GB2275725A

GB2275725A - Scaffold fitting to expansion anchor connecting method

Info

Publication number: GB2275725A
Application number: GB9304223A
Authority: GB
Inventors: Philip John Rendle
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-03-02
Filing date: 1993-03-02
Publication date: 1994-09-07
Anticipated expiration: 2013-03-02
Also published as: GB9304223D0; GB2275725B

Abstract

A scaffold fitting has a body 3 with a large base and an aperture 8 into which is fitted load transmitting members 9, 22 which also fit into holes 14, 23 in a structure together with expansion anchor means 16, 18 actuated by rotation of a screw thread 13, and 19. In one embodiment, in Fig. 1, the screw thread is a headed bolt passing through the load transmitting sleeve 9 from inside the fitting body 3 and expanding the split shell 16 when it is turned by drawing the cone 17 upwards and at the same time pulling the body 3 down onto the surface 2 of the structure. In another embodiment, in Fig. 2, the screw thread is provided on an extension 19 of the load transmitting boss 22. The head of the boss 22 is shaped (eg hexagonal) to fit into the aperture of the fitting 3, which is correspondingly shaped. A bolt 29 threads into the top of the boss 22 to attach it to the fitting. In order to expand the expansion fitting 18, the whole assembly, including the fitting, is rotated. <IMAGE>

Description

SCAFFOLD FITTING to ANCHOR CONNECTION METHOD This invention relates to a method and apparatus for connecting a scaffold tie fitting to a variety of anchors used to fix the tie fitting to the face of a structure, such as a building.

This invention leads to an improved fitting to that shown in my published UK Patent Application No. GB 2 254 367 A.

There are many scaffold fittings for connecting a scaffold tie tube to a structure. There are also many proprietary anchors for inserting into holes in the structure to provide a temporary means of connecting the tie fitting and hence the scaffold to the face of the structure for the duration of the temporary scaffold structure.

The scaffold tie fittings should ideally be capable of resisting and transmitting to the anchor both tensile loads, in a direction perpendicular to the face of the structure, and lateral loads parallel to the face of the structure; together with any combinations of these acting in either direction. Lateral loads in scaffold tie fittings frequently reverse in direction from push to pull - for instance, the loads in the scaffold tubes tying in a hoist reverse from tension to compression every time the hoist cage passes the tying position.

The anchors also need to be capable of transmitting all the above loads to the structure. The tensile loads are normally resisted by an expanding wedge or expanding sleeve in intimate contact with the side of the hole in which the anchor device is located. The lateral loads are normally transmitted by a close fitting sleeve or boss in contact with the side of the hole in the structure.

For the scaffold tie fitting to provide a rigid connection of the scaffold to the structure, the load transmitting sleeve or boss of the anchor needs to be as tight a fit in the hole as the tolerances of drilling a hole in a brick or concrete structure permit. The sleeve also has to be a snug fit in the aperture in the base of the fitting in order to resist the reversing loads without appreciable movements.

An object of this invention is to provide a method of connecting the scaffold fitting part with various different expansion anchor and sleeve means.

According to one aspect of the invention the scaffold fitting part comprises a base part having a flat or substantially flat exterior surface with the central section slightly domed, away from the structure, and with an aperture therein for engagement of the body with the sleeve or force transmitting part of the anchor.

According to another aspect of the invention a domed washer is fitted within the body of the scaffold fitting.

When the loads to be anchored are large, the use of a proprietary Heavy Duty anchor is necessary. One typical type is shown in use in Figure 1. This has a heavy duty split expansion sleeve and conical wedge means located deep in the structure to resist the tensile loads. The lateral loads are transmitted to the sides of the drilled hole by means of a thick wall tube or sleeve of cylindrical form. The aperture in the base of the fitting is required to be circular in shape to engage with the end of the cylindrical load transmitting means.

