Patent Description:
Numerous solutions exist for preventing vermin such as rats from entering specific sections of a sewage pipe system. Among others, the following prior art patent publications exist:.

In particular, it may be seen as an object of the present invention to provide a barrier suitable for installation at least partly in a sewage pipe and for preventing rats or other vermin from passing the barrier that may yield the mentioned advantages with respect to prior art barrier, such as being more reliable and/or efficient.

Thus, the above described object and several other objects are intended to be obtained by a barrier according to independent claim and a method according to independent claim <NUM>.

The invention may be particularly, but not exclusively, advantageous for obtaining a barrier, which may be effective in preventing vermin from passing the barrier in at least one direction, since a locking system with at least two parts are mounted on the barrier, the locking mechanism preventing vermin from being able to open the shutters from the upstream direction, the locking mechanism being shaped and mounted on the barrier so that no vermin would not be able to unlock the locking mechanism and thereby would not be able to enter the pipe system, despite the tendency of vermin to tries assiduously to pass the barriers.

Furthermore, the invention may be particularly, but not exclusively, advantageous for obtaining a barrier, which may be more effective in preventing vermin from passing the barrier in at least one direction, since the parts of the locking mechanism may be exchangeable. The parts of the locking mechanism are possibly existing in a variety of different shapes and dimensions, thereby possibly be exactly suitable for the specific sewage pipe system it is to be installed in.

Furthermore, the invention may be particularly, but not exclusively, advantageous for obtaining a barrier, which may be more reliable, such as not being blocked by organic solid matter and other solid matter in, e.g., a sewage flow, since the shutters and the locking mechanism in the barrier makes a sewage flow in a downstream direction possible, furthermore an edge of the first shutter is possibly smoother than a corresponding edge of the second shutter, whereby the first shutter therefore may be less likely to attract organic solid matter and other solid matter in, e.g., a sewage flow, since such solid matter is less likely to get attached to, such as stick to, the smoother edge.

Furthermore, the invention may be particularly, but not exclusively, advantageous for obtaining a barrier, which may be effective in preventing vermin from passing the barrier in at least one direction, since the barrier makes it possible to alter the orientation of the at least first shutter between a first orientation and a second orientation in the barrier, i.e. positioning the shutter in the one direction or the other direction in the barrier, results in the one and same barrier being applicable for sewage systems, nondependent on whether the vermin may enter one way or the opposite way according to a longitudinal extension of the barrier. The at least first shutter may always be positioned so that the vermin is prevented from entering without the need for different barriers with differently positioned shutters, one barrier for each way of possible entering of the vermin.

It may be seen as an insight of the present inventor, that a more reliable and efficient barrier may be achieved by having a very reliable and durable locking mechanism as a part of the barrier. The locking mechanism making sure, that no vermin can pass the barrier in an upstream direction, simultaneously the barrier and the locking mechanism still allowing solid organic waste and other solid material to pass in the downstream direction. The barrier with the locking mechanism thereby enable both effective blocking of rats and other vermin, and enabling a reduction of risk of blocking of the barrier.

A 'barrier' may be understood as is common in the art and described in, e.g., <CIT> and/or <CIT>. The barrier may be installed as described in, e.g., <CIT> which is hereby incorporated in their entirety.

By 'suitable for installation at least partly in a sewage pipe' may be understood that the barrier may be positioned at least partially within a sewage pipe, such as partially within a sewage pipe and partially outside of a sewage pipe, such as partially in a well adjacent the sewage pipe, such as a completely inside a sewage pipe. The barrier may be located in a downstream sewage pipe to let rodents escape from a well and further away from housings. However, the barrier may also be used in an upstream sewage pipe so as to allow rats or other rodents to escape into a well and away from the upstream sewage pipe leading to, e.g. a housing.

The term 'vermin' may be understood as any animal similar sized with a rat and that lives or moves within sewage pipes systems. This may e.g. being any rodent or a like.

