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Патент USA US3098814

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3,098,84
Patented July 23, 1963
2
1
acid and sulfuric acid, balance water, and thereafter a
layer of metal such as nickel and/ or chromium is electro—
deposited on the anodized surface of said aluminum. By
3,098,804
METAL TREATMENT
Henry J. Wittrock, Opportunity, Wash, assignor to Kaiser
Aluminum 8; Chemical (Iorporaticn, Oakland, (Dali?,
this method, ?rmly adherent metal layers can be provided
on a wide variety of aluminum alloys.
\In carrying out the method of this invention, the object
to be treated may ?rst be mechanically buffed and pol
ished although this is not essential to the invention. The
a corporation of Delaware
No Drawing. Filed Mar. 28, 1960, Ser. No. 17,754
5 Claims. (til. 204-41)
article is then cleaned in a suitable solution such as a
This invention relates to the production of ?rmly ad
hering coatings on aluminum and aluminum alloys. 10 mild or inhibited alkaline cleaner. 'Ilhe cleaned article
may then be anodized. If a very smooth deposit is re
More particularly, this invention relates to the produc
quired on the ?nished article, the article to be plated may
tion of ?rmly adhering galvanic coatings of metals, such
first be polished by conventional brightening treatments,
as chromium and nickel, on aluminum and a variety of
aluminum alloys. This application is a continuation-in 15 e.g., chemical or electrochemical. On the other hand,
part of copending application Serial Number 828,451,
where a matte or satin appearance is desired on the ulti—
?led July 21, 1959.
mate article, the aluminum metal may be subjected to a
-
According to prior art practice, these metals have
been plated on aluminum over a preliminary zinc coat
suitable etching treatment.
The clean aluminum is immersed as an anode in an
ing produced by the well-known zincate immersion proc 20 aqueous electrolyte consisting essentially of from 5 to
ess. Usually brass or copper is plated over the thin zinc
45% by volume phosphoric acid, from 1 to 30% by vol
layer produced by this process, followed by plating with
ume sulfuric acid, balance water. An electric current
the nickel and/or chromium. Such process possesses
is passed through the electrolyte for a time period ranging
certain inherent disadvantages. The zincate process and
its attendant surface preparation is relatively complicated 25 from 1 to 30 minutes, producing an oxide coating on the
surface of the aluminum metal. A current density of
from 12 to 120 a.s.f. is maintained, using a voltage of
less than 40 volts. As used herein, the term “a.s.f.” is an
the copper, zinc and brass layers aggravate the corrosion
abbreviation of the expression “amperes per square foot.”
of the plated aluminum product.
In order to overcome these disadvantages, it has been 30 The electrolyte is maintained at a temperature ranging
from 80 to 140° F. The oxide-coated metal is then plated
proposed to produce ?rst an oxide coating by anodic
with the desired metal such as chromium and nickel.
treatment of the aluminum metal, followed by electro
Where a chromium-plated aluminum metal article is
plating of the desired metal on the oxide coating. in the
and not as easily handled as the preparation for plating of
other common base metals such as steel or brass. Also,
prior art, these oxide coatings were generally produced
to be subjected to severe corrosive environment or to
by anodizing in either an electrolyte of phosphoric acid 35 severe bending stresses or impact, it is preferred ?rst to
alone or oxalic acid alone.
Anodizing in phosphoric acid or oxalic acid possesses
certain inherent disadvantages. For example, oxalic acid
anodizing requires the use of a post anodizing treatment
to obtain adequate adhesion of the plated metal. Both
phosphoric acid and oxalic acid anodizing are particularly
sensitive to variations in aluminum alloy composition,
and with many aluminum alloy products, it is difficult
if not impossible to adherently plate metal particularly
electrodeposit a layer of nickel on the oxide-coated sur
face of the aluminum metal in a conventional nickel-plat
ing bath. For some applications it has been found desir
able to electrodeposit a plurality of layers of nickel on
the oxide-coated surface of the aluminum metal, for ex
ample, two or three layers of nickel. Thereafter, a layer
of chromium is electrodeposited on the nickel in a con
ventional chromium-plating bath. Where an article to
be plated with chromium is not to be subjected to un
45
nickel and chromium, on an anodized surface produced
usually severe corrosive environments or to unusually
in phosphoric acid alone or oxalic acid alone.
severe bending and impact stresses, the layer of chromi
Additionally in the prior art it has not been possible
um may be electrodeposited directly on the oxide-coated
to produce many plated articles from aluminum or alu
surface of the aluminum metal without electrodepositing
minum alloys wherein the articles are characterized by
50
an intermediate layer of nickel.
multiple curved portions and accordingly require a de
A series of aluminum alloys has been developed which
sirable combination of formability coupled with good
strength such as in automobile bumpers and wheel covers.
