The present invention relates to a connector system suitable for connecting truss modules. The connector system would also be suitable for connecting other tubular elements together.

Truss gantry systems are commonly used in the exhibition, entertainment and events industry for supporting lighting and stage set rigging. They are reasonably quick to erect, relatively easy to transport, strong (if assembled correctly), and can be built in different configurations.

A truss gantry system is made up of several truss modules. Each truss module may have two, three or four parallel rails or bars which may be tubular, and which may be referred to as chords.

Systems currently available to connect truss modules include opposing forked ends joined with pins or nuts and bolts; internal pipe connectors joined with a nut and bolt through each end; or, the most widely-used system, the double-ended tapered lug and spigot pin arrangement.

THE TAPERED LUG AND SPIGOT PIN CONNECTOR

The chords in each truss module are specially manufactured or adapted to use a lug and pin. An internally-tapered collar is welded to each end of the chord to accommodate a lug which is conically tapered at each end. Tapered entry and exit holes are machined on opposite sides of the collar to accommodate a tapered spigot pin. The collar also has a central bore and defines an internal step, or edge, of around 5mm, where the collar meets the remainder of the chord. The double-ended tapered lugs are usually machined from solid aluminium. These lugs have a transverse tapered hole passing through both ends to accommodate the spigot pin. Tapered spigot pins are manufactured from high-grade steel. (The material used for the spigot pin impacts on the strength of the truss system.) A small hole is machined in the thinnest end of the spigot pin to accommodate a safety clip. To assemble a truss, one double-ended, tapered lug is fitted into the tapered collar of each chord. It is secured with a tapered spigot pin which is fitted through the hole in the collar, through the lug and out through the hole in the other side of the collar. The pin is held in place with the spring safety clip, slotted through the small hole in the end of the spigot pin. Once lugs are fitted into the ends of all the chords in a truss module, the module is mated to another truss module by inserting the projecting ends of the lugs into the collars of the other truss module, and again secured with spigot pins and safety clips.

There are however some problems arising from use of this tapered lug and spigot pin system:

(i) A high degree of accuracy is required in manufacturing truss modules. All the holes must line up and all the tapers must match correctly so that spigot pins can be inserted all the way through the truss, with sufficient clearance for safety clips to be fitted.

(ii) Assembly can be time consuming while holes in collars, lugs and pins are lined up. Any slight inaccuracy in manufacture means that pins have to be driven into place with a hammer. This is a commonly-used method of assembly.

(iii) Hammering in the spigot pins (which are tapered) damages and widens the entry holes in truss collars. The widened holes allow spigot pins to vibrate loose, leaving the truss with 'sloppy' joints which can contribute to structural weakness

(iv) On site, stocks of safety clips can run out, be lost or damaged, or riggers can forget to fit them.

(v) The specially-designed spigot pins might accidentally or intentionally be replaced with pins made from inferior materials, or stocks of correct spigot pins may be mixed with inferior pins. Inferior pins can reduce the safety factor of the lug connector from 5 to 1 down to 1 to 1 , compromising the safety and reliability of a structure. Truss structures are designed to carry specific loads under varying climatic conditions including snow weight and high wind movement, and substituting components can seriously affect the strength of these structures. THE PRESENT INVENTION

According to the present invention there is provided a connector system suitable for truss modules, the connector system comprising:

- a tubular double-ended lug having opposed end portions which may be inserted into collars of truss modules, at least one hole being defined near the end of each end portion;

- a locking element movable within each hole between a locked position in which the locking element projects radially beyond the surface of the end portion, and a retracted position;

- a control strut movable axially within the bore of the end portion between a first position in which the locking element is thereby secured in the locked position, and a second position in which the locking element is free to move into the retracted position;

- an actuating member at a central portion of the tubular double-ended lug between the end portions, the actuating member being movable between a first position in which each control strut is in its first position, and a second position in which each control strut is in its second position, movement of the actuating member enabling movement of each control strut.

