U.S. patent number 3,844,159 [Application Number 05/328,373] was granted by the patent office on 1974-10-29 for liquid quality evaluating apparatus.
This patent grant is currently assigned to Fujisoku Electric Co., Ltd., Kitoku Co., Ltd., Showa Industries Co., Ltd.. Invention is credited to Fukuo Hata, Hiromu Kamatani, Masumi Mizutani.
United States Patent |
3,844,159 |
Mizutani , et al. |
October 29, 1974 |
LIQUID QUALITY EVALUATING APPARATUS
Abstract
This is an electrical apparatus for rapidly determining the
quality of a liquid such as automotive brake fluid by comparing its
boiling point with a predetermined reference value. Liquid to be
tested is heated to its boiling point in a first vessel having a
nozzle opening into a second vessel so as to transfer liquid when
boiled from the first to the second vessel. Temperature rise to a
predetermined value in the first vessel produces one signal and the
presence of boiled liquid in the second vessel produces a second
signal. Comparison of the time of occurrence of the two signals
indicates the relation of the boiling point of the sample to the
predetermined reference value.
Inventors: |
Mizutani; Masumi (Gifu,
JA), Hata; Fukuo (Tokyo, JA), Kamatani;
Hiromu (Yokohama, JA) |
Assignee: |
Showa Industries Co., Ltd.
(Gigu-ken, JA)
Kitoku Co., Ltd. (Tokyo, JA)
Fujisoku Electric Co., Ltd. (Kawasaki-shi,
JA)
|
Family
ID: |
23280735 |
Appl.
No.: |
05/328,373 |
Filed: |
January 31, 1973 |
Current U.S.
Class: |
374/21 |
Current CPC
Class: |
G01N
33/28 (20130101); G01N 25/10 (20130101) |
Current International
Class: |
G01N
33/26 (20060101); G01N 33/28 (20060101); G01N
25/02 (20060101); G01N 25/10 (20060101); G01h
025/10 (); G08b 023/00 () |
Field of
Search: |
;73/17,61.1R ;324/65R,7
;340/236,270 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Goldstein; Herbert
Attorney, Agent or Firm: Kemon, Palmer & Estabrook
Claims
What we claim is:
1. Apparatus for determining whether the boiling point of
hygroscopic liquid such as automotive brake fluid is at least above
or below a reference temperature comprising:
a first substantially closed vessel made of heat conductive
material for containing a predetermined sample of liquid to be
tested, said vessel being provided with a nozzle projecting from a
side wall, said nozzle having at least a portion higher than the
level of the sample liquid within said vessel;
means for controlled heating of said vessel;
a second vessel made of electrically conductive material,
positioned to receive said sample liquid when forced through said
nozzle by boiling in said first vessel;
a needle-like electrode having one end disposed within said second
vessel so as to be in contact with the boiled sample liquid
therein;
a current detection circuit forming a closed path through at least
the boiled sample liquid within said second vessel and saie
needle-like electrode for producing an output signal in response to
contact of the boiled sample with said electrode;
means for providing a different signal whenever the temperature of
liquid in said first vessel reaches a reference temperature;
and
indicating means responsive to said signals to indicate at least
whether the boiling point of said sample liquid is above or below a
reference temperature.
2. Apparatus as defined by claim 1 in which said vessels are
substantially U-shaped in cross-section and said first vessel
includes a cover having a capillary bore extending completely
therethrough said bore having an inside diameter of about
0.5mm.
3. Apparatus as defined by claim 1 in which said means for
controlled heating of said first vessel includes an electrically
resistive heating element connected in series with a variable
resistor and a power source.
4. Apparatus as defined in claim 1 wherein said current detection
circuit comprises:
an active circuit means having input and output electrodes;
said second vessel;
the boiled sample liquid in said second vessel;
said needle-like electrode;
a DC power source;
an excitation coil;
said input electrode being connected to said source and said output
electrode being connected through said excitation coil to said
source; and wherein said liquid temperature detection circuit
comprises:
a variable current path formed by a series circuit including a
second DC power source, a heat responsive resistance element in
said first vessel and a resistor;
a DC amplifier having its input connected to said series circuit
between said heat responsive resistive element and said
resistor;
a Schmidt circuit coupled to the output of said DC amplifier and
having a preset threshold voltage level indicative of a boiling
point substantially representing a boundary between good and bad
qualities of the same type of liquid as the sample liquid on the
test;
a driver circuit having its input coupled to the output of said
Schmidt circuit;
a second excitation coil connected between the output of said
driver circuit and said second DC source;
and wherein said indicating means includes a first normally open
lamp circuit arranged to be closed when said second excitation coil
is energized and a second normally open lamp circuit arranged to be
closed when the other of said excitation coils is energized.
