Drift Shield
The present invention relates to a drift shield which is adapted to be fastened to essentially vertical posts (6) arranged in the ground. The wind shield comprises a plastic sheeting (2) and at least two longitudinal stiffening strips (4) which are essentially parallel in relation to the ground and which are joined to the plastic sheeting (2) along the whole length of the plastic sheeting (2). Several dynamic wind dampers (12) in the form of V-shaped cuts are arranged in the plastic sheeting (2) in such a manner that they allow wind to pass through. The V-shaped cuts of the dynamic wind dampers (12) are arranged in columns, the dynamic wind dampers in the same column being located vertically straight under each other and the dynamic wind dampers in two adjacent columns being vertically offset in relation to each other.
The present invention relates to a drift shield for protecting road sections or other objects against drifting snow, sand or other airborne material.
PRIOR ARTMany different types of drift shields are described in the patent literature. A drift shield of classic type is disclosed in the American patent U.S. Pat. No. 3,966,172, which describes a fence with sections consisting of transverse ribs or posts which can be fastened to each other and leaned against each other so that the fence will get a triangular shape when seen from the side. The main purpose of this fence is to create a portable fence which can be erected and demounted in a simple manner.
U.S. Pat. No. 4,932,634 discloses a snow fence of classic type with broad and horizontally extending plastic elements which are fastened to vertical and uniformly spaced fence posts.
A fence for protection against wind and snow consisting of a canvas provided with vent holes is described in the Japanese patent document JP 2010-216095. Each vent hole is quadratic and is at most 144 mm2. The vent holes constitute at least 40% of the area of the canvas in order to prevent a turbulent flow on the side of the canvas facing away from the wind.
Snow fences consisting of metal plates mounted between fence posts are described in the Japanese patent documents JP 2007-315135 and JP 2006-169770. The metal plates are provided with holes which are uniformly distributed over the surface and which constitute 40-60% of the total area. A disadvantage with this solution is that the plates are heavy and opaque.
A snow fence consisting of transparent plastic elements is described in the Japanese patent document JP 7-259020, each plastic element being fastened between two fence posts. Each plastic element is provided with a number of holes which allow wind to pass through.
The drift shields described above are all based on solutions which have fixed slits, i.e. a construction with fixed and given openings through which the wind is allowed to pass. When it comes to fixed slits, it is possible to use Huygens' Principle, which describes how a wave motion arises and propagates. According to Huygens' Principle, two types of nodes are obtained, one node where the waves cancel each other out and another node where the waves instead amplify each other. This implies that areas with a wind that is stronger than the wind on the windward side may ensue on the leeward side of a fence or snow shield with fixed slits. In total, there will however be less wind on the leeward side owing to the fact that half of the wind that is allowed to pass through will dies out. In addition, the fixed material around the fixed slits will also remove a lot of wind. It is however a problem that areas with very strong wind may ensue on the leeward side.
A fence having a grid consisting of fence posts and transverse bars is described in the Japanese patent document JP 2000-257025. A flexible sheet is fastened to each square in three of the four sides of the square. In this manner, an opening is formed at the side of the square where the flexible sheet is not fastened. This solution will not give fixed slits, since the material is flexible. However, it takes a lot of time to mount the fence, since each square in the grid has to be mounted individually.
In view of what has been described above, there is a need for a drift shield which in a better manner avoids the formation of wave motions that amplify each other on the leeward side of the drift shield and thereby causes problem areas with occasionally very hard wind. There is also a need for a drift shield which can be mounted in a simple manner and which can be used on a large scale, for instance along long stretches of roads or the similar and not only for private use around houses or the similar.
SUMMARY OF THE INVENTIONThe object of the present invention is to achieve an efficient drift shield for airborne material which can be produced, mounted and transported in a simple manner.
According to the invention, this object is achieved by means of a drift shield having the features defined in claim 1.
The drift shield according to the invention is adapted to be fastened to essentially vertical posts arranged in the ground. The drift shield comprises a plastic sheeting and at least two longitudinal stiffening strips which are essentially parallel in relation to the ground and which are joined to the plastic sheeting along the whole length of the plastic sheeting. Furthermore, dynamic wind dampers in the form of several V-shaped cuts are arranged in the plastic sheeting in such a manner that they allow air (wind) to pass through. The V-shaped cuts of the dynamic wind dampers are arranged in columns, the dynamic wind dampers in the same column being located vertically straight under each other and the dynamic wind dampers in two adjacent columns being vertically offset in relation to each other. It has appeared that such an arrangement of the dynamic wind dampers entails that the effect with amplifying wave motions according to Huygens' Principle on the leeward side of the drift shield is eliminated to a large extent. Hereby, the arising of areas with local hard wind on the leeward side of the drift shield is consequently avoided.
In a preferred embodiment, the plastic sheeting is transparent and made of a weatherproof plastic material, such as polyethene, polyethene terephtalate or the like. The thickness of the plastic sheeting is suitably in the interval of 0.1 to 1 mm, preferably between 0.2 to 0.6 mm.
In another preferred embodiment, the number of dynamic wind dampers in the plastic sheeting is between 25 and 75 per m2, preferably between 40 and 60 per m2. The distance between the upper ends of the two legs of the V-shaped cuts of the dynamic wind dampers is suitably between 5 and 15 cm, preferably between 8 and 12 cm, and the angle between the two legs of the V-shaped cuts of the dynamic wind dampers is suitably in the interval between 45 and 135°, preferably between 75 and 105°.
