GB2482580A

GB2482580A - Fall prevention system

Info

Publication number: GB2482580A
Application number: GB1110221.7A
Authority: GB
Inventors: Stuart Arnold
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-06-16
Filing date: 2011-06-16
Publication date: 2012-02-08
Also published as: GB201110221D0; WO2011158035A1; GB201010053D0

Abstract

The system for guarding at least one side of a platform, e.g. of a machine or vehicle, has a stowed state and a deployed state and comprises a first member and a second member, e.g. posts 5, an elongate flexible element, e.g. a rope 9, and a tensioner for tensioning the said elongate flexible element. Tensioning is by rotation and/or translational movement apart of the posts 5. The posts 5 carry retainers 7 for a vertical array of ropes 9, the retainers being movable between upper, in use, locations and lower, stowed, locations where the ropes are below the platform. The ropes 9 can support a flexible sheet.

Description

FALL PREVENTION SYSTEM

Field of the Invention

The present invention relates to a fall prevention system, in particular to a fall prevention system for vehicles such as commercial vehicles.

Background of the Invention

Vehicles are used to transport goods from place to place. The load carrying platforms of commercial vehicles in particular are positioned at such a height that if an operator working on the platform were to fall off, he may well be injured, perhaps seriously. It has therefore been identified that vehicles should either be able to be loaded and unloaded without an operator being required to climb onto the load carrying platforms of such vehicles, or operators should be able to walk on and off the platform from/to a surface lying at substantially the same level as the load carrying platform. Where it is economic and practical to do so, this is what happens. For example, curtain sided vehicles are generally loaded in palletised form, from the ground, using forklift trucks. Flatbed trucks are often loaded at factories in loading bays, the surfaces of which lie substantially at the same level as that of the flat bed of the truck.

However, there are circumstances where it is not practical to load and unload goods in a palletised form or to provide a loading bay. Elongate objects, such as pipes are a good example.

As a rule they are often too large in both dimension and weight to be palletised, and hence are typically loaded onto a vehicle where they are held in place by upstanding posts by means of a crane which may lift the pipes over the top of the posts (or alternatively the posts may be removed during loading).

In such a scenario, an operator would usually climb onto the working platform of the vehicle to position the pipes as they are lowered by the crane. Working in such conditions presents a danger to the operator. He may lose his footing, or be pushed by a swinging pipe that he is attempting to control, or simply mis-judge his position with respect to the edge of the trailer, any of which could result in a fall.

It is often the case that goods are delivered to locations where the construction of docking bays for loading/unloading is simply not economically feasible.

It is evident that operators will continue to need to work at height, i.e. on the working platform. Hence, there is a need for a fall prevention system.

Attempts have been made to provide vehicles with fall prevention systems. Once such system comprises a set of inflatable mattresses deployed around the vehicle, their purpose being to cushion the fall of an operator from the vehicle. These systems are time consuming to deploy and put away and do not actually prevent a fall. The operator may still be injured in the event of a fall.

Another system comprises portable staging which is brought to a site to provide a temporary docking facility so that the operator may walk on and off the vehicle at a substantially similar level. However, such portable staging must be brought to a site, occupies space at the site, and adds to the logistical demands presented by the transportation of goods, and in many cases cannot be justified economically unless a significant number of deliveries are to be made.

Another system comprises a lanyard attached at one end to the vehicle and the other to the operator. Typically, the lanyard is attached to an inertia reel so that the operator may move about, drawing the lanyard off the reel, but if he were to begin to fall the increase in acceleration would cause the inertia reel to prevent the further release of the lanyard. Whilst such a system offers an operator a level of protection from falling, it would not prevent falls in all circumstances. This will depend on the operator's position on the vehicle relative to the attachment point of the inertia reel to the vehicle. On curtain sided vehicles a mono-rail is provided along each edge of the vehicle to overcome the afore-mentioned problem, but this would not work with a flatbed trailer.

I

Another system for preventing falls involves attaching balustrade to the sides of the vehicle, so that if an operator on the vehicle were to fall, he would be caught by the balustrade and prevented from falling.

One system which claims to overcome the problems associated with the aforementioned systems is described in the patent application published under number WO 2008/117065. This patent application describes a combination of a load bed and a platform for a trailer. The platform is moveable between stowed and deployed positions. In the stowed position the platform is situated beneath the trailer bed, and in the deployed position the platform extends alongside the trailer bed, thereby providing a walk way. A balustrade is provided along the outside edge of the platform.

