TITLE OF THE INVENTION
FIRE DETECTOR
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fire detector such as a flame detector
and a smoke detector.
2. Description of the Related Art
A smoke detector is provided in a fire monitoring area such as a house or
a building. A conventional smoke detector includes a first element substrate
having a light-emitting element and a second element substrate having a
light-receiving element, which are provided inside a casing (also referred to as
an "optical case"). A main substrate including a power supply circuit, a current
control circuit, an MPU, and the like is provided in a case. Electrical
connection for transmission/reception of a signal and power feeding between the
first and second element substrates and the main substrate is made through a
signal line. The signal line connected to the first and second element substrates
passes through a circular hole provided through a peripheral wall of the casing
to extend along an outer surface of the peripheral wall so as to be connected to
the main substrate (for example, see Japanese Patent Application Laid-open No.
2008-082708; hereinafter, referred to as Patent Document 1).
For inspecting and repairing the smoke detector described above, the
first and second element substrates are required to be removed from and

replaced into the casing. The signal line is introduced into the circular hole,
and hence the signal line is required to be disconnected from the first and second
element substrates so as to remove the first and second element substrates from
the casing. Moreover, after the first and second element substrates are replaced
in the casing, the first and second element substrates and the signal line are
required to be connected to each other again. Much efforts are required to
remove the element substrates from the casing and to replace the element
substrates in the casing in the prior art as described above, and hence operating
efficiency is lowered.
Further, in the conventional smoke detector described above, the signal
line is provided from the hole formed through the peripheral wall of the casing
to the main substrate without being shielded. Therefore, a noise component
present inside the casing adversely affects an output of the signal line to result in
malfunction of the smoke detector in some cases.
SUMMARY OF THE INVENTION
In view of the problems described above, the present invention has an
object to provide a fire detector in which an element substrate can be easily
removed from and mounted into an optical case.
In view of the problems described above, the present invention has
another object to provide a fire detector with improved shielding effects for a
signal line so that the signal line is not affected by a noise component.
According to the present invention, a fire detector includes: an optical

case; an element substrate, on which a light-receiving element is mounted, the
element substrate being provided in the optical case; a signal line passing
through an introduction portion of a peripheral wall of the optical case, the
signal line being connected to the element substrate; and an optical cover for
closing an opening of the optical case, in which the signal line is inserted into a
slit in connection with an upper end surface of the introduction portion of the
peripheral wall.
According to the present invention, a fire detector includes: an optical
case; a light-receiving element provided in the optical case; a received-light
amplifying section for amplifying an output signal of the light-receiving
element; and a fire determination section for determining occurrence of a fire
when a detection level obtained by A/D conversion of the amplified output
signal is equal to or higher than a threshold value, in which: a signal line is
connected to an element substrate on which the light-receiving element is
mounted; and the signal line passes through a slit formed through a peripheral
wall of the optical case.
According to the present invention, a fire detector includes: an optical
case whose interior forms a dark box; an air passage constituting a smoke
detection portion, for letting a gas flow into the optical case; a light-emitting
element provided in the optical case; a light-receiving element for receiving
scattered light generated by scattering of light emitted from the light-emitting
element by smoke particles present in the smoke detection portion; a
received-light amplifying circuit for amplifying an output signal of the
light-receiving element; and a fire determination section for determining

occurrence of a fire when a detection level obtained by A/D conversion of the
amplified output signal is equal to or higher than a threshold value, in which: a
signal line is connected to an element substrate on which one of the
light-emitting element and the light-receiving element is mounted; and the signal
line passes through a slit formed through a peripheral wall of the optical case.
According to the present invention, in the fire detector, a light-shielding
wall is provided in a space for housing the signal line in the optical case between
a position at which the element substrate is to be mounted and the slit.
According to the present invention, in the fire detector, the slit obliquely
intersects the peripheral wall.
According to the present invention, a fire detector includes: an optical
case; an element substrate, on which a light-receiving element is mounted, the
element substrate being provided in the optical case; a signal line passing
through an introduction portion of a peripheral wall of the optical case, the
signal line being connected to the element substrate; and an optical cover for
closing an opening of the optical case, in which: an outer surface of the optical
case and an outer surface of the optical cover have conductivity; and the signal
line is held in contact with an outer surface of a peripheral wall by a signal-line
retaining portion.
According to the present invention, a fire detector includes: an optical
case; a light-receiving element provided in the optical case; a received-light
amplifying section for amplifying an output signal of the light-receiving
element; and a fire determination section for determining occurrence of a fire
when a detection level obtained by A/D conversion of the amplified output

