GB2546753B - A rotatable unit for a barrier - Google Patents

Description

TITLE OF THE INVENTION A Rotatable Unit for a Barrier

FIELD OF THE INVENTION

The present invention relates to a rotatable unit for a barrier. The present invention also relates to a tube and tool for forming the rotatable unit and a method of forming the rotatable unit.

BACKGROUND OF THE INVENTION

Traditionally, apparatus, such as broken glass and spikes, have been used on the top of perimeter structures, such as walls, to deter intrusion. Such apparatus has an unsightly appearance and is relatively easy for intruders to overcome.

An improvement on the traditional apparatus is to use barriers with movable parts. The movable parts are able to rotate so that when an intruder puts weight on the part it rotates towards the ground. Therefore, the intruder is denied a static hand/foot hold and the barrier is more difficult to circumvent.

However, the current barriers comprise movable spikes or blades which have sharp or jagged edges. The sharp or jagged edges are a result of the manufacturing process and can cause injuries to people who comes into contact with the blade edges.

Therefore, the spike or blades presently used on the current barriers are not fit for the purpose of purely deterring intruders and are not suitable for use in areas for children where the barrier is needed to prevent access but not to cause injury.

SUMMARY OF THE INVENTION

The invention is defined by the independent claims. The dependent claims define advantageous embodiments.

According to an aspect of the present invention, there is provided a rotatable unit for a barrier, the rotatable unit being configured to be rotatable about a support shaft, the rotatable unit comprising a tubular portion through which the support shaft is configured to extend, and a plurality of blades extending outwardly of the tubular portion, the blades comprising first and second blades surfaces, each blade surface comprising first and second longitudinal edges, and first and second connecting edges arrangements, each edge arrangement connecting one of the longitudinal edges of the first blade surface to one of the longitudinal edges of the second blade surface, each of the connecting edge arrangements comprising at least a first portion, the first portion adjoining, and extending along, a longitudinal edge of one of the first and second blade surfaces, wherein said connecting edge arrangement further comprises a second portion, said second portion adjoining said first portion, and having a profile which varies along the length of said connecting edge arrangement in the longitudinal direction..

This aspect may be modified according to any feature as described herein, including any examples described herein and any of the following optional features.

The first portion may extend continuously along a longitudinal edge of one of the first and second blade surfaces. The first portion may extend along the majority of the longitudinal edge, preferably at least 50% of the length of the longitudinal edge. The first portion may form a strip of surface running along the length of the blade.

The first portion may, about a blade cross section perpendicular to the length of the blade, have a cross sectional profile having one end adjoining a said longitudinal edge and another end extending in a direction away from said first and second blade surfaces. Preferably this profile is substantially continuous along the length of the blade.

The connecting edge arrangement may further comprise a third portion adjoining, and extending along, a longitudinal edge of the other of the first and second blade surfaces.

The third portion may, about a blade cross section perpendicular to the length of the blade, have a cross sectional profile having one end adjoining a said longitudinal edge and another end extending in a direction away from said first and second blade surfaces. Preferably this profile is substantially continuous along the length of the blade.

Any of the first and third portions may form a strip of surface running along the length of the blade.

The connecting edge arrangement may therefore, about a blade cross section perpendicular to the length of the blade, comprise: the first portion extending from one of the longitudinal edges of the first and second blade surfaces and adjoining an end of the second portion, the third portion extending from the other of the longitudinal edges of the first and second blade surfaces and adjoining the other end of the second portion. TThe blades may extend outwardly at an angle to the axis of the tubular portion and are spaced apart.

Preferably, the blades extend from one end of the tubular portion. The blades may be longitudinally curved and surround said tubular portion. Preferably, each of the blades is curved transversely to its longitudinal extent. Each of the blades may be curved through an angle greater than 180 degrees transversely to its longitudinal extent.

The rotatable unit may comprise first and second longitudinal ends, the first end comprising the plurality of outwardly extending blades and the second end comprising a plurality of channels indented from at least one of an inner surface and an outer surface, the channels extending at least partially along the length of the tubular portion, at least the first end of the tubular portion having been urged outwardly to tear the tubular portion at least partially along the length of the channels to form the plurality of blades and to define an untom second end.

