This invention relates generally to the assembly of frame components such as tubes or channels of generally rectangular cross-section, and has particular, though certainly not exclusive, application to the assembly of rectangular frames such as door frames made up of metal channel sections.

The typical prefabricated cavity frame for sliding doors is presently formed in timber. These frames serve to define both the doorway and a space within the wall cavity to receive the sliding door when in the open position. This latter portion of the door frame substitutes for wall studs and normally mounts plasterboard or other cladding applied to the wall in which the frame is fixed. Because the cavity door frame effectively comprises a pair of spaced interconnected sub-frames for supporting two sides of a cavity wall, there is some merit in forming the frame from metal components which include channels defining the periphery of the frame. However, assembly of a rectangular array of inwardly open channels prima facie involves several cutting and welding steps and it is accordingly an object of the invention to provide for the angled coupling of a pair of tubes or channels in a simple and effective manner.

The invention accordingly provides, in one aspect, a tube or channel of generally rectangular cross-section and having longitudinally extending wall means defining respective sides of the tube or channel, wherein, adjacent at least one end of the channel and in one of the wall means, is disposed a transversely extending slot and a complementary tab which terminates a portion of the wail means, wherein the slot and tab are transversely aligned and are positioned and adapted to respectively engage a tab and slot of a similar tube or channel whereby to couple the tubes or channels in angular relationship.

In an embodiment, a channel is provided in which the wall means provided with the slot and tab comprises a pair of longitudinally extending lips defining a channel opening between them. In this case, the slot is formed in one of the lips and the complementary tab in the other, the tab terminating this lip.

For effective engagement, the tab is out-turned with respect to the tube or channel, but may be more conveniently in maintained substantially flush with the wall means in which it is formed until it is required to couple the tube or channel with another, whereupon the tab may be bent outwardly.

Preferably, the aforementioned angular relationship is a right-angular relationship with the respective wall means in which the tab and slot are formed being those on the inside of the angle.

In a further aspect, the invention is directed to a combination of a pair of tubes or channels according to the first aspect of the invention, coupled in angular relationship.

In a preferred application, the invention further affords a frame, e.g. a cavity door frame, including at least one upright, a top rail and a bottom rail in which the upright and the top and bottom rails comprise channels according to the first aspect of the invention, the rails being coupled to the upright in respective right angular relationships in which the channels open inwardly of the frame.

The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a cavity door frame, depicted in situ and incoφorating an upright and top and bottom rails according to an embodiment of the invention;

Figure 2 illustrates a pair of similar channels prior to their interengagement;

Figure 3 is a partial plan view of the steel metal blank from which the channel is rolled; Figure 4 is a partial cut-away end view of the channels overlaid ready for interengagement;

Figure 5 is a view similar to Figure 4 but showing the completed coupling in right- angular relationship;

Figure 6 is a side view of a second embodiment of a sliding door frame constructed in accordance with the invention;

Figure 7 is a schematic sectional view along the line 7-7;

Figure 8 is an enlarged cross-sectional view along the line 8-8;

Figure 9 is a schematic cross-sectional view along the line 9-9;

Figure 10 is a schematic sectional view along the line 10-10; Figure 11 is a fragmentary perspective view of a pair of uprights; Figure 12 is a fragmentary perspective view of an end of the top rail; Figure 13 shows how the end of the top rail interlocks with the pair or uprights; Figure 14 is a fragmentary view showing one of the uprights and a cross beam;

Figure 15 shows the upright and cross beam interlocked together; and Figure 16 is a fragmentary sectional view along the line 16-16.

The cavity door frame 10 illustrated in Figure 1 includes an upright 12, a longer top rail 14 and a shorter bottom rail 16. These three components of the frame are rolled steel channels of similar cross-section. The rails are coupled at right angles to the respective ends of upright 12, and the other end of the bottom rail 16 is also linked to top rail 14 at an intermediate position by a pair of spaced steel plates 18, 19. These plates are in turn linked to upright 12 by respective side rails 20, 21.