The anchor is tightened by a long bolt, contained within the cylindrical force transmitting sleeve, with a head and washer in contact with the inside surface of the fitting base. At the bottom end of the bolt, a thread engages with an internal thread of a conical wedge. Turning the bolt pulls the conical wedge upwards into the split sleeve causing it to expand radially outwards giving a good fixing to the side of the hole.

When the loads to be anchored are not large, or even nominal, they can be resisted by an expansion anchor in the form of a sleeve of chloroprene rubber which is expanded against the inside of the hole in the structure. The rubber sleeve is expanded by turning a threaded bolt which is an integral part of a cylindrical boss.

The bolt thread engages with a metallic insert fitted at the bottom end of the rubber sleeve so that, by turning the bolt, the insert is pulled upwards so compressing the rubber sleeve causing it to move radially outwardly, as shown in Figure 2, to fix the anchor tightly in the hole.

The boss engages with the side of the hole in the structure to resist lateral loads. The boss has to engage with the aperture in the base of the fitting. The centre of the boss is drilled and tapped with a female thread into which a short set screw is fitted the head of which, with a washer, engages with the inside surface of the base of the fitting.

The rubber sleeved anchor is a proprietary anchoring device that is used to provide an anchorage for other proprietary fittings for instance a ringbolt which has a threaded end to engage into the female thread in the end of the boss. In this use, the boss needs to project proud of the face of the structure and be provided with a shaped external face to enable a spanner to be used to tighten and slacken the anchor. Obviously it is this shaped external face that engages with the aperture in the base of the fitting.

This invention has overcome the problems of engaging a variety of shaped members in the aperture in the base of the fitting and provide a load transmitting connection for lateral loads from the fitting into the various shaped force transmitting members.

Additionally, by making the shaped head of the boss of the rubber sleeve anchor bolt fit into a shaped aperture in the base of the fiting, the boss and the long bolt which is integral with it, can be turned by rotating the fitting without need for socket spanners or for removing the scaffold tube fixed in the fitting - thus tightening or loosening the rubber anchor.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a part sectional view of a scaffold fitting, with a scaffold tie tube shown secured thereto and a heavy duty proprietary anchor shown with the split sleeve expanded in a bore in a surface of a structure to which the fitting is thus fixed; Figure 2 is a similar part sectional view but with a normal duty anchor with a chloroprene rubber sleeve shown expanded to fix it in a bore in a surface; Figure 3 is a plan detail of the shaped aperture in the base of the fitting with the top of the cylindrical boss of the normal duty "rubber sleeve" anchor machined to form a square head; Figure 4 is a similar plan detail but with the top of the cylindrical boss machined to a hexagonal shape.

Figures 1 and 2 show a scaffold fiting securing a scaffold tube 1 parallel to a flat or generally flat surface 2 of a wall or floor of a building or the like. The fitting has a body part 3 and a cover part 4 which is tightened in the conventional way.

The body part of the fitting 3, to which my UK Patent Application refers, is formed with upwardly converging sides 4 so that the base 5 of the fitting is enlarged compared to a conventional scaffold clamp. The base has inner and lower surfaces 6 & 7 resfectively.

The base can be flat but in the example shown, the centre is domed upwards away from the surface 2 of the structure. The base has an aperature 8, centrally positioned.

In Figure 1 the load transmitting member 9 of a Heavy Duty proprietary anchor is shown passing through the aperture 8. The anchor shown and described is a Hilti HSL anchor. The aparture 8 could be designed to fit a number from several fixings manufacturers

of proprietary anchors available s Z ;s X t T iSbb;zz In the Figure 1 embodyment, the bolt 10 has a head 11 which is larger than the aperture 8 and which, via a thick flat washer 12 bears against the inner surface 6 of the body 3. A screw-threaded stem 13 extends through aperture 8 and out of the base of the fitting. Around the bolt stem 10 the thick walled cylindrical load transmitting member 9 is positioned. One end is a relatively snug fit in aperture 8 to transmit lateral loads from the body 3 to tube 9. However, the fit can be loose enough to accommodate angular movement to permit minor inaccuracy of the drilling of hole 14 in the structure. The inner end of load transmitting tube 9 abuts the underside of washer 12 and is a sliding fit on bolt stem 10.