In one preferred embodiment the actuating member also includes a safety button which is engaged when the actuating member is in the first position, the safety button being released to enable the actuating member to be moved into its second position.

In one preferred embodiment the actuating member, when in its first position, is substantially flush with the tubular double-ended lug, whereas when it is in its second position it projects radially from the tubular double-ended lug. This ensures that a truss assembly can be easily inspected to check that each connector system is locked, because if any connector system is unlocked then the control strut must be in its second position, and the actuating member is therefore projecting. Preferably the connector system also includes springs to act on the locking elements, and to urge them into the locked position. The locking elements may be balls, for example stainless steel balls.

As mentioned previously, the collars on truss chords have a central bore hole and an internal step, or edge, of around 5mm. The connector system of the invention may be of a suitable size to fit through the central bore hole in these truss collars, and the locking element would catch against the internal step. The connector system is locked in place with a push-button activator mechanism. No holes or extra components are required to connect it to another truss module or secure it in place.

In each of the examples described below, the actuating member is movable between the first position and the second position along a line which is transverse to the longitudinal axis of the connector system. The invention will now be further and more particularly described, by way of example only, and with reference to the accompanying drawings in which:

Figure 1 shows an exploded view of a connector system of the invention;

Figure 2 shows a sectional view of the connector system of figure 1 when assembled, in its unlocked position;

Figure 3 shows a sectional view of the connector system of figure 1 when assembled, in its locked position;

Figure 4 shows the sequence of operation of the connector system of figure 1 ;

Figure 5 shows a perspective view of an alternative connector system of the invention; Figure 6 shows a part-sectional view of the connector system of figure 5 in the unlocked position;

Figure 7 shows a view equivalent to that of figure 6, but in the locked position;

Figure 8 shows an exploded view of the connector system of figure 5; and

Figure 9 shows sectional views of three alternative collars for use with the connector system of figure 5.

DESCRIPTION AND OPERATION

The connector system of Figure 1 is referred to as an inner-slide truss connector (ISTC). Referring to Figure 1 , an ISTC has a main body 1 with an activator button 3 positioned in a collar 2 mid-way along the main body 1 . The activator button 3 comprises a cap 24 and a safety release button 4 in the cap 24. The safety release button 4 operates in the opposite direction to the activator button 3 and must be depressed to allow the activator button 3 to move. When the safety button 4 is depressed, the activator button 3 can be slid

perpendicular to the connector's main body 1 . This forces activator balls 20 to slide along oppositely-inclined grooves 22 inside the body of the activator button 3, these grooves 22 being aligned at an angle to the longitudinal axis of the main body 1 ; the angle is 45° in the embodiment shown in the drawings, although in an alternative embodiment the grooves 22 may be at a different angle such as 60°. The activator balls 20 are also held firmly within two sliders 7 which run lengthways through the main body 1 and activator button 3.

Because of their engagement with the inclined grooves 22, as the activator button 3 is pushed in, the balls 20 push the sliders 7 lengthways, in opposite directions from each other, away from the activator button 3.