Preferably, the second portion of the connecting edge arrangement is formed from a connecting portion of the tubular portion, the connecting portion radially adjacent to the channels, part of the tubular portion having been urged outwardly to form a tear through the connecting portions to form the plurality of blades and define the second section of the blade edge.

Optionally, the first portion of the connecting edge arrangement extends into one of the first or second blade surfaces by a distance of between 0.25 mm and 1 mm. Preferably, the first portion of the connecting edge arrangement extends into one of the first or second blade surfaces by a distance of between 10% and 45% of the blade thickness.

Optionally, the first portion of the connecting edge arrangement extends from one of the first or second blade surfaces laterally in a direction away from the first and second blade surfaces by a distance of between 0.25 mm and 2 mm. Preferably, the first portion of the connecting edge arrangement extends from one of the first or second blade surfaces laterally in a direction away from the first and second blade surfaces by a distance of between 9% and 80% of the tube thickness.

In one embodiment, the first portion of the connecting edge arrangement is an arc having a radius between 0.5 mm and 2.5 mm.

According to another aspect of the present invention, there is provided a tube for forming a rotatable unit comprising first and second longitudinal ends and a plurality of channels indented from at least one of an inner surface and an outer surface, the plurality of channels extending at least partially along the length of the tube from the first longitudinal end.

This aspect may be modified according to any feature as described herein, including any examples described herein and any of the following optional features.

The tube may comprise a plurality of channels indented from both the inner and outer surfaces of the tube.

Each outer surface channel may be radially aligned with an inner surface channel.

Preferably, the plurality of channels extend in a direction parallel to the longitudinal axis of the tube. Optionally, the tube comprises a plurality of channels indented from the inner surface and in the outer surface, each channel indented from the outer surface being disposed radially outward of a corresponding channel indented from the inner surface.

Optionally, the channel indents from at least one of the inner surface and the outer surface by a distance of between 0.25 mm and 1 mm. Preferably, the channel indents from at least one of the inner surface and the outer surface by a distance of between 10% and 45% of the tube wall thickness.

In one embodiment, the channel indent is formed by rounded edges having a radius of between 0.1 mm and 0.5 mm.

Optionally, the channel indent from at least one of the inner surface and the outer surface has a width of between 0.5mm and 2.5 mm. Preferably, the channel indent from at least one of the inner surface and the outer surface has a width of between 18% and 100% of the tube thickness.

According to another aspect of the present invention, there is provided a barrier comprising a support shaft, and a plurality of rotatable units according to any of claims 1 to 14.

According to yet another aspect of the present invention, there is provided a method of forming a rotatable unit for a barrier comprising: driving a tool into a tube to form the rotatable unit, the tube comprising first and second longitudinal ends, a plurality of channels indented from at least one of an inner surface and an outer surface, the plurality of channels extending at least partially along the length of the tube from the first longitudinal end, the tool comprising a first portion configured to fit inside the tube and a second portion having at least one cross-sectional dimension larger than the diameter of the tube, wherein driving the tool into the tube comprises: inserting the first portion of the tool into the first end of the tube, and driving the tool at least partially along the length of the tube parallel to the longitudinal axis of the tube, such that the tool outwardly urges the inner surface of the tube and tears the tube at least partially along the length of the channels to form a plurality of blades.

This aspect may be modified according to any feature as described herein, including any examples described herein and any of the following optional features.

The method may be configured such that driving the tool comprises urging a cone-shaped second portion of the tool against the inner surface of the tube to outwardly urge the inner face to tear the tube at least partially along the length of the channels to form the plurality of blades.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 shows a view along the longitudinal axis of a first embodiment of a rotatable unit for a barrier from a tubular portion end;

Fig. 2 shows a view along the longitudinal axis of the rotatable unit, shown in Fig. 1, from a blade end;

Fig. 3 shows a side on view of a second embodiment of the rotatable unit;

Fig. 4 shows a side on view of a tube for forming the rotatable unit shown in

Fig. 1;

Fig. 5 shows a view along a longitudinal axis of a tube for forming the rotatable unit, shown in Fig. 1, from a first longitudinal end;

Fig. 6 shows a side view of a tool for forming a rotatable unit;

Fig. 7 shows the tool, shown in Fig. 6, partially driven into the tube, shown in Fig. 4, for forming the rotatable barrier, shown in Fig. 1; and

Fig. 8 shows a barrier comprising a plurality of rotatable units attached to a wall.

