Connector for a framework structure
BACKGROUND OF THE PRESENT INVENTION 
     This invention relates to connectors of a type suitable for connecting together elongate members to form a framework structure which may be used, for example, as a display structure or a framework structure. 
     SUMMARY OF THE PRESENT INVENTION 
     According to one aspect of the invention, there is provided a first group of at least four projections extending outwardly from a main body, and are equi-angularly spaced about an axis normal to a plane parallel to the direction in which each projection of the first group extends from the main body, and a second group of at least four projections extending outwardly from the main body and being equi-angularly spaced about the axis, the projections of the second group each extending at between 15° and 75°, and preferably at 45° or substantially 45°, to the aforesaid plane. 
     Preferably each projection is of non-circular cross-section. 
     Preferably, there is an equal number of projections in the first and second groups and the projections of the second group are angularly staggered by half the angle between adjacent projections of the first group about the axis relative to the projections of the first group. 
     Conveniently, the main body includes a cylindrical or substantially cylindrical surface portion from which the first group of projections extend and a partial spherical or substantially spherical end portion adjoining the cylindrical portion and from which the second group of projections extend. 
     Advantageously, each projection is of triangular or substantially triangular cross-section. In this case, preferably, a flat or a substantially flat portion is provided at the junction between each pair of adjacent sides of each triangular or substantially triangular projection. 
     Conveniently, the projections and body of the connector are made of non-flexible plastics material. 
     According to a second aspect of the invention there is provided a framework structure including a plurality of elongate members having a tubular shape at least at their ends. The plurality of elongate members are interconnected by connectors according to the first aspect of the invention. 
     Preferably, the elongate members are tubes and are made of deformable plastics material. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be more particularly described with reference to the accompanying drawings, wherein: 
     FIG. 1 is a perspective view of one embodiment of a connector according to the invention; 
     FIG. 2 is an end view of the connector of FIG. 1; 
     FIG. 3 is a cross-sectional view showing a tube mounted on a projection of the connector of FIGS. 1 and 2; and 
     FIG. 4 is a schematic view showing a plurality of elongate members connected together by connectors of FIGS. 1 through 3 to form a space frame. 
    
    
     Referring to FIGS. 1 through 4 of the drawings, the connector shown therein includes a body part 10 having a cylindrical surface portion 12 and a part-spherical end portion 14 which adjoins the cylindrical surface portion 12. The other end portion of the body part will be referred to later. A first group of four projections 16 extend outwardly from the cylindrical surface portion 12 and are equi-angularly spaced about an axis 18 of the cylindrical surface portion 12. The projections 16 extend in a common plane which is normal to the axis 18. A second group of four projections 20 extend outwardly from the part-spherical end portion 14 of the body part 10. These projections 20 are also equi-angularly spaced about the axis 18 but are angularly staggered by 45° about this axis relative to the projections 16. Also the projections 20 extend at an angle of between 15° and 75°, and preferably at 45°, to the common plane. 
     Each projection 16 or 20 is of non-circular cross-section and ideally is of substantially triangular cross-section as shown. Each projection 16 or 20 has a flat 22 at the junction between each pair of sides. Each flat 22 may be slightly convex. 
     Each projection has two sides 24 of equal length and a side 26 of shorter length. Each side 26 has a concave recess. 
     The other end of the connector is provided with an axially inwardly extending annular groove 28 (see FIG. 2) which may receive the end of a tube serving as a vertical support column. As shown this other end of the connector is also provided with an integral, hexagonal nut 30. 
     The connector is conveniently formed from non-flexible plastics material, such as that sold by I.C.I. under the Trademark `Noryl`. 
     A plurality of such connectors can be used to connect together elongate members in the form of deformable plastics cylindrical tubes 32 (see FIG. 4) to form a space frame which may be used, for example, as a display stand. In order to locate a tube 32 on a projection 16 or 20, an end of the tube 32 is deformed, by hand pressure, is pushed over the projection and is then released. The inner wall of the tube is engaged by each of the three flats 22 of the projection as an interference fit (see FIG. 3). 
     In the above embodiment the projections are described as being of non-circular cross-section and while this is highly desirable, it is conceivable that they could be of circular cross-section. 
     Instead of the tubes 32, solid rods, with cylindrical deformable plastics sockets at each end, could be used. 
     The connectors and tubes described above could be scaled down for use as a toy or an architect&#39;s model. 
     If desired, the tubes 32 could be heat welded to the projections 16 or 20 in order to provide a permanent installation or, if the tubes 32 and connectors are of the same material, the tubes may be secured to the projections of the connectors by adhesive. 
     Moreover, the partially spherical end portion may have grooves formed therein, each groove joining a diametrically opposite pair of projections 16 and acting in conjunction with the concave recesses in the sides 26 of the associated projections 16 as a location for a cable which can run through the tubes. 
     What is claimed as novel is as follows: