Drop-head support assembly
This invention relates to an improved drop-head support assembly for use in the construction of concrete roofs, floors, ceilings or the like. 
     Drop-head assemblies of the kind to which the invention refers are used in combination with builders scaffolding or props to support the shuttering, usually in the form of decking panels with or without decking beams, used in the construction of concrete floors and other horizontal, or non-vertical, structures. Such assemblies are used to enable the shuttering elements to be removed progressively, prior to final hardening of the concrete, without leaving the concrete totally unsupported. Thus, the shuttering elements can be removed and re-used without taking away the props or scaffold elements which remain in position until the concrete is fully set. 
     Known drop-head assemblies for this purpose tend to be complicated and expensive to manufacture and it is among the objects of the present invention to provide a simplified assembly which is robust and relatively cheap to manufacture. 
     According to the present invention, there is provided a drop-head support assembly of the kind hereinbefore referred to, which comprises an upright pillar one end of which is provided, directly or indirectly, to be atached to a prop or the like and the other end of which is formed with, or is provided to receive, a head plate device a shuttering support member slidably mounted on the pillar, and a wedge device captively mounted on the pillar, wherein the wedge device includes an elongated tapered part which is pivotally attached to the pillar so as to be movable, in a vertical direction, between an operative position where it extends transverse to the axis of the pillar to hold the support member in its operative position, and an inoperative position where it is co-extensive with the axis of the pillar to permit movement of the support member into its inoperative position. 
     Preferably, the pillar is provided to detachably receive the head plate device so that, in practice, different forms of head plate may be used selectively. 
    
    
     The invention is illustrated by way of example in the accompanying drawings in which, 
     FIG. 1 is a section through a drop-head assembly according to the invention showing the support member in its raised or operative position, 
     FIG. 2 is an elevation corresponding to FIG. 1, 
     FIG. 3 is an elevation in the direction of the arrow &#34;3&#34; of FIG. 2, 
     FIG. 4 is an elevation corresponding to FIG. 3 but showing the support member in its lowered or inoperative position, 
     FIG. 5 is a section on the line 5--5 of FIG. 1, 
     FIG. 6 is a section on the line 6--6 of FIG. 1, and 
     FIGS. 7 and 8 are elevations of the pillar. 
    
    
     Referring to the drawings, there is shown a drop-head support assembly comprising an upright pillar 1 including a pair of spaced flanges 2 each having an inwardly directed web 3 of a length to present a space 4 therebetween. 
     The lower ends of the flanges 2 are fixed, as by welding, to a transverse base plate 5. The base plate 5 has associated therewith hook bolts 6 which serve to attach the assembly to the head of a prop indicated at 7. Stop plates 8, fixed to the flanges 2, are provided near the lower end of the pillar 1 for the purpose hereinafter described. 
     The webs 3 extend upwards from the lower ends of the flanges 2 at a distance which is approximately one half of the length of the flanges 2 and support a transversely disposed pin 9 of rectangular cross-section, the pin 9 also extending at its ends into openings formed in the flanges 2 in which openings it is welded to the flanges 2. 
     Spaced above the pin 9 is a web plate 10 which extends across the full distance between the flanges 2 and is fixed to the latter. 
     In the space between the pin 9 and the web plate 10 there is provided a wedge device 11. The device 11 comprises an elongated flange element 12, a pair of tapered elements 13 which are spaced apart and lie perpendicular to the flange element 12, and a wedge retainer bar 14 the ends of which are fixed in the space between the tapered elements 13. As can be seen from the drawing, the retainer bar 14 is formed to present an opening or slot 15 extending lengthwise of the elements 12 and 13 and the pin 9 extends through the opening or slot 15 so that the wedge device is held captive on the pillar 1. Also, it can be seen that the wedge device 11 is pivotable about the pin 9 so that it is movable, in a vertical direction, from its horizontal or operative position as shown in FIGS. 1 to 3 to its vertical or inoperative position as shown in FIG. 4 where it lies in the same vertical plane as that of the pillar 1. 
