GB2135006A - Threaded fasteners - Google Patents

Abstract

A threaded bolt 1 (or nut) for use with slotted channel systems can be inserted through the slot and has an extension 4 on the head 2 that enters the slot and is shaped and dimensioned to permit rotation but restrict it to much less than 180 DEG . Material savings may result, because it is not necessary for the bolt head length x to be sufficient to reach the sides of the channel. <IMAGE>

Description

SPECIFICATION Threaded fasteners This invention relates to threaded fasteners; it relates primarily to bolts, but can also be applied to nuts. More specifically it relates to threaded fasteners for mounting in slots, and more especially (though not exclusively) in the slots of structural channel systems (such as the Applicant's channel systems sold under the trade marks Leprackand Intelok) comprising channel members with inturned flanges at the free endsofthe limbs thereof which definethe slot.

In the conventional use of such structural channel systems, the bolt head or nut (as the case may be) is of broadly rectangular shape and is dimensioned such that when longitudinally aligned with the slot it may be passed through it and then rotated (normally through substantially 90") to engage behind the edges of the slot. It will be evident that rotation through a further angle sufficientto make up half a turn will release the bolt-head or nut and needs to be inhibited at least during tightening ofthethreaded fastener.

Conventionally the bolt head or nut has been shaped to engage the limbs ofthe channel member, which in many cases requires a larger body than is dictated by any other function.

In accordance with the present invention, a threaded fastener having an axis defined by a male or female screwthread comprises (a) a main body having a minor dimension normal to the axis and a major dimension normal both to the axis and to the minor dimension and (b) an extension projecting axially from the main body and having a dimension in the direction ofthe major dimension ofthe main body that is substantially equal to or greaterthan the minor dimension ofthe main body but less than its major dimension; the shape ofthe extension and the direction in which it projects from the main body being such that the extension can enter a slot having some width less than the major dimension ofthe main body but not less than its minor dimension when the major dimension of the main body is transverse to the length oftheslotand can rotate in suchaslotthrough a limited angle much less than 180 (preferably about 9or).

In the case of a bolt, the extension will normally surround the base of the shank; in the case of a spring nut, itwill normally surround the threaded opening on the side remote from the spring; in the case of a plain nut it may be on either side, or if desired extensions can be formed on both sides to eliminate a risk of wrong mounting.

The cross-section of the extension may be a square with two opposite corners square and two corners radiused concentrically with the axis so as to permit rotation through 900 with the main body engaged with the edges ofthe slot; when the thread is right-handed, the rounded corners will bethetop right and bottom left as seen from outside the slot when the main body is positioned with its major dimension vertical. Other shapes consistent with function can be used.

The bearing surfaces on the main body may be ribbed for positive locking engagement with a slotted channel member having teeth formed on its free edges, in accordance with our U.K. Patent No.

2050549B.

We have found, during the testing of the improved bolts, that the pull load (the load required to pull the boltfrom the channel member) has been substantially increased above those recorded for conventional channel bolt fittings.

The invention will be further described, by way of example only, with reference to the following drawings, in which: Figure 1, Figure 2 and Figure 3 are mutually perpendicular views of a hot- orcold-forged bolt in accordance with the invention; Figure 4 is a perspective view of a channel member for use with the bolt of Figures 1-3; Figures 5, 6and 7are views corresponding to Figures 1,2 and 3 respectively of a second form of a hot- or cold-forged bolt in accordance with the invention.

Figures 1,2 and 3 show a bolt 1 comprising a head 2, a shank3 and an extension 4 positioned at the base of theshank.

The head 2 constitutes the 'main body' in accordance with the invention is of a broadly rectangular shape with minor dimension y and major dimension x normal to each otherand both normal to the axis ofthe threaded shank 3. Surrounding the base of the shank and integrally connected to both the head and the shank is an extension 4 having a dimension z in the direction of the major dimension x of the head and which is substantially the same as dimension y. The cross-section ofthe extension is a square with two opposite corners 5 square and the othertwo corners 6 radiused concentrically with the axis. The corresponding corners ofthe head are also similarly shaped.This ensuresthatthe bolt head can be inserted into the slot of a suitable channel (having a slot width slightly greaterthan y but much less than x), and the bolt rotated about its axis through an angle of about 90" whereupon the extension 4 engages with the edges of the slot. If the channel has an inside width of x, the head 2 will also engage with the limbs ofthe channel.

The bearing surface 7 on the head in this example is ribbedforpositive locking engagementwith aslotted channel member having teeth formed on its free edges in accordance with our U.K. Patent No.

2050549B, a suitable example of which is shown in Figure 4. In this particular example, the channel is made from mild steel sheet 2.5 mm thick roll formed to the shape shown with a width of 41.3 mm and a height also 41.3 mm. The inturned flanges are substantially semicircular and define a slot 22.3 mm wide. The flange edges are formed with teeth at a pitch of 2 mm.

Conventional 12 mm screwfittings usedwith such a channel have a safe pull-out load rating of 1000 kg force and observed pull-out failure loads in the range 1500-2000kg; failure is by unrolling distortion of the flanges.

When used with a 12 mm bolt ofthe form shown in Figures 1-3 in which the dimensions x, y and zwere 35.2,20.0 and 20.0 mm respectively, the observed pull-outfailure load was 3,500 kg and the mode of failure was by splaying ofthe channel sides. The safe pull-out load can therefore be set art kg.

Figures 5,6 and 7 show another bolt, in accordance with the invention, in which the dimension x of the head 2 is smallerthan in the first example. In this case the head will not engage the limbs of the channel and the engagement of the extension 4 with the slot edges is relied on to hold the bolt againstfurther rotation.

This modification has the advantage of substantial material savingsoverthefirstexample.

Claims (12)

1. Athreaded fastener having an axis defined buy a male orfemale screw thread comprises (a) a main body having a minor dimension normal to the axis and a major dimension normal both to the axis and to the minor dimension and (b) an extension projecting axiallyfrom the main body and having a dimension in the direction ofthe major dimension ofthe main body that is substantially equal to or greater than the minor dimension ofthe main body but less than its major dimension; the shape of the extension and the direction in which it projects from the main body being such thatthe extension can enter a slot having some width less than the major dimension ofthe main body but not less than its minor dimension when the major dimension of the main body is transverseto the length ofthe slot and can rotate in such a slotthrough a limited angle much lessthan 180 .

2. Athreadedfasteneras claimed in Claim 1 wherein the angle of rotation ofthe extension in the slot is limited to substantially 90".

3. Athreadedfastenerasclaimed in Claim2 wherein the cross-section ofthe extension is a square with two opposite corners square and two corners radiused concentrically with the axis so as to permit rotation through about 90".

4. A Bolt as claimed in any one of the preceding Claims.

5. Aboltasclaimed in Claim4wherein the extension surrounds the base oftheshank.

6. A nut as claimed in anyone of Claims 1 to 3.

7. Anutasclaimed in Claim 6wherein the extension surrounds one or both sides ofthethreaded opening.

8. A spring nut as claimed in any one of Claims 1 to 3.

9. A spring nut as claimed in Claim 8 wherein the extension surroundsthethreaded opening ontheside remote from the spring.

10. Athreaded fastener as claimed in any preced ing Claim, wherein the or each bearing surface on the main body is ribbed for positive locking engagement with a slotted channel member having teeth formed on its free edges.

11. Athreaded fastener substantially as described with reference to and as shown in Figures 1-3 ofthe accompanying drawings.

12. Athreaded fastener substantially as described with reference to and as shown in Figures 5-7 ofthe accompanying drawings.