GB2125881A

GB2125881A - Couplings for scaffold tubes

Info

Publication number: GB2125881A
Application number: GB08321624A
Authority: GB
Inventors: David Edgar Thorley
Original assignee: BOULTON SCAFFOLDING Ltd
Current assignee: BOULTON SCAFFOLDING Ltd
Priority date: 1982-08-12
Filing date: 1983-08-11
Publication date: 1984-03-14
Also published as: GB8321624D0; GB2125881B

Abstract

A putlog coupler having a body 1 made from sheet metal formed with a part-cylindrical portion 6 adapted to engage a putlog 4 and including a hook-shaped portion 6' which extends over the top of the putlog 4, has a rib 18 formed in the sheet material which projects from the side of the body opposite the hook-shaped portion and extends from a point 20 of a seating 10 for the ledger 4 for at least a major part of the height of the part- cylindrical portion 6. The rib stiffens the part-cylindrical portion against being opened out but does not interfere with the laying of staging on the putlog. <IMAGE>

Description

SPECIFICATION Couplings for scaffold tubes This invention relates to couplings for scaffold tubes and provides a coupling which is especially suitable for use in tubular scaffolding as a putlog or transom coupler. The term putlog is used hereinafter to refer both to putlogs and transoms.

As putlogs are often required to support staging, couplings used to secure them to other scaffold tubes should project as little as possible above the putlogs so that a substantially level surface is provided on which planks or boards forming the staging can be laid. Putlog couplers can also be used for securing guardrails to standards or other upright scaffold tubes of the coupler provided that the part engaging the guardrail projects little from the guardrail; the term putlog is therefore to be understood, if the context allows, as including guardrails.

In one known putlog coupler, used to secure a putlog across ledgers, that is longitudinal tubes, of a scaffolding structure, the body of the coupler is made from sheet metal which is shaped into a part-cylindrical portion, so as in use to lie against one side of the putlog and including a hookshaped portion which extends over the top of the putlog. Below the part-cylindrical portion the body extends downwards to form two ears lying parallel to the plane containing the axis of the partcylindrical portion and of the putlog when the coupler is in use. The ears are spaced apart to define between their confronting edges a recess defining a seating to receive a ledger of a scaffold structure. Each of the ears is pierced with a hole for pivots. One of the pivots hingedly connects one end of a cover (sometimes called a flap or a lid) to the body.The cover is shaped to form an arcuate recess to engage the side of the ledger opposite that located by the seating in the body. The end of the cover remote from its pivot to the body is bifurcated to receive the shank of a clamp bolt hinged by the other pivot to the body. When a nut on the shank of the bolt is tightened the cover is urged towards the ledger. By the same action the hook-shaped portion of the body is drawn towards the putlog so that the putlog and ledger are urged one against the other and jointly clamped between the hook-shaped portion and the cover.

In the body, between the ears, the marginal portion of the seating for the ledger is bowed outwardly on the side of the body opposite to the hook-shaped portion. In use, when the cover is tightened against one side of the ledger this bowed portion engages the opposite side of the ledger at a point offset along the axis of the ledger from the plane containing the ears. This is the plane in which the force due to tightening the cover is applied. The body thus constitutes a third order lever of which the point of contact of the bowed portion with the ledger is the fulcrum, and the applied force lies between the fulcrum and the free end of the hook-shaped portion. Consequently the free end of the hook-shaped portion is drawn towards the ledger and tightened upon the putlog.

In service the part-cylindrical portions of such putlog couplers can be strained, for example, if the cover nut is overtightened or overloaded in use.

The part-cylindrical portion can become opened out as a result and the hook-shaped portion may then not clamp the putlog effectively.

The present invention consists in a putlog coupler having a body made from sheet metal and formed with a part-cylindrical portion adapted to engage a putlog and including a hook-shaped portion which, in use, extends over the top of a putlog, the body being further formed with a seating adapted to engage a ledger or other scaffold tube and the coupler including means for pivotally connecting a cover to the body and means for tightening the cover to clamp the ledger, wherein the body has a rib formed in the sheet material, projecting from the side of the body opposite the hook-shaped portion and extending from the seating for at least a major part of the height of the part-cylindrical portion.

