A LIFTING APPARATUS FOR A SAFETY SCREEN Field of the Invention
 The present invention relates generally to a lifting apparatus for lifting a safety screen disposed adjacent an external region of a multi-storey building. The present invention also relates generally to methods of lifting safety screens disposed adjacent an external region of a multi-storey building.
Background of the Invention
 When a multi-storey building is under construction, safety screens may be deployed adjacent an outer edge of the building to inhibit workers and materials falling from the edge of the building. The safety screens typically extend across roughly three storeys, and generally all around the building. They include a structural support frame, restraints and a plurality of mesh panels affixed thereto. The screens are to screen upper floors as they are formed during construction, and they must be elevated as the construction progresses.
 The structural frames include a pair of longitudinal frame members disposed side- by-side and oriented generally vertically. The longitudinal frame members are in the form of lipped channels and a pair of lipped channels are referred to as a soldier. Each lipped channel is spaced about 100 mm laterally from one another, and each one has a plurality of apertures provided at selected distances along the length of their walls. The apertures of opposed lipped channel walls are adapted to receive a support pin which extends horizontally between the channels. There are a plurality of support pins normally installed along the channels, about 1500mm to 1800mm apart. The support pins are set back from a front wall of the soldier in a recess between opposed walls. However, the support pins are heavy, expensive to manufacture and partly because there are so many, they are time consuming to install.
 The screens are held in position adjacent the edge of the building by screen support props.
 Known methods of elevating the screens involve detaching and folding in a plurality of support props and elevating the screens with either cranes or forklifts.
 The present invention seeks to provide a new method of lifting safety screens.
Summary of the Invention
 According to one form of the invention there is provided a lifting apparatus adapted to vertically lift a safety screen assembly having a support structure having spaced-apart front and rear walls and a mesh safety panel attached to a rear wall of the support structure, the lifting apparatus including:
a lifting arm including a base in use mounted adjacent the front wall of the support structure, the lifting arm including an extensible arm including a head end; and
a lifting attachment disposed on the head end of the extensible arm wherein the lifting attachment is adapted to interengage with a front wall of the support structure so that the extensible arm is substantially vertical when interengaged with the front wall of the support structure.
 The lifting arm may be operated by a lever with mechanical advantage to be operated by an operator, such as a manual winch or other kind of ratcheting device.
Preferably, however, the lifting arm is a powered lifting arm, and may be electrical or operated by some other power source. Preferably the powered lifting arm is a hydraulic ram.
 Preferably the lifting attachment includes:
a chassis; and
one or more connecting devices mounted on the chassis, the connector devices adapted to engage with the front region of the structural element.
 Preferably the support structure is in the form of spaced-apart pairs of elongate support elements and first and second connecting devices are disposed at respective left and right portions of the main body so that each connector device connects to respective elongate support elements.
 In one arrangement the arrangement is such that the support structure includes apertures in the front wall and the connecting devices include catches for interengaging with the apertures by insertion into the apertures.
 Preferably the catches include fingers for interengaging with the structural element.
 Preferably the safety screen lifter the fingers extend from the connector body at an upward angle to facilitate retention on the connecting devices.
 Preferably the chassis includes a pivot to pivotally connect the connector bodies thereto.
 Preferably the pivot is disposed at left and right ends of the chassis and the connector bodies hang from the pivot to facilitate catching the apertures.
[0 6] Preferably there is provided a holding bracket for holding the support structure in an elevated position.
 Preferably the holding bracket can adopt a deployed position in which catches on the holding bracket interengage with the front wall of the support structure, and a stowed position in which the catches are withdrawn from interengagement with the front wall of the support structure.
 Preferably the holding bracket is linearly extensible and retractable.
 Preferably the catches on the holding bracket are fingers for extending into apertures on the front wall of the support structure.
 Preferably an emergency stop is provided, which is an arm which in a normal position extends from a region adjacent the base of the hydraulic ram so as to engage with the support structure.