DETAIFED DESCRIPTION OF THE EMBODIMENTS

Fig. 1 to Fig. 3 show two embodiments of a rotatable unit 1, 20 for a barrier, shown in Fig. 8. The rotatable unit 1 comprises a tubular portion 2 and a plurality of blades 3. In the present embodiment, the tubular portion 2 is substantially cylindrical and has a support shaft receiving space 4 through which a support shaft, shown in Fig. 8, is configured to extend. The plurality of blades 3 extend outwardly of one end of the tubular portion 2. The embodiment shown in Fig. 1 comprises three blades 3 which extend generally in a radial direction and are spaced equally from one another. However, it will be understood that in an alternative embodiment the number of blades and direction in which they extend may differ.

Referring to Fig. 1 and Fig. 2, it can be seen that each blade 3 comprises a first blade surface 6, shown in Fig. 1, and a second blade surface 7, shown in Fig. 2. The first blade surface 6 corresponds to an outer surface 8 of the tubular portion 2 and the second blade surface 7 corresponds to an inner surface 9 of the tubular portion 2. In the present embodiment, the first blade surface is convex and the second blade surface 7 is concave. The first blade surface 6 comprises a first longitudinal edge 11 and a second longitudinal edge 12, shown in Fig. 1. The second blade surface 7 comprises a first longitudinal edge 13 and a second longitudinal edge 14, shown in Fig. 2.

Each blade 3 further comprises a first connecting edge arrangement 15 and a second connecting edge arrangement 16, shown in Fig. 2. The first connecting edge arrangement 15 connects the first longitudinal edge 11 of the first blade surface 6 to the first longitudinal edge 13 of the second blade surface 7. The second connecting edge arrangement 16 connects the second longitudinal edge 12 of the first blade surface 6 to the second longitudinal edge 14 of the second blade surface 7.

Each of the connecting edge arrangements 15, 16 comprises at least a first portion 17. The at least first portion 17 adjoins, and extends continuously along, one of the longitudinal edges 11, 12, 13, 14 of one of the first and second blade surfaces 6, 7. The first portion 17 extends laterally in a direction away from the first and second blade surface 6, 7 and has a profile which is substantially the same along the longitudinal edge 11, 12, 13, 14 from which it extends.

In the present embodiment, the connecting edge arrangements 15, 16 comprise three portions. The first portions 17 extend from the first and second longitudinal edges 13, 14 of the second blade surface 7 to second portions 18. Third portions 19 extend from the first and second longitudinal edges 11, 12 of the first blade surface 6 of the second portion 18. The first and third portions 17, 19 extend laterally with an arced profile towards the second portion 18, although these portions may have other cross sectional profiles. In the present embodiment, the first and third portions 17, 19 are substantially mirror images of one another about a plane of symmetry down the middle of the blade cross section.

That is, the first and third portions 17, 19 of the connecting edge arrangements 15, 16 have substantially the same profile but because they extent from longitudinal edges 11, 12, 13, 14 on opposing blade surfaces 6, 7, they converge together.

As will be explained hereinafter, the connecting edge arrangements 15, 16 are formed by tearing the blades 3 apart. The tear propagates down a channel indented in the surface of a tube, shown in Figs. 4 and 5. The channel is symmetric such that the tube thickness is thinnest adjacent to the middle of the channel which encourages the tear to propagate along the middle of the channel. Therefore, when the blades 3 are formed the channel is split substantially in half to create first and third portions 17, 19 with substantially symmetrical profiles. The tear propagates longitudinally along the middle of the channel of the tube producing substantially symmetrical profiles along the length of the blades 3.

The first portions 17 are formed by channels indented on the outside surface of the tube and the third portions are formed by channels indented on the inside surface of the tube. As the first and third portions 17, 19 are already preformed before the blades 3 are defined, they have smooth surfaces which help to prevent injury to a person who comes into contact with them. The majority of the profile of the first and third portions 17, 19 will be substantially symmetrical and have similar profiles.

The second portion 18 is located between the first and third portions 17, 19 and is formed when adjacent blades 3 are urged apart from one another, as will be described hereinafter. The second portions 18 are formed by the surfaces created when the tear propagates longitudinally along the channel. As the tear propagates longitudinally along the channel, localised material properties will vary. Therefore, the second portion 18 has a rough surface, which varies along the length of the blade, compared to the surfaces of the first and third portions 17, 19. The tearing action may also cause localised thinning of the material proximate the second portions 18 due to the strains induced in the material.

