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Sept. 10, 1-946.
'
“ ‘w, P, MASON
'
2,407,315
LIQUID MEDIUM FOR ULTRASONIC COMPRESSIONAL WAVE TRANSMISSION
‘
Filed Oc't. 6. 1943
.
2 Sheets-Sheet 1
FIG /
INVENTOR
By
W . B MASON
:f $ .47‘ TORNEP
‘
Sept. 10, 1,946.
I
w. P. MASON
2,407,315
LIQUID MEDIUM FOR ULTRASbNIC COMPRESSIONAL WAVE TRANSMISSION
Filed Oct. s, 1943
‘2 Shoals-Sheet 2
H612
.IQCOUSTIC IMPEDANCE 0F MIXTUIES 0MP Aw I"? AT "'6. AND IMKC.
p - aumrr
v - moan-r
W, = 4:00am lumwvct
L80 -
I40 -
34%
x: x
L30
m:
L30
"
‘
uo -
L00 '
w ,9 msozv
Patented set; 10, 1946 ‘ v
' 2,401,315
Q'UNI‘TED STATES PATENT OFFICE
‘
2,407,315
'
-
LIQUID MEDIUM FOR ULTRASONIC GOM
PBESSIONAL WAVE TRANSMISSION
Warren 1’. Mason, West Orange, N. 5., assignor' to
Bell Telephone Laboratories, Incorporated, New
York,'N. Y., a corporation of New York
Application October '6, 1943, Serial No. 505,158
'
2 Claims.
(01. 252-1) .
.
This invention relates to ultrasonic compres
sional wave transmission and has for its object the
discovery and use of a medium which will support
the transmission of high power.
- It has been shown that the phenomenon of
I‘ cavitation imposes a limit on the amount of
power which may be transmitted by a transducer,
the transducers provided having a capability of
transmitting far greater power than can be sup
ported by the surrounding medium.‘
'
One form of transducer in common use con
sists of an array of piezoelectric crystals which
respond to electrical excitation to produce com
pressional waves in a surrounding medium such
,2
struction even after cavitation has been estab
lished.
_
Investigation has shown that when an object is
moved in a liquid insuch a way as to put a ten
sile strain on the liquid, if the movement is-of
su?‘lcient rapidity voids are torn in the liquid. ‘
When these voids collapse the movement of the
liquid has‘ acquired a certain momentum which
leads to great and destructive forces being brought
10 to bear on anything in the path of such move- ‘
ment. It has further been found that this phe
nomenon of cavitation starts somewhat more
readily and has less destructive effect in a liquid
in which a considerable amount of gas has been
as sea water; but it has been found that sea 15 dissolved. Whereas in such a liquid, gaseous
water will not transmit a great concentration of
power before the phenomenon of cavitation sets
bubbles may easily be formed, as by agitation, the
bubbles so formed'are easily expanded by the
forces which establish cavitation but are ?lled
in and imposes a practical limit thereto and it
has also been found that besides limiting the
with vapor of the liquid .or the dissolved gas and
power which may be transmitted, that cavitation 20 consequently do not collapse with such great
leads to rapid physical destruction of the trans-‘
force as'would a void approaching a vacuum.
ducer.
Hence a transducer in such a liquid is not sub
Some advance in the means to transmit greater
ject to such rapid destruction as it would be if
power has been made by immersing the trans
operated in a non-gaseous liquid. But the gaseous
ducers in another liquid which will support a
turbulence set up in such a gaseous liquid has just
greater power than sea water and then inter
as limiting an effect as true cavitation on the
‘ posing between such surrounding liquid and the
transmission of power.
sea water in diaphragm having a much greater
One means for increasing the power that may
area than the effective area of the faces of the
be transmitted through a liquid medium‘ is there
transducers so that the power transmitted there 30 fore to use a non-gaseous or a degassed liquid.
by per unit of area is comparatively small. In
It has further been found that the cohesive
this way the total power transmitted may be
force which is related to the tensile strength of
greatly increased. However, even in this case, the
the liquid is the chief factor which determines
power transmitted by. the transducer has to be
the amount of power the liquid will .transmit be
limited a reasonable amount below the point at 35 fore cavitation sets in. It is, therefore, desirable
which cavitation will begin so as to avoid de
to employ a liquid which has a high cohesive
struction of the transducer should the power be
force.
momentarily raised above the danger point.
