GB2196380A

GB2196380A - Couplers for scaffold tubes

Info

Publication number: GB2196380A
Application number: GB08723320A
Authority: GB
Inventors: John William Barrett; David Edgar Thorley
Original assignee: BOULTON SCAFFOLDING Ltd
Current assignee: BOULTON SCAFFOLDING Ltd
Priority date: 1986-10-15
Filing date: 1987-10-05
Publication date: 1988-04-27
Anticipated expiration: 2007-10-05
Also published as: GB8624702D0; GB8723320D0; GB2196380B

Abstract

A putlog coupler made from sheet metal has a part-cylindrical portion (6) which in use engages a putlog (4), and an open hook-shaped portion (7) which extends in use over the top of the putlog. A reinforcing rib (19) is formed in the body of the coupler projecting away from the space in which the putlog is received. The rib (19) extends circumferentially from a seating (11) which in use engages the putlog and for at least a major part of the height of the part-cylindrical portion (6). At least one reinforcing formation (22) is formed in the sheet metal extending over the hook-shaped portion (7). The rib (19) may project further from the part-cylindrical portion near the seating than it does near the reinforcing formation (22). The rib (19) may blend into two formations (22) to form a Y shape. Thinner sheet metal may be used to form the coupler because of the strengthening of the rib and formation. <IMAGE>

Description

SPECIFICATION Couplers for scaffold tubes This invention relates to couplers for scaffold tubes and provides a coupler which is espcially 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.

Putlog couplers can be used for securing guardrails to standards or other upright scaffold tubes; 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 hook-shaped 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 part-cylindrical 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 has 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 tight ened 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 a hook-shaped portion may then not clamp the putlog effectively. To a large extent the thickness of the metal sheet of which the bodies of the putlog couplers have been made has been relied upon to provide the strength to resist straining in this way. Typically the sheet metal used has had a thickness of at least 4mm.

According to the present invention a putlog coupler is provided which has a body made from sheet metal and formed with a part-cylindrical portion adapted to engage a putlog and including an open 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 reinforcing rib formed in the sheet material, projecting from the side of the body opposite the hookshaped portion and extending from the seating for at least a major part of the height of the part-cylindrical portion, and at least one other reinforcing formation in the sheet material extending over the hook-shaped portion from the rib towards the free end of that portion.

The. rib and formation stiffen the part-cylindrical portion and hook-shaped portion against being opened out. Moreover sufficient stiffening may be achieved to enable thinner sheet metal to be used that that used conventionally. With suitable arrangement of the rib and formation sheet metal may be used which is three quarters or less, possibly two-thirds, of the conventional thickness of sheet metal.

Thus, for example 2.4mm-3.2mm thick sheet metal may be used. This can result in a significant saving in cost of material for manufacture of the coupler, as well as a weight reduction.

Preferably the reinforcing formation projects externally of the hook-shaped portion so as not to interfere with the engagement of the hook-shaped portion over a putlog, but the extent of the projection of the formation is limited in order to interfere as little as possible with the laying of staging on the putlog. The extent of the projection may be substantially less than the projection of the rib whilst enabling the formation to provide effective reinforcement. It may be less than a quarter of the projection of the rib, and may be similar to the thickness of the sheet metal of the body. The formation and an adjacent portion of the rib may present upper surfaces which lie in a common plane spaced just above the crest of the outer surface of the hook-shaped portion and normally substantially horizontal when the coupler is in use, thereby to provide a flat support for staging.

The formation may be an extension of the rib although, as indicated above, preferably projecting appreciably less than the rib, and preferably also narrower than the rib. The for mation may itself be in the form of a rib which may be substantially wider, for example at least four times wider, than its projection.

In one embodiment the projection of the rib is appoximately one-third to two-fifths of its width and its width occupies approximately two-fifths of the full body width, that is to say the dimension lengthwise of a putlog en gaged by the part-cylindrical portion The rib and formation may each have a profile which is at least partly rounded. That of the formation may be fully rounded, or be generally rounded, as, for example, by being of channel section with rounded sides. The rib may, for example, be triangular in cross-section with a rounded apex and substantially straight flanks or it may be of rounded top hat section. These are just some examples; it will be understood that the rib and formation may have other profiles which enable the body and hook-shaped portion to be reinforced.