The at least first portion 17 of the connecting edge arrangement 15, 16 may comprise a surface having an arced profile wherein the arc has a radius of between 0.5 mm and 2.5 mm. Furthermore, in one embodiment, the longitudinal edge 11, 12, 13, 14 of the blades 3 may also comprise a rounded edge having a radius of between 0.5 mm and 2.5 mm. In the present embodiment, the first and third portions 17, 19 have a concave profile. However, in an alternative embodiment, the profile of the first and third portions 17, 19 may be, for example, but not limited to, linear or convex.

The second portion 18 has a profile which varies along the length of said connecting edge arrangement in the longitudinal direction. This is because the second portions 18 of the connecting edge arrangements 15, 16 are formed by a tear, as will be further explained hereinafter.

The at least one portion extending continuously along one of the longitudinal edges and laterally in a direction away from the blade surfaces 6, 7 helps to reduce, if not prevent, the formation of a blade that is sharp or jagged enough to cause injury to anyone who may come into contact with the blade.

The at least first portion 17 of the connecting edge arrangement 15, 16 may extend transversely from one of the longitudinal edges 11, 12, 13, 14 of one of the blade surfaces 6, 7 by a distance of between 0.25 and 1 mm. Preferably, the at least first portion 17 of the connecting edge arrangement 15, 16 may extend transversely from one of the longitudinal edges 11, 12, 13, 14 of one of the blade surfaces 6, 7 by a distance of between 10% and 45 % of the blade 3 thickness.

The at least first portion 17 of the connecting edge arrangement 15, 16 may extend laterally from one of the longitudinal edges 11, 12, 13, 14 in a direction away from one of the blade surfaces 6, 7 by a distance of between 0.25 mm and 2 mm. Preferably, the at least first portion 17 of the connecting edge arrangement 15, 16 may extend laterally from one of the longitudinal edges 11, 12, 13, 14 in a direction away from one of the blade surfaces 6, 7 by a distance of between 9% and 80% of the blade 3 thickness.

Referring now to Fig. 3, a side view of a second embodiment of a rotatable unit 20 is shown. The second embodiment of the rotatable unit 20 comprises four equally spaced blades 3. However, due to the side on view of Fig. 3, only three blades can be seen. Each of the blades 3 extends outwardly at an angle to the longitudinal axis and from one end of the tubular portion 2. Furthermore, the blades 3 are longitudinally curved so that they rotate through at least 180 degrees. Optionally, the blades 3 may surround tubular portion 2 and/or may be curved transversely to their longitudinal extent.

In an alternative embodiment, the blades 3 of the rotatable unit 1, 20 are curved through an angle of greater than 180 degrees transversely to its longitudinally extent. Therefore, the far end of each blade 3 is pointing in a direction towards the longitudinal axis of the tubular portion 2. This helps to reduce the risk of a person impaling part of their body on the blades 3 of the rotatable unit because the ends of the blades 3 do not face outwards.

Referring to Figs. 4 and 5, a side view and a front view of a tube 25 for forming the rotatable unit 1, shown in Figs. 1 and 2, is shown. The tube 25 has a first longitudinal end 26 and a second longitudinal end 27, shown in Fig. 4. The tube 25 is formed from a larger extruded tube (not shown) which is preferably between 1.5 m and 6 m in length. The larger tube 25 is then cut to provide multiple tubes 25. The tube 25 is preferably between 100 mm and 500 mm long. Even more preferably, the tube 25 is between 200 mm and 300 mm long. The tube 25 may be formed from, for example, but not limited to, Aluminium alloy 6082 in T4 condition.

The tube 25 comprises an inner surface 28 and an outer surface 29, shown in Fig. 5. The inner and outer surfaces 28, 29 of the tube have generally circular profiles. However, in alternative embodiments, the profile of the inner surface 28 may remain circular whilst the profile of the outer surface 29 may take any other shape.

