Pacione, Gianni (C/- Hayes Steel Framing Systems Pty Ltd, 4 Alvis Place Ingleburn, New South Wales 2565, AU)
| 1. | An elongate framing member (2, 3, 6) having a transverse C or U shaped cross section which is substantially constant along the length of the framing member, the framing member having first and second substantially planar and mutually parallel side walls (12, 14, 16) which extend in a common direction from respective opposite edges of a substantially planar base wall (13, 15, 17), at least one of the three walls having a first throughhole (20, 21, 30, 32) which is surrounded by an offset portion (50, 51) of the respective wall, the offset portion being offset out of the general plane of the respective wall. |
| 2. | An elongate framing member as claimed in claim 1, wherein the first through hole is circular and the offset portion is annular and concentric with the first through hole. |
| 3. | An elongate framing member as claimed in claim 1 or claim 2 wherein the first through hole is in the base wall and the offset portion is offset in the common direction. |
| 4. | An elongate framing member as claimed in claim 1 or 2, wherein the first throughhole is in the first side wall, and the second side wall has a second throughhole which is transversely aligned with the first throughhole. |
| 5. | An elongate framing member as claimed in claim 4, wherein the second throughhole is surrounded by an offset portion of the second side wall, the offset portion of the second side wall being offset out of the general plane of the second side wall. |
| 6. | An elongate framing member as claimed in claim 5, wherein the second throughhole is circular and the offset portion of the second side wall is annular and concentric with the second throughhole. |
| 7. | An elongate framing member as claimed in claim 5 or 6, wherein the offset portion of the second side wall is offset toward the first side wall. |
| 8. | An elongate framing member as claimed in any one of claims 4 to 7, wherein the offset portion of the first side wall is offset toward the second side wall. |
| 9. | A pair of elongate framing members (2, 6), each framing member having a transverse C or U shaped crosssection which is substantially constant along the length of the framing member, each framing member having a pair of first and second substantially planar and mutually parallel side walls (12, 14) which extend in a common direction from respective opposite edges of a base wall (13, 15), the first and second side walls of each framing member being spaced apart by approximately the same distance, and each framing member having a pair of first and second transversely aligned throughholes (20, 21) in the respective first and second side walls, wherein the two framing members are assembled together with the two side walls at a portion of the first framing member lying between the two side walls at a portion of the second framing member. |
| 10. | A pair of elongate framing members as claimed in claim 9, wherein the framing members are fixed together by a threaded nut (26) and bolt (24), the bolt having a shank which passes through at least one of the first and second throughholes of each of the first and second framing members. |
| 11. | A pair of elongate framing members as claimed in claim 10, wherein the shank passes through both the first and second throughholes of each of the first and second framing members. |
| 12. | A pair of elongate framing members as claimed in claim 11, wherein a sleeve (22) is fitted over the shank, the sleeve lying between the first and second walls (14) of the first framing member (6), and the sleeve having a length that is substantially the same as the distance between the first and second side walls (14) of the first framing member (6). |
| 13. | A pair of elongate framing members as claimed in claim 12, wherein the sleeve is circularly cylindrical, the bolt has a head, and at least one of the head and the nut has a circular flange which abuts against an outer face of one of the side walls of the second framing member, the flange having a diameter that is substantially the same as or greater than the outer diameter of the sleeve. |
| 14. | A pair of elongate framing members as claimed in claim 12 or 13, wherein the bolt has a head, and at least one substantially circular washer (28) is fitted on the shank, either inside of the head or inside of the nut, to abut against an outer face of one of the side walls of the second framing member, the washer having an outer diameter that is substantially the same as or greater than the outer diameter of the sleeve. |
| 15. | A pair of elongate framing members as claimed in any one of claims 9 to 14, wherein the first throughhole in each pair of side walls is surrounded by an offset portion of the respective first side wall and the offset portion is offset out of the general plane of the respective first side wall, and the offset portions of the respective framing members are offset in a common direction and are in mutual nesting engagement one inside the other. |
| 16. | A pair of elongate framing members as claimed in claim 15, wherein, in each pair of side walls, the second throughhole is surrounded by an offset portion of the respective second side wall and the offset portion of the respective second side wall is offset out of the general plane of the respective second side wall, and the offset portions of the second side walls of the respective framing members are offset in a common direction and are in mutual nesting engagement one inside the other. |
| 17. | A pair of elongate framing members as claimed in claim 15 or 16, wherein, in each pair of side walls, the first and second throughholes are circular and the offset portion of the first side wall is annular and concentric with the first throughhole. |
| 18. | A pair of elongate framing members as claimed in claim 17, wherein, in each pair of side walls, the offset portion of the second side wall is annular and concentric with the second throughhole. |
| 19. | A pair of elongate framing members as claimed in claim 16, 17 or 18, wherein, in each pair of side walls, the offset portion of the second side wall is offset toward the first side wall. |