signal is equal to or higher than a threshold value, in which: an outer surface of
the optical case has conductivity; and a signal-line retaining portion for bringing
a signal line connected to an element substrate, on which the light-receiving
element is mounted, into contact with the outer surface is provided to the optical
case.
According to the present invention, a fire detector includes: an optical
case whose interior forms a dark box; an air passage constituting a smoke
detection portion, for letting a gas flow into the optical case; a light-emitting
element provided in the optical case; a light-receiving element for receiving
scattered light generated by scattering of light emitted from the light-emitting
element by smoke particles present in the smoke detection portion; a
received-light amplifying circuit for amplifying an output signal of the
light-receiving element; and a fire determination section for determining
occurrence of a fire when a detection level obtained by A/D conversion of the
amplified output signal is equal to or higher than a threshold value, in which: an
outer surface of the optical case has conductivity; and a signal-line retaining
portion for bringing a signal line connected to an element substrate, on which
the light-receiving element is mounted, into contact with the outer surface is
provided to the optical case.
According to the present invention, in the fire detector, the signal-line
retaining portion is provided to an optical cover mounted onto the optical case.
The present invention has the structure as described above, and hence the
signal line connected to the element substrate externally extends while being
held in the slit provided through the peripheral wall of the optical case.

Therefore, the effort of disconnecting the signal line from and reconnecting the
signal line to the element substrate can be saved.
Moreover, the light-shielding wall is provided at the position between
the position where the element substrate is to be mounted and the slit, and hence
the light-receiving element is not adversely affected even if outside light enters
the optical case through the slit.
The present invention has the structure as described above, and hence the
signal line can be reliably shielded. Thus, the signal line is not affected by the
noise component present in the optical case. Accordingly, in contrast to the
prior art, the occurrence of malfunction due to the noise component can be
prevented according to the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIG. 1 is a plan view illustrating a first embodiment of the present
invention, which shows the schema of a smoke detector;
FIG. 2 is a perspective view illustrating a smoke detection unit;
FIG. 3 is a plan view of an optical case;
FIG. 4 is a bottom view of an optical cover;
FIG. 5 is a plan view of the smoke detection unit;
FIG. 6 is a sectional view taken along the line VI-VI of FIG. 5; and
FIG. 7 is a side view of the smoke detection unit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A smoke detector according to a first embodiment of the present
invention is described referring to FIGS. 1 to 7.
The smoke detector 1 includes: a smoke detection unit 2; an optical case
21 of the smoke detection unit 2; a fan 3; and a filter 5. The interior of the
optical case 21 forms a dark box. The fan 3 sends the air, which is to be
detected, to a smoke detection portion 25 provided in the optical case 21 through
a pipe 4. The filter 5 is provided to the pipe 4.
A light-emitting element 11 is provided inside the optical case 21. The
light-emitting element 11 is, for example, an element which emits an infrared ray.
A light-receiving element 12 such as a photodiode receives scattered light
generated by scattering of the light emitted from the light-emitting element 11
by smoke particles present in the smoke detection portion 25. The
light-receiving element 12 is provided at a position onto which the light emitted
from the light-emitting element 11 is not directly incident. A power source
section 14 feeds electric power to the fan 3 and an airflow sensor 13 for
measuring an airflow quantity. A fire determination section 15 is also
provided.
Although not shown in detail, the fire determination section 15 includes:
an amplifier circuit for amplifying an output signal S of the light-receiving
element 12; an A/D converter for converting the amplified output signal to a
detection level; a comparator circuit for determining the occurrence of a fire
when the detection level becomes equal to or higher than a preset threshold

