U.S. patent number RE30,323 [Application Number 05/940,156] was granted by the patent office on 1980-07-01 for smoke detector adapted to a smoke sensing apparatus.
This patent grant is currently assigned to Hochiki Kabushiki Kaisha. Invention is credited to Yukio Tomioka.
United States Patent |
RE30,323 |
Tomioka |
July 1, 1980 |
Smoke detector adapted to a smoke sensing apparatus
Abstract
A smoke detector is disclosed which comprises an inner
electrode, an intermediate electrode with a hole for passing
radioactive rays therethrough, an outer electrode having openings
for allowing smoke to flow therethrough, and one radioactive
source, the inner and intermediate electrodes forming an inner
ionization chamber, the intermediate and outer electrodes forming
an outer ionization chamber, the radioactive source being disposed
in the inner ionization chamber. A proper quantity of radioactive
rays from the radioactive source is applied into the outer
ionization chamber through the hole provided in the intermediate
electrode.
Inventors: |
Tomioka; Yukio (Sagamihara,
JP) |
Assignee: |
Hochiki Kabushiki Kaisha
(JP)
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Family
ID: |
27282218 |
Appl.
No.: |
05/940,156 |
Filed: |
September 5, 1978 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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860357 |
Sep 23, 1969 |
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Reissue of: |
440521 |
Jun 18, 1971 |
03935466 |
Jan 27, 1976 |
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Foreign Application Priority Data
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Sep 26, 1968 [JP] |
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43-69696 |
Mar 11, 1969 [JP] |
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44-18458 |
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Current U.S.
Class: |
250/385.1;
250/380; 340/629 |
Current CPC
Class: |
G08B
17/113 (20130101) |
Current International
Class: |
G08B
17/113 (20060101); G08B 17/10 (20060101); G01T
001/18 () |
Field of
Search: |
;340/629
;250/385,380 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Dixon; Harold A.
Attorney, Agent or Firm: Haseltine, Lake & Waters
Parent Case Text
RELATED CASE
This application is a continuation of Ser. No. 860,357 filed Sept.
23, 1969, now abandoned.
Claims
I claim:
1. An ionization-type smoke detector .Iadd.having only a single
radioactive source, .Iaddend.comprising: an inner electrode
provided with .[.a.]. .Iadd.said single .Iaddend.radioactive
source; an intermediate electrode having at least one throughhole;
and an outer electrode having openings through which smoke can
enter; .Iadd.an insulating support member supporting said inner
electrode, said intermediate electrode and said outer electrode;
and an annular wall means projecting from said support member at a
position inwardly of the outer circumference of said support
member; .Iaddend.said inner electrode and said intermediate
electrode forming an inner ionization chamber in which said
radiation source is arranged, said intermediate electrode and said
outer electrode forming an outer ionization chamber, said inner
ionization chamber being .[.arranged inside.]. .Iadd.located in a
topmost portion of .Iaddend.said outer ionization chamber
.Iadd.which surrounds the inner ionization chamber, said
intermediate electrode being secured to said annular wall means
such that the surfaces thereof define said inner ionization
chamber.Iaddend., and wherein a necessary quantity of radioactive
rays emitted from said radioactive source is introduced directly
into said outer ionization chamber through said holes.
2. A smoke detector as defined in claim 1, in which said inner
electrode is movable upwardly and downwardly. .[.3. A smoke
detector as defined in claim 1, in which said inner electrode is
movable upwardly and downwardly..]. .[.4. A smoke detector as
defined in claim 1, in which said inner electrode is supported on a
supporting member having an annular projecting wall, and wherein
said intermediate electrode is secured to
said annular projecting wall..]. 5. An ionization-type smoke
detector .Iadd.having only a single radioactive source,
.Iaddend.which comprises: an inner ionization chamber; an outer
ionization chamber within which said inner chamber is
.[.positioned.]. .Iadd.located at a topmost portion
thereof.Iaddend.; an intermediate electrode common to both of said
chambers and forming a boundary therebetween; an inner electrode
positioned within said inner chamber; an outer electrode defining
the outer boundary of said outer chamber and having openings
therein through which smoke can freely pass; .Iadd.an insulating
support member supporting said inner electrode, said intermediate
electrode and said outer electrode; and an annular wall means
projecting from said support member at a position inwardly of the
outer circumference of said support member; .Iaddend.said inner
electrode being provided with .[.a.]. .Iadd.single
.Iaddend.radioactive source positioned within said inner chamber;
.Iadd.said intermediate electrode being secured to said annular
wall means such that the surfaces thereof define said inner
ionization chamber, .Iaddend.said intermediate electrode including
aperture means formed therein .[.for substantially preventing smoke
from entering said inner chamber from said outer chamber and.].