Thus, while aluminum may have many advantages for
exhibit the combination of good formability and strength
necessary for applications such as automobile bumpers
such applications due to lightness in weight, corrosion 55 and wheel covers. These alloys are designated by the
letters A thru E in Table I below wherein the, percent
resistance, etc., in the past, such articles have not been
produced from aluminum. Accordingly, special alloys
have been developed for such applications. However,
satisfactorily adherent plates of nickel and chromium
could not be produced on these alloys over anodized coat
ages by weight of elements other than aluminum con
tained therein are given. In addition, a small but effec
tive amount of titanium is added for grain re?nement.
' Such alloy compositions generally fall within the range
60 of not more than 0.25% silicon, not more than 0.25 %
ings produced in phosphoric acid alone or oxalic acid
iron, 1.30 to 3.70% copper, not more than 0.25% man
alone.
According to this invention, aluminum is anodized in
an aqueous electrolyte consisting essentially of phosphoric
ganese,’ 0.20 to 1.20% magnesium, not more than 0.30%
zinc, a small but effective amount of titanium su?icient for
3,098,804
4
grain re?nement, and not more than 0.05% each, 0.15%
total of other elements, balance aluminum.
area of 6 sq. inches per sample were fabricated from a
sheet of each of the commercial aluminum alloys desig
Table I
Silicon
Iron
Copper Man-
Mag-
Others
Zinc
ganese nesium
E h I T t 1
‘a0
3.35
3.02
2.15
3.80
2.55
.8
v50
______ __
0.10
0.10
0.10
0.10
______ __
______ __
1.
s
______ __
1.
5
______ __
1. 05
0.10
0.85
______ -_
(1.55
(1)15
0.20
oés
.
0.10
010
0.10
0.10
5
0'05
0'05
0'05
0'05
0'15
0'15
0'15
0'15
0.10 l 0'05
Q15
______ _
.40
______ ._
0.
5
______ -_
0.
5
______ __
0.45
l
i
i
i
Table II below gives typical results of strength and
elongation tests performed on these alloys after treatment
according to the conventional temper designations in
dicated in Table II below. The samples on which these
nated by the aluminum association as 1100, 2024 and
6061. The percentages of elements other than aluminum
in these alloys are indicated in Table III below. The
?gures in Table III indicate maximums unless a range is
shown.
Table III
tests were performed were 0.090‘ inch thick standard
Silicon
0 a
Iron
Copper
Manganese Magne- Chromium
Zine
sium
Tita
Others
niurn
Each
1100-.
2024_-
6061"
1.0 Si-t-Fe
0.50
0.40—0.8
0.20
0.50
3.8-4.9
0.7
0.15-0.40
A.S.T.M. sheet samples for alloys A, B, and C and 0.032
inch thick standard A.S.T.M. sheet samples for alloys D
and E. Variations in alloy composition within the above
limits may produce variations from the typical properties
indicated in Table II below.
Table II
0.05
0.3-0.9
0. '
____________________ __
1.2-1.8
0.10
0.8-1.2
015-035
0.10
______ __
0.05
Total
0.15
0.25 ______ __
0.05
0.15
0.25
0.05
0.15
0.15
In these tests, all the samples were given the following
treatment, it being understood that the conventional cold
water rinsing operations after the various steps are not
recited:
(1) Cleaned for 5 minutes in a mild inhibited alkaline
cleaner of the carbonate-phosphate-silicate type contained
40 in a 30-gallon rectangular stainless steel tank at a tem
Tensile
Yield
strength,
strength,
55, 000-58, 000
49, 500-52, 200
50, 500-52, 000
43, 500-47, 200
44, 400-45, 500
35, 800-37, 000
34, 800-39, 700
30, 600-33, 700
30, 900-33, 900
36, 000-40, 000
28, 100-31, 900
32, 000-33, 600
24, 000-27, 400
27, 700-28, 500
16, 900-19, 000
23, 000-23, 600
13, 400-16, 800
13, 600-16, 500
p.s.1.
p.s.1.
Elong ,
percent
in
perature of 160° F. to a water break-free surface.
