Note: Descriptions are shown in the official language in which they were submitted.
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1 ~ACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
This invention relates to cleaning metal foil recording
tapes, and, more particularly, to an electrochemical cleaning
apparatus and method for cleaning oxidation and other contamination
from a metal foil recording tape.
PROBLEM AND THE PRIOR ART
For special recording applications, the recording tape
must be capable of withstanding sudden shocks and high temperatures
without breaking the tape or losing the recorded information. A
specific example of the conditions under which a tape is subjected
to extreme shock and heat is in the use of a tape in the flight
recorders on aircraftr which tape must be able to withstand the
shock of a crash and the tremendous heat that might follow the
crash should a fire result therefrom.
A metal foil magnetic recording tape, such as a tape
made of a vanadium-cobalt-iron alloy and sold under the trademark
"VICALLOY" by Arnold Engineering, has been found to satisfactorily
withstand the shock and heat requirements.
Metal foil recording tapes in the process of being
manufactured have been found to have not only an oxide coating on
the surface of the tapes, but also oil or other processing lubri-
cants and small metal burrs or grindings that have adhered to the ;
surface of the tapes. In the past, attempts have been made to
clean metal strips or sheets by anodic treatment in a solution of
hydrochloric acid followed by a second anodic treatment in a
solution either of phosphoric acid or phosphoric acid and hydro-
chloric acid. Other attempts to clean metal strips included
electrolytic action in alkali baths with spray treatments during
30 or after the electrolytic action. These and other electrolytic ;
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1 treatments of metal sheets or strips (1) were inapplicable to the
present problem of cleaning thin metal foil recording tapes, (2)
were too expensive or (3) were directed to the solution of a dif-
ferent problem not applicable to the present problem.
SUMMARY OF THE INVEWTION
An apparatus and method are provided for cleaning
oxidation, dirt, burrs and other contaminants from a metal foil
recording tape that overcomes the problems of the prior art and
results in a clean, uncontaminated metallic tape. The apparatus
and method comprise applying a positive charge to the metal tape
which charge, incidentally, heats up the tape. A stream of cooling
air or a spray of acid is directed onto the tape to cool and, in
the case of the acid spray, to precondition the tape. The tape
is drawn through a negatively charged acid solution for cleaning
the oxidation, burrs, dirt and other contaminants. The tape is
then rinsed and its surface is neutralized by passing the tape
through a water bath with ~et water sprays and a dewatering alcohol
bath. The tape is stripped of the solution in each bath as the
tape leaves each bath. A take-up reel received the cleaned and
decontaminated tape.
BRIEF DESCRIPTION OF THE DR~WINGS
:,
The details of construction and operation of the inven-
tion are more fully described with reference to the accompanying
drawings which form a part hereof and in which like reference
numerals refer to like parts throughout.
In the drawings:
Figure 1 is a front elevational view of the apparatus
of our invention showing the metal foil tape moving mechanism in
a position raised from the cleaning and rinsing baths;
Figure 2 is a schematic view of the operative parts of
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1 the cleaning apparatus of Figure l, and with said cleaning
mechanism shown in solid lines in operative position and in phan-
tom in the raised position above the baths;
Figure 3 is a perspective view of the alcohol dewatering
bath and associated parts;
Figure 4 is a front elevational view of the water rinse
bath with spray jets and associated parts shown-removed from-the
water bath;
Figure 5 is a perspective view of the mercury contact
-10 bath, cooling tube and acid bath electrode arrangement; and,
Figure 6 lS a front elevational view of a modification
of the cooling arrangement for the tape as it leaves the contact
bath.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The apparatus and method illustrated and described
herein are particularly suited for cleaning and decontaminating
the surfaces of a magnetic tape used in aircraft cockpit recorders.
Federal regulations require many aircraft parameters, and further
require that the recording medium withstand severe conditions such
20 as the high temperature of a fire, in the event of a crash. A ;
vanadium-cobalt-iron alloy sold under the trademark "VICALLOY"
by Arnold Engineering, has been found suitable. A typical foil
tape made of "VICALLOY" by Arnold Engineering, has a width of
.250 inch and a thickness of .0005 inch. The foil is commonly
rolled in a web several inches wide and several hundred feet 1n
length. The web is then slit into the .250 inch tapes. The
slitting operation leaves burrs along the edge of the tape which,
although generally microscopic in size, are sufficiently large to
lift the tape away from the surface of the magnetic heat and often
break off, contaminating the recording head and the tape-to-head
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1 interface. The quality of the recording is imp~~red resulting in
an inaccurate data record. In the applicants'U.S. Patent 3,986,301
entitled "Apparatus and Method for Lapping the Edges of a Metal
for Lapping the Edqes of a Metal Foil Tape," which issued
October 19, 1976, an apparatus and method is described and claimed
for deburring and otherwise smoothening the edges of the tape.
The tape, as received from the manufacturer, has a scale
coating of oxidation coating on the surfaces caused by the rolling
operation performed on the tape during manufacture. During the
deburring and edge smoothening operation, loose chips or burrs
can be attracted to the surface of the tape and adhere thereto.
