IES20080117A2 - A barrier - Google Patents

Abstract

A barrier 1 for preventing the passage of a ball is disclosed. The barrier 1 comprises a pair of uprights 102, 104 mounted spaced-apart from each other; a pulley system mounted on the uprights; a working wire 136 engaging the pulley system, and extending between the uprights; and a screen 108 depending from at least one bracing wire 110, 112, 114 which extends between the uprights 102, 104. The pulley system is operable to move the screen 108 to and from a furled position adjacent one upright 104 and an unfurled position extending between the uprights 102, 104. Additionally, a ground-engaging support unit 106 for mounting the uprights 102, 104 is disclosed. The support unit comprises guiding blocks 500, 600 for correctly positioning the upright and adjustable clamps 220 for aligning the upright 102, 104 and maintaining the correct alignment. <Figure 1>

Description

The present invention relates to a barrier for preventing the passage of a ball. More particularly, the present invention relates to a barrier for preventing the passage of a ball, the barrier comprising a pair of uprights adapted to be mounted spaced-apart from each other; a pulley system adapted to be mounted on the uprights; a working wire adapted to engage the pulley system so as to form an upper working wire and a lower working wire, each extending between the uprights; a screen having an upper horizontal edge and a lower horizontal edge and adapted to extend between the upper working wire and the lower working wire; the pulley system, in use, being operable to move the screen to and from a furled position adjacent one upright and an unfurled position extending between the uprights. Such barriers are often used behind goalposts or the like on a sporting ground or on a golf course.

In many sports grounds, such as golf courses or football and rugby pitches, it is often desirable to be able to prevent the passage of a ball at a certain location. This may be, for example, at the boundary of the sports ground so as to prevent the inconvenience of balls being lost across the boundary and to prevent the balls causing damage to property adjacent the sports ground. Additionally, in some circumstances it may be necessary to prevent the passage of the ball into a spectator area which could be very dangerous.

United Kingdom Patent No. GB 2 324 474 discloses a screen to limit the flight of balls comprising a pair of spaced apart uprights, a screen that is supported by and extendible between the uprights and a pulley system for furling and unfurling the screen comprising a winch rope connected to the top and base of screen.

There are however a number of problems associated with the disclosed screen. Firstly, the operation of the screen can be compromised by overly windy conditions. In such conditions, the screen is inclined to billow. This billowing causes the edges of the screen to be pulled inwards towards the centre of the screen, in particular pulling the top edge of the screen down and the lower edge of the screen upwards. This in turn reduces the -2effective area of the screen, thereby reducing its effectiveness at preventing balls from passing. Secondly, the pulling of the bottom of the screen will put extra pressure on the winch rope, thereby making it very difficult to operate the furling and unfurling mechanism in windy conditions.

It is an object therefore of the present invention to provide a barrier whose use and effectiveness is not compromised by windy conditions.

Statements of Invention According to the invention there is provided a barrier for preventing the passage of a ball, the barrier comprising a pair of uprights adapted to be mounted spaced-apart from each other; a pulley system adapted to be mounted on the uprights; a working wire adapted to engage the pulley system so as to form an upper working wire and a lower working wire, each extending between the uprights; a screen having an upper horizontal edge and a lower horizontal edge and adapted to extend between the upper working wire and the lower working wire; the pulley system, in use, being operable to move the screen to and from a furled position adjacent one upright and an unfurled position extending between the uprights, characterized in that the barrier further comprises a bracing wire, adapted to extend between the uprights and to be coupled to one horizontal edge of the screen In this way, the use of the bracing wire provides additional stiffness to the screen so that billowing is reduced, thereby preventing the reduction of area of the screen and associated reduction in effective ness of the barrier. Additionally, the extra tension on the horizontal edge of the screen due to the billowing now acts on the bracing wire and not on the working wire, so the billowing does not place extra pressure on the working wire, thereby allowing the screen to be furled and unfurled effectively, even in windy conditions.