The overhanging portion of top rail 14 bounds the door opening 23 and the space defined between upright 12, plates 18, 19 and side rails 20, 21, is a door cavity 22 to receive the sliding door panel when in its open position. In situ, the whole frame is fastened to the floor, to an overhead lintel 26 and to spaced wall studs 28, 29. Plasterboard or other wall cladding would typically be mounted to either side of the frame 10 to cover the cavity 22.

The side rails 20, 21 are fixed to upright channel 12 and to upright plates 18, 19, and the latter are connected to the top and bottom rails 14, 16, by a tab and slot lock mechanism

25 similar to that described in Australian Patent Application No. PN4134/95 in respect of an invention entitled "Fence Post and Rail Combination". The contents of that specification is incorporated herein by cross-reference.

With particular reference to Figure 2, each of the channels 12, 14, 16 is a rolled steel rail with a back web 30, side flanges 32, 33 and respective narrow frontal lips 34, 35 extending longitudinally along the outer edges of flanges 32, 33. These lips define a channel opening 11 between them and each in turn has a fine return leg 36. At each end of upright 12 and at at least one end of rails 14, 16, a similar coupling configuration is provided. One of the lips 34 has a transverse slot 40 displaced from the end of the channel by a distance substantially

equal to the depth of the channel, i.e. the width of each flange 32, 33. In transverse alignment with this slot, i.e. at the same distance from the end of the channel, the other lip 35 is terminated by an upwardly projecting tab 42.

Figure 3 is a partial plan view of a suitable sheet steel blank 12' from which a channel such as channels 12, 14, 16 may be roiled by folding on the broken lines depicted. Elements corresponding to features of the rolled channel are indicated by like primed reference numerals. The end of the blank 12' is subjected to a cutting operation to form slot 40' and tab 42'. Tab 42' is formed by cutting along the fold lines 44, 46 between flange 33 ' and lip 35' and at leg 36' back to a position transversely aligned with slot 40 ' and then cutting off the leg 36' to that position and the lip 35' to a shorter point, thereby leaving tab 42'.

A pair of thus configured channels are shown in opposed alignment in Figure 2, with the respective tabs 42 turned outwardly substantially at right angles to the channels. The join can then be formed by first overlying and then abutting the channels as shown in Figure 4 so that the respective tabs 42 project into the complementary slots 40 of the other component. There is sufficient transverse movement possible, arising from the cutting formation of the tabs, that the two channels can be relatively rotated apart about an axis at the aligned slots to bring the assembly to the coupled position shown in Figure 5. In this motion, tabs 42 swing around under the adjacent lip and the flanges of the respective channels at opposite sides are able to swing around and be accommodated behind the associated flanges of the other channel in the space 41 created by the cutting off of the lips 35 at tabs 42. It will be appreciated from Figures 4 and 5 that in the completed corner assembly, the sidewall 33 of the rail 16 is outwardly adjacent to the sidewall 32 of the upright 12. Correspondingly, the sidewall 33 of the upright 12 is located outwardly adjacent to the sidewall 32 of the rail 16.

It is found that once the thus assembled metal frame is screwed into place within the timber frame, the resultant joint provides similar strength to a spot welded joint. Top rail 14 may serve as a track for wheels carried by the door panel, or may be fitted with a separate track.

Figure 6 shows a modified form of sliding door frame 50 constructed in accordance with the invention. The same reference numerals have been used to denote parts which

correspond to those of Figures 1 to 5, where appropriate.

The door frame 50 includes the top and bottom rails 14 and 16 but in this arrangement the top rail 14 is essentially the same length as the bottom rail 16. The frame also includes the 5 upright 12 and the junction between the bottom rail 16 and the top rail 14 is essentially the same as that shown in Figures 2 to 5. Similarly, the junction between the top rail 14 and the upright 12 is also of this construction. In this embodiment, however, the plates 18 and 19 are omitted and are replaced by upright channels 52 and 54 which are the mirror image of one another, as diagrammatically shown in Figures 7 and 8.