5. Apparatus as defined by claim 1 wherein said current detection
circuit comprises:
an active circuit element means having input and output
electrodes;
said second mentioned vessels;
the boiled liquid in said second vessel;
said needle-like electtode;
a first DC power source;
an excitation coil;
said input electrode being connected to said first DC source and
said output electrode being connected through said excitation coil
to said source;
and wherein said liquid temperature detection circuit
comprises:
a bridge circuit one leg of which is a heat responsive resistence
element in said first vessel;
a second DC source connected across one pair of terminals of said
bridge circuit;
and wherein said indicating means comprises:
a temperature indicating DC galvanometer connected across the
opposite pair of terminals of said bridge; and
means responsive to energization of said excitation coil for
locking the pointer of said galvanometer.
6. Apparatus for determining whether the boiling point of a
hydroscopic liquid such as automotive brake fluid is at least above
or below a reference temperature comprising:
a heating vessel formed of a material both electrically and heat
conductive;
a needle-like electrode having one end disposed in proximity to the
inner bottom of said vessel;
a heating source for said vessel including a heater and a power
source coupled to said heater;
a current conduction path including said vessel, a sample liquid
poured into said vessel, said needle-like electrode, a resistor
connected to the opposite end of said needle-like electrode and a
DC power source connected between said vessel and said
resistor;
a Schmidt circuit having its input terminals connected across said
resistor and having a preset threshold voltage level; and
a counter coupled to the output of said Schmidt circuit to count a
number of output pulse signals therefrom.
Description
BACKGROUND OF THE INVENTION
This invention relates to a liquid quality evaluating apparatus for
evaluating the quality of any liquid such as a brake fluid for
automobiles.
Recent tendency has been towards using a brake fluid as high in
boiling point as possible so as to enhance brake performance. In
general, however, the higher the initial boiling point, the greater
the drop of the boiling point due to its hygroscopic property and
the degeneration of the brake fluid due to its hygroscopicity now
presents a problem. As is known the brake fluid decreases in
boiling point with an increase in the percentage of contained
water. On the other hand brake fluid reaches a high temperature at
the time of brake operation, particularly when a greater amount of
braking force such as on a steep downhill road is required. If the
brake fluid reaches its boiling point during the time of brake
operation, what is called "a vapor lock phenomenon" occurs with the
result that the braking force is lowered to an extreme extent,
presenting a possible greater peril under which an unexpected
traffic accident can take place. It is necessary, therefore, to
exchange the degenerated brake fluid reaching a certain water
content for a new one. The necessity for exchange has heretofore
been determined by judging the frequency of uses without resort to
checking the quality of a used brake fluid, or by sampling the
brake fluid and chemically analyzing its constituents. In the
former case however, a still usable brake fluid may be discarded
with the attendant uneconomical result, since no checking is made
as to the usability of the brake fluid. Furthermore, even a
relatively fresh brake fluid or one left unused, when placed in
moist or humid environments such as in a rainy season, reaches more
than a certain water content (usually 3 percent) than expected, and
its use is still continued without the knowledge that its has
become dangerous. In the latter case, a relatively intricate
chemical analysis, as well as a relatively long period of time, is
required with the attendant disadvantages.
A liquid, in general, to say nothing of a brake fluid for
automobiles, when an impurity is included therein, shows the
property that its boiling point varies.
Accordingly the object of this invention is to provide a liquid
quality evaluating apparatus capable of determining in a relatively
simple way and in a short period of time whether any sample liquid
is good or bad, by electrically detecting whether or not its
boiling point exceeds a predetermined temperature level.