In one embodiment of the invention there is provided a barrier further comprising a pair of ground-engaging support units adapted to mount the uprights. In this way, erecting the barrier of the invention is greatly simplified. In the absence of such ground-engaging support units, the uprights would be mounted in a cement foundation, thereby requiring those installing the uprights to engage in cement mixing or to engage others to carry out -3the operation, at the same time as the uprights are ready to be installed. By using ground-engaging support units, this problem can be overcome as the support units can be installed prior to the installation of the uprights, and no co-ordination of personnel is required on the day of installation. Furthermore, the process involved in installing an upright in a pre-existing ground-engaging unit is much simpler than that of erecting an upright in a foundation of wet cement.

In another embodiment of the invention there is provided a barrier comprising a plurality of bracing wires adapted to extend between the uprights and to be coupled to the screen. In this way, billowing of the screen can be further reduced, and its associated disadvantages minimised.

In another embodiment of the invention there is provided a barrier comprising a pair of bracing wires each adapted to extend between the uprights and to be coupled to one horizontal edge of the screen. In this way, an upper bracing wire and lower bracing wire are provided, each reducing billowing by increasing the stiffness of the screen, and further reduce the force acting on the working wire in windy conditions.

In a further embodiment of the invention there is provided a barrier comprising a middle bracing wire adapted to extend between the uprights and to be coupled to the screen at a location intermediate the upper and lower horizontal edges. The use of a middle bracing wire further increases the stiffness of the screen and reduces billowing in windy conditions. As the screen will tend to billow towards its centre, the presence of a bracing wire adjacent the centre of the screen will greatly reduce billowing.

In a further embodiment of the invention there is provided a barrier in which the groundengaging support unit comprises a base section, a hollow trunk section for reception of one of the uprights and an top section, the base section comprising a plurality of guiding blocks for guiding the upright to a correct position within the support unit and the top section comprising a plurality of clamps for aligning the upright and holding it in alignment. In this way, the upright may be positioned within the support unit, correctly aligned and held in position. Consequently, this allows the barrier of the invention to be erected safely and conveniently. -4ln an alternative embodiment of the invention there is provided a barrier in which the base section comprises an annular plate having the plurality of guiding blocks disposed radially thereon, the trunk section comprises a cylinder; and the top section comprises an top section plate having a substantially circular aperture therein, with the clamps being radially disposed about the circular aperture, the circular aperture being axially aligned with the cylinder and the annular plate, thereby forming a receptacle for one of the uprights.

This is a particularly effective arrangement of ground-engaging support unit, the radial arrangement of guiding blocks and clamps being particularly suitable for use with a substantially circular upright. The upright will rest in the base section of the support unit, and extend upwards through the cylinder and the circular aperture in the top section plate where it will engage the clamps.

In one embodiment of the invention there is provided a barrier in which the one or more of clamps are adjustable. In this way, the ground-engaging support unit may be adapted to deal with uprights of different diameters. Furthermore, the vertical alignment of the upright may be adjusted and corrected by adjusting the position of one or more of the clamps.

In another embodiment of the invention there is provided a barrier in which the top section of the support unit forms an enclosure surrounding the clamps. In this way, the clamping mechanism is protected from the elements and interference by unauthorised parties.

In a further embodiment of the invention there is provided a barrier in which the guiding blocks comprise a substantially rectangular block having a chamfered face inclined towards the centre of the annular plate. In this way, the upright will slide along the inclined face towards the centre of the base section, thereby guiding the upright to the correct position at the centre of the base section, between all the guiding blocks. -5ln a further embodiment of the invention there is provided a barrier in which the pulley system comprises a drive means and the barrier further comprises an energy converter mounted on one of the uprights, the energy converter being operable to derive energy from a natural energy source so as to operate the drive means. This is a particularly effective way of providing power to the drive means of the barrier. By having an energy converter, the barrier does not require a connection to mains electricity, thereby making it easier and safer to install. Furthermore, the use of a natural energy source reduces costs and is environmentally friendly.

