Note: Descriptions are shown in the official language in which they were submitted.
CA 02583890 2007-04-04
MUSHROOM COMPACTION AND ASYMMETRIC-THREAD
IMPACT-DRIVABLE SCREW
BACKGROUND OF THE INVENTION
1. Field of the Invention.
The present invention relates to the field of impact drivable screws. In
particular, the
present invention relates specifically to an asymmetric thread screw having a
ballistic point for
use with impact drivers along with a high degree crest angle forming a long
surface area slide
flank and a short surface area grip flank to reduce fiber cutting during
impact insertion of the
screwnail. A secondary mushroom compaction thread is also disclosed.
2. Description of the Known Art.
As will be appreciated by those skilled in the art, symmetrical thread screws,
self drilling
screws, and screws with cutting points have been known for an extended period
of time. Present
construction techniques use screws with a cutting or self tapping head that
are rotated into a
material to connect different materials together. This is very time consuming
because of the
extended time period it takes to rotate the screw into the material.
Other techniques use a combination of glue and regular nails in an attempt to
achieve a
similar holding power to the rotated screws. This creates a permanent
attachment that cannot be
disassembled. Similarly, the use of regular nails creates a strong bind that
is difficult if not
impossible to disassemble.
HITACHI has recently attempted impact driving screws with prior art type screw
designs
using a cutting point and a sharp angled thread on a wide thread pitch. These
screws rip and tear
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CA 02583890 2007-04-04
the wood fibers during installation. See http://www.hitachipowertools.com for
the limited
information on their design.
Patents disclosing information relevant to screws include: United States
Patent No.
137,414, issued to Burdick on April 1, 1873; United States Patent No. 276,541,
issued to Sloan
on April 24, 1883; United States Patent No. 327,296, issued to McGinnis on
Sept. 29, 1885;
United States Patent No. 373,074, issued to Jones on Nov. 15, 1887; United
States Patent No.
426,008, issued to Groff on April 22, 1890; United States Patent No. 471,179,
issued to Jones on
Mar. 22, 1892; United States Patent No. 676,240, issued to Latty on June 11,
1901; United States
Patent No. 1,326,910, issued to Butterfield on Jan 6, 1920; United States
Patent No. 1,891,895,
issued to Nagel on Dec. 20, 1932; United States Patent No. 1,912,222, issued
to Rosenberg on
May 30, 1933; United States Patent No. 1,953,592, issued to Deniston on April
3, 1934; United
States Patent No. 2,001,869, issued to Deniston on May 21, 1935; United States
Patent No.
2,046,837, issued to Phillips on July 7, 1936; United States Patent No.
2,075,411, issued to
Mertens on March 30, 1937; United States Patent No. 2,093,610, issued to
Kraemer on
September 21, 1937; United States Patent No. 2,190,883, issued to Pauze on
February 20, 1940;
United States Patent No. 2,269,708, issued to Dickson on January 30, 1942;
United States Patent
No. 2,558,379, issued to Phipard on June 26, 1951; United States Patent No.
2,605,867, issued to
Goodwin on Aug. 5, 1952; United States Patent No. 2,967,448, issued to Hallock
on January 10,
1961; United States Patent No. 3,010,353, issued to Psaros on November 28,
1961; United States
Patent No. 3,019,460, issued to Corckram on February 6, 1962; United States
Patent No.
3,056,234, issued to Nelsson et al. on Oct. 2, 1962; United States Patent No.
3,204,516, issued to
Wieber on Sept. 7, 1965; United States Patent No. 3,850,073, issued to Hayes
on November 26,
1974; United States Patent No. 3,861,527, issued to Perkins on January 21,
1965; United States
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Patent No. 3,977,142, issued to Dove et al. on Aug. 31, 1976; United States
Patent No.
4,572,720, issued to Rockenfeller et al. on Feb. 25, 1986; United States
Patent No. 4,718,802,
issued to Rockenfeller, et al. on January 12, 1988; United States Patent No.