.Iadd.for substantially preventing smoke from entering said inner
chamber from said outer chamber and .Iaddend.for facilitating the
passage of radiation from said inner chamber into said outer
chamber in order to improve the ionization efficiency therein, said
aperture means comprising an unobstructed hole formed through said
intermediate electrode. .[.6. The smoke detector as set forth in
claim 5, further comprising: an insulating support member having an
annular wall projecting therefrom at a position inwardly of the
outer circumference thereof; said intermediate electrode being
secured to said annular wall such that the inner surfaces thereof
define said inner ionization chamber; the portion of said support
member outside said annular wall forming a boundary for said outer
ionization chamber; said outer electrode being secured to the outer
circumference of said
member..]. .Iadd.7. A smoke detector as defined in claim 1, in
which said annular wall means consists of a projecting annular wall
of said support member, the portion of said support member inside
said annular wall forming a boundary for the top of said inner
ionization chamber; the portion of said support member outside said
annular wall forming a boundary for the top of said outer
ionization chamber; said outer electrode being secured to the outer
circumference of said support member. .Iaddend. .Iadd.8. A smoke
detector as defined in claim 1, in which said annular wall means
consists of a side wall of said intermediate electrode; the portion
of said support member inside said side wall forming a boundary for
the top of said inner ionization chamber; the portion of said
support member outside said side wall forming a boundary for the
top of said outer ionization chamber; said outer electrode being
secured to the
outer circumference of said support member. .Iaddend. .Iadd.9. A
smoke detector as defined in claim 5 in which said annular wall
means consists of a projecting annular wall of said support member,
the portion of said support member inside said annular wall forming
a boundary for the top of said inner ionization chamber; the
portion of said support member outside said annular wall forming a
boundary for the top of said outer ionization chamber; said outer
electrode being secured to the outer circumference of said support
member. .Iaddend.
Description
BACKGROUND OF THE INVENTION
The present invention relates to improved smoke detectors adapted
to a smoke sensing apparatus comprising a smoke detector and an
electric indicating or alarm device including a relay such as, for
example, a control electric valve the control electrode of which is
connected to the output terminal of said smoke detector, and more
particularly to smoke detectors in which a kind of radioactive
substance is used in common in two ionization chambers.
Hitherto, as a method of detecting particles contained in any kind
of smoke, it has been well known to utilize ionization of said
particles. For this purpose, a smoke detector provided with two
inner and outer ionization chambers each including a radioactive
substance therein has been generally used, said outer chamber being
denoted as an outer ionization chamber and being provided with a
metal wire net for passing outer gas therethrough, and said inner
chamber being denoted as an inner ionization chamber and being
constructed so that penetration of said outer gas into said inner
ionization chamber is very difficult.
In the conventional smoke detectors as mentioned above, there are
disadvantages such that the detector becomes large in its
structure, very complicated in its construction, and uneconomical
because each of the inner and outer ionization chambers is provided
with a radioactive substance therein, and, furthermore, the
quantity of the radioactive rays is relatively large, thereby
increasing harmful effects on human bodies.
Furthermore, in the conventional smoke detectors as mentioned
above, precise detection at various temperature condition or
precise detection unaffected by variation of the surrounding
temperature is very difficult and simple temperature compensation
or alarming of an emergency temperature itself cannot be attained.
For the purpose of temperature compensation of the smoke detectors,
various compensating circuits utilizing any kind of various
thermistors have been conventionally utilized, but these circuits
are relatively complex and cause expensive structure of the smoke
detector provided with said circuit.
SUMMARY OF THE INVENTION
It is therefore an essential object of the present invention to
provide improved smoke detectors adapted to a smoke sensing
apparatus comprising a smoke detector and an electric indicating or
alarm device the input of which is connected to the output terminal
of said smoke detector, and having no disadvantages of the
conventional smoke detectors mentioned already.
Said object and other objects of the invention have been attained,
according to the invention, by a smoke detector which comprises
outer, inner and intermediate electrodes, said intermediate
electrode forming an inner ionization chamber therein and said
outer and intermediate electrodes forming an outer ionization
chamber therebetween, and comprises a radioactive substance
provided in a position of said inner chamber to cause ionization in
said chambers.
The objects, characteristic features and function of the invention
will be described in detail in conjunction with the accompanying
drawings, in which the same or equivalent members are designated by
the same reference numerals and characters.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic side view, in section, for showing the
principle of an example according to the invention;
FIG. 2 is a sectional side view for showing another example of the
invention, corresponding to FIG. 1;
FIG. 3 is a sectional view for showing a further example of the
invention, corresponding to FIG. 1;
FIG. 4 is graph showing the relation between output voltage
deviation .DELTA.E of the device, as illustrated in FIGS. 1, 2 or
3, and the surrounding temperature;
FIGS. 5 and 6 are schematic side views, partly in section, of other
examples of the invention, respectively; and
FIG. 7 is a plan view showing a part of a modification of the
example illustrated in FIG. 6.
