AU2014224104B2 - Construction Site Safety Screen System - Google Patents

Abstract

A construction site safety screen system comprising a plurality of vertical rails deployed across the face of a structure; safety screens, scaffoldings. or the like fixed to said rails; support beams fixed to 5 the outer zone of each concrete slab of a structure with their ends extending beyond the edge of each said slab; releasable means at the outer end of said support beams to engage said rails to retain them parallel to the outer face of said structure but allow their upward or downward sliding displacement; supporting tongues 10 pivotally supported towards the outer ends of said support beams to support the weight of said rails; sliding latch elements to lock said tongues in their engaged positions; jacking means pivotally supported from said support beams, the upper ends of which incorporate supporting means to slidingly engage with said rails, 15 and means to engage said rails to raise or lower them. Sheet 1 of 5 so .57 -4 t Fig 4 44 s-4, 3,51 f3 3 Fig 3

Description

CONSTRUCTION SITE SAFETY SCREEN SYSTEM

This invention relates generally to the provision of safety screens in elevated construction situations. More specifically, it relates to the installation of such screens and their supporting structures on multi-storied building sites by a jacking process commenced at ground level.

In the field of multi-level building construction, it is a legal requirement in many jurisdictions for safety screens to be erected over open areas of elevated building floors until such areas are enclosed by the installation of curtain walls and the like. Screens ensure the safety of personnel and prevent the falling of tools, equipment and materials which might cause injury to persons and property below. In their simplest embodiment, safety screens take the form of suitable frames covered with a wire mesh, polymer tapes welded to create a strong web, or the like. The frames are hoisted into place following stripping of formwork from concrete floor slabs and are fixed to the edges of the slabs, remaining in place until curtain walls or the like are installed. The strength of the fixing method is an important consideration, given the large screen areas and the fact that wind forces in elevated situations may be significant.

In the construction field, the jacking into position of scaffolding, safety screens and the like is well known. In a method taught by Eisenberg in DE4335791, a hoisting device for raising a load extending over a large horizontal length, for example, a slide screen, a partition or a theatre backdrop, hangs on several ropes which are distributed over its length and can be wound onto a common, motor-driven winding shaft, a

2014224104 10 Sep 2014 flapping-rope safety device being allocated to each rope. The arrangement could be readily adapted to the raising of construction safety screens.

In a method taught by Schwoerer in W02007000135, US2008/0257644, US2009/0146041 and US2010/0212237, a climbing shoe apparatus for climbing formwork is used to hold rails on walls of a structure on already produced concrete sections to support fittings for erecting a new concrete section. The apparatus has a sliding shoe section and a wall or ceiling shoe section, whereby the wall or ceiling shoe section can be firmly attached to a wall or ceiling of a concrete section and the sliding shoe section has means for guiding and holding a climbing rail, the wall or ceiling shoe section being connected to the sliding shoe section in an articulated manner. The climbing shoe acts to minimise moments resulting from the weight of a climbing rail and the connected fittings into an anchoring point in a wall. Via an articulated connection between the wall or ceiling and sliding shoe section it is possible for the sliding shoe section to attach to a climbing rail, with the climbing rail taking up the load, thereby acting as a counter bearing to catches formed in the sliding shoe section which support the load-bearing bolts of the climbing rail. Pivotable catches borne in the sliding shoe section serve as supports for

0 load-bearing bolts of the climbing rails, the catches able to be pivoted within the sliding shoe section in such a way that displacement of the climbing rails within a sliding shoe section is possible. When the climbing rails climb the catches are disengaged from the load-bearing bolts and once a climbing procedure has ended the catches automatically

2014224104 10 Sep 2014 pivot back into their initial position and can again hold the climbing rail immobile on the wall of a structure in its new position.

In a method variously taught by Choo in KR20020062239 and US

2005/0217934, a scaffolding system and (jackable) method of moving scaffolding includes a scaffold assembly having a plurality of elongate (vertical) members, the members including support portions, a plurality of brackets for mounting directly or indirectly to a structure, the brackets including retaining means for releasably retaining the members in a lengthwise upright orientation when mounted to a structure, and 10 supporting means for supporting at least part of the weight of said members and guides for guiding the members during repositioning of the assembly on the structure. The guides guide the members during raising and/or lowering of the assembly, the supporting means being arranged to allow passage of the support portions during raising of the assembly but 15 prevent passage of the support portions during lowering of the assembly to thereby support the assembly. The system provides a scaffolding assembly that alleviates problems known in the art by providing a system that is more readily movable despite poor weather conditions and which is simpler and more efficient. The brackets incorporate pivotable 2 0 (releasable) arms and are employed to grip the elongate members.