4,932,820, issued to
Schniedermeier on June 12, 1990; United States Patent No. 5,375,957, issued to
Golledge on
Dec. 27, 1994; and United States Patent No. 5,741,104, issued to Lat et al. on
Apr. 21, 1998.
Each of these patents is hereby expressly incorporated by reference in its
entirety. These prior
art references teach that screws should cut the wood fibers with a cutting or
pyramid shaped
point during insertion. Thus, it may be seen that these prior art patents are
very limited in their
teaching and utilization, and an improved impact drivable screwnail is needed
to overcome these
limitations.
SUMMARY OF THE INVENTION
The present invention is directed to an improved screw nail. In accordance
with one
exemplary embodiment of the present invention, an asymmetric thread impact
drivable screw is
provided using an impact head and a conical shaped tip having a ballistic
insertion angle formed
on the ends of a shank defining an axis. Of particular note is the use of the
ballistic tip with the
shank defining asymmetrical threads. The ballistic tip and the threads have a
unique shape
adapted for dividing the wood fibers while minimizing the cutting or breakage
of the wood
fibers. The thread has an insertion flank protruding from the shank at slide
angle to push the
fibers aside and allow for penetration of the wood without cutting the fibers.
The slide angle has
a long surface area leading to a crest that is supported on the back side by a
catch flank. The
catch flank is protruding from the shank at an impact supporting grip angle
that provides the
necessary support to the crest during impact insertion while still providing
increased gripping
strength when compared to bare nail shanks.
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In another embodiment, the screws nails are collated into a clip for use with
an impact
fastener such as a pneumatic or gas operated nail gun.
In yet a further embodiment, the use of mushroom compaction threads are also
disclosed.
These and other objects and advantages of the present invention, along with
features of
novelty appurtenant thereto, will appear or become apparent by reviewing the
following detailed
description of the invention.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
In the following drawings, which form a part of the specification and which
are to be
construed in conjunction therewith, and in which like reference numerals have
been employed
throughout wherever possible to indicate like parts in the various views:
Figure 1 is a top view of a screwnail showing a Phillips head.
Figure 2 is a side view of a screwnail showing the ballistic point and unique
thread
configuration.
Figure 3 is an enlarged view of the unique thread configuration showing the
elongated
slide flank and the crest angle supported by the grip flank.
Figure 4 is a top view of a screwnail showing a square drive head.
Figure 5 is a side view of a screwnail showing the ballistic point, non -
threaded shaft
section and unique thread configuration.
Figure 6 is a top view of a screwnail showing a slot head.
Figure 7 is a side view of a screwnail showing the ballistic point, non-
threaded shaft
section and multiple thread sections.
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Figure 8 is a side view of a screwnail clip showing wire collating strips
connecting
multiple asymmetric thread screws using the unique thread configuration.
Figure 9 is a side view of a screwnail clip showing plastic collating strips
connecting
multiple asymmetric thread screws using the unique thread configuration.
Figure 10 is a side view of a screwnail showing a raised hex head.
Figure l l is a side view of a screwnail clip showing a paper collating strips
connecting
multiple asymmetric thread screws in a clipped head configuration.
Figure 12 is a top view of a screwnail showing a clipped phillips head.
Figure 13 is a top view of a screwnail showing a square drive head.
Figure 14 is a side view of a screwnail showing the ballistic point, unique
thread
configuration, mushroom compaction threads, and driving head.
Figure 15 is a cutaway view of a board with a mushroom compaction slide thread
screwnail installed.
Figure 16 is a cutaway view of a board with a mushroom compaction slide thread
screwnail installed and showing the opposite side and the resulting hole in
the composite.
DETAILED DESCRIPTION OF THE INVENTION
As shown in Figures 8 and 9 of the drawings, exemplary embodiments of the
present
invention are generally shown as an asymmetric thread impact drivable screw
clips 100 having
asymmetric thread impact drivable screws 300 connected by a collating strip
200. The collating
strip 200 may be made from any conventional material including wire, paper,
plastics, epoxies,
or other known materials and is typically made from a wire 202 as shown in
Figure 8, or a plastic
strip 204 as shown in Figure 9. Strips, sheets, lines, and other known
collating schemes may be
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used with the present invention. Alternative embodiments may include coiled
strips, ratcheting
strips, or other constructions.