Fitted on the bolt 10 against the outer end of tube 9, remote from the washer 12, is a collar of plastic material 15 its external surface has small fins to engage with the side of the hole to prevent rotational movement and its end remote from the tube 9 being configurated so as to engage with the narrow end of the split, expansion shell or sleeve 16 and prevent relative rotation during expansion. The threaded stem of bolt 13 extends through both the collar 15, the split sleeve 16 and complementary internally threaded expansion member 17 which is in the form of a frusto-conical plug.

The anchor parts are assembled on the base of the fitting, bolt being inserted through the aperture 8 and the remainder threaded onto the stem with the expansion member finally being screwed into place loosely. The anchor assembly is then located into the hole.

The bolt 10 is tightened with a torque socket on head 11 with the cap 4 open and scaffold tube 1 not yet fitted. This tightening with the lower surface of the base 7 in contact with surface 2, causes the cone 17 to be drawn inwardly of the split sleeve 16 on the bolt stem. This movement causes a splaying of the split sleeve 16, such expansion of the sleeve 16 securely engaging the outwardly extending parts of the shell with the side of the hole 15 and fixing the anchor in place. The same tightening force in the bolt stem 10 pulls the body of the fitting down. Tightening the bolt 10 with a torque wrench further pulls and tightens surface of base 7 onto surface 2 of the structure - enhancing the rigidity of the assembly in use and improving its load bearing characteristics, especially with respect to lateral loads.

In addition to the resistance to lateral loads due to friction between the body base 7 and the surface 2 of the structure, the thick walled tube 9 acts as a force (shear) transmitting member.

The loads are transmitted by the tube 9 to the side of the hole 14 in the structure. The lateral loads from the scaffold tie tube 10 are transmitted by the body 3 to the thick walled tube 9 by bearing of the aperature 8 against the side of the tube 9. Hence to resist movements from oscillating or reversing loads the shape of the aperture 8 needs to be circular and a snug fit around the tubular sleeve 9. For the magnitude of loads for which the fitting will be used, the thick walled sleeve 9 will be in the order of 18mm diameter - this being determined by the split anchor 16 in the bore to resist tensile forces on the anchor.

Figure 2 shows the fitting used with an anchor more suited to smaller loads normally associated with tying in scaffolds. The body of the fitting is as previously described with an aperture 8 in the base of the fitting.

The anchor in this example has a chloroprene rubber sleeve 18 which is spaced radially outwardly of the bolt thread 19. The rubber sleeve 18 has a metallic insert sleeve 20 fitted in its outer end, this insert providing an internal screw thread which is complementary with the thread on bolt 19. Preferrably a short metallic locator sleeve 21, which is not internally threaded, is part of the rubber sleeve 18 at its internal end.

The bolt part 19 is an integral part with the boss part 22 which is the same diameter as the rubber sleeve 18 so that it fits into the hole 23 drilled into the face 2 of the structure to transmit lateral loads into the structure.

The usual design for this type of anchor for use with say, a ringbolt has the boss 22 and the bolt 19 machined from a length of 20 AF hexagonal bar. The portion of the anchor projecting above the surface 2 normally remains as a 20mm hexagon to provide means for tightening and slackening the anchor. In normal use, the sleeves 18, 20 & 21 are threaded onto bolt 19 with sleeve 21 touching the bottom of boss 22. The assembly is then inserted into bore 23 until the larger hexagon head (not shown) is just proud of the surface. The hex. head is tightened with a spanner causing threaded sleeve 20 to move towards the boss 22 and the rubber sleeve 18 to be compressed and expand radially outwards so as to fix the anchor assembly tight in the bore 23.The normal anchor has the end of the boss 22 remote from the bolt 19 drilled and tapped to receive a fitting, for instance, a ringbolt.

