GB2197417A

GB2197417A - Space frame joint

Info

Publication number: GB2197417A
Application number: GB08625060A
Authority: GB
Inventors: Lawrence Paul; Kim Teck Sit
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-10-20
Filing date: 1986-10-20
Publication date: 1988-05-18
Also published as: GB8625060D0

Abstract

A joint for connecting a tubular member (1) to a node (3) in a space frame is disclosed. The joint includes a cap (5), for attachment to the tubular member (1), a bolt (31) for connection to a node and a connecting member (9). The bolt is arranged to pass through an opening in the connecting member (9) with the bolt head (35) being arranged to abutt against a shoulder (21) of the connecting member (9). In order to connect the tubular member (1) to the node (3) complementary threaded portions on the cap (5) and connecting member (9) are engaged one with another and the connecting member (9) is tightened, thus joining the member (1) to the node (3). The thread direction on the cap (5) is opposite to that of the bolt (31). <IMAGE>

Description

SPECIFICATION A joint for a space frame structure This invention relates to a joint for a space frame structure.

Space frames are reticulated structures formed from a plurality of elongate members, usually of a tubular form, connected together at the ends, by a suitable joint system. By assembling many joints and interconnecting tubular members a structure of any desired geometry may be constructed.

Some common applications of such space frame structures are in the construction of roofs of large span e.g stadia, community centres, hangars exhibition buildings etc, the structure often being constructed as a double layer grid, a plate like space truss built of two parallel plain lattice structures of nodes and tubular members which are mutually interconnected by vertical and/or diagonal bracing members.

A proposed joint, for connecting a node to a tubular member includes a cap member, which is welded to an end of the tubular member. The cap member has an opening for receiving the shaft of a bolt which shaft is threaded so as to engage a corresponding threaded opening in the node. The head of the bolt is larger than the opening in the cap member so that the bolt head is held in the tubular member against the sides of the cap member. A tightening member is attached to the shaft of the bolt, between the tubular member and the node, for tightening the bolt relative to the node.

In a first proposal, the tightening member comprises first and second nuts, the second nut acting as a lock nut for the first so that once locked in position on the threaded shaft of the bolt, the first nut may be turned so as to tighten the connection between the tubular member and the node.

In an alternative form, the shaft of the bolt is provided with a diametrical opening, for receiving a pin; a nut having an axial slit is positioned on the shaft, with the pin passing through the slit and the shaft to prevent relative rotational movement. The pin then has the function of the second nut mentioned above.

Such proposed joints have several disadvantages in that, they are difficult to assemble once the major portion of the' space frame is assembled, as the bolt is required to be placed in and projecting from the tubular member.

Since the most common anti-corrosion protection provided for steel tubular members is hot dip galvanising, it is not possible to fabricate the tubular member with the bolts in place because the treatment will damage the thread on the bolts. As such, the tubular member needs to be provided with an opening, for allowing the bolts to be inserted after the anti-corrosion treatment. This, however, results in a reduction in strength of the tubular member and introduces an unnecessary aperture in the tubular member.

It is an object of the invention, therefore, to provide an improved joint structure.

According to the invention in a first aspect, there is provided a space frame joint for connecting an elongate member to a node in a space frame structure, the joint comprising a first member connectable to a said elongate member, a second member connectable to a said node; and a third member arranged to engage the first and second members so as connect the first and second members together.

According to the invention in a second aspect there is provided a space frame structure comprising an elongate member, a node and a joint for connecting the elongate member to the node, the joint comprising a first member connectable to the elongate member, a second member connectable to the node; and a third member arranged to engage the first and second members so as to connect the first and second members together.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which Figure 1 illustrates a pipe, node and components of a joint according to an embodiment of the invention Figure 2 shows the components shown in figure 1 assembled.

With reference to figure 1, the essential components of a space frame structure including an embodiment of the joint of the invention are shown.

The structure includes an elongate tubular member 1, a spherical node 3 and a joint comprising a cap 5 (first member), shoulder bolt 7 (second member) and a connecting member 9 (third member), all preferably formed from steel.

The cap 5 is provided with a portion 11 of substantially the same diameter as the internal diameter of the pipe 1, a shoulder 13 having a diameter similar to the external diameter of the tubular member 1 and a threaded portion 15. The shoulder 13 is connected to the portion 11 via a tapered region 17. The cap 5 is also provided with an axial bore 41.

In use, the cap is placed over the end of the pipe, as shown in figure 2. The end of the pipe is chamfered at 18 and the cap 5 is welded to the tubular member 1 at 38, to ensure a firm connection.

The connecting member 9 is provided with an cylindrical bore 19 having a shoulder 21, for reducing the diameter of the bore adjacent one end to form an opening 20. The bore 19 is threaded at the opposed end to the shoulder 21, to form a threaded portion 23 which is complementary to the portion 15 provided on the cap 5.

