Note: Descriptions are shown in the official language in which they were submitted.
l99~_D~D~ vention
This irlvention relates to me~hod and apparatus ~or
tr~atin~ m~tal ~trip with ultr~sonic wave energy.
~t has already been propo~ed t~ pickle, clean and
polish metal ~trip and wlre~ u~inq ult~.asonic wave energy
in a treating ~olution which may be acid, a detergent or
a liquid with abr~sive particle~ ~u~pen~ed in the liquid.
Exampl~s of prior ar~ U. S. patents in ~his field are
Englehart 2,894,860, Osterma~ e~ al 3,066,0~4 and Sasaki
30240,g63.
It has al~o been propos@d to utilize the reflection
characteristics of ultra~onic wave energy to treat object~
in treating solution~ where the ene~gy is reflected froM
tank ~urfaces and the ~uxface of the treating solution.
; Example~ of prior art U. S. patent~ o this category ar0
~ran~on 2,987,068, Hightower 3,033,710 and Kouril 3,433,669.
Further, it ha~ been propo~ed to use heavy granite
tank~ for pickling a~ de~cribed in U. S. patent to White
et al, 3,473,791.
It is now well known that highly effioient ultra
sonic wave energy generator~ produce a beam of wave energy
with only ~light divergence, for e~ample 5~, and thus that
the effect of the beam of w~ve energy in a treating solu-
; tion on object~ in its path i8 localized. It ~ollows that
e~fective treatment of a ~trip o~ metal moving through a
treating solut.ion with ultraso~ic generators directed
toward the strip and relying only on dir~ct action of the
beam of energy would require an economically prohibitiv~
number of generators. Such u8e of ultra~onic g~nerator3
or tran~ducer6 al~o xuns into problems of ~tanding Iwaves
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which reduce or even render ineffective the desired action of the
untrasonic energy. Even where reflection of the 8enerated beam of
ultrasonic wave energy has b~en contemplated~ attenuation of the
energy in the beam by long paths through a treating solution has
reduced the effectiveness of such arrangement:s. ~8 a result the
ultrasonic treatment of movlng strips of metal has not progressed
in industry to the extent that might be expected.
The shortcomings of the prior art E)ractices have been
removed or alleviated in the present invention.
By one aspect of this invention there is provided apparatus
for continuo~sly treating moving metal s~rip with ultrasonic wave
energy compri~ing
an elongated open top tank having a bottom wall~ sidewalls and
endwalls,
a body of trea~ing solutlon in the tank,
means for introducing the moving metal strip into the treating
solution near one end of the tank, moving the metal strip through
the treating ~olu~ion and withdrawing the metal strip from the treat-
ing solution near the other end of the tank,
imperforate cover means for the open top of the tank extending
across the top of the tank in spaced relation to the body of treating
solution, the cover means including means forming a plurality of
openlngs in the cover means,
a plurality of transducer means, each having a bottom, for
generating a beam of ultrasonlc wave energy and emanating the beam
of the ultrasonlc energy out of the bottom of the transducer means,
a plurality of receptacle means each having liquid impermeable
bottom and sidewalls for holding a liquid, the bottom wall being
formed of ultrasonic energy transmlssible material,
a body of liquid in each receptacle means,
means associated with the means forming the openln~s in the cover
means for supportlng the receptacle means in the openings with at least
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the bottom wall of the receptaclc means in contact wlth the treatlng
solution and above the moving strip~
each receptacle means supporting a transducer means in the recept-
acle means with at least a major portion of the transducer means
immersed in the body of liquid in the receptacle means and with the
beam of ultrasonic energy directed at an angle other than 90 to the
bottom wall of the tank, through the ultrasonic energy transmissible
material of the receptacle means bottom wall, through the moving metal
strip and against the bottom wall of the tank.
In a preferred embodiment o~ this invention the aforesaid
apparatus also comprises a cover for an elongated open top tank for con-
.
tinuously treating moving metal strip w1th ultrasonic wave energy which
supports receptacle means having liquid impermeable bottom and side
walls for holding a liquid, the bottom wall of the receptacle being
formed of ultrasonic energy transmissible material and means associated
with receptacle ~eans for supporting transducer means for generating
waves of mechQnical vibratory energy at ultrasonic frequency and emanat-
ing the beams through the receptacle means bottom wall and through the
moving metal strip.