As shown in Figures 1 through 9, the asymmetric thread impact drivable screw
300 has
an impact head 310 with a top surface 312 having a head diameter HD defining a
tool receiving
recess 314. The counter sunk head shown is the preferred design, although any
of the other head
types may be implemented if it is compatible with the type of impact tool
being utilized. Figure
1 shows a number two phillips aperture 316, Figure 4 shows a number two square
aperture 318,
and Figure 6 shows a slot aperture 319 which are the preferred shapes. Any
type of tool
receiving recess or bolt head design may be used that will fit in the area of
top surface 312 and
this design aspect will be dependent upon the contact head inside the impact
driver. Most impact
drivers use a flat driving hammer such that the design of the impact head may
be varied
according to the application.
For the preferred embodiment, the impact head 310 is connected with a tapered
neck.320
to the shank 340. The tapered neck has a head neck angle HA 322 used for the
countersinking of
the impact head 310 to the surface of the material that the screwnail is being
used to secure.
The opposite end of the shank 340 ends in a conical shaped tip 330 using a
ballistic
insertion point angle PA 332. The present invention teaches a unique
distinction over the prior
art teaching of diamond or cutting shaped screw point because a ballistic tip
330 is used to
separate fibers with minimal or no cutting of the wood fibers. This allows the
present invention
to work in a variety of situations, including but not limited to wood to wood,
wood to light gauge
steel, drywall to wood, drywall to steel, foam to wood, foam to steel,
subfloor attachment, roof
deck attachment, siding attachment, concrete board attachment, fiberboard
attachment, fencing
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applications, deck boards, framework, crating construction, pallet
construction, soffit installation,
concrete forms and other assemblies.
The shank 340 defines a central axis 342 running from the head end 344 to the
tip end
346. The distance form the top of the impact head 310 to the bottom of the tip
330 is shown as
the total length TL. The shank 340 defines a shank diameter SD 348 has at
least a first threaded
section 350 defining a major thread diameter TD 352. Multiple thread sections
may be used as
shown by the second threaded section 354 where the first section 350 and the
second section 354
are separated by a thread gap TG 358. The top of the first thread is shown as
the top thread TT
measurement in Figures 5 and 7. The bottom of the first thread is shown as the
thread bottom
TB measurement in Figure 7. The shank 340 may also define a non-threaded shank
section 356.
A key aspect to the present invention is the use of the ballistic point 330 to
separate the
wood fibers along with the use of asymmetrical threads 360 using a low angle
thread pitch 378
which passes the wood fibers with minimal or no tearing of the wood fibers.
The asymmetric
thread design and the fine thread shown by the pitch depth PD of the present
invention keeps the
wood fibers spread during insertion of the fastener without the large
movements caused by
changes between the maximum thread diameter and the root diameter of the
thread. Thus, the
relative high insertion speed consistency of the external shape of the present
invention minimizes
the cutting of the wood fibers during installation. The insertion without
cutting is provided by a
slide insertion flank 362 oriented at a slide angle SA 364 with a long slide
surface 366 leading to
the crest 368. The slide angle SA is shown in Figure 3 as measured from a
perpendicular line to
the axis. This allows the wood fibers to be moved to the side without cutting
into the fibers with
the threads and the fine thread of the pitch depth keeps the fibers there
without any substantial
additional damage. Once the high speed insertion is stopped, the fibers will
then close around
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the back side of the crest angle CA 370 and are caught by the grip catch flank
372 oriented at an
impact supporting grip angle GA 374 providing a short catch surface 376. Note
that the grip
angle GA 374 must be chosen so that the grip catch flank 372 can provide the
necessary strength
to the crest 368 during the high impact forces of ballistic insertion while
still providing an
increased grip for the grip catch flank 372. This slide angle SA 364, grip
angle GA 374 and crest
angle CA 370 allow for increased holding power while minimizing or eliminating
cutting of the
wood fibers. The elongated nature of the wood fibers increases the holding
power of the wood to
screw connection to provide a superior product over previously known designs.