Acccording to this invention, the boss 22 and bolt 19 are machined from a 20mm diameter bar - this size being determined by the diameter of the rubber sleeve 18 to make a practical anchorage in bore 23. The end of the boss 22 remote from bolt 19 is machined to form a shape 24 which could be used to attach a spanner to tighten the anchor. The shape 24 shown in Fig.2 is a square but a hexagon shape or a triangular shape could be machined.

The shaped end 24 on the boss 22 is engaged in the aperture 8 with a reasonably snug fit to transmit lateral loads from the fitting 3 to the boss 22 and hence to the side of thee hole 23 in the structure. The fit of the shaped end 24 needs to have some tolerance in aperature 8 to allow for bore 23 to be drilled not quite square to surface 2.

Figure 3 is an enlarged plan detail of aperture 8 in the base of fitting 3 with the top of the anchor boss 22 machined square shown in place 24. The aperture is formed from an inital circular hole 25 of the required diameter to fit over sleeve 9 shown in Fig. 1.

The square shape 24 machined in the top of boss 22 in Fig. 2 is shown. The corners of the square 26 are the original size of boss 22 but could be machined smaller if required. The corners 26 of the square 24 are housed in the aperture 8 by punching four 4mm radii shapes 27 at 90 degrees around the circumference of the circular hole 25. Central in the square top 24 is a drilled and tapped hole 28 for the fixing screw bolt 29.

It is obvious that the square shank 24 can not turn in the aperture 8 due to being housed in the punched shapes 27. Hence the anchor expanding bolt 19 can be turned by just turning the fitting body 3. Also, as the size of the boss 22 is larger than the circular aperture 25, once the screw bolt 29 is fixed, the anchor assembly is captive on the base of the fitting 3. This means that the anchor and fitting assembly can be moved between uses on site as a single unit with the benefits claimed in the original UK Patent Application.

In Figure 4 the plan of the aperture 8 is also shown to an enlarged scale with the top of the machined boss 22 shown. In this embodyment of the invention, the top of boss 22 has been machined to a hexagon shape 30 which is just a little smaller than the original circular hole 25 required for the sleeve 9 of the anchor shown in Fig. 1. The corners 31 of the hex. shape 30 machined from the 20mm diameter boss 22 are machined to a smaller diameter to fit into the six 4mm radii shapes 32 punched around the circular aperture 25 at 60 degree spacings. Once again it is obvious from Fig.4 that the hex shape 30 can not turn in the shaped aperture 8. The tapped hole 28 for the fixing screw bolt 29 is also shown in Fig. 4.

Some of the commercial advantages of a scaffold fitting as described and claimed by this invention are considered to be: (A) The scaffold body 3 with the shaped aperture 8 can be used with either a "normal duty" anchor with a reuseable rubber sleeve or with a choice of various "heavy duty" anchors comprising loose load transmitting sleeves which, with the bolt & washer are recoverable but the expanding shell remains with the cone deep in the structure - only one type of fitting needs to be stocked.

(B) With either type of anchor, the bore in the structure is free of metal parts near the surface and can be made good with no risk of rust stains.

(C) The initial cost of the new anchor with the rubber sleeve will be more expensive than anchors like, say, the Hilti HKD which is usually used to tie in scaffolds. However, if the benefits are costed, the reusable anchor will in the long run be cheaper.

(D) Also, in the "normal" mode, it will be a more reliable fixing as it does not have the same potential for misuse and incorrect setting - not requiring a special punch and a hammer which scaffolders do not normally carry - only a scaffold key is required. With the HD anchors, there is a need, as with every anchor of this type for the bolt to be tightend with a torque spanner.

(D) The labour cost of fixing the new "normal duty" assembly, which is removed and refixed as a single unit, is less than fixing separate anchors and tie fixings. Also, as there are no loose parts, safety on site when erecting and dismantling the scaffold will be enhanced - a difficult item to cost but certainly a benefit.

With either anchor type, the fitting is particularly advantageous compared with current commonly used fittings as its strength, particularly with the resistance to lateral loads and reversing loads, is far superior. It will be the natural choice of specialist Designers to comply with the requirements of the latest Code for sheeted temporary structures.

