Field of the invention

The invention relates to a bridge barrier for the protection of a rear area against a rising water level from a front area, wherein the bridge barrier acts between a bottom and a water surface, wherein the bridge barrier comprises at least one blocking element with a longitudinal direction and a height direction, wherein the longitudinal direction, in an operating situation, extends essentially across an area, for example a stream, a fjord, a river or a river delta, wherein the height direction, in an operating situation of protection, extends from the bottom of an area, for example a stream, a f ord, a river or a river delta, and up, wherein the at least one blocking element, during operation, cooperates with a bottom rail system arranged at the bottom of the area in question.

The invention further comprises a method for establishing such a bridge barrier for the protection of a rear area against a rising water level from a front area.

Background of the invention

It is generally known to use different protection systems to stem rising water table levels, whether due to tides, wind, rain or a storm surge. Hereinafter, these systems are collectively called a bridge barrier.

For example, a number of different locks are known, including at the mouths of several Danish rivers into the North Sea. These locks work with side-hung gates or with lifting gates, wherein the gates can be opened and closed as needed, thus protecting low-lying areas further inland against flooding with seawater during heavy winds from the west. Undersluices or chamber locks are typically used for such tasks. Lock systems work well and efficiently in sealing off relatively narrow passages, but at the same time require a significant construction structure. For wider passages, such as the mouth of a f ord or off a bay, the known gate solutions are not suitable. Partly because of the extension to be stemmed, but also because of both the construction costs and an often unattractive architectural impact on the area.

Furthermore, flap gates are also known, arranged on the seabed from where they can be tilted upwards about a horizontal axis by the seabed when there is a stemming need. As mentioned, this entire structure is arranged on the seabed, which of course also requires extensive construction and foundation work. In addition, there are a number of challenges in maintaining the structure, as sanding up and sediment deposition will typically occur over time, to which should of course be added the common challenge of supervision and maintenance of a structure mounted underwater. At the same time, the structure is complicated and very costly to establish at the bottom of a fjord or similar.

Another variant of a gate system are the so-called Moses gates, which are known from Venice. These gates are also arranged on the seabed in a foundation, but are raised simply by allowing compressed air to displace water from the interior of the gate elements. This increases the buoyancy of said gate elements which therefore rise from the seabed and act as a high water protection. This solution avoids complex and vulnerable chain drives or other hoisting facilities to raise the gate elements from the seabed. Maintenance-wise and inspection-wise, there is no immediate difference between Moses gates and the flap gates mentioned above.

The disadvantage of the types of bridge barriers mentioned is that they require considerable foundations and/or structures, which are typically large and unsightly and, not least, costly to establish and to replace when needed. The reason for the size of the foundations/structures is that they must be able to withstand the horizontal forces that arise when water has to be withheld from entering a given area. The forces on the two respective sides of a bridge barrier naturally remain in balance as long as the water level is the same on both sides, but when the water level rises on the one side, horizontal forces arise, which must be absorbed into the foundation of the structure in question.

A further disadvantage of the known bridge barriers is that they do not allow pedestrian or vehicular passage across the water surface of the area.

However, from US 2017/0175352 Al, a method is known in which a bridge barrier is established, wherein a blocking element has a first position in which it may be used as a bridge, and a second position in which the blocking element may establish protection against a rising water level. However, it is not shown therein that a support face has been provided for the blocking element when this is in its operating situation. This is a disadvantage, as great forces may act on the blocking element. Object of the invention

The object of the present invention is to provide a solution for a bridge barrier in which a good, efficient and simple solution is achieved, whereby a rising water level can be retained on an outer side of a bridge barrier, thereby avoiding or at least minimising any flooding of a low-lying area on the rear side of said bridge barrier.

The object is also to provide a bridge barrier, wherein the at least one blocking element, when it is not in operation for establishing protection, may be used as a bridge for pedestrian or vehicular passage across the water surface of the area.

It is a further object of the invention to provide a method for establishing such a bridge barrier.