SUMMARY OF THE INVENTION
A liquid quality evaluating apparatus according to a preferred
embodiment of this invention comprises: a sealed vessel made of a
heat conductive material contained therein a predetermined amount
of sample liquid and provided with a nozzle projecting in an
integral fashion from a predetermined side wall thereof so that a
section of the nozzle is at least higher in level than the upper
surface of the sample liquid contained within the sealed vessel; a
heating source including a heater disposed in proximity with the
sealed vessel and a power source connected across the heater;
another vessel made of an electric conductive material into which
the sample liquid boiled through the heating of the heating source
is forced through the nozzle; a needle-like electrode whose one end
is arranged within the second-mentioned vessel in a manner to be in
contact with the boiled sample liquid; a conduction current
detecting circuit having an active circuit element whose input
electrode is connected to a bias power source including the
second-mentioned vessel, the boiled sample liquid poured into this
vessel, the needle-like electrode and a first D.C. power source and
whose output electrode is connected via an excitation coil with a
core to the first D.C. source; a rotatable metal piece of a
magnetic conductive material provided in proximity to the core of
the conduction current detecting circuit and adapted to be
electromagnetically attracted with its one end as a fulcrum when
the conduction current detecting circuit is actuated; a temperature
indicating meter continuously indicating the temperature variation
of the sample liquid within the first mentioned vessel and
constituting a bridge circuit constructed of three resistors and a
heat responsive resistance element partly received in the
first-mentioned vessel in a manner to be dipped in the sample
liquid, a second D.C. power source connected acorss the paired
input terminals of the bridge circuit and a temperature indicating
meter consisting of a conventional D.C. galvanometer connected
across the paired output terminals of the bridge circuit; and means
for locking the deflection of the pointer of the temperature
indicating meter by the metal piece at the moment the metal piece
is attracted to the core of the conduction current detecting
circuit.
According to the liquid quality evaluating apparatus so constructed
the temperature indicating meter can continuously detect the
temperature variation of the sample liquid within the
first-mentioned vessel which is heated by the heating source, and
is adapted to lock the deflection of the temperature indicating
meter pointer in a position representative of a boiling point of
the sample liquid at the moment it is boiled. Therefore, if the
boiling temperature range of a fresh reference liquid the same as
the sample liquid is preliminarily known, a temperature indicated
by the locked pointer on the temperature indicating meter makes the
ready evaluation of the quality of the sample liquid according to
whether said indicated temperature falls within the preset boiling
temperature range of the reference liquid.
A liquid quality evaluation apparatus according to another
embodiment of this invention uses, in place of the metal piece of
the first embodiment of this invention, a first normally closed
contact and first normally open circuit both driven by the
excitation coil included in the conduction current detecting
circuit. There is also used, in place of a temperature indicating
meter as shown in the first embodiment of this invention, a liquid
temperature detecting circuit consisting of means for detecting the
variation of the resistance of the heat sensitive resistance
element as the variation of an amount of electric current, a D.C.
amplifier for amplifying the variation of the amount of electric
current so detected by said means, a Schmidt circuit connected to
the D.C. amplifier, and an excitation circuit coupled to the
Schmidt circuit and having an excitation coil connected between the
output terminal thereof and a D.C. source so as to drive a second
normally open contact and second normally closed contact. A first
series circuit consisting of the first normally closed contact, the
second normally opened circuit and a first lamp and a second series
circuit consisting of the first normally open contact, the second
normally closed contact and a second lamp are connected in parallel
between both the terminals of the D.C. power source. With the
liquid quality evaluating apparatus so constructed, when the
conduction current detecting circuit is rendered conductive earlier
than the liquid temperature detecting circuit, the second lamp is
lighted earlier than the first lamp. On the contrary, when the
liquid temperature detecting circuit is rendered conductive earlier
than the conduction current detecting circuit, the first lamp is
lighted earlier than the second lamp. A liquid, in general,
exhibits the property that when any inpurity is contained therein
its boiling point is raised or dropped with an increase of the
impurity content.
Therefore, if a threshold voltage level of the Schmidt circuit in
the liquid temperature detecting circuit is preset at the level
representative of a temperature corresponding to a temperature
immediately below a lower boiling point limit of a fresh reference
liquid the same as the sample liquid i.e. a reference liquid whose
impurity content is below a predetermined value, or at the level
representative of a temperature corresponding to a temperature
immediately above a upper boiling point limit thereof, then whether
the sample liquid is good or bad can be determined by knowing which
of the first and second lamps is lighted first.