Connected to each slider 7 is a push-rod 8 which is screwed into position. (Screw- fitting aids assembly and retains the activator balls 20 in position.) The push-rods 8 incorporate a waist indent 9 large enough to accommodate locking balls 10. These locking balls 10 are held under spring pressure from a spring 12 within seat cavities in the ends of the main body 1 . The motion of the sliders 7 moves the push-rods 8 so the waist indents 9 are positioned under the locking balls 10 in the main body 1 . At this stage, the locking balls 10 are not depressed into the waist indents 9 as the spring pressure holds them in position. When the ISTC is inserted into a collar 30 of a truss chord 32, the tapering of the hole depresses the locking balls 10 into the push-rod waist indents 9. This allows the end of the ISTC to pass through the hole in the truss collar 30. Once through, the spring pressure pushes the locking balls 10 back out so they become captured behind the collar edge. When the ISTC is in place, the activator button 3 is pressed back to its original position, flush with the main body 1 . This action retracts the sliders 7 and push-rods 8 and therefore the waist indent 9. This means that the locking balls 10 are held in place behind the collar edge as they are unable to fall back into the waist indent 9. The ISTC does not rely on spring pressure to function. The springs 12 are included to make the connection of trusses easier if they are assembled on their sides or upside down. The springs 12 prevent the locking balls 10 from retracting and stop the ISTC from falling out of the chord 32 while trusses are being assembled. If the spring 12 in one end of the ISTC is stronger than the spring 12 in the other end, the ISTC will tend to remain in one truss 32 when two trusses are separated. This is a safety feature to help stop the ISTC accidentally dropping out of both trusses 32 when an assembly is being dismantled.

The ISTC cannot be released without moving the push-rod waist indents 9 beneath the locking balls 10. This can only be done by depressing the safety button 4.

The safety release button 4 comprises an 'apple-core' shaped button, safety button balls 1 1 and a central spring 13. When the safety release button 4 is not engaged, the safety button balls 1 1 sit in indents in the collar 2 of the main body 1 . When the safety release button 4, which is under spring pressure, is depressed, the safety button balls 1 1 can move into the 'apple core' indent. The inward movement of the balls 1 1 releases the activator button 3 which can then be moved perpendicular to the main body 1 .

Referring to figure 4, this illustrates the operation of the ISTC being inserted into collars 30 that are welded to the ends of truss chords 32. In the upper drawing the ISTC is shown in the disengaged position, with the activator button 3 projecting out from the main body 1 . The locking balls 10 do not project, as they locate in the waist indent 9, so the locking balls 10 do not engage with the inner edge of the collar 30. In this position the ISTC can be slid in or out of the collars 30.

If the activator button 3 is pushed in 9 mm, this pulls the pushrods 7 axially 9 mm towards the middle of the ISTC. This changes the ISTC into the engaged state shown in the lower drawing, in which the locking balls 10 protrude through the radial holes in the ends of the main body 1 (not shown on the right hand side), and therefore engage behind the inner edge of the collar 30. In that position of the activator button 3, the safety release button 4 would be released, and would move upwards (under pressure of the spring 13) by 6 mm, into the position shown in figure 3 in which the activator button 3 is secured in this position.

KEY POINTS ABOUT THE ISTC

- Initial computer testing shows that the ISTC is strong and compares favorably with the tapered lug and spigot pin system (used with the correct pins).

- It's safe and easy to use, simple to connect and release.

- Trusses can be assembled in a quarter of the time or less. With the tapered lug and spigot pin system (main body, two pins and two 'R' clips) the estimated assembly time of one four-chord truss to another at ground level is about 90 seconds if all pins fit without hammering. With the ISTC system, a self-contained unit, the estimated time is less than 20 seconds with no tools required

- The ISTC can be supplied to existing customers for use with previously purchased collared trusses 30, as well as to new customers.

- As there is no possibility of fitting inferior pins or forgetting safety clips, pre-determined strength capabilities at the joints can be achieved every time a truss is assembled, even if it is assembled by non-qualified erectors.

- The ISTC is held in position by spring pressure even when unlocked. This allows trusses 32 to be assembled at ground level on their sides without the connectors dropping out.

- If the connector is not properly engaged, the protruding activator button 4 can be seen from ground level, providing a visual safety feature.

