AU2007201042B2

AU2007201042B2 - Method and Apparatus for Clamping

Info

Publication number: AU2007201042B2
Application number: AU2007201042A
Authority: AU
Inventors: Peter Horton
Original assignee: Buildsafe Equipment Sales Pty Ltd
Current assignee: Buildsafe Equipment Sales Pty Ltd
Priority date: 2007-03-10
Filing date: 2007-03-10
Publication date: 2014-12-18
Anticipated expiration: 2027-03-10
Also published as: AU2007201042A1

Abstract

Abstract A clamp comprising a rigid elongate member having a longitudinal axis. A jaw is 5 moveable relative to said elongate member in the direction of said longitudinal axis. A frame includes a retaining portion through which said elongate member forms a sliding fit. A gripping member is held captive by the frame, said gripping member having an aperture therein where said aperture is sized to form a loose fit upon said elongate member. There is means for tilting said gripping member relative to said 10 elongate member whereby the gripping member frictionally binds onto said elongate member, and means for moving said frame relative to said gripping member while said gripping member is so frictionally bound onto said elongate member to thereby move said jaw relative to said elongate member in said axial direction. - 20 25" 84 FIGURE 1

Description

1 AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION for the invention entitled: "Method and Apparatus for Clamping" The invention is described in the following statement: 2 METHOD AND APPARATUS FOR CLAMPING 5 Background and Summary of the Invention This invention concerns the use of clamping devices and is particularly adapted to the use of such clamping devices on building sites for affixing temporary safety railing at elevated positions. 10 There is an increasing emphasis on the provision of safety railing on building sites to prevent accidental falling of personnel from dangerous heights. Often such railing can be conveniently fastened into position by nailing, bolting or screwing supports into portion of the structure of the building and it does not matter that, when later 15 removed, the fastenings leave a damaged surface because such damage will later be covered by plasterwork, cladding or the like. However in some situations, it is desired to fasten safety railing supports to exposed brickwork, which may already be rendered or painted, and it is desired that such fastening does not leave any discernable damage when removed. There is a need for a system which provides the 20 relatively strong fastening required to satisfactorily hold a safety rail but does not damage the surface it is affixed to. An aim of the present invention is to provide a means to overcome this difficulty. Accordingly, in one aspect the invention provides a clamp comprising: 25 - a rigid elongate member having a longitudinal axis, - a jaw moveable relative to said elongate member in the direction of said longitudinal axis, - a frame including a retaining portion through which said elongate member forms a sliding fit, 30 - a gripping member held captive by the frame, said gripping member having an aperture therein where said aperture is sized to form a loose fit 3 upon said elongate member, - means for tilting said gripping member relative to said elongate member whereby the gripping member frictionally binds onto said elongate member, and 5 - means for moving said frame relative to said gripping member while said gripping member is so frictionally bound onto said elongate member to thereby move said jaw relative to said elongate member in said axial direction. 10 In another aspect the invention provides a method of clamping a rigid elongate member relative to a first and second surface where said surfaces are fixed relative to each other, said method comprising: (a) sliding said elongate member into a frame of a clamp assembly, and through an aperture in a gripping member of the clamp assembly, wherein: 15 (i) said clamp assembly includes a jaw, and (ii) said gripping member: - is held captive by said frame, and - forms a loose fit around said elongate member, (b) rotating a threaded member of the clamp assembly to thereby tilt the gripping 20 member relative to the elongate member whereby the gripping member frictionally binds onto said elongate member, (c) continuing to rotate said threaded screw whereby said frame is moved relative to said gripping member while said gripping member is frictionally bound onto said elongate member to thereby move said first jaw in said axial 25 direction, (d) engaging a second jaw, which is affixed to said elongate member, with said second fixed surface and engaging said first jaw with said first fixed surface, and (e) continuing to rotate said threaded screw to more firmly press said first and 30 second jaws against said first and second fixed surfaces to thereby clamp said jaws against said fixed surfaces.

