GB2489213A - Removable clamp - Google Patents

Abstract

A removable clamp suitable for attachment to a structure, where the structure features a horizontal surface and two opposed, upright sides. The clamp comprises two relatively movable clamping portions 2, 4, with a first clamping portion 2 having a clamping face 6 for clamping against one of the upright sides of the structure, and a second clamping portion 4 having a clamping face 8 for clamping against the other of the upright sides of the structure. The clamping means exerts a clamping force against the upright sides of the structure. The first and/or the second portion has a mounting means 40 for mounting a post or other component on the clamp. Preferably the clamp features a guide means 16 to guide the movement of at least one of the clamping portions. A tongue 28 on one clamping portion 4 engages with a horizontal slot 26 on the other clamping portion to prevent twisting of the clamp in use. The invention may be applied to vertical plinths associated with bridges.

Description

Title: Temporary Additions to Building Structures

Field of the Invention

The present invention relates to a removable device for attachment of temporary additions to building structures, especially to bridges; a system comprising the clamp; and to a method of attaching temporary additions to a building structure, such as a bridge.

Background of the Invention

It is well known to provide temporary additions to building structures, e.g. a temporary work platform to allow easy access to parts of a structure, or a safety barrier to prevent workers from falling from the structure to the ground, or indeed to is protect passers-by below the structure by preventing any objects or debris such as tools or construction materials from falling off the structure.

A particular example concerns the installation of permanent barriers on the sides of bridges, or repairing or maintaining existing barriers. In such circumstances it is usually desirable to provide a temporary safety panel (e.g. comprising metal mesh or metal railings) along the sides of the bridge.

A conventional system for attaching a temporary addftion, such as a safety barrier, to the side of a bridge, requires an anchor to be drilled into the concrete plinth at the side of the bridge (by way of explanation, it is customary to provide a concrete plinth at the side of the bridge, on which a permanent railing can be mounted). The protruding end of the anchor is screw-threaded, and a metal plate is secured in place on the horizontal upper surface of the plinth by a nut which is fed onto the screw-threaded end of the anchor. The metal plate has mounting means (e.g. suitably shaped and dimensioned recesses) to mount one or more upright metal posts, to which uprights can in turn be fastened a vertical safety panel.

The anchor/plate/post system outlined above suffers from a number of drawbacks.

Firstly, and most evidently, it requires a number of holes to be drilled into the concrete plinth. This may weaken the structure of the plinth if the holes are left unrepaired or, in the alternative, requires repairs to the concrete to fill the holes once the temporary additions are removed. Secondly, a hole drilled in the concrete plinth may often be aborted if it strikes a metal reinforcing rod or the like within the concrete plinth. Another problem with the prior art system is that, if the bridge passes over a road, railway or other thoroughfare, the road, railway or other thoroughfare must usually be temporarily closed whilst the safety panels are installed, because of 1° the hazard presented by articles or objects falling off the bridge. A third deficiency of the prior art system is that the vertical posts are not strong enough to meet the criteria for public access to the bridge and instead are sufficient only to allow for access by a temporary workforee.

is The present invention relates to a novel device which, inter cilia, in particular embodiments seeks to avoid or reduce the problems experienced by the prior art system outlined above.

Summary of the Invention

In a first aspect the invention provides a removable clamp for attachment to a structure, the structure having a generally horizontal surface and two opposed, generally upright sides; the clamp comprising: two relatively movable clamping portions, with a first clamping portion having a clamping face for clamping against one of the upright sides of the structure, and a second clamping portion having a clamping face for clamping against the other of the upright sides of the structure; clamping means for exerting a clamping force against the upright sides of the structure; and wherein the first and/or the second portion has a mounting means for mounting a post or other component on the clamp.

In a second aspect, the invention provides a system for attaching a temporary addition to a structure, the system comprising: a removable clamp in accordance with the first aspect of the invention, in combination with a post or other component mounted on, and preferably secured to, the mounting means provided on the clamp. Typically the system will comprise a plurality of clamps, and a plurality of posts or other components. The system may further comprise a safety panel, or a temporary work platform, attached to one or more of the posts mounted on the mounting means.

In some embodiments the clamp comprises a static portion, and the two clamping portions are movable relative to each other and to the static portion. In other embodiments there is no static portion.