| 20. | A pair of elongate framing members as claimed in any one of claims 15 to 19, wherein, in each pair of side walls, the offset portion of the first side wall is offset toward the second side wall. |
| 21. | A pair of elongate framing members as claimed in claim 19 or 20 when dependent upon claim 12, 13 or 14, wherein the offset portions of the first side walls of the first and second framing members are circular, and the sleeve is circularly cylindrical and has an internal diameter that is substantially the same as, but not less than, the outer diameters of the offset portions of the first side walls. |
| 22. | A method of assembling a pair of framing members in a predetermined configuration, each framing member being elongate and having a transverse C or U shaped crosssection which is substantially constant along the length of the framing member, each framing member having a pair of first and second substantially planar and mutually parallel side walls which extend in a common direction from respective opposite edges of a base wall, the first and second side walls of each framing member being spaced apart by approximately the same distance, the method including the steps of: (a) forming first and second transverselyaligned throughholes at predetermined locations in the respective first and second side walls of each framing member, (b) forming an offset wall portion surrounding the first throughhole in each framing member, each offset portion being offset out of the general plane of the respective first side wall, and (c) assembling the pair of framing members with the first and second side walls at a portion of the first framing member lying between the first and second side walls at a portion of the second framing member, and with the offset portions of the respective framing members offset in a common direction and in mutual nesting engagement one inside the other. |
| 23. | The method of assembling a pair of framing members as claimed in claim 22, the step (c) being preceded by the further step of: (d) forming an offset wall portion surrounding the second throughhole in each framing member, each offset portion of the second side walls being offset out of the general plane of the respective second side wall, so that when the framing members are assembled in step (c) the offset portions of the second side walls of the respective framing members are offset in a common direction and are in mutual nesting engagement one inside the other. |
| 24. | The method of assembling a pair of framing members as claimed in claim 22 or 23, wherein the first and second throughholes are circular and the offset portion of the first side wall is annular and concentric with the first throughhole. |
| 25. | The method of assembling a pair of framing members as claimed in claim 24, wherein, in each pair of side walls, the offset portion of the second side wall is annular and concentric with the second throughhole. |
| 26. | The method of assembling a pair of framing members as claimed in claim 23, 24 or 25, wherein, in each pair of side walls, the offset portion of the second side wall is offset toward the first side wall. |
| 27. | The method of assembling a pair of framing members as claimed in any one of claims 22 to 26, wherein, in each pair of side walls, the offset portion of the first side wall is offset toward the second side wall. |
| 28. | The method of assembling a pair of framing members as claimed in any one of claims 22 to 27, including the further steps of: (e) inserting the shank of a threaded bolt through at least the first or second throughholes of both the first and second framing members after assembly of the framing members in step (c), and (f) threading a mating nut onto the bolt shank to fix the framing members together. |
| 29. | The method of assembling a pair of framing members as claimed in claim 28, wherein in step (e), the shank is passed through both the first and second throughholes of both the first and second framing members. |
| 30. | The method of assembling a pair of framing members as claimed in claim 29, including the additional step of: (g) fitting a cylindrical sleeve fitted over the shank so that the sleeve lies between the first and second walls of the first framing member, the sleeve having a length that is substantially the same as the distance between the first and second side walls of the first framing member. |
| 31. | The method of assembling a pair of framing members as claimed in claim 30, wherein the bolt has a head and the method includes the additional step of: (h) fitting respective substantially circular washers concentrically on the shank inside of the head and inside of the nut to abut against outer faces of the first and second side walls of the second framing member. |
FIELD OF INVENTION
The present invention relates to framing members and particularly to elongate framing members having a generally U or C shaped cross section, and more particularly to such framing members made using rolled or folded sheet material, for example sheet steel, and to the inter-connection of such framing members. One application of the present invention is in structural frames, for example roof trusses, for residential and light commercial buildings.
BACKGROUND
It is known to fabricate steel framing, for construction of buildings, by roll forming galvanised steel sheet into framing members, typically having C or U shaped cross- sections. Members are connected together by fasteners, such as screws or nut and bolt sets, to form framing systems, such as vertical walls or roof trusses, for example. Such framing systems can be readily designed and built to have a predictable and consistent performance with a high strength-to-weight ratio.
United States Patent No. 4,982,545 (Stromback) describes a steel truss having a U shaped lower chord facing upward and a U shaped upper chord facing downward. Edges of the lower chord have a flat reinforcing flange allowing the lower chord to slide into the upper chord. Webs are fitted into the upper and lower chords. The trusses are formed by driving self tapping screws into each side of the joints between chords, and between chords and webs.