The formation may extend to the free end of the hook-shaped portion, or it may at least as effectively reinforce the hook-shaped portion if it extends over most of the portion but stops short of the free end. In such an arrangement the formation preferably merges smoothly into the surrounding surface of the hook-shaped portion adjacent to the free end.

There may be two or more of the formations which may extend parallel to one another towards the free end, or they maybe in a non-parallel arrangement.

At least at the seating, the projection of the rib may be about one-quarter to one-third of the external diameter of the ledger, for example 17.5mm for 48.3mm outside diameter scaffold tubes.

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

Preferably the ears to which the clamp bolt and cover of the coupler are pivoted have holes plunged into them for the pivots. Plunging the holes produces bosses around the holes at the surfaces of the ears opposite to those at which the hole forming tools enter the ears. The holes are thereby extended beyond the thickness of the material of the ears and the bearing areas they provide for the pivots are increased. This compensates for the thinner sheet material which may be used for the body of the coupler so as to resist distortion of the metal at the ears under bear ing loads exerted by the pivots when the cou pler is in use.

An 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 putlog coupler in accordance with the invention.

Figure 2 is a plan view, and Figure 3 is an end view of the coupler.

the putlog coupler comprises a body 1, a cover 2 and a clamp bolt 3. As illustrated in the drawings the coupler is shown in use, by ghost lines in Fig. 1, clamping 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 as staging.

The body 1 is made of sheet steel, typically 3mm thick, which is shaped into a part-cylindrical portion 6 which, in use, lies against one side of the putlog 4 and includes a hookshaped portion 7 which hooks over the top of the putlog. Below the part-cylindrical portion 6 the body 1 is formed with two depending ears 8, 9 which lie parallel to the plane, indicated by the broken line 10 in Fig. 3, containing the axis of the part-cylindrical portion and of the putlog 4, being at right angles to the axis of the ledger 5. The ears 8, 9 are spaced apart to define between their confronting edges a recess which forms an arcuate seating 11 for the ledger 5. In each of the ears 8, 9 there is a plunged hole in which a pivot pin 12, 13 respectively is engaged. The bearing length of the plunged holes for the pivot pins 12, 13 is typically about 1.4 times the thickness of the sheet metal of the body.Pivot pin 12 pivotally connects one end 21 of the cover 2 to the ear 8, so hinging the cover to the body.

The cover 2 is shaped to form an arcuate recess 14 to engage the side of the ledger opposite that located by the seating 11 in the body. Remote from the pivot pin 12 the cover 2 has a bifurcated end 2" to receive a threaded shank 15 of the clamp bolt 3 which is hinged by the pivot pin 13 to the ear 9. A nut 16 and washer 17 are fitted to the shank 15. When the nut 16 is tightened on the shank 15 the cover is urged towards the ledger 5 and the hook-shaped portion 7 is drawn towards the putlog 4. The putlog 4 and ledger 5 are urged one against the other at a point 18, Fig. 3, at which they cross and both the putlog 4 and ledger 5 are clamped between the hook-shaped portion 7 and the cover 2.

In the body 1, between the ears 8, 9, a reinforcing rib 19 is formed in the sheet material projecting from the side of the body opposite the hook-shaped portion 7, and extend ing from the seating 11 to the top of the part-cylindrical portion 6 where it projects a short distance above the highest point of the outer surface of the hook-shaped portion 7.

At its upper end 20 the rib 19 has a medial portion 21 which merges smoothly and substantially tangentially down into the crest of the outer surface of the hook-shaped portion 7. At either side of that medial portion 21 the rib joins with two rib-like reinforcing formations 22 in the sheet-metal which extend, as continuations of opposite sides of the rib, parallel to one another over the hook-shaped portion towards a free end 23 of the hookshaped portion. These formations 22 stop short of the free end 23 and merge smoothly, tangentially, into the surface of the hookshaped portion adjacent to the free end. The formations project above the outer surface of the hook-shaped portion by an extent approximately equal to the thickness of the sheet metal.Uppermost surfaces 22', 20' respectively of the formations 22 and the adjoining end 20 of the rib 19 lie in a common plane normal to the plane 10. In use of the coupler these co-planar surfaces 22', 20' will normally be horizontal and provide a flat support for a staging plank.