In a method taught by Schwoerer in US 2010/0038518, a (jackable) rail-guided climbing system provides a joint formed on the respective climbing rails, the joint allowing repositioning during construction from concreting section to concreting section to take place

2014224104 10 Sep 2014 more simply. If a concreting section is completed, climbing brackets are fastened to anchor points formed there. Subsequently, the rail-guided climbing system is repositioned either by having it lifted by a crane or selfclimbing by a lifting cylinder. The free ends of the climbing rails are 5 navigated by means of an adjustor device to slide into climbing brackets provided. With the joint provided at each climbing rail all irregularities appearing on the construction can be compensated. The joint provides each climbing rail an increased moveability so that, over an adjustable angular position of the adjacent climbing rail sections, dimensional 10 changes resulting from the dead weight of the system, varying wind load or from construction sections completed within the allowable tolerance threshold, etc. can be compensated for. This allows repositioning from a completed concrete section to a concrete section to be manufactured to be carried out without adjustment work, thereby increasing the versatility of 15 the inventive system. The rail-guided climbing system obtains its static stability through a brace framework construction, the necessary overall flexural rigidity of the system being achieved by integration of the climbing rails into the scaffolding unit. A releasable climbing is shoe employed to engage the climbing rails.

0 In a method taught by Svedberg in WO 2011/116829, a construction safety screen comprises a net, a front horizontal tube located at a front edge of the net, a rear horizontal tube located at the rear edge of the net and an attachment arrangement connecting the construction safety screen to a construction. The attachment arrangement comprises a net

2014224104 10 Sep 2014 hanger of U-shaped form, the rear horizontal tube of the net structure being accommodated in the U-shaped portion at a distance from a short side of the net structure, such that the rear horizontal tube protrudes from both sides of the U-shaped portion. The net hanger of the attachment 5 arrangement is optionally replaced by an adjustable net coupling part clamped to the rear horizontal tube. The safety screen could be readily adapted to use in elevated construction situations.

In a method taught by Le et al in CN202055617, a fencing device for construction comprises a frame, a baffle and a base, the frame 10 comprising two side vertical rods, an upper cross rod and a lower cross rod. The upper parts of the side vertical rods are symmetrically provided with two upper drum-shaped brackets, two ends of the upper cross rod being provided with bolts which extend downwards, the lower cross rod being inserted onto the lower drum-shaped brackets of the two side 15 vertical rods. The baffle comprises the frame and a protective screen and is arranged in the frame, the upper part of the base being provided with a fixed mandrel, the bottom parts of the side vertical rods being provided with shaft holes, and the side vertical rods are inserted onto the base. The fencing device disclosed by the utility model is stable and firm, can be 2 0 repeatedly used, and can protect adjacent sides of a foundation pit so as to eliminate potential safety hazards. The fencing device could be readily adapted to use in elevated construction situations.

In a method taught by Zhuang et al in CN201843355, a mobile multilayer protective screen comprises a tower, a plurality of trundles

2014224104 10 Sep 2014 arranged at the bottom of the tower and multilayer safety screens transversely laid on the tower. The mobile multilayer protective screen is mainly used for preventing overhead working personnel in building construction fields and other operation fields from falling, and is characterized by the protective screen being able to move along with the working personnel and conduct dynamic protection through continually changing of the operation position. The protective screen can move to operating points along with the overhead working personnel conveniently for conducting safe protection below the working personnel all the time, forming a safe forbidden zone on the ground to prevent personnel access. The protective screen ensures safety of personnel, is convenient and flexible and has great promotional value. The protective screen could be readily adapted to use in elevated construction situations.

In a method taught by Zhang et al in CN202559708, a lifting type scaffold floor safety protection device comprises a bottom plate, a turning plate, a connecting device, a pulling rod and an automatic pulling device, wherein the bottom plate is movably connected with the turning plate by a connecting device, and the turning plate is connected with the pulling rod capable of adjusting the incline angle. Compared with the prior art technology, the lifting type scaffold floor safety protection device has the advantages of simple structure, low cost, high work efficiency, and complete protection of the lifting type scaffold floor. The lifting type scaffold floor safety protection device provides a firm protection screen for personnel falling from an elevated position during the construction

2014224104 10 Sep 2014 process and simultaneously effectively prevents falling accident, saves the engine cost, prolongs the maintenance period, simplifies the operation and is able to be repeatedly used. The protection device could be readily adapted to use in elevated construction situations.