United States Patent No. 5,463,837 (Dry) describes a metal roof truss for a building construction. Each of the top and bottom chord members of the truss is of a U shaped cross-section, with the outer edge of each leg of the U-shape having a radiused or rolled hem to provide stiffening to the members. The U-shaped chords are interfitted to form
a truss, with the relatively thin-gauge steel stock allowing the legs to flex so that the chords fit together.
United States Patent No. 5,722,210 (Baker et al) describes a generally triangular truss comprising a horizontal lower chord and a pair of inclined upper chords. The chords are joined by single pin connections which are preferably made by a bolt, two washers and a nut. In one preferred arrangement the bolt is fitted in a press-fit sleeve. The truss chords, which are made using engineered lumber substitutes, and other truss elements are assembled on site to create a truss of a defined shape using the nut and bolt combinations to provide specifically placed pivotal joints.
United States Patent No. 5,901,522 (Slater) describes a collapsible metal roof truss using chord members of generally U shaped cross-section. The horizontal bottom chord opens upwardly and the upper chords open downwardly. Pivotal connections, which are preferably nut and bolt connections, join the chords to form a generally triangular truss. Pre-located interconnecting points of the truss components are provided by pre- drilled holes for the connecting bolts. The truss may be partially preassembled at a factory or other off-site location and transported in a collapsed form for final assembly in a predefined geometry when on site.
United States Patent No. 6,634,152 (Pilkington) describes a collapsible metal roof truss having upper and lower chords of U shaped cross-section which are pivotally interconnected at three corners. The open ends of the walls of the upper chords are directed downwards and those of the lower chord are directed upwards. The truss webs lie between, and are pivotally attached to, the walls of the upper and lower chords. A pair of co-axial stamped hinge pivots is provided at each chord-to-chord and web-to- chord pivot connection. The finished truss geometry is set by fixing together telescopic chord and web elements.
United States Patent Application No. 2002/0194811 (Shimizu et al) describes a method for assembling a structural member such as a roof or wall truss using lightweight shaped-steel members. The truss members are provided with at least one pilot hole at each joint position. The joint position is accurately indexed in advance in a factory by boring complementary pilot holes in respective truss members to define a required truss
geometry. The trass members, which may be lightweight channel shaped steel members, are provided with concave/convex portions which are recessed to protrude inward from the walls of the channel members. The concave/convex portions of respective truss members are engaged with one another to temporarily fix the truss members in the predefined geometry for permanent fixing by screws which are fastened into the pilot holes previously provided for the purpose.
International Patent Application Publication No. WO 94/15041 (Hart) describes a precision truss system comprising channel-shaped chords, posts and braces which are pivotally interconnected at separate locations using individual pins or bolts. A very tight hole-to-pin tolerance ratio allows the structural system to be precisely assembled, initially in a non-critical shape which is then progressively stabilised by connecting the brace members.
SUMMARY OF INVENTION
An object of at least one embodiment of the invention is to provide an elongate framing member, having a generally C or U shaped cross-section, with a locating means which facilitates the placing of the framing member into a predetermined relationship with another similar framing member, in preparation for fixing the framing members together, or at least to provide the public with a useful choice.
Another object of at least one embodiment of the invention is to provide a simple inter¬ connection for joining together respective elongate framing members having generally C or U shaped cross-sections.
Yet another object of at least one embodiment of the invention is to provide a method of assembling a pair of elongate framing members.
In a first aspect the invention may be broadly said to be an elongate framing member having a transverse C or U shaped cross-section which is substantially constant along the length of the framing member, the framing member having first and second substantially planar and mutually parallel side walls which extend in a common direction from respective opposite edges of a substantially planar base wall, at least one
of the three walls having a first through-hole which is surrounded by an offset portion of the respective wall, the offset portion being offset out of the general plane of the respective wall.
The first through-hole may be circular and the offset portion annular and concentric with the first through-hole.
The first through hole may be in the base wall and the offset portion offset in the common direction.
Alternatively, the first through-hole may be in the first side wall, and the second side wall may have a second through-hole which is transversely aligned with the first through-hole. The second through-hole may be surrounded by an offset portion of the second side wall, the offset portion of the second side wall being offset out of the general plane of the second side wall. The second through-hole is circular and the offset portion of the second side wall may be annular and concentric with the second through- hole. The offset portion of the second side wall may be offset toward the first side wall. The offset portion of the first side wall may be offset toward the second side wall.
