GB2180876A

GB2180876A - Scaffolding strut

Info

Publication number: GB2180876A
Application number: GB08523983A
Authority: GB
Inventors: James Baker
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-09-28
Filing date: 1985-09-28
Publication date: 1987-04-08
Also published as: GB2180876B; GB8523983D0

Abstract

A strut member for adjustable scaffolding devices of the type in which the relative axial position of two or more members are determined at least partly by a device which positively engages the members. The inner strut member 10 comprises a hollow section 11 incorporating an internal web 13. Into the periphery and along the length of the inner member are indented a number of grooves 12 crimping the internal web within the hollow section resulting in an integrated assembly. The web provides reinforcement for the hollow section and supports the load bearing function of the grooves. The grooves provide distinct and positive locations for an engagement device 15 housed in a carrier 14 which is attached to an outer jack assembly 20. In the example described the inner strut member forms part of a heavy duty unitary head or base jack. <IMAGE>

Description

SPECIFICATION Strut member for adjustable scaffolding This invention relates to a strut memberfor adjust- able scaffolding.

Theterm "adjustablescaffolding" as used in this specification is intended to mean any form of load bearing scaffolding device in which the relative axial position oftwo or more members is determined wholly or partly by the use of a positive engagement device which is usually in the form of a transverse pin passing through apertures or otherwise abutting the members.

Adjustable scaffolding devices are constructed in a variety of forms.

Forexample,to enable an array ofscaffolding standard uprights to be set level to one another irrespective ofthe attitude ofthe substrate an adjustable basejack is provided to the foot of each upright and a similarform of jack, known as a head jack can be provided atthetop of the uprights to establish a precise level of formwork or platform supported by the scaffolding.

Other forms of adjustable scaffolding devices include telescopic metal props and struts as defined in British Standards Specification BS 4074(1982) which are used forthe temporary support of lintels and ceilings during building or alteration work, ortrench shuttering. Prefabricated metal spitheads and trestles as defined in British Standards Specification BS 1139 part4 (1982),forthe supportoflow level platforms.

Another type oftelescopic adjustable scaffolding device known as a push-pull prop is used to adjust the vertical attitudeofshuttering orthe like and is capable of withstanding either compressive or tensile forces.

Current designs of adjustable scaffolding devices comprise three major components, an inner strut member, an outer member and a positive engagement device such as a load pin and they may also incorporate a supplementaryfine adjustmentfacility normally of the screw and nut type superimposed on the coarse adjustment range.

The inner strut member and the outer member are manufactured in metal from either circular or square hollow sections or pressed sections, the dimensions ofthe sections being such that the inner strut member is free to slide within the outer member. In- variably the means whereby the length adjustment is effected is by positioning a load pin through holes that have been made in the respective members, the additional holes to provide adjustment being along the length ofthe inner strut member which by nec essity is ofsmaller dimensions in its cross section.

This method of providing a coarse and positive adjustment facility although convenient incurs a number of disadvantages.

The already smaller sectioned inner strut member is further weakened by the addition of holes.

The load bearing area in way ofthe load pin is limited by the thickness of the section bearing against the pin and the need to keep the hole dimension to a minimum limits the cross sectional area ofthe load pin.

These constraints can lead to the use oflargerand or heavier sections than would otherwise be requi red for a given load-extension capacity. The produc tion of many holes in members that can be uptofour metres long is relatively expensive. In the case of adjustable base, or head jacks, where the cross sec- tion dimension ofthe inner strut member is limited bythe need to fit inside a scaffolding standard, and where a heavy load carrying capacity is required cur rent designs dispensewith the coarse adjustment facility and the devices used comprise a long threa ded stem with a nut.

Afurther operationai disadvantage of existing des igns oftelescopic adjustable props is that under load it can be difficult to adjust the screw mechanism to release the load on dismantling.

For convenience of description, the invention will be described in relation to an adjustable basejack but it will be appreciated that the principles of the inven tion are equally applicable to otherforms of adjust- able scaffold devices.

It is an object of the present invention to provide a strut memberfor adjustable scaffold devices as herein defined which overcomes or reduces these disadvantages.

It is a further object of the invention to provide a new form of heavy duty adjustable scaffold jack incorporating such a strut member.