In an alternative embodiment of the invention there is provided a barrier in which energy converter comprises a solar panel or wind turbine. These are particularly efficient energy converters for use with the barrier of the invention. The energy converters may be connected to a battery so that they may charge the battery for later operation of the drive means or other components of the barrier. Ideally, the energy converters are located adjacent the top of the uprights and positioned so as to facilitate optimum energy conversion, for example the solar panel may be angled so as to catch more sunlight.

In one embodiment of the invention there is provided a barrier comprising a photocell for detecting the onset of darkness, and processing means allowing communication between the photocell and the drive means. In this way, the processing means can be programmed to automatically furl the screen on receipt of a signal from the photocell. In this way the screen can be automatically furled at night and then unfurled again the next morning. This prolongs the life of the screen as it is subjected to less day to day wear.

In another embodiment of the invention there is provided a barrier further comprising a communications module connected to the processing means. In this way, the barrier may receive a signal from a remote user to furl or unfurl. This may be particularly useful, for example, in the case of a storm that would be likely to damage the screen if it was left unfurled. The remote user could send a signal to furl the screen from a communications device such as a mobile telephone or the like.

In a further embodiment of the invention there is provided a barrier in which in the furled position, the screen is retracted inside one of the uprights. This is a particularly efficient way of storing the screen when it is not in use. / 7? -6In an alternative embodiment of the invention there is provided a barrier in which the screen has two side edges and in which, in the unfurled positioned, each side edge of the screen is located inside one of the uprights. In this way, billowing can be further reduced. Furthermore, it ensures that there are no gaps in the protection provided by the screen between the uprights. Additionally, it prevents the edges of the screen from any damage caused by flapping in the wind.

In one embodiment of the invention there is provided a barrier in which the working wire passes through at least one of uprights. In this way, the working wire will engage a pulley that is positioned away from the screen, thereby preventing the screen from fouling on the pulley.

In another embodiment of the invention there is provided a barrier in which the screen comprises one or more of: netting, advertising material or non-transparent sheeting. In this way, the screen may be used to prevent the passage of a ball while still allowing spectators to view the playing are through the netting of the screen. Additionally, the screen may support temporary or permanent advertising material in a sports ground or elsewhere. Finally the barrier of the invention may be used to provide a shield or blinding screen for use in work areas where it may be desirable to shield an area from public view.

Detailed Description of the Invention The invention will now be more clearly understood from the following description of an embodiment thereof given by way of example only with reference to the accompanying drawings in which:Fig. 1 is a diagrammatic representation of the barrier according to the invention; and Fig. 2 is a diagrammatic representation of a ground-engaging support unit according to the invention; -7Fig. 3 is diagrammatic representation of an alternative view of the groundengaging support unit according to the invention; Fig. 4 is a top view of a ground-engaging support unit according to the invention; Fig. 5 is a diagrammatic representation of a guiding block; Fig. 6 is a diagrammatic representation of an alternative embodiment of a guiding block; Fig. 7 is a diagrammatic representation of a fixed piece of a clamp according to the invention; Fig. 8 is a diagrammatic representation of an adjustable piece of a clamp; and Fig. 9 is an exploded view of the adjustable clamp.

