One-way gates for animals are arranged to permit passage of animals in one direction but prevent passage of animals in the opposite direction. One-way gates are used, for example, for controlling the cow traffic to and from a milking robot. Simple such one-way gates comprise a gate element hinged to a stationary post located at one side of the one-way gate. The gate element has an extension across substantially the whole width of the passage in a closed position. The gate element is displaceable from a closed position to an open position by a pushing motion of a cow.

However, it could be tempting for a cow to try to pass one-way gates in the wrong direction in order to get, for instance, access to food without passing the milking robot. A relatively large number of the cows of a herd learn to open such simple one-way gates from the wrong side.

A more complicated one-way gate comprises two hinged gate elements, which are independently pivoted from a closed position to an open position by a pushing motion. Such gate elements may be hinged at different levels to a post located at one side of the one-way gate. In the closed position, each of the gate elements

has an extension across substantially the whole width of the passage through the one-way gate. Alternatively, the gate elements may be hinged at the same level to posts located-at different sides of the one-way gate. In this case, each of the gate elements has an extension across substantially half the width of the passage through the one-way gate. In a large herd of cows, at least some of the cows often learn to open such more complicated one-way gates from the wrong side.

SUMMARY OF THE INVENTION The object of the present invention is to provide an one-way gate for animals, which is substantially impossible to pass in the wrong direction for an animal, like a cow, at the same time as the one- way gate has a simple construction such that it is inexpensive to manufacture.

This object is obtained according to the invention by the feature that the gate comprises locking means which are arranged to prevent a movement of the first gate element from the closed position when the second gate element is in the closed position. In order to open a one-way gate having such locking means from the wrong side an animal, like a cow, has to perform a plurality of actions. Initially, the cow has to grip and displace the second gate element from the closed position by the head from the wrong side of the gate. Thereafter, the cow has to grip the first gate element at the same time as it maintains its grip of the second gate element such it can displace the first gate element and the second gate element together to an open position. Consequently, it is considerably more difficult for a cow to open such a one-way gate from the wrong side than a conventional one-way gate having two gate elements. However, only a small numbers of cows learn to open conventional one-way gates having two gate elements from the wrong side. Hence, the number of cows, which will learn to open a one-way gate according to the invention from the wrong side, is negligible. Except for the presence of the locking means,

the one-way gate may have a conventional construction. Since such locking means may be given a reliable function with a relatively simple construction, the costs for manufacturing such a one-way gate become low.

According to a preferred embodiment of the invention, the locking means are arranged to prevent a movement of the first gate element from the closed position until the second gate element has been moved a predetermined distance from the closed position.

Consequently, the cow has to open the second gate element a predetermined distance before the locking means allows a movement of the first gate element from the closed position. By a sufficiently large such distance, the risk that a cow opens the one- way gate from the wrong side is further reduced. The second gate element may be pivotally hinged, wherein the locking means are arranged to prevent a movement of the first gate element from the closed position until the second gate element has been pivoted a predetermined angle from the closed position. Preferably, both the gate elements are pivotally hinged but it is also possible to arrange the gate elements such that they obtain another kind of movement from the closed position, for example, a sliding movement or an oblique movement.

According to a further embodiment of the invention, the first gate element and the second gate element are arranged at different levels. Such gate elements may be arranged in substantially the same vertical plane above each other. In this case, each of the gate elements has in a closed position an extension across substantially the whole width of the passage of the one-way gate.

Advantageously, the first gate element may be arranged at a higher level than the second gate element. Normally, a cow passes a one-way gate with a lowered head. In such a case, the cow first pushes up the lower second gate element and then the upper first gate element. Consequently, the locking means does not in any way prevent a normal passage of a cow through the one-way gate.

On the other hand, the locking means makes it very difficult for a

cow to pass the one-way gate in the wrong direction. In order to open the one-way gate from the wrong side, a cow has first to grip the lower gate element and to pull it from the closed position before it grips the upper gate element and pulls it from the closed position together with the lower gate element.

According to a further embodiment of the invention, the first gate element is arranged in a first vertical plane and the second gate element is arranged in a second vertical plane, wherein said first vertical plane and said second vertical plane are different vertical planes. With such an arrangement of the gate elements, it is even more difficult for a cow to open the gate elements from the wrong side. Preferably, the first gate element and the second gate element are positioned such that an animal, which passes through the one way gate, first passes through said second vertical plane and then through said first vertical plane. Thereby, a cow, which passes through the one-way gate in a natural manner, first gets into contact with the second gate element and moves it from the closed position before the cow gets into contact with the first gate element. Advantageously, the second vertical plane is located at a distance from the first plane, which distance substantially corresponds to said predetermined distance the second gate element has to be moved from the closed position in order to allow a movement of the first gate element from the closed position.

