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Патент USA US2405101

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Patented July 30, 1946
Robert S. Truesdell, Los Angeles, Calif., assignor
of thirty-?ve one-hundredths to Fred Everett
Howell, Long Beach, and twenty-‘?ve one-hun
dredths to Frank Walker Harrington, Los An
geles, Calif.
No Drawing. Application January 1, 1944,
Serial No. 516,741
4 Claims.
(01. ‘IS-24)
This invention relates to a method of treating
steel ?les to accomplish sharpening and recon
set forth in order to enable-persons skilled in
the art to carry it into effect with a high degree
of efficiency, but it. will be apparent that ‘the
method can be modi?ed within limits without de
ditioning thereof.
The invention contemplates and has as its pri
mary object the provision of a method of recon
parting from the spirit of the invention.
ditioning and sharpening steel ?les such as to be
In carrying out my invention the following con
secutive steps are employed:
applicable to the treatment of ?les either before
or after being used to effect sharpening thereof
First step
and which is particularly adapted to recondition
preferably in a batch,
ing ?les after their having become oxidized, or
are ?rst immersed in an alkali bath capable of
worn, or rendered ine?ective by clogging of the
dissolving grease, oils and fats and also capable
toothed surfaces thereof.
of acting as a solvent for particles of aluminum,
Another object is to provide a method of chemi
and. which bath preferably consists of a 25 to 35%
cally treating steel ?les whereby various sub
stances accumulated on the toothed surfaces of
the ?le and which interfere with its proper use
may be removed ‘and the teeth of the ?le slightly
etched so as to sharpen the ?le.
Another object is to provide a method of the
above character which is extremely rapid in its
action and is adapted to the treatment of ?les in
batches to the end of enabling the attainment of
a large voutput; in a short time and whereby the
reconditioning of ?les may be so economically
effected as to render practical the commercial
rejuvenation of ?les on a large scale.
Another object is to provide a process for chem
caustic soda solution. The ?les are boiled in this
solution for suchlength of time as to effect re
moval of all particles of aluminum which may
have ‘accumulated on the ?les and at the same
time remove at least a-portion of such grease, oil
and fat as may-have been deposited thereon.
Thirty minutes of such hot alkaline bath is ordi
narily'su?icient to accomplish this Cleansing ac
tion.v .FAfter completion of the bath, the ?les are
removed from the solution and .while hot are
rinsed with a spray of cold water applied at nor
maltemperature and. at the pressures of domestic
water supply systems, usually about 85 pounds,
for a period of ?ve minutes or thereabouts to ef
fect sudden cooling of the ?les and their conse
as not to be detrimental to the ?les under treat
ment and which consequently results in little or 30 quent contraction from their expanded condi
tion occasioned by the action of heat in the boil
no loss of ?les because of damage thereto While
ically reconditioning and etching steel ?les such
A further object is to provide a ?le recondition
ing and sharpening process embodying a step
whereby the processed ?les will be rendered free
of subsequent detrimental action of chemicals
employed in the process.
Other objects and advantages will appear here
lng operation. This rinsing and cooling opera
tion may also be effected by immersing the ?les
in cold Water. The expansion and contraction of
the ?les serves to effect loosening of some ma
terial embedded in the crevices of the ?les due
to differential in expansion and contraction of
di?erent substances.
This rinsing operation also serves to wash the
The method constituting the subject hereof in 40 ?les to remove loose particles therefrom and at
the same time effect cleansing the ?les of at least
volves the employment of alkaline baths and acid
the major portion of the alkali solution as may
baths which generally considered have been used
cling thereon.
heretofore in the cleansing of metallic surfaces
Second step
particularly in removing oxides and in pickling
operations, and also involves the employment of ,2. 15K
The washed ?les are submerged in an acid bath
sulphuric acid and nitric acid which have long
capable of dissolving and removing any grease,
been used in chemically conditioning ?les. My
invention while embracing these old features is
characterized by the employment of certain spe
oil, fat, tar, pitch and similar substances which
may be present thereon after completion of the
alkali and washing treatment, and also capable
ci?c consecutive steps embodying the employment 50 of removing iron oxide or rust accumulated on
of alkaline and acid baths of particular natures
the ?le and at the ‘same time dissolve ?ne par
and in a particular fashion, together with inter
ticles of iron or steel and silver which may be
mediate washing operations which I have found
deposited in the crevices of the ?le. This acid
to be essential to proper conditioning of ?les and
bath preferably comprises a mild solution of sul
which results in a product possessing a high 55 phuric acid. A ?ve to ten per cent solution is
standard of quality not subject to deterioration
as the result of the acid treatment.