Preferably the clamp comprises at least one screw-threaded member which is retained in one portion of the clamp and is fastened to the other portion of the clamp by a bolt or the like, such that rotation of the bolt in one direction will tend to cause relative movement of the two clamping portions of the clamp inwards, towards each other, thus applying a clamping force, via the clamping faces, to the upright sides of the is structure. The clamping force can be increased by continued rotation of bolt, until the desired clamping force has been applied. This can be checked by use of a torque meter or the like. Rotation of the bolt in the other direction will allow relative outward motion of the clamping portions, away from each other, reducing or removing entirely the clamping force, allowing the clamp to be removed from the structure. If desired, the clamping means may additionally comprise biassing means which tends to urge the two clamping portions either towards each other or, more preferably, apart. For example, the biassing means may comprise one or more springs.

The two relatively-movable clamping portions can be joined together by one or more screw-threaded members which, conveniently, are the same screw-threaded members which comprise the clamping means. Preferably the clamp comprises a plurality of clamping means, so as to provide for a more equal distribution of clamping force across the clamping faces than if a single clamping means were used. In one embodiment, the clamp comprises two or more spaced-apart screw-threaded members or clamping elements which form part of the clamping means.

In some embodiments, the clamp of the invention may be such that the clamping forced is applied along a single, substantially horizontal plane, along a long axis of the clamp.

However, this may be difficult to achieve. For example, it will normally be desirable for the clamping means to be readily accessible, to facilitate attachment to, and detachment from, the structure. Accordingly, in many embodiments the clamping means will include one or more moveable clamping elements disposed towards an upper portion of the clamp adjustment of the clamping elements serving to apply, or release, a clamping force to the clamping faces.

The clamping elements may conveniently comprise one or more screw-threaded components (e.g. bolts), which are in screw-threaded engagement with a corresponding retainer, such as a nut. The clamping elements being disposed towards is an upper portion of the claim, they are readily accessed for suitable adjustment.

However, this vertically asymmetric disposition of the clamping elements means that the clamping force tends to be vertically off-centre, and introduces a tuming moment tending to cause the top of the clamping portions to pivot inwards and the bottom of the clamping portions to swing outwards, which would prevent effective attachment of the clamp to the structure. This can be countered by providing moment-resisting means. In one embodiment, the moment-resisting means comprises a substantially non-deformable engagement between the clamping portions, or between the clamping portions and an intervening static portion. The substantially non-deformable engagement will preferably be provided on the clamp lower than the clamping elements, and need not be readily accessible.

In a particular embodiment the moment-resisting means comprises a projecting tongue formed on one clamping portion, which tongue is received within a correspondingly shaped and dimensioned aperture formed on the other clamping portion. The tongue may slide through the aperture as the clamping portions move relative to each other, and thus also serves as a guide means to guide the inward and outward movement of the clamping portions.

The relatively movable clamping portions of the clamp are desirably relatively slidably movable. Desirably at least one of the movable portions comprises a guide means, and at least part of the other portion slides within the guide means.

In one embodiment, part the clamp is provided with a channel section, and at least part of one or both of the clamping portions slides within the channel section.

Conveniently, the channel section may comprise a substantially horizontal surface with up-raised flanges at opposed edges thereof, with one or both clamping portions io having at least a part which is shaped and dimensioned to be received by, and move within, the channel section.

The channel section or other guide means may be formed as a static part of the clamp, and may act as a common channel section or guide means for both clamping portions is of the clamp, or for just one of the clamping portions. Alternatively the clamp may have a channel section or guide means on one of the clamping portions, which channel section or guide means is engaged by the other clamping portion.

In some embodiments, additional or alternative to the guide means defined above, the clamp may comprise an aperture, within which is locatable a projection which can move within the aperture. The aperture may be circular, square, rectangular, hexagonal etc. and the projection will be correspondingly shaped and dimensioned to be received by the aperture. In one embodiment, one of the clamping portions comprises an aperture which is engaged by a projecting tongue formed on the other clamping portion. Such additional guide means may advantageously additionally function as a moment-resisting means, as described previously above.