It is a speci?c object of the present invention to
.
-
'
Applicant has discovered that a great amount
of power may be transmitted by employing a liquid
provide means whereby the power which the 40 which'is non-gaseous, has a high cohesive force
liquid medium in contact with the transducer will
and in addition has a high vapor pressure. This supportjmay'be transmitted freely and whereby
last factor is one which causes the liquid'to act
the tra'nsducer‘may be operated without de
in the same manner as a gaseous liquid for due‘to
2,407,315
I
‘
3
4
form a sealed chamber housing the electrical ap
paratus and ?lled with a liquid medium 3 such
as a mixture of dimethyl p'hthalate and xylene
hexailuoride. The electrical apparatus consists
of a plurality of piezoelectric crystal mosaics
such as 4, 5 and 6, each with its resonator 1, 8
and 9 respectively mounted on a plate In. With
in a housing H, also attached to the mounting
the high vapor pressure voids torn in such liquid
are filled with vapor of the liquid and hence
do not collapse with the destructive effect of voids
which more nearly approach a vacuum. There
fore, given a liquid medium which will support a
large power transmission before cavitation sets
in, it may be employed up to the limit because
like the turbulence set up in a gaseous liquid the
plate l0, there is contained other electrical ap
cavitation here set up is robbed of its destructive
power through its, high vapor pressure and hence 10 paratus such as ?lters and delay networks ,used
when such a transducer is connected as a prism
if the limit is overstepped the transducer will not
array. The device is shown as submerged in
> be immediately ruined.
water I2 and the vertical broken lines to the
It can be said in general that as the cohesive
right of the pc rubber cap represent a compres
force of various liquids increases, the vapor pres
sure thereof decreases. A feature of the present __ sional wave as being transmitted.
The graphs of Fig. 2 represent the values of p
the density, 12 the velocity and p1: the acoustic
impedance of various mixtures of DMP and XHF.
sure.
Horizontal lines at values between, 1.5 and 1.6
While the above is a primary requirement, there
are other qualities which such a liquid must 20 represent the po values of sea water so it will be
‘seen that DMP has a higher pu value and XHF
have. It must have a very high electrical resist
has a lower pv value than sea water. It will be
ance so that no effective electrical connections
noted that the density of the mixtures lies accu
will be made thereover between electrodes which
rately on a straight line between the terminal
are immersed therein. It musthave low viscosity
to avoid heating at the crystal face through the 25 values. The basis for this relationship is given
invention therefore is a liquid characterized both
by a high cohesive force and a high vapor pres
by the formula
violent mechanical agitation of the liquid there
at. It must have a mechanical impedance equal
to sea water and it must not physically or chem
ically affect the devices and parts with which it
comes in contact.
Applicant has discovered that a mixture of
dimethyl phthalate and xylene hexa?uoride most
nearly ful?lls all of these requirements.
Dimethyl phthalate, hereinafter referred to as
30" where p1 and p2 are the densities of the two com
ponents, X is the proportion of the first com
ponent‘and (l-X) that of the second. For this
mixture of DMP and XHF this relation is quite
accurate when used for the density but not for
the velocity and impedance. The next plausible
DMP, is a derivative of benzene and an ester of 35 assumption is that sound travels through the
phthalic acid having the chemical formula
liquid as if it went first through all of one pure
CeH4(COOCH3) a. This liquid ranks among the
component the-rest of a given distance. This
highest in its cohesive force and at the same time
leads to ‘the relation for the velocity. has a low viscosity. It has a low vapor pressure.
Xylene hexa?uoride, hereinafter referred to as 40
XHF, is another derivative of benzene and has
the chemical formula CaI-IdCFa) 2. While it‘has
a low cohesive force it has a very high vapor pres
_____
viva
" T.+“(1-Xiv‘.
Applying this relation to the present components
gives an over-connection. Actually, the experi
sure and a low viscosity, Generally speaking
these liquids having a high vapor pressure are
good solvents and have a highly corrosive effect
mental points, from which the graph for u were
on the rubber which is used as a diaphragm.
empirical relations, the line for v in Fig. 2 repre
XHF is peculiar in this respect that while it has
a high vapor pressure it nevertheless has a high
plotted, lie closely half-way between these two
senting the equation
inertness to the materials with which it will come 50
in contact.