In a method taught by Song et al in CN2209701, a safe inclined screen of a construction scaffold comprises two connecting rod sets which can be expanded, one end of each of the connecting rod sets can be transversely arranged on different heights of the scaffold, and the other end forms a series shape and is suspended on the outside of the scaffold, 10 wherein, each connecting rod set comprises an inner and an outer side rods which are arranged in parallel and a center rod which can be pulled upwards; a falling object shield body on the scaffold directly uses positioning clamping bodies on the bottom surface of both ends of the falling object shield body to push and clamp the inner side rod respectively 15 through object placing space formed between the inner and the outer side rods; the falling object shield body being caused to be positioned and transversely arranged on a placing plane formed by two sets of the inner and the outer side rods; the substantial effects being simple structure, convenient construction and high safety. The screen system could be

0 readily adapted to use in elevated construction situations.

In a method taught by Xifa et al in CN202899596, a hydraulic (jackable) climbing protection screen device for construction comprises an anchor system, a support hanging seat, a hydraulic jacking system, a colorsteel protection screen and a guide rail. The support hanging seat

2014224104 10 Sep 2014 comprises a floor support, a hanging seat and connecting bolts for connecting the floor support and the hanging seat. A bearing pin and a sliding groove are arranged on the hanging seat. The hydraulic jacking system comprises a hydraulic main machine and a hydraulic oil cylinder.

The color-steel protection screen comprises a color-steel plate and a railing keel fixing the color-steel plate. The railing keel is fixed on the guide rail. The guide rail supports on the hanging seat. The floor support is fixed on a floor through the anchor system. The hydraulic climbing protection screen device for the construction is reasonable in structure design, strong in 10 operation, sturdy, durable, high in safety, low in cost, high in working efficiency, wide in applicable position, free of limit of floor height and flexible in function expansion.

In a method taught by Hou et al in CN101787792, a jackable building protection screen system comprises a vertically arranged guide 15 rail, wherein the outer side of the guide rail is provided with a protection screen, and the inner side of the guide rail is provided with a plurality of hanging seats; the guide rail is supported on the hanging seats through a load supporting device; the hanging seats are supported on a floor plate and are connected with the floor plate through an embedded part; an oil 2 0 cylinder component is arranged between at least one of the plurality of the hanging seats and the guide rail; and the oil cylinder component is detachably connected with the hanging seats and the guide rail respectively. The system also comprises a discharging platform, an operation platform and the like; a guide rail bracket body can be

2014224104 10 Sep 2014 ί

automatically elevated through a hydraulic system to realize a climbing function of a climbing frame. The building protection screen system has the characteristics of simple structure, easy mounting, convenient operation, high degree of safety, high construction speed and the like, and can be widely applied to modem building construction works.

The various prior art examples cited suffer to different degrees from shortcomings that inhibit their efficient use. The shortcomings relate to incapacity or, in particular, complexity of arrangement which prevents their reliable application on a large construction site with a minimum of time, skilled personnel or equipment.

The object of the present invention is to provide a jackable construction safety screen system that is simple and reliable in application and that can be employed to install safety screens speedily and safely, with a minimum requirement for skilled personnel and equipment.

According to the present invention, in the construction of a multi-storey structure, following pouring of the reinforced concrete slab of a level of the structure and the stripping away of formwork, before further work is continued on that level, safety screens are installed. The safety screens are raised to a vertical attitude at the base of the structure and vertical rails forming part of the safety screens are engaged with jaws of a plurality of guiding and retaining units fixed to levels of the structure above. The guiding and retaining units permit sliding vertical displacement of the safety screen vertical rails while guiding the rails and retaining them in their vertical orientation, a guiding and retaining unit

2014224104 10 Sep 2014 having its jaws open until a rail has intercepted it, the jaws then being closed and locked onto the rail to perform their guiding and retaining function. The guiding and retaining units are adapted to receive hydraulic jacking units employed to vertically displace the safety screen vertical rails 5 from the base of the structure and above to successive levels and to positively retain and lock the safety screen vertical rails at selected heights. The guiding and retaining units are fixed in suitable positions to the outer ends of support beams fixed to the outer parts of the reinforced concrete slabs of each completed level of the structure.

