"AN IMPROVED PURLIN STRUT" The present invention relates, in general, to improvements in struts for use in conjunction with purlins and the like constructional elements, and to an improved building technique using such struts. More particularly, but not exclusively, the invention relates to an improved form of purlin strut, particularly suited for use in the construction of a roofing system of any known type. It should be realized, however, that the strut in accordance with the invention, and the technique associated with the use thereof, would be equally suitable for use in any situation or context where purlins or the like are to be arranged in an in-line configuration. In accordance with prior art techniques, in the construction of a support for a roof or the like an arrangement of principal rafters, purlins, common rafters, bridging elements and tie rods are employed. In accordance with known techniques the purlins, bridging elements, tie rods etc. are adapted to be appropriately located on the principal rafters for supporting common or subsidiary rafters adapted to support the roof covering itself. Interconnection between the various elements employed in accordance with the known techniques, such as for example between mating or in-line purlins and, more importantly, between purlins and bridging members and purlins and tie rods, is normally achieved by means of bolts and the like fixing means. More specifically the purlins are provided with pre-drilled holes or apertures adapted to co-operate with corresponding holes or apertures on the bridging members and to receive and retain bolts and the like fixing means. Manual means are generally employed for bolting together the purlins and associated bridging members and the rods. Nowadays, in accordance with D.L.I, safety requirements, workmen installing such purlins and associated struts or bridging members and tie rods must operate from within an internal scaffolding structure. Such scaffolding structures are, by their very nature, expensive in both terms of their availability and their ease of operation. More specifically, internal scaffolding of the type now in use, generally hired by the builder, involve that builder in substantial extra expense in terms of hiring cost. Furthermore, and perhaps in a more practical sense, it should be realised that the manual installation and tightening of a significant number of purlins and struts, by means of bolts and the like fixing means, can involve the expenditure of a substantial number of manhours in labour. In the result, therefore, the prior art techniques, which involve the use of additional equipment, can be seen to give rise to substantial expense in terms of both time and cash outlay. The present invention seeks to overcome this rather significant practical disadvantage associated with the prior art by providing a method of construction, and a component for use in such a method, which reduces substantially the number of manhours likely to be involved in erection of a system of rafters, purlins, struts or bridging members and tie rods.

In accordance with a first aspect of the present invention, therefore, there is provided a purlin strut adapted for the interconnection, without need for any additional fixing means, of adjacent pairs of purlins, said strut including: a strut tie piece; a first end member associated with said tie piece, said first end member including at least one projecting lug member adapted, in use, to be located within an aperture provided on or in one of said purlins; and a second end member for said tie piece, said second end member including means for releasably engaging with and retaining said at least one lug member of the other of said purlins.

In accordance with^' a further,aspect of the present invention there is provided a method of interconnecting adjacent pairs of purlins in a building structure, using a purlin strut of the type referred to in the preceding paragraph.

In order that the invention may be more clearly understood and put into practical effect there shall -now be described in detail a preferred technique of construction, and a preferred form of purlin strut or bridging member, in accordance with the invention. The ensuing description is given by way of non-limitative example only and is with reference to the accompanying--drawings, wherein:-

Fig. 1 represents a perspective view, from above, of a purlin strut or bridging member in accordance with the present invention;

Fig. 2 is a top plan view of the purlin strut of Fig. 1;

Fig. 3 is a side elevational view of the purlin strut of Fig. 1;

Fig. 4 is an exploded view of a first end portion of the purlin strut of Fig. 1;

Fig. 5 is a similarly exploded view of a second end portion of the purlin strut of Fig. 1; Fig. 6 is a view from above of an arrangement in accordance with the present invention showing a first purlin interconnected with an adjacent or second purlin via a purlin strut in accordance with the invention; and Fig. 7 is a side elevational view of the -it-

arrangement in Fig. 6.

As a preliminary point it should be realized that the purlin strut in accordance with the present invention will be equally suitable for use with so-called C-section purlins, Z-section purlins or indeed purlins of any other cross-sectional shape. It must be realized, therefore, that the purlin strut in accordance with the present invention is not in any way to be considered to be restricted to use with a purlin of a particular cross-sectional shape.