Whilst the system described in W02008/117065 maybe regarded as an advance on the prior art, it does present its own problems. First, it is heavy. Commercial vehicles have a maximum laden weight. Every additional unit of weight taken up by the vehicle is a unit of weight that cannot be added as payload. Since haulage operators tend to charge for their services according to the weight of goods that they carry, reducing the carrying capacity of a vehicle would make using such a vehicle undesirable. Also, commercial vehicles work in harsh environments where they are often hit either by the payload that is being loaded or unloaded or by the vehicle that is doing loading or unloading, or simply by the driver of the vehicle mis-judging the position of an object and crashing into it, or forgetting that the platform is in the deployed condition and therefore hitting an object that had been missed when the platform was stowed. In the event that the platform is damaged when deployed it may not be possible to return the platform to its stowed position. The likely result of this is that the vehicle would not be able to travel on the public highway because it would be over the width permitted by law. A fitter would have to be sent to repair the system.

Whilst commercial vehicles present a risk of falling from a height, there are other situations also presenting a risk of falling from height. For example some large machine tools have a bed that is raised above the ground, and which workers must gain access to. Also, certain categories of plant include a platform which workers must gain access to and which is raised a significant height above ground level.

Another system involves equipping a platform with posts and extending an elongate element such as a wire rope about those posts. The wire rope is typically attached to a winch which allows the rope to be tightened or made slack so that it may be withdrawn from the posts on to the winch for loading of the vehicle. Whilst this system functions well on large vehicles, which deliver large loads with significant unloading times, on smaller vehicles shorter unloading times are required.

It would therefore be desirable to provide a fall prevention system, the features of which provide for rapid deployment. Such a system would have application in the field of vehicles and other areas where raised platforms are used and access to the platform is needed.

Summary of the Invention

According to a first aspect of the invention there is provided a fall prevention system comprising a first member and a second member, an elongate flexible element and at least one tensioner for tensioning the said elongate flexible element, wherein the said element extends between the first and second members, and wherein at least one of the first and second members provides an elongate flexible element support, said element engaging the support.

Advantageously, the elongate flexible element support is a retainer. Preferably, the retainer retains an end of the elongate flexible element. The retainer may be in the form of a collar which may include a cam surface.

Advantageously, the tensioner is formed by at least one of the first and second members such that it is moveable between a first position in which the elongate flexible element is slack and a second position where the elongate flexible element is tight.

A drive means may be provided to move the member between the first and second positions, which may be provided with a tool receiving part in order that an operator may with the aid of a tool, move the said member between the first and second positions.

At least one of the first and second members may be mounted so as to rotate about its own axis between the said first and second positions. The drive means may comprise a worm gear drive mechanism.

At least one of the first and second members may be mounted so as to translate with respect to the other member. The drive means may comprise rack and pinion mechanism.

The first and/or second members may be configured as posts.

Advantageously the elongate flexible element is attached to retainers, at least some which are slidably mounted on the first and second members. Preferably, a locking means is provided for each retainer in order that the retainer may be secured in a selected position. This provides the advantage that the retainer may be locked in a selected position, such as a position where the elongate flexible element serves to prevent a person or object falling from a surface, and when unlocked allows the retainer to slide to a position where the elongate element is stowed, allowing free access to the surface.

In one embodiment at least one of the first and second members are non-circular in cross-section, for example square or rectangular, and the retainer includes an opening having a shape corresponding in cross-section to the cross-sectional shape of the first and second members. The non-circular cross-sectional shape of the first and or second member and corresponding cross-sectional shape of the retainer ensures that the retainer may slide up and down the said first or second member in only one axis, but that when the said first or second member is rotate, the retainer will rotate therewith.

In one embodiment at least one of the first and second members includes an indent or track and the retainer includes a protrusion configured to extend into the indent or track. The protrusion may include at least a part of the locking means which secures the retainer in a selected position. The protrusion may be in the form of a pin, which may include a biasing means, such as a spring, configured to bias a part of the pin into a locking position, and a release means adapted to release pressure on the said part of the pin to facilitate release from the locking position. The locking means may include a pin receiving opening in the first or second member.

The elongate flexible element may be attached to the retainer by attachment to the pin.

The protrusion may comprise a ball, such as a ball beating, mounted in a cylinder and biased to protrude from one end of the cylinder by a biasing means such as a spring, the biasing means preferably being mounted in the cylinder.