The means for tightening the cover may be a screw-threaded member, or a wedge or cam.

The rib stiffens the part-cylindrical portion against being opened out but does not interfere with the laying of staging on the putlog.

The rib may be of rounded form having an overall width greater than its projection, that is to say the distance the furthest point of the rib projects radially from the outer surface of the partcylindrical portion at a part adjacent the rib and the inner surface of which is adapted to engage a ledger.

The overall width of the rib may, for example, be two or three times its projection, and an appreciable proportion, for example between onequarter and one-half and preferably of the order of one-third, of the full body width, that is to say the dimension along the length of a putlog engaged by the part-cylindrical portion.

The rib and the seating for the ledger may be slightly offset from the middle of the width of the body so that the ear to which the clamp bolt is pivoted can be wider, and therefore stronger, than the ear to which the cover is hinged. The torque reaction on the ear due to tightening the clamp bolt imposes an additional load not imposed on the ear to which the cover is hinged.

The projection of the rib, at least at the seating, may be of the order of one-fifth to one-third of the external diameter of the ledger, for example, 12.5 mm for 48.3 mm outside diameter scaffold tubes.

The upper end of the rib is preferably closed and merges smoothly into the surrounding surface of the part-cylindrical portion.

The rib preferably extends for the full height of the part-cylindrical portion, that is from the seating for the ledger to the highest point of the outer surface of the hook-shaped portion in the direction mutually perpendicular to the longitudinal axes of a ledger and putlog clamped by the coupler.

A closed upper end of the rib may then lie substantially in a plane normal to the said mutually perpendicular direction and tangential to the outer surface of the hook-shaped portion. The upper end of the rib, in use, does not then project above the rest of the hook-shaped portion, and the hook-shaped portion as a whole does not project above a putlog it clamps by more than the thickness of the sheet metal material of which the body is made.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a perspective view of a putlog coupler according to the invention, Figure 2 is a front elevation, Figure 3 is a plan, and Figure 4 is an end elevation of the putlog coupler of Figure 1, Figure 5 is a fragmentary view on line V-V of Figure 2, and Figure 6 is a section on line VI--VI of Figure 2.

The putlog coupler illustrated in the drawings comprises a body 1, a cover 2 and a clamp bolt 3 and is shown in use, by ghost lines in some of the figures, to clamp a putlog 4 to a ledger or other scaffold tube 5 of a scaffold structure in which boards or planks are to be laid across the putlog 4 and other putlogs to form a staging.

The body 1 is made of sheet steel which is shaped into a part-cylindrical portion 6 which, in use, lies against one side of the putlog 4 and includes a hook-shaped portion 6 which hooks over the top of the putlog. Below the partcylindrical portion the body 1 extends downwards to form two ears 7, 8 lying parallel to the plane, indicated by the broken line 9 in Figure 4, and containing the axis of the part-cylindrical portion 6 and of the putlog 4 and at right angles to the axis of the ledger 5. The ears 7, 8 are spaced apart to define between their confronting edges a recess defining a seating 10 for the ledger 5. Each of the ears 7, 8 is pierced with a hole for pivot pins 11, 12 respectively. The pivot pin 11 pivotally connects one end 2' of the cover 2 to the ear 7, so hinging the cover 2 on the body 1.

The cover 2 is shaped to form an arcuate recess 13 to engage the side of the ledger 5 opposite that located by the seating 10 in the body 1. The end 2" of the cover 2 remote from the pivot 11 is bifurcated to receive a threaded shank 14 of the clamp bolt 3 which is hinged by the pivot pin 12 to the ear 8. A nut 1 5 and washer 1 6 is fitted to the shank 14. When the nut 1 5 is tightened on the threaded shank 14 the cover 2 is urged towards the ledger 5. This also draws the hook-shaped portion 6 towards the putlog 4. The putlog 4 and ledger 5 are urged one against the other at a point 17 (Figure 2) at which they cross and both the putlog 4 and ledger 5 are clamped between the hook-shaped portion 6' and the cover 2.

In the body 1, between the ears 7, 8, a rib 1 8 is formed in the sheet material projecting from the side of the body opposite the hook-shaped portion 6' and extending from the seating 10 for the full height of the part-cylindrical portion 6, that is to the highest point of the outer surface of the hookshaped portion 6' in the direction of the line 9 in Figure 4 which is mutually perpendicular to the longitudinal axes of the putlog 4 and ledger 5.