The clamp will comprise mounting means for mounting a post or other component on the clamp. Any sort of mounting may be employed, provided it confers the desired degree of strength and rigidity. For example, the mounting means may comprise a projecting collar, within which a post may be received. The collar may be circular in cross section, or square, rectangular or indeed any other shape, to receive an appropriately shaped and dimensioned post. In one embodiment the collar is substantially tubular or cylindrical, and positioned such that, when the clamp is in situ on the structure, the post is substantially upright. In some embodiments, the clamp may comprise a plurality of mounting means, on each of which a respective post or other component may be mounted.

The mounting means may additionally comprise a locking or securing means, by which the post or other component may be locked or secured to the clamp. This may include one or more apertures to receive one or more retaining members, such as a boh, which pass through the post and are fastened by a nut. Additionally, or alternatively, the post or other component may be secured by one or more detents, which are urged by biasing means (such as a spring) into engagement with a co- operating recess. The detent may be provided on the clamp and received by a co-operating recess on the post or the like, or vice versa. In some embodiments the clamp and/or the post or other component will be provided with a pin, attached to is flexible attachment means (e.g. a cord, cable, wire or chain), which pin passes through suitable aligned apertures in the post and mounting means.

Desirably the clamp is formed at least partly from metal, such as steel. More preferably the clamp is formed substantially or entirely from metal.

In a particular preferred embodiment, the clamp is adapted and configured to be clamped to a concrete plinth at the side of a bridge, so that temporary safety railings or barriers can be securely attached to the plinth, via the clamp, whilst work is ongoing to install permanent safety barriers or to repair or maintain existing safety barriers. In the UK, for road bridges, such a concrete plinth is typically 5 00mm to 600mm wide, but may on occasion be up to 1000mm wide, and for pedestrian footbridges the plinth is usually 200mm to 250mm wide.

If desired, a clamp in accordance with the invention can be made with a sufficient extent of travel of the relatively movable clamping portions such that the same clamp can be used to clamp to either a road bridge concrete plinth (especially a plinth from 500mm to 600mm in width) or to a footbridge plinth of about 250mm width.

Alternatively, clamps of different sizes can be made; a larger clamp adapted and configured for use with road bridges; and a smaller clamp adapted and configured for use with footbridges.

In a third aspect, the invention provides a method of attaching a temporary addition to a building structure, especially, but not necessarily, attaching a temporary addition to a bridge, the method comprising the steps of: clamping, to opposed upright faces of the structure, a clamp in accordance with the first aspect of the invention defined above; and mounting on the clamp a post or other component.

Preferably the method further comprises attaching to the post or other component mounted on a clamp a further element or member, such as a safety panel, safety rail, temporary work platform or the like.

More typically the method comprises attaching a plurality of clamps to the structure, is preferably spaced at a suitable separation to provide adequate numbers and distribution of mounting means on which the posts or other components may be mounted.

In some embodiments, it may be necessary to perform a preliminary task to expose one, or possibly both, of the upright sides of the structure. For example, where a concrete plinth is provided on a bridge, the bridge will usually be provided with a surface of tarmac, asphalt or the like which will cover most of the inner side of the plinth. In order to attach the clamp of the invention, a small section of the tarmac or asphalt may need to be removed. Such a task is however far easier than drilling into the concrete plinth itself, which is required by prior art attachment systems. In addition, removing the tarmac or asphalt does not weaken the plinth or impair its integrity, unlike drilling into the plinth itself, and can readily be repaired. Of course, if the bridge is still under construction, prior to application of the surface dressing of tarmac or asphalt, then no such preparatory work is required in order to attach the clamp of the invention.

A further preferred feature of the clamp of the invention is that it is provided with restraining means, which serves to prevent the clamp from falling off the structure whilst it is being installed. The restraining means may comprise, for example, a chain, or a cord of wire or other strong material (e.g. nylon, Kevlar'TM), which can be used to temporarily fasten the clamp to the structure, or to a worker working on the structure. The cord will need to be strong enough to take the weight of the clamp without breaking. Conveniently the clamp may be provided with an aperture, ring or the like, through which the restraining cord may be threaded. The restraining cord may advantageously be provided with a carabiner or the like to allow rapid, reversible, attachment of the cord to another object e.g. to the structure itself, or an existing item of street furniture already anchored on the bridge, or to a belt, safety harness or the like wom by a member of the workforce working on the bridge.