By another aspect of this invention there is provided the
method of continuously treating moving metal strip with ultrasonic wave
energy comprising
providing an elongated open top tank having end walls, sidewalls and
having a bottom wall sloping down~ard from at least one sidewall toward
the other sidewall, the upwardly facing surface of the bottom wall having
the ability to reflect ultrasonic energy efficiently,
providing a body of treating solution in the tank having a top sur-
face located above ~he bottom of the tank a distance not substantially
greater than that required to cover the widest metal strip to be treated,
3~ introducing the moving metal strip into the body of t:reating solu-
tion, moving the metal strip through the treating solutLon and withdraw-
ing the metal strip from the treating solution,
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providing a plurality of receptacles, each receptacle holding a body
of l~quid other than the treating solution and being positioned with the
bottom wall of the receptacle in contact with the treatin~ solution, the
bottom wall of the receptacle being formed of ultrasonic energy transmis-
sible material,
generating a beam of ultrasonic wave energy under the surface of the
body of liquid in each receptacle,
arranging the plurality of receptacle~ along the length dimension of the
moving metal strip with each of the plurality of beams of ultrasonic wave
energy generated in the receptacles directed downwardly toward one of the
marginal portions of the moving metal strip, and
pro~ecting the generated beam of ultrasonic energy through the bottom
wall of each receptacle, through sa:Ld marginal por~ion of the moving metal
strip and onto the bottom of the tank so as to be reflected therefrom, the
angle of incidence of the beam of ultrasonic energy on the bottom and the
slope of the bottom a~ the place of incidence of the beam on the bottom being
such that ~he reflected beam passes through the moving metal strip at a dif-
ferent place located inwardly of said marginzl portion relative to the width
of the atrip from the place where the beam first passed through the moving
metal strip and the reflected beam impinges against and is again reflected
from the top surface of the treating solution and passes through the moving
metal strip at still another place.
Thus, by a more preferred embodiment the present invention utilizes
an elongated, very shallow bath of treating solution coupled with a sloping
~ tank bottom that will reflect ultrasonlc wave energy and suspended ultrasonic
: generators, submerged in water and isolated from attack by the treating solu-
tion, directed downwardly so that the beam of generated ultrasonic energy
passes through the moving metal strip, impinges on the sloping tank bottom in
a direction transverse of strip movement~ is reflected upwardly through the
moving strip at a different point, is reflected downwardly from the surface
of the ~olution
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through the moving metal strip at still another point across
the width of the strip, impinges again on the sloping bottom,
repetition of these reflections acting to repeat the ultra-
sonic energy treatment of the metal strip across its full
width. For best results the generated beam of ultrasonic
energy should go through the marginal portion of at least
one edge of the strip and be reflected upwardly but in the
general direction of the other marginal portion of the strip.
Thus with a sloping tank bottom as shown in the drawings, or
with the slope being due to an arcuate shape, an ultrasonic
generator is positioned over one maryinal portion of the
strip with the beam directed vertically downward or at an
.
angle toward the intermediate portion of the tank, depending ~.
upon the slope of the bottom, so that the marginal portion of ~.
one edge of the strip will receive the beam directly from the .~:
generator. As shown in the drawings, another generator can
be positioned above the marginal portion of the other edge of
the strip in a similar manner but arranged so that standing
waves are not set up by the two beams of ultrasonic energy.
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Brief Description of the Drawin~s
Figure 1 is a plan view of an elongated tank for
treating a moving strip of metal/ with parts omitted for
simplicity and clarity;
Figure 2 is a view in longitud~nal section taken on
the line 2--2 of Figure 1 with a metal strip shown in position
in the tank;
Figure 3 is a view in cross section taken on the
line 3--3 of Figure l;
Figure 4 is a view in cross section taken on the
line 4--4 of Figure l;
Figure 5 is a view in cross section taken on the
line 5--5 of Figure l;
Figure 6 is an enlarged, fragmentary view in plan
of an arrangement of transducers for the central portion of
the tank shown in Figure 2; :
Figure 7 is an enlarged view in cross section taken
on the line 7--7 of Figure 6;
Figure 8 is a view in perspective of a tank cover
showing receptacles for holding transducers;
Figure 9 is an enlarged, fragmentary view in sac-
tion taken on the line 9--9 of Figure 8 with the transducer
and immersion liquid shown in place;
: Figure 10 is a vi~w similar to Figure 6 showing a
different arrangement of transducers;
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Figure 11 is a fragmentary, enlarged view in sec-
tion taken on the line 11--11 of Figure 10;
Figure 12 is an enlarged view in cross section
taken on the line 12--12 of Figure 10;
Figure 13 is a plan view sirnilar to Figures 6 and
10 but showing three covers, of another arrangement of trans-
ducers;
Figure 14 is an enlarged view in cross section
taken on the line 14--14 of Figure 13; and
Figure 15 is an enlarged view in section taken on
the line 15--15 of Figure 13.
Detailed Description of the Method and
Embodiments of the Invention
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; Although the present invention is applicable to any
treatment of metal strip with ultrasonic wave energy, such as
pickling steel strip and cleaning or polishing any metal
strip, the invention is especially suited to the pickling of
steel strip and will therefore be described in this environ-
ment.
Referring to Figures 1 to 5, a long, extremely ;
shallow pickling tank, indica-ted generally at 20, is shown,
the bottom and side walls of which are formed from four mono-
lithic granite slabs, the middle two slabs being hollowed out
to form that portion of tank 20 and the other two being hol-
lowed out to form the two differently shaped end portions
of tank 20. Referring particularly to Figures 1, 2 and 4,
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identical monolithic granite slabs are shown at 22. Simi-
larly Figures 1, 2 and 5 show a monol:ithic granite slab 24
similar in shape to slabs 22. Monolithic granite slab 25 the
shape of which is evident in Figures :l and 2 forms the other
. 5 end of tank 20. The slabs 22, 22 24 and 25 are cemented in
liquid-tight relation to each other. The moving strip 27,
shown in Figure 2, enters tank 20 from the right hand side in
Figures 1 and 2 and at this end of tank 20 a specially shaped
piece of granite 26 coacts with slab 24 to form a dam across
the rear end of tank 20 over which the pi.ckling solution in
the tank can flow into a sump 28 formed by dam member 26 and
a granite block 30. Granite block members 26 and 30 are
cemented in liquid-tight relation to slab 24 with block 31
bracing dam member 26. A drain 32 leads pickling solution .-
away from sump 28. Granite member 30 has cut in it an open-
ing 34 to admit strip 27 into tank 20, rolls 38, 38 serving
to move the strip forward.
At the other end of tank 20 granite slab 25 has an
~ inclined portion 42 which guides strip ~ up and out of tank
20 through an opening 44 at the upper end of the inclined
: portion 42 to rolls 46 which act in conjunction with rolls
~, 38 to move the strip through tank 20. Sloping portion 42 of
granite slab 25 also acts as a dam to hold the treating solu-
.~, tion in the tank and a sump 48 is formed by granite members
50 and 51. As in the case of all the other grani.te components
_g_
~.
of the tank, members 50 and 51 are cemented in liquid-tight
relationship to each other and to the end of slab 25. Treat-
ing solution in sump 48 can drain out through drain openings
52. Although not shown in the drawings, a pickling line
incorporating the present invention can include a second
tank similar to tank 20 with the two tanks in tandem, tank 20
in such case being the second or final tank for treatment of
the steel strip with the strongest acid solution. Since the
present invention has its greatest advantage in the final
pickling tank, the earlier pickling tank has not been shown.
However, pickling solution from sumps 28 and 4~ can go on to
the earlier tank relative to movement of the strip where the
pickling solution need not be as concentrated.
The central portion of tank 20 which is formed by
slabs 22, 22 and 24, as best seen in Figure 4, is deepest
along its center line with straight sloping sides 54, 54
merging into upright side walls 55, 55. Obviously the bottom
can have an arcuate configuration.
~3perl ~ o p
~ The extremely shallow/tank of the present invention
has granite slabs forming covers 56, 56 covering the strip
entrance end portion of the tank and granite slabs forming
covers 57, 57 covering the exit end portion of the tank.