For the most part the rib 19 has a generally triangular cross section with a rounded apex 24 and substantially straight flanks 25. Its projection from the part-cylindrical portion 6 reduces towards the upper end 20 although the width of the rib remains constant forts length. Adjacent to the seating 11 and for approximately half the length of the rib from the seating the flanks 25 of the rib merge smoothly into the outer surface of adjacent end parts 6' of the part-cylindrical portion 6, but for the remainder of the length of the rib the fianksm meet the part-cylindrical portion at a pronounced angle, as indicated at 26 in Fig.

2. The formations 22, which are of fully rounded form, similarly meet the outer surface of the hook-shaped portion 7 at a pronounced angle at their sides. It is at the inner surfaces of the end parts 6' that engagement of the body is made with the ledger 5. The greatest radial projection P, Fig. 3, of the rib 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 27 of the seating 11 with the ledger 5 and is about 16.5mm. The overall width w, Fig. 2, of the rib is about two and half times the radial projection P and about two-fifths the overall width w of the part-cylindrical portion 6.The radial projection of each of the formations 22 is only about one-fifth of one-quarter that of the radial projection P of the rib, in this example about 3mm, and the width of each formation is about three-tenths of the width w of the rib.

The rib 19 and the seating 11 are offset slightly from the middle of the width w of the body in the direction away from the ear 9 which is thus enabled to be wider and stronger than the ear 8.

The clamp bolt 3 is a fork or cievis body assembly in which the bolt proper is a T-bolt having a head 28 of cylindrical form having a diameter five-sixths that of the shank 15. The shank 15 extends through an opening 29 in a sheet metal element 30 forming the fork or clevis. End parts of the element 30 are folded about opposite sides of the head 28 to engage a substantial portion of the circumference of the head to positions at which their curvature is reversed to leave the curved surface of the head and form parallel limbs 31 of the fork or clevis. The width of the element 30 is equal to the length of the head 28 so that there is a large area of contact between the head and the fork or clevis.

Limbs 31 are cranked or curved as a whole and holes in the limbs for the pivot pin 13 are offset to one side of the prolongation of the axis of the shank 15 in the same- direction as the limbs are cranked or curved.

The clamp bolt 3 is fitted to the body with concave edges 32 of the limbs 31 facing the seating 11. When a ledger 5 is being clamped the concave edges 32 follow the curved surface of the ledger 5, Fig. 1, and may make contact with the surface to afford additional clamping surfaces. By curving the limbs 31 and offsetting the holes for the pivot pin 13 as described, the shank 15, when engaged with the cover 2, can be arranged to be inclined towards the seating.

The cover 2 is formed from sheet steel into channel section having a web 33 and flanges 34 substantially at right angles to the web 33.

Free edges of the flanges 34 are shaped to form the arcuate recess 14 to engage the ledger 5 and lie on an imaginary part-cylindrical surface. The web 33 widens towards the middle of the arcuate recess 14 from the places at which the ends of the arcuate recess meet the ends 2' and 2" of the cover. The widening of the web 33 and resulting separation of the flanges 34 towards the middle of the arcuate recess 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.

An open-ended slot 35 is pierced in the web 33 of the cover to form the bifurcated end 2". The web 33 is again widened, and the spacing apart of the flanges 34 increased, from both the adjacent end of the arcuate recess 14 and the free end of the cover, towards the position in the bifurcated end 2" which the shank 15 normally occupies. The flanges 34 follow a curve substantially concentric with the shank and the area available for contact by the washer 1 7 and nut 16 is enlarged. Nibs 35', formed when the slot 35 is pierced in the web, project from the surface of the web on each side of the slot and retain the washer in position before and when the nut 16 is tightened.

The cover is slightly arched and the depth of the flanges 34 is substantially uniform around the middle of the arcuate recess 14 but at each end of the arcuate recess they are considerably deeper. Where the web 33 is wider, therefore, the flanges are less deep so that the channel section can be formed from a blank of substantially constant width.

At the pivoted end 2' of the cover the web 33 is omitted but the flanges 34 are continued to form separate, flat, closely spaced, parallel limbs 36 which straddle the ear 7.

Holes are formed through the limbs 36 for the pivot pin 12.