The use of such a restraining system with the clamp of the invention substantially eliminates the risk of the clamp falling off the structure, during installation, onto passers-by below. It may therefore be possible to avoid the need to close is thoroughfares (streets, footpaths, railway lines, cycle tracks etc.) below the structure whilst the temporary additions to the structure are being installed. Even if such closure is necessary for other reasons (e.g. due to the risk of tools or construction materials falling from the structure), the clamps of the invention can be much more rapidly attached than the drilled anchor/plate/post prior art arrangements, and the necessary safety panels therefore installed more rapidly, so that the duration of any closure of thoroughfares below the structure can be briefer than with prior art systems and methods.

Also, because the clamp of the invention can rest on a substantially horizontal surface of the structure, it is inherently less likely to fall from the structure (especially during installation) than a clamping device which attaches vertically to a structure. In addition, in some embodiments, the clamp of the invention is configured such that, when placed approximately in position on the structure (prior to clamping), the centre of mass of the clamp is towards the inner part of the horizontal surface of the structure on which the clamp is resting such that the clamp, if dislodged, will tend to fall inwards onto the structure rather than outwards, off the structure. To facilitate this, it may be desirable that the mounting means is located towards the inner end of the clamp when the clamp is being positioned on the structure, the mass of the mounting means serving to offset the centre of mass of the clamp towards the inner end.

In other embodiments, the centre of mass of the clamp may be towards the outer part of the horizontal surface of the structure on which the clamp rests, especially if the mounting means is located towards the outer end of the clamp. Such embodiments, may not possess the safety feature of tending to fall inwards, described above, but possess other advantages. For example, by providing the mounting means towards, or even at, the outer end of the clamp, more working space is provided on the structure.

This may be very important if the structure is narrow. Additionally, these embodiments may facilitate work being performed on the actual plinth or the like to which the clamp is clamped. In some embodiments, a safety barrier or the like attached to posts or other components mounted on the clamp(s) of the invention may be cantilevered, so that they actually extend outside the structure, to allow maximum is working space on the structure.

A further advantage of the present invention, relative to available prior art systems or methods, is that the clamp and post or other component mounted thereon, can be made stronger than prior art apparatus. In tests on a prototype, the inventor has found that an upright post mounted on a clamp in accordance with the invention can withstand a horizontally applied force of 1.5 kiloNewtons at a height of lm above the base of the post. This allows the system to comply with the requirements of BS EN 13374 for public access to the structure, whilst many conventional prior art systems are strong enough to comply only with the less stringent requirements for access by a temporary workforce, excluding members of the public.

It is a further advantage of the invention that, in preferred embodiments, there are no separate or separable components of the clamp which could fall off during installation, thus reducing the risk to passers-by below the structure whilst the clamp is being installed.

For the avoidance of doubt, it is expressly stated that features of the invention described herein as "preferable", "convenient", "advantageous", "typical" or the like may be present in the invention in isolation or in any combination with any one or more other features so described, unless the context dictates otherwise. Further, features described in relation to one aspect of the invention are applicable to other aspects of the invention, unless the context dictates otherwise.

The invention will now be described in further detail by way of illustrative example, and with reference to the accompanying drawings, in which: Figures 1 and 2 arc perspective views of first and second clamping portions of a one embodiment of a clamp in accordance with the invention; and Figures 3 and 4 are photographs of a second embodiment of a clamp in accordance with the invention, clamped in situ to a concrete plinth at the side of a bridge under construction.

Description of Specific Embodiments

Example 1

Referring to Figures 1 and 2, one embodiment of a clamp in accordance with the present invention comprises a first clamping portion 2, shown in Figure 1, and a second clamping portion 4, shown in Figure 2.

The two clamping portions arc both formed from steel. The clamp is adapted and configured to be clamped to a 500mm wide concrete plinth at the side of a bridge.

The clamp rests on the horizontal upper surface of the plinth and is clamped to the opposed upright sides of the plinth by clamping faces 6 (in Figure 1) and 8 (in Figure 2).

Referring to Figure 1, the first clamping portion 2 has at one end a clamping body 10, which is a section of generally right-angled metal which is intended to be positioned on the outside edge of the plinth. The clamping body 10 has an upper section 12, which rests on the horizontal surface of the plinth, and a downward-projecting side section 14, which is positioned adjacent the outer side of the plinth (e.g. as demonstrated in Figure 3). The clamping face 6 is on the inside of the side section 14.