o The various aspects of the present invention will be more readily understood by reference to the following description of preferred embodiments given in relation to the accompanying drawings in which:

Figure 1 is an isometric view of a support beam with a guiding and retaining unit fixed to its outer end engaging a safety 15 screen vertical rail, a hydraulic jacking unit being set in place on said guiding and retaining unit to raise said vertical rail;

Figure 2 is an isometric view of the support beam and guiding and retaining unit of Figure 1, the jaws of said guiding and retaining unit being shown opened;

0 Figure 3 is an isometric view of the support beam and guiding and retaining unit of Figure 1, the jaws of said guiding and retaining unit being shown closed;

Figure 4 is a view of the outer end of said support beam with the articulating components of said guiding and retaining unit

2014224104 10 Sep 2014 being removed;

Figure 5 is a side view of the view of the supporting tongue of said guiding and retaining unit, obscured features of which are depicted in broken line;

Figure 6 is a partial view from above of a retaining strap pivotally supported on the free end of the ram of said hydraulic jacking unit;

Figure 7 is a frontal view (from the hook end) of a lifting bar pivotally supported on the free end of the ram of said hydraulic 10 jacking unit;

Figure 8 is a side view of the lifting bar of Figure 7.

No significance should be taken from the fact that the figures are drawn are to differing scales.

With reference to all Figures, a safety screen vertical rail 1 15 comprises two rolled C-section elements fixed back-to-back in spaced relationship by means of short, generally cylindrical separating elements 2 arranged in pairs. Said separating elements are optionally through-bolted to said C-section elements or welded to them. Suitably positioned apertures 3 are provided in said C-section elements to facilitate fixing in 2 0 place of said separating elements. The spacing between the parallel parts of said C-section elements is adjusted to permit the free ingress of the lifting bar depicted in Figures 7 and 8. Said vertical rails are deployed in vertical orientation across the face of a structure and safety screens, scaffoldings, equipment of various types, hoardings, weather shields or the

2014224104 10 Sep 2014 like are fixed in various ways to said rails.

Support beam 4 comprising two rolled U-sections arranged backto-back in spaced relationship has fixed to its inner end a short length of angle 5, the horizontal part 6 of which is provided with suitable apertures 5 8, 9 for the installation of attachment fastenings (not shown) to fix said support beam to the upper surface of a concrete slab. Said apertures are optionally circular (as depicted as feature 9) or slotted (as depicted as feature 8), to permit positional adjustment. Other suitably located apertures 7a, 7b are optionally provided in the horizontal parts of said U10 sections. Said U-sections are fixed in said spaced arrangement by said length of angle, transverse web 10 and transverse bar 11, said length of angle, said web and said bar being welded or bolted to said U-sections. The spacing between the parallel parts of said U-sections is adjusted to permit the free ingress of supporting tongue 12 of said guiding and 15 retaining unit, said supporting tongue being pivotally supported on pivot bolt 13 passing through the parallel parts of said U-sections, said pivot bolt passing through aperture 14 provided towards the inner end of said supporting tongue. Said supporting tongue is adapted to be pivoted upwardly (as depicted in Figure 1) or pivoted downwardly, in which 20 position notch 15 provided in the lower edge of said supporting tongue bears against transverse bar 11. In its said downwardly pivoted position, hook 16 of said supporting tongue is adapted to receive the inner one of a pair of separating elements 2, thereby supporting the weight of a said vertical rail and safety screens or the like fixed to it. It the preferred

2014224104 10 Sep 2014 embodiment, said supporting tongue is made in laminated form from three pieces of a suitable metal alloy material plug-welded together. With specific reference to Figure 5, an inner piece (upper edge depicted in broken line as 19) is sandwiched between two outer pieces 18, the lower 5 height of the main part of said inner piece generating a channel 25 in which is slideably accommodated latch element 17. Lugs 22 provided on the sides of said latch element slideably engage slots 20 formed in outer pieces 18, acting to limit the longitudinal displacement of said latch element and retaining it in sliding contact with the upper edge of said inner 10 piece. The lower height of the inner piece of the beak part 29 of said supporting tongue generates gap 21 which accommodates the free outer end 26 of said latch element in its fully deployed position. Lug 24 formed on the upper edge of said latch element is employed to apply a displacing force to said latch element. Said lug is provided with a suitable aperture 15 for attachment of a handle, lanyard or the like. In the said downwardly pivoted position of said supporting tongue with said latch element fully deployed, locking bolt 27 is passed through suitably located, tubular receivers 28 fixed to the upper horizontal surfaces of said support beam and through aperture 23 provided in said latch element, said locking bolt 20 acting to retain said latch element in place in which it imprisons a separating element (depicted as 2 in Figure 1) in hook 16 of said supporting tongue.