In a second aspect the invention may be broadly said to be a pair of elongate framing members, each framing member having a transverse C or U shaped cross-section which is substantially constant along the length of the framing member, each framing member having a pair of first and second substantially planar and mutually parallel side walls which extend in a common direction from respective opposite edges of a base wall, the first and second side walls of each framing member being spaced apart by approximately the same distance, and each framing member having a pair of first and second transversely-aligned through-holes in the respective first and second side walls, wherein the two framing members are assembled together with the two side walls at a portion of the first framing member lying between the two side walls at a portion of the second framing member. The framing members may be fixed together by a threaded nut and bolt, the bolt having a shank which passes through at least one of the first and second through-holes of each of the first and second framing members. The shank may
pass through both the first and second through-holes of each of the first and second framing members. A sleeve may be fitted over the shank, the sleeve lying between the first and second walls of the first framing member, and the sleeve having a length that is substantially the same as the distance between the first and second side walls of the first framing member. Preferably, the sleeve is circularly cylindrical, the bolt has a head, and at least one of the head and the nut has a circular flange which abuts against an outer face of one of the side walls of the second framing member, the flange having a diameter that is substantially the same as or greater than the outer diameter of the sleeve. More preferably, the bolt has a head, and at least one substantially circular washer is fitted on the shank, either inside of the head or inside of the nut, to abut against an outer face of one of the side walls of the second framing member, the washer having an outer diameter that is substantially the same as or greater than the outer diameter of the sleeve.
The first through-hole in each pair of side walls may be surrounded by an offset portion of the respective first side wall and the offset portion may be offset out of the general plane of the respective first side wall, the offset portions of the respective framing members being offset in a common direction and in mutual nesting engagement one inside the other.
Optionally, in each pair of side walls, the second through-hole is surrounded by an offset portion of the respective second side wall and the offset portion of the respective second side wall is offset out of the general plane of the respective second side wall, and the offset portions of the second side walls of the respective framing members are offset in a common direction and are in mutual nesting engagement one inside the other.
In each pair of side walls, the first and second through-holes are preferably circular, and the offset portion of the first side wall annular and concentric with the first through- hole. Also, the offset portion of the second side wall may be annular and concentric with the second through-hole. In each pair of side walls, the offset portion of the second side wall is preferably offset toward the first side wall, and the offset portion of the first side wall is preferably offset toward the second side wall. Preferably the offset
portions of the first side walls of the first and second framing members are circular, and the sleeve is circularly cylindrical and has an internal diameter that is substantially the same as, but not less than, the outer diameters of the offset portions of the first side walls.
In a third aspect the invention may be broadly said to be a method of assembling a pair of framing members in a predetermined configuration, each framing member being elongate and having a transverse C or U shaped cross-section which is substantially constant along the length of the framing member, each framing member having a pair of first and second substantially planar and mutually parallel side walls which extend in a common direction from respective opposite edges of a base wall, the first and second side walls of each framing member being spaced apart by approximately the same distance, the method including the steps of:
(a) forming first and second transversely-aligned through-holes at predetermined locations in the respective first and second side walls of each framing member,
(b) forming an offset wall portion surrounding the first through-hole in each framing member, each offset portion being offset out of the general plane of the respective first side wall, and (c) assembling the pair of framing members with the first and second side walls at a portion of the first framing member lying between the first and second side walls at a portion of the second framing member, and with the offset portions of the respective framing members offset in a common direction and in mutual nesting engagement one inside the other.
The step (c) may be preceded by the further step of:
(d) forming an offset wall portion surrounding the second through-hole in each framing member, each offset portion of the second side walls being offset out of the general plane of the respective second side wall, so that when the framing members are assembled in step (c) the offset portions of the second side walls of the respective framing members are offset in a common direction and are in mutual nesting engagement one inside the other.
Preferably, the first and second through-holes are circular and the offset portion of the first side wall is annular and concentric with the first through-hole. In each pair of side walls, the offset portion of the second side wall may be annular and concentric with the second through-hole.
Optionally, in each pair of side walls, the offset portion of the second side wall may be offset toward the first side wall, and/or the offset portion of the first side wall may be offset toward the second side wall.
Preferably, the method of assembling a pair of framing members includes the further steps of:
(e) inserting the shank of a threaded bolt through at least the first or second through-holes of both the first and second framing members after assembly of the framing members in step (c), and
(f) threading a mating nut onto the bolt shank to fix the framing members together.
In step (e), the shank may be passed through both the first and second through-holes of both the first and second framing members.
Preferably, the method of assembling a pair of framing members includes the additional step of:
(g) fitting a cylindrical sleeve fitted over the shank so that the sleeve lies between the first and second walls of the first framing member, the sleeve having a length that is substantially the same as the distance between the first and second side walls of the first framing member.
Optionally, the bolt has a head and the method includes the additional step of: (h) fitting respective substantially circular washers concentrically on the shank inside of the head and inside of the nut to abut against outer faces of the first and second side walls of the second framing member.