The tube 25 further comprises a plurality of channels 31 indented from at least one of the surfaces 28, 29. The channels 31 define the edges of the unseparated blade surfaces. In the present embodiment, the tube 25 comprises three channels 31 indented from the inner surface 28 of the tube 25 and three channels indented from the outer surface 29 of the tube 25. The channels 31 extend the length of the tube 25 from the first longitudinal end 26 to the second longitudinal end 27. However, it will be understood that in an alternative embodiment, the channels 31 may begin at the first longitudinal end 26 of the tube 25 and end before they reach the second longitudinal end 27. In the present embodiment, the channels 31 extend in a direction parallel to the longitudinal axis of the tube 25 and perpendicularly to an end face 32 of the tube 25

Furthermore, in the present embodiment, the channels 31 indented in the outer surface 29 are located radially outwards of the channels indented in the inner surface 28 such that the channels 31 are formed in radial pairs. In the present embodiment, the channels 31 are equally spaced around the circumference of the inner and outer surfaces 28, 29.

However, it will be understood that the number and location of the channels 31 may be alternately arranged. For example, the channels 31 may only be formed in one of the surfaces 28, 29, the channels 31 may be formed at random intervals, or the channels 31 may not be formed in pairs.

In the present embodiment, the plurality of channels 31 are formed from “U-shaped” cut-outs. However, the plurality of cut-outs may be formed by, for example, but not limited to, “V-shaped” cut-outs, slits, or square cut-outs.

The plurality of channels 31 may indent from at least one of the inner and outer surfaces 28, 29 of the tube 25 by a distance of between 0.2 mm and 1mm. Preferably, the plurality of channels 31 indent from at least one of the inner and outer surfaces 28, 29 of the tube 25 by a distance of between 10% and 45% of the tube wall thickness.

The width of the plurality of channels 31 which indent from at least one of the inner and outer surfaces 28, 29 of the tube 25 may be between 0.5 mm and 2.5 mm. Preferably, the width of the plurality of channels 31 which indent from at least one of the inner and outer surfaces 28, 29 of the tube 25 may be between 18% and 100% of the tube wall thickness.

Referring now to Fig. 6, there is shown a side view of a tool 35 used for forming the rotatable unit 1, 20 from the tube 25. The tool 35 comprises a first portion 36. The first portion 36 is configured to fit inside the tube 25. The tool 35 further comprises a second portion 37. The second portion 37 comprises at least one cross-sectional dimension which is larger than the inner diameter of the tube 25. The cross section here being the cross section perpendicular to the length of the tool 35. Preferably, the second portion 37 of the tool 35 is inclined relative to the longitudinal axis of the tube 25 when the tool 35 is being used to form a rotatable unit 1, 20 from the tube 25.

In the present embodiment, the first portion 36 is a cylindrical element. The cylindrical element may be substantially the same size as the inner diameter of the tube 25 so that the first portion 36 fits into the tube 25. Therefore, the cylindrical element 36 is able to help ensure that the tool travels longitudinally along the tube 25 when forming the rotatable element 1, 20. This helps to provide blades 3 that curve without twisting. The cylindrical element 36 may also help to prevent buckling of the tube 25.

In the present embodiment, the second portion 37 comprises a conical section which extends from one end of the cylindrical element 36. The conical section 37 is wider further from the cylindrical element 36 so that the dimensions of its cross-section begin smaller than the inner diameter of the tube 25 and are wider than the inner diameter of the tube 25 at the opposite end of the conical section 37. The incline of the surface of the conical section 37 influence the curvature of the blades 3 of the rotatable unit 1, 20. Preferably, the angle of the inclined face of the conical section is between 10 and 60 degrees relative to the longitudinal axis of the tool 35.

The tool 35 further comprises a main body 38. The main body 38 may be attached to a driver (not shown) which is configured to drive the tool 35 along the longitudinal axis of the tube 25 to form the rotatable unit 1, 20, as will be described hereinafter. In the present embodiment, the main body 38 is cylindrical. The tool 35 may be formed from, for example, but not limited to, hardened steel. A method for forming a rotatable unit 1, 20 for a barrier comprises driving the tool 35 into a tube 25 to form the rotatable unit 1, 20. Driving the tool 35 into the tube 25 comprises inserting the first portion 36 of the tool 35 into the first longitudinal end 26 of the tub 25, as shown in Fig. 7, and driving the tool 35 at least partially along the length of the tube 25 parallel to the longitudinal axis of the tube, such that the tool 35 outwardly urges the inner surface 28 of the tube 25 and tears the tube 25 at least partially along the length of the channels 31 to form a polarity of blades 3.