When the second gate element has been displaced said predetermined distance, the cow gets into contact with the first gate element and displaces the first gate element and the second gate element together to an open position. With such an arrangement of the gate elements, it is nearly impossible that a cow fails to open the gate elements during passage of the one-way gate in the right direction.

According to a further embodiment of the invention, the locking means comprises a locking member which is movable to a locked position where it prevents a movement of the first gate element from the closed position and to an unlocked position where it

allows such a movement. Preferably such a locking member may be automatically displaced between the locked and the unlocked position dependent on the position of the first gate element and the second gate element. In such a manner, the locking member may be arranged to be displaced to the locked position by the second gate element when the second gate element is moved to the closed position. Hereby it is guaranteed that the locking member locks the first gate element in the closed position when the second gate element is in the closed position. The surface of the second gate element, which gets into contact with the locking member, may be a surface of an existing part of the second gate element or a surface of a specific part, which has been attached to the second gate element only for this purpose. Preferably, the locking member is displaceable to the unlocked position by gravity. When the second gate element has been displaced a predetermined distance from the closed position, the contact between the surface of the second gate element and the locking member is interrupted. With a suitable construction of the locking member, the locking member drops down from the locked position to the unlocked position by its weight. Such an automatically controlled locking means may have a relatively simple construction.

According to a further embodiment of the invention, the one-way gate comprises a stationary mounted housing, which accommodates the locking member. Such housing could be fixedly attached to, for example, a post to which the gate elements are pivotally attached by suitable hinges. The housing may have inner surfaces, which define a space in which the locking member is displaceable between the locked position and the unlocked position. Preferably, the locking member comprises a locking surface, which is arranged to prevent a movement of the first gate element from the closed position when the locking member is in the locked position. The locking surface may have an extension in parallel with a suitable locking surface of the first gate element.

The locking surface of the first gate element may be a suitable surface of an existing part of the first gate element. Alternatively,

the surface of the first gate element may be a surface of a specific part, which has been attached to the first gate element for this purpose.

According to a further embodiment of the invention, the locking member comprises a first part, which comprises the locking surface, a second part, which comprises a surface arranged to get in contact with the second gate element, and a spring member, which constitutes a resilient connection between the first part and the second part. Thereby, the first part and the second part of the locking member are resiliently arranged in relation to each other.

The first part may comprise an inclined surface, which is arranged to allow a movement of the first gate element to the closed position when the locking member is in the locked position. By such an inclined surface, the first part will be depressed by a surface of the first gate element when it gets in contact with the inclined surface.

Thereby, the first gate element, when it is moved in a direction back to the closed position, is allowed to pass the locking member even when the locking member is in the locked position.

Advantageously, the second part comprises a convex surface, which is arranged to get in contact with the second gate element for the displacement of the locking member to the locked position.

If the second gate element is moved to the closed position in a substantially horizontal direction, the second gate element may be arranged to act on a downwardly protruding convex surface of the second part. Thereby, the second gate element may act on the convex surface of the second part and displace it upwardly to a locked position.

According to a further embodiment of the invention, the one-way gate comprises closing means for moving the first and second gate elements to a closed position. It is important that the gate elements immediately moves back to the closed position after that a cow has passed the one-way gate in order to prevent that an other cow passes the one-way gate in the wrong direction. Such closing means may comprise a spring having an attachment such

that it urges the gate elements to a closed position. Alternatively, said closing means may comprise an inclined support of the hinged gate elements such the gate elements are moved to a closed position by gravity.

BRIEF DESCRIPTION OF THE DRAWINGS In the following, preferred embodiments of the invention are described by examples and with references to the attached drawings, in which Fig. 1 shows a first embodiment of a one-way gate comprising a first gate element and a second gate element, Fig. 2a-d shows sectional views in a plane A-A in Fig. 1 of a locking means when the gate elements are in different positions and Fig. 3 shows a second embodiment of a one-way gate.