     In the operative position of the wedge device 11, the tapered faces of the elements 13 are in engagement with the uppermost face of the pin 9 and the flange element 12 supports an apertured support member 16 which is vertically slidable on the pillar 1. Thus, by hammering the wedge device to the right as shown in FIGS. 1 and 3, the member 16 is forced upwards into engagement with a pair of stop plates 17 fixed to the flanges 2 where it is temporarily retained. 
     In order to move the support member 16 into the lowered or inoperative position, the wedge device 11 is hammered in the opposite direction until it is free to pivot about the pin 9 and falls into the position shown in FIG. 4 whereupon the support member 16 slides downwardly over the pillar 1 into the position also shown in FIG. 4, where it is in engagement with, and supported by, the stop plates 8. In this respect, the retainer bar 14 is formed at one end with an angular portion 18 which engages the rectangular pin 9 to retain the wedge device 11 in a vertical position within the confines of the pillar 1. 
     The support member 16, as can best be seen in FIG. 6, consists of a flat rectangular plate 19 having a central rectangular aperture 20 by which it can slide over the pillar 1. The plate 19 has, adjacent each edge thereof, a pair of upstanding pegs 21 by which, in use, the ends of decking or other beams indicated at B are attached to the support member. The underside of the plate 19 has fixed thereto a pair of reinforcing or packing elements 22 which are engaged by the flange 12 of the wedge device 11. 
     At its upper end the pillar 1 is provided with a detachable head plate device 23 having a transverse plate 24 to which is fixed a central downwardly depending flange 25 having a transverse hole to receive a nut and bolt 26. When the head plate device is in position, the bolt is arranged to be received in a slot 27 formed in the upper edge of the web plate 10. The head plate is held firmly in position by tightening the bolt to effect locking engagement between the flange 25 and the web plate 10. To avoid having loose nuts and bolts which can be mislaid, the nut is preferably welded to the flange 25 and the end of the bolt is burned over so that it cannot be removed from the nut. 
     As can be seen from the drawing the flange 25 of the head plate device is positioned centrally relative to the pillar 1, whereas the web plate 10 is offset relative to the pillar 1. This arrangement ensures that the head plate device 23 which must be positioned centrally on the pillar 1, cannot be wrongly positioned. Furthermore, since the head plate device is detachable it provides the advantage that it can be replaced by head plates of different forms. However, it will be appreciated that, if desired, the head plate may be permanently fixed to the upper end of the pillar 1. 
     In use, a drop-head support assembly as hereinbefore described is attached to a prop 7 and the prop is adjusted to the required height. A decking beam B is then attached, as hereinbefore described, by one of its ends to the support member 16, the support member being held in its uppermost or operative position by the wedge device 11 as shown in FIGS. 1 to 3. The other end of the decking beam B is then attached to a second support member 16 and so on to build a framework on which shuttering panels or other shuttering means (not shown) are supported. In this position, the uppermost surfaces of the shuttering elements are level with the upper surface of the head plate devices 23 thereby providing a continuous flat surface. 
     In order to strike or dismantle the structure, the wedge devices 11 are hammered to the left as shown in FIGS. 1 to 3 and are caused to pivot downwardly into the inoperative position shown in FIG. 4. This results in the support members 16, and thus also the decking beams and shuttering elements, sliding downwardly relative to the pillars 1 into the position shown in FIG. 4. This provides sufficient space to remove the decking beams and the shuttering elements for re-use. In this respect, it will be seen that the aforementioned operation does not in any way affect the position of the head plate devices 23 which remain in position to support the concrete structure. Thus, it will be appreciated that the shuttering can be removed after initial setting of the concrete leaving the prop in position with the head plate devices to support the concrete until final setting thereof. 
     In practice, when handling the assembly, there may be a tendency, if the bolt 26 is not fully tightened, for the device 23 to fall out of the slot 27. To prevent this, the web plate 10 is formed with a dimple or projection 28 which extends into a hole 29 formed in the flange 25. Alternatively, the projection 28 can be provided on the flange 25 and the hole 29 formed in the web plate 10.