 Preferably the support structure includes support pins extending between pairs of elongate elements, and the emergency stop is in the form of a ratchet in which the arm of the emergency stop is pivotally connected to a mounting point of the hydraulic arm base, and which allows the upward passage of the support pins but inhibits the downward passage of the support pins.
 In accordance with another aspect of the present invention there is provided a method of lifting a safety screen having a support structure, itself having spaced-apart front and rear walls and a mesh safety panel attached to a rear wall of the support structure, the method including the steps of:
attaching a lifting attachment as described herein to the front wall of the support structure; and
lifting the screen via the lifting attachment.
 Preferably the method includes the step of extending a holding bracket to interengage with the support structure to hold the support structure at the end of a lifting stroke.
 The front region of the structural element is arranged to include a plurality of apertures extending through the front region and spaced apart from one another along a longitudinal axis at about 100mm intervals therealong. The structural element is hollow and the apertures are through holes in a front wall of the structural element.
 Preferably there is provided a plurality of connector bodies. In one preferred arrangement, there are provided first and a second connector bodies. Preferably the first and second connector bodies are disposed at respective left and right portions of the main body. Preferably the connectors are. spaced apart from one another on the main body to facilitate stability of engagement with the structural element.
 Preferably the connector bodies include catches for interengaging with the apertures. Preferably the catches include fingers for retaining the structural element.
Preferably the fingers extend from the connector body at an upward angle to facilitate retention on the connector body.
 Preferably the main body includes a pivot to connect the connector bodies.
Preferably the pivot is disposed at left and right ends of the main body and the connector bodies hang from the pivot.
 Preferably the main body is in the form of a cylinder, disposed transverse to the connector bodies.
 Preferably the main body includes a mount suitable for mounting a hydraulic ram. The mount may be in the form of a plate comprising an aperture, the plate extending from a base portion of the main body.
 According to yet another form of the present invention there is provided a method of lifting a safety screen, the safety screen having a support structure and screen panels affixed thereto, the support structure having a supporting region for supporting a mesh screen and a front region opposite the supporting region, the method including the steps of:
attaching a lifting attachment as above described to a front region of one or more support structure; and
lifting the screen via the lifting attachment.
 Preferably the method includes the step of disconnecting a base of a prop which is holding the screen in an elevated position and pivoting the prop about its upper end so that the prop is parallel with the screen and the one or more structural elements.
 The method may include the step of holding the support structural at the end of a lifting stroke. The holding step includes extending a holding bracket from the building at the level of the building floor.
 According to still another aspect of the present invention there is provided a holding bracket which includes a lifting attachment as abovedescribed.
 Preferably the safety stop mount includes a backing plate which in use mounts to an upper surface of a hydraulic lifting bracket.
 According to a still further aspect of the present invention there is provided a lifting apparatus adapted to vertically lift a safety screen assembly having a support structure having spaced-apart front and rear walls, the walls having apertures spaced along the front and rear walls, and a mesh safety panel attached to a rear wall of the support structure, the lifting apparatus including:
a powered lifting arm including a base in use mounted on a foot in turn mounted on an elongate support member adjacent the front wall of the support structure, the lifting arm including an extensible arm including a head end; and
a lifting attachment disposed on the head end of the extensible arm wherein the lifting attachment includes fingers mounted on backing plates, the fingers adapted to insert into the apertures on the walls of the support structure to interengage therewith so that the extensible arm is substantially vertical when interengaged with the front wall of the support structure.
 In this specification, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date:
part of common general knowledge; or
known to be relevant to an attempt to solve any problem with which this specification is concerned.