Pairs of jaw-carrying arms 30 are pivotally supported on suitably positioned pivot bolts 31 passing through apertures provided in the

2014224104 10 Sep 2014 horizontal parts of said support beam U-sections at either side towards the outer end of said support beam, slotted apertures 32 being provided in said jaw-carrying arms to permit said arms a suitable degree of axial displacement in relation to said support beam. Said jaw-carrying arms are 5 provided at their free, outer ends with transverse parts 34 which terminate at their laterally, inner edges in jaws 33. Said jaw-carrying arms are adapted to be pivotally displaced outwardly in relation to said support beam, as depicted in Figure 2, or pivotally displaced inwardly in relation to said support beam, as depicted in Figures 1 and 3. In said inwardly 10 pivotally displaced positions of said jaw-carrying arms, said jaws positively engage the near edges of said vertical rail C-sections, axially outward displacement of said jaw-carrying arms being necessary in order to have said jaws pass over said rail C-section edges. In said inwardly pivotally displaced position of said jaw-carrying arms, with said arms 15 axially displaced fully inwardly on pivot bolts 31, locking bolts 35 are inserted through suitably located apertures 37 in said horizontal parts of said support beam U-sections and through complementary apertures in said jaw-carrying arms, thereby positively locking said jaws in engagement with said near edges of vertical rail C-sections. In the 20 preferred embodiment, suitable bridles (not shown) are attached to the heads of locking bolts 27, 35, said bridles being attached in suitable positions to said support beam or said jaw-carrying arms.

With said jaws locked in engagement with said near edges of said vertical rail C-sections, a said safety screen vertical rail is free to be

2014224104 10 Sep 2014 displaced vertically in either sense. When said vertical rail is displaced upwardly, separating elements 2 successively strike the lower, outer surfaces of said supporting tongue, causing it to pivot upwardly on pivot bolt 13, thereby imposing no impediment to the passage of said vertical 5 rail. Where it is desired to secure a said vertical rail at a particular height, said rail is raised until the appropriate said separating element is positioned above said supporting tongue and is then lowered so that said separating element is received in hook 16 of said supporting tongue. If desired, said latch element is then fully deployed and locked into place to 10 capture said separating element in said hook.

Hydraulic jack 38 is provided at its lower end with yoke 39 of sufficient width and height to permit pivotal displacement through it of supporting tongue 12. Fixed to the outer surfaces of said yoke at its lower edges are channels 40 shaped to accommodate receivers 28, said channels 15 being buttressed by gussets 41 fixed to said yoke outer surfaces and, if required, to the outer surfaces of said hydraulic jack. Yoke 43 is fixed to the free end of ram 42 of said hydraulic jack. Pivotally supported within said yoke on pivot shaft 46 is lifting bar 60. Said lifting bar comprises two arms, an upper arm 48 separated from a lower arm 47 by an angle in the 20 range 70° to 120°, pivot boss 55 positioned at the line of angular change being provided with bore 56. Said upper and lower arms may be of equal length or the length of one may exceed the length of the other by up to 50 per cent. Transversely-arranged contact plate 49 is fixed to the free end of said upper arm and centrally-positioned locating plug 50 is optionally

2014224104 10 Sep 2014 provided on the outer face of said contact plate. Said locating plug is made with a width occupying 50 to 90 per cent of said space between the parallel parts of said vertical rail C-sections, said plug being provided with suitable chamfering or tapering 59 to ensure ready entry to and release 5 from said space. Hook 61 formed on the free end of said lower arm is adapted to engage the inner one of a pair of separating elements 2 of said vertical rail and, in the preferred embodiment, is strengthened by being made with two outer parts 58 plug welded to inner part 47. A retaining strap comprises side panels 44 supported on pivot shaft 46, said side 10 panels being joined by bridging piece 57 and extended laterally by straps which pass around the inner parts of said C-section elements, sprung plungers 53 in said straps engaging the edges of said C-section elements, thereby acting to retain yoke 43 and lifting bar 60 in fixed relationship to said safety screen vertical rail. Said sprung plungers are impelled inwardly 15 by springs (not shown) accommodated within housings 52 fixed to straps