A 'pipe' may in general be understood to be any pipe, and in particular a sewage pipe, such as pipes for leading a sewage flow, such as any one of domestic sanitary, commercial, industrial, agricultural sewage flow and surface runoff. The pipes usually have a circular cross-sectional profile, but other profiles, e.g. elliptic cross-sectional profile, or with vertical sides and rounded bottom, are possible within the context of the present invention as the skilled person will understand. By 'allowing a sewage flow within the sewage pipe to pass the barrier in a first direction of the sewage pipe' may be understood, that a sewage flow may pass the barrier, such as the barrier being arranged so that the flow resistance of the barrier in the first direction is small enough so as to allow a sewage flow to pass. It may be understood that in an embodiment, a flow resistance of the barrier in the first direction is smaller than a flow resistance in the second direction.

By 'preventing rats or other vermin from passing the barrier in a second direction' may be understood that the barrier may prevent vermin from passing the barrier in at least one direction, such as the second direction, such as an upstream direction. It may further be understood, that the barrier may not block rats or vermin from passing the barrier in the opposite direction, such as in the first direction, such as a downstream direction.

It may be understood, that the barrier may be installed in a pipe so as to allow a flow of liquid in a first direction, such as a downstream direction, and so as to block rats or other vermin from passing the barrier in a second direction, such as an upstream direction. It may be understood, that the barrier may not necessarily block passage of rats or other vermin in a downstream direction.

By 'first direction' is understood a direction of flow of sewage in the sewage pipe, such as a downstream direction. While a pipe in itself may be symmetrical and as such not have any specific flow direction, it is in general understood, that a pipe, such as a sewage pipe, has a primary direction of flow, such as a direction of flow. The direction of flow is the direction in which liquid typically flow through the pipe, such as due to gravity and/or pressure differences. By 'first direction' is understood at direction being parallel with a longitudinal direction of the sewage pipe in a direction being similar to a direction in which flow of sewage is allowed by the barrier, such as a downstream direction.

By 'second direction' is understood a direction in which rats or vermin are blocked. The second direction may be the upstream direction. By 'second direction' is understood a direction being parallel with a longitudinal direction of the sewage pipe in a direction being similar to a direction in which rats or other vermin are being prevented from passing the barrier, where the second direction is opposite to the first direction, such as the second direction being an upstream direction.

By 'upstream direction' of a pipe is understood a direction opposite the flow direction in the pipe.

By 'downstream direction' of a pipe is understood a direction of flow of liquid in the pipe.

By 'a support structure' is understood a structural part of the barrier in from which the shutters may be pivotally suspended.

It may be understood that the support structure may be structurally fixed to the sewage pipe, such as fixed via other structural elements in the barrier, such as fixed in an upper portion of the sewage pipe (with respect to gravity).

A 'shutter' may be understood as is common in the art, such as described in, e.g., <CIT> and/or <CIT>. In general, a shutter may thus denote a structural element, such as a plate or a net or a set of bars, which may be pivotally suspended so as to facilitate barring an aperture in a first angular position and not barring the aperture in a second angular position.

By 'first shutter' and 'second shutter' may be understood shutters which are placed relative to each other, so that in case the barrier is installed in a pipe so as to allow a flow of liquid in a first direction, such as a downstream direction, and so as to block rats or other vermin from passing the barrier in a second direction, such as an upstream direction, the first shutter is placed upstream relative to the second shutter. In other words, the first shutter is the first shutter, which the water passes when flowing through the pipe, pass the barrier in a downstream direction, and a rat or other vermin trying to pass the barrier in an upstream direction will first face the second shutter.

The first shutter and the second shutter are arranged pivotably around each of their axes of rotation, e.g. at a first and a second hinge, respectively. They may be arranged so as to enable each of them to pivot independently from each other, although they may touch each other for certain combinations of angular values.

