Joints and connections – Member ends joined by inserted section – Externally bridged
Reexamination Certificate
1999-04-26
2001-10-09
Browne, Lynne H. (Department: 3629)
Joints and connections
Member ends joined by inserted section
Externally bridged
C411S457000, C411S467000, C052S092100, C052SDIG006
Reexamination Certificate
active
06299378
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the manufacture of wooden structures such as roof and floor trusses, where structural members such as webs and chords are attached by means of metal connector plates, consisting of plates from which have been struck a pattern of projecting teeth which are driven into the members to effect the joint. The invention also relates to connector plates for use in the manufacture of such members. The invention is particularly applicable to the location and attachment of webs to chords in the manufacture of wooden roof trusses.
BACKGROUND ART
Various procedures are used in the assembly and fixing of trusses. In one approach. the chords are laid out and connected, then the webs are positioned and stapled to the chords to maintain their position while connector plates are applied successively to each side of each joint. The plates are driven home by pressing. The need for a stapling operation at each joint adds to the assembly time, as does the positioning of the underneath plate, for example by the use of a jig or frame device, or by temporarily locating the underneath plate by means of a harnmer. The latter technique has the further disadvantage that teeth may be bent, reducing the quality of the joint.
Attempts have been made to reduce the time involved in truss manufacture by attaching the connector plates to components of the truss prior to their assembly with the other components. For example, International patent application No. PCT/FI91/00104 describes an approach in which the plates for one side of the truss are pre-attached to the webs, while the plates for the other side of the truss are pre-attached to the chords. Such a method is of limited usefulness.
SUMMARY OF THE INVENTION
The present invention seeks to provide an alternative approach, which enables the plates for both sides of the joint to be pre-attached to each end of a web, while still enabling the webs to be brought into position in the truss without difficulty, prior to pressing of the joint.
This is achieved by providing the nail plates with at least one, but preferably several, teeth of greater length than the remainder of the plate teeth, these longer teeth being located only in the region of the plate which is to be attached to one of the joint members, preferably the web.
In this way, plates can be attached to the-web ends by pressing the plates into position, the press driving only the longer teeth into the web. The opposed ends of the teeth of the portion of each plate which extends beyond the end of the web will thus still be separated by at least the thickness of the chord to which the web is to be attached, so the web can be brought into position for fixing to the chord without these teeth fouling the chord and thereby obstructing movement of the web.
Of course, while it is preferred to pre-attach the plates to the webs, they may instead be pre-attached in the same way to the chords at the correct joint positions and the webs then brought into position with their ends between the projecting opposed pre-fixed fixed plates.
It may be noted here that in U.S. Pat. No. 3,304,106 of Gerald M. McCormack there is described a nail plate which is divided into a region having short teeth and a region having longer teeth. In the McCormack patent, however, the short teeth have low withdrawal strength, so that the plate may be permanently fastened to the member by means of the longer teeth and removably fastened to the other member by the short teeth, in order that the truss may be disassembled for transport and later reassembled on site. Because the short teeth are incapable of forming a permanent joint, nail holes are also provided and the final joint is achieved by nailing through these holes.
A connector plate of the kind described by McCormack is distinguished from plates according to the present invention by the fact that the short teeth of McCormack are designed for low withdrawal resistance and are incapable of forming a permanent joint, whereas in the case of the present invention the short teeth are of conventional connector plate design, and consequently have conventional withdrawal resistance and are capable of forming a permanent joint. In other words, McCormack achieves the ability to disassemble the joint by having shorter than normal teeth over one half of the plate, whereas in the present invention the ability to pre-attach plates to one side of the joint is achieved by using in one half of the plate some teeth which are longer than normal. The conventional teeth employed in the plate are, ipso facto, capable of forming a satisfactory joint without additional means such as nailing. Such a joint will be referred to herein as a permanent joint.
The invention will be exemplified below in its application to roof trusses, but it is to be understood that it is applicable to other structural assemblies of wooden components, such as floor trusses.
The accompanying drawings illustrate, by way of example only, the application of the invention to the manufacture of roof trusses.
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Bochna David E.
Browne Lynne H.
Co-Ordinated Constructions Pty. Ltd.
Schindler Edwin D.
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