Trusses are common components for many construction framing projects. However, despite the ubiquitous nature of trusses, it is relatively rare that any single truss design is replicated to a large extent. As such, many trusses are custom built for a particular construction project. Due to the highly customized residential and commercial construction markets, a strain is placed on truss manufacturers, which may be particularly acute in the area of set up. For that reason, much of the automation associated with truss fabrication has been focused on automating set up functions for cutting and assembly.
Currently, pieces of lumber are cut to the precise length and properly angled end, sorted and stacked after sawing, and transported to a staging area where truss assembly is performed. When the production schedule requires, the cut and sorted pieces may be moved to the assembly area along with needed connectors, which may include plates with teeth that imbed at least partially into wood members of the truss at their ends or along their length to hold the members together during the assembly process. The pieces may then be laid into an assembly jig, which provides a form or guide for member placement and truss assembly. The connectors may be placed on both top and bottom faces of the lumber at the joints between adjacent pieces.
Due to the custom nature of truss fabrication, it is often necessary to readjust the jig for each different truss. Accordingly, mechanisms have been developed to increase efficiencies related to setting up a jig. For example, jigging tables using lasers to outline jig or lumber patterns or having slidable guide members for more rapid adjustment of the jig have improved the ability of fabricators to customize jigs. However, the placement of lumber in the jig is typically done manually. The installation of connectors is also typically done by hand.
While the top face of the lumber is readily accessible, the bottom face is not since it is typically in contact with a jigging table or other substrate upon which the jig is provided. Accordingly, placement of a top plate, which is a connector engaging a top face of various members forming a joint in the truss, may not be difficult. In fact, various mechanisms including outlining a form of a plate on the various members have been developed to increase efficiency in placement of plates or connectors for the top faces of the lumber in the truss. However, it is typically necessary for the lumber pieces or members forming a particular joint to be simultaneously lifted so that the bottom plate can be slid underneath and properly located. Moreover, the location of the bottom plate is often determined by feel or merely from the positioning of edges that may be visible from above.
U.S. Pat. No. 5,440,977 to Poutanen describes one mechanism aimed at improving truss assembly by affixing connector or nail plates to some truss members prior to transporting the members to an assembly station. However, the assembly of truss members in Poutanen is manual. Although the prior plating of the connector plates may speed the truss assembly process, errors associated with manual handling and placement of truss members may still be introduced.
Given that truss manufacturing is likely to remain a highly customized process and also given that mechanisms for automating truss manufacturing may have the capability of providing time and cost savings that may present market advantages to those employing automation techniques, it may be desirable to introduce a mechanism that may overcome at least some of the disadvantages described above, or further automate the truss assembly process.