By being 'pivotably mounted on the support structure' it is understood that each shutter is, directly or indirectly, linked to the support structure, and each pivot around an axis of the hinge in, or on, the support structure. It is noted that the axis of rotation of the first shutter and/or the first locking mechanism may or may not be identical to an axis of rotation of the second shutter and/or the second locking mechanism.

By 'spaced apart along the first direction' it is understood that the first shutter and the second shutter are at different positions, and that these positions spaced apart along the first direction, such as along a direction parallel with the flow, the first shutter is placed at a first position with respect to the first direction, and the second shutter is placed at another position with respect to the first direction. An advantage of having the shutters spaced apart may be, that a rat or vermin trying to open the second shutter (where the second shutter may be the shutter the rat or vermin is facing when trying to pass the barrier in an upstream direction) by rotating it from a first angular position towards another angular position, then the rat or other vermin may have difficulties in handling the partially opened second shutter when it furthermore has to open the first shutter which is placed further upstream. The distance between the first shutter and the second shutter in the flow direction may be a distance arranged so as to be large enough that a rat or vermin cannot reach pass the second shutter and get hold of the first shutter and small enough so that the locking system between the two shutters are able to function, e.g. the distance may be at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, or at least <NUM>. Said distance may be within <NUM>-<NUM>, such as <NUM>-<NUM>, such as <NUM>-<NUM>, such as substantially <NUM>, such as <NUM>.

It is noted that the barrier may be installed in a sewage pipe as described in any one of <CIT> or <CIT>.

It is furthermore noted, that said first shutter, second shutter may be capable of being positioned either in a first orientation in the barrier or in another orientation in the barrier, depending on the possible entering of the vermin, as described in <CIT>.

Particularly, the barrier according to the present invention may have a mounting mechanism comprising two wings, which each have a shape conforming to the sewage pipe interior, preferably the two wings has the shape of a part of the circumference of a circular pipe. The mounting mechanism may be expanded to establish a mounting of the barrier in the sewage pipe. Advantageously, the barrier may accordingly be mounted in standard circular pipes with various diameters because the barrier is insertable, at least partly, in such standard pipes. Additionally, the barrier is easy to replace and/or temporally remove for service and maintenance.

Preferably, the barrier may be installed in a sewage pipe so that the second shutter is pivotal between.

The four angle definitions (v, w, x, z) preferably being defined in relation to each other as follows: <MAT>.

By 'wherein the barrier may be installed in a sewage pipe so that' may be understood that the claimed subject-matter is not confined to a barrier being installed in a sewage.

It may be understood, that the four angular positions defined above (v, w, x and z) is defined for the second shutter. The first shutter and potentially other shutters within a barrier may also have different potential angular position, the angular positions for other shutters within the barrier may not necessarily be identical with the angular positions of the second shutter, but may potentially being relatively similar.

Preferably, the first hinge is arranged with a larger vertical distance to the support structure than the second hinge to provide improved operation of the locking mechanism.

Preferably, the second part of the locking mechanism forms a separate part from the the second shutter.

This embodiment of the invention is particularly, but not exclusively, advantageous in that the parts of the locking mechanism is possible exchangeable so that the locking mechanism potentially mounted in the barrier fit the exact dimension and slope of the sewage pipe system the barrier is installed in.

Preferably, the first part of the locking mechanism being a blocking mechanism, has a form comprising a protrusion, the protrusion being the part of the blocking mechanism, which the corresponding protrusion of the second part of locking mechanism is arranged for engaging.

According to the invention, the first part of the locking mechanism forms a separate part being pivotably mounted on, or near, the first hinge of the first shutter, alternatively being a pre-manufactured part of the first shutter.

According to the invention, the second part of the locking mechanism being formed as a protrusion from the second shutter, said protrusion being an extension of the second shutter so that the second shutter and said protrusion is functioning as one mechanical coherent part, the protrusion preferable being a separate part composed with the second shutter, alternatively being a pre-manufactured part of the second shutter.