Claims

1. A method of connecting a metal member, in this instance a scaffold fitting having a base with an aperture, to a force transmitting member extending from said base to terminate at an end spaced therefrom with thread means to engage with expansion anchor means and part of said force transmitting member being within said aperture.

2. A method as claimed in Claim 1, wherein the force transmitting member extends normally or substantially normally from the exterior surface of the base.

3. A method as in Claims 1 & 2 wherein the force transmitting member is engaged within the aperture to resist lateral forces from the sides of the aperture.

4. A method as in Claim 3 wherein the force transmitting member remote from the base is contained within a hole or bore in a structure to transmit said lateral forces to the structure.

5. A method as in the previous Claims wherein a shank of a headed screw extends through said aperture.

6. A method as in Claims 3, 4 & 5 wherein the load transmitting member is a boss threadedly engaged with the shank of the headed screw as shown in Figure 2.

7. A method as in previous Claims wherein a bolt extends nonrotatably from the boss, the bolt terminating at a free end from which a screw-thread extends along the bolt towards said boss.

8. A method as in Claim 1 wherein the expansion anchor means is a sleeve which is internally screw-threaded complementary with the screw-thread on the bolt so that it can be screwed thereon until its leading edge abuts the boss, further relative rotation between the sleeve and the bolt causing compression of the sleeve with consequent outward expansion thereof resulting in a tight fix between the anchor and the side of the bore to transmit tensile loads from the headed screw into the structure.

9. A method as in Claim 3 wherein that portion of the boss that is within the aperture is formed by machining the boss to produce a shape the corners of which engage with complementary shapes formed in the aperature to resist relative rotational motion.

10. A method as in Claim 9 wherein the shape is in the form of a square.

11. A method as in Claim 9 wherein the shape is in the form of a hexagon or other geometric shape.

12. A method as in the previous Claims wherein the corners of the geometric shapes have their points machined to provide a better fit in the complementary shapes formed in the aperature.

13. A method wherein the rotational motion in Claim 8 is produced by turning the body of the scaffold fitting, said turning motion being transmitted to the boss and bolt by the complementary shapes in Claim 9.

14. A method as in Claim 1 wherein the load transmitting member is a thick walled tube.

15. A method as in Claim 5 & Claim 14 wherein the shank of the headed screw passes through the tube, the shank below the end of said tubular member being threaded to engage with an internally threaded expansion member having a frusto-conical outer surface said expansion member being received within a split expansion sleeve or cone, so that movement of the expansion member along the thread by turning the head of the screw within the body of the scaffold fitting in one direction causes a splaying out of the expansion sleeve or cone resulting in a tight fix between the anchor and the side of the bore in the structure.

16. A method as in Claim 15 wherein the anchor resists tensile forces from the headed screw and transmits said tensile forces to the structure.

16. A method as in Claims 4 & 14 wherein the thick walled. tube fits within the bore in the structure to transmit lateral forces from the scaffold fitting to the structure.

17. A method as in Claim 3 wherein the outer cylindrical surface of the load transmitting member engages with the circular parts of the aperture to resist lateral loads from the sides of the aperture.

18. A method as in Claim 5 wherein there is a domed washer fixed within the body of the fitting having a hole therethrough aligned with the aperture in said base with the shank of the threaded bolt passing through said hole and said aperture.

19. A method as in Claim 1 wherein the force transmitting members are cylindrical shapes with different diameters required to fit in the bores in the structure to transmit lateral loads, said bore diameters being determined by the requirements of the expanding anchors to enable the expansion to give a good fixing to resist movement of said expanding anchor along the surface of said bore to transmit tensile loads.

20. A method as in Claim 8 wherein the expanding sleeve is made of chloroprene rubber or similar material which can be reused several times.

21. A method as in Claim 2 wherein the tolerances of the fit of the load transmitting member within the aperture permits the normal inaccuracy of boring a hole in a structure.