Attached to the clamping body 10 are two arms 16, one at each side, positioned to extend at least part of the way across the plinth. Each arm 16 is essentially right-angled in section, such that the two arms 16 co-operate to form a partial channel section guide means, within which the second clamping portion 4 may slide, such that the first and second clamping portions are slidably movable relative to one another.

io The upper section 12 of the clamping body 10 is provided with a transverse raised section 18. The raised section has three outwardly extending triangular flanges 20, which serve to strengthen the raised section 18. One such flange 20 is provided at each of the opposed ends of raised section 18, and the third flange 20 is provided in a central portion of the raised section 18.

The raised section 18 is also formed with two circular apertures 22, each of which accommodates a screw-threaded clamping element or bolt, the position of one of which, 24, is indicated by discontinuous lines. The threaded bohs 24 also pass through similar apertures 30 in the second clamping portion 4, as shown in Figure 2, and these bolts form part of a clamping means by which the clamp can apply a clamping force to the plinth.

Finally, Figure 1 also shows a horizontal slot 26 in the side section 14. This slot accommodates a co-operating projecting tongue 28 formed on the second clamping portion 4, and thus provides an additional guide means to guide the relative movement of the two portions, and, more importantly, acts as a moment-resisting means, providing a substantially non-deformable engagement between the two clamping portions, so that the tightening of the bolts 24 in the upper part of the clamp does not cause the upper parts of the clamp to pivot inwards and the bottom of the clamping portions to swing outwards.

Referring now to the second clamping portion shown in Figure 2, the portion comprises a clamping body 32, which is generally horizontal and adapted to extend at least part way across, and rest on, the horizontal surface of the plinth. The clamping body 32 also comprises a downward-projecting side portion 34, generally similar in size and shape to the side portion 14 of the first clamping portion. The clamping face 8 is provided on the inside of the portion 34. The side portion 34 is positioned adjacent the inner side of the plinth, such that the respective clamping faces 6 and 8 can clamp against the opposed upright sides of the plinth.

The clamping body 32 is also provided with a transverse raised section 36, which is substantially a minor image of the raised section 18 provided on the first clamping io portion. The raised section 36 is provided with three strengthening flanges 38, which are triangular in shape. One of these is visible in Figure 2, the position of the other two being denoted by broken lines.

The raised section 36 has two circular apertures 30, as described previously, each of is which accommodates a screw-threaded bolt. The bolts pass through each of the first and second clamping portions, keeping the portions attached. Moreover, by tightening nuts located on the bolts, to a desired torque (as measured by a torque meter, if desired), the appropriate clamping force can be applied to the plinth.

Finally, clamping body 32 is provided with a mounting means, in the form of an upstanding tubular collar 40. Into the collar can be inserted the end of a post (not shown) of conventional design. If desired, the collar 40 can be equipped with fixing means, such as one or more apertures to accommodate respective bolts attached to or passing through the post, and/or spring-mounted dctcnts or the like (provided either on the post, or on the collar), which engage with co-operating recesses.

Typically, a plurality of clamps of the sort depicted in Figures 1 & 2 will be attached to the plinth at suitable intervals (e.g. from about 1 metre spacing up to about 3m spacing), and a respective upright post will be mounted on the mounting means of each clamp, and secured to the clamp. A plurality of lengths of safety barrier e.g. of metal railings and/or mesh, may then be securely fastened to the upright posts in any convenient and conventional manner.

Example 2

A second embodiment of a clamp in accordance with the invention is shown in Figures 3 and 4.

Referring to those Figures, a clamp is shown in situ on the concrete plinth of a bridge under construction, from which the action of the clamp and its engagement with the plinth are readily apparent. The mounting means, provided towards the inner end of the clamp, takes the form of a rectangular-shaped projection, on which can be mounted a suitably shaped and dimensioned upright post of conventional design.

Although not clearly visible in the Figures, the rectangular mounting means has a circular aperture formed therein, to accommodate a bolt with which to attach the post to the clamp.

Other embodiments of the invention will of course be apparent to those skilled in the is art.