Advantageously, the parts of the locking mechanism are possible exchangeable so that the locking mechanism mounted in the barrier fit the exact dimension and slope of the sewage pipe system the barrier is installed in.

Furthermore, this embodiment of the invention is particularly, but not exclusively, advantageous in that the installer and/or user of the barrier may decide themselves, if they want an exchangeable locking system within their barrier or they want a locking system having the two parts being a one- and pre-manufactured part of each associated shutter.

Preferably, the second part of the locking mechanism forms an obstacle for the second shutter to rotate in a direction towards the upstream direction, as the said protrusion is engaging the support structure, the shape and size of the said protrusion thereby defining a first, closed position (v) when the barrier is undisturbed by vermin.

This embodiment of the invention is particularly, but not exclusively, advantageous in that the protrusion of the second shutter potentially can be formed in the exact dimension, so that the angle, defining the first closed (v), is the most optimal angle for stopping vermin opening the shutter and thereby preventing them from passing the barrier.

Preferably, the second part of the locking mechanism comprises a form shaped as a hook.

By 'a hook' may be understood that the protrusion is curved so as it forms a bend.

This embodiment of the invention is particularly, but not exclusively, advantageous in that a protrusion formed as a hook is very optimal for engagement with another component. The said other component being the first part of the locking mechanism.

Furthermore, this embodiment of the invention is particularly, but not exclusively, advantageous in that a protrusion formed as a hook is very easily and relatively inexpensive to manufacture.

Preferably, the first and the second shutters are arranged for preventing vermin from entering the sewage pipe, the first and the second shutters being mounted so that they have a minimum distance between each other so that the vermin cannot grab the first shutter from the upstream direction, such as least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, or at least <NUM>, or the distance being preferably between <NUM> and <NUM>. The said distance being between the lower part of the first and second shutter.

This embodiment of the invention is particularly, but not exclusively, advantageous in that by mounting the two shutters in a distance, so that it is certain, that the vermin cannot grab the first shutter from an upstream direction. Such distance thereby secure, that a vermin cannot unlock the locking mechanism by tipping the first shutter with its forelegs. Many of the already existing vermin barriers on the market having two shutters inside the barrier have positioned the shutters in a distance so the vermin can unlock the locking system it selves, and thereby making the locking system more or less redundant.

Preferably, the first shutter is arranged for acting as an opener of the second shutter, the first shutter rotating towards the downstream direction until engaging with the second shutter, thereby allowing the second shutter to rotate towards the downstream direction from a first, closed position (v) to a third, open position (w), so as to reduce damming of liquid in front of the barrier on the side facing the first shutter by allowing a flow of liquid passing in a downstream direction from the first shutter towards the second shutter.

This embodiment of the invention is particularly, but not exclusively, advantageous in that it enables a flow of liquid to open the barrier itself, so as dispensing with a need for actively opening the barrier for allowing a flow of liquid to pass the barrier.

According to the invention, - when the first shutter is in a closed position - the second part of the locking mechanism is capable of passing the first part of the locking mechanism so that the second shutter is rotatable to a first, closed position (v).

Advantageously, when a flow of liquid has opened the barrier in a downstream direction, the barrier can close it selves into a closed and locked position in a upstream direction, so that no vermin is allowed to pass the barrier.

Preferably, the first shutter has a profile being smoother than a profile of the second shutter, preferably the second shutter has a profile being any one of: a toothed, a serrated, a notched or a pointy profile, and wherein the barrier is arranged to have reversible direction so that the definition of downstream and upstream direction can be reversed using the same barrier.