45, knobs 51 formed on their outer ends being employed to withdraw said plungers from engagement with said C-section element edges. Said sprung plunger housings are optionally permanently fixed to said straps by welding or are made replaceable by being screwably fixed to threaded 2 0 bosses welded to said straps. Said hydraulic jack 38 is positioned with its lower end located by channels 40 engaging receivers 28, with plungers 53 engaging the edges of said C-section element edges and with of said hook 61 of lifting bar 60 engaging a separating element 2 of said vertical rail. Hydraulic pressure is then applied to said hydraulic jack, the force thereby

2014224104 10 Sep 2014 applied to said lifting bar causing it to pivot about pivot shaft 46 to urge transversely-arranged contact plate 49 into abutment with the inner surfaces of said C-section elements, locating plug 50 entering the space between the parallel parts of said vertical rail C-sections. Because of the 5 sliding contact between sprung plungers 53 and the edges of said Csection elements, no force is applied to said retaining strap. The force applied by ram 42 of said hydraulic jack to said separating element causes said safety screen vertical rail to be displaced upwardly, slidingly passing through jaws 33, contact with separating elements 2 displacing supporting 10 tongue 12 upwardly. From its position of full extension, said ram is retracted a small amount to lower the separating element 2 immediately above said supporting tongue to bring it into a position in which it is supported by hook 16 of said supporting tongue, said ram then being further retracted to disengage hook 61 from separating element 2.

Plungers 53 are then disengaged from the edges of said C-section elements, lifting bar 60 is separated from said vertical rail and said ram is retracted completely. Hook 61 of lifting bar 60 is then engaged with the lowest suitable separating element 2 of said vertical rail, hydraulic pressure is then re-applied to said hydraulic jack and the lifting cycle is 2 0 repeated. Lowering of said vertical rail is the reverse of the procedure described. In an alternative embodiment (not shown), locking bolts 27 are deleted and channels 40 are made with closed outer ends which support sprung plungers of the type depicted as 51, 52, 53 in Figure 6, said sprung plungers and their housings being made longer such that said plungers

2014224104 10 Sep 2014 from both sides extend through receivers 28 and abut in aperture 23 of latch element 17, thereby acting to retain said latch element in place in its said locking position.

In the preferred embodiment, pressurised hydraulic fluid is supplied from a single hydraulic power pack (not shown) to hydraulic jacks arranged to provide synchronised lifting of a plurality of said safety screen vertical rails. In this embodiment, a single hydraulic valve (not shown) controls the flow of pressurised hydraulic fluid to a manifold (not shown) connected to all said hydraulic jacks. In an alternative 10 embodiment, a manifold (not shown) supplies pressurised hydraulic fluid to separate, electrically-operated hydraulic valves (not shown) which control the flow of pressurised hydraulic fluid to individual said hydraulic jacks.

Claims (9)

