Note: Descriptions are shown in the official language in which they were submitted.
z
BACKGROUND OF THE INVENTION
1. Ficld of the Inve_tion
The present invention relates to a cutting instrument formed from an
amorphous alloy. More particularly! the present invention relates to a
cutting instrument, such as a razor blade, having an amorphous alloy comp-
osition which is suitable for applying a solid fluorocarbon polymer at
elevated heating temperatures.
2. Description of the Prior Art
Amorphous alloys are known in the art. One such alloy is available
from Allied Chemical Corporation, Morristown, New Jersey, under the name
METGLAS, a registered trademark of Allied Chemical Corporation. METGLAS
alloys consist of base metals iron and nickel, as well as chromium, cobalt
and molybdenum combined with various metalloids (boron, carbon, silicon,
pllosphorus, etc.). The basic fabrication process, although varying in de-
tail with the base-metalloid combination, consists of extremely rapid
quenching from the liquid state. In this way the random atomic structure
o~ the liquid phase is retained in the solid state at ordinary temperatures.
Thus, unlike conventional metallic alloys, METGLAS materials are not aggreg-
ates of small crystals and therefore do not have the "grain boundaries"
that tend to weaken conventional alloys and make them susceptible to chem-
ical attack. On the other hand, and unlike ordinary glasses, the METGLAS
alloys are not brittle.
It is also well known in the art to coat safety razor blade cutting
edges with a solid fluorocarbon polymer. During the coating process heat
in the order of 626 F. - 700 F. is applied for about 8 to 30 minutes ~time
being varied inversely proportional
;
to the temperature) to melt the coating. Examples of processes using such
temperatures when coating safety razor blade cutting edges with a solid
fluorocarbon polymer are disclosed in U.S. Patent Nos. 3,071,856 and 3,518,110.
S MMARY OF THE INVENTION
The applicants have determined that most nickel-iron base amorphous
alloys having a high nickel content become brittle when baked at elevated
temperatures in the order of 650 F. to 675~ F. as used in the above-described
solid 1uorocarbon coating process. It is theorized that the brittle property
is caused by amorphous alloy beginning to crystallize.
IO In accordance with one aspect of the present invention there is prov-
ided a razor blade comprising: at least one strip of an amorphous alloy
comprising 60 to 70 percent by weight of iron, 2 to 10 percent by weight
nickel, 20 to 30 percent by weight of at least one metal selected from the
group consisting of chromium, cobalt, molybdenum and tungsten, 2 to 3 percent
by weight of at least one metalloid, at least one cutting edge formed on said
amorpllous alloy strip, and an adherent coating on at least said cutting edge~
said coating comprising a solid fluorocarbon polymer compound of a high mol-
ecular weight polytetrafluoroethylene dispersed on a base coating of low mol-
ecular weight polytetrafluoroethylene, said blade and coating having been
subjected to a temperature greater than approximately 626 ~. for more than
npproximately 8 minutes and less than approximately 30 minutes.
The alloy preferably includes a plurality of metalloids selected from
the group consisting of phosphorus~ boron, carbon, aluminum, sulfur, silicon,
gallium, germanium, arseni.c, selenium, and tellurium, of which the first six
elements are preferred, particularly the first three. Preferred alloys,
furthermore, are those containing 10 to 20 percent by weight o:E chromium and
molybdenum, or 10 to 20 percent by weight of chromium or molybdenum, or 10 to
20 percent by weight of chromium.
In another aspect of the invention, applicants have determined that a
nickel-iron base amorphous alloy of high nickel and low iron content having
t~
a relatively high cobalt content may be subjected to elevated coating temp-
eratures without embrittlement. In accordance with this aspect of the pres-
ent invcntion, there is provided a razor blade comprising: a strip of an
amorphous alloy comprising approximately 5.4 percent by weight of iron,
approximately 51.3 percent by weight of nickel, approximately 10.1 percent
by weight of chromium, approximately 22.9 percent by weight of cobalt,
approximately 7.5 percent by weight of molybdenum, and 2.8 percent by weight
of boron, a cutting edge formed along a margin of said amorphous alloy strip,
and an adherent coating on said cutting edge, said coating comprising a
ll~ solid 1uorocarbon polymer composed of a high molecular weight polytetra-
fluoroetllylene dispersed on a base coating of low molecular weight poly-
tetrafluoroethylene, said blade and coating having been subjected to a temp-
erature greater than approximately 626 F. and less than approximately 700 F.
for more than approximately 8 minutes and less than approximately 30 minutes.