ALTERNATIVE CONNECTOR

Referring now to figure 5, an alternative connector system 40 has several similarities to the ISTC of figures 1 to 4, and is used in substantially the same way. The connector system 40 has a main body 41 with an activator element 43 positioned in a collar 42 midway along the main body 41 . The activator element 43 includes a safety release button 44. The safety release button 44 operates in the opposite direction to the activator element 43 and must be depressed to allow the activator element 43 to move up. The activator element 43 may define a finger recess for user comfort when depressing the safety release button 44. Tubular end portions 45 of the main body 41 project from each end of the collar 42, and define apertures 46 through which project locking balls 50. The connector system 40 is shown in the locked position. In use, with the end portions 45 inserted into collars 30 at the end of truss chords 32, the locking balls 50 in the position shown would engage behind the inner edge of the collar 30 and would prevent removal of the connector system 40. In this respect operation is equivalent to that of the ISTC, as shown on the left-hand side of figure 3, but the collar 30 would be shorter (as discussed below in relation to figure 9).

Referring now to figure 6, this shows the internal mechanism of the connector system 40 in the unlocked position, with the main body 41 in section, and with the activator element 43 also in section, but in an orthogonal plane. The activator element 43 is cylindrical, sliding in a cylindrical channel 48 orthogonal to the longitudinal axis of the main body 41 . A lower portion of the activator element 43 defines two opposed part-spherical recesses 52, above which are shallow grooves 51 (see Figure 8). The recesses 52 are aligned with the longitudinal axis of the main body 41 when the activator element 43 is in the unlocked position. The safety release button 44 is also generally cylindrical, sliding in a cylindrical cavity 53 at the upper part of the activator element 43. Two balls 55 locate in opposed radial holes through the activator element 43; and the safety release button 44 defines two opposed part-spherical recesses 56 (see figure 7) and a shallow groove 57 below it. In the position shown in figure 6, the balls 55 fit into the recesses 56, so that the activator element 43 can move axially into the position as shown. The safety release button 44 is pushed upwards by a spring 60 (see figure 7), towards the position shown in figure 5; but with the activator element 43 in the position shown in figure 6 the balls 55 are held against the wall of the cylindrical channel 48, so the safety release button 44 is held in this position.

Within each tubular end portion 45 is a generally cylindrical push rod 62 with a part- spherical head 63 at one end, and a narrow projecting pin 64 at the opposite, outer end. In the unlocked position, the part-spherical heads 63 of the pushrods 62 locate in the part- spherical recesses 52 of the activator element 43. The locking balls 50 locate in the apertures 46, but rest on the projecting pin 64; the apertures 46 may be peened over on their outer edge, or may be shaped as ball sockets, so the locking balls 50 can't fall out. A helical spring 66 around the push rods 62 exerts an axial force pushing the balls 50 and the part-spherical heads 63 apart. In a modification, the pushrod 62 may taper slightly from the part-spherical head 63 down towards the projecting pin 64, to assist retraction and to reduce the risk of jamming.

In the unlocked position, as shown in figure 6, the tubular end portions 45 can be inserted into collars 30 of truss chords 32, because the balls 50 do not project radially. Referring now to figure 7, this shows the internal mechanism of the connector system 40 in the locked position, with the main body 41 in section, and with the activator element 43 also in section, but in an orthogonal plane. The activator element 43 has been slid through the channel 48 until the ends of the activator element 43 are flush with the outer surface of the collar 42. The part-spherical heads 63 no longer align with the recesses 52 and instead locate within the shallow grooves 51 (see figure 8), so the pushrods 62 are pushed axially outward, and the locking balls 50 are therefore pushed radially outward through the apertures 46, so they project, and are held by the cylindrical part of the pushrods 62. This compresses the helical springs 66. In a modification, an insert of wear-resistant material may be inset into the surface of the activator element 43 at the lower edge of each shallow groove 51 , where the shallow groove 51 communicates with the recess 52, to minimise wear.

The cylindrical channel 48 defines two opposed recesses 68, such that when the activator element 43 is positioned with its end flush with the collar 42, the balls 55 can move radially outward into the recesses 68. The spring 60 can then push the safety release button

44 upward, so it is also flush with the end of the activator element 43, and in this position the balls 55 are at the bottom of the shallow grooves 57 (see figure 6). Since the balls 55 are in the recesses 68, the activator element 43 is not free to move. For simplicity of assembly, such opposed recesses 68 may be provided adjacent to both ends of the cylindrical channel 48.