Description of the invention

The invention relates to the bridge barrier referred to above and in the preamble of claim 1, which is novel in that the bridge barrier comprises:

- a contact face on a bottom rail system, adapted for contact with a cooperating contact face on the at least one blocking element; and

- a support for the blocking element arranged along the bottom rail system, located in the direction of the rear area;

- that the blocking element has a first position and a second position in relation to the support, wherein the second position is established in an operating situation for protection;

- that the blocking element is supported in the first position on a first support face of the support, and wherein a surface of the blocking element is horizontal and may be used as a bridge for pedestrian or vehicular passage across the water surface of the area;

- that the blocking element is supported in the second position on a second support face of the support and is located with the contact face in the form of a first side edge on the surface of the blocking element in contact with the contact face of the bottom rail system;

- that the opposite second side face of the surface in the second position of the blocking element is vertically higher than the first support face of the support; and

- that the second support face is closer to the foundation than the first support face. The method of the invention is distinctive in that the establishment of said bridge barrier comprises at least the following method steps:

- placing a bottom rail system with a contact face adapted for contact with a cooperating contact face on the at least one blocking element; and

- placing a support for the blocking element arranged along the bottom rail system, located in the direction of the rear area, said support having a first support face and a second support face for the blocking element;

- placing the blocking element, so that it has a first position and a second position in relation to the support, wherein the blocking element is supported in the first position on the first support face of the support, and wherein a surface of the blocking element is horizontal and may be used as a bridge for pedestrian or vehicular passage across the water surface of the area, and wherein the blocking element is supported in the second position on the second support face of the support and is located with the contact face in the form of a first side edge on the surface of the blocking element in contact with the contact face of the bottom rail system, so as to establish an operating situation for protection against a rising water level in the front area from entering into the rear area, the opposite second side face of the surface in the second position of the blocking element being vertically higher than the first support face of the support, and the second support face being closer to the foundation than the first support face.

This achieves a solution wherein the respective blocking elements are displaced from their first horizontal position to their operating position, wherein they are largely vertical with an upper edge, which will be in a position above the expected water level of the high tide. This may happen when a need therefor is foreseen. Typically, a storm surge or other situation that causes an increased water level will be foreseeable with up to two days’ notice. There is subsequently ample time to bring the necessary blocking elements in place in the bottom rail system and against the support to withstand pressure from the increased water level.

In the bridge barrier, actuators are provided between the blocking element and the support for establishing the movement between the first and second positions of the blocking element.

In the bridge barrier, the connection between a blocking element and the support is established, for example, by hinges and rails with sliding guideways for their mutual rotation and displacement. Rotation then occurs around a axis of rotation defined by the hinge, and displacement occurs along a sliding rail or similar sliding face on the support.

For example, the bottom rail system may be U- or I-shaped and cooperate with a matching shape on the respective blocking elements. In a preferred variant of a bottom rail system, this may advantageously be fixed with driven piles, a sheet wall, or the bottom rail system may be fixed with the known "suction bucket" principle. Thus, there is no significant impact on the bottom, as neither large excavations nor extensive construction work is required. The bottom rail system can be laid out in sections that are placed and anchored using suitable processes on the bottom. Subsequently, or concurrently with or before, the support is placed by driving piles into the bottom which extend to a position above normal daily water level. At the upper end of the piles, the beam structure is mounted, which provides the first and second support faces for the blocking element. The blocking elements are then placed on the beam structure. The piles allow water to pass freely under the blocking element when it is not in operation for the protection of the rear area. In this situation, the blocking elements will be located on the first support face and can be said to constitute bridge elements that allow pedestrian or vehicular passage across the area on the horizontal surface of the blocking elements.

Construction costs are relatively low due to the simple principle of construction.

During normal use, the bridge barrier will typically be established to protect, for example, a port or residential area against flooding in connection with a storm surge or another situation that may result in an unwanted water level increase. It will therefore typically be seawater that is blocked, which is why the blocking elements are typically designed to rotate to one side of the support, namely away from land, so that the water pushes from the outer side. This pushes the blocking elements into contact against the contact face of the bottom rail. However, the design can also withstand a water pressure from the land side if actuators are used to retain the structure.

Alternatively, the bridge barrier may be arranged with a bottom rail system on either side of the support, and the support may be arranged with a second support face on either side of the first support face. Thus, the blocking elements can be rotated both ways in relation to the support.

In an embodiment, the bridge barrier of the invention may be distinctive in that the blocking element is adapted for rotation between the first position and the second position.

By rotating the blocking element in relation to the support, the blocking element can be changed between the first position with the horizontal face acting as a bridge, to a second position in which the blocking element is in operation to protect the rear area in the event of high tide, a storm surge or similar in a front area of the bridge barrier.