DESCRIPTION OF SPECIFIC EMBODIMENTS
As noted above, the cutting edges of safety razor blades are generally
coated with a solid fluorocarbon polymer normally comprising a dispersion of
polytetrafluoroethylene. United States Patent Nos. 3,~71,856 and 3,518,110
disclose the nature and purpose of such coatings and the processes by which
they are placed on the cutting edges. United States Patent No. 3,518,110,
in Colunms 4, 5 and 6, Examples 1 through 10, demonstrates that temperatures
~etween approximately 626 F. and 698 F. may be successfully employed to
acllieve useful coatings of polytetrafluoroethylene when the blades are sub-
jected to such temperatures for appropriate periods of time. Generally the
prior art shows that the achieving of a temperature above the melting point
of the polymer for sufficient time so as to achieve a uniform coating of the
edge produces a useful blade edge coating.
The following example provides for coating various amorphous alloy
blade cutting edges with a high molecular weight polytetrafluoroethylene dis-
persed on a base coating of a low molecular weight polytetrafluoroethylene.
~79~2
Examp]e
; A dispersion of fluorocarbon telomer VYDAX 1000, a registered trade-
mark of DuPont Corporation, havi.ng a molecular weight of approxima~ely
20,000 is diluted by mixing with trichlorotrifluoethanc to obtain a solids
level of 7.5 percent by weight. Nine parts of this mixture is then
- -4a-
,
subsequently dlluted with 24 parts tertiarybutyl-alcohol and
5 parts tetrachlorodifluoroethane~ The mixture .is then placed in
an a.ir spray recirculat.ing system pressure vessel us.ing l.ine
pressure of 2 to 8 psi and a fluid heater to prevent freez.ing.
The blades are sprayed uslng a gaseous atom.izing pressure of
20-40 ps.i while the blades are transversed in front of the spray-
.ing guns at a rate of 3-25 feet per minute.
Having successfully applied the base telomer, the blades
are preheated via a holding oven/ induction heater, or infra-
red heater until the temperatures of the blades are stabilizedbetween 140 F. and 200 F. As the blades attain this temperature,
they are then processed through a second spray system containing
a non-recirculating but pressurized vessel containing a tank
pressure of 1-10 psi and an atomizing pressure from 3-40 psi which
is spraying a d.iluted mixture of polytetrafluoroethylene particles,
containing one part DuPont's Teflon PTFE Product Type 30 wlth
50-70 percent solids by weight and 9 parts of deionized water
while the blades transverse at a rate of about 3-25 feet per minute.
Having appl.ied both coatings to the desired degree, the
blade is placed in an atmosphere controlled furnace. The atmosphere
may be a reducing atmosphere such as dissociated ammonia or an
.inert atmosphere such as nitrogen gas and the blade is raised
.in temperatures 650 F to 675 F. as rapidly as poss.ible above the
s.intering temperature of both materials, and held for a period of
~5 8-30 minutes at that temperature followed by a subsequent rap:id
cool.ing cycle.
Samples of amorphous alloys produced by Allied Chemical
Corporation under the trade name METGLAS were subjected to ele-
vated temperatures typically used when coating blade edges with a
~'7~1~2
solid fluorocarbon polymer. The cornpositions of the samples are
given in Table I.
T A B L E
Element in Weight Sample No.
Percent 1 _ 2 3 4 5
Iron 69.4 64.165.1 35.7 5.4
Nickel 1.9 5.0 9.6 41.4 51.3
Chromium 4.0 5.017.1 15.4 10.1
Cobalt 2.2 3.2 6.2 0 22.9
Copper 0 0 0 0 0
Molybdenu~ 20.1 20.0 0 0 7.5
Phosphorous 0 0 0 6.5 0
Silicon 0.28 0.570.13 0 0
Boron 2.2 2.1 1.9 loO 2.8
Samples 1 through 4 were each divided into six strips of
at least six inches in length. The thickness and width dimensions
or the sample strips are given in inches in parentheses in left-
hand "Sample" column of I'able II. Five of the strips of each
sample were subjected to respectively di~ferent temperatures for
30 minutes as shown in Table II. Sample 5 was subjected only to
the 700 F. test, previous experience having shown such temperature
to be the most critical to performance of the material and its
adaptability to the fabrication of razor blades.