value, and the like. Collective control of the fire determination section 15 is
performed by a CPU.
The smoke detection unit 2 includes the box-like optical case 21. An
opening of the optical case 21 is closed by an optical cover 30. Although an
outer surface of the optical case 21 has conductivity because the outer surface of
the optical case 21 is subjected to a conductive treatment (such as coating or
vapor deposition) so as to block an electromagnetic wave from entering the
smoke detection unit 2 from the exterior, the optical case 21 may be formed of
an electrically conductive resin instead of the implementation of the conductive
treatment. The inner side of the optical case 21 is, for example, mat black, and
the interior thereof forms the so-called dark box. A stray-light portion 22 is
provided in the optical case 21 so as to be opposed to the light-emitting element
11.
A collective lens 24 collects the light emitted from the light-emitting
element 11 on a curved portion of a light trap 23 provided in the stray-light
portion 22. The smoke detection portion 25 allows the air to pass therethrough.
Apertures 26 are provided at appropriate intervals.
The light-receiving element 12 is mounted on an element substrate 31
along with a circuit component 32. Right and left ends of the element substrate
31 are fitted into grooves 33 so as to be supported thereby. The grooves 33 are
concave portions formed on an inner side of a peripheral wall 21a of the optical
case 21 so as to vertically extend. Therefore, the element substrate 31 is
allowed to be easily inserted and mounted into and removed from the optical
case 21 by vertically reciprocating the element substrate 31.

A signal line 35 is connected to the element substrate 31. The signal
line 35 is, for example, a band-like flat cable, and is used for the
transmission/reception of a signal, power feeding, and the like between the
element substrate 31 and a control board (not shown). The signal line 35 exit
the optical case 21 through a slit 37 so as to extend along an outer surface of the
peripheral wall 21a of the optical case 21.
The slit 37 is formed so as to obliquely intersect the peripheral wall 21a.
In this manner, the signal line 35 is bent so as to more easily extend along the
outer surface of the peripheral wall 21a and outside light is less likely to enter
the optical case 21, as compared with the case where the slit is provided so as to
orthogonally intersect the peripheral wall. Further, the signal line 35 is lightly
held in the slit 37, and hence a part of the signal line 25, which is located inside
the optical case 21, is not affected even if the signal line 35 is pulled from the
exterior of the optical case 21. Moreover, an opening 37a of the slit 37 is in
connection with (is open on) an upper end surface 21f of the peripheral wall 21a.
In this manner, mere vertical reciprocating movement of the signal line 35
enables the signal line 35 to be placed in and removed from the slit 37.
Therefore, the element substrate 37 can be removed from or inserted and
mounted into the optical case 21 while the signal line 35 is being connected to
the element substrate 31.
A housing section 39 for the signal line is provided between the element
substrate 31 and the slit 37 in the optical case 21. Light-shielding walls 40 are
provided in the housing section 39. The light-shielding walls 40 include
light-shielding walls 40a fixed to the optical case 21 and light-shielding walls

40b fixed to the optical cover 30. As a whole, the light-shielding walls 40 are
provided along a path of the signal line 35 to surround the path of the signal line
35 so that the outside light does not reach the element substrate 31. Further,
the light-shielding walls 40a and 40b are provided so as to be adjacent to each
other to enhance light-shielding effects.
On an opening of the optical case 21, the optical cover 30 is placed so as
to cover the opening. The optical cover 30 is fixed to the optical case 21 by
screws 42. Although an outer surface of the optical cover 30 has conductivity
because the outer surface of the optical cover 30 is subjected to the conductive
treatment (such as coating or vapor deposition) so as to block an electromagnetic
wave from entering the smoke detection unit 2 from the exterior, the optical
cover 30 may be formed of an electrically conductive resin instead of the
implementation of the conductive treatment. On longer-side edges of the
optical cover 30, a plurality of signal-line retaining portions 41 are provided at a
distance from each other. The signal-line retaining portions 41 are
pressure-support members for retaining the band-like signal line 35 so that the
signal line 35 is held in contact with the peripheral wall 21a of the optical case
21. The signal-line retaining portions 41 are plate-like pieces which extend
downward from the longer-side edges of the optical cover 30.
A length of each of the signal-line retaining portions 41 is set so as to be
longer than a band width of the signal line 35, and is set to be, for example,
approximately the same as a length (depth) of the slit 37. Further, a distance
between an inner surface of each of the signal-line retaining portions 41 and the
outer surface of the peripheral wall 21a is set so as to be slightly smaller than a