The rotation may be carried out in a simple manner by the blocking element being attached to the support via hinge connections. If the blocking element has a width and the hinge is placed in an appropriate position on the support, the rotation may be carried out so that the first side edge of the blocking element is placed in contact with the contact face of the bottom rail system, while the blocking element rests on the second support face of the support. This may be done in a simple manner by appropriate sizing of the elements forming part of the bridge barrier.

There may also be situations in which the height of the support is such that the rotation cannot ensure that the first side edge of the blocking element is brought into abutment with the bottom rail system.

In an embodiment, the bridge barrier of the invention may therefore be distinctive in that the blocking element is also adapted for a translational displacement in relation to the support.

By combining the rotation with a translational displacement, the blocking element may be displaced translationally after rotation to bring the first side edge into contact with the bottom rail system. The translational displacement may be carried out by a rail system being provided at the underside of the blocking element, which is in abutment with the support. This allows sliding guideways or sliding rails located on the second support face of the support and the underside of the blocking elements to allow for the mutual displacement. In an embodiment, the bridge barrier of the invention may be distinctive in that the angle between the surface in the first and second positions is between 45° and 90°, preferably between 60° and 90°, and more preferably between 70° and 80°.

By rotating the blocking element to the second position, in which it is in operation, it is desirable that the angle is as large as possible so that the blocking element may be provided with an approximately vertical orientation with its first side edge resting on the bottom rail system. This achieves the highest height of the bridge barrier. Similarly, an approximately vertical orientation will also ensure that rising water from a front area cannot be pushed over the blocking element in the event of waves.

In a particular embodiment, the blocking element may, at the opposite second side that is swung upwards, be provided with a wall perpendicular to the surface of the blocking element. This perpendicular wall may serve as a handrail when the blocking element is in its first position and may serve to prevent the risk of waves crashing over the second edge of the blocking element in an operating situation.

In an embodiment, the bridge barrier of the invention may be distinctive in that the bottom rail system comprises a sheet wall or a series of juxtaposed piles driven into the bottom and a rail mounted thereon, which comprises the contact face of the rail system.

This ensures inexpensive anchoring of the bottom rail system on the bottom. Especially when establishing a bridge barrier with a considerable extension in the longitudinal direction, this embodiment is advantageous, since the establishment of conventional foundations is often too expensive.

In an embodiment, the bridge barrier of the invention may be distinctive in that the support is formed by a series of juxtaposed piles driven into the bottom and beam structures mounted thereon, which form the first and second support faces.

Since the support for the blocking element is formed by juxtaposed piles, free water passage between the piles is possible when the blocking element is in its first position and acts as a bridge. In this situation, the piles and the beam structure will extend not only above the seabed, but also to a position above the water surface at normal water level.

The beam structure may have the first support face located at a distance of 1 to 10 metres above the water surface at normal water level.

The bridge barrier of the invention will typically be used in situations with a water level difference of up to about 3 metres. Thus, the height of the first support face above the water surface at normal water level will typically be 1-2 metres.

Alternatively, the bridge barrier may be located in a land area adjacent to the front water area and thus be located in a land area where the rear land area must be protected against a rising water level in the front water area. Such a land area will typically be a wetland where passage along the water area is difficult and where a bridge barrier with the blocking element in the first position may advantageously be used for pedestrian or vehicular passage in the same way as is known from path and road systems on top of dykes used along the water area to protect the rear land area. In this case, by using a bridge barrier according to the invention, the height of the dyke may be reduced or a dyke may be completely replaced by a bridge barrier.

In this case, at normal low water level, the land surface can be said to be a ‘bottom’, since the land surface will form a bottom at high water levels that flood the adjacent land area. In this situation, the bottom rail system may be in contact with the first side edge of the blocking element, so that rotation of the blocking element takes place around the contact face between the first side edge and the contact face of the bottom rail system.

The bottom rail system may then have its contact face located approximately at the level of the land surface. Preferably, the support for the blocking element will be formed by two parallel walls, wherein the blocking element in its first position rests against contact faces on top of the two walls, which are piled into the land area, so that their upper side is approximately level with the ground surface. The two walls may be interconnected by a bottom wall or by beams located between the two walls. The bottom wall or the beams may serve to support actuators to provide the rotation of the blocking element. The abutment of the actuators with the underside of the blocking elements can be said to constitute the second support face for the blocking elements in the second position.