The invention may further be said to consist in any alternative combination of parts or features mentioned herein or shown in the accompanying drawings. Furthermore, known equivalents of these parts or features which are not expressly set out are nevertheless deemed to be included.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments and methods of utilising the invention will be further described, with reference to the accompanying figures, by way of example only and without intending to be limiting, wherein;
Figure 1 shows a side elevation of a roof truss frame,
Figure 2 shows details of one of the heel joints of the truss shown in Figure 1, fastened using a bolt and nut,
Figure 3 shows a conceptual cross-section of the chord-to-chord connection at the heel joint shown in Figure 2,
Figure 4 shows details of a web-to-chord joints of the truss shown in Figure 1, fastened using a bolt and nut, Figure 5 shows a conceptual cross-section of the web-to-chord connection shown in Figure 4,
Figure 6 shows details of a web-to-chord joint of the truss shown in Figure 1, fastened using a self-tapping screw,
Figure 7 shows a conceptual cross-section of the web-to-chord connection shown in Figure 6,
Figure 8 shows a conceptual cross-section of an alternative chord-to-chord connection at the heel joint shown in Figure 2, and
Figure 9 shows a conceptual cross-section of another alternative chord-to-chord connection at the heel joint shown in Figure 2.
It is to be noted that the conceptual cross-sections shown in Figures 3, 5, 7, 8 and 9 are not true cross-sections as might be seen in each case at a single section plane, but rather
illustrate the concept of the inter-connections between the respective chords and webs which meet at various angles. Furthermore, the conceptual cross-sections show the various components spaced apart for clarity of illustration.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to the figures it will be appreciated that the invention may be implemented in various forms and modes. The following description of a preferred embodiment of the invention is given by way of example only.
Figure 1 shows a side elevation of a roof truss 1 made up of elongate framing members. Two top chords 2, 3 are joined together by a fastening system at a truss apex 4. The two top chords are also joined respectively to the ends of a bottom chord 6 at truss heels 8, 9. The chords are reinforced by truss webs 10 which interconnect the bottom chord 6 to each of the top chords 2, 3.
The top chords 2, 3 and bottom chords 6 are each formed with a substantially common U-shaped cross-section, as seen in the thumbnail cross-sectional views shown in Figure 2 and in more detail in Figure 3. The webs 10 are each formed with a substantially common C-shaped cross-section, as seen in the thumbnail cross-sectional views of the webs shown in Figure 4 and 6 and in more detail in Figures 5 and 7. In each case the cross-section is substantially constant along the length of each chord or web.
As best seen in the cross-sections shown in Figures 3, 5, 7, 8 and 9, each top chord 2, 3 has a pair of substantially planar and mutually parallel side walls 12 which extend in a common direction from respective opposite parallel edges of a third substantially planar base wall 13, the bottom chord 6 has a pair of substantially planar and mutually parallel side walls 14 which extend in a common direction from respective opposite parallel edges of a third substantially planar base wall 15, and each web 10 has a pair of substantially planar and mutually parallel side walls 16 which extend in a common direction from respective opposite parallel edges of a third substantially planar base wall
17.
In one preferred embodiment, and as seen in the figures, the outer edges of the chord and web side walls 12, 14, 16 are rolled over to form flanges 18, 19, explained further below, for reinforcing the side walls and providing the side walls with a more user- friendly radiused or flat outer edge rather than an otherwise raw edge.
In the preferred embodiment shown, edge flanges 18 are formed on the top and bottom chords. These flanges 18 are rolled approximately 180 degrees outwardly, as seen on the side walls 12, 14 of the U-sectioned chords 2, 6 shown in Figures 2 to 8. Similarly, edge flanges 19 are formed on the webs 10. These flanges 19 are rolled approximately 90 degrees inwardly, as best seen on the side walls 16 of the C-sectioned webs 10 shown in Figures 5 and 7. The flanges can be rolled in opposite directions to those shown, or rolled with other cross-sectional shapes, for example with a circular cross- section rather than the relatively flattened flange shown in the figures.
References in this description and in the accompanying claims to a substantially or generally planar wall are to be interpreted as not excluding an otherwise planar wall having a rolled or folded flange or hem along a wall edge, and/or having localised deformations or offset dimpled portions which lie out of the general plane of the wall, and/or having a reinforcing ridge formed along the length of the wall.
In a preferred embodiment, the chords and webs are rolled into the respective U and C shaped sections, such as described above, from a strip of galvanised steel. The rolled form is cut into lengths to form discrete chords and webs. Holes and/or localised deformations are formed at predetermined locations in the side and base walls to provide framing members that can be readily assembled into a predetermined geometry at an end use site.
A typical roof truss assembly is shown in the Figure 1, by way of example. This generally triangular trass is formed by joining a pair of upper top chords 2, 3 together at the truss apex 4, and to respective ends of a lower bottom chord 6 at the two truss heels 8, 9.