In accordance with a preferred embodiment of the present invention there is provided, as illustrated in Figs. 1, 2 and 3 for example, an improved form of purlin strut or bridging member, generally designated 1. The purlin strut 1 itself may be of any overall length dependent upon the length of strut tie piece 2 employed, this in turn being dependent upon the intended^usage. The purlin strjut tie piece 2 as . illustrated includes, at a first end thereof, what might be termed a double lug end member 3. In the preferred embodiment illustrated the so-called double lug end member 3 is in the form of a substantially right-angled section having upper and lower lugs 4 and 5 formed therein, those lugs 4 and 5 having apertures 6 extending therethrough for a purpose to be described in more detail hereinafter. The lug end member 3 is adapted to be connected to the purlin strut 1 itself, or more correctly the tie piece 2 thereof, in any known mannner, as for example by means of welding. It must be realized, however, that in a practical sense any means of interconnection of the lug end member 3 and the purlin strut tie piece 2 may be utilised. Alternatively, perhaps, the lug end member 3 could be formed integrally with the strut tie piece 2, although such a configuration could be expected to give rise to problems in terms of fabrication etc.

At the other free end of the purlin strut tie piece 2 there is provided what is termed a double-hook end member 7 of the type illustrated. In like manner to the double-lug end member 3 this double-hook end member 7 is adapted to be connected to the strut tie piece 2 itself in any known manner, as for example by welding. Preferably the hook portions 8, 9 of that double-hook end member 7 will be disposed at an angle to the strut tie piece 2, whereby to assist in assembly and at the same time make disassembly difficult. Preferably the upper-most hook portion or pin 8 is somewhat longer than the lowermost hook portion or pin 9 whereby to allow for more ready engagement in the respective top or upper lug 4 of an adjacent mating purlin strut 1.

The improved technique of construction in accordance with the present invention, utilizing the aforementioned purlin strut, will now be described in more detail.

Once an array of principal rafters has been constructed, using known building techniques, arrays of purlins will be required to be laid horizontally thereacross and connected together in any known manner, again in accordance with known techniques. For purposes of bracing the purlin system thus formed a plurality of purlin struts in accordance with the present invention will be employed at appropriately spaced-apart positions along the length of the purlin system itself. More specifically, purlin struts in accordance with the present invention will be adapted for location at spaced-apart intervals between adjacent rows of purlins. To this end, and as illustrated in Figs. 6 and 7, the or each purlin 10 of a first row or line of purlins is provided with a plurality of apertures 11 adapted, in use, to receive the protruding lug members 4, 5 of a purlin strut 1 in accordance with the invention.

For ease of explanation the principle of operation and installation of a purlin strut in accordance with the present invention will be described in a situation where three adjacent rows of purlins are to be interconnected, those rows being identified hereinafter as the first, second and third rows respectively.

A first purlin strut is appropriately located between adjacent members of said first and second rows of purlins, with the lugs 4, 5 protruding through the apertures of a purlin of said second row 11. A second purlin strut is then located between the second and third rows of purlins, adjacent the first strut, and "jockeyed" or moved into a position wherein the hook portions 8, 9 of that second strut can be passed ^' - through or located within the apertures 6 of the lugs 4, 5 of the first strut as protruding through the apertures 11 of said purlin of said second row. In this regard the fact that the hook portions 8 and 9 are preferably disposed at an angle to the tie piece 2 proves to be of assistance in such location. The second purlin strut can then be turned or further moved so as to be disposed between the send and third rows of purlins, with the lugs thereof protruding through the apertures 11 provided in the corresponding purlin of the third row. Once thus disposed the strut will be effectively locked in position between the second and third row of purlins. A similar procedure can then be repeated with adjoining rows of purlins as desired and required.

In such a manner an array of interconnected purlins and purlin struts may be built up, as illustrated for example in Figs. 6 and 7. Interconnection of adjacent purlin struts with an associated purlin can therefore be seen to be achieved without the need for bolts or fixing means of any type, thereby giving rise to a substantial reduction in installation time. This in itself gives rise to significant savings in overall construction cost for any give structure.

Finally, it is to be understood that the aforegoing description refers merely to preferred embodiments of the present invention, and that variations and modifications are possible thereto without departing from the spirit and scope of the invention, the ambit of which is to be determined from the following claims.