(2) Etched by immersion for 5 minutes in a mild aque
ous etching solution containing 25% by Weight sulfuric
acid, balance water contained in a 4-liter Pyrex beaker,
20-24
24-29 45 at a temperature of 180° F.
23-37
(3) Anodized in a 20-liter Pyrex rectangular tank
22-26
equipped with stirring devices and lead cathodes for 2
22-25
17-24
minutes with direct current in an aqueous phosphoric
23-36
acid-sulfuric acid electrolyte, containing 300 mls./liter of
19-24
19-25
aqueous 85% by weight H3PO-4 solution and 30 mls./liter
The temper designations of Table II are the standard
of aqueous 96% by weight H2804, solution, the balance
of the electrolyte being distilled water. The temperature
designations recommended by the aluminum association.
was maintained at 100° F. with a thermostated electric
The heat treatment employed on the above alloys may
immersion heater. The current densities were maintained
comprise heating the metal to a temperature of at least 55 at 36 a.s.f. In general, the voltages necessary to main
about 850° F. and maintaining the metal at that tempera~
tain a given current density vary with the alloy, the cell
ture for a period of time which may be as short as about
10 minutes. The metal is then quenched in a suitable
means such as water. Following quenching, the metal
geometry and the anodizing conditions and the required
voltage varies as the anodizing progresses. In anodizing
the samples employed in these tests the voltages required
with the temper designation of T3 is cold worked. The 60 to maintain a constant current density of 36 a.s.f. ranged
above alloys may be formed into products such as auto
from about 2 to 30 volts.
mobile bumpers or Wheel covers. However, such arti
(4) Electroplated as a cathode with chromium in a 20
cles cannot be adherently plated with metals such as
liter Pyrex rectangular tank equipped with stirring devices
nickel and/or chromium when anodized in conventional
and lead anodes for 30 minutes with a direct current in an
anodizing baths. When anodized in a phosphoric acid 65 aqueous electrolyte containing 250 grams per liter of
‘sulfuric acid electrolyte they may be plated with nickel
CrO3, 2.5 grams per liter ‘of H2504, balance distilled Water.
and/or chromium whereby an attractive plate character
The temperature was maintained at 601° F. ‘by use of a
ized by excellent adherence may be produced. In plat
cold water jacket surrounding the 20-liter Pyrex tank.
ing articles such as automobile bumpers or Wheel covers
The current ‘densities were maintained at 200 |a.s.f. The
of the above alloys, best results have been achieved by 70 voltages required to maintain a constant current density
anodizing in a sulfuric acid-phosphoric acid anodizing
of 200 a.s.'f. ranged from- 6 to 8 volts.
bath, plating three layers of nickel on the anodized metal
(5) The samples were rinsed brie?y in distilled water,
followed by plating with chromium.
‘dried and tbuffed to a decorative brightness.
In an illustrative example of the process of this inven
All samples had a lustrous, attractive chromium plate
tion, 1” by 3" rectangular samples having a total surface
characterized by excellent ‘adherence as shown ‘by absence
3,0 assoc
(3) All samples were electroplated as a cathode with
of ?aking o? of the chromium when the samples were
nickel in a 20Jliter Pyrex rectangular tank equipped with
a cathode rod agitating device and nickel anodes for 60
bent over a 3%” diameter mandrel.
In another example of the practice of this invention, 1”
minutes with a direct current in an aqueous. electrolyte
by 3" rectangular samples having a total surface area of
_ . per sample
,
_
6 _ square‘ inches
were fabricated
from sheets
5
having a pH of between 3 and 4, containing 12 ounces per
of_the commercial alu-rmnum alloys designated by the Alu-
gallon of N504. 7H20, 27 ounces per gallon’ Niclz. 61120,
r as 1100,
.
mlnum Association
2011,. 2024, 3003, 6061, 6063,
5 ounces per gallon of H3803, and 1/z % by volume of a
7075, and the alloy designated in Table I above by the
.
n
_
wetting
agent, balance
water. The temperature
of the
vletter “C3, The percentages of elements other than 81m
minum in the above commercial alloys are indicated in
‘electrolyte was mamtamed at 135° F- ‘by means of an
Table IV below The ?gupgs in Table IV indicate maxi- 10 electric immersion heater. The current densities were
mums unless a range is shown.
maintained at 40 aslf. and the voltages required to main
Table IV
Others
Alloy
Silicon
1100..
2011..
Iron
1.0 Si-l-Fe
0.4
0.7
2024-.
