GB2252806A - Floor deck fixing device - Google Patents

Abstract

A fixing device (16) which can anchor itself in a dovetail formation (14) provided in the underside of a pressed metal docking structure (10) for suspending a pipe 26 or a ceiling, comprises a generally U-shaped device (17) having a base (18) and a pair of side limbs (19) provided with formations (20) engageable with respective side walls (15) of the dovetail formation (14), a threaded rod (22) extending through the opening (21), and an expander member (24) arranged on the threaded rod (22). The movement of the expander member (24) towards the base (18) upon axial movement of the threaded rod (22) is guided by the internally facing sides of the side limbs (19) which also prevent rotation of the expander member (24), and therefore the formations (20) are urged outwards. The rod (22) is moved axially by the nut (23); alternatively, the opening (21) may be screw-threaded. The formations (20) may be extended transversely of the limbs (19) to prevent rocking. <IMAGE>

Description

FLOOR DECK FIXING DEVICE This invention relates to a fixing device for mounting on the underside of floor decking of the type used to support a floor slab of concrete cast thereon, such slab being derived from a concrete mixture poured onto the decking which forms a mould for the underside of the slab and which also forms a component part of the slab upon setting of the latter.

Floor decking of this type is used in the formation of floor slabs in multi-storey buildings, and is usually made of galvanised steel sheet pressed into a corrugated form for strength. The decking has a dual purpose, in that it forms a mould for the poured concrete mixture and which must therefore be able to bear the load of the poured concrete without flexing, but which also forms a component part of the floor structure upon setting of the cast concrete slab.

The decking therefore is exposed on the underside of the cast concrete slab, and can form a support for a ceiling or other structure to be suspended below the floor slab. In addition to supporting the ceiling structure, it is often necessary to suspend overhead pipes, especially of a fire prevention sprinkler system, and also electrical conduits, and at present such items are usually suspended via "pipe hangers" and threaded rods which are anchored at their upper ends to suitable anchorages provided in the decking.

The decking therefore usually is provided with laterally spaced shallow trough shaped formations which extend throughout the length of the decking to permit anchorage to be made of suspended fittings at any required positions along the length of the formations.

The formations are shaped somewhat in the manner of a "dovetail joint", into which wedge shaped devices can be installed, from which any required fittings can be suspended. In one existing form, the wedge shaped device has an external profile which corresponds approximately with the design profile of the dovetail formation, and is presented to this formation with the longitudinal axis of the wedge extending generally along the length of the formation, but is then rotated through 900 so as to bring the two opposed ends of the wedge into engagement with respective side walls of the dovetail formation.

These existing wedge members operate satisfactorily when the production versions of the dovetail formations correspond substantially with the design profile. However, the dovetail formations are of shallow depth (typically about 1cam) and have short side walls which diverge as they approach the base of the formation, and therefore in practice the formation can deviate substantially from the ideal design profile.

This is not surprising, in that the entire decking profile is stamped or pressed from a single sheet, and the major deformation which takes place comprises the formation of laterally spaced channels of substantial size which extend parallel to each other throughout the length of the decking, whereas the dovetail formations (for supporting suspended items) are formed in the bases of these channels and have a width which is about a quarter of the width of the channels and a depth which is about one seventh of the depth of the channels.Therefore, in practice there are certain permitted tolerances in the formation of the relatively large channels which will be acceptable, but the same tolerances necessarily applied in the formation of the dovetail formations will have a proportionally greater effect, and can often result in the formation of side walls of the dovetail formations which do not diverge to a sufficient extent to provide reliable anchorage of the existing wedge shaped devices i.e. the dovetail profile in practice does not correspond with sufficient closeness to the ideal design profile, and of course the wedges are manufactured with profiles to suit this ideal design profile.

Also, in such a situation, upon rotation of the wedge shaped devices to anchor them in position, they will tend to make line or point contact with the walls of the dovetail formation, which will apply very substantial contact pressure which will be liable to damage or tear the material from which the side walls are made.

Clearly, it is unsatisfactory to have unreliable anchorage of the wedge shaped devices in the dovetail formations, and especially when heavy items are to be suspended overhead, such as water pipes of a fire prevention sprinkler system. Further, when there is an unsatisfactory dovetail profile in which a wedge shaped device is force fitted by operators not acting with required degrees of skill and attention, the wedge may take-up an apparently reliable anchored position from which it can subsequently fall out under load e.g. by tearing through or otherwise deforming the thin walls of the dovetail formation. Alternatively, the act of force fitting of the existing devices may provide an initially reliable anchorage, but which subsequently fails in service because of corrosion effects.Thus, the decking is usually galvanised, but force fitting of the existing devices can easily remove the protective surface coating and which then sets-up sites in which rapid corrosion will take place.