A further
advantage is provided by the fine thread and limited damage design of the
present invention
because removal of the screwnail leaves a smooth hole like a nail removal
instead of a torn hole
that is created by a prior art type of cutting screw. Typical design
parameters are shown in the
following table:
Descr. General General General
Type .113(inch) * L .120(inch) * L .131(inch) * L
HD Head diameter 7.0 7.0 7.0
0.15 mm 0.15 mm 0.15 mm
HA Head Angle 80 80 800
2 2 t2
PA Point angle 28 28 28
5 t5 5
TL Length L L L
1.27 mm 1.27 mm 1.27 mm
TB First thread Point Point Point
bottom*
TG Thread Gap** NA NA NA
TT First Thread Top 2/3 * L 2/3 * L 2/3 * L
***
PD Pitch Distance 1.59 1.69 1.69
f 10% mm 10% mm f 10% mm
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SD Shank Diameter 2.87 3.05 3.33
0.03 mm 0.03 mm 0.03 mm
TD external thread 3.15 3.43 3.70
diameter 0.05 mm 0.05 mm 0.05 mm
SA Slide Angle 700 70 70
f2 2 2
GA Grip Angle 40 40 40
2 2 2
CA Crest Angle 110 110 110
t2 2 t2
Head type #2 phillips or #2 phillips or #2 phillips or
square square square
Material c-1010 or 1022 c-1010 or 1022 c-1010 or 1022
steel steel steel
Surface hardness Hv450 Min Hv450 Min Hv450 Min
Case Depth 0.05 mm Min 0.05 mm Min 0.05 mm Min
Bending angle 12 Min 12 Min 12 Min
Torsional 28 kg/cm Min 35 kg/cm Min 45 kg/cm Min
Strength
Coating 3um 3um 3um
* measured from head
** measured from first thread bottom to second thread top
* measured from ballistic point
The preferred embodiments use the following design parameters:
Descr. Example Example Example Example Example Example
Type .113 .113 .113 2.85 2.85 2.85
(inch) * (inch) * (inch) * (inch) * (inch) * (inch) *
1.5 (inch) 2.0 (inch) 2.5 (inch) 2 (inch) 2.5 (inch) 3 (inch)
HD Head 6.83 6.83 6.83 6.1 6.1 6.1
diameter 0.15 0.15 0.15 1 mm 1 mm 1 mm
mm mm mm
HA Head 80 80 80 80 80 80
Angle t2 f2 2 2 2 f2
PA Point 28 28 28 28 28 28
angle 5 5 5 5 5 5
TL Length 38.1 57.15 63.5 57.15 63.5 76.2
1.27 1.27 1.27 1.27 1.27 1.27
mm mm mm mm mm mm
TB First Point 34.5 34.5 Point Point Point
thread 1.0 mm ~ 1.0 mm
bottom*
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TG Thread NA 5.0 5.0 NA NA NA
Gap* * 0.5 mm 0.5 mm
TT First Head 35 40 30 42 42
Thread 1.0mm 1.0mm 1.0mm 1.0mm 1.0mm
Top * * *
PD Pitch 1.59 1.59 1.59 1.59 1.59 1.59
Distance 10% 10% 10% 10% 10% 10%
mm mm mm mm mm mm
SD Shank 2.87 2.87 2.87 2.87 2.87 2.87
Diameter 0.03 0.03 0.03 0.03 0.03 0.03
mm mm mm mm mm mm
TD external 3.15 3.15 3.15 3.15 3.15 3.15
thread 0.05 0.05 0.05 0.05 0.05 0.05
diameter mm mm mm mm mm mm
SA Slide 70 70 70 70 70 70
Angle 2 f2 2 2 2 2
GA Grip 40 40 40 40 40 40
Angle 2 f2 2 2 2 2
CA Crest 1100 110 110 110 110 110
Angle 2 2 f2 2 2 t2
Head #2 #2 #2 #2 #2 #2
type phillips phillips phillips phillips phillips phillips
or square or or square or square or square or square
square
Material c-1010 or c-1010 c-1010 or c-1010 or c-1010 or c-1010 or
1022 or 1022 1022 1022 1022 1022
steel steel steel steel steel steel
Surface Hv450 Hv450 Hv450 Hv450 Hv450 Hv450
hardness Min Min Min Min Min Min
Case 0.05 0.05 0.05 0.05 0.05 0.05
Depth mm mm mm mm mm mm
Min Min Min Min Min Min
Bending 12 Min 12 Min 12 Min 12 Min 12 Min 12 Min
angle
Torsional 28 kg/cm 28 28 kg/cm 28 kg/cm 28 kg/cm 28 kg/cm
Strength Min kg/cm Min Min Min Min
