GB2120094A - Clamping assemblies for support structures such as trestles - Google Patents

Abstract

A clamping assembly (1) comprises a pair of shoes (2) pivotally connected through opposed spaced lugs (4,4') and each having a socket portion for receiving a trestle leg, a jaw portion (8) for clamping a ledger member and a wedging member (14) of springy steel for spreading the legs.The inclined sides of the wedging member (14) are relatively movable one to the other so that the wedge angle is adjustable according to the size of timbers used for the legs and ledger member. Ledger supports are provided by the upper edge parts of opposed lugs (4, 4') which have different depth dimensions. For better stability in use of the trestle legs are splayed both laterally and outwardly relative to the ledger until both ledger supports engage the underface of the ledger before the assembly is clamped tightly together. <IMAGE>

Description

SPECIFICATION Clamping assembliesforsupport structures such as trestles The present invention relates to clamping assemblies of the kind used to construct a readily foldable or knock-down trestle or similar support structure and comprising a pair of pivotally connected shoes. Each shoe has a socket portion for receiving a trestle leg and a jaw portion for engaging a ledger member of the trestle and which co-operates with the jaw portion of the opposing shoe to provide a clamping action for securing the ledger member to the legs. Clamping assemblies ofthis kind will hereinafter be referred to as "clamping assemblies of the kind defined".

Examples of assemblies of the kind defined are disclosed in British Patent Specifications 321 505 and 632047.

One problem with known assemblies of the kind defined is that they provide insufficient rigidity in the assembled structure.

Attempts have been made to overcome the problem by providing nail or screw holes in the shoes so that, after assembly, nails or screws can be driven into the trestle legs and into the ledger member. This remedy is not always satisfactory and moreover if both shoes are nailed to the ledger memberthe trestle cannot be folded, which is highly desirable for reasons of space in storage and transportation.

It is also known from British Patent 632047 to use a releasable, rigid wedge which bears on the inner faces of the trestle legs so as to increase the grip of the shoe jaws on the ledger when tightened. This arrangement however makes inadequate provision for varying thicknesses of the timbers which may be used for the trestle legs and ledger member.

The present invention results from attempts to provide a more efficient clamping assembly of the kind defined which can be used with timbers of varying thickness and stiil enable folding of the trestle.

According to the present invention from one aspect a clamping assembly of the kind defined comprises stiffly resilient wedging means in which the mutually inclined wedging faces ofthewedging means are adapted to makeface contact respectivelywith a pair of legs received in the shoes over a substantial area thereof and in use are movable relative to each other to adjustthewedge angleto accommodate ledger or leg members of different thickness whilst maintaining said face contact.

Preferably, the wedging means is formed from a singie strip of metal bent about transverse lines to provide opposed, flat, inclined sides of substantial area, the free end parts preferably being arranged in overlapping disposition.

There may be morethan one"turn" ofthestrip in the mannerofa coil spring.

When the wedging means is formed of sheet material it may incorporate one or more recesses to provide "ribs" for added stiffness.

Preferably, the wedging means its loosely mounted on a rod suspended from a transverse barwhich provides the pivotal connection between the shoes, and in use the wedging means is vertically adjustable on the rod by screw means.

Each jaw portion comprises ledger support surfaces preferably provided by the upper edge parts ofthe spaced lugswhich receive the barforpivotal connection ofthe shoes.

The spaced lugs may be dimensioned so that both upper edge parts engage and support the ledger member when the legs diverge downwardly in a plane normal to the longitudinal axis ofthe ledger, or they may be differentially dimensioned so that the lug on the inwardly facing side of each shoe relative to a mid point on the longitudinal axis of the ledger member is of greater depth than the outer lug and in use both upperedgepartssupporttheledgeronlywhenthe legs diverge both downwardly and outwardly relative to the longitudinal axis of the ledger member.

Thus, according to the invention from another aspect in a clamping assemblyofthe kind defined each shoe is adapted by means of differentially dimensioned ledger support parts of the shoe to permit the trestle legs to be both downwardly and outwardly divergent relative to the longitudinal axis of the ledger memberwhilstfirmly supporting the ledger member.