10

The channel 52 includes a jamb face 56 which defines or is adjacent to the jamb of the sliding door frame. Extending inwardly from the face 56 is a retum leg 58 which faces the door cavity 22. At the other side of the jamb face is an outer face 60 which is stepped inwardly by an inward leg 62, the leg 62 being joined with an inner face 64. The face 64 is

15 joined with an edge face 66, which is parallel to the jamb face 50, the edge face 66 being joined with a return leg 68 which is co-planar with the leg 58. The channel 54 is of a mirror image construction and need not be described.

Figure 11 diagrammatically illustrates the upper end configuration of the upright 20 channels 52 and 54. It will be seen that the upper part of the edge face 66 has been removed at the top edge to form a first slot 70. A second portion of the edge face 66 has been also removed to form a first opening 72 located somewhat below the slot 70. A similar siot and opening 74 and 76 are formed in the edge face 66 of the second upright channel 54. The slots and openings in the uprights 52 and 54 form an interlock with the adjacent end of the top rail 25 14, as will be described below.

Figure 12 shows the end of the top rail 14 adjacent to the upright channels 52 and 54. In this configuration, slots 78 and 80 are removed from the ends of the flanges 32 and 33 so as to define projections 82 and 84 respectively. The slots 78 and 80 also define projecting legs 30 86 and 88 but these are contiguous with the web 30.

As best seen in Figure 13, the dimensions are such that the end of the top rail 14 can interlock with the formations on the upright channels 52 and 54. More particularly, the

projections 82 and 84 are received snuggly within the openings 72 and 76 respectively. Further, the projecting legs 88 and 86 are received within the slots 70 and 74 respectively. The lengths of the slots 80 and 78 are such that the end of the top rail 14 abuts or lies adjacent to the faces 62 of the upright channels 52 and 54. This provides a neat and robust interconnection of the top rail 14 with the upper ends of the upright channels 52 and 54. A similar interlocking is effected between the lower rail 16 and the lower ends of the upright channels 52 and 54.

In the door frame 50, a number of horizontal beams 90 are provided to extend between the upright 12 and the upright channels 52 and 54. Figures 14 to 16 diagrammatically illustrate the manner in which one end of one of the beams 90 interlocks with the upright channel 52.

A similar technique can be used for interlocking with the other upright channel 54 as well as the upright 12.

It will be seen in Figure 14 that the beam 90 comprises a C-channel having a web 92, inwardly directed sidewalls 94 and 96 and return legs 98 and 100. At the end of the beam where the interlock is to be formed, the sidewalls 94 and 96 and return legs 98 and 100 are removed so that the terminal portion 102 of the web 90 can be used as a mounting plate. The terminal portion 102 overlies the inner face 64 of the upright channel 52 and its length is such that its free end 104 lies adjacent to the face 62. The terminal portion 102 has an integral clip 106 formed generally centrally thereof. The clip 106 extends inwardly of the channel, as is shown in Figure 16. The face 64 of the upright channel 52 is formed with an integral pressed out recess 108 to receive the clip 106. An interlock between the terminal portion 102 and the channel 52 is effected by causing the free edge of the clip 106 to enter the recess 108 and then be moved downwardly so as to form and interlock therewith, as generally illustrated in Figures 15 and 16. The other end of the beam 90 is formed with a similar clip and the wall 32 of the upright 12 is formed with openings which correspond to the recess 108. Although it is not shown in the drawings, similar beams 90 can be provided on the other side of the framework 50 so as to interconnect the sidewall 33 of the upright 22 with the upright channel 54.

Vertical bracing members (not shown) can also be provided to interconnect the adjacent beams 90. The vertical bracing members can be interlocked with the beams 90 by the use of integral clips which are the same or similar to those illustrated in Figures 14 to 16.

The described arrangements have been advanced merely by way of explanation any many modifications may be made thereto without departing from the spirit and scope of the invention which includes every novel feature and combination of novel features herein disclosed.

Throughout this specification, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to impiy the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.