Min
Coating 3um 3um 3um 3um 3um 3um
* measured from head
** measured from first thread bottom to second thread top
CA 02583890 2007-04-04
*** measured from ballistic point
Obvious variations may be made to these examples, including varying the angles
outside
of these preferred parameters and changing thicknesses or types of coatings.
For example,
common requests for diameters of screws are 0.099, 0.100, and 0.105 inch
diameter screws with
varying lengths. Note that any type of coating may be used with this screw
design including,
galvanized coating, yellow zinc, paint, ceramic, concrete, etc... Thus, these
examples are
illustrative only and are not meant to limit the present invention. A further
example of this
variation is shown in Figures 10, 11, and 12.
Figure 10 shows how the head 310 may be varied to use a hex head or socket
type of
driver similar to the common one-quarter inch hex drives used in various
industries. Figure 11,
shows a paper collation used on a D-head shaped impact head. Note that the
head angle 322 has
been changed from the preferred embodiment's eighty degree angle to a
curvature to
accommodate the adjacent heads. Further note should be taken in Figure 11 of
the advantages
provided by the slide 366 and grip 372 configuration. As noted by Figure 11,
when screws are
placed into a tight configuration such as with a full head, offset head, or
clipped head
configuration, the threads on the shanks of the screws may contact due to
mishandling of the
screw strip on the job site. With the present invention's slide 366, the
threads of the driven
screw 380 will not catch the threads of the adjacent screw 382 remaining on
the strip because the
slide 366 will guide the driven screw 380 past the adjacent screw 382. Figure
12 shows a top
view of the d-shaped clipped head 310. Note that full head, offset head, or
clipped heads may be
utilized as appropriate. From this, it may be seen that many variations may be
utilized with the
advantages taught by the present invention.
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Figures 13, 14, 15, and 16 show the top and side views of a mushroom
compaction
asymmetric thread impact drivable screw 400. This mushroom compaction screw
400 uses a
mushroom compaction impact head 410 having a similar top surface 312 and tool
receiving
recess 314 that can define a phillips aperture 316, a square aperture 318, a
slot aperture 319, or
other appropriate tool connection shape. Instead of the tapered neck 320, the
mushroom
compaction head is almost a blunt connection using only a minimal neck fillet
420. This allows
for the capturing of any mushrooming wood fibers without the redirecting that
would be caused
by the tapered neck 320. Once again, a conical shaped tip 330 is used with a
ballistic insertion
angle 332 on the end of the shank 340. The shank 340 again defines the central
axis 342 and the
head end 344 and the tip end 346. Note head that in addition to the shank
diameter 348 and the
first threaded section 350 with the major thread diameter 352, there is second
threaded section
354 with mushroom compaction threads 454 having a mushroom compaction diameter
452. A
non-threaded shank section 356 can still be used with a thread gap 358.