thickness of the signal line 35 (a length of the signal line 35, which is
perpendicular to the band width). In this manner, the signal-line retaining
portions 41 are capable of supporting the signal line 35 in a pressurized manner.
The number, the band width, and the length of the signal-line retaining portions
41 are appropriately selected as needed. Note that, as in the case of the optical
cover 30, the signal-line retaining portions 41 may be provided with
conductivity.
Note that, mounting bosses for the substrate and board all have a
grounding function and are grounded on vapor-deposited surfaces of the bosses
and a surface of a land on a bottom surface of each of the substrate and board.
Moreover, by providing the bosses for mounting the substrate and board to the
optical case 21 and the optical cover 30, a potential of the optical case 21 and
that of the optical cover 30 can be made equal to each other through the ground
of each of the substrate and board. Therefore, by bringing the signal line 35,
and the outer surface of the optical case 21 and the outer surface of the optical
cover 30 close to each other, an electrostatic capacitance is generated between
the signal line 35 and the outer surfaces of the optical case 21 and the optical
cover 30. As a result, noise resistance is enhanced.
An operation of the smoke detector of this embodiment is now
described.
The outer surface of the optical case 21 and the outer surface of the
optical cover 30 have the conductivity, while the signal line 35 is held in contact
with the peripheral wall 21a of the optical case 21. Thus, the signal line 35 is
in a shielded state. Accordingly, the signal line 35 is not affected by noise

present in the optical case 21, and hence the fire determination section 15 can
make a normal determination. Thus, the malfunction of the fire detector can be
prevented.
For removing the element substrate 31 placed in the smoke detection
unit 2 from the optical case 21, the screws 42 are loosened to detach the optical
cover 30 from the optical case 21. Then, the interior of the optical case 21 is
exposed, whereas the upper ends of the grooves 33 and the upper end (opening
37a) of the slit 37 of the optical case 21 are brought into an open state.
When the element substrate 31 and the signal lines 35, which are placed
in the optical case 21, are pulled up with fingers, the element substrate 31 is
pulled out of the grooves 33 while the signal line 35 is pulled out of the slit 37.
Therefore, the element substrate 31 can be easily removed from the optical case
21 while being connected to the signal line 35.
For mounting the element substrate 31 into the optical case 21, a
mounting operation is performed in reverse order of the above-mentioned
removal operation. Specifically, while the element substrate 31 and the signal
line 35 are in connection with each other, the element substrate 31 is moved
downward so as to be pressed into the groove 33. At the same time, the signal
line 35 is moved downward so as to be pressed into the opening 37a of the slit
37. As a result, the element substrate 31 and the signal line 35 are located at
the respective design positions. In addition, the signal line 35 is lightly held in
the slit 37. At this time, the part of the signal line 35, which is located inside
the optical case 21, is housed along the formed path.
The signal line 35 is led to the predetermined position so as to extend

along the outer surface of the peripheral wall 21a. Thereafter, the optical case
30 is placed on the opening of the optical case 21. After the signal line 35 is
brought into contact with the peripheral wall 21a by the signal-line retaining
portions 41, the optical cover 30 is fixed to the optical case 21 by the screws 42.
At this time, the depth of the slit 37 or a height of a stopper of the optical cover
30 may be set so as to limit the vertical movement of the signal line 35 in the
opening 37a of the slit 37.
A second embodiment of the present invention is now described (not
shown).
The fire detector of the present invention can be applied not only to the
smoke detector but also to a fire detector (for example, a flame detector) which
does not include the light-emitting element.
Specifically, the fire detector according to the second embodiment
includes: a box-like optical case; a light-receiving element provided in the
optical case; a received-light amplifying section for amplifying an output signal
of the light-receiving element; a fire determination section for determining the
occurrence of a fire when a detection level obtained by A/D conversion of the
amplified output signal is equal to or higher than a threshold value; and an
optical cover mounted onto the optical case. The optical case has the outer
surface with conductivity and the signal-line retaining portions for bringing the
signal line connected to the element substrate, on which the light-receiving
element is mounted, into contact with the outer surface.
The signal line is connected to the element substrate on which the
light-receiving element is mounted. The signal line is provided so as to pass

through a slit formed through a peripheral wall of the optical case.
Note that, the optical cover, the optical case, the slit, and the signal-line
retaining portions are the same as those of the first embodiment.