In another embodiment, the first and second members each include a protruding element and the retainer is configured to receive the protruding element. Hence, the retainers may slide on the first and second members but only in the direction permitted by the co-operating protruding element and so configured retainer. Advantageously, a locking means is provided to lock the retainer in a selected position on the first or second members.

A support member may be provided between the first and second members, the support being adapted to support the elongate flexible element when align therewith. The support member may comprise a post. The support member may comprise a pulley, which may be mounted on the post. The support member may comprise a hook and the hook may include a channel adapted to receive and support the elongate flexible element. The hook may include a recess for receiving and supporting the elongate flexible element when the said element is taut.

In one embodiment of the invention, a length of a flexible element, such as fabric is attached to at least upper and lower elongate flexible elements, and preferably to each of the elongate flexible elements. In such an embodiment, it may be preferable that the lower most retainers are not arranged to slide with respect to the first and/or second members.

Where the fall prevention system is provided on a vehicle, head and tail boards may also be provided. The head and tail boards may be formed of solid elements, such as steel bars.

Advantageously, the fall prevention system may have a deployed state and a stowed state and be moveable between the two said states.

According to another aspect of the invention there is provided a fall prevention system of the first aspect of the invention further including a mechanism for moving the elongate flexible elements between their deployed and stowed states.

Advantageously, the mechanism includes at least one actuator and at least one flexible element, such as a wire, each associated with a respective first and/or second member, the flexible element engaging with the actuator or a component moveable by the actuator, and the flexible element attached to each of the elongate flexible element retainers.

The mechanism may include two flexible elements, both engaging with one actuator or a component moveable by the actuator and both flexible elements attached to each of the elongate flexible element retainers.

The at least one actuator may be arranged in a substantially hollow post, and one end of the flexible element may be attached to the post forming part of the first or second member, or to the actuator.

The flexible element may engage with a pulley wheel mounted on the actuator.

The respective first or second member may mount a flexible element support, which may comprise a pulley wheel, the flexible element extending over the said flexible element support.

Preferably, the flexiMe element includes attachment elements for securing the flexible element to at least those retainers that are slidably mounted on the first and second members.

The attachment elements may include ferrules or clamps attached to the flexible element and configured to engage with retainers.

The retainers may include a flexible element receiving means, which may comprise a slot.

The actuator is preferably a linear actuator and may be pneumatic, hydraulic or electric.

In some embodiments the actuator may include a winch, the flexible element winding on and off the winch to move the retainers to which the flexible element is attached.

The fall prevention system may include a supply of pressurised fluid, such as air or hydraulic fluid, depending on the requirements of the actuator.

In one particular embodiment where the fall prevention system forms part of a vehicle and it is desirable that the elongate flexible element should not be above the load carrying surface when stowed the first and second members may be so located with respect to the surface to be protected that the retainers may slide to a position where the uppermost retainer and elongate flexible element attached thereto are situated below level of the surface to be protected.

According to another aspect of the invention there is provided a machine having a platform equipped with a fall prevention system as described above. The machine may be a vehicle.

The fall prevention system of the invention is particularly advantageous because it may be switched between its stowed and deployed states very easily and quickly, and furthermore this may be done by the operator simply moving the first and/or second memebers to slacken off the elongate elements, and then sliding the retainers down the first and/or second members after releasing any locking means. As can be seen from the drawings, this can be done from ground level. Still further, much of the system can either withstand minor knocks or easily be replaced in the event of such a knock.

Where the fall prevention system include a mechanism for moving the retainers with respect to the first and/or second members moving the system between the stowed and deployed states is even easier.

In the embodiment where flexible material is attached to at least some of the elongate flexible elements, this can prevent items falling from the surface being protected. For example, tools may not be kicked off risking bystanders. Further the flexible material may carry advertising, which is desirable in many circumstances.

Still further, any posts arranged to support the elongate flexible element between the first and second members may be removed quickly and easily from the ground to facilitate loading and unloading.

The fall prevention system may be used to protect an edge of any length or any width.

All that is required is for supports (typically pulley wheels) to be suitably positioned and the elongate flexible element to be of sufficient length.