The above-mentioned first and second series circuits can be
replaced by a series circuit of a lamp and a normally open contact
closed by the excitation coil of the conduction current detecting
circuit and a series circuit of a lamp and a normally open contact
closed by the excitation coil of the liquid temperature detecting
circuit.
A liquid quality evaluating apparatus according to further
embodiment of this invention comprises a vessel made of a heat
conductive and electroconductive material into which a suitable
amount of sample liquid is poured; a heating source having a heater
arranged in proximity to the vessel and a power source connected
across the ends of the heater; a needle-like electrode whose one
end is arranged within the vessel in a manner to be in contact with
the sample liquid; a current conduction path consisting of the
needle-like electrode, the sample liquid, the vessel, a D.C. power
source and a resistor; a Schmidt circuit receptive to a voltage
drop appearing across the resistor in the current conduction path
when the sample liquid is heated, through the vessel by the heating
source, to a preset temperature corresponding to a temperature
immediately below the lower boiling point limit of a fresh
reference liquid the same as the sample liquid, or to a temperature
immediately above the upper boiling point limit thereof; and a
counter coupled to the Schmidt circuit.
With the liquid quality evaluating apparatus so constructed, if no
boiling occurs when the sample liquid is heated to the aforesaid
predetermined temperature, the input voltage level of the Schmidt
circuit is substantially constant and the count number of the
counter is 1 or 0. On the other hand, if boiling takes place, the
sample liquid forms bubbles corresponding to the impurity content
therein, and corresponding pulsating signals are applied to the
Schmidt circuit. Therefore, if the threshold voltage of the Schmidt
circuit is so preset that binary coded signals corresponding to the
number of the pulsating signals from the Schmidt circuit are
driven, the number of the binary coded signals are counted by the
counter, and whether the sample liquid is good or bad can be
evaluated according to the number of counts involved.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic block diagram showing one embodiment of a
liquid quality evaluating apparatus according to this
invention;
FIG. 2 is a practical circuit diagram of the conduction current
detecting circuit of FIG. 1;
FIG. 3 is a practical circuit diagram of the liquid temperature
detecting circuit of FIG. 1;
FIG. 4 is a schematic block diagram showing one modification of the
embodiment of FIG. 1;
FIG. 5 is a schematic block diagram showing another embodiment of a
liquid quality evaluating apparatus according to this
invention;
FIG. 6 is an enlarged front view showing the dial plate portion of
a temperature indicating meter of FIG. 5;
FIG. 7 is an enlarged sectional view illustrating a preferred
example of the cover for the heating vessel shown in FIGS. 1, 4 and
5;
FIG. 8 shows a schematic block diagram showing further embodiment
of a liquid quality evaluating apparatus according to this
invention; and
FIGS. 9A and 9B respectively show input and output waveforms of the
Schmidt circuit in FIG. 8.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 is a schematic block diagram of one embodiment of this
invention. In the figure, reference numeral 11 denotes a heating
vessel made of a heat conducting material such as copper, the
vessel 11 having a sufficient capacity to hold about 0.6cc of
liquid and an upper opening measuring about 10mm in diameter and
presenting a substantially U-shaped longitudinal cross section
placed in the heating vessel 11 is about 0.5cc of an automobile
brake fluid 12 to be evaluated. Then, a sealing cover 13 is placed
on the top of the vessel 11. From a side wall of the heating vessel
11, for example, from the lower side wall thereof as shown in the
figure, a nozzle 15 having an inner diameter of about 2mm projects
in an integral fashion. A section of the nozzle is at a higher
level than the upper surface 14 of the brake fluid 12 in the
vessel. At the bottom of the heating vessel a heater 18 is disposed
in series with a temperature adjusting variable resistor 17. The
brake fluid 12 within the heating vessel 11 can thus be heated to
about 100.degree.-300.degree.C by an appropriate power source 16
When the brake fluid 12 within the heating vessel 11 boils, it is
rapidly forced through the open end of the nozzle 15 (due to vapor
pressure of the boiled brake within the sealed vessel 11) into
another vessel 19 made of a electroconductive material such as
brass having substantially the same capacity and configuration as
the heating vessel 11. Within the vessel 19 there is disposed a
needle-like electrode 20 one end of which is permitted to contact
the boiled brake fluid. The other end of the electrode 20 is
connected to a positive terminal 22 of a D.C. power source 21 of
about 12 volts and integrally secured through an insulating
material 23 such as porcelain to the vessel 19, the negative
terminal of the D.C. source 21 being connected to ground. The
positive terminal 22 of the D.C. source 21 is connected to the
vessel 19 through a conduction current detection circuit 25 (as
will be later described with reference to FIG. 2) to the output
terminal of which is connected an excitation coil 24. The
conduction current detecting circuit 25 is normally open circuited,
but when the brake fluid 12 within the heating vessel 11 is boiled
and forced into the vessel 19, a current conduction path is
established with respect to the D.C. power source 22 through the
electrode 20, the boiled brake fluid 12, the vessel 19 and the
conduction current detecting circuit 25, thereby causing excitation
of the coil 23. To electrically detect the temperature variation of
the brake fluid 12 within the heating vessel 11, there is received
in a fluid-tight fashion in the heating vessel 11 a heat responsive
resistance element 26. This could be a metal-coated thermistor one
end of which contacts the brake fluid 12 within the heating vessel.