According to the invention, there is provided a strut member of adjustable scaffolding devices, as herein defined which comprises a circular hollow section incorporating an internal web, into the per ipheryand along the length ofthesaid hollowsec- tion is indented a plurality ofgrooveswhose align- ment is across the longitudinal axis of material, the single length of which is such asto extend beyond all the said grooves. The depth of the said grooves is small relative to the cross section dimension of the said hollow section and reformed relative to and across the edge of the said web, crimping the said web inside the said hollow section.

The member is contained within a die during the indenting operation to maintain the straightness of the member and to ensure that the hollow section in way of and adjacent to the grooves does not deform to such an extent asto inhibitthe sliding fit when used in conjunction with an outer member.

These grooves provide positive and distinct locations for an engagement device which can have a variety offorms, depending on the configuration of the grooves, including asingleordoublepin,screw fastening, cotter, wedge, latch, keyplate, or collet mounted in a suitable carrier.

The carrier may be attached to an outer member which may form an externally threaded part of a scaffolding jack, alternatively it may comprise the outer telescoping member of an adjustable prop, strut or push-pull prop in each case including external screw threads, orthe outertelescoping member of a trestle or spithead.

The strut membermayalso be an integral partof other loadbearing scaffolding devices requiring an adjustment facility, for example, dropheads support- ing formwork.

According to a further aspect of the invention there is provided a heavy duty adjustable scaffolding jack comprising an inner strut member according to the first aspect of the invention attached to a baseplate, an outer assembly comprising an internally threaded outer sleeve and an externallythreaded sleeve attached to a carrier housing a positive engagement device.

The invention will now be described in more detail byway of example only with reference to the accompanying drawings in which Figure 1 is a vertical sectional view of a heavy duty adjustable scaffolding jack embodying a strut member.

Figure2 is a horizontal section through the strut memberoffigurel at position markedAA.

Referring to Figure 1 and Figure 2 on the drawings, a strut member is generally indicated at 10 in Figure 1 and comprises a circularhollowsection 11 and an internal web 13, into the assembly of which has been indented a plurality of grooves,12 12 being regularly spaced along the member.

In this particular case the outer member comprises a positive engagement device 15 mounted in a carriver 14and an externallythreaded sleeve 16 and an outer sleeve 17 incorporating a loop 18forming part of an adjustable scaffolding jack generally indicated by 20. The outer sleeve 17 is formed in this example from a hollow section swaged inwards at the top end 21 to provide a platform to supportthe foot of a scaffolding standard as indicated by the dotted outline 19. The other end ofthe outer sleeve 17 is also swa ged inwardsat22to reducethedimension ofthe hollow section locally, so that when threaded inter naliy, as a nut, it engages with a corresponding external thread cut on the member 16.It will therefore be seen that when the outer sleeve 17 is rotated relat iveto the member 16, if necessary by engaging a suitable lever in the loop 18, the axial relationship ofthe two parts can be finely adjusted.

The outer member 16 is attached to a carrier 14 which in this particular case is a fabricated pressing having aligned holes at 23 which enables the carrier to slide freely along the inner strut member 10. This carrier 14 houses in this example a positive engagement device 15 which is a circular section rod bentto form a "U" which can positively engage the groove 12, and is free to slide within the carrier in the directions indicated by the arrows in Figure 2.

Each leg of the "U" shaped rod 15 is cropped to approximately one half of the width of the rod, par ailel to its axis and for a length approximately one half ofthe straight length of the leg as shown at 24 in figure 2. The dimension between the cropped faces 24 ofthe rod is such that it is largerthan the overall diameter of the circular hollow section 11.Afurther piece of rod 25 is attached across the open end ofthe "U"shapedrodl5.

There may also be features formed in the carrier 14, not shown on the drawings such asto preventthe complete removal ofthe engagement device 15 from the carrier 14, in either direction.

The strut member generally indicated by 10 in Figure 1 shows a plurality of indented grooves 12.

In this particular case the grooves are shown as round bottomed and are arranged as opposed pairs along the strut member, but it will be appreciated that the principles ofthe invention are equally applic- abletoothergroove profiles and to other patterns of grooves spaced axially along the strut member.