A preferred embodiment of the invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a perspective view of a clamping assembly in accordance with the invention in use on a trestle, Figure 2 is a perspective view of the clamping assembly of Figure 1 showing the wedging means, Figure 3 is an elevation of one side of one shoe of the clamping assembly shown in Figures 1 and 2, Figure 4 is an elevation of the opposed side ofthe shoe shown in Figure 3, Figure 5is an end elevation ofthe shoe shown in Figures 3 and 4, Figure6isan end elevation ofthewedging means, Figure 7is a plan view ofthe wedging means, and Figure Bis an inverted plan of the wedging means.

The clamping assembly 1 comprises a pair of shoes 2, each of which is formed from steel plate bent to provide a rectangular channel section which is open at the top, bottom and on one side. The shoes are pivotally connected together with their open sides in confronting disposition by means of a bar or pin 3 extending transversely ofthe shoes th rough pairs of spaced lugs4,4' positioned substantially mid-way between the ends of each shoe 2 respectively. Below the lugs4, 4' a rectangular open area ofthe inwardly facing side of each shoe is defined by short inturned edges providing right-angled flanges 5. These flanges together with the otherthree closed sides form a socket of rectangular section which receives the upper end portion of a wooden trestle leg 6.Each shoe 2 is provided with strengthening ribs 28.

Above the pivot bar 3 the opposed sidewalls 7, 7' (Figures3 and 4) of each shoe are cut at an angle to provide inclined edges comprising opposed jaw portions 8 for receiving a ledger 11. The aforementioned lugs 4, 4' are integral with the shoe sidewalls 7, 7' and extend beyond the inner edges 5 of the sidewalls to provide a substantially right-angled recess in each sidewall defining a jaw portion 8. It will be seen from Figures 3 and 4thatthe opposed sidewalls 7 and 7' of each shoe 2 are of slightly differnnt configurations, the inner or right hand wall 7', when considered relative to the assembled trestle 1 shown in Figure 1, is longer and has an upwardly extended lug portion 10. The upper edges 9,9' ofthe Iugs4and4'togetherconstitute ledgersupport surfaces.When a clamping assembly 1 is mounted on a pairof legs 6 andvertically disposed relative to a horizontal ledger member 1 1 , becauseofthegreater depth dimensions ofthe lugs4' provided bythe portion 10, the upper edges 9' of the inner pair of lugs 4' will be at a higher level than the upper edges 9 ofthe outer pair of lugs 4. The geometrical arrangement of the shoe jaw portions 8 is such that when, in use, the jaws are pivoted laterally normal to the ledger axis to a position wherethe opposed jaw portions together present a substantially rectangular recess, the sockets, which are belowthe pivot bar 3, are at an angle of approximately40 degrees one to the other.In this position the opposed jaw portions can receive and supportthe ledger 11 which is of rectangular section but only the upper edges 9' of the inner pair of lugs 4' would be supporting the ledger 11. For greater stabilityofthetrestlethe Iegsarepivoted outwardly relative to a mid-point on the ledger axis until both upper edges 9 and 9' engage and support the ledger.

In this position the upper edge of each shoe 2 will be parallel to the ledger axis. With this arrangement it is possibletosplaythe legs 6 intwo directionswhilst keeping the ledger support surfaces 9,9' in full supporting contactwith the underface ofthe ledger 11 thus promoting greater stability to the trestle. The edges of the jaw portions 8 are provided with spaced teeth 12forgripping the ledger 11.

The laterally outwardly facing wall of each shoe 2, at approximately the level ofthe pivot bar3, is partially severed and turned inwardly to provide a stop 13 for the upper end of a trestle leg 6 when the latter is inserted into the shoe socket.

The aforementioned wedging means comprises an adjustable wedge 14 loosely mounted on a threaded rod 15 suspended by means of an eye portion 16from the pivot bar.

The eye 16 is a loose fit on the pivot bar 3 to enable the rod 15to be moved close to one edge of the shoe socket so that it can be pivoted outwardly of that edge to bring the wedge 14 outside the socket and so enable the shoes 2to be broughttogetherwith the legs 6 still in the sockets. A notch or recess 17 is provided in the sidewalls 7,7' of each shoe just beneath each lug 4,4' to provide adequate clearanceforthe rod 15.