BRIEF DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION Fig. 1 shows a one-way gate for animals, which is arranged to permit passage of animals in one direction but prevent passage of animals in the opposite direction. Such one-way gates may be used for controlling the cow traffic to and from a milking robot. The one-way gate comprises a first gate element 1 and a second gate element 2, which gate elements 1,2 are pivotally hinged to move in one direction from a closed position to an open position. The first gate element 1 and the second gate element 2 each comprises a substantially U-shaped tubular part 1 a, 2a and a straight tubular part 1b, 2b. The straight tubular parts 1b, 2b are connected to the ends of the respective U-shaped tubular part 1a, 2a. Thereby, the first gate element 1 and the second gate element 2 have an extension in a substantially vertical plane in a mounted state. In Fig. 1, the first gate element 1 and the second gate

element 2 are arranged in substantially the same vertical plane in the closed position. The first gate element 1 is mounted at a higher level than the second gate element 2. The first gate element 1 and the second gate element 2 have, in the closed position, an extension substantially across a passage through the one-way gate between a first vertical post 3 and a second vertical post 4.

The posts 3,4 are stationary fastened to the ground 5. However, the posts 3,4 may be replaced by suitable wall elements or other stationary elements for suspending the gate elements 1,2.

The first gate element 1 is pivotally hinged in relation to the first vertical post 3 at an upper part of the straight tubular part 1b by a first hinge 6a and at a lower part of the straight tubular part 1 b by a second hinge 6b. The second gate element 2 is pivotally hinged, in a corresponding manner, in relation to the first post 3 at an upper part of the straight tubular part 2b by a third hinge 6c and at the lower part of the straight tubular part 2b by a fourth hinge 6d.

Consequently, each of the first gate element 1 and the second gate element 2 has an end portion, which is pivotally hinged in relation to the first post 3, and a free end portion. The first gate element 1 and the second gate element 2 have an extension between the hinged end portion and a free end portion, which exceeds the distance between the first post 3 and the second post 4. Consequently, the second post 4 constitutes a stop surface for the free end portions of the gate elements 1,2. Thereby, the second post 4 permits a motion of the first gate element 1 and the second gate element 2 from the closed position in one direction only. The gate elements 1,2 are movable from the closed position in the direction of motion of a cow, which passes the one-way gate.

The first gate element 1 is pivotally hinged around an axis defined by the first hinge 6a and the second hinge 6b. Said axis has an inclination in relation to a vertical axis such that the free end portion of the first gate element 1 has it lowest level in the closed position. The second gate element 2 has a corresponding suspension such that the free end portion of the second gate

element 2 has it lowest level in the closed position. Thereby, the first gate element 1 and the second gate element 2 are automatically pivoted back towards the closed position by gravity after that the gate elements 1,2 have been moved from the closed position. According to the invention, the one way-gate comprises locking means 7, which are arranged to make it substantially impossible for a cow to pass the one-way gate in the wrong direction.

Fig. 2a shows a sectional view in the plane A-A of Fig. 1 disclosing said locking means 7, when the first gate element 1 and the second gate element 2 is in a closed position. A lower part of the first gate element 1 and an upper part of the second gate element 2 are visible in Fig. 2a. The locking means 7 comprises a housing 8 having walls, which define an inner space. The housing 8 is fixedly attached to the first post 3 at a surface of a rear wall 8a. A locking member 9 is arranged in the inner space of the housing 8.

The locking member 9 is movably arranged in the housing 8 in a substantially vertical direction. The locking member 9 comprises a first part in the form of a lock bolt 10, a second part in the form of a ball 11, and a spring 12, which constitutes a resilient connection between the lock bolt 10 and the ball 11. The first gate element 1 comprises a fixedly attached downwardly protruding plate member 13.

The first gate element 1 and the second gate element 2 are, in Fig.

2a, in a closed position. In that position, a surface of the second gate element 2 is in contact with the surface of the ball 11, such that the locking member 9 has been displaced upwardly to a locked position. In the locked position, a locking surface 10a of the lock bolt 10 prevents a movement of the first gate element 1 from the closed position. The locking surface 10a prevents the downwardly protruding member 13 of the first gate element 1 to pass. Consequently, the locking means 7 prevents a movement of the first gate element 1 from the closed position when the second gate element 2 is in the closed position. Consequently, the second

gate element 2 has to be opened before it is possible to open the first gate element 1.