When the connector system 40 is to be removed from a collar 30, the safety release button 44 is depressed against the force of the spring 60, and then the activator element 43 can be pushed up, the balls 55 moving into the recesses 56. As the activator element 43 is pushed up, the compression springs 66 push the pushrods 62 axially until the part-spherical heads 63 fit into the recesses 52. The balls 50 are then free to move radially inwards, and so the connector system 40 is in the unlocked position as shown in figure 6. In a further modification, each tubular end portion 45 of the connector system 40 may be provided with a dust cap covering its open end. For example the tubular end portion

45 may be slightly lengthened, and define a groove to locate a dust cap (not shown). The dust cap may define means to guide the projecting pin 64, ensuring it remains axial within the tubular end portion 45. (Similarly, such a dust cap might be provided in the ISTC of figures 1 to 4.)

If the spring 66 at one end of the connector system 40 is stronger than that at the other end, the connector 40 will tend to remain in one truss 32 when two trusses are being separated. This is a safety feature to reduce the risk of the connector 40 accidentally dropping out of both trusses 32 when an assembly is being dismantled. One difference between the connector system 40 and the ISTC is that the ISTC mechanically actuates the pushrods 8 both when locking and unlocking, whereas in the connector system 40 the movement of the push rods 62 is mechanically actuated when locking, and is spring-actuated when unlocking. Another difference in the versions shown in the figures is that the connector system 40 is shown as having shorter tubular end portions 45 than the equivalent portions of the ISTC, so it can be used with a shorter collar 30. It will be appreciated that the ISTC might be modified for use with a shorter collar 30.

Referring to figure 9, this shows a variety of types of collar 30. The collar 30a of the top figure comprises a steel ring insert 33 with a curved inner face 34, which is mechanically pressed into an aluminium collar 35, and the edge of the collar 35 is peened over to hold the steel ring insert 33 in place. The aluminium collar 35 would then be welded to the end of the truss 32. The collar 30b of the middle figure is substantially the same shape as the collar 30a, but is a single component of aluminium, which is welded to the end of the truss 32. This is suitable for use where there are lower loads, and so reduced wear and tear on the collar 30b. It would generally be made from aluminium for use with an aluminium truss 32, but it might be made from steel for use in a steel truss.

The collar 30c is for use as a rapid-use connector, for example for connecting low- loaded rails such as handrails. It is made of spring steel, or another suitably resilient material, it is intended to be hammered into a square-cut end of a pipe or truss 32. It comprises an outer collar 36 which defines two slots 37 on a diameter on the outer face, and a curved inner face 34, and with a projecting cylinder 38 with projecting ratchet-shaped ribs 39. One slot 37 extends the length of the projecting cylinder 38, so it is deformable on insertion. The ribs 39 may be circumferential circles, or may be formed as a helical thread so the collar 30c can be subsequently removed, using the slots 37 on the outer collar 36 to turn it.

The connector system of the invention, as described above, is suitable for connecting truss modules together. It will be appreciated that such a connector system may be equally suitable for connecting other structural tubular elements together. For example, it may be used when constructing handrails. The only requirement is that the structural tubular element defines an inwardly-projecting protrusion, equivalent to the inner edge of the collar 30 (as in figure 3), or the curved inner face 34 of the collars 30a to 30c of figure 9. Such an inwardly-projecting protrusion may be a feature of the structural tubular element itself, or may be provided by attaching a suitable collar, as described above. Evidently the dimensions of the connector system must be appropriate: in every case the tubular end portion of the connector system must fit into the structural tubular element, and the locking element (which corresponds to the balls 10 and 50 in the examples above) must then be able to engage with the inwardly-projecting protrusion.