We Claim:
1. Afire detector, comprising:
an optical case;
an element substrate, on which a light-receiving element is mounted, the
element substrate being provided in the optical case;
a signal line passing through an introduction portion of a peripheral wall
of the optical case, the signal line being connected to the element substrate; and
an optical cover for closing an opening of the optical case,
wherein the signal line is inserted into a slit in connection with an upper
end surface of the introduction portion of the peripheral wall.
2. A fire detector, comprising:
an optical case;
a light-receiving element provided in the optical case;
a received-light amplifying section for amplifying an output signal of the
light-receiving element; and
a fire determination section for determining occurrence of a fire when a
detection level obtained by A/D conversion of the amplified output signal is
equal to or higher than a threshold value, wherein:
a signal line is connected to an element substrate on which the
light-receiving element is mounted; and
the signal line passes through a slit formed through a peripheral wall of
the optical case.

3. Afire detector, comprising:
an optical case whose interior forms a dark box;
an air passage constituting a smoke detection portion, for letting a gas
flow into the optical case;
a light-emitting element provided in the optical case;
a light-receiving element for receiving scattered light generated by
scattering of light emitted from the light-emitting element by smoke particles
present in the smoke detection portion;
a received-light amplifying circuit for amplifying an output signal of the
light-receiving element; and
a fire determination section for determining occurrence of a fire when a
detection level obtained by A/D conversion of the amplified output signal is
equal to or higher than a threshold value, wherein:
a signal line is connected to an element substrate on which one of the
light-emitting element and the light-receiving element is mounted; and
the signal line passes through a slit formed through a peripheral wall of
the optical case.
4. A fire detector according to any one of claims 1 to 3, wherein a
light-shielding wall is provided in a space for housing the signal line in the
optical case between a position at which the element substrate is to be mounted
and the slit.

5. A fire detector according to any one of claims 1 to 4, wherein the slit
obliquely intersects the peripheral wall.
6. A fire detector, comprising:
an optical case;
an element substrate, on which a light-receiving element is mounted, the
element substrate being provided in the optical case;
a signal line passing through an introduction portion of a peripheral wall
of the optical case, the signal line being connected to the element substrate; and
an optical cover for closing an opening of the optical case, wherein:
an outer surface of the optical case and an outer surface of the optical
cover have conductivity; and
the signal line is held in contact with an outer surface of a peripheral
wall by a signal-line retaining portion.
7. Afire detector, comprising:
an optical case;
a light-receiving element provided in the optical case;
a received-light amplifying section for amplifying an output signal of the
light-receiving element; and
a fire determination section for determining occurrence of a fire when a
detection level obtained by A/D conversion of the amplified output signal is
equal to or higher than a threshold value, wherein:
an outer surface of the optical case has conductivity; and

a signal-line retaining portion for bringing a signal line connected to an
element substrate, on which the light-receiving element is mounted, into contact
with the outer surface is provided to the optical case.
8. Afire detector, comprising:
an optical case whose interior forms a dark box;
an air passage constituting a smoke detection portion, for letting a gas
flow into the optical case;
a light-emitting element provided in the optical case;
a light-receiving element for receiving scattered light generated by
scattering of light emitted from the light-emitting element by smoke particles
present in the smoke detection portion;
a received-light amplifying circuit for amplifying an output signal of the
light-receiving element; and
a fire determination section for determining occurrence of a fire when a
detection level obtained by A/D conversion of the amplified output signal is
equal to or higher than a threshold value, wherein:
an outer surface of the optical case has conductivity; and
a signal-line retaining portion for bringing a signal line connected to an
element substrate, on which the light-receiving element is mounted, into contact
with the outer surface is provided to the optical case.
9. A fire detector according to any one of claims 6 to 8, wherein the
signal-line retaining portion is provided to an optical cover mounted onto the

optical case.

Provided is a fire detector in which an element substrate can be easily
removed from and mounted into an optical case. The fire detector includes: an
optical case (21); an element substrate (31), on which a light-receiving element
(12) is mounted, the element substrate (31) being provided in the optical case
(21); a signal line (35) passing through an introduction portion of a peripheral
wall (21a) of the optical case (21), the signal line (35) being connected to the
element substrate (31); and an optical cover (30) for closing an opening of the
optical case (21), in which the signal line (35) is inserted into a slit (37) which is
open on an upper end surface (21f) of the introduction portion of the peripheral
wall (21a).