Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Threaded fastener locked to a discreet structure – Nut – and means to engage substructure on its opposite faces...
Reexamination Certificate
2000-06-02
2001-10-16
Wilson, Neill (Department: 3627)
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
Threaded fastener locked to a discreet structure
Nut, and means to engage substructure on its opposite faces...
C411S161000, C411S399000
Reexamination Certificate
active
06302629
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to an anti-loosening fastener for joining metal panels. Specifically, the invention is directed to a sheet metal screw for attaching two thin panels together, which screw exhibits an increased stripping torque over those of the prior art.
2. Description of the Prior Art
With presently available sheet metal screw, the range between drive torque and strip torque is unacceptably small. For this reason, it is virtually impossible, given dimensional tolerances and variances in material, to find a single torque setting on power screwdrivers that will drive the hardest-to-drive screw without stripping the easiest-to-drive screw. Such a situation results in a relatively high number of screws being stripped during installation, leading to reduced clamping force between two metal panels being joined or secured together, or requires substantial operator time for removal and replacement of stripped screws. A type of screw that probably would provide a solution to this problem by increasing the range between drive torque and strip torque, making it more difficult to strip the screw with the torque required to drive it into the panels being joined together.
One such attempt is disclosed in U.S. Pat. No. 5,183,359, issued to Barth on Feb. 2, 1993. Barth discloses a head
20
a
and a threaded shank
10
a,
and the head
20
a
has a clamping face
210
a
which include s a number of polyhedral nibs
23
a
extending axially therefrom and separated from one another by substantially planar uninterrupted portions of the clamping face
210
a.
The nibs
23
a
include a leading wall
233
a
and a trailing wall
235
a,
facing in the direction of tightening and opposite thereto, respectively. The leading wall
233
a
may be inclined at a steeper angle with respect to the plane of the clamping face
210
a
than is the trailing wall
235
a,
or vice versa. The leading wall
233
a
and trailing wall
235
a
meet to form an apex
231
a
which is also inclined with respect to the plane of the clamping face
210
a,
so that the nibs
23
a
increase in axial height as one views outward toward the periphery of the clamping face
210
a.
And the trailing wall
235
a
angle may be greater than the leading wall angle
231
a
may still inhibit further tightening of the fastener member, while the trailing wall
235
a
may resist backout due to vibration, as shown in
FIGS. 1A and 1B
.
Unfortunately, the direction of vibration cannot be predetermined. The trailing walls
235
a
of the nibs
23
a
are designated for absorbing one-way vibrational torque only. Therefore, this type of fastener cannot be used in a nondirective high frequency vibration environment.
SUMMARY OF THE INVENTION
It is a major object of the invention to provide a plurality of relatively small integral tapered angle blocks on the underside of the head, spaced from one another by substantially planar uninterrupted portions of head and projecting axially therefrom for engaging a workpiece.
Another object of the invention is to overcome the directional instability in a high frequency vibration environment by using the tapered angle block to absorb in any direction.
The present invention is directed to a sheet metal screw for attaching two thin panels together, an anti-loosening fastener for joining metal panels. It comprises a head having an upper side and underside; a shank having threads throughout the entire length thereof, the shank being attached to the underside of the head; and a plurality of relatively small integral tapered angle blocks on the underside of head, spaced from one another by substantially planar uninterrupted portions of said head and projecting axially therefrom for engaging a workpiece. Furthermore, each tapered angle block has an incision therefrom, which defines an angle from the periphery of said tapered angle block cutting to the vertex, and set on whose clockwise direction by substantially planar uninterrupted portions of said head and projecting axially therefrom.
These and other objects and advantages of the invention, as well as the details of an illustrative embodiment, will be more fully understood from the following description and drawings, in which:
REFERENCES:
patent: 2112494 (1938-03-01), Olson
patent: 2128757 (1938-08-01), Olson
patent: 4220188 (1980-09-01), McMurray
patent: 5356253 (1994-10-01), Whitesell
National Aerospace Fasteners Corp.
Rosenberg , Klein & Lee
Wilson Neill
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