 and 55. Depending on whether flushing liquid is carried into the valve via conduit 51 or milk for processing, the diaphragm valve 60 closes off respectively opening 54, 55.

Shown in fig. 5 is the pneumatic discharge system for the milk and liquid. A pump 70 driven by a motor M provides an underpressure in the conduit 71 which applies underpressure in the gas side of the valve housing 50 as well as in the tank for the flushing liquid 59 and the milk tank 58. An alternative possibility of cleaning the teats consists of attaching sprayers in a ring on the outside of each teat cup. Before connecting the teat cup the ring is first arranged round the teat and the teat sprayed clean. Thereafter the teat cup(s) is (are) arranged. In this manner the channel 41 is not soiled with dirt adhered to the teat. Another possibility of removing dirt consists of spraying the udder and automatic wiping and/or drying thereof before the cow enters the milking box. This drying can be done with a mechanically moving surface on which lies an absorbent material. This material may for instance be paper or the like which is on a roll and which is changed after each cow.

The collected milk from tank 58 is guided via a pump 72, a filter 73 and a cooler 74 to a storage tank 75 for further treatment. Because milking takes place all day in an automatic milking system, milk is also being pumped continuously to the storage tank. This makes it necessary for the milk filter to be cleaned continually and this will preferably be an automatically cleaning filter.

It is noted that the vacuum on both sides of the diaphragm valve 60 is practically the same because of the connection to the same vacuum system. Since the vacuum on the top side acts over a greater surface of the diaphragm the latter is pulled loose of the respective openings 54, 55 and control of the flushing liquid and milk respectively can take place in suitable manner.

Driving of the milking rack 5 with teat cups 26 is carried out by the sensor arm 7 with sensors 8 arranged on the carriage 6. This carriage 6 is further shown in fig. 9. The carriage can be displaced along a rail 80 along the milking location la, lb etc. and is clamped fixedly on the rail 80 at a milking location in order to obtain a stable disposition. Control of the sensor arm takes place with servo motors, the control boxes of which are mounted on the carriage. The weight of the arm is compensated pneumatically. The arm has a gripper with which the milking rack is gripped and positioned relative to the arm and therefore relative to the sensors arranged thereon. Placed on the arm are two first sensors 81 in addition to a third sensor 82.

The two first sensors 81 serve to detect a reference teat, that is, one of the four teats of a cow. The third sensor 82 serves to detect the remaining three teats in relation to this reference teat. For this purpose the arm with the milking rack coupled thereon is first carried by the two sensors 81 to the reference teat, whereafter the third sensor 82 is lifted upward between the teats, which is possible because the third sensor 82 is placed on a lifting arm 83.

The lifting arm 83 carries the third sensor, which is further explained in fig. 11, upward until the sensor has measured the underside of the teats. The sensor itself, here for instance an ultrasonic sensor, is held in a housing on the end of the arm 83, wherein a rotatably arranged cover 84 is placed round the housing. The cover is driven by a tooth belt 85 which is driven by a motor 86 arranged on the arm 83.

In the upper part of the cover 84 a reflective mirror 68 is arranged such that the signal emitted by the sensor is reflected in the correct direction to the surrounding teats. The position of these teats can thus be established in relation to the reference teat.

Moreover a bellow sensor is placed on the milking arm. Said bellow sensor is not used to control the arm, but is used as safety to prevent that the connecting system is hindering the cow. Said bellow sensor is mounted on the upper part of the connecting arm, adapted to detect a touch of the connecting arm against the lower side of the bellow. In the case this happens, it means that the other sensors have not detected the udder or teats. The control of the system is signaled to repeat the connecting cyclus and repeatedly disconnection leads to an alarm signal.

The two sensors 81 each consist of a transmitter and a receiver of signals. Forming part of the sensor is a control system which measures the time between transmitting and receiving of the reflected signal. The time duration is all each sensor measures and it can occur that the one sensor measures the reflection of a different teat from the other sensor. This is particularly the case when the front teats lie close together. The control system therefore receives an erroneous position and therefore orients the arm wrongly. In order to prevent this, the desired position of the reference teat is selected s ch that this teat in this position always lies closest to the sensor. The sensors 81 are therefore arranged on the arm 7 such that an asymmetrical position is obtained relative to the nominal central position of the udder at the milking location. In general the distance between the desired front teat (reference teat) will hereby usually be smaller that the other front teat, whereby the above mentioned control error is prevented. This is achieved by drawing an imaginary line through sensor 82 in lengthwise direction of the milking box and placing both sensors 81 on the same side of this line.