In Fig. 2b, the second gate element 9 has been pivoted a predetermined angle from the closed position. In this position of the second gate element 2, the contact between the second gate element 2 and the ball 11 has been interrupted. Thereby, the locking member 9 has fallen down to an unlocked position by gravity. The housing 8 comprises edge portions 8b, which prevent the locking member 9 from falling out of the housing 8. In this position, the lock bolt 10 has been displaced downwardly such that the locking surface 10a is located at a lower level than the protruding member 13 of the first gate element 1. Hence, the locking means 7 does not any longer prevent a movement of the first gate element 1 from the closed position. In fig. 2c, both the first gate element 1 and the second gate element 2 have left the closed position and are now in a more or less open position, in which state an animal may pass the one-way gate.

In Fig. 2d, the second gate element 2 has been pivoted back to the closed position by gravity. The second gate element 2 has displaced the locking member, via the ball 11, upwardly to the locked position. At the same time, the first gate element 1 is pivoted back towards the closed position. The protruding member 13 gets here in contact with an inclined surface 1 Ob of the lock bolt 10, which has a suitable inclination in relation to the direction of motion of the protruding member 13. Since the locking member 9 comprises a spring 12 arranged between the lock bolt 10 and the ball 11, the lock bolt 10 is resiliently retracted by the protruding member 13 in the housing 8. Therefore, the first gate element 1 has the ability to pass back to the closed position also if the locking member 9 has already been displaced to the locked position.

Normally, a cow passes a one-way gate with a lowered head.

During a passage of a one-way gate having a first gate element 1

and a second gate element 2 in different levels, the cow first pushes up the lower gate element 2 and then the upper gate element 1. The function of the locking means 7 is to prevent a movement of the upper first gate element 1 from the closed position until the lower second gate element 2 has been pivoted a predetermined angle from the closed position. Consequently, the locking means 7 has a function, which does not prevent a normal passage through such a one-way gate in the right direction. It is nearly impossible for a cow to pass the one-way gate in the wrong direction. For opening the one-way gate from the wrong side, a cow has first to grip the lower second gate element 2 and displace it towards herself said predetermined distance from the closed position. Thereafter, the cow has to grip the first gate element 1 at the same time as it maintains her grip on the second gate element 2 and to displace the first gate element 1 and second gate element 2 together to an open position. Consequently, it is nearly impossible for a cow to open a one-way gate having such locking means 7 from the wrong side.

Fig 3 shows a second embodiment of a one-way gate according to the invention. The first post 3 has here a shape such that the first gate element 1 is arranged in a first vertical p ! ane Vi in the closed position. The second gate element 2 is arranged in a second vertical plane v2 in the closed position. The second vertical plane v2 differs from said first vertical plane V1. Advantageously, the second post 4, which is not shown in Fig. 3, has a corresponding shape as the first post 3 in order to comprise a stop surface for the first gate element 1 and the second gate element 2 in the closed position. When a cow arrives to the closed gates element 1,2 of the one-way gate, the second vertical plane v2 of the second gate element 2 is located in front of the first vertical plane of the first gate element 1. Thereby, a cow in a-natural manner first gets in contact with the second gate element 2 and moves it from the closed position. When the second gate element 2 has been moved said predetermined distance, the cow gets in contact with the first gate element 1 and displaces the first gate element 1 and the

second gate element 2 together to an open position. With such an arrangement of the first gate element 1 and the second gate element 2, it is nearly impossible that a cow fails to open the gate elements 1,2 from the right side. Furthermore, with this arrangement it is even more difficult for a cow to pass the one-way gate from the wrong side. In this case, the cow first has to reach and grip the lower second gate element 2, which thus is located in a plane v2 behind the plane v1 of the first gate element 1.

The locking means 7 has a substantially corresponding design as the locking means 7 described in Fig. 2a-d. However, the second gate element 2 has here a plate like member 15 arranged at an upper part. The plate like member 15 has an extension such that it is in contact with the ball 11 until the second gate element 2 has been displaced a predetermined distance.

The invention is not limited to the described embodiments but may be varied and modified freely within the scope of the claims. The gate elements may have a substantially arbitrary but functional design such that they in a closed position prevent that animals pass the one-way gate in the wrong direction. The invention is not restricted to two gate elements arranged at different levels. The gate elements may, for example, be arranged at the same level on different sides of the passage. The locking means may have an arbitrary but functional construction, which prevents a movement of the first gate element 1 from the closed position when the second gate element 2 is in the closed position.