Tank 20 slants upward slightly toward the strip exit end so
that hydrogen gas evolved during the pickling treatment will
not collec~ under the covers and also because movement of the
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strip at high speed through the treating solution drags the
treating solution toward the exit end of the tank. Covers
57, 57 restrain the pickling solution at that end of the tank
from being carried out of the tank in too large quantities.
In lieu of additional granite covers, the central
portion of the tank in the present invention is enclosed by
plastic covers, indicated generally at 58 in Figures 1 and 2,
which are resistant to corrosive action by the pickling solu-
tion t these plastic covers being designed to hold a plurality
of ultrasonic wave energy generators or tranducers for ultra-
sonic treatment of the strip during its movement through the
pickling solution.
In Figure 1, only one granite cover and one plastic
cover are shown in order better to illustrate the tank and
its constituent parts but as shown in Figure 2 the entire
end portions of open top tank 20 are covered at one end by
granite covers 56, 56 and at the other end by granite covers
57, 57 with the entire intermediate section being closed by
the plastic covers 58 to be more specifically described
hereunder. The thus-enclosed tank has fumes and evolved
gases removed by a conventional suction exhaust system not
shown. Fresh pickling solution is added to the bath in the
tank at a convenient location near the strip exit end of the
tank. Dam member 26 determines the liquid level 59 in the
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tank although the moving strip drags treating solution out
the opening 44 at the other end oE the tank. Of course the
speed of the strip must be controlled so as not to lower the
liquid level below a desired level which can be a couple of
inches on the side walls 55 of the tank 20 or in other words,
not substantially above the widest strip that can be
accommodated by the tank.
As shown in Figures 2, 7 and 12, although rolls 38,
38 and 46, 46 maintain tension on strip 27~ the catenary
effect of the weight of the strip causes the strip to clroop
- and the design of tank 20 results in bottom walls 54, 54 of
slabs 22, 22 supporting the strip on its edges as it passes
through that portion of the tank.
Returning now to the plastic covers illustrated
generally at 58 in Figures l and 2, these covers are con-
veniently dimensioned the same as granite covers 56 and 57 and
as in the case of covers 56 and 5~, the bottoms of these
covers are spaced above the liquid level 59 of the treating
solution to permit flow of fumes and gases along the length
of the tank.
In the embodiment of the invention illustrated in
Figures 6, 7, 8 and 9, each of the plastic covers 58 comprises an
imperforate body portion 60 having flanges 61 for supporting the
cover on the top surfaces of the ~ide walls 55, 55 of tank
20, the transverse edges of the cover relative to the length
of the tank being chamfered at 62 for sealing engagement with
adjacent covers. The body portion 60 can be formed in any
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desired manner but as shown in Figure 9, it is conven:Lently
formed of sheets of plastic such as polypropylene, which i8
corrosion resistant in respect to acid used in pickling steel,
cemented or welded to form the desired shape. Openinga 64
are formed at desired locations through the body portion 60
of each cover and pans or open-top liqu:id impervious recep-t-
acles 66 having supporting flanges 67 a:re resting on the
plastic material surrounding the openings fitted into each
opening 64. A resilient gasket 68 seals the ~oint between
receptacle 67 and the plastic material surrounding opening
64 to prevent fumes from the pickling bath escaping to the
atmosphere. Receptacles 66 may be formed of fiberglass which
is resistant to corrosion by acid used to pickle steel and
which transmits ultrasonic wave energy, satisfactory product
being molded fiberglass No. 811-101 manufactured by Rockwell
International Corporation.
The lower portions and bottom walls of receptacles
66 extend below the bottoms of covers 60 so as to project
below the liquid level 59 oE the pickling solution in tank
20. Received within each receptacle 66 and positioned in
any suitable manner therein is an ultrasonic energy generat-
ing unit or transducer 70 having a bottom wall 71 resting on
the bottom of receptacle 66. Each ultrasonic wave energy
generating unit or transducer unit 70 comprises an entirely
closed and sealed metal box which contains up to a dozen
ultrasonic wave energy gen~ra~ing elements or transducer
elements, all arranged in the container with their sonic
energy emanating faces directed toward the bottom wall 71
of container 70. The group of ultrasonic wave energy
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generating elemen-ts thus act to produce a combined beam oE
ultrasonic wave energy emanating downwardly in a direction
normal -to and through the bottom 71 of con~ainer 70. Recept-
acle 66 is filled with a liquid such as water to a height
above the transducer. As thus assembled, the beam of ultra-
sonic energy emanating from the bottom 71 of container 70
passes through the bottom of receptacle 66, the fiberglass
being chosen as the material of receptacle 66 because it
will transmit ultrasonic wave energy efficiontly for as long
as six months. It has been found that the beam of ultra-
sonic wave energy emanating downwardly from the bottom 71
of container 70 is substantially nondivergent, a divergenc~
of only 5 on all sides of the beam being the rule.