The upper end 19 of the rib 18 is closed and merges smoothly into the surrounding surface of the part-cylindrical portion 6. The upper end 19 lies substantially in a plane normal to the line 9 and tangential to the outer surface of the hookshaped portion 6'. The rib 1 8 thus does not project above the rest of the hook-shaped portion 6' which itself projects above the putlog by no more than the thickness of the sheet metal of which the body is made.

At the lower end the rib 1 8 terminates at the edge defining the seating 10 so that the seating 10 is bowed outwardly on the side of the body opposite to the hook-shaped portion 6'. The bowed portion of the seating 10 engages the ledger 5 at a point 20 (Figure 4) offset along the axis of the ledger 5 from the plane containing the ears 7, 8. This is the plane in which the force due to tightening the cover is applied.

As the cover 2 is tightened the body 1 tends to tilt (clockwise in Figure 4) about the fulcrum formed by the point of engagement 20 of the seating 10 with the ledger 5. The hook-shaped portion 6' is drawn towards the ledger 5 and tightened upon the putlog 4.

The rib 18 is of rounded form and merges smoothly into the outer surface of adjacent end parts 6" of the part-cylindrical portion 6. The inner surfaces of the parts 6" are the surface of the body which actually engage the ledge 5. The greatest radial projection P (Figure 4) of the rib 1 8 from the outer surface of the parts 6", in this example for use with 48.3mm outside diameter scaffold tubes, occurs at the point of engagement 20 and is about 12.5 mm. The overall width w (Figure 3) of the rib 1 8 is about three times the radial projection P and about one-third the overall width Wof the partcylindrical portion 6.The rib 18 and the seating 10 are offset slightly from the middle of the width W of the body in the direction away from the ear 8 which is thus enabled to be wider and stronger than the ear 7.

The clamp bolt 3 is a fork or clevis bolt assembly in which the bolt proper is a T-bolt having a head 21 of c.yl ndricai form having a diameter five-sixths that of the shank 14. A sheet metal element 22 forming the fork or clevis has an opening 23 through which the shank 14 extends.

End parts of the element 22 are folded about opposite sides of the head 21 to engage a substartial portion, for example of the order of 270 , af the circumference of the head 21 to positions at which their curvature is reversed to leave the curved surface OT the head 21 and extend to form parallel limbs 24 of the fork or clevis. Owing to the uniform curvature imposed on the portion of the element 22 in contact with the head 21 the opening 23 is only slightly elongated at the outer surface of the element 22 as shown In Figure 5. The width of the element 22 is equal to the length of the head 21 so that there is a large area of contact between the hpad and the fork or clevis element.These features combine to form a very strong fork or clevis bolt assembly.

The limbs 24 are cranked or curved as a whole and holes in the limbs for the pivot 1 2 are offset to one side of the prolongation of the axis of the shank 14 in the same direction as the limbs are cranked or curved.

The clamp bolt 3 is fitted to the body with concave edges 26 of the limbs 24 facing the seating 10. When in use for clamping a ledger 5 the concave edges 26 follow the curved surface of the ledger 5, as shown in Figure 2, and may make contact therewith to afford additional clamping surfaces. As a consequence of curving the limbs 24 and offsetting the holes for the pivot 12, the shank 14, when engaged with the cover 2, can be arranged to be inclined towards the seating 10 as shown in Figure 2.

The cover 2 is formed from sheet steel into channel section having a web 27 and flanges 28 substantially at right angles to the web 27. The free edges of the flanges 28 are shaped to form the arcuate recess 1 3 to engage the ledger 5 and lie on an imaginary part-cylindrical surface. The web 27 widens towards the middle 29 of the arcuate recess from the places at which the ends of the arcuate recess 1 3 meet the ends 2r and 2" of the cover. The widening of the web 27 and resulting separation of the flanges 28 towards the middle of the arcuate recess 1 3 provide points of contact with the ledger 5 which are well separated along the axis of the ledger with consequent improvement in the stability with which the coupler is clamped to the ledger.