The two side walls 14 of the U-sectioned bottom chord 6 are directed upward and, at the truss heels 8, 9, lie inside the two downwardly-directed side walls 12 of the respective U-sectioned top chords 2, 3. At the truss apex 4, the two side walls of one top chord 3 lie inside the two side walls 12 of the other top chord 2.
The chords are sufficiently flexible to distort slightly so that the chords and their respective pairs of similarly spaced apart side walls can be fitted together, with one pair of side walls between the other pair.
Figure 3 shows a conceptual cross-sectional view of a connection between a top chord 2 and a bottom chord 6 at a truss heel connection. An identical connection is made at the other truss heel and a similar connection made at the truss apex. Two transversely- aligned through-holes 20 are formed through the two respective side walls 14 of the bottom chord 6, at pre-determined locations adjacent each end of the bottom chord. Two transversely-aligned through-holes 21 are formed through the two respective side walls 12 of each top chord 2, 3, at two locations on each top chord, a pair of top chord through-holes being adjacent the apex end of each top chord, and another pair being inboard of the other end of each top chord 2, 3, at respective truss heels 8, 9.
At each chord-to-chord joint, a cylindrical spacer sleeve 22 is placed between the two innermost side walls 14 and the shank of a threaded bolt 24 is passed through the aligned holes and the spacer sleeve. A threaded nut 26 is fitted to the bolt shank and tightened to draw together the two side walls under the bolt head, and the two side walls under the nut, and to fasten the two respective chords together. In preferred embodiments, the spacer sleeve is made from a metal, preferably steel, or a plastic material.
To improve the strength and integrity of the chord-to-chord connection under load, a plain flat washer 28 may be located under the bolt head and/or under the nut as shown in Figure 3. Alternatively or additionally, (but not shown in the figures) the bolt head and/or the nut can be flanged.
A pre-determined truss geometry can be assured by fastening all three chord-to-chord joints in this way using holes provided at predetermined locations.
The chords of a truss are formed with substantially the same spacing between side walls, the chord U-sections deforming slightly to accommodate both side walls of one chord inside the side walls of the other.
In an alternative chord-to-chord connection (not shown in the figures), a first side wall of a first chord is located adjacent the inside of a first wall of a second chord, and the second wall of the second chord is located adjacent the inside of the second wall of the first chord.
In one version of the preferred truss embodiment shown in Figures 2 and 3, the chord- to-chord fastening bolt 24 has a shank with a length of about 20 mm and a diameter of
12 mm that is dimensioned to be a clearance fit in the 13 mm diameter through-holes
20, 21 in the chord side walls 12, 14, and inside the spacer sleeve 22. The sleeve 22 has an internal diameter of about 16 mm and a length of about 35 mm that is substantially equal to the spacing between the innermost chord side walls 14. The chord side walls 12, 14 are spaced apart by a distance of about 35 mm, and extend about 90 mm from the respective chord base wall 13, 15.
As noted above, and as best seen in Figure 1, webs 10 may be added to reinforce the basic triangular truss chord arrangement. As best seen in Figures 5 and 7, the webs 10 are formed with a C-shaped cross-section. Respective ends of the webs 10 are inserted between the side walls 12 of the top chords 2, 3 and between the side walls 14 of the bottom chord 6. In a preferred arrangement, the chords and webs have correspondingly dimensioned cross-sections; the length of the web side walls 16 being substantially the same as the spacing between the chord side walls 12, 14 so that the C-shaped webs are a neat fit between the side walls of the U-shaped chords.
A bolt and nut fastening system similar to that described above for the chord-to-chord connections (but without the spacer sleeve) is used to fasten the webs 10 to the top and bottom chords 2, 3 and 6.
Figures 4 and 5 show an example of such a web-to-chord bolt and nut fastening system, connecting an upper chord 2 to a web 10. Two transversely-aligned through-holes 30 are formed through respective side walls 12 of the upper chord 2 and a third through- hole 32 is formed through the base wall 17 of the web 10, at one end of the web. These holes are aligned and the shank of a threaded bolt 34 is passed through the aligned holes. A threaded nut 36 is fitted to the bolt shank and tightened to fasten the web and chord together.
To improve the strength and integrity of the web-to-chord connection under load, a washer (for example, a plain flat washer 38) may be located under the bolt head and/or under the nut as shown in Figure 5. Alternatively or additionally, (but not shown in the figures) the bolt head and/or the nut can be flanged.
A pre-determined truss web geometry can be assured by providing the through holes at predetermined locations.