4 In a further aspect the invention provides a method of supporting a temporary safety railing on a building by clamping a rigid elongate member relative to a first and second surface on the building where said surfaces are fixed relative to each other, said method comprising: 5 (a) sliding said elongate member into a frame of a clamp assembly, and through an aperture in a gripping member of the clamp assembly, wherein: (i) said clamp assembly includes a jaw, and (ii) said gripping member: - is held captive by said frame, and 10 - forms a loose fit around said elongate member, (b) rotating a threaded member of the clamp assembly to thereby tilt the gripping member relative to the elongate member whereby the gripping member frictionally binds onto said elongate member, (c) continuing to rotate said threaded screw whereby said frame is moved relative 15 to said gripping member while said gripping member is frictionally bound onto said elongate member to thereby move said first jaw in said axial direction, (d) engaging a second jaw, which is affixed to said elongate member, with said second fixed surface and engaging said first jaw with said first fixed surface, 20 (e) continuing to rotate said threaded screw to more firmly press said first and second jaws against said first and second fixed surfaces to thereby clamp said jaws against said fixed surfaces, and (f) attaching the safety railing to said elongate member. 25 The rigid elongate member may be a support for a temporary safety railing on a building. Preferably said retaining portion of the frame is tubular. Preferably said aperture in the gripping member is a rectangular or square hole through the gripping member. 30 Preferably said rigid elongate member is a length of square hollow section steel. Preferably said frame includes a pair of side walls, each side wall having a hole 5 therethrough into which is engaged a respective portion of said gripping member whereby the gripping member is held captive between the side walls. The gripping member may be held sufficiently loosely within said frame to allow limited rotary movement of the gripping member, said rotary movement permitting opposed edges 5 of said aperture in the gripping member to bear against opposite sides of said elongate member and thereby produce said frictional binding. The gripping member may be loosely engaged with and captive to a shaft which carries a thread and rotation of said shaft causes said tilting of the gripping member. 10 Preferably a female-threaded member retained by the frame engages said threaded shaft whereby rotation of the shaft causes said shaft to move along said female threaded member and thereby tilt said gripping member relative to said elongate member. 15 Preferably said clamping face of the jaw extends perpendicular to rigid elongate member. The clamping face of jaw may have a cushioned facing. Said aperture in the gripping member is preferably a hole through the gripping member. Said aperture in the gripping member may be a rectangular or square hole 20 through the gripping member. Preferably said gripping member comprises a main body portion having said aperture therein and a tab portion having a hole therethrough and an end of said shaft is held captive through said hole in the tab portion. 25 Brief Description of the Drawings 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 30 with reference to the accompanying drawings where: Figure 1 is a perspective view of a portion of a clamp assembly according to a first embodiment of the invention; 6 Figure 2 is a perspective view of a portion of a clamp assembly according to a second embodiment of the invention; Figure 3 is a side view of a pair of clamp assemblies shown positioned ready to commence tightening of a clamp onto a masonry column; 5 Figure 4 is a partial cut-away view of Figure 3 including an enlargement of the portion indicated; Figure 5 shows the same views as in Figure 4 but the gripping members tilted to grip the elongate member, including an enlargement of the portion indicated; Figure 6 shows the views like Figure 5 but with the tightening screw tightened 10 so that the two jaws press against the opposite faces of the masonry, including an enlargement of the portion indicated; Figure 7 is a perspective view of a nut frame component forming part of the assembly shown in Figure 1; and Figure 8 is a perspective view of the gripping member forming part of the clamp 15 assembly shown in Figure 1. Description of Examples of the Invention and the Preferred Embodiment The clamp assembly 10 shown in Figure 1 comprises a main frame 12 to which is 20 attached a jaw 14. The main frame 12 includes a tubular portion 16 formed by a short length of square hollow section steel tube which is welded a pair of steel side plates 18 and 20. The jaw 14 is formed from a short length of rectangular hollow section steel to which a thin layer of sheet rubber 24 has been affixed. 25 Relative higher, lower and sideways positions of components of the clamp assembly will be described with reference to the orientation shown in Figure 1 although it will be appreciated that the clamp can operate in any orientation. The inside dimensions of the tube 16 are chosen so that it is a loose sliding fit over a 30 much longer length of square hollow section steel tube 23 (shown dashed in Figure 1) which is to be used as a support for a safety railing system on a building site. Conveniently the long length of tube forming the support 23 is square hollow section 7 steel having an outside dimension of 35mm and a wall thickness of 2mm, and the tubular portion 16 of the frame is square hollow section steel having an inside dimension of 36mm and a wall thickness of 2mm. The longitudinal axis 17 of the tube 23 is coincident with that of the tubular portion 16. 