1 AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION INNOVATION PATENT "Clamp for Safety Railing" The following statement is a full description of this invention, including the best method of performing it known to me: 2 Clamp for Safety Railing 5 Background and Summary of the Invention This invention concerns the use of clamping devices and is particularly adapted to the use of clamping devices on building sites for affixing temporary safety railing at elevated positions on buildings. 10 There is an increasing emphasis on the provision of safety railing on building sites to prevent accidental falling of personnel from dangerous heights. Sometimes such railing can be readily fastened into position by known techniques. But often the structure of a building, the state of its erection, or the nature of work yet to be done means it is difficult 15 to support satisfactory safety railing without unduly restricting access to the parts of the building under construction. Often it has proven necessary to custom manufacture components for particular sites and/or remove roofing or damage plasterwork in order to satisfactorily affix suitable railings. For safety railing around the roof of a building it is known to support the posts of the railing from rafters. The present invention uses a 20 mechanism clamped to the rafter. It is useful to be able to clamp such a mechanism at the preferred distance inwards from the edge of the roof so that the safety railing is positioned the correct distance from the roof edge. But a problem arises when roofing material is already in place. Battens affixed to the top face of the rafters, and extending at right angles to the rafters, can limit the positions at which the mechanism can be clamped to a rafter. It 25 is useful to be able to clamp such a mechanism at the preferred distance inwards from the edge of the roof so that the safety railing is positioned the correct distance from the roof edge. An aim of the present invention is to provide a device which overcomes or reduces these difficulties. 30 Attaching support railing to sloping rafters can be difficult because the rafter slopes vary from building to building and even within individual buildings and it is inconvenient and expensive to carry specifically angled systems to suit all the possible slopes. An aim of 3 some embodiments of the present invention is to reduce this difficulty by having the device adjustable on site for use with roofs of any slope. An aim of another form of the invention is to provide a method of attaching a safety railing 5 which reduces the range of hardware required for jobs involving many different modes of attachment. Accordingly, in one aspect the invention provides an apparatus for securing to a rafter of a building frame a support post for a temporary safety rail, said apparatus comprising a 10 clamp portion adapted to clamp to the rafter, said clamp portion comprising a pair of jaws actuatable towards and away from each other, wherein a first of said jaws comprises a pair of arms, said arms being separated so said clamp portion may be positioned to clamp the rafter between said jaws while an elongate member fastened to the rafter and at right angles to the rafter extends between said arms. 15 Preferably the apparatus further comprises: - a post attachment portion adapted to be releasably attached to the support post, - a rotatably adjustable connection to adjust the angular relationship between the clamp portion and the post attachment portion, and 20 - selectably locking means to restrict rotational movement between the clamp portion and the post attachment portion, wherein said locking means acts to retain said angular relationship at a selectable one of a plurality of set positions. 25 In a second aspect the invention provides a method of attaching a temporary safety railing to a rafter of a building frame, said rafter having an upwardly facing top face and a downwardly facing bottom face, said method comprising: - positioning adjacent the rafter a clamp which has a pair of jaws actuatable towards and away from each other; 30 - positioning a first of said jaws against said top face of the rafter, said first jaw comprising a pair of arms extending across said top face such that a gap between said arms extends across said top face; 4 - positioning the second of said jaws against the bottom face of the rafter; - tightening the clamp against said top and bottom faces to thereby fasten the clamp to the rafter; and - attaching the safety railing to the clamp. 5 A post in said safety railing may be attached to an elongate joining piece, the elongate joining piece attached to said clamp by a rotatably adjustable connection, and the rotatably adjustable connection adjusted and locked with said post held in a generally vertical orientation. 