The six strips of Samples 1 through 4 and test Sample 5
were then subjected to a break test in which a loop of each portion
of 0.5 to 0.75 inch is inserted between two flat and parallel
plates of a table micrometer, and compressed until the loop breaks.
The distances, in thousandths of an inch, separating the plates at
the time of breakage for the portions are recorded in Table II.
However, it will be noted from Table II that Samples 1, 2, 3 and
5 as received, Sample 3 subjected to 600 F. and Sample 5 (Mirror
; surface out only) subjected to 700 F. for 30 minutes were suffi-
ciently ductile so as to avoid breakage during the blending test.
:
.
.his failure to break indicates the materials as being in a highly
amorphous condition which is desirable to the fabrication of
cutting edges.
It is noted that the strips of Metglas tested have one
highly reflectant surface and an opposing relatively dull surface.
As shown in Table II, a portion of each strip was subjected to
the break test with the reflectant surface facing outwardly (MO),
and another portion of each strip was tested with the reflectant
surface facing inwardly (MI). The designation TB (too brit-tle)
indicates fracture of the material prior to achieving a measurable
bend dimension within the test fixture. This is assumed as
indicating the material has crystallized to a point where its
desirable characteristics have sufficiently diminished due to
time temperature conditions as to obviate its applicability to
razor blade fabrication in accordance with the processes described
herein.
--7---
H m m m m
oo
a~ o m m m m
E4 H m ~ m m
o ~
o
U~ U~
~ o m CO m m
~ In
o ~
o
O o m m U~ m m
H . ISl ~ Il'~
1-1 1:4 H ~`1 ~ ~ m
O
o U~
in u~
i~ ~D O ~O ~ ~ m
m ~ a
~ ~ ~:
E~ ~
~ ~ CO I ~ o
F4 :~ ~D ~ mz
o
O u, o I ~ a~
~O o ~ o m ~ 1 Q
Z
~
11
a
, . a) o
H m m m o m ~ o
~, ~: æ z z ~ æ ~ o ~
P; cq ~ ~,
o m m m ~ m
U~ ~ ~; Z Z ~ Z ~ ~ ~
rd ~ C)
.,~,"~
a) ~
o
l~ ~ o
O O
O H a)
a) xxxxx
~ ~ Q
1~ .~ O
ni o o o o o -.~ O o
u~ ooooo
~_ _ _, _ ~_ 11 11 11 11 11
OH u~m m
~ Z
~7~9~
The data of Table II shows that the four strips of
Sample 4 when respect.ively heated for 30 m.inutes at 650 F.,
700 F., 750 F and 930 Fo were so brlttle that they could not
be looped in preparation for the break test. However, the strips
of Samples 1 and 2 d,id not become two brittle for the test unt,il
heated at 700 F., and the str,ips of Sample 3 d.id not become too
brittle until 750 F. It is bel.ieved that the brittleness
property is caused by the alloys beglnn.ing to crystall,ize.
Sample 5 did not become too br.ittle when subjected to a tempera-
ture of 700 F.
The data show that the alloys of Samples 1 and 2 aresuitable for coat.ing w.ith polytetrafluoroethylene employing
processes carried on at temperatures up to approximately 650 F.
Subsequent testing has indicated that the temperature range may
be extended to above 675 F. without detrimental effect. The
alloys of Samples 3 and 5 are shown to be suitable for processes
employing temperature ranges up to and exceeding 700 F. w.ithout
resultant embrittlement of the material. The break.ing of samples
at various bending d.istances shown in the table does not indicate
unsuitability for fabrication into razor blades but only the
probability that some transition to a semi~crystalline state has
occurred.
It was found subsequent to the bend testing that the
sample alloys, with the exception of Sample 4, were capable of
producing coated raæor blades with acceptable edge sharpness and
shaving comfort. It is pointed out that the provision of accept-
able shaving comfort and blade performance does not require the
two-stage, low molecular weight base coating and subsequent h.igh
molecular weight final coating, but may be achieved with a single
coating of the Vydax 1000 dlspers:ion subjected to the same
i ~
~ ~7~332
temperature ranges. The two coating process merely enhances
performance rather than altering the basic characteristicsO
The embodiments of the invention described herein are
intended as illustrative of applicants' novel concept and hence
S all those variations and modifications which are obvious to one
of ordinary skill in the art are considered to be within the
scope of the invention.
--10--