5 Each side plate 18 and 20 has a square hole 26 and 28 respectively passing through it above tubular portion 16. A nut frame 30 (shown in more detail in Figure 7) is held captive between the two 10 side plates 18 and 20. The nut frame 30 has a main body 31 which is a shape cut from 10mm steel plate. It has a pair of wings 38 and 40 protruding sideways so that they loosely engage with the square holes 26 and 28. By this means the nut frame 30 is held captive between the side plates 18 and 20 and a limited degree of up and down rotary movement is permitted. A hole (obscured in Figure 1) is bored centrally 15 through the nut frame body 31 and a threaded nut 34 is welded to the front face 36 of the nut frame body 31. The thread 29 in the nut 34 engages with the thread 37 on a bolt 32 such that the bolt 32 can be screwed through the nut frame. The bolt 32 passes with a wide clearance fit 20 through the hole in the nut frame body. The clamp assembly 10 includes a gripping member 42 which is shown in detail in Figure 8. The gripping member 42 is a shape cut from 10mm plate steel. It has a main body portion 42 having the general shape of a squared-off letter 0. The main 25 body portion 42 has a square central aperture 48 which has a flat top face 49 and bottom face 50. The top and bottom faces of the aperture 48 have sharp square edges where they meet the front and rear faces 51 and 52 of the gripping member 42. Extending upwards from the main body portion 42 is a tab portion 54 which has a hole 56 therethrough. 30 The bolt 32 carries at its leading end 33 a pair of circular collars 44 and 46 which are welded to the bolt. The bolt passes through the hole 56 between the two collars. The 8 collars are spaced apart by about 13mm which is 3mm greater than the thickness of the gripping member 42. The hole 56 is a loose clearance fit on the shank of the bolt between the two collars 44 and 46. The main body portion 42 has a pair of sides 58 and 60 which extend into cut outs 62 and 64 in respective side plates 18 and 20. 5 The clamp assembly 80 shown in Figure 2 differs from the assembly 10 shown in Figure 1 in as much as the open sided cut outs 62 and 64 of assembly 10 are replaced by quadrilateral shaped apertures 86 and 88 in the side plates where the apertures are holes through the plates rather than the recesses used in assembly 10. There is also a 10 rod 85 welded to, and extending between, the side plates 82 and 83. The rod 85 is positioned such that in use it rests across and in contact with the tube 23 and thus provides additional support to the tube 23. The clamp assembly 80 also has a piece of thick rubber sheet 90 positioned across the 15 width of the assembly and extending a little more than fully through the apertures 86 and 88. The rubber is positioned towards the bottom of the apertures with the rubber in slight compression and slightly domed towards its centre. The rubber sheet 90 acts as a spring to urge the bottom of the gripping member towards the bolt head. 20 A length of square hollow section tube 23 (shown in the drawings as phantom lines) is used with the clamp assembly 10 to form a clamp. Figures 3 to 6 illustrate how clamp assembly 10, clamp assembly 80 and a length 23 of square tube can be used in conjunction to attach the tube 23 to a masonry column. The tube 23 is to be used as a support for a temporary safety railing. The masonry column has a rendered and 25 painted finish which it is desired to not damage during the time of erection, use and dismantling of the safety railing. The tube 23 is first fed through the tubular portion 16 and the gripping member 42 of each clamp assembly 10 and 80, having first checked that the bolts 32 are adjusted so 30 that each gripping member 42 is retracted towards the head of its respective bolt. To facilitate easy sliding of the tube 23 into assembly 10, it may be useful to use a finger to press the upper portion of the gripping member towards the head of the bolt, as 9 indicated in Figure 3. In the case of clamp assembly 80, a thick width of rubber sheet 90 is positioned towards the bottom of the apertures 86 and 88 with the rubber in slight compression and slightly domed towards its centre. The rubber 90 urges the bottom 65 of the gripping member towards the head 35 of its respective bolt 32. 5 At this stage the faces 51 and 52 of the gripping member are at right angles to the axis of the tube 23, the top and bottom walls 49 and 50 of the aperture 48 are parallel to the walls of the tube 23 and the tube is free to slide through the aperture 48. This is shown in Figure 4. 10 The head 35 of each bolt 32 is then rotated to first lock the gripping member onto the tube 23. This is down by rotating the head of the bolt, which causes the tab 54 of the gripping member to be pushed away from the nut frame, ie to move outwards as seen in Figures 4 and 5 until such time as the gripping member is tilted from the 15 orthogonal position relative to the axis 17. At this stage, as seen in Figure 5, the outer sharp edge 66 of the top face of aperture 49 bites down hard down onto the upper face of the tube 23 and the inside sharp edge 68 of the bottom face of aperture 49 bites up hard onto the lower face of the tube 23. Figure 4 shows the gripping member aligned orthogonally to the tube 23 while Figure 5 shows the gripping members tilted to the 20 point where they grip onto the tube. When the gripping members grips onto the tube, the bolt is then held in a fixed position relative to the tube. Further turning of the bolt then causes the frame 12 to move inwards from the position shown in Figure 5. In the progression from the position as shown in Figure 5 25 to that as shown in Figure 6, it can be seen that each nut 34 has moved further up along its respective bolt. As the bolt is turned, the respective frame and jaw moves inwards until the rubber layer 24 on the front faces of the jaws contact respective opposite faces 95 and 96 of the masonry column 94. Further tightening of the bolts increases the clamping force by which the clamp assembly is held to the column. 30 The rubber spring 90 shown in Figure 6 has bent upwards in the middle. This maintains a sideways force on the gripping member.