0.5
0.5
3003-.
0.6
0.7
0051.. 0. 40-08
5003-. 0. 20-00
7075.- 0.5 -0.7
0.7
0. 35
0.7
Copper
0.20
5. 0-50
Manganese Magne- Chromium
Zinc
sium
Tita
nium
Each
0.05 ____________________ __
________________________________ ._
3.8-4.9
0.30 .9
0.20
1.0 -1.5
0.15-0.4
0.10
1.2-2.0
0.15
0.10
0.30
1 2-1.8
0.05
0.05
0.10
____________________ __
0.8 -1.2
0.45-0.19
2 1 -2.9
0.15-0.35
0.10
0.18-0.40
5.
Total
0.15
0.15
0.05
0.15
0.05
0.15
0.05
0.05
0.05
0.15
0.15
0.15
1n these tests the samples ‘were given the following treat- 25 tain a constant current density of 40 a.s.f. ranged from
ment, it being understood that the conventional cold water
2 to 4 volts.
rinsing operations after the various steps are not recited:
(4) Samples 2, 7, 8, l3 ‘and 14 were additionally elec
(1) Cleaned for 5 minutes in a mild inhibited alkaline
troplated as a cathode with chromium in a 20-liter Pyrex
cleaner [of the carbonate-phosphate-silicate type contained
rectangular tank equipped with mechanical stirring and
in a SO-gallon rectangular stainless steel tank at a tempera- 30 lead anodes for 5 minutes with a direct current in an aque
t-ure of 160° F. to a water break-free surface.
ous electrolyte containing 33 ounces per gallon of 0x03,
(2) Anodized in a 20-liter Pyrex rectangular tank
equipped with an air agitation device and lead cathodes
0.33 ounce per gallon oil-12504, balance water. The tem
per-attire of the electrolyte was maintainedat 100° F. by
with direct current in an aqueous electrolyte containing
means of an electric immersion heater. The current den
phosphoric acid and sulfuric acid or phosphoric acid alone 35 sities were maintained at 200 a.s.f. and the voltages re
or sulfuric acid alone in the amounts indicated in Table V
quired to maintain such cur-rent densities ranged from- 5
below. These amounts are in terms of the percentages
to 8 volts. The remaining samples were not plated with
of aqueous 85% by weight H3PO4 solution and aqueous
chromium.
.
96% by weight H2804 solution in the electrolyte, the bal(5) The samples were rinse briefly in distilled water,
ance' of the electrolyte being water. The anodizing time, 40 dried and bul’ied to a decorative brightness. Chromium
electrolyte temperature, current densities and the voltages
required to maintain such current densities are vgiven in
TableVbelow:
Table V
plating of exceptional adherence was produced on samples
2, 7, 8, 13 and 14. A nickel plating of exceptional ad
herence was produced on samples 1, 3-6, 9—12 and 15 to
25. No peeling whatsoever was observed on any of the
45 samples 1 through 25 even after severe grinding or bend
ing. All of the samples on which these adherent plat
Anodizing conditions
Sqm 10
(Noxf
Tam
Alloy
Current
AnoOF?" density, vo1t_
dlmg Percent Percent
a-S-f-
ings were produced, i.e., samples 1—25, were anodized
in a phosphoric acid-sulfuric acid electrolyte embodying
mm,
the prmciples
of this
invention
as can be seen from Table
.
.
., .
.
time,
I'I3PO4
H2504
gs
32
lg
phoric ‘acid alone or sulfuric acid alone. Samples 26
48
15
and 28 could not be plated at ‘all while with the remainder
i‘;
of samples 26-36 the platings exhibited very poor ad
1
00_F___-__
5
15
a
%
38535::-
lg
lg
3'3
4
_ 2011—T4__:
5
15
g:
_ ggggi:
2
1(5)
7__
_ 20214-3.-.