Connected to the heat responsive resistance element 26 is a liquid
temperature detecting circuit 28, as will later be described with
reference to FIG. 3. The output terminal of circuit 28 is connected
an excitation coil 27. The excitation coil 24 controls the opening
and closing of a second normally open contact Y2 and second
normally closed contact X2. As an electric assembly 29 for
evaluating the quality of the sample brake fluid 12 contained
within the heating vessel 11 there are provided a first series
circuit 291 consisting of the first normally closed contact X1, a
first lamp L1 and the second normally open contact Y2, and a second
series circuit 292 consisting of the first normally open contact
Y1, a second lamp L2 and the second normally closed contact X2.
These series circuits 291 and 292 are connected in parallel between
both the terminals of the D.C. power source 21.
FIG. 2 shows a practical circuit diagram illustrating the
conduction current detection circuit 25 of FIG. 1 consisting of a
Darlington circuit including a transistor TR1 whose base is
connected to the vessel 19 and a transistor TR2 whose base is
connected to the emitter of the transistor TR1. The excitation coil
24 is connected between the collector of the transistor TR2 and the
positive terminal 22 of the D.C. power source 21. The collector of
the transistor TR1 is connected via a resistor R1 to the terminal
22 of the D.C. power source, and the emitter of the transistor TR2
is connected to ground.
FIG. 3 is a practical circuit diagram showing the liquid
temperature detection circuit 28 of FIG. 1 which comprises a
variable current path 32 which is a series circuit consisting of a
resistor R11, the aforesaid heat responsive resistance element 26
and a D.C. power source 31 whose negative pole is connected to
ground. A series circuit 35 consists of a variable resistor VR and
a resistor R12 series connected via a D.C. amplifier 34 between
ground and a common connection 33 of the resistor R11 to the heat
responsive resistance element 26. A Schmidt circuit 37 includes a
transistor TR11 whose base is connected to a common junction 36 of
the variable resistor VR and the resistor R12. The emitter is
connected to ground via a resistor R13 and the collector is
connected via a resistor R14 to the positive terminal 22 of the
D.C. power source 21. A transistor TR12 has its emitter connected
in common to the emitter of the transistor TR11, and the base is
connected via a resistor R15 to the collector of the transistor
TR11 and is connected to ground via a resistor R16 and the
collector is connected via a resistor R17 to the terminal 22 of the
D.C. power source 21. A driver circuit 38 includes a transistor
TR13 whose base is connected via a resistor R18 to the collector of
the transistor TR12; the emitter is directly connected to ground;
and the collector is connected via the excitation coil 27 to the
terminal 22 of the D.C. power source 21.
When the percentage of contained water of an automobile brake fluid
in general is more than 3 percent, its boiling point is
substantially decreased. The results of experiments made by the
inventors reveal that when its boiling point is below about
150.degree.C it is necessary to exchange it for a fresh brake fluid
and that a good brake fluid with a water content of below 3 percent
has a boiling point in the temperature range of about
160.degree.-200.degree.C. The resistance of the heat responsive
resistance element 26 is varied as the sample brake fluid 12 within
the heating vessel 11 is heated by the heater 18. This causes the
electric current flowing from the D.C. power source 31 to the
variable current path 32 to be varied with a corresponding
variation in the input voltage of the D.C. amplifier 34 appearing
across the resistor R11.
