U.S. patent application number 09/886889 was filed with the patent office on 2001-12-13 for chemically coated fasteners having improved penetration and withdrawal resistance.
Invention is credited to Godsted, Kent B., Lat, Geronimo E..
Application Number | 20010051080 09/886889 |
Document ID | / |
Family ID | 22862681 |
Filed Date | 2001-12-13 |
United States Patent
Application |
20010051080 |
Kind Code |
A1 |
Godsted, Kent B. ; et
al. |
December 13, 2001 |
Chemically coated fasteners having improved penetration and
withdrawal resistance
Abstract
A polymer-coated metal fastener is provided which has both
improved ease of drive into a substrate, and improved resistance to
withdrawal from the substrate. The coated fastener is prepared by
heating a metal fastener, or a portion of it, to about
400-2000.degree. F. and cooling in an aqueous medium containing an
acrylic or modified acrylic polymer. The rapid cooling causes
formation of a thin yet durable polymer coating on the
fastener.
Inventors: |
Godsted, Kent B.;
(Grayslake, IL) ; Lat, Geronimo E.; (Ivanhoe,
IL) |
Correspondence
Address: |
Pauley Petersen Kinne & Fejer
Suite 365
2800 W. Higgins Road
Hoffman Estates
IL
60195
US
|
Family ID: |
22862681 |
Appl. No.: |
09/886889 |
Filed: |
June 21, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09886889 |
Jun 21, 2001 |
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09229792 |
Jan 13, 1999 |
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Current U.S.
Class: |
411/82.2 |
Current CPC
Class: |
F16B 33/06 20130101;
F16B 15/0092 20130101 |
Class at
Publication: |
411/82.2 |
International
Class: |
F16B 001/00 |
Claims
We claim:
1. An elongated fastener, comprising: a head portion; an elongated
shank; and an acrylic-based polymer coating covering at least part
of the elongated shank; the elongated fastener having better ease
of drive into a wooden substrate and better resistance to
withdrawal from the substrate, than a similar fastener without the
polymer coating; the polymer coating being formed by heating the
fastener to effect hardening, and quenching the heated fastener in
an aqueous medium including the acrylic-based polymer.
2. The fastener of claim 1, wherein the polymer coating comprises a
material selected from the group consisting of acrylic polymers,
chemically modified acrylic polymers, and combinations thereof.
3. The fastener of claim 1, wherein the polymer coating comprises a
material selected from the group consisting of polymers of one or
more of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl
methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate,
butyl methacrylate, 2-ethyl hexyl acrylate, 2-ethyl hexyl
methacrylate, decyl acrylate, decyl methacrylate, hydroxyethyl
acrylate, hydroxyethyl methacrylate, hydroxy propyl acrylate,
hydroxypropyl methacrylate, acrylonitrile, and derivatives and
combinations thereof.
4. The fastener of claim 1, wherein the polymer coating comprises a
material selected from the group consisting of polyacrylic acid,
polymethacrylic acid, polyethacrylic acid, poly-R acrylate, poly-R
methacrylate, polymethyl acrylate, polymethyl methacrylate,
polyethyl acrylate, polyacrylonitrile, chemically modified
derivatives thereof, and combinations of any of the foregoing.
5. The fastener of claim 1, having at least about 4% better ease of
drive than a similar fastener without the polymer coating, and at
least about 5% better withdrawal resistance than a similar fastener
without the polymer coating.
6. The fastener of claim 5, having at least about 5% better ease of
drive than a similar fastener without the polymer coating, and at
least about 20% better withdrawal resistance.
7. The fastener of claim 5, having at least about 25% better
withdrawal resistance.
8. The fastener of claim 5, having at least about 40% better
withdrawal resistance.
9. The fastener of claim 5, having at least about 50% better
withdrawal resistance.
10. The fastener of claim 1, comprising a nail.
11. The fastener of claim 1, comprising a threaded nail.
12. The fastener of claim 1, comprising a screw.
13. The fastener of claim 1, comprising a pin.
14. The fastener of claim 1, comprising a staple.
15. The fastener of claim 1, comprising a brad.
16. The fastener of claim 1, comprising a corrugated fastener.
17. The fastener of claim 1, partially coated with the polymer.
18. The fastener of claim 1, completely coated with the
polymer.