The scale, the oxidation, the loose burrs or chips and the general - '
contaminants on the surfaces of the magnetic recording tape, are '
removed by our novel apparatus and method.
The apparatus for cleaning the surfaces of the magnetic
recording tape is illustrated generally in Figures 1 and 2 wherein
10 designates the cleaning apparatus which is carried by a base 11
having a vertically movable 'frame 12. A supply reel or play-out
reel 14 is mounted on the frame 12 and has a length of magnetic
recording tape 16 wound thereon. The frame 12 is vertically move-
able relative to the base 11 on the-pillars 13 such that the frame,
with its associated members, can be raised to remove said members ~ '
from the tanks on the base as will appear more clearly hereinafter.
The tape 1~ is directed from the reel 14 over a tape guide or
pulley 18, through a precleaning bath 20, through a mercury contact
bath 22, down a cooling tube 24, through an electrochemical or
electropolish acid bath 26, through a water bath 28, through a
dewatering bath 30, over a guide or pulley 32 and onto a take-up
reel 34. The tape 16 is received at the guide 18 either from the
play-out reel 14, as shown, or directly from an apparatus for
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1 deburring and buffing the tape edges which apparatus is described
and claimed in U.S. Patent 3,986,301 referred to hereinabove.
Likewise, after the tape has been cleaned and decontaminated, it
may pass to the take-up reel 34, as shown, or it may pass directly
through an oil fogging apparatus wherein a thin coating of lubri-
cant is applied to the tape. The fogging apparatus is described
and claimed in the applicants' U.S. Patent 4,018,303 entitled
"Oil Mist Lubricator for Metal Tape," which issued April 19, 1977.
Referring to the left-hand portion of Figures 1 and 2
and to Figure 5, the precleaning bath 20 is mounted on the frame
12 and is provided with three guides or pulleys 36, 37, 38 which
guide the tape 16 from guide 18 over pulley 36 into a tank 40
of Freon "TF*," or the equivalent, precleaning solution 42, around
guide 37, back out of the tank 40 and over guide or pulley 38. The
precleaning solution is intended to dissolve some of the contamin-
ants, such as certain oils, and to loosen other contaminants,
such as the scale formed in the sheet-forming operation.
The tape 16 from pulley 38 enters the mercury contact
bath 22 mounted on frame 12 which has a tank 44 containing mercury
46. The tape passes around guide or pulley 48 in the mercury and
up and around guide or pulley 50. The mercury is electrical~y
connected at 50 to the positive side of an electrochemical power
supply 52 carried by said base 11 and provides effective electrical
contact with the tape. Any commercially available electrochemical
or ~e~tropolish power supply 52 that is capable of delivering a
positive current of, for example, 40 volts D.C., 3 amps, is
acceptable. The electrically charged mercury 46 will apply a
positively charged current to the metallic foil tape 16 as said
tape passes through said mercury bath. Due to the relatively high
-electrical resistance to the metal foil tape, the tape will heat
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1 up as said tape leaves the bath.
The cooling tube 24 is aligned with the exit of the
pulley 50 and is attached to the mercury contact bath 22 on the
frame 12. The tube 24 is angularly disposed to guide the tape
into the tank 54 of the electrochemical or electropolish bath 26.
An air line 56 is connected to the tube 24 and supplies or forces
a stream of cooling air into the tube to cool the heated tape and
to prevent oxidation of the surface of said tape while it is
carrying the electrical current into the electrochemical or elec-
tropolishing bath.
The electrochemical or electropolishing acid bath 26comprises the large tank 54 mounted on the base 11 in which is
placed a phosphoric acid solution 60. One suitable solution is
a 75% solution which is readily available and commonly referred
to as "commercial grade." A plate 62 is mounted on the frame 12
and extends downwardly to support a pulley 64 about which the tape
16 passes. A pair of V-shaped, spaced apart electrodes 66 are
supported on said plate 62 such that tape 16 leaving the tube 24
passes between said electrodes 66 about the pulley 64 at the apex
-20 of the "V" and angles upwardly to the guide pulley 74 on the frame.
With the frame 12 in a lowered position the phosphoric acid solut-
ion 60 submerges the electrodes 66, the pulley 64 and the tape 16
as said tape passes between said electrodes. The negative side
of said electrochemical or electropolishing power supply 52 is
connected by lead 68 to the electrodes 66 to apply neagtive -
current to said electrodes. The negatively charged electrodes 66,
the phosphoric acid solution 60 and the positively charged tape 16
will combine to produce the electrochemical cleaning or electro-
polishing of the surface of the tape 16 to clean said surface of
scale, oxidation, burrs, or other contaminants. The electrochemical
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1 reaction o~ electropolishing principle are well-known in the art
and include concentration of current flow in sharp points of
material which results in erosion of points, thus providing
smoother surfaces.
As the tape 16 leaves the acid bath 26, it passes up
angled trough 70 through an air knife 72, both mounted on the
frame 12, and around the pulley 72. The air knife is a commer- -
cially available device constructed of a pair of air conduit tubes
as at 72a and 72b, each having a closed outer end and a longitud-
inal slit for directing air under pressure backwardly and toward
the tape. The air knife is adapted to blow air on the surface of
the tape (at room temperature, for example) to strip the phosphoric
acid solution from the tape so as to minimize dragout of the acid
solution. The solution stripped from the tape by the air knife
72 is discharged back into the tank 54 along the trough 7~.
