Static structures (e.g. – buildings) – Openwork; e.g. – truss – trellis – grille – screen – frame – or... – Three-dimensional space-defining
Reexamination Certificate
2002-11-12
2004-08-10
Friedman, Carl D. (Department: 3635)
Static structures (e.g., buildings)
Openwork; e.g., truss, trellis, grille, screen, frame, or...
Three-dimensional space-defining
C052S715000, C052S092200, C052S640000
Reexamination Certificate
active
06772570
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to brackets. More particularly, this invention relates to brackets for connecting rafters to ridge boards.
Building a roof requires extensive labor to prepare the components for assembly and for erection. The time required is increased if the components have to be positioned and then assembled high in the air with little or nothing to support them. In addition, components such as rafters have to be located with great accuracy in order to have the roof surfaces plane and intersect properly.
One of the simplest roofs is the gable, an illustration of which is shown in
FIG. 5
herein. At its center and highest elevation, the gable roof has a rectangular steel or wood ridge board that connects the two triangular gable ends of the roof along the long axis of the building. Connected to the ridge board on both sides at regular intervals (normally 16 or 24 inches on center) are rafters, typically rectangular wood or steel roof supporting members, the same size or smaller than the ridge board. Rafters are attached perpendicularly to the ridge and slope down the roof at some angle, called the “roof slope”, in opposite directions, to intersect with the top of the building's exterior walls at opposite sides of the ridge. The distance between the outside edges of the two opposing top plates is referred to as the roof's “total span”.
A triangle is created at the two ends of the gable roof, between the two top plates and the ridge board. Because the ridge board is normally centered on the roof, a vertical line dropped from the center of the ridge board perpendicular to the horizontal plane created by the two opposing top plates will form two identical right triangles. Each triangle has a base leg equal to one-half the roof's “total span”. The angle created between the horizontal plane of the two top plates and the hypotenuse of each triangle is the roof slope. The vertical distance between this horizontal plane and the theoretical point of intersection of the two opposing rafters is known as the “total rise” of the roof. The horizontal distance from the outside edge of either top plate to the point perpendicular and directly below the point of intersection of the two opposing rafters is known as the “total run” of the roof. The roof's “total run” is equal to one-half the roof's “total span”. The “roof pitch” is the slope of the roof expressed as the ratio of the “total rise” to the “total run”, and is usually shown as a whole number of inches of “total rise” to 12 inches of “total run”.
For any set of plans, the designed roof pitch is specified and the “total run” is determined from the plan dimensions. From this information, the theoretical length of the rafters (the hypotenuse) can be calculated.
FIG. 5
shows the typical rafter installation using current assembly techniques. The calculated theoretical rafter length is different from the actual rafter length because the top surface of the rafter does not intersect the outside of the top plate. Instead, the rafter typically has a cut (i.e., “bird's mouth”) which extends horizontally from the bottom surface of the rafter to provide a surface for the rafter to rest on and be secured to the top plate. Thus, the actual line the hypotenuse follows is from the intersection of the two opposing rafters through the body of the rafter to the intersection of the “bird's mouth” and the outside of the top plate. Depending on the length and size of the rafter, the height of the rafter's top surface above the top plate and the steepness of the roof, the actual pitch of the roof would be considerably different from the designed roof pitch.
Using the current assembly techniques, the top of the rafter is marked with the first ridge plum line (based on the designed roof pitch). An adjustment to the theoretical length of the rafter is then manually applied at the first ridge plum line to compensate for the thickness of the ridge board. A second ridge plum line is then marked at this adjustment point on the rafter. From the first ridge plum line, the calculated theoretical rafter length is then applied to the rafter. A heel plum line is marked at the end of the applied rafter length measurement. A horizontal seat cut line is then determined and marked on the rafter to intersect with the heel plum line.
Once the markings are applied to the rafter, the rafter is cut at the second ridge plum line and the heel plum line. The heel plum line is cut from the bottom surface of the rafter along the heel plum line to the intersection with the horizontal seat cut line. The horizontal seat cut line is then cut horizontally from the bottom surface of the rafter to the intersection with the heel plum line.
All of the cuts along the aforementioned marked lines are cut manually at the job site. As indicated in the discussion above, however, the layout and cutting of rafters requires considerable expertise and time. Thus, the accurate placement of the rafters, using the current assembly techniques, is completely dependent on the skill, care and knowledge of the carpenter building the roof. Small compounded errors in measuring, the width of the markings, the kerf size of the saw blade, the accuracy of the saw cut line, and the like, can all accumulate to cause significant variations between each finished rafter. Thus, it is desirable to provide a means for attaching rafters to ridge boards, the accuracy for which does not rely solely on the skill of the carpenter. In particular, it would be desirable to provide a means for attaching rafters to ridge boards which does not require on-site cutting of the rafters.
Once the rafters have been cut, they are individually attached to the ridge board. The top of the rafter at the ridge plum line cut, is located at and fastened to the top edge of the ridge board. Because of variations in rafter lengths and the angle of the rafter's ridge plum line cuts caused by the lack of accuracy in the manual measurement and cutting steps, the rafters are positioned on the ridge by “eye” and then, based on visual observation, adjusted to create as level a plane as possible along the top surfaces of the rafters. The plane formed along the rafter top surfaces constitutes the roof surface.
As indicated above, the location and level of the roof surface plane totally depends on the accurate cutting and positioning of each rafter on the ridge board by the carpenter. When using the current assembly techniques, there is no mechanical means or calculated measurement that aids the carpenter during assembly. It is all done by “eye” based on experience. It would be desirable to provide a means for installing rafters which does not rely solely on visual observation for accurate installation.
Variable pitch connector brackets for attaching rafters to bearing members such as ridge boards have been used in the art. Reference is made, e.g., to U.S. Pat. Nos. 4,498,801 (Gilb et al.), 5,546,726 (Stalzer), 5,797,694 (Breivik), 5,004,369 (Young) and U.S. Pat. No. 5,230,198 (Callies).
Although many brackets of varying designs have been developed, they all use similar assembly techniques and have all attempted to provide an integrated support to the existing rafter/ridge connection, e.g., by attaching sheet metal, with nails or screws, to the upper portion of the rafter at the rafter's ridge plum line cut/ridge junction and then mechanically fastening the sheet metal, with nails or screws, to the ridge board. Thus, the rafter is integrated as an interdependent, mechanical link in the support mechanism designed to support the pre-existing, direct mechanical connection of the rafter to the ridge at the rafter's ridge plum line cut/ridge junction. Therefore, in the prior art, the bracket's pitch depends on the integration and attachment of the rafter to the bracket and to the physical joining of the surface of the rafter's ridge plum line cut against the side surface of the ridge board.
It would be desirable to provide a bracket for connecting one or more rafters
Friedman Carl D.
Katcheves Basil
Patton & Boggs LLP
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