10 A rubber layer 25 is also affixed to the underside of the frame 12, at right angles to the face of the jaw, where the frame would otherwise contact the masonry at right angles to the respective jaws. 5 Whilst the above description includes preferred embodiments of the invention, it is to 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. 10 For example, it is not essential to provide two adjustable jaws on separate frames. The tube 23 could instead have a simple non-adjustable jaw welded to it so that the clamping is achieved by tightening a single adjustable jaw. Alternatively the non adjustable jaw could be not welded to the tube but instead slide into a simple self 15 locking position. Also, although the embodiments of the invention shown in the drawings have the jaws tightening towards each other in order to clamp onto surfaces between them, the frames may be reversed so the clamp tightens by pressing the jaws apart in order to 20 affix the clamp into a gap between a pair of inwardly opposed surfaces. Thus, in order to press against the fixed surfaces, the jaws may be pressed towards each other or away from each other. It will be also understood that where the word "comprise", and variations such as 25 "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 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, 30 an acknowledgment or any form of suggestion that such prior art forms part of the common general knowledge in Australia.

Claims

1. A clamp comprising: - a rigid elongate member having a longitudinal axis, 5 - a jaw moveable relative to said elongate member in the direction of said longitudinal axis, - a frame including a retaining portion through which said elongate member forms a sliding fit, - a gripping member held captive by the frame, said gripping member 10 having an aperture therein where said aperture is sized to form a loose fit upon said elongate member, - means for tilting said gripping member relative to said elongate member whereby the gripping member frictionally binds onto said elongate member, and 15 - means for moving said frame relative to said gripping member while said gripping member is so frictionally bound onto said elongate member to thereby move said jaw relative to said elongate member in said axial direction. 20

2. A clamp according to claim 1 wherein said retaining portion of the frame is tubular.

3. A clamp according to claim I or 2 wherein said aperture in the gripping member is a rectangular or square hole through the gripping member. 25

4. A clamp according to any one of any one of claims I to 4 wherein said rigid elongate member is a length of square hollow section steel.