19. The fastener of claim 1, wherein the polymer coating has a
thickness of about 0.00001 to about 0.00095 inch.
20. The fastener of claim 1, wherein the polymer coating has a
thickness of about 0.00003 to about 0.00075 inch.
21. The fastener of claim 1, wherein the polymer coating has a
thickness of about 0.00004 to about 0.00060 inch.
22. A method of improving both the ease of drive and ease of
withdrawal of a metal fastener, comprising the steps of: heating at
least a portion of an elongated metal fastener to a temperature of
about 400-2000.degree. F.; cooling at least the heated portion of
the fastener in an aqueous polymer medium; the polymer medium
including about 5-99% by weight water and about 1-95% by weight of
a polymer selected from the group consisting of acrylic polymers,
chemically modified acrylic polymers, and combinations thereof; the
quenching resulting in a polymer coating covering at least the
heated portion of the fastener; and drying the fastener.
23. The method of claim 22, wherein at least the heated portion of
the fastener is cooled for less than about 30 seconds.
24. The method of claim 22, wherein at least the heated portion of
the fastener is cooled for about 3-10 seconds.
25. The method of claim 22, wherein the aqueous medium comprises
about 50-98% by weight water and about 2-50% by weight of the
polymer.
26. The method of claim 22, wherein the aqueous medium comprises
about 75-97% by weight water and about 3-25% by weight of the
polymer.
27. The method of claim 22, wherein the heating temperature is
about 500-1800.degree. F.
28. The method of claim 22, wherein the heating temperature is
about 500-1700.degree. F.
29. An elongated fastener having improved ease of drive and
improved resistance to withdrawal, prepared by a process comprising
the steps of: heating at least a portion of an elongated metal
fastener to a temperature of about 400-2000.degree. F.; cooling at
least the heated portion of the fastener in an aqueous polymer
medium including a polymer selected from the group consisting of
acrylic polymers, chemically modified acrylic polymers, and
combinations thereof to provide a polymer coating covering at least
the heated portion of the fastener; and drying the fastener.
Description
FIELD OF THE INVENTION
[0001] This invention relates to chemically coated fasteners having
improved ease of penetration into a substrate, and improved
resistance to withdrawal from the substrate. This invention also
includes a process for preparing the chemically coated fasteners
which is integral with a heat treating and hardening process, and
does not require separate cleaning of the fasteners.
BACKGROUND OF THE INVENTION
[0002] Chemical coatings on objects have been employed for the
purposes of protecting the objects from corrosion and imparting
aesthetic properties. The coated objects can be made from metals
such as steel, iron, aluminum, or the like, or from other materials
such as wood, plastic or paper. U.S. Pat. No. 5,283,280, issued to
Whyte, discloses a process in which an aqueous bath containing a
polymer solution is heated to about 80-160.degree. F. A metal
object is heated to about 220-1700.degree. F. and immersed in the
bath, causing a polymer coating to form on the surface of the
object. Examples of suitable polymer solutions include those
containing water-reducible alkyd resins, acrylic polymers,
urethanes, multi-functional carbodiimides, melamine formaldehyde
resins, styrene-acrylic copolymers, and polyolefin waxes.
[0003] Aqueous polymer coatings useful for coating objects are also
disclosed in U.S. Pat. Nos. 5,458,659; 5,605,722; 5,605,952;
5,605,953; and 5,609,965; all of which are issued to Esser. All of
these patents are directed to providing protective coatings or
aesthetic finishes on various substrates.
[0004] In the construction industry, there is always a need or
desire for fasteners having easier penetration into wood, metal and
other substrates. Fasteners such as nails, for instance, are
typically driven into substrates using nail guns and other power
tools. Fasteners which penetrate substrates more easily reduce the
energy, and often the weight, required for a power driving
tool.
[0005] There is also a need and desire in the construction industry
for nails and other fasteners which remain embedded in the
substrate, and do not easily retract or withdraw from the
substrate. Unfortunately, fasteners which are relatively easy to
drive into a substrate often tend to withdraw more easily.
Fasteners which are more difficult to withdraw also tend to be more
difficult to drive into the substrate. Thus, it has been relatively
difficult to develop fasteners which have excellent ease of
penetration as well as strong resistance to withdrawal.