Brief Description of the Drawings

In the drawings, which illustrate preferred embodiments of the invention, and are by way

of example:

Figure 1 is a schematic representation of a fall prevention system according to one aspect of the invention mounted on a vehicle according to another aspect of the invention; Figure 2 is a schematic representation of a rotatable upright element of the fall prevention system according to the invention; Figure 3a and 3b illustrate components of a fall prevention system according to the invention; Figure 4 is an illustration of a centre post of a fall prevention system according to the invention; Figure 5 is another illustration of a vehicle according to the invention; Figure 6 is side view of an embodiment of a fall prevention system according to another aspect of the invention; Figure 7 is a detail view of the embodiment illustrated in Figure 6; Figure 8 illustrates component parts of the fall prevention system illustrated in Figures 6 and 7; Figure 9 illustrates component parts of the fall prevention system illustrated in Figure 6 and 7; Figure 10 illustrates further component parts of the fall prevention system illustrated in Figures 6 and 7; Figure 11 illustrates further component parts of the fall prevention system illustrated in Figures 6 and 7; Figure 12 illustrates another component part of the fall prevention system illustrated in Figures 6 and 7; Figure 13 illustrates a collar of the fall prevention system illustrated in Figures 6 and 7; Figure 14 illustrates a bracket for attachment to the collar illustrated in Figure 13; Figure 15 illustrates the assembled bracket of Figure 14 and collar of Figure 13; and Figure 16 illustrates the part of a wire that carries the collars of the fall prevention system of Figures 6 and 7.

Detailed Description of the Preferred Embodiments

Referring now to Figure 1, there is shown a vehicle in the form of a flat bed truck 1.

Alternatively, the vehicle could be a trailer, which in use would be towed by a tractor unit. The flat bed I comprises a platform 2 upon which goods are loaded, the platform 2 having edge members 3, 3'. The edge members may be formed from steel channel section. Brackets 4 are attached to edge members 3, 3' by bolts, welding or other suitable fasteners. Attached to each bracket 4 are upright posts 5 which are mounted upon a drive gear mechanism 6. The drive gear includes a worm gear (not shown) and a spur gear 6a that intermeshes with the worm gear. The worm gear is drivable and may have a drive member attached thereto so that a tool may engage with the drive member and rotate the worm gear. Alternatively, a motor may be attached to the worm gear so that rotation of the motor causes the worm gear and hence the spur gear 6a to rotate.

In an alternative, the drive gear mechanism may be a rack and pinion arrangement rather than a worm gear intermeshing with a spur gear. With such an arrangement, each of the posts 5 could be attached to the rack of the rack and pinion, and be arranged to follow a translational movement with respect to the bracket 4. In the embodiment illustrated in Figure 1, this would lead to the post 5 proximate the cab of the truck being moved to the right and the post 5 to the rear of the truck being moved to the left to tighten the wire ropes 9, and in the opposite directions to slacken off the wire ropes 9. Of course, with a rack and pinion arrangement if the post is attached to the pinion, it may be rotated by translational movement of the rack.

Whether the posts 5 rotate, translate or move in another manner, an embodiment may be envisaged in which only one post 5 on each side is movable, the other being fixed. Whether there is a requirement for the posts at both ends to rotate depends on a number of factors, such as: cost, desired ease of use, the length of rope that is to be taken up, etc. The upright post 5 is mounted on the drive mechanism and is attached to the spur gear 6 so that rotation of the spur gear causes the post 5 to rotate about its own axis. As can be seen from Figures 1 and 2, a plurality of collars 7 are mounted on the post 5. Each post includes an indent in the form of a slot 8 extending radially into the post 5, and axially therealong. Each collar is provided with a protruding element so shaped and dimension as to protrude into the slot 8. Hence, the collars 7 rotate with the post rather than with respect to the post.

As can be seen from Figure 1, a platform 2 is provided with a post 5 mounted on a drive gear mechanism 6 at each end of the platform. Only one side of the truck is illustrated in Figure 1, but the vehicle would typically be provided with four posts 5 one at each corner of the platform 2. Elongate elements in the form of wire ropes 9 extend between the posts 8, respective ends of the wire ropes 9 being attached to collars 7. The ropes 9 are made tighter or slacker by inserting a tool into the worm gear drive member 6b and turning the worm gear in the appropriate direction.

In Figure 1, the wire ropes 9 are in the raised position but slackened off. The ropes 9 need to be tightened in order to fully deploy the fall prevention system. When the platform is to be loaded or unloaded from the side, and it is necessary to gain access to a particular side of the platform 2, the wire ropes 9 may be moved into a second position in which access to the platform from the side, at platform height is permitted.

The slot 8 ensures that the collars 7 rotate with the post 5. However, they also provide for movement of the collars 7 with respect to the post 5 in the vertical plane, that is the collars 7 may slide up and down on the posts 5.

