Patent Application
20050252152
This invention relates generally to fasteners used in the construction arts, and in particular, to steel construction utilizing fastener connected truss members.
Trusses and girders have long been used in construction for spanning distances in industrial and residential buildings. Steel trusses are now frequently used for the support of roof structures due to their advantageous physical properties. In general, trusses are constructed of truss members such as chords and tubular members. The truss members are often joined together with fasteners, such as bolts. Fastener joining is most common in medium and large span truss assemblies.
The joining of the truss elements often involves complex assembly that requires a high labor input to complete the truss assembly. Typically, the assembly is accomplished through the use of plates combined with bolts that pass through the truss members and plates. The plates may be separate or may be integral to the truss members. In some cases welding may augment or replace the use of fasteners in joining together truss members. However, when welding is utilized, the truss assembly typically must be flipped over in order to complete the reverse side welds.
Conventionally, truss fasteners are designed to pass through a first plate and penetrate through the truss member and into a second plate. Fasteners such as those disclosed in U.S. Pat. No. 5,746,039 have a threaded section near the tip of the fastener and a threaded section near the head of the fastener. In some cases, the tip of the bolt or screw is configured to be a self-tapping such that rotation of the fastener allows the tip to penetrate both plates and truss members. One advantage to this fastener configuration is that a truss can be assembled without a need to turn the truss over such as when a screw or bolt is used on either side of the truss assembly or when welding is utilized.
A significant problem arises when the truss fasteners do not penetrate in strictly a perpendicular orientation to the surfaces of the truss components. Conventionally, truss fasteners have a head with a planar bottom surface which may also have a grooved seating surface. When the conventional fastener is installed in such an oblique angular orientation as described above, the planar or grooved seating surface contacts the plate or structural member at a very limited point of contact. Not only is this a relatively weak point of contact, but there is also a concentration of force at this limited point of contact.
The present invention in a preferred form is directed to a device that addresses, among other things, the adverse consequences which result from the oblique driving of a structural fastener. The present invention is a fastener which comprises a fastener shank having a tip and a head. The fastener shank further has threaded portions for engaging truss members and plate elements if present. The tip of the shank can have a self-tapping point. The head of the fastener has a tool engagement surface and a seating surface. The seating surface has a configuration that allows for a wider distribution of force at a truss assembly contact point. In particular, the configuration may include an arcuate contour that is generally convex and is defined by a surface of revolution about the central shank axis.
An object of the present invention is to provide a strong contact interface between the seating portion of the fastener head and the truss assembly regardless of the fastener installation angle.
Other objects and advantages of the invention will be evident to one of ordinary skill in the art from the following detailed description with reference to the accompanying drawings in which:
Briefly stated, the invention in a preferred form is a steel truss fastener which advantageously provides a connection of high integrity even for an installation wherein the fastener is driven at an oblique angle to the joined structural elements of a truss assembly. With reference to the drawings wherein like numerals represent like parts throughout the several figures, a steel truss fastener in accordance with the present invention is generally designated by the numeral 10.
The steel truss fastener 10 includes a head 12 integrally attached to an elongated threaded shaft 14. The threading 16 of the shaft 14 may be present along the entirety of the shaft or may be interrupted so as to be present at only a portion or separate portions of the shaft. For example, two portions of the shaft may be threaded, as illustratively shown in
In one embodiment of the invention the threading 16 is of the buttress thread 58 configuration. The buttress thread 58 includes a support surface 86 and a driving surface 88. In a preferred form, the support surface 86 is oriented at an angle of approximately 10 degrees to a normal line N to the central axis 18 of the shaft 14. Preferably, the angle a between normal line N and the support surface 86 is between about 0 degrees and about 15 degrees. The driving surface 88 is preferably oriented at an angle of approximately 35 degrees to a normal line N to the shank axis 18. In preferred form, the angle of b between the normal line N and the driving surface 68 is between about 25 degrees and about 65 degrees.
The head 12 in one embodiment of the invention has an upper surface 22 and a lower surface 24. The lower surface defines a contact surface 26 that is substantially arcuate in shape and axially symmetric about axis 18. The arcuate contact surface 26 of the head may be in the form of a continuous arc or may have angular arcing portions of differing angles relative to the center axis 18 of the shaft 14. For instance, the angle(s) of arcuate contact surface 26 relative to the shaft center axis 18 may range from an angle that is about 0° to an angle of about 25°. The arcuate contact surface 26 when in contact with a truss member 34 or plate 38 defines an arcuate contact pathway 28. The arcuate contact pathway 28 is positioned between an attachment point 30 of the head and an edge of the head 32 when the fastener 10 is installed at an oblique angle. The arcuate contact pathway 28 includes a portion of the arcuate contact surface 26 that is in contact with the truss member 34 or plate 38. This portion of the arcuate contact pathway 28 may encompass a significant length of the total arcuate pathway length. For example, the portion of the arcuate contact pathway in contact with the truss member 34 or plate 38 can be in the range of about 5% to over 90% of the total arcuate contact pathway 28 length.
An example of a truss assembly 40 utilizing a fastener 10 is illustrated in
In one embodiment of the invention, the fastener 10 engages with the truss member 34 until the lower surface 24 of the head 12 reaches a first surface 36 of the truss member. The truss member 34 may form a multiple sided structure such as a square, rectangle, or other geometrical shape. The truss member may therefore have a second surface through which a portion of the fastener 10 may penetrate. The fastener 10, as illustratively shown in
In one embodiment plates 38 may be used on both sides of the truss member 34 when joining truss members together. The plates 38 can be present to secure several truss members 34 together, such as at a web of the truss assembly. A plate or plates may be present intermediate that head arcuate contacting surface 26. For example, a plate may be present in substantially parallel alignment with a surface of the truss member. When the fastener is installed through a plate 38 on the first surface of a truss member, a portion of the arcuate contacting surface 26 contacts the plate substantially parallel to the first surface of the truss member 34. It should be understood that a second surface of the truss member 34 may or may not be in substantially parallel alignment with the portion of the arcuate contacting surface 26 depending on the configuration of the truss member 34.
While the embodiments of the foregoing invention have been set forth for the purpose of illustration, the foregoing description should not be deemed a limitation of the invention herein. Accordingly, various modifications adaptations and alternatives may occur to one skilled in the art without departing from the spirit and scope of the present invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.