SUMMARY OF THE INVENTION
[0006] The present invention is directed to an elongated fastener
which has improved ease of drive into a substrate, as well as
improved withdrawal resistance, and a method for coating the
improved fastener which can be integrated with an in-line heat
treatment and hardening process.
[0007] In accordance with the invention, an elongated metal
fastener (for example, a nail) is first heated to a temperature of
about 500-2000.degree. F. An aqueous solution or mixture is
prepared containing about 5-99% by weight water and about 1-95% by
weight of an acrylic or modified acrylic polymer or copolymer,
and/or a derivative thereof. The heated fastener is then quenched
(i.e. rapidly cooled) by immersing it in the aqueous polymer
solution or mixture. It is not necessary to clean the fastener (to
remove oils, etc.) before heating and quenching it.
[0008] The rapid cooling of the fastener causes the formation of a
substantially uniform and stable coating of the polymer on the
fastener surface. When the fastener is heated to the above
temperature range before quenching, and quenched using the
described polymer bath, the resulting polymer coated fastener
exhibits surprising and unexpected properties. Specifically, the
coated fastener exhibits a combination of improved ease of drive
into a wood substrate, and improved resistance to withdrawal,
compared to a similar but uncoated fastener. Because no cleaning of
the fastener is required, the polymer coating step can be part of
an in-line process during which the fasteners are partially or
totally heat treated, to effect hardening.
[0009] The coated fasteners of the invention exhibit these improved
properties regardless of whether or not the fasteners are washed
prior to coating. Also, the chemical coating does not inhibit the
resistance welding of fasteners to one or more collation wires, to
form a collated fastener assembly. This may be due to the fact that
the resulting chemical coating is very thin or discontinuous (e.g.
cracked) so that the electrical conductivity through the coating is
not compromised.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 illustrates a row of elongated fasteners, welded to
two wires to form a collation.
[0011] FIG. 2 is a top view of a heating apparatus for elongated
fasteners.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
[0012] Referring to FIG. 1, a collation 10 includes a row of
elongated fasteners 12, which are nails, maintained in position by
wires 14 and 16 which are welded to the fasteners. Each fastener 12
includes a head portion 18 and an elongated shank portion 20. Each
shank 20 includes an upper smooth portion 22 adjacent the head, an
upper threaded portion 24 adjacent the upper smooth portion 22, a
smooth land portion 26 adjacent the upper threaded portion 24, a
lower threaded portion 28 adjacent the land 26, and a pointed end
30. The invention is not limited to threaded nails, but is also
applicable to smooth nails, brads, staples, corrugated fasteners,
and other elongated fasteners. Alternatively, the threaded portion
could extend to the head.
[0013] Depending on the end use application, and the substrate into
which fasteners 12 are driven, the fasteners 12 may be constructed
from suitable metals, including without limitation various alloys
of carbon steel and stainless steel, aluminum, copper, bronze,
nickel, and combinations thereof. For many construction
applications, fasteners 12 may be constructed from carbon steel.
The wires 24 and 26 may be constructed from any suitable metal
which can be welded to the fasteners, including the above-listed
metals and alloys.
[0014] Each of the fasteners 12 is coated with a thin polymer
coating 34. Depending on the specific application, the polymer
coating 34 may cover one or more select portions of each fastener
12, or the entire fastener 12. Preferably, the coating covers all
portions of the fastener because this can be easily accomplished
in-line by dropping a heated fastener into a quenching bath
containing the polymer. In the embodiment shown, the polymer
coating 34 covers the end 30, lower threaded portion 28, land 26,
and upper threaded portion 24 of each fastener, and terminates in
the upper smooth portion 22. As stated above, the polymer coating
34 may be discontinuous due to cracking or other separation
resulting from its thinness, and/or rapid cooling during
quenching.