In use, the inner strut member 10 is attached to a base-plate (not shown) and the member is setvertic- ally.

The outer assembly 20 is set to an approximate height by withdrawing the engagement device 15 within the carrier 14 sufficient to bring the cropped features 24to a position to clearthe holes 23 and sliding the assembly along the inner strut memberto an approximate position and aligning with a suitable pair of grooves 12. The engagement device 15 isslid into the carrierto positively engage with the grooves.

The scaffolding standard represented by 19 is assembled over the protruding inner strut member 10, which also acts as a spigot location, to bear againstthe platform feature 21 of the outer sleeve 17.

Fineadjustmenttothe relative height ofthe scaffolding standard is obtained by rotating the outer sleeve 17 relative to the member 16.

It will be seen that the grooves 12 in the inner strut member 10 provide positive and distinct locations for the positive engagement device, in this case a "U" shaped rod 15.

The inner strut member 10 incorporating the internal web 13 becomes an integrated structure after the operation indenting the grooves 12, no otherfixing being required.

The indenting operation which can be carried out in a press, each groove requiring only one blow in the machine and is a very rapid operation when compared to drilling holes and unlike holes drilled in hollow sections does not raise ragged edges around the features which need to be removed by an expensive deburring operation.

Material is not removed from the strut member 10.

The internal web 13 provides reinforcement to the strut member, which compensates for the local changes in the strut cross section profile in way ofthe grooves 12 and assists in maintaining the integrity of the strut as a load bearing member.

The internal web 13 also provides supportto the load bearing surfaces of the grooves 12 and prevents the strut member distorting under the action of the radial forces imposed by the positive engagement device 15.

It will also be seen that the strut member 10 is capable ofwithstanding axial forces, either compressive ortensile, transmitted through the positive engagement device 15.

In use, when concrete or mortar can fall onto the scaffolding eiements, the profile of the grooves 12 in the inner strut member 10 are such that debris falling onto the device will not easily cling and the wiping action of both the outer member 17 and the positive engagement device 15 when being manipulated during positioning and engaging will tend to remove any material adhering to the surfaces.

When the strut member, carrier and positive engagement device shown in figure 2 forms a compo- nent part of an adjustable load bearing device such as an adjustable prop, dismantling under load can be facilitated by "striking" the positive engagement de vice. This operation is achieved by driving the "U" shaped rod assembly 15 out of engagement with the grooves 12 by hitting the rod 25 with a mallet orsimilar instrument.

Claims

1. Astrut memberforadjustable scaffolding devices, as herein defined, which comprises a circular hollow section incorporating an internal web, into the periphery and along the length ofthe said hollow section is indented a plurality of grooves whose alignment is across the longitudinal axis of the said hollow section. The internal web which is a strip of material the single length of which is such as to extend beyond all the said grooves. The depth ofthe said grooves is small relativeto the cross section dimension ofthesaid hollow section are formed relative to and across the edge of the said web, crimp ingthesaidwebinsidethesaid hollow section.

2. A strut member according to CLAIM 1 wherein the hollow section is square.

3. A strut member according to CLAIM 1 wherein the hollow section is rectangular.

4. A strut member according to any preceding claim wherein the memberformsthe inner strut of a basejackor head jack.

5. Astrut member according to anyone of CLAIMS 1 to 3 wherein the strut member comprises the innertelescoping member of an adjustable prop or push-pull prop.

6. Astrut member according to anyone of CLAIMS 1 to 3 wherein the strut member comprises the innertelescoping member of a trestle or spithead.

7. A strut member according to anyone of CLAIMS 1 to 3 wherein the strut member comprises the strut of a drophead.

8. A strut member for adjustable scaffolding sub- stantially as herein before described with reference to and as illustrated in the accompanying drawings.

9. A heavy duty adjustable scaffolding jack comprising an inner strut member according to CLAIM 1, attached to a baseplate; an outer memberjack assembly attached to a carrier which contains a device which can be slid into the carrier so as to posi tivelyengagewiththe grooves formed in the inner strut member.

10. A heavy duty adjustable scaffoid jack incor- porating an inner member substantially as herein before described with reference to and as illustrated in the accompanying drawings.