Note: Descriptions are shown in the official language in which they were submitted.
SCREW-TYPE FASTENER FOR CEMENT BOARD
TECHNICAL FIELD
[0001] This application relates generally to threaded fasteners for
cement board
applications, and more particularly, to a multi-thread cement board screw.
BACKGROUND
[0002] A typical screw configuration includes an elongated shank that
extends between
a driving head of the screw and a pointed end of the screw. At least part of
the shank is
helically threaded. Cement board screws with a variety of configurations are
known.
However, improvements are continuously sought.
[0003] It would be desirable to provide a cement board screw
configuration that
facilitates quick and effective installation with relatively low torque
requirement and a
resulting high resistance to pull-out after installation.
SUMMARY
[0004] In one aspect, a cement board screw includes advantageous
performance
features.
[0005] In another aspect, a cement board screw includes a head end, a
shank and a
tapered end, the head end including a tool engaging part, the head end located
at one end of the
shank and the tapered end located at an opposite end of the shank. A high
thread is formed
along the shank, wherein the high thread begins on the tapered end, extends
onto the shank and
terminates at a first axial location along the shank. The high thread defines
a high peripheral
edge, wherein the high thread includes a leading flank and a trailing flank
that meet at the high
peripheral edge and together define a high thread angle that is between about
thirty degrees
and about fifty-five degrees. A low thread formed along the shank, wherein the
low thread
begins on the tapered end, extends onto the shank and terminates substantially
at the first axial
location along the shank such that an axial length of the low thread is
substantially the same as
and contiguous with an axial length of the high thread. The low thread defines
a low
peripheral edge, wherein the low thread includes a leading flank and a
trailing flank that meet
at the low peripheral edge and together define a low thread angle that is
between about fifty
degrees and about seventy degrees.
[0006] In another aspect, a cement board screw includes a head end, a
shank and a
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tapered end, the head end including a tool engaging part, the head end located
at one end of the
shank and the tapered end located at an opposite end of the shank. A high
thread is formed
along the shank, wherein the high thread begins on the tapered end, extends
onto the shank and
terminates at a first axial location along the shank. The high thread defines
a high peripheral
edge, wherein the high thread includes a leading flank and a trailing flank
that meet at the high
peripheral edge and together define a high thread angle. The first axial
location is spaced from
the head end. A low thread is formed along the shank, wherein the low thread
begins on the
tapered end, extends onto the shank and terminates substantially at the first
axial location
along the shank such that an axial length of the low thread is substantially
the same as and
contiguous with an axial length of the high thread. The low thread defines a
low peripheral
edge, wherein the low thread includes a leading flank and a trailing flank
that meet at the low
peripheral edge and together define a low thread angle. The low thread angle
is larger than the
high thread angle. A set of counter threads on the shank run from proximate
the first axial
location toward the head end, the counter threads having a helical direction
that is opposite a
helical direction of the high thread and the low thread.
[0007] In another aspect, a cement board screw includes a head end, a
shank and a
tapered end, the head end including a tool engaging part, the head end located
at one end of the
shank and the tapered end located at an opposite end of the shank. A high
thread is formed
along the shank, wherein the high thread begins on the tapered end, extends
onto the shank and
terminates at a second axial location along the shank. The high thread defines
a high
peripheral edge, wherein the high thread includes a leading flank and a
trailing flank that meet
at the high peripheral edge and together define a high thread angle that is
between about thirty
degrees and about fifty-five degrees. A low thread formed along the shank,
wherein the low
thread begins on the tapered end, extends onto the shank and terminates
substantially at the
first axial location along the shank such that an axial length of the low
thread is less than an
axial length of the high thread. The low thread defines a low peripheral edge,
wherein the low
thread includes a leading flank and a trailing flank that meet at the low
peripheral edge and
together define a low thread angle that is between about fifty degrees and
about seventy
degrees.
[0008] In another aspect, a cement board screw includes a head end, a
shank and a
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tapered end, the head end including a tool engaging part, the head end located
at one end of the
shank and the tapered end located at an opposite end of the shank. A high
thread is formed
along the shank, wherein the high thread begins on the tapered end, extends
onto the shank and
terminates at a second axial location along the shank. The high thread defines
a high
peripheral edge, wherein the high thread includes a leading flank and a
trailing flank that meet
at the high peripheral edge and together define a high thread angle. The first
axial location is
spaced from the head end and the second axial location is proximal to the head
end. A low
thread is formed along the shank, wherein the low thread begins on the tapered
end, extends
onto the shank and terminates substantially at the first axial location along
the shank such that
an axial length of the low thread is less than an axial length of the high
thread. The low thread
defines a low peripheral edge, wherein the low thread includes a leading flank
and a trailing
flank that meet at the low peripheral edge and together define a low thread
angle. The low
thread angle is larger than the high thread angle. A set of counter threads on
the shank run
from proximate the first axial location to proximate the second axial
location, the counter
threads having a helical direction that is opposite a helical direction of the
high thread and the
low thread.