Each collar 7 is provided with a pin which is biased into a first position where it engages with the post 5, and the post 5 may be provided with holes into which the pin extends. The pin may be pulled away from the post so that it disengages from the post 5, or the hole in the post 5.

With the pin disengaged the collars may slide relative to the posts 5 between a raised position as illustrated in Figure 1 and a lowered position where the wire ropes 9 are lowered and preferably the uppermost rope 9 is situated below the top of the side rave 3 and hence the surface of platform 2.

Referring now to Figures 3a and 3b, the collars 7 are provided with lips 7a, 7b which ensure that the rope 9 winds on to the collar without falling off the collar. The collar 7 is provided with a suitable fitting to allow the wire 9 to be secured thereto. In order to allow the collars 7 to move up and down with respect to the posts 5, yet be held in the deployed position yet be moved to the stowed position, the collars 7 are provided with pins 7c which include a spring 7f a ball bearing 7d and a ball bearing housing 7e. The spring 7f pushes the ball bearing 7d to the end of the housing 7e and in this position the ball bearing will extend into a hole in the slot 8, when aligned with such a hole. To allow the collar 7 to move with respect to the post 5, the pin 7c to which the spring 7f is attached is pulled away from the post 5, which releases the force on the ball bearing 7d and allows the collar 7 to move with respect to the post. As soon as the ball bearing 7d has released from the hole, the pin 7c may be released, since the spring 7f then only presses the ball bearing 7d against the surface of the slot and hence the collar may still slide with respect to the post 5.

Referring now to Figure 4, depending on the distance between the posts 5, it may be necessary to include an intermediate support for the wires 9. Such an intermediate support may comprise a post 10 sitting in a bracket 11 formed in the side rave 3 of the truck. The post 10 mounts a support in the form of a pulley 13 which is attached to the post 10 by a bracket 12.

Referring now to Figure 5, the truck illustrated shows how the ropes 9 are attached to the collars 7, and how the ropes 9 are supported by the intermediate post 10. Regarding the attachment of the ropes 9 to the collars 7, as can be seen from the Figure, the end of the rope 9 passes through a hole in the pin 7c. A grub screw is situated in the pin 7c which may be turned by an Allen key to fasten the rope to or release the rope from the collar.

The posts 5 and 10 may be removable from the brackets on which they are mounted, for example, a pin may be provided extending through the post and a part attached to the bracket, which when removed allows the post to be lifted from the bracket.

The posts 5 and collars 7 are described above with reference with the post being provided with an indent and the collar with a protrusion for engaging with the indent, Of course, this could be reversed with the post being provided with the protrusion and the collar the indent. In such an arrangement the protrusion on the post could be provided with a releasable fastening means, such as one or more spring biased ball bearings, that engage with indents in the collar, and that are disengaged from the indents upon release of the fastening means.

Figures 6 to 15 illustrate an alternative embodiment of the fall prevention system of the invention. The system is described as being semi-automatic because it can be raised automatically. In the embodiment illustrated in Figure 6 to 15, lowering is achieved manually.

Further, the embodiment illustrated in Figure 6 supports a length of flexible material 120, which is supported on the wires 90. In this embodiment, only the two upper collars are configured to be moved upward and downward, since it is preferred that the bottom edge of the flexible material be fixed in position along the side rave 130 of the surface being protected.

Referring first to Figures 6 and 7, there is shown a side view of a fall prevention system.

The fall prevention system comprises two spaced apart end posts 50, each mounting three collars 51 slidably thereon. The end posts 50 are square in cross-section, which provides for driving the collars 70 rotationally about the axis of the posts 50 and for sliding of the collars 70 with respect to the posts 50. Between the end posts 50 there are located intermediate posts 100, each of which mounts a plurality of hooks 110. A wire 90 is attached to a pair of collars, one mounted on each of the posts 100. Each wire 90 is provided with a tensioning element, which in the illustrated example is a turnbuckle 91. The turnbuckle 91 allows each of the wires 90 to be brought to substantially the same tension with the same amount of wire wound on to each collar 70.

The hooks 110 are illustrated in greater detail in Figure 12, each hook comprising a channel 111 and a recess 112 extending off the channel. Each hook 110 further comprises a bore 113 so shaped and dimensioned as to receive a bolt and bolt head in order that the hook may be fastened to an intermediate post 100. The hooks 110 are attached to the posts 100 such that the channel is oriented with its longitudinal axis substantially vertical and the recess 112 situated below the opening of the channel 111. In this way, a wire 90 may be introduced to the hook from above the hook, and be supported by the hook in the recess 112 when the wire 90 is pulled taut.