The mixture of DMP and xl-IF has a cohesive
From this relation and the values for p was de
force between those of the two components but
retains the high vapor pressure of the XHF.
rived‘ the line for pr.
This chart may be used ‘to determine the vol
Through proper proportioning of the two com 55
ume proportions required to give any acoustic
ponents it will provide an exact match in me
impedance within the range of the components.
chanical impedance to sea water. The mixture
also has the low viscosity of the two components.
Forinstance, the values of pi) for sea water at
25“l C. and at 15° C. are shown by dotted lines on
Another feature ‘of the invention is a mixture
of DMP and XHF in proportions to provide an 60 the chart. The curve for pc of the mixture shows
that for the mixture at 25° C. to match sea water
exact mechanical impedancematch to sea water.
at 25° C., the components should be '73 per cent
Other features will appear hereinafter.
‘
The drawings consist of two sheets having two
DMP and 2'! per cent XHF. For the mixture to
simulate sea water at ‘15° C. the components
?gures as follows:
Fig. 1 is a side view, partly in section of an
should be 66 per cent DMP and 34 per cent XHF.
electromechanical transducer in which the liquid
Finally for a mixture to match sea water when
medium of the present invention may be em
both are at 15° C. the rough temperature cor
rection of three parts per thousand per degree
ployed; and
may be used. The impedance of the mixture
Fig. 2 is a graphical representation of certain
properties of various mixtures DMP and XHF.
70 should thus be about 1.504Xl0‘s ohm/cm.2 at
25°C. in order to become 1549x105. at 15° C. and
The electromechanical transducer shown in
the proportions shown by'the chart are 62 per
Fig. 1 comprises a casing I of steel or other rigid
cent DMP and 38 per cent XHF.
and mechanically strong material and a cap 2
The method pointed out by the above example
of plastic material such as that known as p0 rub
ber. These two elements are bolted together to 75 may be used in determining the proper propor
2,407,315
6
-
.
tions of other mixturesof other liquids when the
of BM? and three parts of XHF being some
acoustic impedance of sea water is to be matched.
where midway between the two. ' “
The following table gives the acoustic properties
While other oils and mixtures have higher cavi
tation pressures (directly relatedto the cohesive
temperature at which these properties were 5 force) other properties prevent their use.
measured is noted for the purpose of making
As a i'urther guide to the selection of a. liq
temperature corrections.
uid medium a third table listing the general range
of a number of liquids at one megacycle and the
Table 1
Density p
Liquid
“mum
in g/cc.
Velocity 0 Tem mm"
in m/sec.
_ A071,?‘
'
Ethylene chloride
Sea water.
Do‘
___
Alpha methyl nap" “me
010E101!-
Distilled water
H10
_-
Peanut oil
Corn oil
Cottonseed oil
. __
Dimethyl phthalate .... _.
C5H4(C00CH;), ............ ._
Mineral oil
Acetylated castor oil-P8 _____ ._
goat's-14311: nil
rm 0
_-
--
_
O ive oil. _ _ _ _
ohms/cm I
1. 073
1. 025
1. 730
1. 569
1. 027
1. 648
1.090
Fuel oil-99 g'rsv“
Castor oil D B
'
Linseed 0"
Mechanical
impedance Temperature
p nXlOl m
m 5Q
1.495
_ . _ __
1. 495
25
1. 472
l. 430
25
25
. 921
1. 353
24
. 936
. 914
1. 363
1. 333
25
24
. 912
1. 330
24
l. 176
1. 722
25
. 868
1. 263
24
. 956
1. 363
.g
1, 1g;
. 912
26. 5
25
1. 308
25
1. 574
1. 155
2A
1. 645
24
24.3
25
Decalin._
____ CmHu
Dibutyl phthalate __________________ _.__ 01114000041510; ........... .-
.8765
1. 032
1. 245
1. 455
Tricresyl phosphate"
1. 153
1. 620
24
___
1. 158
1. 630
24
CH1COCH;C(CH|OH), ____ -_
013K031): ................ -_
. 910
. 854
. 810
1. 280
1.150
1. 072
24
24
25
D0.
Diacetone alcohol ____________________ __
Diethyl benzene ..................... -_
Kerosene____
__ _
Pentanediol __________________________ ._
' 1-2-4 trichlor-benzene..Carbon tetrachloride _________________ -_
'
24
.
1. 104
Chlor nated diphenyl-
25
.998
.990
.969
.