Therefore, while the existing wedges can perform reliably when the decking is manufactured to sufficiently high standards of minimum tolerance, in practice any structure suspended from the decking by such devices may not be able to perform to required safety standards, and especially in a case of the high safety standards set for fire prevention sprinkler systems.

The invention therefore seeks to provide an improved design of fixing device which can anchor itself more reliably in a dovetail formation than the existing devices.

According to the invention there is provided a fixing device which can anchor itself in a dovetail formation provided in the underside of a pressed metal decking structure for supporting a concrete floor slab cast thereon, said device comprising: a generally U-shaped anchoring device having a base and a pair of side limbs upstanding from the base; a pair of wedges arranged one at each end of each of said limbs, with each wedge being engageable with a respective side wall of the dovetail formation; an opening formed in said base; a rod to be taken through said opening; a wedge member to be mounted on said threaded rod; and, guides provided on the internally facing sides of said limbs to engage the wedge member and prevent its rotation, and also arranged to guide the movement of the wedge member towards the base upon axial movement of the threaded rod in one direction, whereby to apply an outward force to each of the limbs in order to press the wedges firmly into engagement with the respective side walls of the dovetail formation.

Therefore, in use of the fixing device of the invention, the wedges can be adjusted to fit tightly in the dovetail formation, by suitable axial adjustment of the rod, and even if the dovetail formation has an irregular shape or departs from an ideal design profile.

Also, by virtue of the outward movement of the wedges into area contact with the side walls of the dovetail formation (rather than point or line contact as with the existing wedge shaped devices), there is reduced risk of tearing or unacceptable damage being done to the material of each side wall.

In practice, there will be concrete filling located around the side walls and the base of each dovetail formation, and this will provide solid support for the formation, while allowing small movement of the component parts of the formation to take place in order to take-up any clearances under the action of the moving wedges.

The fixing device therefore can have a reliable anchoring in position even in poorly formed dovetail formations, and the device will-be able to meet any necessary building standards, and particularly the higher safety standards applied to fire prevention sprinkler systems.

In one preferred arrangement, the rod is a threaded rod and the wedge member is internally threaded to fit on one end of the rod. The axial movement of the rod may be achieved by any convenient means, such as rotation of the rod in a threaded opening in the base of the anchoring device, but preferably by the provision of a plain oversized opening in the base, and a nut fitting on the rod and tightened against the base in order to draw the rod through the opening.

Preferably, each wedge forms an integral part of its respective side limb, and conveniently this is achieved by making the entire anchoring device of one piece construction with the side limbs (plus wedges) and the base being integrally connected together.

In use, the wedges move outwardly under the action of the wedge member, and this is permitted by slight flexing movement of each side limb about a region of connection to the base. Therefore, the anchoring device will be made of any suitable strong, but resiliently deformable material.

One preferred material is malleable iron.

The rod may be threaded throughout its length, with the wedge member fitted on one end (on one side of the base), and the nut applied to the opposite end (which projects from the opposite side of the base) and this nut can be tightened in a direction towards the base in order to cause the wedge member to be drawn towards the base while moving within the guides.

The wedge member may comprise a trapezoidal section nut (as seen in side view), and the guides may comprise channels formed in the facing sides of the side limbs to receive and to guide slidable movement of the respective end faces of the trapezoidal nut.

Any required structure can be suspended from the decking by being fastened to the lower ends of each of the threaded rods e.g. a length of pipe and sprinklers can be suspended from a run of fixing devices by suitable "pipe hangers" fastened to the lower ends of the threaded rods.

Preferably, the side limbs and the respective wedges are of substantially uniform width throughout their lengths (when viewed in end view). However, to minimise any tendency for the wedges to rock in a sideways direction when initially installed and prior to anchoring, it may be advantageous for side shoulders to be provided on the wedges, which can take up any clearances.

One embodiment of fixing device according to the invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic illustration of floor decking of the type used to support a floor slab of concrete cast thereon, and from which a fixing device according to the invention can be securely anchored:: Figure la is a detail view of a part of the decking shown in Figure 1, and illustrating a typical deviation from an ideal design profile which can occur in practice during pressing of the decking from sheet metal; Figure 2 is a diagrammatic illustration of an embodiment of fixing device according to the invention, in partly assembled form; Figure 3 is a sectional view, taken on the section line A-A in Figure 5, of a generally U-shaped anchoring device forming part of a fixing device according to the invention; Figure 4 is a top plan view of the anchoring device shown in in Figure 3; Figure 5 is an under plan view of the anchoring device showin in Figure 3; Figure 6 is an end view of the device shown in Figure 3; and, Figure 7a to 7c show consecutive stages in the installation of the device in a dovetail formation of a piece of floor decking.