The embodiment illustrated in Figures 6 and 8
incorporates 15 receptacles 66 and containS ultrasonic
transducers in each cover 58 disposed in longitudinal and
transverse rows. It will be apparent that with the slight
amount of divergence of the ultrasonic energy beam emanated
by transducer units 70, strip 27 moving through tank 20
will be subject to direct radiation over an area consider-
ably less than the total areaO The applicants have found
however that the beams of ultrasonic energy from each trans-
ducer 70 pass through the strip and impinge upon a bottom
wall 54 from whence they are reflected upwardly at an angle
toward the center line of the pickling tank. The extremely
shallow bath of -~he present invention and the nature of
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monolithic granite coact to give very efficient reflection of
energy and each reflected beam again passes through the strip
but at another place, from whence it goes to the surface of
the liquid there to be reflected back:wardly again toward the
bottom through the strip at still another place, into engage-
ment with the bottom of the tank and so on across the width
of the tank and the strip. In this way, the arrangement of
15 spaced transducer units 70 illustrated in Figures 6 to 8
very adequately subjects the entire strip to the action of
ultrasonic wave energy and for reasons now well known the
pickling action is greatly expedited.
It will be noted that the rows of transducers in
the embodiment of Figures 6 and 8 are arranged closer
together on one side of the strip than the other. Where
desired, this arrangement can be reversed in alternate covers
but the applicants have found that with the arrangement shown
a very complete and uniform pickling is achieved across the
width of the strip despite the fact that steel strip has a
more tenacious oxide film along its marginal portions than in
the center. Looking at Figure 7 it will be seen that the
transducers on the left-hand side of this figure, the lower
rows in Figure 6, send a concentrated massing of ultrasonic
wave energy onto and through the strip, regardless of its
width. Those portions of the left-hand side of the metal
strip in Figure 7 not su~jected to direct ultrasonic
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radiation are subjected to mass reflected ultrasonic radia-
tion from bottom 54. The transducers which are spaced far-
ther apart on the right-hand side of Figure 7, the upper
transducers in Figure 6, merely supplement the action of
those already described and assure uniform pickling under all
the varying conditions of everyday pickling operations.
In fact, as indicated in Figure 10, where econom~
in the use of transducers is the desideratum, much fewer
transducers can be used as shown in the arrangements of
transducers appearing in the three covers on the left-hand
side of Figure 10. In the case of the embodiment disclosed
in Figures 10, 11 and 12, the bank arrangement of transducers
in the cover on the extreme right can constitute a reserve
supply of energy in case a steel strip is highly resistant to
normal pickling action or the pickling line speed is in-
creased for some reason or the temperature of the pickling , -
solution is reduced for some reason.
The angled position o~ the transducers as shown in
the extreme right-hand cover 58 of Figure 10 has been -Eound
, 20 to be effective under some operating conditions. A variation
of this arrangement is shown in the extreme right-hand cover
of Figure 13 and Figures 14 and lS. The reason for an effec-
tive radiation pattern when the transducers are at an angle
as shown in these modifications seems to be that the beam
~5 directly lmpinging on the strip and thereafter on the bottom
of tank 20 covers a much larger area of the strip and tank
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bottom than when the beam is pro~ected vertically on the horizontal strip~
Preferably at least some of the transducer units are supported so as to
; impinge the ultrasonic energy emanating from the transducers on the moving
strip at an angle of incidence to the strip of between about 30 and about
60-
Figures 13 through 15 disclose variations of transducer arrange-
ments which have been found to give satisfactory pickling results. It will
be noted that in Figures 1~ and 15 each of the transducers 70 has a portion
projecting above the liquid level in the associated receptac]e 66 with the
liquid level at a practical height, as illustrated in Figure 9; however the
major portion of each transducer would in such case be immersed in the liquid.