[0015] The polymer coating 34 includes a polymer selected from the
group consisting of acrylic polymers and copolymers, modified
acrylic polymers, and copolymers, and derivatives and combinations
of the foregoing. Suitable polymers include polymers of one or more
of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl
methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate,
butyl methacrylate, 2-ethyl hexyl acrylate, 2-ethyl hexyl
methacrylate, decyl acrylate, decyl methacrylate, hydroxyethyl
acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate,
hydroxypropyl methacrylate, acrylonitrile, and derivatives and
combinations thereof. Some suitable polymers include, without
limitation, polyacrylic acid, polymethacrylic acid, polyethacrylic
acid, poly-R acrylate, poly-R methacrylate, polymethyl acrylate,
polymethyl methacrylate, polyethyl acrylate, polyacrylonitrile,
chemically modified derivatives thereof, and combinations of any of
the foregoing. Other suitable polymers are identified in the
aforementioned patents to whyte and Esser, the disclosures of which
are incorporated by reference.
[0016] The polymer coating 34 should be thin and/or discontinuous
enough so as not to significantly interfere with the welding of the
fasteners 12 to the wires 14 and 16. In the embodiment illustrated,
wire 16 must be welded to the fasteners 12 through the polymer
coating 34, while wire 14 is welded to the fasteners 12 without
exposure to polymer. For example, the polymer coating 32 should be
thin and/or discontinuous enough that wires 14 and 16 can be welded
to the fasteners using the same welding apparatus, technique and
conditions.
[0017] The polymer coating 34 should have a thickness sufficient to
improve both the ease of drive and the resistance to withdrawal of
the fastener 12. If the coating 34 is too thick or too thin, any
improvement in either the ease of drive or withdrawal resistance
may be lessened or eliminated. Desirably, polymer coating 34 should
have a thickness of about 0.00001 to about 0.00095 inch.
Preferably, the coating thickness should be about 0.00003 to about
0.00075 inch, most preferably about 0.00004 to about 0.00060
inch.
[0018] In addition to the polymer coating type and thickness, the
method of application is also important for achieving the desired
end use properties. Before applying the polymer coating 34, the
fasteners 12 are heated to a very high temperature. The fasteners
12 should be heated to about 400-2000.degree. F., preferably about
500-1800.degree. F., most preferably about 500-1700.degree. F. If
only portions of the fasteners need to be coated, then it is only
necessary to heat those portions to the desired temperature. If
heat treatment is employed to harden all or part of each fastener,
it is highly advantageous to integrate the hardening and coating
processes by using a polymer solution to cool or quench the heat
treated fasteners. No intermediate cleaning of fasteners to remove
oils, etc., is required.
[0019] The fasteners 12, or the specific portions of fasteners 12
requiring coating, are then quenched (rapidly cooled) using an
aqueous medium containing the polymer. Preferably, the entire
fasteners are cooled, because this can be conveniently accomplished
by dropping the fasteners into the aqueous medium containing the
polymer. The coating polymer may be present in the aqueous medium
in the form of a solution, emulsion, dispersion, colloidal
suspension, or other type of mixture. Preferably, the polymer is
substantially homogeneously dispersed in the aqueous medium. The
aqueous medium may include about 1-95% by weight of the polymer,
preferably about 2-50% by weight of the polymer, most preferably
about 3-25% by weight of the polymer. Dilute solutions or
dispersions of the polymer are preferred, because of the need to
form only a very thin polymer coating on the fasteners, and to
minimize the cost of the coating material.
[0020] The temperature of the aqueous polymer medium may range from
about 40-200.degree. F., preferably about 50-150.degree. F., more
preferably about 60-120.degree. F. If the volume of the aqueous
polymer medium is large enough to prevent overheating from the
fasteners being quenched, there is Generally no need to otherwise
heat or cool the aqueous polymer medium.
[0021] The method of application of the aqueous polymer medium to
quench and coat the fasteners may depend on whether all, or only
portions, of fasteners 12 are being polymer coated. Generally, the
aqueous polymer medium may be applied to the fasteners by
immersion, dipping, spraying, jetting, and other techniques. If the
entire fastener 12 is being coated, it may be desirable to simply
dip or drop each fastener into a bath containing the aqueous
polymer medium. If only an upper or lower portion of each fastener
is being coated, as shown in FIG. 1, it may be desirable to dip
only that portion into a bath containing the aqueous polymer
medium. If an isolated intermediate portion or portions are being
coated, it may be desirable to use a jet or spray of the aqueous
polymer medium, directed at only those portions.