Referring now first to Figures 1 and la of the drawings, this shows a typical design of an existing construction of floor decking which is designated generally by reference 10, and of a type used to support a floor slab of concrete cast thereon, the slab being derived from a concrete mixture poured onto the decking 10 which forms a mould for the underside of the cast slab, and which also forms a component part of the slab upon setting of the latter. In Figure 1, there is shown part of a concrete slab 11 which has been cast onto the decking 10.

The decking 10 is usually made of galvanised steel sheet, which is pressed into corrugated form comprising a series of laterally spaced inverted channels 12, which run the length of the decking, and in which the base 13 of each channel 12 is formed with a dovetail formation 14. The purpose of the dovetail formation 14 is to serve as a means by which any fixing devices can be anchored therein, to enable any required structures, such as a ceiling structure, or an overhead pipe run of a fire prevention sprinkler system, to be suspended therefrom.

Figure 1 shows an ideal design profile of a typical piece of floor decking 10, and it will be noted that the depth and also the width of the dovetail formations 14 are substantially smaller than the corresponding dimensions of the channel 12, in the base 13 of which it is formed.

Typically, the height or depth of channel 12 is about 7cm, and the corresponding dimension of formation 14 is 1cam, whereas the respective widths might be 20cm and 6cm.

Therefore, while it is readily possible to press out the channels 12 from the general plane of the steel sheet to acceptable tolerances, the same tolerances applied proportionally in the formation of the dovetail formations 14 can result in unacceptable deviations from the ideal design profile. Figure la shows a detailed example of what could be an unacceptable deformation of a dovetail formation designated by reference 14a. Thus, in the manufacture of existing designs of wedge shaped fixing devices for anchorage in the dovetail formations 14, the ideal design profile of the formations 14 are taken and used in corresponding shaping of the outer profile of the wedge shaped device.The existing device will normally be presented lengthwise-on to each formation 14, to allow it to enter the formation, and is then rotated through 900 to bring the two opposed wedging ends of the wedge shaped member into engagement with the opposed side walls 15 of the formation 14. This provides a satisfactory anchorage, when there is an idea profile of the formation 14, as shown in Figure 1. However, in the event of unacceptable deviation from the norm, as shown for formation 14a in Figure la, there is a risk that the rotation of the wedge shaped device will tear, unacceptably deform and / or abrade the surface of the side walls 15a. This results in improper anchorage in position of the fixing device, and when there is surface damage or tearing, this also creates sites at which corrosion can take place, which will cause the anchorage to become further unreliable over a period of time.

The major problem involved with the existing wedge shaped devices, which are secured in position by simple rotation, is that there tends to be line or point contact with the side walls 15a, which raises the bearing pressure to very high levels, with resultant risk of unacceptable damage being done.

The present invention has been developed primarily, though not exclusively, with a view to providing an improved form of fixing device which addresses this problem which arises in connection with the type of floor decking described herein.

Referring now to Figure 2 of the drawings, this shows, in partly assembled form, one embodiment of fixing device according to the invention which is designated generally by reference 16. The device 16 comprises a generally U-shaped anchoring device 17 having a base 18 and a pair of side limbs 19 upstanding from the base 18. A pair of wedges 20 is provided, each engageable with a respective one of the side walls 15 of the dovetail formation 14, and each being arranged at one end of a respective one of the limbs 19. A plain wall opening 21 is formed in the base 18, and a threaded rod 22 is taken through the opening 21, with a nut 23 arranged on the lower end of the threaded rod 22, and an internally threaded wedge member 24 arranged on the upper end of the rod 22.

Figure 2 shows a longitudinal sectional view of the anchoring device 16, but its constructional details are shown in more detail in Figures 3 to 6 which are described below. In particular, as will be apparent from the subsequent description, guides are provided on the internally facing sides of the limbs 19 to engage the wedge member 24 and to prevent its rotation, such guides also serving to guide the movement of the wedge member 24 towards the base 18 upon axial downward movement of the threaded rod 22 in one direction. By virtue of the freestanding arrangement of the side limbs 19, and of the guides, downward movement of the wedge member 24 is accompanied by outward movement of the wedges 20 which are thereby moved firmly into engagement with the respective side walls 15 of the dovetail formation 14, even in the event of the formation 14 being poorly formed i.e.

deviating appreciably from an ideal design profile to retain a wedge shaped member.

The outward movement of the wedges 20 is permitted by resilient movement of the limbs 19 about a general region of connection with base 18, and therefore the engaging faces 25 of the wedges 20 tend to make area contact with the facing surfaces of the side walls 15 (15a) of the formation 14, and therefore a relatively gentle gripping engagement takes place without any localised high pressure.