An e~amination of the phenomenon present in all the disclosed
modifications and which is shown diagrammatically in Figure 12, shows why
ultrasonic wave energy treatment of metal strip in any treating solution
can be accomplished with transducers only along one marginal portion of the
strip. The dotted lines show the paths of directly radiated ultrasonic
energy and the paths of reflected ultrasonic energy from the granite bottom
of the tank and from the surface of the treating solution, with the paths
of the beams of ultrasonic energy repeatedly passing through the strip all
the way across its width.
For some unknown reason it seems that best results are
obtained with all the transducer arrangements disclosed in the drawings
when ultrasonic wave energy passes through the marginal portion of at least
one edge of the strip. Of course in any event it will be apparent that the
marginal portion of the strip receives no appreciable ultrasonic energy
rad-lation when the margin of the strip pro~ects outwardly past the beam of
the farthest out transducer since the direct beam thus passing through the
strip inwardly of the marginal portion of the strip is reflected inwardly
toward the center of the strip.
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In an example of actual use of this invention in
the steel strip pickling field, steel strip is passed at a
speed between about lO0 feet per minute and about 300 feet
per minute through two 50-foot long granite bottom tanks con-
taining a solution of hydrochloric acid. The tanks slope up-
wardly in the direction of movement of the strip because the
strip pulls the solution along with it especially at the
higher speeds of pickling possible with the use of ultrasonic
energy. The strip varies in width from about 30 inches to
about 60 inches. When the narrower widths of strip are being
pickled, the transducers or ultrasonic energy generators which
are located outside the edges of the strip need not be acti-
vated but the cost of operation is negligible and the energy
repeatedly reflected from the tank bottom and solution surface
passes toward the other side of the tank and thus passes
repeatedly through the strip. The first tank in direction of
strip movement has the lower concentxation of acid, namely
between about 3% and about 6%. The second tank in the direc-
tion of strip movement needs an acid concentration of up to
about 15% hydrochloric acid where the present invention is not
~ec~
used. The ultrasonic energy is utilized in the ~e~4~ tank
where the acid concentration is greater. The ultrasonic fre-
quency used is 25,000 cycles. 20,000 cycles would be more de-
sirable but the only available commercial transducers operate
at 25,000 cycles or 40,000 cycles. A lower frequency does
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better pickling but the sound effects become objectionable
below about 20,000 cycles per second. Using the ultrasonic
energy the temperature of the pickling solution is dropped
down to about 185 to about 190 whereas without the invention
the bath must be run at 210 to 215. Using the invention an
acid concentration of about 9~ in the second tank is suffi- ;
cient which results in a saving in cost of acid. The lower
bath temperature gives less fumes and better cavitation by the
ultrasonic energy. Fresh solution is pumped into the second
tank relative to the movement of -the strip near the strip
exit end and most solution leaving the tank overflows out of
the strip entry end of that tank. The greater the speed of
the strip the more solution is dragged out of the tank at the
strip exit end and this places a limit on strip speed. The
amount of solution pumped into the tank considering the over-
flow at both ends is sufficient to maintain an inch to an
inch and a half of depth of solution on the side walls of the
tank. Effluent from both ends of the second tank relative to
strip movement is collected in a first holding tank and is
pumped from there into the first tank relative to strip move-
ment near the strip exit end and, as in the case of the
second tank, overflows mostly from the strip entry end of the
first tank. This overflow is discarded as spent pickle
liquor. The solution is pumped into the system at 150 gal-
lons per minute, the depth of the solution in the deepest
part of each tank being maintained at about 9 to 10 inches.
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In passing through the tanks, although the strip has tension
on it, there is a catenary effect which results in the edges
of the strip riding on the sloping surfaces of the bottom,
with the depth of pickling solution being just sufficient to
cover the widest strip to be treated.
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The described embodiments and method are to be con-
sidered in all respects as illustrative and not restrictive
since the invention may be embodied in other specific forms
without departing from its spirit or essential characteris-
tics. Therefore the scope of the invention is indicated by
the claims rather than by the foregoing description, and all
changes which come within the meaniny and range of the equiva- .
::
lents oE the claims are intended to be embraced therein.
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