Accordingly, the threshold voltage level of the Schmidt circuit 37
is preset, by adjusting the variable resistor VR in the series
circuit 35, at a voltage level representing a boiling point of, for
example, about 150.degree.C at which level it is possible to
evaluate the quality of the brake fluid.
According to the liquid quality evaluating apparatus so
constructed, when the conduction current detection circuit 25 is
rendered conductive before the liquid temperature detection circuit
28, the first normally open contact Y1 is closed before the second
normally open contact Y2. As a result, the second lamp L2 included
in the second series circuit 292 of the liquid quality evaluating
assembly 29 is lighted before the first lamp L1 included in the
first series circuit 291. The sample brake fluid 12 within the
heating vessel 11 is thus proved unfit for further use as brake
fluid and replacement is necessary. On the other hand, when the
liquid temperature detection circuit 28 is rendered conductive
before the conduction current detection circuit 25 the second
normally open contact Y2 is closed before the first normally open
contact Y1 and the first lamp L1 is lighted before the second lamp
L2. This indicates that the sample brake fluid 12 is still
usable.
FIG. 4 is a schematic block diagram showing a further modification
of the embodiment of FIG. 1. This modification is substantially the
same as the embodiment of FIG. 1 except that the first normally
closed contact X1 in the first series circuit 291 and the second
normally closed contact X2 in the second series circuit 292 have
been eliminated. It will be evident that this modified embodiment
can be put to practice in the same way as the embodiment of FIG. 1
with substantially the same result.
FIG. 5 is a schematic block diagram showing another embodiment of a
liquid quality evaluating apparatus according to this
invention.
This embodiment uses, in place of the liquid temperature detection
circuit 28, a liquid temperature detection circuit 281 including a
bridge circuit 42 constituted by the heat responsive resistance
element 26 and three resistors R21, R22 and R23. A D.C. source 41
of about 1.5 volts is connected across one pair of terminals of the
bridge circuit 42; and a temperature indicating meter 43 consisting
of a conventional D.C. galvanometer, such as a movable solenoid
type is connected between the opposite pair of output terminals of
the bridge circuit 42. With the liquid temperature detection
circuit 281 so designed, when the resistors R22 and R23 are preset
to be equal in resistance value to each other and the resistor R21
is preset to be equal in resistance to that of the heat responsive
resistance element 26 under a normal ambient temperature (about
20.degree.-25.degree.C), then no output appears, at that
temperature. When the brake fluid 12 within the heating vessel 11
is gradually heated by the heater 18, the resistance of the heat
responsive resistance element 26 is increased. As a result, a
corresponding output voltage appears between the output terminals
of the bridge circuit 42. The temperature rise of the brake fluid
causes the resistance of the heat responsive resistance element 26
to rise causing the pointer 44 of the temperature indicating meter
43 to be deflected, to represent a temperature variation. Also,
with the embodiment of FIG. 5, in place of the sample liquid
quality evaluating assemblies utilizing two lamps as in FIGS. 1 and
4, an arrangement is used so that when the excitation coil 24 is
actuated, a metal piece 46 made of a magnetic conductive material
whose one end is rotatable around a fulcrum 45 is
electromagnetically attracted to cause the tip of the pointer 44 of
the temperature indicating meter 43 to be locked.
According to the liquid quality evaluating apparatus so designed,
when the pointer 44 is deflected, and locked of a temperature a
position representative at below about 150.degree.C on the
indicating meter 43 as shown in FIG. 6, the brake fluid 12 should
be exchanged. Where the pointer is locked within a boiling
temperature range of about 150.degree.-170.degree.C a warning "ATT"
is the meter indication. When the pointer 44 is locked at a
position of about 170.degree.C, the meter indication is "GOOD". As
a result, it is possible to indicate the quality of the brake fluid
with a high accuracy and with a simpler structure than the
embodiment of FIG. 1.