The adjustable wedge 14 is formed from a single strip of springy steel plate bent about transverse lines to present two opposed, downwardly diverging, flat sides 18 of equal length and substantial width and two opposed sides 19,20 ofthe same width as the firsttwo sides but of different lengths. The four sides together form one "turn" of a box-like "spring" having one shortside 19. The short side 19 is defined by the overlapping free edge portions 21 ofthe "spring" strip and both the upper edge portions have co-operating elongate slots 22 thorough which the threaded rod 15 extends. When assembled to the rod 15 in use, the short side 19 of the "spring" is uppermost and the threaded end ofthe rod extends through a hole 23 in the opposed longer side 20 which is lowermost.A wing nut 24 and washer are provided to force the wedge upwardly in usetowardsthepivotbar3.

Strengthening ribs 26 and a recess27forthewasher are provided on the lower side 20 of the wedge 14.

Relative movement between the inclined sides 18 of the spring wedge 14 provides adjustmentfortimber widths of between 11/2" and 21/4".

Holes 25 may be provided in the shoes to allowthe use of anchor nails or screwsforthe legs 6, and if desired to enable one shoe 2to be secured to the ledgerll.

In usethe respective upperend portionsofthe legs 6 are inserted into the shoe sockets and moved inwardly until their end faces abutthe limit stops 13. The legs 6 are then opened to adjustthe angle therebetween according to the width ofthe ledgertimber 11 which is then inserted between the jaws 8. Each pair of legs is then adjusted in position to bring both the ledger support surfaces 9,9' intocontactwiththeunderface ofthe ledger 11. Thewedge 14 isthen movedto a central position between the legs 6 with its inclined flat sides 18 in face contactwith the legs through the open inner sides of the shoe sockets.The wing nut 24 on each clamping assembly 1 is then screwed inwardly to force the flat sides 18 of the spring wedges 14tightly againstthe sides of respective pairs of legs 6 so forcing them outwardly. Consequently, as the pivot bar is above the wedge 14, with each inward turn of the wing nut 24 the jaws 8 are brought closertogether to grip the ledger bar 11 more tightly as the sides ofthe wedge move together to adjust to the leg angle.

Normally, two clamping assemblies are used for each trestle.

In orderto fold the trestle the adjustable wedge 14 in each clamping assembly is released and pivoted outwardly of the sockets as described above.

In one modified arrangement of clamping assembly according to this invention the depth dimensions of the lugs 4 are made equal and the trestle is used with the legs 6 splayed in a plane normal to the ledger.

For convenience of the user pre-cuttimbers suitable forthe legs and the ledger of a trestle may be provided togetherwith at leastone pair of clamping assemblies.

Claims (9)

1. Aclamping assemblyofthekind defined comprising stiffly resilient wedging means in which the mutually inclined wedging faces ofthe wedging means are adapted to make face contact respectively with a pair of legs received in the shoes over a substantial area thereof and in use are movable relativeto each otherto adjustthewedgeangleto accommodate ledger or leg members of different thickness whilst maintaining said face contact.

2. Aclamping assemblyas claimed in claim 1 wherein the wedging means is formed from a single strip of metal bent abouttransverse lines to provide opposed, substantially flat, inclined sides ofsubstan- tial area.

3. A clamping assembly as claimed in claim 2 wherein the strip comprises free end parts in overlapping disposition.

4. A clamping assembly as claimed in any ofthe preceding claims wherein the wedging means is formed from springy steel.

5. A clamping assembly as claimed in any ofthe preceding claims wherein the wedging means is loosely mounted on a rod suspended from a transverse bar which provides the pivotal connection between the shoes, and the wedging means is adjustablealongthe rod by screw means.

6. A clamping assembly as claimed in any ofthe preceding claims wherein ledger support surfaces are formed by upper edge parts of a pair of lugs provided on each shoe for pivotally connecting the shoes and wherein the lug on the inwardly facing side of each shoewhen considered relative to a mid point on the longitudinal axis of the ledger member has a greater depth dimension than the other,to permitthetrestle legsto be both downwardly and outwardly divergent relative to the longitudinal axis ofthe ledger member when the ledger memberis engaged with the ledger support surfaces.

7. A clamping assembly as claimed in claim 6 wherein a notch is provided beneath each lug for receiving the rod when the shoes ofthe clamping assembly are pivoted inwardly when not in use.

8. A clamping assembly of the kind defined substantially as hereinbefore described with referenceto and as shown in the accompanying drawings.

9. Aclamping assembly of the kind defined wherein each shoe is adapted by means of differential- ly dimensioned ledger support parts ofthe shoe to per:nitthetrestle legsto be both downwardlyand outwardly divergent relative to the longitudinal axis of the ledger memberwhilstfirmly supporting the ledger member.