Diethf'l phthslate .................... .. CQHKGOOCMHI)! .... _-. .... ._
25
25
15
éCHrhCOHCH: ............ __
‘H101.
___
. 913
1. 441
l. 192
1. 849
C014 .................. ._
l. 595
1. 478
24
24.
25
X lene bexa?uoride __________________ _- O¢H4(OF;):..
1. 370
1. 205
25
D +DMP (equal parts of castor oil
1. 080
1. 585
20
D B and dimethyl-phthelate) .
of viscosity and vapor pressures’ is here given.
From this table various mixtures may be pro
duced whose impedance will match that of sea 40 In the column of viscosity the ?guresrepresent
water. Providing other properties of the liquids
viscosity ranges as follows:
meet given requirements, the proportions of the
liquids to be used may thus be readily deter
mined.
1.
2;
3.
4.
For the purposes hereinabove set forth in or
der to provide a liquid which has 5 high cavita
Carbon tetrachloride
Kerosene
Olive oil
Castor oil
i
tion pressure the following values have been de
termined and are herein set forth in:
In the column oi’ vapor pressures the letters irep
resent vapor pressure ranges of the following'
orders:
»
50
Table 2
A. 1 cm. Hg or more .
B. .1 cm. H8
Prefssurtehon
the
ietgci
0
e
crys
C. ' .01 Cm. Hg
ag8mstthenquid_
Liquid _
expresedinatmos
D. .001 cm. H8’ .
55
>
pheres per cent
'
Table 3
Olive oil_____‘____~_
7.5
DB (caster 011) ..... __
P8 (acetylated caster o
3%
.
6.5
DMP _______ _.' _________ __
6.1
85% DM P+15% DB__
Peanut oil .......... _.
5.3
5.2
5.2
perm
4 parts DMP+3 parts XHF.
Soy been 011..
_
3 parts DM P+1 part DB
Carbon tetrachloride
Kerosene ___________________ __
-
vs cos- '
ity
v
a or
presgure
'oxlo‘
’
P
0.969
4
C
1.43
1.477
(P8) ................ --
4
C
1.387
1.451
.956
3
3
3
3
3
3
B
B
B
B
B
B
1.308
1.333
1.363
1.362
1.333
1.353
1.431
1.463
1.458
1.461
1.463
1.468
.912
.914
.936
.919
.912
.921
4.4
4.2
4.0
3.9
3.9
3.7
L
d i]
_.
2.8
3.4
@rennoiL.
erosene ............. -_
3
B
1.022
1.268 1.324
1.440
.81
Xylene hexa?uoride _______________________ __
2.6
aMethylnaphthalene“
Dimeth lphthalate____
1
234
A
1)
1.643 1.510
1.722 1.463
1.090
1.176
1.595
4! Methyl naphthalene
'
.
Cestoroil (DB) ______ __
Acetylated eastor oil
5.0
________________________ __
Linseed oil
Liquid
60
3
B
.88
70 Xylene exailuoride-.._
'1
A
1.205
.879 1.37
Carbontetrachloride.._
1
A
1.595
.926
From this table it will be seen that dimethyl
phthalate ranks among the highest in cavitation
pressures and that xylene hexa?uoride is the
' of the above table it appears that ‘
On the basis
lowest here recorded, the mixture of four parts 75. a methyl naphthalene and carbon tetrachloride
2,407,315
7
~ .
are both suitable from the standpoint 01' high
What is claimed is:
vapor pressure but it will be noted that both of
1. A mixture or 57 per cent by volume of
these liquids have too high a mechanical imped
ance (pv) for mixture with DMP to provide a
match with sea, water and in addition both will
attack rubber.
‘
.
'
It therefore appears that the mixture of
dimethyl phthalate and xylene hexa?uoride is a
peculiar and novel combination oi’ liquids produc
ing a liquid medium for electromechanical trans
ducers and other like apparatus having the great
est combination of desirable properties.
v
dimethyl phthaiate and 43 per cent by volume of
xylene hexa?uoride.’
2. In a mixture of liquids having high cohesive
force to support large power transmission and
high vapor pressure to reduce the destructive ei
fect of cavitation, the combination of dimethyl
phthalate and xylene hexa?uoride in substantially
10 the proportions of tour volumes of dimethyl
phthalate and three volumes of xylene hoxaiiuo
ride.
.
‘WARREN P. MASON.
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