Referring to the drawings, and initially to Fig. 1 thereof, there is shown a barrier for preventing the passage of a ball, the barrier being indicated generally by the reference numeral 1, comprising a first upright 102 and a second upright 104 mounted in the ground 105 in a spaced-apart manner. Each upright 102, 104 is mounted in the ground 105 by way of a ground-engaging support unit 106 which is sunk into the ground 105. The second upright 104 is of greater diameter than the first upright 102 and has a longitudinal aperture 107 extending down the side of the second upright 104 that is closest to the first upright 102. The barrier 1 further comprises a substantially rectangular screen 108 which extends between the uprights 102, 104 and is supported by an upper bracing wire 110, a lower bracing wire 112 and a middle bracing wire 114. The upper edge 116 of the screen 108 is coupled to the upper bracing wire 110 by way of connecting rings 118 and the lower edge 120 of the screen 108 is connected to the lower bracing wire 112 by connecting rings 118. When not in use, the screen 108 is stored within the second upright 104, entering by way of the longitudinal aperture 107 in the side its side, in a furled or folded manner. The screen has a fixed side edge (not shown) which is fixed to the inside of the second upright 104, and a leading side edge (not shown). -8The barrier further comprises a pulley system mounted on the uprights, the pulley system comprising a drive pulley 122 mounted on the second upright below the lower edge 120 ofthe screen 108; a first lower pulley 124 mounted on the second upright 104 adjacent the lower edge 120 of the screen 108; a second lower pulley 126 mounted on the first upright 102 adjacent the lower edge 120 of the screen 108; a third lower pulley 128 mounted on the second upright 104 adjacent the bottom ofthe screen 108; a first upper pulley 130 mounted on the second upright 104 adjacent the top edge 116 of the screen 108; a second upper pulley 132 mounted on the first upright adjacent the top edge 116 ofthe screen 108; and a third upper pulley 134 mounted on the second upright 104 adjacent the top edge 116 ofthe screen 108.

A working wire 136 engages the pulley system and travels from the drive pulley 122 up along the second upright 104 to the first lower pulley 124, then through suitable apertures, including the longitudinal aperture 107, in the second upright 104 and across to the first upright 102, along the lower edge 120 of the screen 108 and parallel to the lower bracing wire 112, to the second lower pulley 126 such that this leg of the working wire 136 forms a lower working wire 138, then back to the third lower pulley 128 on the second upright 104 along the lower edge 120 of the screen 108. The working wire 136 travels through suitable apertures (not shown) in the first upright 102 to reach, and return from, the second lower pulley 126, which is mounted on the upright 102 in such a way that it will not interfere with the screen 108, and then returns to the third lower pulley 128 by way of apertures in the second upright 104, including the longitudinal aperture 107. The working wire 136 then travels up the second upright 104 to the first upper pulley 130, through suitable apertures in the second upright 104, including the longitudinal aperture 107, and across to the second upper pulley 132 on the first upright 102, parallel to the upper bracing wire 110 such that this leg forms an upper working wire 140. The working wire 136 travels through suitable apertures (not shown) in the first upright 102 to reach, and return from, the second upper pulley 132, which is mounted on the upright 102 in such a way that it will not interfere with the screen 108, and then returns to the third upper pulley 134 by way of apertures in the second upright 104, including the longitudinal aperture 107. The working wire 136 then travels back to the third upper pulley 134 on the second upright 104 and then finally down the second upright 104 back to the drive pulley 122. The drive pulley 122 is driven with a drive motor, which is -9connected thereto by way of a step-down gear box, the motor and gearbox being shown as a single assembly 142.

The connecting rings 118 at the corners of the screen where leading side edge (not shown) meets the upper edge 116 and lower edge 120 of the screen are coupled to fixed points on the working wire by way of a freely swivelable joint (not shown). In this way, movement of the working wire 135 results in movement of the upper working wire 140 and lower working wire 138 which in turn results in a corresponding movement of the leading side edge (not shown) of the screen, thereby causing the screen 108 to furl or unfurl. The swivelable joint ensures that any twist that occurs in the working wire as it is in motion is not transferred to the screen 108 or bracing wires 110, 112. In the fully extended or unfurled state, the screen 108 extends into a recess (not shown) in the first upright 102 so that the leading edge is enclosed within the first upright 102.