It can be seen that the lower most wire 90 is held in place by two hooks 110 on each intermediate post 100, the hooks 110 having their channelslll lying parallel to one another but turned through 180 degrees, such that one channel 111 is open from above and the other open from below. Hence, the lower most wire 90 is fixed in position, which when a flexible material is attached to the wires 90 provides a barrier against objects falling from the edge of the surface being protected.

The intermediate posts 100 are preferably demountable, for example in the manner described with reference to Figure 4.

The posts 50 are mounted such that they may rotate about their own axes and are driven by a drive gear mechanism of the type described with reference to Figure 1. The posts 50 are rotatably mounted at their upper ends in brackets 52.

The posts 50 include a lifting mechanism arranged to pick up the collars 70 from their stowed state (left hand elevation of Figure 6) and raise them to the deployed state as shown in the main elevation of Figure 6.

The lifting mechanism will now be described with reference to Figures 8 to 11. The lifting mechanism comprises a piston 55 which mounts a pulley 56 on the end thereof. The piston 55 is mounted in a post member 57, which in the illustrated example is a piece of box section steel. The post member 57 mounts a bracket 58.

Referring specifically to Figure 9, the most right hand elevation the post 50 and collars are illustrated such that the collars 70 are illustrated in both their deployed and stowed states.

In the deployed state the piston 55 is extended with the pulley 56 proximate the base of the post member 57. In the deployed state the collars 70 are spaced apart along the most member 57 and the wire 60 is taut. The wire 60 engages with the collar 70 through slot 77 thereof and by means of ferrules 61 which engage with the flanges 75 of the collar 70. Hence, when the wire 60 is raised the collars 70 are lifted on the post member 57. The wire 60 is illustrated in greater detail in Figure 16. In addition to the wire 60 being held in the slot 77 by the ferrules, the wire 60 may be prevented from escaping from slot 77 by wire 90 passing around the collar 70.

The collar 70 may be made of metal, such as steel, for example stainless steel, or another suitable material, such as a hard plastics material.

Figure 9 also illustrates the collars 70 in their stowed state, that being with all three collars 70 situated at the base of the post member 57. However, in the stowed state the condition of the wire 60 is not shown.

The embodiment illustrated in Figure 9 is one in which all three collars are raised and lowered. Where only the upper two collars are raised and lowered, as in the embodiment illustrated in Figure 6, the wire need only attach to those collars to be moved.

Referring to the left hand elevation of Figure 9, one end of the wire 60 is attached to the a fixed point, such as the post member or a bracket attached thereto, for example just above the pulley 56 in its raised position. The end of the wire could be attached to the end of the piston 55 mounting the pulley 56 or the bracket mounting the pulley 56.

The wire 60 extends upward and over the bracket 58 of the post member 57, exiting the post member 57 through slot 59. When the collars 70 are to be raised, air is introduced into the piston 55 thereby extending it, and moving the pulley 56 to the base of the post member 57. The wire 60 is of a fixed length and hence as the pulley 56 is moved downward in the post member, so the wire 60 is pulled taut. Since the collars 70 are attached to the wire 60, movement of the wire 60 results in those collars being raised to the deployed state.

The left hand elevation of Figure 9 illustrates an embodiment including two wires 60, each provided with its own bracket 58, the actuator 55 in this case being provided with two pulleys 56 preferably on a common axis, the pulleys horizontally spaced apart thereon. For the sake of clarity, the two wires 60 to the upper part of the elevation are shown spaced apart laterally. However, this is not necessary. The wires 60 could lie in the same plane, but would be spaced apart horizontally, as would brackets 58. All that is required is that the wires 60 do not interfere with each other. The provision of twin wires 60 is less likely to exert a force on the collar 70 that is likely to twist the collar with respect to the post, which force would resist movement of the collar up and down with respect to the post.

Whilst the piston 55 is described as being pneumatically actuated, any linear actuator could be used with the arrangement shown in the drawings. For example, a hydraulic or electrically actuated piston could be used. Also, in some applications, an on-linear actuator may also be used. For example a post member 57 may be of a dimension that is suitable to receive a small barrel winch, the rope 60 being mounted on the barrel of the winch.

Figure 10 illustrates the mounting of the post member 57 at its lower end, the post member 57 including a cylindrical portion 57' having upper and lower flanges 57" which prevent vertical movement of the post member 57 but allow for rotation thereof.