The cover and the element 30 forming the fork or clevis may possibly be made of sheet metal of a thickness comparable to that of the body. In that event the holes in those components for their pivot pins 12, 13 may be plunged holes to increase the bearing areas provided for the pivot pins, as in the case of the pivot pin holes in the ears 8, 9 of the body.

A putlog coupler according to the invention will of course be suitable for connecting two elongate members of circular cross-section at right angles, irrespective of what the members are called, whether it be scaffolding members or (for example) components of a tubular storage racking system. For the avoidance of any doubt it is to be understood, therefore, that the putlog coupler of the invention used for such equivalent purposes, instead of with members that are strictly scaffolding, will nevertheless clearly be within the scope of the invention.

Claims

1. A putlog coupler comprising a body made from sheet metal and formed with a part-cylindrical portion adapted to engage a putlog and including an open 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 reinforcing rib formed in the sheet material, projecting from the side of the body opposite the hookshaped portion and extending from the seating for at least a major part of the height of the part-cylindrical portion, and at least one other reinforcing formation in the sheet material extending over the hook-shaped portion from the rib towards the free end of that portion.

2. A coupler according to claim 1 in which the rib extends circumferentially of the partcylindrical portion.

3. A coupler according to claim or claim 2 in which the reinforcing formation extends circumferentially of the hook-shaped portion.

4. A coupler according to any preceding claim in which the reinforcing formation projects externally of the hook-shaped portion.

5. A coupler according to claim 4 in which the extent of projection of the formation is substantially less than the extent of projection of the rib from the part-cylindrical portion.

6. A coupler according to claim 5 in which the extent of projection of the formation is less than one quarter of that of the rib.

7. A coupler according to any preceding claim in which the formation projects externally of the hook-shaped portion by an extent substantially equal to the thickness of the sheet metal of the body.

8. A coupler according to any preceding claim in which the formation and an adjacent portion of the rib present upper surfaces which lie in a common plane which, in the position of use of the coupler, is spaced just above an uppermost part of the outer surface of the hook-shaped portion and is normally substantially horizontal, said upper surfaces thereby providing a flat support for staging.

9. A coupler according to any preceding claim in which the reinforcing formation is an extension of the rib.

10. A coupler according to any preceding claim in which the reinforcing formation is narrower than the rib.

11. A coupler according to any preceding claim in which the rib is substantially wider than its projection.

12. A coupler according to claim 11 in which the rib is at least four times wider than its projection.

13. A coupler according to any of claims 1 to 11 in which the rib projects externally of the part-cylindrical portions, away from the putlog to the coupled, and in which the width of the rib is approximately two-fifths of the dimension, lengthwise of a putlog, engaged by the part-cylindrical portion, and the extent of projection of the rib is between approximately one-third of the width of the rib and two-fifths of the width of the rib.

14. A coupler according to any preceding claim in which the rib has a profile that is at least partly rounded.

15. A coupler according to any preceding claim in which the formation has a profile that is at least partly rounded.

16. A coupler according to any preceding claim in which the formation extends to the free end of the hook-shaped portion.

17. A coupler according to any one of claims 1 to 15 in which the formation extends over most of the hook-shaped portion, but stops short of the free end of the hookshaped portion.

18. A coupler according to claim 17 in which the formation projects externally of the hook-shaped portion and merges smoothly into the surrounding surface of the hook shaped portion adjacent to the free end.

19. A coupler according to any preceding claim in which there are two or more reinforcing formations.

20. A coupler according to claim 19 in which the formations extend parallel to one another towards the free end of the hookshaped portion.

21. A coupler according to any preceding claim in which the body defines a recess for receiving a ledger, the recess being of complementary curvature to the circumference of the ledger that it is intended to receive, and the seating part-defining the recess, and in which the projection of the rib is about onehalf to two-thirds of the radius of curvature of the recess.

22. A coupler according to any preceding claim in which the means for pivotally connecting the cover to the body comprises a pivotal connection between one end of the cover and a first ear of the body extending generally away from the part-cylindrical portion, and the means for tightening the cover to the body comprises a tightening member pivotally connected to a second ear of the body extending generally away from the partcylindrical portion, the first and second ears being on opposite axially spaced sides of the seating, and in which the rib and seating are offset from the middle of the axial width of the body so that the second ear is wider than the first ear.

23. A coupler according to claim 22 in which the ears have holes plunged into them to increase the bearing areas they provide for the pivots they receive.

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