GB2129902A - A fork or clevis bolt in clamps for tubular scaffolding - Google Patents

Abstract

In a clamp for tubular scaffolding a cover 2 hinged to a body 1 affording a seating 10 for a scaffold tube 5 is urged towards the seating to clamp the scaffold tube by a fork or clevis bolt 3 in which the limbs 24 of the clevis are curved, at least on the edges 26 towards the scaffold tube to be clamped. The curvature follows that of the seating 10 and a recess 13 in the cover. As illustrated, the limbs of the fork or clevis as a whole are curved and holes for a pivot 12 are offset to one side of the axis of the shank 14 of the fork bolt in the same direction as the limbs are curved. The fork or clevis bolt may be a one-piece forging or an assembly of a bolt and a sheet-metal fork or clevis element. <IMAGE>

Description

SPECIFICATION Clamps for tubular scaffolding This invention relates to clamps for tubular scaffolding generally, including not only putlog couplers and right angle and swivel couplers but any other scaffolding element which includes a clamp comprising a body defining a seating for a scaffold tube, a cover one end of which is hingedly connected to the body on one side of the seating and a clamp bolt hinged to the body on the other side of the seating, the shank of the bolt being engageable with a bifurcated end of the cover remote from the hinged connection of the cover to the body and fitted with a nut which, when tightened, urges the cover towards the seating and the cover defining an arcuate recess adapted to engage the side of a scaffold tube opposite that engaged with the seating.

The present invention consists in a fork or clevis bolt for use in scaffolding clamps from the head of which extend limbs forming a fork or clevis portion, aligned holes being pierced in the limbs for a pivot for hingedly mounting the bolt, wherein the limbs of the fork or clevis portion, are curved, at least on the edges which are adapted to be towards a scaffold tube to be clamped.

The limbs of the fork or clevis bolt, may be formed by folding a sheet metal element about the head of a bolt or otherwise, for example, by being forged in one piece with the shank.

The curvature preferably follows that of a seating for the scaffold tube in the body and/or cover of the clamp and may indeed extend the effective circumferential length of such seatings if shaped and dimensioned to make contact with the scaffold tube.

Preferably the limbs of the fork or clevis bolt as a whole are cranked or curved and the holes for the pivot are offset to one side of the prolongation of the axis of the shank in the same direction as the limbs are cranked or curved. When the clamp is done up around a scaffold tube not only does the edge of the limb next to the scaffold tube continue the curvature of the seatings in the body but the shank then extends in a direction which is inclined towards the scaffold tube. This enables the cover of the clamp to be shortened in itself saving material. As the bending movement for a given loading due to tightening the fork bolt is reduced by the shortening of the cover, either the cover is stronger for a given material thickness or further saving can be effected by using thinner material.

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 including a fork or clevis bolt 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, sa hinging the cover 2 on the body 1.

The cover 2 is shaped to form an arcuate recess 1 3 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 16 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 1 7 (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 18 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 1 9 of the rib 1 8 is closed and merges smoothiy into the surrounding surface of the part-cylndrical portion 6. The upper end 1 9 lies substantially in a plane normal to the line 9 and tangential to the outer surface of the hookshaped portion 6'. The rib 18 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 ledger 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 48.3 mm 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 18 is about three times the radial projection P and about one-third the overall width W of the part-cylindrical portion 6. The rib 1 8 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 cylindrical 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 substantial portion, for example of the order of 2700, of the circumference of the head 21 to positions at which their curvature is reversed to leave the curved surface of 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 head 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 12 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 13 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 13 meet the ends 2' 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 1 4 and the area available for contact by the washer 16 and nut 1 5 is enlarged.

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

The cover is slightly arched as appears in Figure 2 and the depth of the flanges 28 is substantially uniform around the middle of the arcuate recess 1 3 but at each end of the arcuate recess 13 they are considerably deeper. Where the web 27 is wider, therefore, the flanges are less deep so that 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" of the cover so that again the local widening of the web in this portion can be obtained from material which would 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 1 1.

Claims (6)

1. A fork or clevis bolt for use in scaffolding clamps from the head of which extend limbs forming a fork or clevis portion, aligned holes being pierced in the limbs for a pivot for hingedly mounting the bolt, wherein the limbs of the fork or clevis portion, are curved, at least on the edges which are adapted to be towards a scaffold tube to be clamped.

2. A scaffolding clamp comprising a body element defining a seating for a scaffold tube, a cover one end of which is hingedly connected to the body element on one side of the seating and a fork or clevis bolt according to claim 1, the fork or clevis bolt being hinged by its limbs to the body element on the other side of the seating, the shank of the bolt being engageable with a bifurcated end of the cover remote from the hinged connection of the cover to the body element and fitted with a nut which, when tightened, urges the cover towards the seating and the cover defining a recess adapted to engage the side of a scaffold member opposite that engaged with the seating.

3. A scaffolding clamp according to claim 2 wherein the curvature of the limbs of the fork of clevis portion follows that of a seating for the scaffold tube in the body and/or cover of the clamp.

4. A fork or clevis bolt according to claim 1 or a scaffolding clamp according to claim 2 or 3 wherein the limbs of the fork or cievis bolt as a whole are cranked or curved and the holes for the pivot are offset to one side of the prolongation of the axis of the shank in the same direction as the limbs are cranked or curved.

5. A fork or clevis bolt for use in scaffolding clamps the limbs of the fork or clevis being curved substantially as herein described with reference to and as illustrated by the accompanying drawings.

6. A clamp for tubular scaffolding comprising a fork or clevis bolt according to claim 1 or claim 5.