By 'smoother' may be understood that topographical features on the edge of the first shutter, such as topographical features on the edge as observed from a direction away from the shutter where said direction is orthogonal to a plane of the shutter, may be larger and/or less smoothly than corresponding topographical features on the edge of the second shutter. When referring to degree of smoothness, it may be understood, to be smoothness on a length scale (such as <NUM> or <NUM>), which may be sensed by a rat or other rodent. It may be understood that an edge may be less smooth by comprising pointy features, such as having any one of a saw-toothed profile, a toothed profile, a serrated profile and/or notched profile. It may be understood that qualitatively similar edges, such as two toothed profiles, may differ in smoothness due to differences in quantitative measures, e.g., by differing in any one of amplitude (such as maximum height differences between maximum and minimum points of the profile), frequency and/or phase of teeth. It may be understood, that smoothness is to be understood to refer to a smoothness, which may be sensed by a rat or rodent upon touching said edge.

This embodiment of the invention is particularly, but not exclusively, advantageous in that the barrier can be used in any sewage pipe no matter how there downstream direction and upstream direction is defined, since the barrier is reversible.

Furthermore, this embodiment of the invention is particularly, but not exclusively, advantageous in that the second shutter is less likely to get dirty by contact with the solid matter. In particular, this may be seen as an advantage when at least a part of an edge of the first shutter is smoother than a corresponding part of an edge of the second shutter, since the less smooth edge of the second shutter would then be relatively more likely to attract the solid matter, unless the - relatively smooth - first shutter is arranged for guiding the solid matter around the second shutter.

Furthermore, this embodiment of the invention is particularly, but not exclusively, advantageous in that the second shutter having a toothed or alike profile will intimidate the vermin from trying to squeeze through/under the second shutter.

The invention also relates to a method for preventing vermin from passing through a pipe, such as a sewage pipe, preventing vermin from passing through a pipe in at least one direction in the pipe, at least in an upstream direction, said method comprising installing a barrier according to any of the preceding claims in the pipe.

The invention will hereafter be described in more detail with regard to the accompanying figures. The figures show one way of implementing the present invention and is not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

<FIG> shows a view of a barrier <NUM> suitable for installation at least partly in a sewage pipe and for allowing a sewage flow within the sewage pipe to pass the barrier in a first direction of the sewage pipe, the first direction being a downstream direction <NUM>, and for preventing rats or other vermin (schematically shown above arrow <NUM>) from passing the barrier in a second direction being opposite to the first direction upon installation of the barrier in the sewage pipe, the second direction being an upstream direction <NUM>, said barrier comprising;.

<FIG> furthermore shows that a profile, such as a second profile, of a part of an edge of the second shutter <NUM> is toothed, and that a profile, such as a first profile, of a part of an edge of the first shutter <NUM> is smooth. It may be noted that support structure <NUM> is shown in <FIG> as the plate immediately above the shutters, but it may in general be understood to be at least a portion of the barrier <NUM>, besides the respective shutters <NUM> and <NUM>, on which the shutters are or may be mounted.

<FIG> shows an example of an inner portion <NUM> of a barrier <NUM> with a support element <NUM>, a first hinge <NUM> and a second hinge <NUM>, a first shutter <NUM> and a second shutter <NUM>, and a locking mechanism with a first part <NUM> and a second part <NUM>.

<FIG> furthermore shows an example of an inner portion <NUM> of a barrier <NUM>, wherein the first hinge <NUM> is arranged with a larger vertical distance to the support structure <NUM> than the second hinge <NUM>.

<FIG> furthermore shows an example of an inner portion <NUM> of a barrier <NUM> having a first part of the locking mechanism <NUM> being a blocking mechanism, that has a form comprising a protrusion, the protrusion being the part of the blocking mechanism, which the corresponding protrusion of the second part of locking mechanism <NUM> is arranged for engaging with. <FIG> shows the portion <NUM> of a barrier <NUM> having a first part of the locking mechanism <NUM> that forms a separate part being pivotably mounted on, or near, the first hinge of the first shutter, alternatively being a pre-manufactured part of the first shutter.