The height of the first support face of the beam structure above the seabed and above the surface of normal water level will depend on the risk of high water level in the front area in the event of a storm surge, tide or high tide.

In an embodiment, the bridge barrier of the invention may be distinctive in that the first support face is horizontal and is formed by the upper side of a series of juxtaposed beam structures.

The first support face does not have to be a contiguous face. It may advantageously be formed by a series of juxtaposed beam structures, wherein the upper side of an upper beam is preferably horizontal. This achieves a secure support for the blocking element when it is located with the surface horizontally and acts as a bridge for walking and vehicular traffic. When the first support face is horizontal, a simple construction is achieved in relation to a support face, which will be angled in relation to a horizontal orientation. In the horizontal orientation of the first support face, the blocking element may be constructed with a back side parallel to the surface.

The second support face may also be advantageously formed by a series of juxtaposed beam structures, wherein the upper side of a series of juxtaposed beams has an oblique orientation in relation to the horizontal.

In an embodiment, the bridge barrier of the invention may be distinctive in that the bridge barrier comprises at least two or more blocking elements, wherein at least the one end face of a blocking element comprises sealing means for abutment with an end face of an adjacent blocking element.

Said variant of a bridge barrier may, for example, be provided with sealing means in the form of a kind of fender (an elastic plastic or rubber element) arranged on the end of the blocking elements. In an embodiment, the respective ends of two adjacent blocking elements may both be equipped with sealing means that are either in abutment with each other or complement each other, for example by being arranged in a mirrored relationship to each other. By having sealing means on the ends of the blocking elements, the advantage is achieved that they can be moved in relation to each other and, of course, also that no more water than absolutely necessary penetrates the bridge barrier. Depending on the use, a more or less tight assembly may be sought.

If the bridge barrier protects a large basin, such as a f ord, it is clear that it is not a goal as such to create a very tight joint between two adjacent ends, but that the joint should also not allow any significant flow.

If the bridge barrier protects a small basin, such as a port and/or great values, such as a transformer station, a joint that is as tight as possible will be sought.

In an embodiment, the bridge barrier of the invention may be distinctive in that the at least one blocking element in a series of several blocking elements is arranged rotatably around an essentially vertical axis or an essentially horizontal axis to a position, so that a disconnection has been formed to allow sailing passage across the bridge barrier between the front area and the rear area.

In the bottom rail system there is a contact face which - when the blocking element is in a non-active position - forms the abutment for the contact means of the blocking element. On one or both of these, packings may be arranged which, when in contact between blocking element and bottom rail, prevent water from flowing freely from one side of the bridge barrier to the other side. In a simple embodiment, this may be an elastic coating or lip on the contact means of the blocking element, such as a rubber seal.

In situations where a very tight closure of the bridge barrier is advantageous, such as port entrances, the packings may be inflatable. This applies to both the packings between blocking element and bottom rail and packings between blocking element and side piece. The packings can also act as shock absorbers when displacing the blocking element for contact with the bottom rail. Furthermore, the packings maintain a possible close seal if, over time, the bottom structure should change due to, for example, soft bottom conditions or the like. Furthermore, it should be mentioned that the bottom does not necessarily have to be horizontal. Thus, the foundation can follow the profile of the bottom course and the blocking elements can be adapted thereto.

According to according to a further embodiment, the bridge barrier of the invention is distinctive in that the bottom rail system is formed by a single rail, wherein the blocking element is only in abutment with one side of the bottom rail system.

The blocking element may be in abutment with the bottom rail system in different ways. As an alternative to being in abutment with one side of a rail, the blocking element may also, via a translational displacement, be located between two sides of a U-shaped top side of a rail in the bottom rail system. However, an abutment with one side of a single rail in the bottom rail system will be possible and may provide sufficient sealing. The side edge and the bottom rail system may be provided with sealing elements which provide a safe seal between the two elements in the operating situation for the blocking element.

The side of the bottom rail system with which the blocking element is in abutment, preferably faces the front area.

According to a further embodiment, the bridge barrier of the invention is distinctive in that the rail system essentially follows the bottom course in the longitudinal direction and in that the at least one blocking element is adapted so that in an operating situation, it follows the rail system in the longitudinal direction.