The connecting member 9 has an external shape comprised of a cylindrical portion 25 within which recesses 27 are provided, for engagement of a tool for rotating the connecting member 9; and a frusto-conical portion 29 formed adjacent the opening 20 to avoid interference between joints at the node 3.

The bolt 7 is provided with a threaded portion 31, formed to engage with a complementary threaded radially disposed opening 32 provided in the node 3. The threaded portion 3 1 is connected to a sleeve portion 33 arranged to fit within the opening 20 in the connecting member 9, and a head 35 of the same diameter as the bore 19 in the member 9. The head 35 is provided with a diametrical slot 37 for receiving a screwdriver or similar tool for rotating the bolt 7 into threaded engagement with the node 3. Alternatively, an opening for receiving an Allen Key may be provided.

The thread direction of the threaded portions 31, 32 is opposite to that of the threaded portion 15, 23. preferably the portions 31, 32 have a right hand thread and the portions 15, 23 have a left hand thread.

In use, the cap 5 is connected to the tubular member 1, as described above, in the factory as part of the manufacturing process.

Also, the bolt 7 is preferably connected to the node 3, the bolt having being passed through the opening 20 in the member 9 prior to attachment to the node 3. Preferably, all components are hot-dip galvanised as part of the manufacturing process. In this case, the cap 5 is welded to the tubular member 1 before galvanising, the bore 41 allowing air to escape from the tubular member during the galvanising process; however, the threaded portion 15 is not machined until after the galvanising process. Similarly, the other threaded portions 23, 31, 32 are not machined until after their respective components have been galvanised.

On site, all that is required is for the threaded portion 15 of the cap 5 to be engaged with the corresponding threaded portion of the connecting member 9, the connecting member 9 then being tightened to hold the cap 5 and bolt 7 in abutting engagement, using a said tool engaged in recesses 27, so as to form a joint as shown in figure 2. As the thread direction of complementary threaded portions 15, 23 is opposed to that of portions 31, 32, tightening of the connecting member 9 will not loosen the connection between the bolt 7 and node 3, A prestress is applied between the head 35 of bolt 7 and the cap 5 by adequately tightening the connecting member 9. The axial length of head 35, threaded portion 15 and bore 19 are chosen so that, when fully tightened, a small gap 40 remains between the connecting member 9 and the shoulder 13 of cap 5, to ensure that threaded portion 5 abuts, in frictional engagement, against the head 35 of bolt 7, thereby ensuring a rigid connection.

It can be seen that if any part of the space frame is damaged during assembly at site or inadvertently damaged in any way, it is a simple step to undo the connecting member 9 and replace the relevant damaged part.

The dimensions of the spherical node, shoulder bolt, threaded shaft and conical bush can all be varied so as to sustain the required loads and size of the space frame structure of which they from part.

Claims

1. A space frame joint for connecting an elongate member to a node in a space frame structure, the joint comprising: a first member connectable to a said elongate member a second member connectable to a said node; and 0 a third member arranged to engage the first and second members so as to connect the first and second members together.

2. A joint as claimed in claim 1 wherein the first and third members are provided with complementary threaded portions.

3. A joint as claimed in claim 1 or claim 2 wherein the first member and the node are provided with complementary threaded portions.

4. A joint as claimed in claim 3 as dependent on claim 2 wherein the thread direction of the complementary threaded portions forming part of the second member and node differs to that of the complementary threaded portion 5 formed on the first and third members.

5. A joint as claimed in claim 4 wherein the complimentary threaded portions formed on the second member and node have a right hand thread.

6. A joint as claimed in any one of the preceding claims wherein the third member has a bore therethrough, the bore being provided, at a first end, with a shoulder, and the second member includes a head arranged to abut against the shoulder and a shaft arranged to pass through the bore and project from the third member, for engagement with the node.

7. A joint as claimed in claim 6 wherein, when the third member fully engages the first and second members, the first member is arranged to abut against the head of the second member in frictional engagement therewith.

8. A joint as claimed in claim 6 or claim 7 wherein the head of the second member is provided with means for receiving a tool for rotating the second member.

9. A joint as claimed in any one of claims 6 to 8 wherein the third member includes a first portion of cylindrical form and a second portion of frusto-conical form, said second portion being disposed adjacent said first end.

10. A joint as claimed in claim 9 wherein the cylindrical portion is provided with a plurality of recesses for engagement with a corresponding tool for rotating the third member.

11. In combination a joint as claimed in claim 9 and a tool for rotating said third member.

12. A space frame structure comprising: an elongate member a node a joint for connecting the elongate member to the node, the joint comprising: a first member connectable to the elongate member a second member connectable to the node a third member arranged to engage the first and second members so as to connect the first and second members together.

13. A joint substantially as hereinbefore described with reference to the accompanying drawings.

14. A space frame structure substantially as hereinbefore described with reference to the accompanying drawings.