The water rinse bath 28 on the base 11 is comprised of
a large tank 76 in which is held water 78. The water may be tap
water, distilled water or deionized water. A bracket 80 is carried
by the frame 12 and projects downwardly and, as is shown in Figure
4, has a pulley 82 at the lower end thereof about which the tape
16 passes as it advances from pulley 74 through the water solution
to the pulley 84 on said frame 12. A pair of spaced apart hig~
pressure water rinse jets 86, 87 are mounted on opposite ends of
piping 88 fastened to bracket 80. Each jet 86, 87 has a pair of
disc-shaped members 90 mounted side-by-side with a spacing there-
between sufficient to pass the tape 16 therethrough. Each member
90 has a nozzle 92 pointing at an angle to the stretch of tape
passing between said members. A cover 94 encases each pair of
disc members with openings provided therein for passage of the
tape and for drainage of the water from the jets. High pressure
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1 water is forced out the nozzles 92 in jets 86, 87 with the jets
pointing generally into the tank 76 when the frame 12 is lowered
and the bracket 80, with the tape passing over the pulley 82, is
submerged in the rinse water. In the case of jet 86, the water
from nozzles 92 will strike each side of the tape, not only at
points aligned with each other, but also at an angle to the tape
which will flush the surface in the direction of travel of the
tape tdownstream). The jet 87 will, likewise, have the water
strike the tape at an angle but in the direction opposed to the
direction of travel of the tape (upstream). The combined down-
stream-upstream water jet flushing of the tape effectively removes
loose scale, oxides, phosphoric acid, mercury particles or contami-
nants from the surface of the tape. The water 78 further flushes
contaminants from the tape as the tape passes therethrough. A
cover 93 is carried by the bracket 80 and has openings to permit
the tape to pass. When the frame 12 is lowered, the cover 93 will
cover the tank 76.
The tape passes from the jet 87 of trough 95 through an
air knife 96 and onto the pulley 84. The air knife 96 may be li~e
air knife 72, and strips water and loose particles from the tape.
The dewatering bath 30 has a tank 98 carried by the base
11. A dewatering solution 100, such as alcohol, is used in the
tank 98. The tape 16 passes from pulley 84 around a pulley 102
mounted on the lower portion of bracket 104 mounted on the frame 12.
With the frame 12 lowered, the lower portion of bracket 104 and
pulley 102 will be submerged in the alcohol solution. From the
pulley 102, the tape passes out of the dewatering solution 100 to
a pulley 106 and through a hot air knife 108 carried by the frame.
As the tape passes through the alcohol solution, the alcohol will
strip and absorb the water from the surface of the tape such that
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. ,
1 as the tape with the alcohol thereon passes through the hot air
knife, the hot air blast (90~ Farenheit, for example) will blow
and evaporate the alcohol from the tape leaving a clean and dry
surface. The tape then passes over guide pulley 32 and onto the
take-up reel 34 both of which are mounted on the frame 12. A
cover 107 is mounted on the bracket 104 and has openings to permit
the tape to pass into and out of the dewatering solution. The ~-
cover covers the tank 98 when the frame 12 is lowered. -
The tape is moved through the cleaning apparatus by means
10 of the positive drive on the take-up reel 34. It has been found ;~
that pulling the tape through the apparatus at the rate of twenty ~ ~;
feet per minute and at a tension of the order of ten to fifteen
ounces, resulted in the apparatus providing a clean tape ready for
long, trouble-free use.
As can be seen in Figures 1 and 2, the frame 12 can be
raised above the base 11 for initially threading the tape 16
around the appropriate pulleys and through the appropriate
openings, the frame can then be lowered with the electrodes 66,
and pulleys 64, 82, and 102 submerged in the appropriate solutions
so that the tape, as it passes through the electrodes 66 and
around pulleys 64, 8-2 and 102, is submerged for cleaning. -
In a modified form of apparatus, as shown in Figure 6,
the cooling air tube, at the exit of the mercury contact bath 22,
is removed and is replaced by a nozzle 120 carried by the frame 12
and pointing toward the tape 16. The nozzle 120 is connected to a
pump 122 which draws acid solution from the acid bath 26. The
nozzle 120 sprays the acid solution onto the tape 16 as said tape
leaves said mercury bath. The acid solution will cool the tape -
which has been heated by the electrical resistance in the tape as ~ -
3~ the positive electric current is applied to the tape by the
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1 electrochemical power supply 52. The spray of acid solution will
drain back into the acid tank. The acid sprayed onto the heated
tape will precondition the surface of the tape for the subsequent
electrochemical or electropolishing cleaning of the tape.
It is also contemplated that the water rinse bath 28
could be two baths,one made up of tap water and the other made up
of deionized water. In this form of invention, air knives would
be provided at the exit of each water rinse bath to strip the
water and other loose contaminants, such as mercury, phosphoric
acid, oxides or the like, fro~ the tape.
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