1. Claims

   1. A construction site safety screen system comprising a plurality of rails comprising Csection elements deployed in spaced-apart relationship and vertical orientation across the face of the structure; safety screens, scaffoldings, equipment of various types, hoardings, weather shields or the like fixed in various ways to said rails; support beams comprising U-section elements fixed to the outer zone of each concrete slab of a structure in the same spaced-apart relationship as said rails and with their ends extending beyond the edge of each said slab; releasable means at the outer end of said support beams able to engage said rails to retain them in parallel to the outer face of said structure but allow them to be slidingly displaced upwardly or downwardly; supporting tongues pivotally supported towards the outer ends of said support beams and deployable to engage separating elements of said rails to support the weight of said rails, safety screens and the like; sliding latch elements to lock said tongues in their positions engaged with said rail elements; jacking means pivotally supported towards the outer ends of said support beams, the upper ends of the jacking means each supporting means to slidingly engage with a said rail, and means to engage said rail separating elements to raise or lower said rails; wherein said rails include suitably positioned apertures, and each said aperture is provided in said C-section elements to facilitate fixing in place of said separating elements, the spacing between said parallel parts of said C-section elements thereby being adjusted to permit the free ingress of said supporting tongues, and wherein the system includes a lifting bar, separate to, and remote from, the support beams by a hydraulic lifting cylinder, and wherein said lifting bar is in the form of a boomerang shaped element with a fulcrum located at the elbow of the boomerang shaped element, thereby enabling the lifting bar to pivot around the fulcrum as the lifting bar engages or disengages with a respective separating element, and wherein said U-sections of said support beams are fixed in said spaced arrangement, the spacing between the parallel parts of said U-sections being adjusted to permit the free ingress of said supporting tongues and portions of the lifting bar, said supporting tongues each being pivotally supported on a pivot bolt passing through the parallel parts of said U-sections and an aperture provided towards the inner end of said supporting tongue.
2. 2. The construction safety screen of Claim 1 wherein when said supporting tongue is in its downwardly pivoted position, a hook of said supporting tongue is adapted to receive the inner one of a pair of said rail separating elements, thereby supporting the weight of a said vertical rail and safety screens or the like fixed to it.
3. 3. The construction safety screen of Claim 1 in which said hydraulic lifting cylinder are each provided at their lower ends with a yoke of sufficient width and height to permit pivotal displacement through it of said supporting tongue; fixed to the outer surfaces of said yoke as its lower edges are channels shaped to accommodate receivers of tubular form, said channels being buttressed by gussets fixed to said yoke outer surfaces and, if required, to the outer surfaces of said hydraulic lifting cylinder.
4. 4. The construction safety screen of Claim 1 wherein said lifting means further comprise a yoke fixed to the uppermost end of the hydraulic lifting cylinder, and wherein said fulcrum of said lifting bar being pivotally supported within said yoke on a pivot shaft; said lifting bar comprising an upper arm separated from a lower arm by an angle in the range of 70° to 120°, said upper and lower being of equal length or the length of one may exceed the length of the other by up to 50 per cent, a pivot boss positioned at the line of angular change of said lifting bar being provided with a pivot shaft bore; a transversely-arranged contact plate being fixed to the free end of said upper arm and a centrally-positioned locating plug is optionally provided on the contact face of said contact plate, said locating plug being made with a width occupying 50 to 90 per cent of said space between said vertical rail C-sections, said plug being provided with suitable chamfering or tapering to ensure ready entry to and release from said space.
5. 5. The construction safety screen of Claim 4 wherein a retaining strap comprising side panels supported on said pivot shaft is included, said side panels being joined by a bridging piece and extended laterally by straps which pass around the inner parts of said C-section elements, sprung plungers in said straps engaging the edges of said C-section elements, thereby acting to retain said yoke and said lifting bar in fixed relationship to said safety screen rail; said sprung plungers being impelled inwardly by springs accommodated within housings fixed to said straps, knobs formed on their outer ends being employed to withdraw said plungers from engagement with said rail C-section edges, said sprung plunger housings being optionally permanently fixed to said straps by welding or made replaceable by being screw ably fixed to threaded bosses welded to said straps.
6. 6. The construction safety screen of Claim 5 wherein said hydraulic lifting cylinders are positioned with their lower end located by channels engaging said receivers with plungers engaging the edges of said rail C-sections and with said hook of said lifting bar engaging a said separating element of said rail, force applied by said hydraulic lifting cylinder to said lifting bar causes it to pivot about said pivot shaft to urge said transversely-arranged contact plate into abutment with the inner surfaces of said rail C-sections, said locating plug entering the space between the parallel parts of said rail C-sections, the sliding contact between sprung plungers and the edges of said C-section elements, minimising the application to force to said retaining strap.
7. 7. The construction safety screen of Claim 6 in which said releasable means are a set of jaws adapted to engage with and retain the vertical rail.
8. 8. The construction safety screen of Claim 7 wherein the force applied by said hydraulic lifting cylinder to said separating element causes said safety screen vertical rail to be displaced upwardly, slidingly passing through said jaws, so that subsequent contact with said separating elements displaces said supporting tongue upwardly.
9. 9. The construction safety screen of Claim 8 in which, from its position of full extension, said hydraulic lifting cylinders are retracted a small amount to lower said separating element immediately above said supporting tongue to bring it into position in which it is supported by said hook of said supporting tongue, said hydraulic lifting cylinder then being further retracted to disengage said hook from said separating element, said plungers then being disengaged from the edges of said C-section elements, said lifting bar is separated from said vertical rail and said hydraulic lifting cylinder are retracted completely; said hook of said lifting bar is then engaged with the lowest suitable said separating element of said rail, force is then re-applied by said hydraulic lifting means and said lifting cycle is repeated.