The collar 70 is illustrated in detail in Figures 13 to 15 and comprises an opening 71 having the same cross-sectional shape as the post 50, that being square in the present example.

The opening 71 is of a slightly larger dimension than the external dimension of the post, thereby allowing the collar 70 to slide on the post 50.

The collar 70 includes a channel 73, which in the illustrated example is substantially circular in cross-section, and is provided with an elongate opening 74. A wire 90 is inserted into the channel 73 through the elongate opening 74. Such a wire is provided with a means to engage with the end of the channel 73. For example, a knot may be formed in the wire or a ferrule attached thereto. The collar 70 is provided with flanges 75 which confine the wire to the collar as the collar is rotated. Also provided in the flanges 75 are holes 76. A pin may be passed through the holes 76 to assist in retention of the wire on the collar.

The collar 70 further includes a bore 72 which is configured to receive a sprung loaded ball bearing, as illustrated in Figure 15. A bracket 80 includes a bore 82 in which a ball bearing 83 and a compression spring 84 are mounted. The bracket 80 is secured to the collar 70 by suitable fasteners engaging with the bores 79 and 85 of the collar 70 and bracket 80 respectively. The dimensions of the bracket 80 are such that the ball 83 aligns with the bore 72 of the collar 70, a part of the ball 83 protruding through the bore 72 beyond the inner surface of the opening 71 of the collar 70. The purpose of the ball 83 is to engage with an indent 51 in the post 50 upon which the collar is mounted, and thereby retain the collar 70 at a certain vertical position on the post. The spring 84, ball 83 and indents 51 are so dimensioned and specified that the force exerted by the spring 84 may be overcome by manually pressing down on or lifting up the collar 70.

The bracket 80 includes a bore 81, and the end of the wire 90 may be mounted in this bore 81. With the bracket 80 attached to the collar 70 the wire 90 is aligned with the channel 73.

Operation of the embodiment of the invention illustrated in Figure 6 to 16 will now be described.

Starting in the deployed state, the posts 50 are rotated using the drive gear 6, thereby slackening off the wire 90. The operator then lifts the wires 90 out of the hooks 110. The next step is depressurising the air in the cylinders 55. This allows the collars 70 to be pushed or pulled downward, overcoming the force of springs 84. The collars 70 may be pushed or pulled downward by the operator's own hands or by means of a tool. If any wire 90 should happen to engage with a hook 110 in its downward path, the operator simply lifts the wire over the hook.

The intermediate posts 100 may then be removed to allow unencumbered access to the horizontal surface that is protected by the fall prevention system. Of course it is possible that the posts 100 may be removed after the step of releasing the wires from the hooks 110.

The system is then in its stowed state. In this state, the wires 90 may be left slack, or the posts may be rotated to bring the wires back taut.

From the stowed state, if the wires 90 are slack, the piston 55 is extended by introducing pressurised air. This lifts the collars 70 to the deployed state, the collars being positioned on the wire 60 such that when the piston 55 is extended the ball bearings 83 engage with indents 51.

The intermediate posts 100 may be remounted at this point in the procedure, or whilst the wires are still in their stowed state. With the intermediate posts 100 remounted, the wires 90 are introduced into the hooks 110. The posts 50 are then rotated to bring the wires 90 taut and the system back to its deployed state.

In the embodiment where a length of flexible material is supported on the wires 90, that flexible material is substantially taut when the system is in its deployed state, and in the stowed state the flexible material tends to fold about the longitudinal axis of the wires 90.