The bifurcation of the end 2" of the cover is formed by piercing a slot 30 in the web 27. The slot 30 extends to an open end at the end of the cover 2 and at the other end is semi-circular. The web 27 is again widened, and the spacing apart of the flanges 28 increased, from both the adjacent end of the arcuate recess 13 and the free end of the cover, towards the position in the bifurcated end which the shank 14 normally occupies. The flanges 28 follow a curve substantially concentric with the shank 14 and the area available for oohtact by the washer 16 and nut 1 5 is enlarged.

When the slot 30 its pierced in the web, ribs 30' are formed projecting from the surface of the web Qn each side of the slot. The ribs 30' retain the washer when the nut 1 5 is tightened.

The cove is slightly arched as appears In Figure 2 and the depth of the flanges 28 Is substantlally uniform around the middle of the arcuate recess 13 but at each end of the arcuate recess 1 3 they are considerably deeper. Where the web 27 Is wider, therefore, the flanges are less deep so thtt the channel section can be formed from a blank of substantially constant width.

As shown in Figure 2 the flanges 28 taper towards the free end of the bifurcated portion 2" o'.f the cover so that again the local widening of the web in this portion can be obtained from material which wouid otherwise be cut to waste.

At the pivoted end 2' of the cover the web 27 is omitted but the flanges 28 are continued to form separate, flat, closely spaced, parallel limbs 31 which straddle the ear 7. Holes are pierced through the limbs 31 for the pivot pin 11.

Claims

1. A putlog coupler having a body made from sheet metal and formed with a part-cylindrical portion adapted to engage a putlog and including a hook-shaped portion which, in use, extends over the top of a putlog, the body being further formed with a seating adapted to engage a ledger or other scaffold tube and the coupler including means for pivotally connecting a cover to the body and means for tightening the cover to clamp the ledger, wherein the body has a rib formed in the sheet material, projecting from the side of the body opposite the hook-shaped portion and extending from the seating for at least a major part of the height of the part-cylindrical portion.

2. A putlog coupler according to claim 1 wherein the means for tightening the cover is a screw-threaded member.

3. A putlog coupler according to claim 1 or claim 2 wherein the rib is of rounded form having an overall width greater than its projection, that is to say the distance the furthest point of the rib projects radially from the outer surface of the partcylindrical portion at a part adjacent the rib and the inner surface of which is adapted to engage a ledger.

4. A putlog coupler according to any preceding claim wherein the overall width of the rib is two or three times its projection.

5. A putlog coupler according to any preceding claim wherein the overall width of the rib is between one-quarter and one-half of the full body width, that is to say the dimension along the length of a putlog engaged by the part-cylindrical portion.

6. A putlog coupler according to claim 5 wherein the overall width of the rib is one-third of the full body width.

7. A putlog coupler according to any preceding claim wherein the rib and the seating for the ledger are slightly offset from the middle of the width of the body so that the ear to which the clamp bolt is pivoted can be wider, and therefore stronger, than the ear to which the cover is hinged.

8. A putlog coupler according to any preceding claim wherein the projection of the rib, at least at the seating, is of the order of one-fifth to one-third of the external diameter of the ledger.

9. A putlog coupler according to claim 8 wherein the projection of the rib is substantially

12.55 mm for 48.3 mm outside diameter scaffold tubes.

10. A putlog coupler according to any preceding claim wherein the upper end of the rib is closed and merges smoothly into the surrounding surface of the part-cylindrical portion.

1 A putlog coupler according to any preceding claim wherein the rib extends for the full height of the part-cylindrical portion, that is from the seating for the ledger to the highest point of the outer surface of the hook-shaped portion in the direction mutually perpendicular to the longitudinal axes of a ledger and putlog clamped by the coupler.

12. A putlog coupler according to claim 11 wherein a closed upper end of the rib lies substantially in a plane normal to the said mutually perpendicular direction and tangential to the outer surface of the hook-shaped portion the arrangement being such that the upper end of the rib, in use, does not project above the rest of the hook-shaped portion, and the hook-shaped portion as a whole does not project above a putlog it clamps by more than the thickness of the sheet metal material of which the body is made.

13. A putlog coupler substantially as described herein with reference to, and as illustrated by, the accompanying drawings.