[0022] Desirably, the fasteners are removed from the quench medium
after a relatively short time of less than 30 seconds, preferably
3-10 seconds. Extended quench times may permit the polymer coating
on the nail to redissolve in the bath. Also, removal of fasteners
which are still warm facilitates drying of the coating on the
fasteners.
[0023] The combination of heating of the fastener followed by rapid
cooling, employing the above parameters for heating temperature and
quench fluid composition, yields a polymer coating 34 which is thin
yet effective. The fasteners 12 need not be previously cleaned to
remove surface oils and contaminants, before coating. Regardless of
whether or not the fasteners 12 are cleaned prior to coating, the
coated fasteners 12 exhibit a surprising combination of improved
ease of drive and resistance to withdrawal, from a wood substrate.
The improved ease of drive also permits smaller diameter fasteners
to be used, resulting in cost savings and further improvements in
the ease of drive.
[0024] The particular substrate employed depends on the type of
fastener 12 and the end use application. Particularly useful
substrates include various types of wood as used in the
construction industry. Other possible substrates may include metal
plates, concrete beams and blocks, bricks, polymer composites, and
other construction materials. The different types of fasteners
which can be coated include nails, screws, hybrids such as threaded
and partially threaded nails, pins, staples, brads, corrugated
fasteners, and other fasteners.
[0025] Various techniques can also be employed for heating the
fasteners 12 prior to coating with the polymer. FIG. 2
schematically illustrates an apparatus 100 useful for continuously
heating a large number of fasteners such as illustrated in FIG. 1,
wherein less than the entire fastener requires heating. A flammable
gas from a source (not shown) enters the apparatus and is injected
into a semi-circular manifold 108 located on a base 102. Firing
burners 110 receive flammable gas from the manifold 108. Firing
burners 11 each include a nozzle 114 which fires burning gas
outward toward a semi-circular exhaust chamber 116.
[0026] A central disk 118 having a toothed outer periphery is
rotated immediately above the firing burners 110. A chain 124 is
located radially outward of the disk during rotation of the disk
for approximately 270.degree.. The chain 124 and outer periphery of
disk 118 travel at the same speed and hold the fasteners 12 in a
substantially vertical orientation in front of burners 110. When
not in contact with disk 118, the chain 124 passes around a series
of sprockets remote from the disk.
[0027] The fasteners 12 enter the furnace via inlet conveyor 122,
whereupon they are inserted into openings between disk 118 and
chain 124, and are captured between the disk and chain. As the disk
118 travels in the circular path, each of the fasteners 12 is
successively exposed to, and heated by, the burners 110. After
passing the last burner 110, the fasteners 12 pass to the exit
chamber 126, whereupon they are ejected and quenched. In accordance
with the invention, fasteners 12 are dropped into a water bath
containing the polymer, so that they may be quenched and coated
with polymer simultaneously in an integrated hardening and polymer
coating process.
[0028] The carrier disk 1 18 and chain 124 may define over 100, and
possibly several hundred linkage openings. Thus, the apparatus 100
may heat a large number of fasteners on a continuous basis, to very
high temperatures. By varying the size and positions of the burners
110, the apparatus 100 can be used to heat select narrow portions
of the fasteners, or wide portions, or substantially the entire
fasteners. For example, the apparatus is useful for heating the
lower portions of fasteners 12 which are then coated as shown in
FIG. 1.
EXAMPLE
[0029] For the following Examples, threaded carbon steel nails
having a length of 2.25 inch, a blank diameter of 0.099 inch, no
lands, a blunt chisel point, a standard (flat) head configuration,
and a thread diameter 10-14% over the blank diameter were employed.
For each Example, the nails were heated in a forced air oven to
about 850.degree. F., and then were dropped into an aqueous
polymeric quench bath for approximately three to five seconds. The
coated nails were then removed from the quench bath, and the
residual warmth in the nails dried the coating.
[0030] Four quench bath compositions were tested. Composition No. 1
contained one volume part water per one volume part ELMCO.RTM.
Coating 59. ELMCO.RTM. Coating 59 was a developmental aqueous
acrylic polymer-based composition obtained from Elmco Co. of
Lafayette, Ind. Composition No. 2 contained two volume parts water
per one volume part ELMCO.RTM. Coating 59. By adding water to an
already dilute aqueous-based coating, the quench compositions were
made sufficiently dilute to provide the desired thin polymer
coating.