The barrier 1 further comprises a wind turbine 150 for converting wind power into electrical energy, a solar panel 152 for converting sunlight into electrical energy and a photocell 154 for detecting falling light levels, all mounted on the top of the second upright 104. An electrical storage means, in this case a battery (now shown) and associated control circuitry, is housed in a battery housing 156 adjacent the barrier for storing electrical energy generated by the wind turbine 150 and/or the solar panel 152 and for supplying electricity to allow operation of the drive motor 136. A wind speed meter 157 is fitted in the second upright so as to allow the wind conditions to be assessed. A flag pole 158 having a flag 160 fixed thereto is mounted on the first upright 102. The flag pole further comprises a halyard 162 and associated gear (not shown) to allow the flag to be hoisted and lowered as required. Each upright 102, 104 is equipped with a stay wire 164 which is connected to a point adjacent the top of the upright 102, 104 and to a point in the ground 105 so as to provide stability to the uprights 102, 104. Each stay wire 164 has a tensioner 166 to allow the tension in the stay wire 164 to be adjusted as necessary. The barrier 1 finally comprises a control unit 148 for controlling operation of the barrier 1, the control unit 148 comprising processing means (not shown) and optionally, communication means (not shown).

In use, the screen 108 is extendable to and from a furled position inside the second upright 104 and an unfurled position extending between the first upright 102 and the - 10second upright 104. The screen is extendable by operation of the drive pulley such that the working wire and consequently the upper working wire 140 and the lower working wire 138 move in the same direction. Therefore, by turning the drive pulley 122 in a clockwise direction the upper working wire 140 and lower working wire 138 will move from right to left in the drawing, causing the leading side edge of the screen to move from inside the second upright 104 to a position inside the first uptight 102, and thereby causing the screen 108 to unfurl, extending between the first and second uprights. Alternatively, by operating the drive pulley 122 in an anti-clockwise direction, the upper working wire 140 and lower working wire 138 will move from left to right in the drawing, J 0 causing the leading side edge of the screen to move from inside the first uptight 102 to a position inside the second upright 104, and thereby causing the screen 108 to furl.

Power to operate the drive motor attached to the drive pulley will be drawn from the battery which will be charged by the wind turbine, solar panel or alternative supplies for example, mains electricity. If necessary, a winch handle may be attached to the motor and gearbox assembly so as to operate the drive pulley by hand. The furling or unfurling operations can be triggered in a number of ways. Firstly, the control unit will have simple switches to allow an operator to operate the furling or unfurling mechanism. Secondly, the control unit may receive a signal from the photocell or wind speed monitor to indicate that conditions are no longer suitable for the screen to be unfurled. Such conditions include failing light at night time or wind speeds in excess of a preset value, for example 70 kmph. Conversely, the control unit may automatically counteract such a furling signal once the condition triggering the furling has been removed, for example, increasing light levels at dawn or wind speeds that have dropped below a certain value. Additionally, the furling or unfurling mechanism may also be triggered remotely by sending a message to the control unit by way of the communications means.

Ideally, the connecting rings 118 used to connect the screen 108 to the bracing wires 110, 112, 114 comprise snap fit rings so as to facilitate ease and speed of connecting the screen to the bracing wires. The uprights may further comprise one or more computerised display panels, such as LED panels or the like, for displaying information. The information may comprise sporting information such as scores or game time; safety information such as the location of the nearest exit; or advertising information. All pulleys are enclosed within safety casings such that unauthorised personnel cannot access the - 11 pulley workings. Furthermore, the pulleys are vertically oriented so as to ensure that the working wire will always engage the pulleys correctly.

In an alternative embodiment of the barrier, one or more of the uprights do not comprise apertures or recesses for reception of the screen, such that one or both of the side edges of the screen will rest adjacent the relevant upright while in use.