[0009] The details of one or more embodiments are set forth in the
accompanying
drawings and the description below. Other features, objects, and advantages
will be apparent
from the description and drawings, and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Fig. 1 shows a side elevation view of one embodiment of a cement
board screw;
[0011] Figs. 2 and 3 show perspective views of the screw;
[0012] Fig. 4 shows a partial cross-section view of the screw taken
along a plane in
which the screw axis lies;
[0013] Figs. 5 and 6 show partial perspectives of the head end of the
screw;
[0014] Fig. 7 shows a cross-section of the head end;
[0015] Figs. 8 and 9 show enlarged views of the head end;
[0016] Figs. 10 and 11 show partial perspectives of the tapered end;
[0017] Fig. 12 shows an enlarged view of the high thread;
[0018] Fig. 13 shows a view looking along the screw axis at the tapered
end of the
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screw;
[0019] Fig. 14 shows a partial cross-section of the screw along a plane
that runs
perpendicular to the center axis of the screw and that is in the region of the
counter threads;
[0020] Fig. 15 shows a side elevation view of another embodiment of a
cement board
screw; and
[0021] Fig. 16 shows a partial cross-section view of the screw of Fig.
15 taken along a
plane in which the screw axis lies.
DETAILED DESCRIPTION
[0022] Referring to Figs. 1-13, one embodiment of a cement board screw
10 is shown.
The cement board screw includes a head end 12, a shank or core 14 and a
tapered end 16. The
head end 12 includes an end face 18 with a drive recess 20 (e.g., a star
recess or any other
suitable drive recess). The end face may include a textured surface feature as
shown, such as a
pattern of recesses or other texturing. As used herein the term shank refers
to the elongated
core or shaft of the screw, which can include threaded and unthreaded
portions. The tapered
end 16 is located at an opposite end of the shank 14 and terminates in a point
or tip 22. By
way of example, the taper angle al defining the point 22 may be between about
fifteen and
about twenty-five degrees (such as about eighteen to twenty-three degrees).
The tapered end
may also include a wedge cut 15 as shown. The wedge cut begins at the tip and
extends the
full axial extent of the tapered end.
[0023] A high thread 30 begins on the tapered end 16 (e.g., preferably
slightly short of
the tip as depicted by spacing X in Fig. 11, or at the tip), extends onto the
shank 14 and
terminates at a first axial location 32 along the shank. The spacing X may be,
for example, in
the range of 0.10 to 0.90 inches (e.g., 0.030 inches to 0.070 inches, or 0.40
to 0.060 inches).
The high thread 30 is a right-hand thread as shown, and has a peripheral edge
34 formed where
a leading flank 36 meets a trailing flank 38, which together define a high
thread angle a2 of
between about thirty-five degrees and about fifty-five degrees (e.g., between
forty degrees and
fifty degrees). In one implementation, the high thread is asymmetric, with a
leading flank
angle 01 and a trailing flank angle 02 that are different. In particular, the
trailing flank angle is
less than the leading flank angle. For example, the trailing flank angle may
be no more than
twenty degrees (e.g., between fifteen degrees and twenty degrees) and the
leading flank angle
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may be no less than twenty-five degrees (e.g., between twenty-five degrees and
thirty-five
degrees). The high peripheral edge 34 may be defined with a radius of between
about 0.002"
and about 0.008", where the radius joins the leading and trailing faces of the
thread.
[0024] The screw 10 has a penetrating axial length LP defined between
the tip 22 of
the tapered end 16 and the end face 18. An axial distance DH is defined
between the tip 22 of
the tapered end 16 and the first axial location 32. Here, the axial distance
DH is at least
seventy percent of the penetrating axial length LP of the screw. However,
variations are
possible (e.g., distance DH at least seventy-five percent of length LP or at
least eighty
percent).