When the tool 35 is inserted into the tube 25, the cylindrical element 36 is located proximate to the inner surface 28 of the tube 25 and the inner surface 28 at the first longitudinal end 26 contacts the conical section 37 of the tool 35. The second longitudinal end 27 of the tube 25 is fixed and the tool 35 is driven in a direction parallel to the longitudinal axis of the tube 25.

As the tool 35 is driven along the longitudinal axis, a cross-section of the conical section 37 with a wider diameter than the inner diameter of the tube 25 is forced into the tube 25. The stress in the tube 25 causes it to deform and begin to move outwardly. The stress in the tube 25 is more highly concentrated in the material located between the pairs of channels 31, a connecting portion 40, where the thickness of the tube wall is smaller. Alternatively, the connecting portion 40 may be located between a channel 31 and one of the inner and outer surfaces 28, 29 of the tube 25. Therefore, the material fails in the connecting portions 40 adjacent the plurality of channels 31 and forms the second portion 18. The channel 31 is split in two and forms the at least first portion 17 which connects the longitudinal edges 11, 12, 13, 14 to second portion 18. The plurality of blades 3 begin to be formed as tears propagate along the channels 31 and the second portion 18 is formed.

As the tool 35 continues to be driven into the tube 25, the same process as above occurs to subsequent sections of the tube 25. This means that the newly formed sections of the plurality of blades 3 are constantly being deflected to form curved blades 3 as shown in Figs. 1 to 3. It will be understood that in an alternative embodiment, the tool 35 will be fixed in place and the tube 25 will be driven over the tool 35.

Fig. 8 shows an end view of a barrier 50 which is fixed to extend along the top of a wall 52. The barrier 50 comprises a plurality of rotatable units 1, such as those described above, each having a plurality of outwardly extending blades 3. The rotatable units 1 are supported on a support shaft 57 which is mounted to extend along the top of the wall 52.

Support means are provided for fixing the barrier 50 to the wall 52. In the embodiment illustrated, the support means comprise a number of support posts 58 connected to the support shaft 57 along its length. Each said support post 58 is connected to the wall 52 to fix the barrier 50 in position. Each support post 58 may be cranked so that it can be connected, for example by screws (not shown), to the inner surface of the wall 52. This denies access to any intruder to the screws or other fixing means, whereby removal of the barrier to gain access is prevented. The support posts 58 are sized and shaped such that the shaft 57 of the barrier 50 extends along the top of the wall approximately centrally of its inner and outer surfaces.

In Fig. 8, the rotatable units 1 are shown positioned so that the blades of adjacent units interengage. In an alternative embodiment, adjacent rotatable units 1 may not interengage.

The barrier 50 comprises a plurality of rotatable units 1 spaced along the support shaft 57 and arranged to be rotatable with respect thereto. The support shaft 57 extends through the tubular portions 2 of each rotatable unit 1. A tubular spacer member 56 is arranged on the support shaft 57 in between facing rotatable units 1 to space two adjacent units 1 apart.

The support posts 58 which fix the barrier 50 to the wall 52 arc each connected to the support shaft 57 by a respective support connector (not shown). The support connector is generally T-shaped and comprises a first tubular portion (not shown) in which the shaft 57 is arranged to extend. A second tubular portion (not shown) in which the support post 58 is received extends substantially at right angles to the first tubular portion.

It would be possible to form the barrier 50 using just a single shaft 57 of the required length. However, for ease of providing barriers of any required length, it is preferred that a number of shafts 57 of standard length are utilised. The adjacent ends of adjacent lengths of shaft 57 are connected together to form a shaft 57, and hence the barrier 50, of the required length. To enable this, a connector (not shown) in the form of a tubular member is provided so that adjacent ends of two adjacent shafts 57 can be received therein.

It will be understood that the components of the barrier may be alternately arranged to accommodate the space available for the barrier and to vary the space between adjacent rotatable units 1.

The above embodiments as described are only illustrative, and not intended to limit the technique approaches of the present invention. Although the present invention is described in details referring to the preferable embodiments, those skilled in the art will understand that the technique approaches of the present invention can be modified or equally displaced without departing from the spirit and scope of the technique approaches of the present invention, which will also fall into the protective scope of the claims of the present invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. Any reference signs in the claims should not be construed as limiting the scope.