Referring now to Fig. 2, in which like parts have been given the same reference numerals as before, there is shown a ground-engaging support unit 106, comprising a base section 202, a trunk section 204 and a top section indicated generally by the reference numeral 206. The base section 202 comprises an annular plate 208 having a centrally located circular aperture 210 therein. The annular plate 208 mounts eight guiding blocks 212 which are radially disposed about the aperture 210, each guiding block 212 being approximately equidistant from its neighbouring blocks 212. The base section further comprises a covering plate 213 which affixed to the outside of the annular plate 208. The base section 202 is fitted into one end of the trunk section 204, which in this case comprises a cylinder, the diameter of the annular plate being substantially equal to the inner diameter of the cylinder. The top section 206 comprises a cuboid enclosure having a substantially square top section plate 214, four rectangular side walls 216 and a lid 218 (only half of which is shown for clarity reasons). The top section plate 214 mounts eight adjustable clamps 220 which are radially disposed about the edge of a circular aperture 222 in the centre of the top section plate 214. Each adjustable clamp comprises a fixed piece, welded to the top section plate 214 and an adjustable piece which is secured to the fixed piece by a nut and bolt arrangement. The lid 218 comprises a substantially square metal plate having a textured upper surface and circular aperture in the centre of the plate.

Referring now to Fig. 3, in which like parts have been given the same reference numerals as before, there is shown diagrammatic representation of the basic groundengaging support unit 106 assembly before the adjustable pieces of the clamps 220, the lid 218 and the covering plate 213 are included. The fixed pieces 302 of the clamps 220 can be clearly seen in the radial arrangement surrounding the circular aperture 222. - 12Referring now to Fig. 4, in which like parts have been given the same reference numerals as before, there is shown a top view of the support unit 106 illustrated in Fig. 3. The substantially square top section plate 214 is bordered by four rectangular side walls 216 and has a central circular aperture 222. The fixed pieces 302 of the adjustable clamps 220 are mounted on the top section plate 214 in an equi-spaced, radial arrangement about the circular aperture 222 and are aligned with the guiding blocks 212 of the base section below which can be seen through the circular aperture 222.

Referring now to Fig. 5, there is shown a large guiding block 500 comprising a cuboid block having a height h, width w and depth d. One edge of the cuboid has been chamfered, thereby creating a downwardly inclined face 502, such that the guiding block 500 comprises seven faces. The face 502 is inclined at an angle of approximately 30’ to the vertical. The large guiding block 500 comprises a cuboid having one chamfered edge, wherein the height h and width w of the main faces of the cuboid are a number of times larger than the depth d of the cuboid. In this way, the guiding block somewhat resembles a very thick rectangular plate having a single chamfered corner.

Referring now to Fig. 6, in which like parts have been given the same reference numerals as before, there is shown a small guiding block 600, which has the same general shape as the large guiding block 500 but in which the width w is smaller than that of the large guiding block. The height h and depth d are substantially the same in both large and small guiding blocks. The small guiding block 600 comprises a downwardly inclined face 602.

Referring now to Fig. 7, in which like parts have been given the same reference numerals as before, there is shown the fixed piece, indicated generally by the reference numeral 302, of the adjustable clamp 220, for use in the top section 206 of the support unit 106. The fixed piece 302 comprises a cuboid block having one chamfered edge so that the block has one downwardly inclined face 702. The fixed piece 302 further comprises a substantially vertical front face 703. The clamp further comprises a substantially circular bore 704 from the chamfered face 702 to the base of the clamp 302. The central portion 706 of the bore 704 is threaded for engagement with a nut or like fastener (not shown). - 13Referring now to Fig. 8, in which like parts have been given the same reference numerals as before, there is shown the adjustable piece 800 of the adjustable clamp 220, for use in the top section 206 of the support unit 106. The adjustable piece 800 comprises a cuboid block having one chamfered edge so the block has one inwardly inclined face 802, forming a rear face of the adjustable piece 800, which is opposite a substantially vertical front face 806 of the adjustable piece 800. The adjustable piece 800 further comprises a substantially oblong bore 804 extending downwardly from the top of adjustable piece 800 to the inclined face 802.

Referring now to Fig. 9, in which like parts have been given the same reference numerals as before, there is shown an exploded view of the adjustable clamp, indicated generally by the reference numeral 220. In use, the adjustable piece 800 will lie on the fixed piece 302 such that the inclined face 802 of the adjustable piece 800 engages the inclined face 702 of the fixed piece 302, and is slideable thereon. A bolt (not shown) is fitted through the oblong bore 804 of the adjustable piece 800 and into the circular bore 704 of the fixed piece 302, along the line X-X in the drawings. By adjusting the position of the adjustable piece 800 relative to the fixed piece 302, the front face 806 of the adjustable piece 800 will move forwards and backwards, and is secured in place by tightening the bolt when the adjustable piece 800 in the desired location.