[0031] Composition No. 3 contained one volume part water per one
volume part ELMCO.RTM. Coating 50. ELMCO.RTM. Coating 50 was a
developmental aqueous modified acrylic polymer-based composition
obtained from Elmco Co. The difference between Coating 59 and
Coating 50 is that Coating 59 may redissolve on a coated part if
the quenching residence time is too long. Coating 50 will not
redissolve. Composition No. 4 contained two volume parts water per
one volume part ELMCO.RTM. Coating 50.
[0032] The coated nails were initially driven into pine wood using
a power driving tool at constant driving pressure, sufficient to
drive the nails into the wood to a desired constant depth. For each
Example, fifteen coated nails were driven into the wood,
alternating with fifteen uncoated precursor "control" nails of the
same type. The driven nails were tested for withdrawal resistance
as follows. The head of each nail was clamped into a tensile
testing machine. The nail was withdrawn at a rate of 0.10 inch per
minute. A graphing mechanism and digital readout were used to
monitor the varying force needed to withdraw the nail. Typically,
the separating force rose to a peak and then fell, as the nail was
withdrawn. The maximum force in pounds was recorded, and divided by
the length of the nail originally embedded in the wood, to
determine the pounds per inch withdrawal.
[0033] To measure the ease of drive, the power driving tool was set
at a driving pressure insufficient to completely drive the nails of
each Example, and some of the control nails, into the wood. The
height of each incompletely driven nail remaining above the wood
surface was measured, and subtracted from the total nail length.
The resulting values represented the amount of nail length driven
into the wood for each of the nails of each Example, again placed
in alternating fashion with uncoated control nails.
[0034] The tests were run both for nails which had been prewashed
prior to coating to remove surface oils, and for unwashed nails.
The following Table 1 summarizes the average results of the
experiments.
1 TABLE 1 Withdrawal (lb/in) Ease of Drive (in) Example Coating
Composition Coated Uncoated Percent Coated Uncoated Percent Coating
No. Washed Unwashed Nails Nails Change Nails Nails Change Thickness
(in) 1 1 228 144 +58 1.64 1.54 +6 0.00006 2 1 189 113 +63 1.74 1.53
+14 0.00008 3 2 189 123 +53 1.63 1.50 +8 0.00003 4 2 163 97 +68
1.77 1.67 +6 0.00007 5 3 164 103 +59 1.58 1.44 +9 0.00006 6 3 189
121 +56 1.68 1.52 +10 0.00010 7 4 164 117 +40 1.69 1.58 +7 0.00004
8 4 164 117 +40 1.75 1.69 +5 0.00005
[0035] As shown above, the polymer coated nails in all cases had an
ease of drive at least about 5% better than the otherwise similar
uncoated control nails. In some cases, the coated nails had an ease
of drive at least about 10% better than the uncoated control
nails.
[0036] In all cases, the polymer coated nails had a withdrawal
resistance at least about 40% greater than the uncoated nails. In
most cases, the polymer coated nails had a withdrawal resistance at
least about 50% greater than the uncoated nails.
[0037] To satisfy the objectives of the invention, the polymer
coated fasteners of the invention should have at least about 4%
better ease of drive and at least about 5% better withdrawal
resistance than otherwise similar fasteners without the polymer
coating. Preferably, the polymer coated fasteners of the invention
should have at least about 5% better ease of drive and at least
about 20% better withdrawal resistance than otherwise similar
fasteners without the polymer coating. More preferably, the polymer
coated fasteners of the invention should have at least about 25%
better withdrawal resistance than otherwise similar uncoated
fasteners.
[0038] The Examples further illustrate that the polymer coating
process of the invention significantly improves both the withdrawal
resistance and ease of drive of the fasteners, regardless of
whether or not the fasteners are pre-washed to remove surface oils
and dirt. In the aggregate, there was little difference in
performance between washed and unwashed nails. The elimination of
the washing requirement is a significant process and cost
advantage.
[0039] While the embodiments of the invention disclosed herein are
presently preferred, various modifications and improvements can be
made without departing from the spirit and scope of the invention.
The scope of the invention is indicated by the appended claims, and
all changes that fall within the meaning and range of equivalents
are intended to be embraced therein.
* * * * *