22. A method as in Claim 21 wherein the domed shape of the base or the domed washer within the fitting gives a good seating for the headed bolt and its washer.

23. A method of securing to a surface of a structure a scaffolding fitting comprising the steps of providing a hole in said surface, inserting said expansion anchor means and the part of said force transmitting means extending from said external surface of the base of the scaffold fitting into said hole so that said external surface of the fitting is in contact with said surface of the structure, and rotating said thread means thereby to cause expansion in said hole of an of an expandable part of said expansion anchor means and tightly secure the fitting to the surface of the structure.

24. A method wherein the lateral loads from the fiting are transmitted by the aperture in the base of said fitting into said load transmitting member and by it into the structure by bearing against the side of the bore in said structure.

25. A method wherein the shape of said aperture in said base is engineered to provide a load transmitting fit for said load transmitting members of varying diameters.

26. A method as claimed on Claim 23 wherein rotation of the thread means is produced by rotating the fitting.

27. A method wherein the top of the boss is retained within the aperture by the headed stud and the fitting/anchor assembly is handled and moved as a complete unit.

28. A method as claimed in Claim 23 wherein the rotation of the thread means is produced by the rotation of the head of a bolt or screw providing said thread means.

29. An apparatus comprising a scaffold fitting and various load transmitting members and expanding anchors as hereinbefore described, with reference to, and as shown in Figures 1 to 4 of the accompanying drawings.

30. A method of securing to a surface a scaffold fitting substantially as hereinbefore described, with reference to, and as shown in Figures 1 to 4 of the accompanying drawings.

CLAIMS 1. A method of connecting a metal member, in this instance a scaffold fitting having a base with an aperture, to a force transmitting member extending from said base to terminate at an end spaced therefrom with thread means to engage with expansion anchor means and part of said force transmitting member being within said aperture.

10. A method as in Claim 9 wherein the shape is in the form of a square.

11. A method as in Claim 9 wherein the shape is in the form of a hexagon or other geometric shape or a spline.

12. A method as in the previous Claims wherein the corners of the geometric shapes have their points machined to provide a better fit in the complementary shapes formed in the aperature to resist reversible lateral loads.

16. A method as in Claim 15 wherein the anchor resists tensile forces from the scaffold fitting and the headed screw and transmits said tensile forces to the structure.

16. A method as in Claims 4 & 14 wherein the thick walled tube fits within the bore in the structure to transmit reversible lateral forces from the scaffold fitting to the structure.

17. A method as in Claim 3 wherein the outer cylindrical surface of the load transmitting member engages with the circular parts of the aperture to resist reversible lateral loads from the sides of the aperture.

22. A method as in Claim 21 wherein the domed shape of the base or the domed washer within the fitting gives a good seating for the headed bolt and its washer or for a fixing screw bolt and its washer.

24. A method wherein the reversible lateral loads from the fitting are transmitted by the aperture in the base of said fitting into said load transmitting member and by it into the structure by bearing against the side of the bore in said structure.

25. A method as in Claims 3 & 16 wherein the shape of said aperture in said base is engineered to provide a load transmitting fit for said load transmitting members of varying shapes to transmit reversible loads.

29. A method of connecting various different anchor and sleeve means, the choice of which is determined by the loads to be resisted and by the details of the structure, to one design of scaffold fitting to transmit tensile and reversible lateral loads.

30. A method of connecting a variety of shaped load transmitting members in the aperture in the base of a scaffold fitting with a snug fit to transmit reversible lateral loads.

31. A method whereby the scaffold tube remains in the body of the fitting when the anchor means is loosened by turning the body making the removal of the reusable anchor from the bore easier and safer when the scaffold is dismantled.

32. An apparatus comprising a scaffold fitting and various load transmitting members and expanding anchors as hereinbefore described, with reference to, and as shown in Figures 1 to 4 of the accompanying drawings.

33. A method of securing to a surface a scaffold fitting substantially as hereinbefore described, with reference to, and as shown in Figures 1 to 4 of the accompanying drawings.