The double sensor consists as stated of a transmitter and a receiver, wherein the time duration is measured between emitting and receiving of the reflection pulse. Since there are two identical sensors which are operated from the same control, it is possible to receive the transmission pulse of a transmitter with both receivers and to process the time duration of both signals. It has been found in practice that, in the case the teat is in a slanting position, one of the two receivers receives better signals than the other. By measuring in each receiver the time duration of the associated transmitter and of the other transmitter it still becomes possible to determine a position. Good guiding can hereby still take place when the teat lies in a considerably slanted position. It is also possible to check whether both sensors are measuring the same object (the desired reference teat) because the time duration of transmitter 1 to receiver 2 must be equal to the time duration of 2 to 1. If there is a difference, the measurement is then ignored. A further refinement can be to equip the receiving circuits of the sensor with electronics with which the transmitter is identified by means of pulse recognition. Incorrect echoes are hereby ignored.

Pulse recognition can be carried out in different manners, for instance emitting two or more pulses having a predetermined interval inbetween. De receiver will react on signals only, inbetween the predetermined interval exists. By this manner disturbing influences of other signals are minimalized.

A further improvement to finding and following the reference teat is obtained by adjusting the sensors 81 in this way that the sensing will take place in a surface other than horizontally. This is in particular advantageous when the teat is not vertically oriented, but forms an angle to the vertical. In this case it is necessary to have an additional control axis of the sensors in order to be able to place the sensors under an angle, wherein for instance said axis is located through both sensors 81. The control of the angle of the sensors is dependent on a certain cow, in which for instance three adjustments are possible. A further possibility is to select a certain adjustment having carried out some measurements by said sensor and to select the optimal adjustment, in order to obtain the best results of measurement.

In the embodiment shown ultrasonic sensors are used as sensors wherein the frequency of the two sensors 81 is preferably 64 kHz, which can nevertheless be increased to 100 kHz. The frequency of the third sensor 82 lies in the range between 300-700 kHz and is preferably 500 kHz. Due to the rugged conditions and the possibility of the cow bending the sensor fastenings, the option has been developed to calibrate the position of the sensors. For this purpose the sensors are carried to a known position and objects similar to teats are detected. The detected position must correspond with the position known in the control. In the case of small variations the known position is corrected with the new one and in the case of large variations this is indicated.

The above described device lends itself admirably to automatic milking of cows which can move freely in a covered yard. Providing feed lure in the milking box causes a problem because several cows are continually being milked and others insufficiently milked. It is then customary to opt for a period after a milking session, for instance 2 to 3 hours, during which a cow is not milked again. Practice has shown that cows then allow themselves to be milked 5 to 7 times a day. This high frequency damages the teats and, moreover, the number of cows which can be milked in a milking box is thereby limited. The extra milk yield resulting from more frequent milking is already reached with 3 or 4 milking sessions per day. By causing each milking session to take place for all cows within a determined time duration for all cows, the udders of all the cows are uniformly loaded, there are no disturbances in the shed and it can be indicated that a cow does not come to be milked. Within each time period the cow is free to go to the milking location. If a cow comes to be milked for a second time during the same period, it is rejected. In preference three milking periods are assigned, while the fourth period is a rest period for the cows during which the installation can be cleaned. It is possible for the time periods to be close together and an overlap of the periods is likewise possible. By causing milking of the cows to take place in periods the behaviour of the cows is easier to follow and action can be undertaken in the case of aberrant behaviour, for instance as a consequence of disease or the like.

Claims

1. Milking device provided with a substantially rectangular milking location for the animal for milking, a feed trough arranged on one side, a fence bounding the milking location along at least one side, a milking arm for supporting a teat cup and a sensor arm provided with at least one sensor for detecting the teat of the animal for milking, characterized in that the fence has a driven swingable part to form the entrance to the milking location in addition to a second swing-away part to form the exit thereof.