10 A roof batten of the building frame may be fastened to said top of the rafter with at least a portion of the batten extending across said rafter within said gap between the arms. Brief Description of the Drawings 15 In order that the invention may be more fully understood there will now be described, by way of example only, preferred embodiments and other elements of the invention with reference to the accompanying drawings where: Figure 1 is an exploded view of a device according to one embodiment of the present 20 invention; Figure 2 is a rear view of one of the components in Figure 1; Figure 3 is a partially cross-sectioned plan view looking down upon the device in Figure 1 when being used in a first configuration; Figure 4 is an elevation view of a safety railing assembly incorporating the device 25 illustrated in Figure 1 when attached in a second configuration to a frame of a building; Figure 5 is an elevation view of an alternative safety railing assembly wherein the device in Figure 1 is attached in a third configuration to a frame member of a building; 30 Figure 6 is a side view showing a third example of a safety railing assembly wherein the securing device of Figure 1 is being used in a fourth configuration to secure the assembly to a sloping rafter of a building frame; and 5 Figure 7 is an enlargement showing the circled portion of Figure 6. Description of Examples of the Invention and the Preferred Embodiment 5 As seen in Figures 1 to 4, the securing device 10 consists of a clamp portion 12, a post attachment portion 14, a pressure plate 16, washer 18 and nut 20. All the components are made of steel and galvanised. The device 10 is used to support a post 28 which in turn is clamped to three rails 100. A 10 connector 27 is used between the device 10 and the post 28. The rails 100 are spaced vertically in accordance with government regulations. The rails 100 are also supported elsewhere by other such posts and together form a safety railing assembly. The post attachment portion 14 comprises a clamping socket 22 welded to an arm portion 15 24. The clamping socket 22 is made from a length of square hollow section steel tube to which is welded a threaded nut 26 aligned with a hole in the tube so that a suitably slightly smaller sized square section steel tube may be slid into the socket 22 and clamped at a chosen height by means of an L-shaped hand screw 30 engaged with the nut 26 and extending through the wall of the tube of clamping socket 22. 20 The arm portion 24 has a central plate portion 32 with a pair of flanges 34 and 36 on respective sides thereof all extending at right angles from the clamping socket 22. The central plate portion 32 extends beyond the flanges 34 and 36 in a semi-circular protrusion 38. The central plate portion 32 has a circular hole 40 therethrough, the perimeter of which 25 carries a continuous array of teeth 42. The hole 40 extends for about half its diameter beyond the flanges 34 and 36 into the protrusion 38. The clamp portion 12 has a fixed jaw portion 46 and a moveable jaw portion 48. The moveable jaw portion 48 has a base 50 formed from a short length of square hollow section 30 tube and a bearing end portion 49 rigidly attached thereto. The base 50 is inserted as a sliding fit into a corresponding square hollow section base 54 of the fixed jaw portion 46.
6 The fixed jaw portion 46 has a bearing end portion 47 and a coupling portion 68 each rigidly attached to the base 54. The respective outer ends 51 and 55 of bases 50 and 54 are blanked off. A threaded shaft 5 58 extends axially through the bases 50 and 54, through a plain hole 52 in the end 51 and threadedly engages with a nut 60 welded to the end 55. The threaded shaft 58 has a hexagonal head 62 and 64 rigidly attached at each end and an associated washer 63 and 65 between the respective head and end. By turning either one of the heads 62, 64 the bearing end portions 47 and 49 of respective jaw portions 46 and 48 are pulled towards each other 10 or allowed to separate. The coupling portion 68 of the jaw portion 46 comprises a circular backing plate 70, a toothed circular plate 72 and a threaded shaft 74 all extending coaxially with each other and at right angles to the shaft 58 such that the plate 72 extends from the backing plate 70 15 and the shaft 74 extends from the plate 72. The backing plate 70, toothed plate 72 and threaded shaft 74 are all rigidly affixed to each other and to the base 54 of the fixed jaw portion 46. The circular plate 72 carries a continuous array of teeth 76 extending radially outwards therefrom. In use these mate with the teeth 42 on the post attachment portion 14. 20 Both the plate 72 and the hole 40 in the embodiment illustrated have 36 teeth. So each tooth is aligned at an angle of 100 relative to their immediately neighbouring teeth. In alternative embodiments, 40, 48 or 60 teeth may be used for example and these would correspond to tooth spacings of 9', 7120 and 6' respectively. 25 In use the toothed circular plate 72 is mated with the toothed hole 40 with the clamp portion 12 and post attachment portion 14 aligned as desired, the pressure plate 16 and washer 18 fed onto the shaft 74 and nut 20 tightened onto the shaft. The pressure plate 16 has a flange 17 on its rim which bears onto the central plate portion 32 surrounding the hole 40. The thickness of the plate 72 and the central plate portion 32 are nominally the 30 same and the flange ensures that if, due to manufacturing tolerances, the plate 72 is in fact slightly thicker than the central plate portion 32, the pressure plate 16 still bears tightly onto the central plate portion 32. The flange 17 may be an integral part of the metal of the 7 pressure plate 16, but is preferably formed by adhering a ring of any appropriate material to the face of the pressure plate. The bearing end portion 49 of the moveable jaw portion 48 is bifurcated. It has a pair of 5 arms 78 which extend sideways relative to the shaft 58 and also extend in the direction of the shaft 58 to beyond the head 62. A pair of face plates 80 extend outwards from respective arms 78. A side plate 82 extends at almost right angles to the face plates 80 and adjacent the base 50. The arms 78 each carry a terminal tooth which forms a spike 79 pointing towards the opposite jaw portion. 