Note: Descriptions are shown in the official language in which they were submitted.
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SELF-DRII,LING, SEl,F-TAPPING FASTENER
BRIEF DESCRIPTION OF THE INVENTION
The present invention cornprises an improved self-drilling,
self-tapping screw. The drill point includes two half-conical
segments with flat sides and rounded tips. The segrnents are
longitudinally offset along the axis of the screw with respect --
to one another and portions of the flat sides are coplanar. The
two angles included by the conical segments may be different
with the angle of the segment nearer the head end preferably
being the larger of the two. The self-tapping thread may take
any of several forms: it may be a machine thread, a type B
thread, or a quad-lead thread having two threads with a first
crest diameter and two threads with a second larger crest
diameter .
The screw of the present invention is particularly adapted
for fastening wallboard or other panel material to steel studs.
The self-drilling, self-tapping screw of the present invention
has shown itself to be a faster driller than other drill screws,
requires less complicated manufacturing steps and tooling to
make and, therefore, can be rnanufactured more economically.
Further, the conical segment positioned nearer the head extrudes
the relatively thin metal in the stud during drilling providing
greater thread engagement with the screw. This greater
thread engagement results in higher pullout values (i. e.,
greater holding power) for the fastener. The embodiment
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utilizing the quad-lead thread can be utilized to further
increase thread en~agement due to its increased thread density.
Although particularly adapted for steel studs, the fastener
of the present invention can be utilized in wood applications
without the need for modifying its configuration. The flatness
of the drill tip prevents the flutes from packing with wall-
board particles which can prove troublesome for other screw
configurations.
The invention, in its broadest aspect, contemplates a
self-drilling, self-tapping screw which comprises a head with
drive-engageable surfaces at one end, a drill point at the opposite
end, and a threaded region intermediate the two ends. The drill
point includes a first conical segment with a flat side and a
rounded tip, wherein the edges of the flat side of the first
conical segment create a pair of cutting edges diverging from
a continuously curved rounded tip at a relatively sharp acute
angle~ The cutting edges e~tend for a predetermined axial dis-
tance along the screw length, with the first conical segment being
at a first longitudinal position along the screw length. A second
conical segment with a flat side and a rounded tip is located at
a second longitudinal position along the screw length, with the
second longitudinal position being nearer the head than said first
position and at least a portion of the two flat sides being
coplanar The surfaces of each conical segment are smoo~h at least
in the longitudinal positions of the cutting edges, and the ~lat
side of the second conical segment is coplanar with the flat
side of the first conical segment and defines a pair of side
edges diverging from the rounded tip of the second conical segment
at a relatively sharp acute angle. The side edges of the second
conical segment are spaced radially inwardly from associated
cutting edges on the first conical segment creating a pair of
flat side segments radially inwardly of the cutting edges for a
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substantial portion of the predetermined axial distance. The
transverse dimension of the drill point in the plane of the
cutting edges at any given location is greater than the trans-
verse dimension in any longitudinal plane intersecting the cutting
edge plane.
These and other features, objects and advantages of the
present invention will become more apparent through reading the
following specification in conjunction with the appended drawings.
BRIEF DESCRIPTION OF THE DRA~INGS
Fig. 1 is a top elevational view of the fastener of the
present invention;
Fig. 2 is an enlarged side elevational view in partial
section of the tip region of the fastener of Fig. l;
Fig. 3 is a partial end cross section taken along line 3-3
in Fig. 2;
Fig. 4 is an enlarged top view of the drill tip of the
fastener of the present invention;
Fig. 5 is an enlarged side elevational view in partial
section of another embodiment of the fastener of the present
invention;
Fig. 6 is a cross-sectional end view taken along line 6-6
in Fig. 5;
Fig. 7 is a top elevational view of the drill tip of the
Fig. 5 embodiment.
DETAILED DESCRIPTION OF THE INVENTION
The self-drilling, self-tapping screw of the present
invention is shown generally at 10. The head 12 of the screw has
the same general configuration shown in U.S. patent 3,056,234. This
head style has proven to be particularly well adapted for retention
in wallboard or the like. Recess 14 provides a plurality of
drive-engageable surfaces for rotationally driving the screw.
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Threaded region 16 may, preferably, cornprise a quad-lead
thread configuration utilizing two threads 18 having a first
crest diameter and two threads 20 having a second larger crest
diameter. The drill tip shown generally at 22 comprises a first
conical segment 24 and a second conical segment 26. Each seyment
has a flat side and a rounded tip 28, 30 respectively. Second
segment 26 is longitudinally offset with respect to the first
conical segment 24 toward head 12. In an alternate embodiment
conical segment 26 also may have a larger included angle to make
up for its shorter length. The flat sides of the two segments
are partially coplanar. The flat sides include portions 32 on
the first conical segment 24 which create a pair of cutting edges
diverging from the rounded tip 28 at a relatively sharp acute
angle. These cutting edges, as shown in the drawings, extend
substantially the full axial extent of the drill tip 22.
It will also be noted from -the drawings that the conical
segments on the tip are free of thread configurations which could
retard the entry rate of the point through the workpiece.
As also will be clearly understood by reference to Figs.
2, 3, S and 6, the axial offsetting of the conical segments,
which have their flat surfaces lying along a hypothetical axial
center line of a complete cone, will provide a tip that has a
transverse dimension in the plane of the cutting edges which
will be greater, at any axial position, than at any other longi-
tudinal plane extending through the center line of the screw.This will clearly provide relief behind the cutting edges.
The offset between segments 24 and 26 creates two flute
areas 32. Due to the drill tips symmetry, it is capable of drilling
by rotation of the screw in either direction. This drill tip can,
therefore, be incorporated on a screw employing a left hand
thread without any modiEication of its configuration. As the
drill tip 22 enters the steel stud, the second conical segment 26
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engages the material and works it, extruding it out the back
of the hole being formed. This extrusion increases the surface
area of the aperture which is available for thread engagement by
threaded region 16. The grea-ter the thread engagement, the
larger the pullout values, or holding strength, of the fastener.
The quad-lead helps to further increase the holding strength due
to the increased thread density.
A second embodiment is depicted in Figs. 5-7. In this
embodiment, the included angle of conical segment 26 is com-
paratively larger with respect to segment 24 than in the previousembodiment. Further, whereas the flat side of each segment lay
generally along -the hypothetical axial center line in the Fig.
1-4 embodiments, the flat sides of this embodiment are off the
center line giving the point a much flatter configuration. The
lS threaded region 16 of this embodiment is shown with a type B
thread but can have a machine thread or any other thread form
which may be convenient.
The self-drilling, self-tapping screw of the present
invention can penetrate ~wallboard or the like and drill into
and ~asten into a steel stud. Due to the configuration of the
drill tip, the flutes will not become packed with particles of
wallboard which can have a detrimental effect on o-ther drill
screws. Further, this drill tip extrudes the material of the
stud as it drills thereby increasing the available material
thickness for thread engagement. Lastly, this fastener is
equally well adapted for use with wooden studs and need not be
limited to steel stud applications.
Various changes, modifications and alternatives wil:l
become apparen-t to a person of ordinary skillin the art as a
result of reading the foregoing specification. Accardingly, it
is intended that all such changes, modifications ancl alternatives
as come within the scope of the appencled claims fall within the
boundaries of the present invention.
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