[0025] A low thread 60 begins on the tapered end 16 (e.g., preferably
slightly short of
the tip or at the tip), extends onto the shank 14 and terminates at an axial
location 62 along the
shank. Here, the axial location 62 is substantially the same as the first
axial location 32, and
an axial length of the low thread is substantially the same as and contiguous
with the axial
length of the high thread. The low thread 30 is a right-hand thread as shown,
and has a
peripheral edge 64 formed where a leading flank 66 meets a trailing flank 68,
which together
define a low thread angle a4 of between about fifty degrees and about seventy
degrees (e.g.,
between fifty-five degrees and sixty-five degrees). In one implementation, the
low thread is
symmetric, with a leading flank angle and a trailing flank angle that are both
the same.
[0026] The pitch PH of the high thread 30 is substantially uniform along
the length of
the thread, as is the pitch PL of the low thread 60, and the low thread pitch
PL is substantially
the same as the high thread pitch PH. Each turn of the low thread 60 is
located substantially at
an axial mid-point between adjacent turns of the high thread 30. The
substantially uniform
thread pitch PH and PL may, for example, be between about 0.080 inches and
about 0.140
inches (e.g., between about 0.100 inches and about 0.120 inches).
[0027] The high thread 30 includes a minor diameter Dm and a major
diameter DMH,
and the low thread 60 includes the same minor diameter Dm and a major diameter
DML. The
height of each thread along the shank 14 is defined as the major diameter less
the minor
diameter. The shank 14 is substantially a right-circular cylinder along the
high and low
threads, and the cross-section of the tapered end 16 is circular, where the
cross-section lies in
any plane that is perpendicular to the screw axis 50.
Date Recue/Date Received 2021-02-02
[0028] The axial location 32, 62 is spaced from the head end 12 and the
shank 14
includes a set of counter threads 80 on the shank, where the counter threads
run from
proximate the axial location 32, 62 toward the head end 12. The counter
threads 80, which
operate as reaming threads, have a helical direction that is opposite a
helical direction of the
high thread and the low thread. The counter threads 80 have a major diameter
DMC that is
less than the major diameter DMH of the high thread and more than the major
diameter DML
of the low thread. The counter threads have a minor diameter Dmc that is
greater than the
minor diameter Dm of both the high thread and the low thread. Here, the set of
counter
threads is formed by six counter threads, wherein each counter thread extends
helically
through no more than one-hundred and twenty circumferential degrees. However,
variations
with more or less counter threads are possible. For example, the set of
counter threads may be
formed by no more than four counter threads, wherein each counter thread
extends helically
through no more than one-hundred and twenty circumferential degrees.
Regardless of the
number of counter threads, the counter threads 80 have a substantially uniform
circumferential
spacing about the shank as shown.
[0029] As best seen in the end view partial cross-section of Fig. 14, in
any given plane
that is perpendicular to the center axis 50 of the screw and along the axial
length of the counter
threads, the trailing flank 80A of each counter thread 80 extends
substantially radially, per line
81, and the leading flank 80B extends in a direction that is offset from
radial in a direction
toward the trailing flank 80A, per line 83. The angle (p4 that is enclosed by
the two flanks 80A
and 80B in the perpendicular plane of cross-section, is between about thirty
degrees and about
forty degrees (e.g., about thirty-five degrees).
[0030] The head end is formed as a countersunk head configuration with a
frustoconical lower part having a plurality of nibs, including a plurality of
large nibs 82 and a
plurality of small nibs 84, where multiple small nibs are disposed between
successive large
nibs as shown. The head end includes both an outer lower part 86 and an inner
lower part 88.
The outer lower part 86 defines a frustoconical taper angle yl and the inner
lower part defines
a frustoconical taper angle (p2, where taper angle yl is larger than taper
angle (p2. In one
implementation the taper angle (p2 is at least twice the taper angle (p2. By
way of example, (p2
may be in the range of sixty-five to seventy-five degrees.
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[0031] The small nibs 82 are defined substantially on the outer lower
part 86 (e.g.,
running from the head periphery to the inner lower part 88). The large nibs 82
are defined on
both the outer lower part 86 and the inner lower part 88. The large nibs are
defined by a first
nib portion 82A on the outer lower part 86 and a second nib portion 82B on the
inner lower
part 88. The first portion 82A and the second nib portion 82B meet and define
an interior nib
angle (p3 that is between about thirty-five and about fifty degrees. The large
nibs 82 have a
uniform circumferential spacing. The plurality of large nibs may formed by no
more than six
large nibs (e.g., four large nibs spaced apart from each other by ninety
degrees, or three large
nibs spaced apart from each other by one-hundred twenty degrees). Each of the
large nibs 82
includes a leading face 90 that joins the lower part at a radiused juncture 92
and a trailing face
96 that joins the lower part at a juncture 94 that is not radiused.