<FIG> furthermore shows an inner portion <NUM> of a barrier <NUM>, wherein the second part of the locking mechanism <NUM> are formed as a protrusion from the second shutter <NUM>, said protrusion <NUM> being an extension of the second shutter <NUM> so that the second shutter and said protrusion is functioning as one mechanical coherent part, the protrusion <NUM> preferable being a separate part composed with the second shutter <NUM>, alternatively being a pre-manufactured part of the second shutter. The second part of the locking mechanism <NUM> being a protrusion is in <FIG> shaped as a hook <NUM>.

Moreover, <FIG> shows an inner portion <NUM> of a barrier <NUM>, wherein the first <NUM> and the second <NUM> shutters are arranged for preventing vermin from entering the sewage pipe, the first and the second shutters being mounted so that they have a minimum distance between each other so that the vermin cannot grab the f In an embodiment there is provided a barrier, wherein the first part of the locking mechanism being a blocking mechanism, has a form comprising a protrusion, the protrusion being the part of the blocking mechanism, which the corresponding protrusion of the second part of locking mechanism is arranged for engaging the first shutter from the upstream direction, the distance being preferably between <NUM> and <NUM>.

<FIG> shows a cross-section of an inner portion <NUM> of a barrier <NUM> in a first closed position (v). The position (v) defines the condition of the barrier when it is undisturbed only affected by gravity.

furthermore shows the second part of the locking mechanism <NUM>, being an obstacle for the second shutter <NUM> to pivot in the upstream direction <NUM>, as the protrusion <NUM> encountering the top of the support structure <NUM>, the shape and size of the protrusion <NUM> defining the first closed position (v).

<FIG> shows a cross-section of an inner portion <NUM> of a barrier <NUM> in a configuration where a second shutter <NUM> is locked by a locking mechanism <NUM> and <NUM> being in a second closed position (x). The position (x) defines the condition of the barrier <NUM> when it is disturbed by a vermin (not shown) tampering with the second shutter trying to pass the barrier.

<FIG> furthermore shows a an inner portion <NUM> of barrier <NUM>, wherein a second part of the locking mechanism <NUM>, is intended to engage with a first part of the locking mechanism <NUM>, when the second shutter <NUM> is tampered to be opened by a vermin, when the engagement of the first <NUM> and second part <NUM> of the locking mechanism takes effect, the protrusion <NUM> of the second shutter <NUM> will encounter the blocking mechanism <NUM> on or near the first shutter <NUM> and thereby only make a limited rotation of the second shutter possible, the rotation being limited so that the second shutter <NUM> cannot be opened or passed by a vermin from the upstream direction <NUM>, the locking mechanism thereby ensure the second shutter <NUM> being kept in a closed position, the position being a second, closed position (x).

<FIG> shows a cross-section of an inner portion <NUM> of a barrier <NUM> in a configuration where a first shutter <NUM> allows opening of a second shutter <NUM>. The first shutter <NUM> is arranged for acting as an opener of the second shutter <NUM>, the first shutter rotating towards the downstream <NUM> direction until engaging with the second shutter <NUM>, thereby allowing the second shutter to rotate towards the downstream direction from a first, closed position (v) to a third, open position (w), so as to reduce damming of liquid in front of the barrier on the side facing the first shutter <NUM> by allowing a flow of liquid passing in a downstream direction <NUM> from the first shutter <NUM> towards the second shutter <NUM>.

<FIG> shows a cross-section of an inner portion <NUM> of a barrier <NUM> in a third opened position (w). The position (w) defines the condition of the barrier when a flow of liquid is passing in a downstream direction <NUM>, cf. <FIG>, from the first shutter <NUM> to the second shutter <NUM>.

<FIG> shows a cross-section of an inner portion <NUM> of a barrier <NUM> in a fourth partly opened position (z), wherein - when the first shutter <NUM> is in a closed position - the second part of the locking mechanism <NUM> is capable of passing the first part of the locking mechanism <NUM> so that the second shutter <NUM> is rotatable to a first, closed position (v).