10
i8
10
i2
8.3
3-3
130
1,3,8
as
5
2
1Q
3
Z
138
130
fig
48
15
18
18
2%
$8
5
5
19'
mo
40
13 60 num alloys in the T4 temper of the type designated by
g
13
1g
13%
‘73(2)
l3
5
10
10
90
4s
21
of elements other than aluminum are indicated in Table
5
10
10
130
48
13
V1 below
10
g"-
SOOH'IM"
130
50 V. Adherent platings could not be produced on the re
15
maining samples which were anodized either in phos
15
90
1,1,8
15 55 hesiom
In another example of the practice of this invention,
a substantial number of automobile bumpers character
ized by multiple transverse and longitudinal curved por
-tions were fabricated from solution heat treated alumi
the letters B, C and D in Table I above. The percentages
55
10
15
15
15
130
so
81
48
2
15
15
130
90
4
54
s4O s15
1 10
a
a72
55
5
5
5
5
00
0
0
15
15
15
15
25
25
0
0
00
130
90
130
90
110
00
48
96
48
21
72
Z5,
{-1
5
25
0
110
84
1?
aluminum alloys having thicknesses ranging from about
g
g;
g
11?,
it
%g
0.090 to 0.125 inch. These sheets were fabricated into
2
g
138
'
Table VI
81
,
To
011
.05
.13
2.01
.13
.11
.15
.18
2. 00
2.14
Mn
______ __
.01
.05
Mg
.95
.48
.37
Zn
______ -_
.02
.03
T1.
.01
.01
.02
These bumpers were fabricated from sheets of the above
75 bumpers in the conventional manner generally employed
'37
3,098,804.
in the fabrication of steel bumpers, i.e. the sheets were
pickled in a conventional pickling bath, dried, blanked
(i.e., cut to the desired shape for forming), polished with
quired to maintain a constant current density of 80 a.s.f.
ranged from 10-15 volts.
(7) Electroplated as a cathode with chromium in a
abrasive belts, subjected to a conventional treatment to,
2500 gallon lead lined steel rectangular tank equipped
make them more suitable for retaining a lubricant, rinsed, 5 with air agitation and lead anodes for 4 minutes with
dried, the lubricant applied and the bumper then formed
direct current in an aqueous electrolyte containing 250
by stamping in a conventional press. After stamping,
g./l. of CrO3, 2.5 g./l. of H2804, balance water. The
the bumper was subjected to one or more trimming op
temperature of the electrolyte was maintained at 105° F.
by means of lead steam oo-ils. The current density was
erations to remove excess metal.
These bumpers were subjected to the following treat 10 maintained at 125 a.s.f. and the voltages required to
ment, it being understood that the conventional water
maintain a constant current density of 125 a.s.f. ranged
rinsing operations after the various steps are not recited:
from 5—8 volts.
(1) Buifed to a decorative brightness.
(8) Rinsed in cold water followed by a hot water
(2) Cleaned for 5 minutes by soaking inea solution
rinse, and dried in air.
containing 60 g./l. of sodium tetraborate
15
A lustrous chromium plating of exceptional adherence
was produced. No peeling whatsoever was observed even
after severe grinding or bending.
As used herein, the term “aluminum” is meant to
(Na2B4O7- 101-120)
plus a small quantity of wetting agent, balance water con
tained in a 2500 gallon rectangular steel tank at a tem
.. perature of 170°,F.
cover high‘gpurity aluminum, commercial purity alumi
20 num and aluminum alloys.
(3) Anodized in a 2500 gallon vinyl plastic-lined steel
rectangular ‘tank equipped with air agitation and lead
It will be understood that various changes, omissions
and additions may be made to the invention without de
,cathodes for 5 minutes with ‘direct current in an aqueous
parting from the spirit and scope thereof as set forth
phosphoric acid-sul?uric acid electrolyte containing 15%
in the appended claim-s.
by volume of aqueous 85% by weight H3PO4, solution 25 What is claimed is:
and 15 % by volume of aqueous 96% by weight H2504
1. A method of producing a ?rmly adherent coating
solution, the balance of the electrolyte being water. The
of a metal selected from the group consisting of nickel
temperature was maintained at 100° -F. with lead steam
and chromium
coils. The current density was maintained at 40 a.s.f.
on an article of an aluminum alloy containing by weight
The voltages required to maintain a constant current 30
not more than 0.25% silicon, not more than 0.25%
density of 40 a.s.f. ranged from about 2 to 13 volts.
iron, 1.30 to 3.70% copper, not more than 0.25%
(4) Electroplated as a cathode with nickel in a 2500
manganese, 0.20 to 1.20% magnesium, not more than
gallon vinyl plastic-lined steel rectangular tank equipped
0.30% zinc, a small but effective amount of titanium
wit-h continuous ?ltration and external heat exchange and
nickel anodes for 5 minutes with a direct current in an
35
aqueous electrolyte having a pH of 3.7, containing 300
g./l. of NiSO4-6H2'O, 45 g./l. of NiCl2-6H2O, 40 g./l. of
suf?cient for grain re?nement, impurities in normal
amounts, balance substantially aluminum,
said method comprising the steps of
immersing said aluminum alloy as an anode in an
aqueous electrolyte consisting essentially of
H3BO3, .5 g/l. of a wetting agent, balance water. The
temperature of the electrolyte was maintained at 130° F.
phosphoric acid and sulfuric acid, balance water,
passing an electric current through said electrolyte
by means of an external heat exchanger. The current
density was maintained at 40 a.s.f. and the voltages re~
quired to maintain a constant current density of 40 a.s.f.
ranged from 4 to 7 volts.