Claims

Claims 1. A fall prevention system comprising a first member and a second member, an elongate flexible element and at least one tensioner for tensioning the said elongate flexible element, wherein the said element extends between the first and second members, and wherein at least one of the first and second members provides an elongate flexible element retainer, said element engaging the retainer.
2. A fall prevention system according to Claim 1, wherein the tensioner is formed by at least one of the first and second members such that said member is moveable between a first position in which the elongate flexible element is slack and a second position where the elongate flexible element is tight.
3. A fall prevention system according to Claim I or 2, wherein drive means is provided to move the member between the first and second positions.
4. A fall prevention system according to Claim 3, wherein the drive means includes a tool receiving part, actuation of a tool in said tool receiving part moving the said member between the first and second positions.
5. A fall prevention system according to Claim 3 or 4, the drive means including a worm gear drive mechanism and/or a rack and pinion mechanism.
6. A fall prevention system according to any preceding claim, wherein at least one of the first and second members is mounted so as to rotate about its own axis between the said first and second positions.
7. A fall prevention system according to any preceding claim, wherein at least one of the first and second members is mounted so as to translate with respect to the other member.
8. A fall prevention system according to any preceding claim, wherein the first and/or second members include a post.
9. A fall prevention system according to any preceding claim, wherein at least some of the retainers are slidably mounted on the first and second members.
10. A fall prevention system according to any preceding claim, further including a locking means is provided for each retainer and configured to secure a retainer in a selected position.
11. A fall prevention system according to any preceding claim, wherein at least one of the first and second members is non-circular in cross-section and the retainer(s) mounted thereon include(s) an opening having a shape corresponding in cross-section to the cross-sectional shape of the at least one of the first and second members.
12. A fall prevention system according to any preceding claim, wherein at least one of the first and second members include an indent or track and the retainer includes a protrusion configured to extend into the indent or track.
13. A fall prevention system according to Claim 12, wherein the protrusion forms at least a part of the locking means which secures the retainer in a selected position.
14. A fall prevention system according to Claim 12 or 13, wherein the protrusion includes a pin and/or a ball.
15. A fall prevention system according to Claim 14, further including a biasing means configured to bias a part of the pin and/or ball into a locking position.
16. A fall prevention system according to any preceding claim, wherein the first and second members each include a protruding element and the retainer is configured to receive the protruding element.
17. A fall prevention system according to any preceding claim, wherein at least one support member is provided between the first and second members, the support being adapted to support the elongate flexible element when align therewith.
18. A fall prevention system according to Claim 17, wherein the support member comprises a post.
19. A fall prevention system according to Claim 17 or 18, wherein the support member comprises a pulley or a hook.
20. A fall prevention system according to Claim 19, wherein the hook includes a channel adapted to receive and support the elongate flexible element.
21. A fall prevention system according to Claim 19 or 20, wherein the hook includes a recess for receiving and supporting the elongate flexible element.
22. A fall prevention system according to any preceding claim, wherein a length of a flexible material is attached to at least upper and lower elongate flexible elements.
23. A fall prevention system according to any preceding claim, the fall prevention system having a deployed state and a stowed state and being moveable between the two said states.
24. A fall prevention system according to any preceding claim, and further including a mechanism for moving the elongate flexible elements between their deployed and stowed states.
25. A fall prevention system according to Claim 24, wherein the mechanism includes at least one actuator and at least one flexible element each associated with a respective first and/or second member, the flexible element engaging with the actuator or a component moveable by the actuator, and the flexible element attached to each of the movable elongate flexible element retainers.
26. A fall prevention system according to Claim 24, wherein the mechanism includes two flexible elements, both engaging with one actuator or a component moveable by the actuator and both flexible elements attached to each of the movable elongate flexible element retainers.
27. A fall prevention system according to any of Claims 24 to 26, wherein the at least one actuator is arranged in a substantially hollow post.
28. A fall prevention system according to Claim 27, wherein one end of the flexible element is attached to a component such that the position of the said one end is fixed with respect to the post forming part of the first or second member, or to the actuator.
29. A fall prevention system according to any of Claims 24 to 28, wherein the flexible element engages with a pulley wheel mounted on the actuator.
30. A fall prevention system according to any of Claims 24 to 29, wherein the respective first or second members mount at least one flexible element support, the at least one flexible element extending over the at least one flexible element support.
31. A fall prevention system according to any of Claims 24 to 30, wherein the flexible element includes attachment elements for securing the flexible element to at least those retainers that are slidably mounted on the first and second members.
32. A fall prevention system according to Claim 31, wherein the attachment elements include ferrules or clamps attached to the flexible element and configured to engage with retainers.
33. A fall prevention system according to Claim 32, wherein the retainers include a flexible element receiving means in the form of a slot.
34. A fall prevention system according to any of Claims 24 to 33, wherein the actuator is a linear actuator or a rotary actuator.
35. A fall prevention system according to any of Claims 24 to 34, wherein the actuator is pneumatic, hydraulic or electric.
36. A fall prevention system according to any of Claims 24 to 35, including a supply of pressurised fluid.
37. A vehicle including a fall prevention system according to any preceding claim, wherein the system is configured such that in the stowed configuration the retainers slide to a position where the uppermost retainer and elongate flexible element attached thereto are situated below level of the surface to be protected.
38. A machine having a platform equipped with a fall prevention system according to any preceding claim.
39. A machine according to Claim 38, wherein the machine is a vehicle.
40. A fall prevention system substantially as shown in, and as described with reference to, the drawings.