<FIG> shows cross-section of an inner part <NUM> a barrier <NUM> being reversible so that the definition of downstream <NUM> and upstream direction (<NUM>) can be reversed using the same barrier. The barrier <NUM> comprises a support structure <NUM> with a first hinge and a second hinge. Also, a first shutter <NUM> is pivotably mounted on the first hinge, and a second shutter <NUM> is pivotably mounted on the second hinge, and a locking mechanism comprising a first part <NUM> and a second part <NUM>.

<FIG> shows a click-on and a click-off function of the locking mechanism. In the figure, the click-on/off functions are shown for the first locking mechanism for the blocking mechanism <NUM>. The click-on/off functions could as well be applicable for the second locking mechanism <NUM>. It is shown here, that the parts of the locking mechanism <NUM> and <NUM> without tolls, or with simple tools, can easily be attached and removed from the barrier <NUM>, preferably on the site where the barrier is installed.

<FIG> shows two different perspectives of a barrier <NUM> for installation in a sewage pipe.

In short, the invention relates to a barrier <NUM> suitable for installation in a sewage pipe and for preventing vermin from passing the barrier. The barrier comprising a support structure <NUM> with a first hinge <NUM> and a second hinge <NUM>, a first shutter <NUM> pivotably mounted on the first hinge, a second shutter <NUM> pivotably mounted on the second hinge, and a locking mechanism comprising a first part <NUM> being a blocking mechanism, a second part <NUM> being formed as a protrusion. The locking mechanism is provided for keeping the second shutter <NUM> in a closed position, when the second shutter is tampered with by a vermin, e.g. a rat, trying to pass the barrier. This vermin barrier has the advantage of being reliable for preventing any vermin to pass the barrier, as the locking system within the barrier has a very optimal locking effect.

Claim 1:
A barrier (<NUM>) suitable for installation at least partly in a sewage pipe and for allowing a sewage flow within the sewage pipe to pass the barrier in a first direction of the sewage pipe, the first direction being a downstream direction (<NUM>), and for preventing rats or other vermin from passing the barrier in a second direction being opposite to the first direction upon installation of the barrier in the sewage pipe, the second direction being an upstream direction (<NUM>), said barrier comprising;
- a support structure (<NUM>) with a first hinge (<NUM>) and a second hinge (<NUM>),
- a first shutter (<NUM>) pivotably mounted on the first hinge,
- a second shutter (<NUM>) pivotably mounted on the second hinge, and
- a locking mechanism comprising
- a first part (<NUM>) of the locking mechanism formed as a separate part, the first part being a blocking mechanism pivotably mounted on, or near, the first hinge of the first shutter, the blocking mechanism being positioned between, or partly between, the first (<NUM>) and the second (<NUM>) shutter, and
- a second part (<NUM>) of the locking mechanism, the second part being formed as a protrusion from, or near, the top of the second shutter,
wherein the barrier is arranged for being installed in the sewage pipe so that the first shutter and the second shutter are spaced apart along the first, downstream direction (<NUM>) so that the first shutter is placed before the second shutter on an axis parallel with the first, downstream direction, and
wherein the locking mechanism is provided for keeping the second shutter (<NUM>) between a first, closed position (v) and a second, closed position (x) when the second shutter is tampered with by a vermin trying to pass the barrier from the second, upstream direction (<NUM>), the second shutter being allowed to have a limited rotation defined by engagement of said first part (<NUM>) and said second part (<NUM>) of the locking mechanism, said first part and said second part being arranged for engagement between, or above, the first and the second shutter, said rotation thereby being limited by the locking mechanism so that the second shutter cannot rotate to a third, open position (w),
wherein, when the first shutter is in a closed position - the second part of the locking mechanism is capable of passing the first part of the locking mechanism so that the second shutter is rotatable from the third, open position (w) to the first, closed position (v).