In setting forth my method herein the several
time, temperature and strength of solution fac
tors, together with speci?c substances used will be
The ?les are immersed in this acid bath for a
period of ?fteen minutes or thereabouts during
which time the solution is maintained at a tem
perature of 160° F. or approximate thereto. How
ever, care must be?exercised to avoid the bath
reaching a temperature in excess of 180° F. for
the reason that a temperature higher than this is
liable to detrimentally affect the points of the ?le
This acid bath will serve to remove the sub
stances above speci?ed as well as others subject
to being dissolved by the action of sulphuric acid
of the strength and in the time stated, and will
also act on removal of such substance to mildly -a
attack the toothed surface of the ?le so as to
‘effect a slight sharpening action on the ridges or
teeth of the ?le. As a substitute for commercial
sulphuric acid I have found that the product
known as “Sani?ush” is‘ highly satisfactory when
used in the range'of proportions speci?ed for
sulphuric acid. This product comprises a mix
ture of sodium bisulphate, sodium chloride and
magnesium silicate.
The ?les are removed from this acid bath when
suf?ciently cleansed and are rinsed in a water
bath or spray for about ‘?ve minutes to effect
valve, to eifect control of the temperature of the.
nitric acid solution and whereby the tempera
ture of the solution may not only be maintained
at not more than 180° F. but may be varied from
time to time to meet varying conditions. The
lower the temperature of the nitric acid solution
the slower will be its action and conversely the
higher its temperature the more rapid its action.
There are occasions when a slow action is desir
able and times when a faster action is wanted
and accordingly regulation of the temperature of
the solution becomes quite important in commer
cial reconditioning of ?les.
There are limitations as to the length of time
the ?les may be treated in this bath without dam
age which period varies, however, as to the condi
tion of the ?les under treatment and also the tem
perature and strength of the nitric acid solution.
The lower the temperature of the solution and
the weaker the solution the greater the period of
time during which the ?les may be immersed
in the solution. I have found in practice that
a period of ?fteen minutes of submersion of the
?les in the nitric acid solution of the strength
above stated and at a temperature of about 160
degrees is ordinarily suf?cient to accomplish re
moval of copper and its alloys from the ?les, but
removal of loose particles from the ?les and also
remove the sulphuric acid clinging thereto.
Some ?les may be adequately cleaned and re
conditioned after the completion of this second
step, particularly ?les ‘that have become fouled
where babbitt or lead are to be decomposed a
by oxidization, those that have been used solely
longer period may be required. However, what
in ?ling aluminum, silver and steel, and such ?les
that are coated with pigments and oily, greasy, 30 ever period is necessary to effect the requisite ac
tion, such peripd is preferably, though not neces
or resinous materials, or other materials that are
sarily consumed in a series of immersions of short
readily soluble in either caustic soda or weak
duration, for example, of three minutes each.
solution of- sulphuric acid. Any ?les that may
By so doing the extent of the action of the nitric
be deemed inadequately reconditioned at the com
acid may be watched from time to time so as to
pletion of this second step may be treated as set
minimize possibility of excessive corrosive action
forth in the last step to be later described. How
on the ?les.
ever, the'essence of the present invention resides
When by examination it is determined that the
in subjecting ?les to the hereinafter recited steps
nitric acid treatment has accomplished the de
in continuation‘of the speci?ed ?rst and second
steps, since the‘ greater majority of ?les requir- _ sired result of removing the softer metals and
slightly etching the teeth of the ?les, the latter
ing reconditioning have dulled teeth which will
not be adequately sharpened by the named alkali
are again subjected to a thorough washing ac
and acid‘ treatments, and besides have been used
in ?ling soft metals such as copper, brass, bronze,
lead, zinc and other metals or alloys which will
not be affected by the alkali and acid speci?ed.