DETAILED DESCRIPTION OF THE INVENTION
One example of the invention as illustrated in FIG. 1 comprises an
insulating support member 4 made of a synthetic resin having a
large electrical resistance, a metal wire net 1 functioning as an
outer electrode, an .[.intermediated.]. .Iadd.intermediate
.Iaddend.electrode 2 supported by a projecting wall 4a of the
member 4, an inner electrode 3 made of a radioactive substance, and
an inner electrode supporting member 5 provided with a washer 6 and
nuts 7, said outer and intermediate electrodes forming an outer
ionization chamber 1a and an inner ionization chamber 2a being
formed at the position inside said intermediate electrode. The
intermediate electrode 2 is provided with at least one small hole A
.[.or a membrane (not shown).]. which is permeable to any
radioactive ray therethrough. The examples of the invention,
including the example of FIG. 1, relate to only the case in which
only one small hole is provided in the intermediate electrode 2.
Furthermore, in the example of FIG. 1, the inner electrode 3 itself
is made of a radioactive substance, but a radioactive substance may
be attached onto a separately provided inner electrode.[., or the
intermediate electrode may be made of a radioactive substance or
may be provided with a radioactive substance attached thereto. Of
course, a radioactive member may be provided at a position in the
outer ionization chamber, with the same effect as the other
cases.].. In the example of FIG. 1, the intermediate electrode is
in the form of a circular plate, but said electrode may be replaced
by a linear element or elements.
The operation of the example of FIG. 1 will now be described
below.
The detector is designed so that when the atmosphere surrounding
the detector is in normal condition, the output voltage E.sub.o
between the intermediate electrode 2 and the outer electrode 1 does
not energize a smoke sensing apparatus which is not shown, said
apparatus comprising a smoke detector to be improved by use with
this invention and an electric indicating or alarm device, the
input of which is connected to output terminals of said smoke
detector. The said indicating or alarm device can be provided with
an electric valve having a control electrode which is energized by
abnormal energy produced in the smoke detector, but since said
indicating or alarm device is ordinarily a conventional one and has
no direct relation to the inventive concept of the invention, a
detailed description of said device is herein omitted. When a fire
breaks out and smoke containing particles therein enters the
ionization chamber 1a through the meshes of the outer electrode 1,
ionized air ions produced by ionization of the air due to the
radioactive substance in the chamber 1a are adsorbed on said smoke
particles thereby to cause recombination of the ions, or these
smoke particles absorb radiation energy of the radioactive
substance so as to disturb the ionization, said adsorption and
absorption being caused by the extremely large dimension of said
smoke particles in comparison with that of the air particles,
whereby the ion current flowing through the ionization chambers is
decreased relative to that in the normal condition, and the
electric potential at the terminal m, that is, the voltage E.sub.o
is remarkably increased. Accordingly, the smoke sensing apparatus
can be made to operate by said increased voltage E.sub.o. The fine
hole A of the intermediate electrode 2 is adapted to disturb
penetration of the smoke particles into the inner ionization
chamber 2a, but to facilitate efficient radiation of radioactive
rays into the ionization chamber 1a. Accordingly, the constructions
of said members can be modified within the concept mentioned above.
In the above case, the voltage-current characteristic of the ion
current is determined depending upon the strength of the
radioactive substance, dimensions and structures of the electrodes
and the like. Furthermore, for the purpose of compensating for the
effects caused by the surrounding conditions such as temperature,
moisture and atmospheric pressure, it is preferable that the outer
ionization chamber directly sensing the smoke has an unsaturated
characteristic with respect to the ion current, and the inner
ionization chamber has a characteristic saturatable at a relatively
low voltage, said inner ionization chamber exhibiting high
resistance to infiltration of the smoke thereinto, but being freely
communicated with the outer air.
The example of FIG. 2 is substantially the same as that shown in
FIG. 1, except that the inner electrode 3 made of a radioactive
substance has a pin-shaped form and projects centrally into a hole
B provided in the intermediate electrode 2, and the projecting wall
4a in FIG. 1 is replaced by a side wall 2b of the intermediate
electrode 2.
The example of FIG. 3 is substantially the same as that of FIG. 2
except for the structure of the intermediate electrode 2.