In a preferred embodiment, the at least two longitudinal stiffening strips are joined to the plastic sheeting, for instance by using a joining technique such as welding, gluing etc.
The invention will in the following be more closely described by means of embodiment examples, with reference to the appended drawings, in which:
The drift shield according to the embodiments described below is suitable to be used for protecting objects against drifting snow or sand. However, the invention is not limited to snow shields or sand shields. On the contrary, the invention can also be used in order to protect objects against other drifting airborne materials.
A part of a drift shield according to an embodiment of the invention is shown in
The plastic sheeting 2 is preferably of a transparent material so as to not obstruct the visibility for road-users or the like when the drift shield for instance is used as a snow shield along a road. Suitable materials for the plastic sheeting 2 can be all types of weatherproof plastic materials, since the drift shield is used in outdoor environments and is to stand i.a. chilliness, heat, moisture and UV radiation. Examples of suitable materials can be polyethene or polyethene terephthalate, but other plastic materials with weatherproof properties may also be used. The thickness of the plastic sheeting 2 is normally in the interval of 0.1 to 1 mm depending on the prevailing weather and wind conditions at the place where the drift shield is to be mounted. In most of the normal cases, it is sufficient with a thickness of the plastic sheeting between 0.2 to 0.4 mm.
The plastic sheeting 2 is shown completely smooth and without any cuts or other openings in
The principle how the drift shield functions in order to essentially eliminate Huygens' Principle will be described with reference to
The drift shield has been described in closer detail above by means of a number of embodiments. To get a further understanding of the invention and notice further advantages, it will now be described how a drift shield can be mounted for instance along a road.
The invention is of course not in any way limited to the embodiments described above. On the contrary, several possibilities to modifications thereof should be apparent to a person skilled in the art without thereby deviating from the basic idea of the invention such as defined in the appended claims.
Claims
1. A drift shield adapted to be fastened to essentially vertical posts (6) arranged in the ground and comprising a plastic sheeting (2), wherein
- at least two longitudinal stiffening strips (4), which are essentially parallel in relation to the ground, are joined to the plastic sheeting (2) along the whole length of the plastic sheeting (2),
- dynamic wind dampers (12) in the form of several V-shaped cuts are arranged in the plastic sheeting (2) in a such a manner that they allow wind to pass through,
- the V-shaped cuts of the dynamic wind dampers (12) are arranged in columns,
- the dynamic wind dampers in the same column being located vertically straight under each other, and
- the dynamic wind dampers in two adjacent columns being vertically offset in relation to each other.
2. A drift shield according to claim 1, wherein the plastic sheeting (2) is made of a weatherproof plastic material, such as polyethene, polyethene terephthalate or the like.
3. A drift shield according to claim 1, wherein the number of dynamic wind dampers (12) in the plastic sheeting (2) is between 25 and 75 per m2, preferably between 40 and 60 per m2.
4. A drift shield according to claim 1, wherein the longitudinal stiffening strips (4) are joined to the plastic sheeting (2).
5. A drift shield according to claim 1, wherein the drift shield can be rolled up.
6. A drift shield according to claim 1, wherein the drift shield comprises mounting lathes (8), which are configured to extend along the posts (6) with the plastic sheeting (2) arranged between the mounting lathe (8) and the posts (6).
7. A drift shield according to claim 1, wherein the width (x) of the V-shaped cuts of the dynamic wind dampers (12) is between 5 and 15 cm, preferably between 8 and 12 cm.
8. A drift shield according to claim 1, wherein the angle (α) between the two legs (12a, 12b) of the V-shaped cuts of the dynamic wind dampers (12) is in the interval between 45 and 135°, preferably between 75 and 105°.
9. A drift shield according to claim 1, wherein the plastic sheeting (2) is transparent.
10. A drift shield according to claim 1, wherein the plastic sheeting (2) has a thickness in the interval of 0.1 to 1 mm, preferably between 0.2 to 0.6 mm.
11. A drift shield according to claim 2, wherein the number of dynamic wind dampers (12) in the plastic sheeting (2) is between 25 and 75 per m2, preferably between 40 and 60 per m2.
12. A drift shield according to claim 11, wherein the longitudinal stiffening strips (4) are joined to the plastic sheeting (2).
13. A drift shield according to claim 3, wherein the longitudinal stiffening strips (4) are joined to the plastic sheeting (2).
14. A drift shield according to claim 2, wherein the longitudinal stiffening strips (4) are joined to the plastic sheeting (2).
15. A drift shield according to claim 4, wherein the drift shield can be rolled up.
16. A drift shield according to claim 13, wherein the drift shield can be rolled up.
17. A drift shield according to claim 12, wherein the drift shield can be rolled up.
18. A drift shield according to claim 11, wherein the drift shield can be rolled up.
19. A drift shield according to claim 4, wherein the drift shield can be rolled up.
20. A drift shield according to claim 3, wherein the drift shield can be rolled up.
Type: Application
Filed: Jun 12, 2013
Publication Date: Nov 12, 2015
Inventor: Lennart Lyhamn (Ånäset)
Application Number: 14/410,726