5. A clamp according to any one of the preceding claims wherein said rigid 30 elongate member is a support for a temporary safety railing on a building

6. A clamp according to any one of the preceding claims wherein said frame 12 includes a pair of side walls, each side wall having a hole therethrough into which is engaged a respective portion of said gripping member whereby the gripping member is held captive between the side walls. 5

7. A clamp according to any one of the preceding claims wherein said gripping member is held sufficiently loosely within said frame to allow limited rotary movement of the gripping member, said rotary movement permitting opposed edges of said aperture in the gripping member to bear against opposite sides of said elongate member and thereby produce said frictional binding. 10

8. A clamp according to any one of the preceding claims wherein said gripping member is loosely engaged with and captive to a shaft which carries a thread and rotation of said shaft causes said tilting of the gripping member. 15

9. A clamp according to claim 8 wherein a female-threaded member retained by the frame engages said threaded shaft whereby rotation of the shaft causes said shaft to move along said female-threaded member and thereby tilt said gripping member relative to said elongate member. 20

10. A clamp according to any one of the preceding claims wherein said clamping face of the jaw extends perpendicular to rigid elongate member.

11. A clamp according to any one of the preceding claims wherein said clamping face ofjaw has a cushioned facing. 25

12. A clamp according to any one of the preceding claims wherein said aperture in the gripping member is a hole through the gripping member.

13. A clamp according to claim 8 wherein said aperture in the gripping member is 30 a rectangular or square hole through the gripping member.

14. A clamp according to any one of the preceding claims wherein said gripping 13 member comprises a main body portion having said aperture therein and a tab portion having a hole therethrough and an end of said shaft is held captive through said hole in the tab portion. 5

15. A method of clamping a rigid elongate member relative to a first and second surface where said surfaces are fixed relative to each other, said method comprising: (a) sliding said elongate member into a frame of a clamp assembly, and through an aperture in a gripping member of the clamp assembly, wherein: (i) said clamp assembly includes a jaw, and 10 (ii) said gripping member: - is held captive by said frame, and - forms a loose fit around said elongate member, (b) rotating a threaded member of the clamp assembly to thereby tilt the gripping member relative to the elongate member whereby the gripping member 15 frictionally binds onto said elongate member, (c) continuing to rotate said threaded screw whereby said frame is moved relative to said gripping member while said gripping member is frictionally bound onto said elongate member to thereby move said first jaw in said axial direction, 20 (d) engaging a second jaw, which is affixed to said elongate member, with said second fixed surface and engaging said first jaw with said first fixed surface, and (e) continuing to rotate said threaded screw to more firmly press said first and second jaws against said first and second fixed surfaces to thereby clamp said 25 jaws against said fixed surfaces.

16. A method of supporting a temporary safety railing on a building by clamping a rigid elongate member relative to a first and second surface on the building where said surfaces are fixed relative to each other, said method comprising: 30 (a) sliding said elongate member into a frame of a clamp assembly, and through an aperture in a gripping member of the clamp assembly, wherein: (i) said clamp assembly includes a jaw, and 14 (ii) said gripping member: - is held captive by said frame, and - forms a loose fit around said elongate member, (b) rotating a threaded member of the clamp assembly to thereby tilt the gripping 5 member relative to the elongate member whereby the gripping member frictionally binds onto said elongate member, (c) continuing to rotate said threaded screw whereby said frame is moved relative to said gripping member while said gripping member is frictionally bound onto said elongate member to thereby move said first jaw in said axial 10 direction, (d) engaging a second jaw, which is affixed to said elongate member, with said second fixed surface and engaging said first jaw with said first fixed surface, (e) continuing to rotate said threaded screw to more firmly press said first and second jaws against said first and second fixed surfaces to thereby clamp said 15 jaws against said fixed surfaces, and (f) attaching the safety railing to said elongate member. Dated this 16th day of June 2011 Buildsafe Australia Pty Ltd 20 by their patent attorneys Morcom Pernat