tion by immersing and agitating in water to re-_
Third step
spraying operation ordinarily is not adequate
move the nitric acid solution and any other sub
stances as may be subject to removal by such
washing. Water spraying of the ?les after treat
ment with nitric acid may be employed but such
when applied to a batch of ?les since impact of
The ?les cleansed as above described are then
immersed in an acid bath capable of digesting 50 the spray on some of the ?les will act to knock
the soft metals and their alloys including copper,
brass, bronze, babbit, lead and zinc, and also
capable of effecting an etching or sharpening
action on the teeth of the ?le. This acid bath
preferably comprises a 7 to 10 percent solution
of nitric acid.
In subjecting the ?les to the action of the nitric
acid bath it is essential that the temperature of
the solution be maintained su?iciently low as not
acid therefrom onto other of the ?les therefore
rendering it possible for retention of nitric acid
on at least some of the ?les with consequent
damage thereto. Even if a spraying operation
be used it is necessary to follow it with immer
sion and agitation in a water bath in order to
insure thorough removal of the nitric acid.
Fourth step
The ?les are then immersed in a ?fty per cent
to blister or mutilate the ?les. I have determined 60
that temperatures in excess of 180° F. are liable ‘ solution of sulphuric acid and allowed to remain
to damage the ?les and accordingly it is neces
sary, in order to insure a high standard of quality
therein a period of from thirty to forty minutes
whereby such metals or other materials as may
have escaped the earlier sulphuric acid treatment
and which are subject to decomposition or dis
solution under the action of such solution will be
in the reconditioned product, to treat the ?les in
the nitric acid solution at a temperature ranging
downward from 180° F. Since considerable heat
removed. The temperature of this solution
is generated by the action of the nitric acid solu
should not exceed 180° F.
tion in digesting metallic particles on the ?le,
especially when'the solution is fresh, the temper
Fifth step
ature of the solution is regulated by subjecting 70
of this second sulphuric acid
the solution to the action of a cooling medium
treatment the ?les will be thoroughly cleansed
such as a refrigerant flowed through tubes sub
and will be well sharpened but ordinarily ?les
merged in the solution. The ?ow of the refrig
erant is controlled in a conventional fashion as
that were considerably worn will be improved by
by an automatic thermostatic controlled feed 75 a further sharpening action. To accomplish this
the ?les are immersed in boiling water. This hot
water treatment constitutes an important step in
the process since on immersion of the acid coated
?les in boiling water an instant accelerated action
of the acid takes place which is particularly mani
fested 0n the tips of the ?le teeth in increased
sharpening thereof.
This action is limited to
The process herein set forth is especially ap
plicable to the treatment of ?les on a large scale,
it being subject to being carried out by the em
ployment of a series of cauldrons containing the
several liquids which are arranged in the consec
utive order of their use. Batches of ?les sup
ported vertically in spaced relation to each other
such short duration as to insure against excessive
on a portable rack are conveyed to and from the
etching of the points of the teeth by reason of
the acid being quickly weakened by the hot water. 10 several cauldrons and are lowered into and with
drawn from the baths by suitable hoisting mech
The ?les are maintained in this hot bath for
the ‘ ?les being previously classi?ed or
a su?icient length of time to dilute the acid cling
graded in each batch according to similar char—
ing to the ?les to at least near neutral. A period
acteristics so that the ?les in batches needing
of ?ve minutes or thereabouts is ordinarily ade
quate. The ?les will be thoroughly cleansed and 15 di?erent times of treatment may be variably
treated according to requirements and so that all
sharpened at this stage of their treatment.
the ?les of each batch will be uniformly treated.