10 The bearing end portion 53 of the fixed jaw portion 46 is less extensively bifurcated than that of the moveable jaw portion. A pair of arms 84 extend sideways relative to the shaft 58 but do not extend in the direction of the shaft 58 beyond the head 64. A face plates 86 is affixed to the arms 84. A side plate 88 extends at almost right angles to the face plate 15 86. Side plates 82 and 88 are coplanar. The arms 84 each carry a terminal tooth which forms a spike 85 pointing towards the opposite jaw portion. As seen in Figure 3, the device 10 may be attached to a frame member 90 by rotating either one of the heads 62, 64 to tighten the face plates 80 and 86 against the frame member. The 20 spikes 79 and 85 assist in preventing the clamp portion twisting on the frame member 90 by either wrapping around the member, as shown in Figure 3, or by biting into the material of thicker members. The frame members may be timber or steel. The face plates 80 and 86 are aligned 3' from being at right angles to the axis of the shaft 25 58. The face plates therefore taper towards each other in the direction of their respective arms with an included taper angle of 6'. As shown in Figure 3, the clamp has been tightened on the timber frame member 90 only enough for the face plates 80 and 86 to start engaging the outer comers 130 and 132 of the timber. In use the clamp would be tightened further, causing some distortion of the timber, so the face plates would more firmly clamp 30 against the engaging faces 134 and 136 of the timber. The taper between the faces causes localised and uneven distortion of the timber and thus reduces the likelihood of the timber moving in the clamp. The solid clamping action provided by the invention provides a 8 substantial advantage over prior art systems which merely wrap around and/or are nailed to a frame member they are attaching to. The faceplates 80 and 86 extend about 37mm from the side plate 82, 88 to spikes 79, 85. 5 This allows a 35mm thick stud to be accommodated as shown in Figure 3. For thicker timber the spikes 79 and 85 bite into the timber and the timber faces are still engaged by the faceplates 80 and 86. If, instead of the spikes 79 and 85, a lip was formed to extend along the ends of jaw portions 46 and 48, the result would be much less satisfactory because the lip would not dig into the timber as far as the spikes would. It can be seen that, 10 unlike some prior art brackets used to fasten to rafters, the jaws of the clamp do not need to wrap over the corners 130 and 132 and engage the side face 138 of the timber frame member 90 in order to tightly hold the timber. The clamp portion is sized so that it can clamp to members from 65mm to 110mm. 15 The device 10 can be readily clamped to wall studs which are very close to brickwork, or even hard up against brickwork by using the biting-in characteristics of the spikes 79 and 85. 20 A notch 39 is formed on the central extreme tip of the semi-circular protrusion 38. Notches 66a, 66b, 67a, 67b and 71 a-/ are also formed on the perimeter of the backing plate 70. The notches 66a and 66b are 180' apart and aligned with the direction of shaft 58. The notches 67a and 67b are 1800 apart and aligned with the faceplate 86, so they are aligned at 900 to notches 66a and 66b. The twelve notches 71a to 71/ are spaced 10' apart with three 25 on each side of each of notches 66a and 66b. The diameter of the semi-circular protrusion 38 and the backing plate 70 are the same, so the notch 39 may be conveniently aligned with a designated notch on the backing plate to set the desired angular alignment between the clamp portion 12 and post attachment portion 14. 30 The device 10 is shown in a first angular configuration in Figure 3. In this configuration the notch 39 is aligned with notch 66a, which is closest to the moveable jaw 48, so the securing device is extended linearly. This aligns the post attachment portion 14 in the 9 same direction as the alignment of the frame member 90 and spaces the clamping socket 22 the greatest available distance from the frame member 90. The clamping socket 22 is made from square section tube having the same cross-sectional 5 dimensions as the main upright body 29 of the post 28. As seen in Figure 4, a short straight length of square section tube of a slightly smaller cross section is used as a connector 27 between the clamping socket and the post 28. The connector 27 is clamped at one end by the hand screw 30 and at the other end by a similarly configured hand screw 96 on the post 28. The height of the post may be adjusted by means of sliding and clamping the connector 10 27 as appropriate within the post 28 or the socket 22. A plurality of posts are erected in a spaced relationship and rails 100 for the safety railing fastened between them. Each post has rigidly attached clamps 98 whereby the rails 100 are attached. Any of many well known clamping systems may be used to attach the rails to the post. 15 As seen in Figure 4, the device 10 may be used to secure a post 28 to a vertical stud 92 in the frame of a building under construction. In the configuration shown, the notch 39 is aligned with notch 66b which is the most distant from the moveable jaw 48. Thus the clamp portion 12 and the post attachment portion 14 are aligned linearly, but are rotated over upon each other. So, although (as in Figure 3) the clamping socket 22 is aligned in 20 the same direction (vertically) as the stud 92, the clamping socket and stud are now spaced closer together than for the Figure 3 configuration. As either one of the heads 62, 64 may be turned to tighten the clamp, the clamp may be easily tightened onto the stud from either inside or outside the building. This provides 25 significant advantage when access from one side is restricted or