2. Milking device as claimed in claim 1, characterized in that the floor of the milking location is divided into portions having an unequal height.

3. Milking device as claimed in claim 2 , characterized in that said floor comprises three portions, the front portion for supporting the front legs of the animal to be milked, is higher than the back portions, the intermediate portion being height-adjustable.

4. Milking device as claimed in claim 2 and 3, characterized in that the upper surface of the back portion of the floor of the milking location is profiled in height for receiving a leg of the animal to be milked, in order to cause a straddling position of the rear legs.

5. Milking device according to one of the previous claims 1-4, characterized in that inbetween the milking location and the feed trough holding and constraining means are arranged for respectively positioning an pushing away the head of the animal to be milked.

6. Milking device as claimed in claim 5, characterized in that said holding and constraining means comprises a pair of downwardly directed arms, each of which is connected to the feed trough by means of an horizontal swivel shaft, and being mutually connected by a linking member such that the angle of rotation of the one arm is greater than that of the other arm.

7. Milking device provided with a rectangular milking location for the animal to be milked, a feed trough located along one side thereof, a fence along the other side of the milking location, a milking arm for supporting the teat cups, a sensor arm provided with at least one sensor to detect the teat of the animal to be milked, characterized in that said arm is provided with two sensors, each of which acts for determining a reference teat of the animal to be milked, wherein a third sensor is arranged, being movable independently with respect to said two sensors for determining the position of the other teats with respect to the reference teat.

8. Milking device as claimed in claim 7, characterized in that said two sensors for determining the reference teat each comprise an emitter and a receiver for signals.

9. Milking device as claimed in claim 8, characterized in that said two sensors for determining the reference teat are positioned a-symmetrical with respect to the nominal intermediate position of the udder on the milking location.

10. Milking device as claimed in claim 7-9, characterized in that the third sensor is respectively emitting and receiving signals in a vertical sense, wherein above the sensor a deflecting member is arranged, being rotatable around the center axis of the sensor.

11. Milking device provided with a substantially rectangular milking location for the animal to be milked, a feed trough located at one side thereof, a fence along the border of at least one side of the milking location, a milking arm for supporting the teat cups, and a sensor arm provided with at least one sensor for detecting the teat of the animal to be milked, characterized in that a set of four milking arms, each for one teat cup, is arranged, said arms being movable independently to each other.

12. Milking device as claimed in claim 11, characterized in that each milking arm is connected via a universal joint with the frame of the device, said universal joint is lockable by locking means in a horizontal plane.

13. Milking device as claimed in claim 12, characterized in that the universal joint is provided with a pair of V-shaped brackets, located above each other, said brackets being adapted to support a pin extending to said V-shaped bracket, said pin being connected to an element of a telescopally working milking arm.

14. Milking device as claimed in claim 13, characterized in that a controlled pressing member acts upon the pin in the direction of the V-shaped bracket.

15. Milking device provided with a substantially reactangular milking location for the animal to be milked, a feed trough located at one side thereof, a fence along at least one side of the milking location, a milking arm for supporting a teat cup, and a sensor arm provided with at least one sensor for detecting the teat of the animal to be milked, characterized in that the teat cup comprises substantially a cylindrical housing of metal, and a sleeve of plastic material inside said housing, wherein inbetween the sleeve and the metal housing a detecting sensor is provided.

16. Milking device as claimed in claim 15, characterized in that the detecting sensor is an inductive sensor.

17. Milking device as claimed in claim 16, characterized in that the detecting sensor comprises a IC-foil.

18. Milking device as claimed in claim 15 upto 17, characterized in that the teat cup is provided with a connection for a flush fluid and for a common drain for the milk and the flush fluid as well, wherein the four teat cups having said fluid drain are connected to a common valve housing.

19. Milking device as claimed in claim 18, characterized in that said common valve housing comprises a lower scale, an upper scale and a membrane tissue as partition between said scales.

20. Method for milking cattle by means of a device according to one of the previous claims, characterized in that three milking periods per day are provided, whereas a fourth period is used as rest period for the animal to be milked.

21. Method according to claim 20, characterized in that said periods are overlapping each other.