In use, a support unit 106 is inserted into the ground 105 without the lid 218, and secured therein. One of the uprights is then inserted into the support unit 106, through the aperture 222 in the top section plate 214 and down into the cylinder of the trunk section 204, until it engages the base section 202 of the support unit 106. The bottom of the upright will be guided to the centre of the base section 202 by the inclined faces 502, 602 on the guiding blocks 212, 500, 600 so that it rests on the base of the support unit 106. The large guiding block 500 or small guiding block 600 will have been chosen depending on the diameter of the upright to be fitted. If the bottom edge (not shown) of the upright alights upon one or more of the inclined faces, it will slide along the inclined faces so that it is guided into the centre of the base section 202. Once the upright is correctly positioned within the support unit, it is clamped in place. The positions of the adjustable pieces 800 of the clamps 220 are adjusted until the front face 806 of each adjustable piece 800 abuts against the side of the uprights and the upright is aligned to - 14the desired angle, generally vertical. This is a substantially easier method of correctly positioning and aligning an upright than mounting such an upright in cement.

The support unit may be secured in the ground by way of setting it in concrete or other 5 securing methods.

In the specification the terms ‘comprise’, ‘comprises’, comprised’ and ‘comprising’ or any variation thereof and the terms ‘include’, ‘includes’, ‘included’ or ‘including’ or any variation thereof are considered to be totally interchangeable and they should ail be afforded the widest possible interpretation.

The invention is not limited to the embodiment herein described, but may be varied in both construction and detail within the terms of the claims.

Claims (5)

1. A barrier (1) for preventing the passage of a ball, the barrier (1) comprising a pair of uprights (102,104) adapted to be mounted spaced-apart from each other; a pulley system adapted to be mounted on the uprights (102,104); a working wire (136) adapted to engage the pulley system so as to form an upper working wire (140) and a lower working wire (138), each extending between the uprights (102,104); a screen (108) having an upper horizontal edge (116) and a lower horizontal edge (120) and adapted to extend between the upper working wire (140) and the lower working wire (138); the pulley system, in use, being operable to move the screen (108) to and from a furled position adjacent one upright (102,104) and an unfurled position extending between the uprights (102,104), characterized in that the barrier (1) further comprises a bracing wire (110, 112), adapted to extend between the uprights (102,104) and to be coupled to one horizontal edge (116,120) of the screen (108).

2. A barrier (1) as claimed in claim 1 further comprising a pair of ground-engaging support units (106) adapted to mount the uprights (102,104).

3. A barrier (1) as claimed in claim 1 or 2 comprising a plurality of bracing wires (110, 112,114) adapted to extend between the uprights (102,104) and to be coupled to the screen (108).

4. A barrier (1) as claimed in any preceding claim in which the ground-engaging support unit (106) comprises a base section (202), a hollow trunk section (204) for reception of one of the uprights (102,104) and an top section (206), the base section (202) comprising a plurality of guiding blocks (212, 500, 600) for guiding the upright (102, 104) to a correct position within the support unit (106) and the top section (206) comprising a plurality of clamps (220) for aligning the upright (102, 104) and holding it in alignment. 7 /7 • 165. A barrier (1) as claimed in claim 4 in which the base section (202) comprises an annular plate (208) having the plurality of guiding blocks (212, 500, 600) disposed radially thereon,

5. The trunk section (204) comprises a cylinder; and the top section (206) comprises an top section plate (214) having a substantially circular aperture (222) therein, with the clamps (220) being radially disposed about the circular aperture (222), the circular aperture (222) being axially aligned with the cylinder (204) and the annular plate (208), thereby forming a receptacle for one of the uprights (102,104).