FIG. 7 show a preferred embodiment of the sealed cover 13 used to
close the heating vessel 11 shown in FIGS. 1, 4 and 5. The seal
covering 131 of this example has a capillary bore 51 of, for
example, about 0.5mm provided substantially at its center. When the
brake fluid 12 within the heating vessel 11 is boiled rapidly
through the nozzle 15 into the vessel 19 due to vapor pressure of
the boiled brake fluid as well as capillary action, the bore of the
seal covering serves to facilitate the passage of a gas or air, but
prevent the passage of fluid therethrough. It is desirable that the
seal covering 131 having the bore 51 be made of a heat insulating
material 52 such as teflon, but it is difficult to provide in
teflon, a bore as small as 0.5mm in diameter and usually 1mm is the
smallest. As shown in the figure however, on the upper portion of
the teflon 52 an auxiliary brass covering 53 is provided having a
bore 512 with a diammeter of about 0.5mm.
FIG. 8 is a schematic block diagram showing a further embodiment of
a liquid quality evaluating apparatus.
With this embodiment use is made of a heating vessel 61 made of an
electric and heat conductive material, such as copper, whose
longitudinal cross section is substantially U-shaped. Disposed
within the vessel 62 is a needle-like electrode 62 one end of which
is spaced apart about 1mm from the inner bottom surface of the
vessel 62. The other end of the electrode 62 is supported, in an
integral fashion through an electrical insulating material 63 such
as porcelain, on the heating vessel 61 and is connected to the
vessel 61 through a resistor R31 and a D.C. power source 64 of
about 6 volts with the polarity indicated. Across the terminals of
the resistor R31 a counter 66 is connected through a Schmidt
circuit 65. Below the heating vessel 61 is a heating source 70
including a heater 67 and a power source 69 connected, through a
temperature adjusting element consisting of a variable resistor 68,
across the terminals of the heater 67. In the figure reference
numeral 71 denotes a coupling capacitor. After the vessel 61 is
heated to the boiling temperature of an automobile brake fluid
having a water content of about 3 percent for example,
150.degree.C, a sample brake fluid 73 of about 0.01-0.03cc is
dropped within the heating vessel 61 by a spout 72 in a manner to
be in contact with the needle-like electrode 62. This establishes a
current conduction path 74 consisting of the heating vessel 61, the
fluid 73, the needle-like electrode 62, the resistor 31 and the
D.C. power source 64. In this case, when the temperature of the
heating vessel 61 is below the boiling point of the brake fluid 73;
the sample brake fluid is not boiled and a constant voltage Vo of
about -6 volts substantially equal to a voltage of the D.C. power
source 64 as shown in FIG. 9A is applied to the Schmidt circuit 65.
When, on the other hand, the temperature of the heating vessel 61
is higher than the boiling point of the sample corresponding to a
water content of more than 3 percent; then, the sample boils, and
bubbles substantially proportional to the water content of the
brake fluid are produced. Then, a corresponding pulsating signals
e1, e2, e3 . . . as shown in FIG. 9A are impressed on the Schmidt
circuit 65 across the terminals of the resistor R31 included in the
current conduction path 74. These pulsating signals are such that
their maximum and minimum values are varied within the range of the
positive voltage (0 volt) and the negative voltage (-6 volts) of
the D.C. power source 64. Therefore, if the threshold voltage level
S of the Schmidt circuit 65 is preset to a voltage level (the
result of experiments has revealed that about - 2 to -3 volts are
suitable) capable of individually detecting each of the pulsating
signals e1, e2, e3 . . . , then pulse signals p1, p2, p3 - - -
corresponding to the bubbles produced are driven, as shown in FIG.
9B, from the output terminal of the Schmidt circuit 65. The number
of pulse signals is counted by the counter 66. When the count
reaches a predetermined value, for example, 3, then the brake fluid
is evaluated as "bad" and when the count is less than 3, the brake
fluid is evaluated as "good".
It will be understood that the liquid quality evaluating apparatus
according to this invention can be applied not only to an
automobile brake fluid, but also any other liquid whose impurity
content and boiling point can beforehand be obtained, since they
provide a ready evaluation of the quality of the liquid.
While preferred embodiments have been disclosed herein, applicants
claim the benefit of a full range of equivalents within the scope
of the appended claims.
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