[0032] Various implementations of cement board screws in accordance with
the
configuration depicted in Figs. 1-11 are possible. By way of example, Table 1
and Table 2
below set forth one examples of such a screw implementation, where the high
thread and low
thread include a minor diameter Dm, the high thread includes a major diameter
DMH, the low
thread includes a major diameter DML, the high thread includes a thread pitch
PH, the low
thread includes a thread pitch PL, the high thread includes a high thread
height HTH on the
shank, the low thread includes a low thread height LTH along the shank.
Typical axial
penetrating lengths LP for such screws may be in the range of between about
one inch and
about two and one-half inches, though other variations are possible.
Table 1 ¨ Exemplary Screw Dimensions
(All Ranges in Inches)
PH & PL = Dm = DMH = DML = HTH = LTH =
0.080¨ 0.090¨ 0.155¨ 0.115¨ 0.005¨ 0.005 ¨
0.140" 0.150" 0.215" 0.170" 0.125" 0.080"
Table 2¨ Exemplary Screw Dimensions
(All Ranges in Inches)
PH & PL = Dm = DMH = DML = HTH = LTH =
0.100¨ 0.110¨ 0.175¨ 0.135¨ 0.045¨ 0.005 ¨
0.120" 0.130" 0.195" 0.150" 0.085" 0.040"
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[0033] Referring to Figs. 15 and 16, in another embodiment, a cement
screw is
provided having the attributes described above, with one or more of the
following alterations.
As shown in Fig. 15, a high thread 30 begins on the tapered end 16 (e.g.,
preferably slightly
short of the tip as described above, or at the tip), extends onto the shank 14
and terminates at a
second axial location 33 along the shank. A low thread 60 begins on the
tapered end 16 (e.g.,
preferably slightly short of the tip or at the tip), extends onto the shank 14
and terminates at an
axial location 62 along the shank. In this embodiment, the axial location 62
is substantially the
same as the first axial location 32, and an axial length of the low thread is
less than the axial
length of the high thread. The axial location 32, 62 is spaced from the head
end 12 and the
shank 14 includes a set of counter threads 80 on the shank, where the counter
threads run from
proximate the axial location 32, 62 toward the head end 12, e.g., terminating
at the second
axial location 33, defining a counter thread region (CTR). Thus, the CTR
comprises both the
counter threads 80 and an end part of the high thread 30. This feature helps
to prevent the
screw from over-spinning, once the screw is fully penetrated and flushed
within the board.
[0034] In one embodiment, the major diameter DMH2 of the high thread is
the same in
the counter thread region as the major diameter DMH1 along the rest of the
shank. However,
in an alternative embodiment, the major diameter DMH2 of the high thread in
the counter
thread region (CTR), is greater than the major diameter DMH1 of the high
thread on the shank
between the first axial location 32 and the tapered end 16. In one embodiment,
the major
diameter DMH2 of the high thread in the counter thread region is between
0.190" and 0.205"
(such as between 0.195" and 0.200") and the major diameter DMH1 of the high
thread
between the first axial location 32 and the tapered end 16 is between 0.175"
and 0.195" (such
as between 0.181" and 0.198"). In one embodiment, the shank in the counter
thread region
may have a diameter Dmc that is slightly larger than diameter Dm, as in the
screw described
above. However, in the illustrated embodiment, the counter thread region (CTR)
has a minor
diameter Dmc that is substantially equal to the minor diameter Dm of both the
high thread and
the low thread along the rest of the shank.
[0035] The subject cement board screw includes advantageous features
that improve
performance. In particular, the asymmetric high thread profile improves
pullout resistance,
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inclusion of both high and low threads renders a smoother finish in harder
cement boards and
wood studs, the wedge cut with sharp tip penetrates well into harder cement
boards and harder
woods and metal studs, the counter threads crush cement board fibers and
render a smoother
finish, the textured screw head end face allows bonding of finishing
materials, adhesives,
plasters, and fillers, the larger head nibs bite into the cement board during
seating reducing
torque to seat and the smaller nibs help in rendering smooth finish and flush
seating.
[0036] What is claimed is:
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