This achieves inexpensive construction compared to bridge barriers that require a horizontal rail system, as costly work at the bottom of the area may be reduced or avoided altogether.

Regardless whether blocking takes place using one type or another of blocking elements, there will typically be a water increase on both the outer side - i.e. in front of the blocking elements, as well as on the inner side - i.e. behind the blocking elements. This is because there will constantly - typically - be a supply of water from the hinterland, regardless of whether a storm surge is pushing water from the outside and into, for example, a fjord or stream.

Prior to placing the necessary blocking elements, the bottom rail system may advantageously be cleaned with a cleaning tool which is pulled through the bottom rail, thereby removing sand and other sediments, thus ensuring that a desired tightness can be achieved between the respective blocking elements and the bottom rail system. Such a cleaning tool may in principle be constituted by ‘V-blade’, which lifts the unwanted sand and sediment up and out of the bottom rail system. It could also be imagined that the cleaning take place with a tool, wherein water is flushed down into the bottom rail, thus removing sand and sediment. This cleaning may be carried out in many conceivable ways, and it is clear that the methods mentioned are but two of many possible ones to a person skilled in the art.

When the bridge barrier is not in use to protect against a rising water level, it may advantageously be used as a bridge. The blocking elements may therefore be provided with appropriate railings or have a shape which ensures pedestrian and/or vehicular passage.

Drawing

In the following, the invention will be explained in detail with reference to the appended schematic drawing, in which:

Fig. 1 shows a partial schematic view of an area with bottom and daily water level; Fig. 2 shows a schematic view of a bottom with a sheet wall and a top rail;

Fig. 3 shows the sheet wall of Fig. 2 and a support for a blocking element in the form of piles as well as a beam structure, however for illustrative reasons without illustration of the bottom;

Fig. 4 shows a schematic view, which for illustrative reasons is partially transparent, of the bridge barrier with a blocking element located in a first position on the support and at daily water level;

Fig. 5 shows a view corresponding to Fig. 4, but with the blocking element in its second position in an operating situation at high tide in a front area;

Fig. 6 shows a schematic view of a bridge barrier made from a number of juxtaposed sections, as illustrated in Fig. 4, and in a situation at daily water level;

Fig. 7 shows a schematic view similar to Fig. 6, but illustrating a situation at high tide with the blocking elements in their second position in an operating situation;

Fig. 8 shows a principle sketch of a bridge barrier with a bottom rail system that follows the bottom course - seen perpendicular to the longitudinal direction;

Fig. 9 shows a principle sketch of a bridge barrier located in a land area adjacent to a front water area and with a blocking element in a first position on the support and at daily water level; and

Fig. 10 shows a view corresponding to Fig. 9, but with the blocking element in its second position in an operating situation at high tide in the front area.

Detailed description

Fig. 1 shows a partial principle sketch of an area 1 in a situation before a bridge barrier was located in the area and with normal water level. 2 indicates the bottom itself. 3 indicates the surface of the bottom. 4 indicates the surface of the water 4' at normal water level.

Fig. 2 corresponds to Fig. 1, but here the water 4' is omitted. In Fig. 2, a sheet wall 5 is provided in the bottom, and on top of the sheet wall, a bottom rail system 6 is provided.

The bottom rail system comprises a rail 7 and a sealing 8 mounted thereon. The bottom rail system will lie approximately level with the surface 3 of the bottom 2.

Fig. 3 corresponds to the drawing shown in Fig. 2, but here an additional support 9 is shown.

On top of the sheet wall, a U-shaped rail 7 is mounted. The rail 7 has a bottom face 10 on top of the sheet wall and branches 11, located on either side of the sheet wall 5.

The support 9 consists of a pile structure with vertical piles 12 driven into the seabed (not shown in Fig. 3), so that part of the piles and a beam structure 13 located thereon are located above the seabed. The support 9 is located with an extent parallel to the bottom rail system 6. This means that a blocking element 14, illustrated in Fig. 4, has a longitudinal direction 15 parallel to the rail system when the blocking element is located on the support 9. The longitudinal direction 15 also indicates the longitudinal direction of the bridge barrier formed. In the situation shown in Fig. 4, a height direction 16 for the blocking element will run approximately parallel to the water surface 4, as the blocking element 14 is in the first position. In this first position, a surface 17 may serve as a bridge for pedestrian or vehicular passage across the water surface 4 of the area.