Claims (20)

1. A rotatable unit for a barrier, said rotatable unit being configured to be rotatable about a support shaft, the rotatable unit comprising: a tubular portion through which said support shaft is configured to extend, and a plurality of blades extending outwardly of said tubular portion, said blades comprising: first and second blades surfaces, each blade surface comprising first and second longitudinal edges, and first and second connecting edges arrangements, each edge arrangement connecting one of the said longitudinal edges of said first blade surface to one of the said longitudinal edges of said second blade surface, each of said connecting edge arrangements comprising at least a first portion, said first portion adjoining, and extending along, a longitudinal edge of one of said first and second blade surfaces, wherein said connecting edge arrangement further comprises a second portion, said second portion adjoining said first portion, and having a profile which varies along the length of said connecting edge arrangement in the longitudinal direction.

2. The rotatable unit according to claim 1, wherein the first portion extends continuously along the longitudinal edge of one of the first and second blade surfaces.

3. The rotatable unit according to claim 2, wherein the first portion extends along the majority of the longitudinal edge.

4. The rotatable unit according to any one of the preceding claims, wherein the first portion, about a blade cross-section perpendicular to the length of the blade, has a cross-sectional profile having one end adjoining one of said longitudinal ends and another end extending in a direction away from said first and second blade surfaces.

5. The rotatable unit according to claim 4, wherein the profile is substantially continuous along the length of the blade.

6. The rotatable unit according to any one of the preceding claims, wherein said connecting edge arrangement further comprises a third portion adjoining, and extending along, a longitudinal edge of the other of the first and second blade surfaces.

7. The rotatable unit according to claim 6, wherein the third portion, about a blade cross-section perpendicular to the length of the blade, has a cross-sectional profile having one end adjoining said longitudinal edge and another end extending in a direction away from said first and second blade surfaces.

8. The rotatable unit according to claim 7, wherein the profile is substantially continuous along the length of the blade.

9. The rotatable unit according to any one of the preceding claims, wherein the connecting edge arrangement, about a cross-section perpendicular to the length of the blade, comprises: the first portion extending from one of the longitudinal edges of the first and second blade surfaces and adjoining an end of the second portion, the third portion extending from the other longitudinal edges of the first and second blade surfaces and adjoining the other end of the second portion.

10. The rotatable unit according to any one of the preceding claims, wherein said blades extend outwardly at an angle to the axis of said tubular portion and are spaced apart.

11. The rotatable unit according to any one of the preceding claims, wherein said blades extend from one end of the tubular portion.

12. The rotatable unit according to any one of the preceding claims, wherein said blades are longitudinally curved and surround said tubular portion.

13. The rotatable unit according to any one of the preceding claims, wherein each of said blades is curved transversely to its longitudinal extent.

14. The rotatable unit according to claim 13, wherein each of said blades is curved through an angle greater than 180 degrees transversely to its longitudinal extent.

15. The rotatable unit according to any one of the preceding claims, wherein the tubular portion comprises first and second longitudinal ends, the first end comprising the plurality of outwardly extending blades and the second end comprising a plurality of channels indented from at least one of an inner surface and an outer surface, said channels extending at least partially along the length of said tubular portion, at least the first end of said tubular portion having been urged outwardly to tear said tubular portion at least partially along the length of said channels to form said plurality of blades and to define an untorn second end.

16. The rotatable unit according to claim 15, wherein said second portion of said connecting edge arrangement is formed from a connecting portion of said tubular portion, said connecting portion radially adjacent to said channels, part of said tubular portion having been urged outwardly to form a tear through said connecting portions to form said plurality of blades and define said second section of said blade edge.

17. The rotatable unit according to any one of the preceding claims, wherein said first portion of said connecting edge arrangement extends from one of said first or second blade surfaces laterally in a direction away from said first and second blade surfaces by a distance of between 0.25 mm and 2 mm.

18. The rotatable unit according to any one of the preceding claims, wherein said first portion of said connecting edge arrangement extends from one of said first or second blade surfaces laterally in a direction away from said first and second blade surfaces by a distance of between 9% and 80% of the blade thickness.

19. The rotatable unit according to any one of the preceding claims, wherein said first portion of said connecting edge arrangement is an arc having a radius between 0.5 mm and 2.5 mm.

20. A barrier comprising a support shaft, and a plurality of rotatable units according to any of claims 1 to 13.