Sixth step
However, it may be that at the end of any step in
the process some ?les in a batch may not be ade
Immediately or shortly after removing the ?les
quately processed in which event such ?les may
from the hot water bath they are subjected to
be removed from the batch at any stage in the
the action of a neutralizing agent, as by being
process and be retreated with any of the steps to
submerged in a boiling alkaline bath such as to
insure its proper reconditioning.
insure any acid clinging to the ?les being ren
I claim:
dered neutral. This bath preferably consists of
1. The method of reconditioning ?les consist
a ?ve to ten per cent Baumé solution of sodium 25
ing in ?rst subjecting the ?les to the action of a
carbonate or a solution comprising one pound or
solvent of aluminum, grease, oils, fats, pigments
thereabouts of pulverized sodium carbonate dis~
and the like, washing the ?les, then immersing
solved in ?fty gallons of water, together with a
the ?les in a weak solution of sulphuric acid,
one per cent solution of bichromate of soda. The
?les are submerged in this neutralizing solution 30 washing the ?les, subjecting the ?les to the ac
tion of a nitric acid solution, washing the ?les,
for such length of time as to obtain the desired
again immersing the ?les in a sulphuric acid so
result. Boiling the ?les in this solution for ten
minutes is ordinarily sufficient.
lution stronger than that previously employed;
immersing the ?les in boiling water whereby an
The ?les on being thus subjected to the hot
neutralizing agentare removed therefrom and 35 instant acceleration of the action of acid clinging
to the ?les will occur and effect a sharpening of
while hot are suddenly cooled by submergence in
?le teeth, immersing the ?les in a neutraliz
cold Water in which the ?les are thoroughly
ing bath, washing the ?les, and ?nally coating the
washed. About ?ve minutes will suf?ce for this
?les with a rust protective material.
2. In a process of sharpening steel ?les involv
Seventh step
40 ing subjecting the ?les to the action of nitric acid
While the ?les are in condition for re-use on
solution ‘to effect etching of the ?le teeth followed
being dried at the conclusion of the preceding
by water washing, the steps of immersing the ?les
step, they are subject to becoming oxidized on
in a sulphuric acid solution immediately followed
exposure to air and moisture and accordingly it
by immersion of the ?les in boiling water whereby
is vitally important in the reconditioning of the '
an instant acceleration of the action of acid
?les on a commercial scale that they be given a
clinging to the ?les will occur and effect further
and ?nal sharpening of the ?le teeth.
protective coating such as to obviate rust. For
this purpose the ?les on being ?nally washed in
3. In a process of sharpening steel ?les involv
cold water at the end of the preceding step are
ing subjecting the ?les to the action of nitric acid
immediately given a protective coating as by be
solution to e?ect etching of the ?le teeth followed
ing submerged in a solution of soap and water.
by water washing, the steps of immersing the ?les
This solution is preferably prepared from a soap
in a sulphuric acid solution immediately followed
having a vegetable base such as the soap known
by immersion of the ?les in boiling water whereby
as “Palm Olive.” Four hand bars of such soap
dissolved in ?fty gallons of water makes a satis
factory soap solution for the purpose. The ?les
are immersed in this soap solution long enough
an instant acceleration of the action of acid
clinging to the ?les will occur and effect further
and ?nal sharpening of the ?le teeth, then im
mersing the ?les in a neutralizing alkaline bath.
to insure thorough coating thereof. Merely dip
4. In a process of sharpening steel ?les, the
ping the ?les in the solution is ordinarily su?i
steps consisting in immersing the ?les in a seven
cient. On removing the ?les in the solution they 60 to ten per cent solution of nitric acid, for a period
are dried in atmosphere at room temperature
of ?fteen minutes, to sharpen the teeth of the
whereupon the ?les will be coated with a pro
tective ?lm of soap whereby the ?le surfaces
will be retained free from rust. The recondi
tioned product is then ready for use or for pack
?les, removing excess heat from the solution oc
casioned by reaction of the acid on the ?les by
means of a refrigerant to maintain the temper~
65 ature of the solution below 180° F. during immer
aging or storing.
sion of the ?les, then water washing the ?les, then
The total time required to perform all the steps
immersing the ?les in a solution of sulphuric acid
of this process to and including applying the ?nal
then immediately immersing the ?les in boiling
coating, assuming no appreciable delay occurs be
tween any of the operations, will be from two to 70 water to effect further sharpening of the teeth of
the ?les, and thereafter subjecting the ?les to an
two and one-halt‘ hours, thus greatly reducing the
acid neutralizing treatment.
time ordinarily consumed in the reconditioning of
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