Fig. 3 shows that the beam structure 13 of the support provides a first support face 18 for the blocking element 14 when this is in the first position shown in Fig. 4.

The beam structure 13 provides a second support face 19, where the blocking element 14 is in abutment when it is in a second position, as illustrated in Fig. 5.

Fig. 5 illustrates a situation in which there is a high water level with a high water surface 20 in a front area 21 compared to the normal water surface 4 in a rear area 22.

In its second position, the blocking element will have a first side face 23 of the surface 17 in contact with the bottom rail system 6. The side face 23 and the rail 7 of the bottom rail system thus provide contact faces between the two elements. Sealing elements may be provided at the contact faces.

The opposite second side face 24 of the blocking element is in a position vertically higher than the first support face 18 of the support on the support 9. Thus, the height direction of the blocking element will now be provided as indicated by the arrow 16. The height direction thus extends upwards in the operating situation shown in Fig. 5, wherein the blocking element protects the rear area 22 against the higher water level in the front area 21.

Fig. 5 shows actuators 25 located between the support 9 and the blocking element 14. The actuators 25 may be double-acting cylinders providing a rotation of the blocking element around an axis of rotation 26 (se Fig. 3), defined by a comer between beam 27 of the beam structure, which defines the first support face 18 and beam 28 of the beam structure, which defines the second support face 19. A sliding face is simultaneously provided on the beam 28 so that the blocking element 14 can make a translational movement along the beam 28 to secure the abutment between the first side face 23 and the rail 7. The beam 28 and/or the blocking element may be provided with guide rails or guideways to ensure the correct guide of the blocking element between the first and second positions.

Above, a bridge barrier is explained with reference to the illustration of a single section.

In Figs. 6 and 7, a bridge barrier is shown with a structure of several sections, each consisting of a bridge barrier as explained above.

Fig. 6 illustrates the blocking elements 14 in the position, wherein they have a horizontal surface forming a coherent surface that may be used as a bridge for pedestrian or vehicular passage across the water surface in a wide area, where it is not appropriate to use only a single section for a bridge barrier.

Fig. 7 illustrates the blocking elements located in their second position for operation as a blocking element to protect the rear area 22 against a rising water level in the front area 21.

Fig. 8 shows a principle sketch of the bridge barrier, wherein the bottom rail system 6 essentially follows the bottom course 29 in the longitudinal direction 15. The blocking elements 14 are adapted so that, in an operating situation, they follow the bottom rail system 6 in the longitudinal direction 15. This structure achieves a more inexpensive design compared to solutions wherein the foundation must be horizontal, because costly work on the bottom for the establishment of horizontal foundation is avoided. Height differences in the bottom course can be compensated by varying the width of the blocking element.

Figs. 9 and 10 show an alternative bridge barrier 1 located in a land area 30 adjacent to a front water area 31 and thus located in the land area 30, wherein the rear land area 32 must be protected against a rising water level in the front water area 31. Such a land area 30, 32 will typically be a wetland, where passage along the water area 31 is difficult. A bridge barrier with the blocking element 14 in the first position as shown in Fig. 9 may be used for pedestrian and vehicular passage in the same way as is known from path and road systems on the top of dykes. In this case, at normal low water level 4, as seen in Fig. 9, the land surface 33 can be said to be a ‘bottom’, since the land surface 33 will form a bottom at high water levels that flood the adjacent land area 30. In this situation, the bottom rail system 6 may be in contact with the first side edge 23 of the blocking element, so that rotation of the blocking element takes place around an axis of rotation 26 defined by the contact face between the first side edge and the contact face of the bottom rail system.

The bottom rail system may then have its contact face located approximately at the level of the land surface 33. Preferably, the support 9 for the blocking element 14 is formed by two parallel walls 34, wherein the blocking element in its first position rests against contact faces on top of the two walls 34, which are piled into the land area 30, so that their upper side is approximately level with the ground surface 33. The two walls are interconnected by a bottom wall 35, which is located between the two walls 34. The bottom wall 35 serves to support actuators 25 to provide the rotation of the blocking element 14. The abutment face of the actuators against the underside of the blocking elements 14 can be said to constitute the second support face for the blocking elements 14 in the second position.