dangerous. The device described above has a particularly useful application in that it is capable of supporting a safety railing by attachment from beneath a rafter. Figure 5 shows the device 10 being used to secure a post 28 to a horizontal rafter 94. In this configuration the notch 30 39 is aligned with notch 67a and the socket 22 is aligned at right angles to the rafter 94. The clamp portion may be tightened from above by turning head 62 or from below by 10 turning head 64. A rattle gun fitted with a socket drive is particularly useful for tightening and loosening the clamp. The device 10 has an especially useful application in that it may be used to support 5 generally vertically aligned posts of a safety railing when attached from the underside of sloping rafters of a building during construction. An example of an embodiment of the invention in this regard is shown in Figures 6 and 7. In Figures 6 and 7 the rafter 102 is aligned at 300 to the horizontal and extends out beyond 10 the wall (not shown) of the building. The notch 39 on the post attachment portion is aligned with notch 711 on the clamp portion before the nut 20 is tightened. The clamp portion 12 is thereby aligned at an angle of 30' to the post attachment portion, in contrast to the linear alignment of Figure 3. The clamp portion 12 is clamped to the sloping rafter 102 near the rafter's lower end, so that the clamping socket 22 is axially aligned 15 horizontally below the lowest line of the eave 106 of the building. A bent connector 127 is used to connect the post 28 to the socket 22. While the connectors 27 described in relation to above described embodiments were straight, the connector 127 is bent in a curve at right angles. Bent connector 127 is formed from the same tube stock as that used for connector 27 so its ends slide neatly into the bottom of the post 28 and socket 22 for clamping by the 20 L-screws 96 and 30 respectively. The height of the post 28 can be adjusted by loosening screw 96, and the spacing of the post from the eave 106 adjusted by use of screw 30. An advantage of the above-described bifurcation in the moveable jaw portion 48 can be seen in particular in the enlargement shown in Figure 7. The building frame 107 has a top 25 hat section steel batten 108 affixed to the upper surface of the rafter 102 at the place where it is desired to clamp the securing device 10. Corrugated steel sheets 114 are affixed to the batten 108. The cross section of such battens has a trough-like centre portion 110, a pair of upstanding walls 111, and a pair outwardly extending feet 112 at its bottom. The bifurcation of the jaw portion 48 allows the arms 78 to be positioned one on each side of a 30 foot 112 with one of the arms 78 and its associated face plate 80 extending into the trough 110 where it hooks over the top of the rafter 102. If the arm 78 and face plate 80 could not 11 extend into the trough 110, there would need to be a much longer horizontal component of the bent connector 127 which would cause undesirable flex in the safety railing structure. The embodiment of the securing device illustrated in Figure 1 has its teeth 42 and 76 at 100 5 alignments. Its use means that whatever the angle of a sloping rafter, the post 28 can be aligned within 5' of vertical. It is normally preferred for safety railing to not be inwardly sloping, in order to provide optimum access to the edge of the roof, and it is generally accepted that the upright posts of a safety railing system can lean up to 15' outwards from the building. 10 As best seen in Figure 1, the edges 87 of the faceplate 86 are positioned further outwards than the corresponding edges 89 of the side plate 88 when measuring in the direction of the length of the elongate frame member 90. Likewise the edges 81 of the faceplates 80 are positioned further outwards than the corresponding edges 83 of the side plates 82. This 15 means that if the clamp portion 12 is clamped to a vertical timber wall stud at the top or bottom of the stud adjacent a horizontal top plate or bottom plate, the edges 83 and 88 can be pressed to abut the top plate or bottom plate and the faceplates 80 and 86 would then overlap onto the top plate or bottom plate. Portion of the top plate or bottom plate, and the joint face between it and the stud, would therefore be captured between the faces 80 and 86 20 and thus within the clamping action. The strength of the safety railing would then not be as dependent on the strength of a possibly insecurely nailed joint between the stud and top plate or bottom plate. It will be appreciated that identical securing devices of the type described can be adjusted 25 into different configurations for many different applications. This means that construction of a safety railing system on a building site can be readily customised using a relative small variety of components, so reducing the inventory required to be carried to a site. Whilst the above description includes the preferred embodiments of the invention, it is to 30 be understood that many variations, alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the essential features or the spirit or ambit of the invention.
12 It will be also understood that where the word "comprise", and variations such as "comprises" and "comprising", are used in this specification, unless the context requires otherwise such use is intended to imply the inclusion of a stated feature or features but is 5 not to be taken as excluding the presence of other feature or features. The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that such prior art forms part of the common general knowledge in Australia.