The present invention relates to tree fasteners useful for fastening items to sheet metal, panels, and similar structures.
BACKGROUND OF THE INVENTION
Tree fasteners with radially extending wings or branches for insertion into apertures in sheet metal, panels, and other similar structures are known in the prior art. Typically, tree fasteners are arranged to be driven axially into preformed openings in a sheet metal or other panel and to engage the surface near the opening on the opposing side of the structure by virtue of radially extending flexible tabs or wing-like members. Fasteners of this variety are often referred to as fir tree fasteners because of the shape of the fastener. Fasteners of this type have flexible tabs or wing-like members that extend outwardly from a shank as branches do from the trunk of a tree. They are also sometimes referred to as plastic drive fasteners.
A tree fastener with split wings is described in Meyer, U.S. Pat. No. 5,907,891. A plastic drive fastener with wings designed to increase the force required for removal from apertures is described in Chisholm et al., U.S. Pat. No. 4,728,238. A plastic drive fastener having axially offset wing elements is described in Lewis, U.S. Pat. No. 5,306,098.
A fir tree fastener may be used to secure one panel to another panel. Additionally, a fir tree fastener may be an integral part of a cable tie that is used to secure a wiring harness to an automotive panel. There are many other possible applications.
For many applications it is desirable to have a low insertion force when installing the fastener into an aperture of a structure and to have a high disengage force for removal. It is advantageous to many manufacturers, suppliers, and users for the fastener to perform over a broad range of aperture sizes, shapes, and panel thicknesses. It is also desirable in applications subject to vibration, such as machinery, or vehicles of all kinds, to have the fastener fit snugly into an aperture to resist the vibration and minimize rattling noise.
Tree fasteners known in the prior art generally provide acceptable performance characteristics when applied to a narrow range of aperture sizes, shapes, and panel thicknesses. Outside of this range of application, performance, such as the force required to engage and/or disengage the fastener, can significantly change.
There are no universally accepted standards for aperture size or shape or panel thickness. Fastener producers and merchants must carry a large variety of fasteners and large number of fastener part numbers to accommodate the wide range of applications. Significant costs are incurred by manufacturers, merchants, and users as a result of having to manage each additional part number. These costs include, but are not limited to, costs for designing, producing, inventorying, tracking, and accounting for each additional part number.
SUMMARY OF THE INVENTION
The present invention relates to a universal tree fastener that can fit and function over a range of aperture diameter, shape, and thickness applications.
These and other advantages are achieved by providing a tree fastener wherein a cylindrical shank vertically extends from a base and wings radially extend from the shank in longitudinally extending segments or columns. The wings extending from two of the opposing segments are smaller than wings extending from two other opposing segments. Multiple opposing sets of wings with different radial dimensions enable the present invention to function over a broad range of aperture sizes and shapes.
Advantages are also achieved by providing a fastener wherein wings extend from the shank in longitudinally extending segments or columns. The invention allows free flexing of the wings and prevents wing interference as the fastener is inserted into an aperture of a structure.
Furthermore, the invention enables a fastener to be installed with relatively low force while maintaining a high disengage force, and a high ratio between disengage force to engage force over a range of aperture sizes and shapes and panel thicknesses. The fastener also provides resistance to vibration and rattling over a range of aperture sizes and shapes and panel thicknesses.
As shown in FIGS. 2 and 3, the shank 14 is generally cylindrical in shape, having a longitudinal axis 18 extending vertically away from the base 12 and a longitudinal surface 20 extending radially from the longitudinal axis 18. It will be appreciated that the shank can have other shapes. For example, the cross-section may also be oval, elliptical, or polygonal. The longitudinal surface 20 is comprised of four diametrically opposing longitudinally extending segments 20 a,b,c,d, from which four corresponding columns of wings extend, each segment 20 a,b,c,d extending the length of the longitudinal surface 20. It will be appreciated that the advantages of the present invention may also be achieved with more or less than four columns of wings.