(5 ) Transferred to a second nickel plating bath and 45
electroplated as a cathode with nickel in a 10,000 gallon
for a time period of from 1 to 30 minutes, at cur
rent density of from 12 to 120 amperes per
square foot and a voltage of less than 40 volts,
thereby producing an oxide coating on the surface
of said article
thereafter electrodepositing a layer of metal se
vinyl plastic-lined steel rectangular tank equipped with
lected from the group consisting of nickel and
air agitation and nickel anodes ‘for 16 minutes with a
chromium directly on said oxide-coated surface.
direct current in an aqueous electrolyte having a pH of
2. The method of claim 1 wherein said electrolyte con
3.7 containing 300 g./l. of NiSO'4-6H2O, 45 g./l. of 50
tains from 5 to 45% phosphoric acid and from 1 to 30%
NiCl2-6H2O, 40 g./l. of H3BO3, .5 g./l. of wetting agent,
sulfuric acid, balance water and wherein said electrolyte
.25 g./l. of coumarin (1,2-benzopyrone), .25 g./l. of
is maintained at a temperature ranging from 80 to 140° F.
formaldehyde (HCHO), balance water. The tempera
3. The method of claim 1 wherein at least one layer of
ture of the electrolyte was maintained at 130° F. by
means of a heat exchanger. The current density was 55 nickel is electrodeposited on said oxide-coated surface
and thereafter a layer of chromium is electrodeposited on
maintained at 60 a.s.f. and the voltage required to main
said nickel.
tain a constant current density of 60 a.s.f. ranged from
10 to 15 volts.
4. An adherently plated aluminum automobile bumper
characterized by multiple curved portions, a tensile
(6) Transferred directly without rinsing to‘ a third
nickel plating bath and electroplated as a cathode with 60 strength of from about 30,000 to 58,000 p.s.i., a yield
strength of from about 13,000 to 40,000 p.s.i. and a per
nickel in a 10,000 gallon vinyl plastic-lined steel rec
centage elongation in two inches of from about 17 to 29
tangular tank equipped with air agitation and nickel
produced by the method of claim 3.
anodes for 8 minutes with a direct current in an aqueous
5. The composite article produced by the method of
electrolyte having a pH of 3.7 containing 300 g./l. of
NiSO4~6H2O, 45 -g./l. of NiCl2-6H2O, 45 g./l. of H3BO3, 65 claim 1.
.5 g./l. of wetting agent, .1 g./l. of coumarin (1,2-benzo
pyrone), 1 g./l. of saccharin (O-sulfobenz-oic imide) and
.005 g./l. of tris (aminophenyl) methanol, balance Water.
The temperature of the electrolyte was maintained at
130° F. by means of a heat exchanger. The current
density was maintained at 80 a.s.f. and the voltages re 7°
References Cited in the ?le of this patent
UNITED STATES PATENTS
1,971,761
2,473,163
2,637,686
2,703,781
Travers ______________ __ Aug. 28,
McCoy _____________ __ June 14,
McKay _______________ __ May 5,
Hesch ________________ __ Mar. 8,
1934
1949
1953
1955
UNITED STATES PATENT OFFICE
CERTIFICATE OF CORRECTION
Patent No. $098,804
July 23v 1963
Henry J. Wittrock
o've numbered pat
uld read as
d that the said Letters Patent sho
fied that error appears in the ab
It is hereby certi
ent requiring correction an
corrected below.
lumn entitled "Elong. ,
Column 3, Table II, in the 00
percent in 2" third entry thereof, for “23~37“ read
—— 23-27 ——;
same table ,
same column, seventh entry thereof ,
for "23-36" read -— 23-26 —-—.
Signed and sealed this 9th day of June 1964.
(SEAL)
Attest:
ERNEST W. SWIDER
Attesting Officer
,
EDWARD J . BRENNER
Commissioner of Patents
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