In one version of the preferred truss embodiment shown in the figures, the web-to-chord fastening bolt 34 has a shank with a diameter of 12 mm that is dimensioned to be a clearance fit in the respective 13 mm diameter through-holes 30, 32 in the chord side walls 12 and in the web base wall 17. The web side walls are spaced apart by a distance of about 90 mm, and extend about 35 mm from the web base wall.
Figures 6 and 7 show an example of a web-to-chord connection using an alternative fastening system to the bolt and nut system described above. A first through-hole is formed through one side wall 12 of an upper chord 2, and a second through-hole is formed through the base wall 17 of a web 10, at one end of the web. These two holes are aligned and a self-tapping threaded screw fastener 40 is screwed into the aligned holes and tightened to fasten the web and chord together.
To improve the strength and integrity of this web-to-chord connection under load a washer (not shown) can be located under the screw head, or the head of the screw can be flanged (not shown).
In this web-to-chord connection, the dimensions of the through-holes are preferably such that the screw 40 is a clearance fit in the through-hole in the side wall 12 of the chord 2, while a 3.5 mm through-hole in the base wall 17 of the web 10 is sufficiently small so that the self-tapping screw 40 forms a thread in the web base wall 17, the screw then engaging the thread to pull the base wall and chord side wall into close abutment with one another.
In yet another web-to-chord connection (not shown), the through holes in the chord and web are dimensioned alike, with a diameter of 6 mm, for accommodating a rivet.
A deformation or offset can be provided in the generally planar web base wall 17 and/or in the generally planar chord side walls 12, 13. Pairs of these offsets can be engaged with one another to facilitate pre-alignment of the chords and webs into the pred- determined geometry. When associated with the fastener through-holes, the offsets facilitate alignment of the fastener through-holes prior to insertion of the fastener.
Figures 6 and 7 show a particularly preferred embodiment in which an offset 50 is provided in one side wall 12 of the chord 2, and a similarly shaped offset 51 is provided in the bottom wall 17 of the web 10. Each offset 50, 51 is a circularly annular dimple that is concentric with a respective fastener hole. Each dimple has a flat portion that is substantially parallel to, but offset out of, the general plane of the respective wall of the chord or web in which the dimple is formed.
The dimples in the U-chords can be offset in either direction, i.e. inwardly or outwardly. Preferably, the dimples are offset inwardly, i.e. the dimples in the chord side walls are offset toward the opposite side wall. For example, a top chord 2 and a bottom chord 6 can be pre-aligned by engaging the two side walls 14 of the bottom chord 6 inside the
two side walls 12 of a top chord 2, with a pair of inwardly directed male dimples in the side walls 12 of the top chord 2 projecting inside respective inwardly directed female dimples formed in the two side walls 14 of the bottom chord 6.
In this configuration, with pairs of dimples of the respective chords in mutual nesting engagement one inside the other, a pair of transversely-aligned fastener holes 20 in a bottom chord 6 is readily pre-aligned with a corresponding pair of transversely-aligned fastener holes 21 in a top chord 2 to facilitate insertion of the chord-to-chord fastener, such as a bolt 24.
For a web-to-chord connection, a dimple 50 is provided around the fastener through- hole in the side wall 12 of a chord 2, and a corresponding dimple 51 is provided in the base wall 17 of the web 10, at one end of the web. The dimples 50, 51 can be offset in either direction, i.e. inwardly or outwardly. Preferably, the dimples are offset inwardly (as shown in Figure 7), i.e. the dimple 50 in the U-chord side wall 12 is offset toward the opposite side wall 12 of that U-chord, and the dimple 51 in the web base wall 17 is offset in the common direction in which the web side walls 16 extend away from the web base wall 17.
The web and chord are pre-aligned by inserting the end of the web 10 between the two side walls 12 of the chord 2, with an inwardly directed male dimple 50 in the side wall 12 of the chord 2 projecting inside the inwardly directed female dimple 51 in the base wall 17 of the web. In this configuration, with the dimples of the chord and web in mutual nesting engagement one inside the other, the associated through-holes in the chord and web are readily pre-aligned to facilitate insertion of the web-to-chord fastener, for example the self-tapping screw 40. This web-to-chord connection can be used at each end of each web 10 to attach the web to the upper and lower truss chords 2, 3 and 6.
The fastener through-holes 20, 21 of the chord-to-chord connection using the spacer sleeve 22, described above and shown in Figures 2 and 3, and the fastener through-holes 30, 32 of the chord-to-chord connection without a spacer sleeve, described above and
shown in Figures 4 and 5, can be provided with the offset dimples described above to facilitate pre-alignment of the fastener through-holes. In the former case, where a spacer sleeve is used, the diameter of the spacer sleeve can be dimensioned so that the sleeve abuts the inside face of the offset portion of the inner side walls.