Brief Description of the Drawings
 The invention will now be further explained and illustrated by reference to the accompanying drawings in which:
 Figure 1 is a perspective view, from the standpoint of a person standing on a floor of a multi-storey building, of a lifting apparatus beside a safety screen in accordance with a preferred embodiment of the invention;
 Figure 2 is a perspective view of the lifting apparatus of Figure 1 , connected to the safety screen at a climber foot and a climbing head;
 Figure 3 is a perspective view of the climber head connected to a soldier, the view from the other side of the safety screen assembly, with mesh removed for clarity;
 Figure 4 is a perspective view of the lifting apparatus of Figures 1 and 2 with the lifting foot retracted to a retracted position;
 Figure 5 is a perspective view of the lifting apparatus of Figure 1 with the hydraulic rams extended to the end of their lifting stroke;
 Figure 6 is a perspective detail view of the lifting feet engaged with the soldier viewed from the building; and
 Figure 7 is a perspective detail view of a lifting foot engaged with the soldier. Detailed Description of a Preferred Embodiment
 Referring to the Figures there is shown a lifting apparatus generally indicated at 30, the lifting apparatus for lifting a safety screen 5.
 The drawings show formwork 6 disposed at an edge portion of a multi-storey building floor 7 under construction, the safety screen indicated at 5. The safety screen 5 is disposed adjacent and operatively connected to the building floor 7 of the multi-storey building. The safety screens 5 are to inhibit worker falls from the building. The safety screens 5 include a support structure 10 and a plurality of mesh 11 or other infill panels affixed thereto. The safety screens 5 extend across about three or four storeys of the multistorey building. .
 The support structure 10 includes a plurality of pairs of structural members 2 and 13, each pair disposed side-by-side and spaced apart from other pairs by a distance of roughly 1.6 to 2.2 metres. The structural members 12 and 13 are lipped channel 14 and a pair of lipped channels is referred to as a soldier 15. Each soldier 15 is substantially upwardly-extending, each structural member 12, 3 being about 100 mm apart from one another, and each soldier 15 has a plurality of through apertures 16 provided at about 100mm centre to centre along each wall 17, 18, 19 of the lipped channel 14.
 When the safety screen 5 is assembled, a plurality of support pins 20 extend horizontally between the channels 14, through apertures 16 from wall 18 to its opposed wall 18 on an adjacent channel 14. The support pins 20 are installed about 1500 to 1800mm apart from one another, and thus there are a great plurality of pins 20 to provide for each screen 10. The support pins 20 when installed are disposed in apertures 16 which are disposed on wall 18 in an intermediate position, between walls 17 and 19, for increased strength so that the support pins 20 are recessed from wall 17.
 Once upper storey is poured and structural work commenced thereon, the screens 10 are elevated so that workers may safely construct and finish the upper storey. Other safety fencing (not shown) is then erected on the edge 7 of the multi-storey building. The lifting apparatus to achieve that lifting will now be described in further detail.
 A lifting apparatus generally indicated at 30 is provided including hydraulically- operated lifting rams 35 including a base cylinder 36 and an extensible ram 37. A lifting
attachment 50 is provided on the distal end of the extensible ram 37, the lifting attachment 50 being adapted to engage with front wall 17 of the soldiers 15. The lifting ram 35 is mounted on a lifting foot 48 which in turn is mounted on an elongate element 4 known as a needle 3. The needle 3 is mounted on a floor 7 of the multi-storey building and extends outwardly over the edge of the formwork 6 so as to facilitate the safety screen being mounted spaced from the edge of the formwork 6.
 A lifting head 49 form a lifting attachment 50 and includes a main body 51 in the form of a chassis 52, the chassis 52 being in the form of a spine 53 and a cross member 54, the cross member 54 being disposed at an upper region of the spine 53.
 The lifting attachment 50 further includes a connecting devices 55, 56 for engaging with the front wall 17 of each structural element 12 and 13. The connecting devices 55, 56 include a backing plate 57 and a plurality of catches 58 disposed thereon and extending therefrom. The catches 58 facilitate interengagement with apertures 16 on the front wall 17 of each soldier 15 by inserting therethrough. Each catch 58 is in the form of a finger 59 for facilitating insertion into the apertures 16 on wall 17, each finger 59 being spaced apart from an adjacent finger 59 on the backing plate. Each finger 59 extends from the backing plate 57 at an upward angle so as to facilitate catching and removal of the fingers 59 from the apertures 16 when desired, by advancing or retracting the ram 37 slightly, while at the same time inhibiting removal of the fingers 59 from the aperture 16 when engaged.