The engaging surfaces 25 can cause any necessary minor yielding of the side walls 15 (15a) to take-up any voids which may be present in the cast concrete surrounding each formation 14, or possibly accompanied by minor crumbling of the concrete, until a firm anchorage of the fixing device is achieved.

This enables a much more predictable safe load to be determined, which can meet any required safety standards.

The anchoring device 17 is of one piece construction, with the side limbs 19 (plus wedges 20) and the base 18 being integrally connected together. The preferred material from which the device 17 is made is malleable iron, which is sufficiently strong, but also resiliently deformable to allow any necessary flexing of the side limbs 19.

Any required structure may be suspended below the decking 10 via a series of fixing devices 16, and Figures 1 and 2 show schematically, by way of example only, the support of an overhead pipe 26 (which may form part of a fire prevention sprikler system) via any suitable design of "pipe hanger" (not shown) which is fastened to the lower end of threaded rod 22, or of which threaded rod 22 may form a component part.

The wedge member 24 comprises an internally threaded nut which is trapezoidal in cross section, as seen in side view in Figure 2, and which is rectangular, as seen in top plan or under plan, so as to be capable of fitting within a rectangular opening 27 (see Figures 4 and 5) formed in the upper flared ends of the side limbs 19. The rectangular opening 27 forms the entrance to a guide passage defined between the facing sides 28 of the side limbs 19 and provided by channel shaped guide surfaces. The purpose of the guides is to prevent rotation of wedge member 24 as it moves downwardly, and also to guide the slidable movement of the wedge member 24, upon downward movement of the threaded rod 22 through opening 21.

The nut 23 will be tightened until it bears against the underside of base 18, and then continued rotation of the nut 23 causes the wedge member 24 to move axially downwardly with the rod 22, while being guided by the guides 28.

Figures 2 and 3 show the profile of the wedges 20, as seen in front or rear view, whereas Figure 6 shows the side limbs 19 end-on. It can be seen therefore from Figure 6 that each wedge 20 also extends laterally to form a shoulder 29, and this is an optional additional feature, which will serve to restrict any tendency for the device to rock sideways upon initial installation and prior to anchorage in position.

Figures 7a to 7c show consecutive stages in the assembly of the device 16 in a dovetail formation 30 of a length of decking 31.

Claims (11)

1. A fixing device which can anchor itself in a dovetail formation provided in the underside of a pressed metal decking structure for supporting a concrete floor slab cast thereon. said device comprising: a generally U-shaped anchoring device having a base and a pair of side limbs upstanding from the base; a pair of wedges arranged one at each end of each of said limbs, with each wedge being engageable with a respective side wall of the dovetail formation; an opening formed in said base; a rod to be taken through said opening: a wedge member to be mounted on said threaded rod; and guides provided on the internally facing sides of said limbs to engage the wedge member and prevent its rotation, and also arranged to guide the movement of the wedge member towards the base upon axial movement of the threaded rod in one direction, whereby to apply an outward force to each of the limbs in order to press the wedges firmly into engagement with the respective side walls of the dovetail formation.

2. A fixing device according to Claim 1, in which the rod is a threaded rod and the wedge member is internally threaded to fit on one end of the rod.

3. A fixing device according to Claim 2, in which the rod is mounted for rotation in a threaded opening in the base of the anchoring device.

4. A fixing device according to Claim 2, in which the rod is taken through a plain oversized opening in the base, and a nut fits on the threaded end of the rod and is tiglitenable against the base in order to draw the rod through the opening.

5. A fixing device according to any one of Claims 1 to 4, in which each wedge forms an integral part of its respective side limb.

6. A fixing device according to Claim 5, in which the entire anchoring device is of one piece construction with the side limbs and wedges and the base being integrally connected together.

7. A fixing device according to Claim 1, in which the rod is threaded throughout its length. with the wedge member being fitted on one end, and a nut applied to the opposite end, said nut being tightenable in a direction towards the base in order to cause the wedge member to be drawn towards the base while moving within the guide.

8. A fixing device according to any one of Claims 1 to 7, in which said wedge member comprises a trapezoidal section nut, and the guides comprise channels formed in the facing sides of the side limbs to receive and to guide slidable movement of the respective end faces of the trapezoidal nut.

9. A fixing device according to any one of Claims 1 to 8, in which the side limbs and the respective wedges are of substantially uniform width throughout their length, when viewed in end view.

10. A fixing device according to Claim 9, in which side shoulders are provided on the wedges, to take up any clearances and thereby minimise any tendancy for the wedges to rock in a sideways direction when initially installed and prior to anchoring.

11. A fixing device according to Claim 1 and substantially as hereinbefore described with reference to, and as shown in the accompanying drawings.