According to the examples of FIGS. 1, 2 and 3, a radioactive member
is utilized in common for the inner and outer ionization chambers,
and the inner ionization chamber is provided inside the outer
ionization chamber, so that the detector is miniaturized and can be
manufactured at low cost.
In the example as illustrated in FIGS. 1 to 3, operation of the
detector is affected by the surrounding temperature, so that
precise smoke detection at a certain temperature or generation of
an indication or alarm at a particular temperature cannot be
attained unless some temperature compensating method is adopted.
According to the invention, however, the devices as illustrated in
FIGS. 1 to 3 can be effectively modified so as to have none of the
disadvantages mentioned above, for example, by constructing the
intermediate electrode from a material the condition of which is
varied in response to temperature variation, adjusting
automatically the relative distance between the intermediate and
inner electrodes, varying automatically the position of the inner
electrode having the radioactive substance, or adjusting the
distance between the intermediate electrode and outer electrode,
thereby to compensate irregularity of sensitivity with respect to
the surrounding temperature. Furthermore, for the purpose of
operating the smoke detector at a particular temperature, the
detector can be designed so that it may be operated upon deviation
of the distance between the intermediate electrode and the inner
electrode or the outer electrode from a limit value, or it may be
operated when radiation of the radioactive rays into the outer
ionization chamber is cut off at a specific temperature.
In the example of FIG. 1, deviation .DELTA.E.sub.o of the electric
voltage E.sub.o with respect to the surrounding temperature is
shown in FIG. 4. This relation has been experimentally confirmed by
the inventor of the present invention. The deviation .DELTA.E.sub.o
mentioned above can be compensated according to the example
illustrated in FIG. 5, in which the same numerals as those in FIG.
1 designate the same members as those in FIG. 1. However, in the
example of FIG. 5, the intermediate electrode is made of a material
such as, for example, a bimetal the condition or position of which
can be varied in response to temperature variation, and the inner
electrode 3 is provided with a radioactive substance 3a attached
thereto, without itself being made of said substance.
In the example of FIG. 5, if the temperature-responsive property of
the intermediate electrode 2 is selected so that the relative
distance between the intermediate and inner electrodes 2 and 3 may
be automatically adjusted so as to compensate for the variation of
the surrounding temperature, a constant smoke detecting sensitivity
can be always obtained irrespective of the surrounding temperature.
In this case, when the intermediate electrode is moved so as to
decrease the relative distance between the intermediate and inner
electrodes, low temperature compensation is achieved. On the
contrary, when the intermediate electrode is moved so as to
increase the relative distance mentioned above, high temperature
compensation is achieved.
For the sake of operating the detector illustrated in FIG. 5 upon
elevation of the surrounding temperature to a certain temperature,
for instance, 70.degree. C., the intermediate electrode 2 is
designed so that said electrode 2 is moved by a necessary distance
.[.a way.]. .Iadd.away .Iaddend.from the inner electrode 3 in
either an abrupt or gradual manner, thereby to increase the voltage
E.sub.o up to a value sufficient to operate the smoke sensing
apparatus, not shown.
FIG. 6 shows a modification of the example of FIG. 5. In the case
of the example of FIG. 6, the inner electrode 3 is supported on its
support member 5 by means of the thermally responsive element 9 so
as to be moved up and down, said support member 5 being passed
through the insulating member 8 held by the insulating support
member 4. The element 9 is made of, for example, a bimetal and
designed to compensate for the influence caused by variation of the
surrounding temperature. In the example of FIG. 6, an adjusting
screw, not shown, adapted to adjust the .[.sensibility.].
.Iadd.sensitivity .Iaddend.of the element 9 can be provided, or the
end face 5a of the support member 5 and a contact 10 confronting
said end face 5a and supported by an arm 10a can be utilized for
signalling by alarm a specific emergency temperature, for example,
70.degree. C., by inserting said end face 5a and contact 10 in the
circuit of an alarm device of the smoke sensing apparatus, not
shown.
The examples of FIGS. 1 to 3 can be modified so that the detector
may be operated at a specific temperature. For this purpose, for
example, such a mechanism as shown in FIG. 7 is additionally
provided in the detector, said mechanism comprising a bimetal 11
attached at its one end to the intermediate electrode 3 by means of
a support pin 11a and provided at its other end with a shield plate
13. If the bimetal 11 is designed so that when the temperature
becomes a predetermined specific value, said bimetal 11 is turned
in the direction of the arrow so as to shut the hole A of the
intermediate electrode 3, whereby penetration of radioactive rays
into the outer ionization chamber is stopped and the ion current
flowing through said chamber disappears, the voltage E.sub.o shown
in FIG. 1 is abruptly increased at said specific temperature,
thereby to operate a control electric valve, not shown.
* * * * *