 Each backing plate 57 is spaced from its adjacent backing plate to facilitate stability by virtue of being disposed at respective ends of the cross member 54. Each backing plate 57 is pivotally connected to the cross member 54 to facilitate attachment to the cross member 54.
 The lifting foot 48 in the form of a holding bracket 70 is provided to hold the screen in a selected vertical position. The holding bracket 70 can move between a retracted position and a deployed position and is in the form of an extensible bracket 71. The hydraulically-operated lifting ram's base cylinder 36 is operatively connected to the lifting foot 48 but not to the extensible bracket 71. That is, the extensible bracket 71 includes a carriage 73 on which a connecting device 155, 156 (similar to 55, 56 on the lifting head 49) is mounted, which includes backing plates 157, and catches 158 in the form of fingers 159. The carriage 73 includes a recess or cutout 74 which receives the mounting of the base of the base cylinder 36 when in the deployed position (Figures 2, 3, 6). The retracted position of the holding bracket 70 is one in which the fingers 159 are withdrawn from the apertures 6 and the deployed position is one in which the carriage 73 is linearly extended from its retracted position and the fingers 159 are engaged with the apertures 16. The carriage 73
includes a retention cage 69 to retain the carriage 73 on the lifting foot but facilitate extension and retraction movement between the deployed and retracted positions.
 Guides 64 are provided, to facilitate stability of engagement between the structural element 12, 13 and the needle 3. The guides 64 facilitate vertical movement when lifting, and facilitate retention of the screen against the needle 3. The guides 64 are in the form of hooks 67 which extend from the lifting foot 48 and are adapted to be disposed when assembled , partially encircling wall 17 of the soldier 15.
 The needle 3 includes an emergency stop 68 which acts to inhibit the unintended fall of safety screens 5 in the event of a failure of the hydraulic rams. The emergency stop 68 includes a pivoting arm 67 which normally adopts a deployed position in which it extends into the gap between the channels 14 and past the support pins 20, and functions something like a ratchet. The pivoting arm 67 is pivotally connected at the end of needle 3 so as to allow the upward passing of the support pins 20 when the screen 5 is being lifted by the hydraulic rams 35, .but to inhibit the downward passage of the support pins 20 if the screen falls downwards in an emergency event. The pivoting arms 67 would be held out of the way in an upwardly pivoting position in a controlled descent of the safety screens 5.
 The main body 51 is constructed from steel and the connectors are welded to the main body 51.
 To lift the safety screen 5, a user attaches lifting attachment 50 as above described to a front region 4, specifically inserting the fingers 59 into apertures 16 on that wall, of the soldiers 15. Each hydraulic ram 35 should have its lifting head 50 at the same level as all the other rams. The hydraulic ram 35 is then ready to extend to lift the lifting attachment 50 and safety screen 5. Support pins 20 are not required for lifting.
 At the end of a lifting stroke the user holds the safety screen 5 by extending the carriage 73 of the holding bracket 70 into the deployed position. The fingers 159 engage with the apertures 16 on front wall 17 of the soldiers 15 just like the attachment 50. Then the fingers 59 of the lifting attachment 50 are withdrawn from the apertures 16 on front wall 17, the safety screen 5 is safely held in place by the holding bracket 70, and the hydraulic ram 35 is retracted to the base of its stroke, and lifting may begin again by inserting fingers from the lifting head 50 into the apertures 16 on wall 17. The fingers 59 and 159, being angled, facilitate retention against the backing plate, and to remove from the apertures 16, the hydraulic ram is retracted, or, in the case of the foot carriage 73, the hydraulic ram 35 is slightly extended.
 Thus, upon re-insertion of the lifting head 50, the foot carriage 73 is retracted fully to the retracted position. The rams may then be extended to their full stroke.
 The word 'comprising' and forms of the word 'comprising' as used in this description do not limit the invention claimed to exclude any variants or additions.
 Modifications and improvements to the invention will be readily apparent to those skilled in the art. Such modifications and improvements are intended to be within the scope of this invention.