Alternatively, and as shown in Figure 8, an inwardly-directed offset or dimple 60 is provided in each side wall 14 of a bottom chord 6 and an inwardly-directed offset or dimple 61 is provided in each side wall 12 of a top chord 2. The dimples are circular and concentrically surround respective through-holes 20, 21 in the side walls. The side walls 14 of the bottom chord 6 are located between the side walls 12 of the top chord 2 with the dimples 60, 61 nested together to align the through-holes 20, 21. The shank of a bolt 24 is passed through the aligned through-holes and through a spacer sleeve 62 which is located between the side walls 14 of the bottom chord 6. The spacer sleeve 62 is provided with a sufficiently large inner diameter so that the ends of the sleeve surround the outer perimeter of the inwardly-directed dimple 60 and abut the in-plane (i.e. not offset) inner faces of the respective chord side walls 14. The inner diameter of the spacer sleeve 62 is preferably substantially the same as, and/or not less than, the outer diameter of the dimples 60 surrounded by the sleeve.
During assembly of the truss, the sleeve 22 is first engaged between the inwardly- directed dimples 60 in the side walls 14 of the bottom chord 6. The top chord 2 is slipped over the bottom chord 6 with the inwardly directed dimples 61 in the top chord side walls 12 engaging the dimples 60 in the bottom chord side walls 14 to facilitate alignment of the through-holes 20, 21. The shank of the bolt 24 is then passed through the aligned through-holes and the nut 26 attached and tightened. Flanges on the nut and bolt head, or washers 28, may be used as explained above.
In a yet further alternative, and as shown in Figure 9, an inwardly-directed offset or dimple 65 is provided in each side wall 14 of a bottom chord 6 and an inwardly-directed offset or dimple 66 is provided in each side wall 12 of a top chord 2. The dimples are circular and concentrically surround respective through-holes 20, 21 in the side walls. The side walls 14 of the bottom chord 6 are located between the side walls 12 of the top
chord 2 with the dimples 65, 66 nested together to align the through-holes 20, 21. The shank of a bolt 24 is passed through the aligned through-holes and through a spacer sleeve 67 which is located between the side walls 14 of the bottom chord 6. In this alternative, the spacer sleeve 67 is dimensioned with an inner diameter that is a clearance fit over the shank of the bolt 24, so that the ends of the sleeve abut the inner faces of the offset dimple 65 of the respective chord side walls 14.
For clarity of illustration the conceptual cross-sections of Figures 3, 5, 7, 8 and 9 show the various components spaced apart and with exaggerated clearances. In practice, the chords and webs are secured together by tightening the fasteners to draw the components together, and in some cases slightly deforming the components. For example, when the flanged side walls 12, 14 shown in Figures 3, 8 and 9 are drawn together into close abutment by tightening the nut 26 on the bolt 24, the side walls 12, 14 will bend slightly to accommodate the thickness of the flanges 18 on the side walls 14.
After initial pre-alignment and fixing of the truss geometry, additional fasteners can be fitted at any one or more of the chord-to-chord or web-to-chord connections to provide additional strength. For example, and as shown in Figures 6 and 7, additional screws 52 can be added at the overlap between a chord side wall 12 and a web base wall 17. The additional screws can be self-drilling and self-tapping screws that drill a pilot hole in the chord and web walls and then form a screw thread in the pilot hole.
The foregoing describes the invention with reference to a preferred embodiment. Alterations and modifications as will be obvious to those skilled in the art are intended to be incorporated within the scope of the invention as defined in the accompanying claims.
For example, although the preferred embodiment described above is a roof truss, the features of the connections described above can also be applied to corresponding connections between similar members of other frame constructions, for example in wall frames at connections between studs and plates, lintels, noggins or dwangs.
Furthermore, although pre-alignment of a chord-to-chord connection is described above by nesting dimples provided on opposite side walls of both chords, a chord-to-chord connection can be pre-aligned by nesting together dimples provided on only one side wall of each chord, or by locating a dimple provided on a side wall of one of the chords inside an appropriately-sized through-hole in a side wall of the other chord.
LIST OF FEATURES LABELLED IN THE FIGURES
roof trass 1 top chord 2, 3 truss apex 4 bottom chord 6 truss heel 8, 9 truss web 10 top chord side wall 12 top chord base wall 13 bottom chord side wall 14 bottom chord base wall 15 web side wall 16 web base wall 17 chord side wall edge flange 18 web side wall edge flange 19 bottom chord through-hole 20 top chord through-hole 21 spacer sleeve 22 bolt 24 nut 26 washer 28 upper chord through-hole 30 web through-hole 32 bolt 34 nut 36 washer 38 screw 40 chord wall dimple 50 web wall dimple 51 screw 52 dimple 60
chord wall dimple 61 spacer sleeve 62 chord wall dimple 65 chord wall dimple 66 spacer sleeve 67