The mushroom compaction threads 454 use either asymmetric or symmetrical
threads
360 with a gripping insertion flank 462 leading to a crest 468 with a
corresponding grip catch
flank 472. In this manner, both the first and second sides of the threads 454
have a short catch
surface 476. This allows for any mushrooming effect from the hole to be caught
by the insertion
side of the mushroom compaction threads 454 and pulled down into the hole to
leave a smooth
surface on the board.
Dimensions for the preferred embodiment of the mushroom compaction asymmetric
thread impact drivable screw 400 are as follows:
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Head Size HD MP 10% P1f10% MD D1 L1 L2 HT
#2 Sq. .120*L 6.68-6.99 1.41 1.69 4.06-4.18 3.43t0.05 5.5 1.0 40f2.0 2 0.1
The overall crest angle from the mushroom threads is 55 5 symmetrically
divided and
the overall length is 2.25 inches. The ballistic angle, crest angle, slide
angle and grip angle are as
previously described. The material is c-1018 or 1022 steel with a surface
hardness of Hv450
minimum and a case depth of 0.05 mm minimum. The bending angle is 12 Min with
a torsional
strength of 35 kg/cm minimum. Note that the mushrooming threads are
comparatively short in
length in this application due to the minimal, if any, mushrooming associated
with the slide angle
type of threads. This allows for use of the impact screw with most nail guns
by allowing the
penetration and holding power to be developed by the sliding threads with only
the slight amount
of compression used by the limited mushroom controlling threads. This allows
for screw
applications with the mushrooming control while still working in the limited
capabilities of
common impact drivers.
Thus, it may be seen that the present invention provides an advantage over the
prior by
using a ballistic point in combination with a unique thread design that allows
for insertion of the
screwnails with minimal or no tearing of the wood fibers.
Reference numerals used throughout the detailed description and the drawings
correspond to the following elements:
an asymmetric thread impact drivable screw clip 100
a collating strip 200
a wire 202
a plastic strip 204
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an asymmetric thread impact drivable screw 300
an impact head 310
a top surface 312
a tool receiving recess 314
a phillips aperture 3 16
a square aperture 318
a slot aperture 319
a tapered neck. 320
a neck head angle 322
a conical shaped tip 330
a ballistic insertion angle 332
a shank 340
an axis 342
a head end 344
a tip end 346
a shank diameter 348
first threaded section 350
a major thread diameter 352
second threaded section 354
a non-threaded shank section 356
a thread gap 358
asymmetrical threads 360
a slide insertion flank 362
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slide angle 364
a long slide surface 366
a crest 368
a crest angle 370
a grip catch flank 372
impact supporting grip angle 374
a short catch surface 376
thread pitch 378
driven screw 380
remaining screw 382
mushroom compaction asymmetric thread impact drivable screw 400
mushroom compaction impact head 410
neck fillet 420
mushroom compaction diameter 452
mushroom compaction threads 454
gripping insertion flank 462
crest 468
grip catch flank 472
short catch surface 476
From the foregoing, it will be seen that this invention is well adapted to
obtain all the
ends and objects herein set forth, together with other advantages which are
inherent to the
structure. It will also be understood that certain features and
subcombinations are of utility and
may be employed without reference to other features and subcombinations. This
is contemplated
CA 02583890 2007-04-04
by and is within the scope of the claims. Many possible embodiments may be
made of the
invention without departing from the scope thereof Therefore, it is to be
understood that all
matter herein set forth or shown in the accompanying drawings is to be
interpreted as illustrative
and not in a limiting sense.
When interpreting the claims of this application, method claims may be
recognized by the
explicit use of the word 'method' in the preamble of the claims and the use of
the 'ing' tense of
the active word. Method claims should not be interpreted to have particular
steps in a particular
order unless the claim element specifically referring to a previous element, a
previous action, or
the result of a previous action. Apparatus claims may be recognized by the use
of the word
'apparatus' in the preamble of the claim and should not be interpreted to have
'means plus
function language' unless the word 'means' is specifically used in the claim
element. The words
'defining,' 'having,' or 'including' should be interpreted as open ended claim
language that
allows additional elements or structures.
16
