Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2000-10-31
2001-09-11
Lefkowitz, Edward (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S628000, C250S574000
Reexamination Certificate
active
06288647
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photoelectric smoke detector whose light receiving section receives light which is originated from a light-emitted section and is scattered by smoke flowing into a smoke detection section, thereby detecting occurrence of fire, as well as to a smoke detection section assembly. More particularly, the present invention relates to a photoelectric smoke detector using a hybrid circuit board, which board has mounted thereon an integrated circuit component including a light-receiving element and an amplifier circuit, in conjunction with other circuit components, as well as to a smoke detection section assembly.
2. Description of the Related Art
FIGS. 24 through 27
show a commonly-employed photoelectric smoke detector, wherein
FIG. 24
is a longitudinal cross-sectional view of the smoke detector;
FIG. 25
is a transverse cross-sectional view of the smoke detector;
FIG. 26
is a layout and construction drawing of a smoke detecting section; and
FIG. 27
is a disassembly view of the smoke detector.
As shown in
FIGS. 24 and 25
, a terminal board
203
is housed in an exterior cover
201
, and a shield case
204
is fixedly attached to the interior of the terminal board
203
. A smoke detection section main unit
205
is fitted to the terminal board
203
, and a printed board
208
is provided on the smoke detection section main unit
205
. A plurality of smoke inlets
202
are formed along the circumference of the exterior cover
201
.
A smoke detection section cover
211
is removably attached to the lower surface of the smoke detection section main unit
205
. Smoke inlets
215
are formed in the circumferential wall of the smoke detection section cover
211
. A plurality of labyrinthine members
213
are formed inside the circumferential wall. An insect screen
214
is provided integrally on the smoke-detecting section
211
.
A light-emission element
221
, such as an infrared LED or the like, is housed in a light-emission holder
217
provided on the lower surface of the smoke detection section main unit
205
. A light-receiving holder
216
houses a light-receiving element
220
, such as a photodiode PD or the like. As can be seen from
FIG. 26
, the optical axis of the light-emission element
221
and the optical axis of the light-receiving element
220
are arranged so as to cross each other in the center of a smoke detecting space and at an angle of, for example, 70°. Here, reference numeral
228
designates an infrared LED for test purpose, and
232
designates a plate member having a slit formed therein.
As shown in
FIG. 27
, the above-described smoke detector is built by means of assembling together the terminal board
203
having fitting metal fitting
209
fixed thereon; the shield case
204
; packing
207
, the printed board
208
; the smoke detection section main unit
205
; the smoke detection section cover
211
; and the exterior cover
201
.
In such a commonly employed photoelectric smoke detector, the light-receiving element
220
is housed in the light-receiving holder
216
and is connected to the printed board
208
disposed on the smoke detection section main unit
205
by means of lead wires. When flowing through lead wires, a faint light-receiving signal is prone to external noise. In order to protect the light-receiving signal from external noise, a metal shield cap
227
is provided within the light-receiving holder
216
.
Electric circuit components to be mounted on the printed board
208
are made compact by means of being made in the form of chip components. Further, the number of components is reduced by means of optimization of circuit design. However, there are limitations to further miniaturization of an electric circuit and to a further reduction in the number of electric circuit components.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a photoelectric smoke detector which prevents intrusion of noise by way of lead wires of a light-receiving element and enables a significant reduction in the number of components, as well as a smoke detection section assembly.
It is another object of the present invention to provide a photoelectric smoke detector which enables a significant reduction in the number of assembly steps, as well as a smoke detection section assembly.
To this end, the present invention is embodied by providing the following configurations.
The present invention provides a photoelectric smoke detector including: a smoke detecting section defining a smoke detecting space; a light emission section holder having a light-emission element disposed in the smoke detecting section; and a light receiving section holder having a light-receiving element disposed in the smoke detecting section, wherein the light-receiving element receives light which has been emanated from the light-emission element and is scattered by smoke flowing in the smoke detecting space, thereby detecting occurrence of fire.
In the photoelectric smoke detector according to the present invention, a hybrid circuit boardwhich has an integrated circuit mounted thereon and is housed in the light receiving section holder, the integrated circuit including the light-emission element and at least a received-light signal amplifying circuit, and that the hybrid circuit board is arranged such that the light-receiving surface of the light-receiving element is directed toward the smoke detecting space.
The majority of electric components constituting electrical circuits of a photoelectric smoke detector are mounted on a hybrid circuit board housed in a light-receiving holder. Further, an amplifying circuit and a light-receiving element are integrated into a single piece, and hence substantially no lead wires are present between the light-receiving element and the amplifying circuit, thus preventing thorough influence of extraneous noise.
The light-receiving element and an amplifying circuit thereof are integrated into a single piece, and remaining electric circuit components are mounted on a circuit board as discrete components, thus constituting a hybrid structure. As a result, the number of components is greatly diminished, thereby resulting in a great reduction in the number of assembling steps.
Since the hybrid circuit board is housed within a light receiving section holder situated within a smoke detecting space, a space for housing a circuit board to be provided at an elevated position within the smoke detecting section becomes unnecessary, and the smoke detector can be greatly miniaturized correspondingly.
The majority of electric circuit components of the detector including the integrated circuit are mounted on one surface of the hybrid circuit board. An opening is formed in an area on the hybrid circuit board on which the integrated circuit is to be mounted. The integrated circuit is mounted on the hybrid circuit board such that the light-receiving surface of the light-receiving element is directed toward the remaining surface of the hybrid circuit board by way of the opening.
The surface of the hybrid circuit board opposing the smoke detecting space serves as a surface to be used specifically for mounting a light-receiving element. The other surface of the hybrid circuit board serves as a surface to be used specifically for mounting electric circuit components. As a result, a single circuit board can be used for receiving light as well as for mounting circuit components without involvement of influence, which would otherwise be exerted on each other.
By means of the structure of the hybrid circuit board, only the surface on which electric circuit components are to be mounted is coated without exerting an influence on the surface having the light-receiving element mounted thereon. Therefore, corrosion-resistance of the hybrid circuit board can be improved.
Preferably, a package of the integrated circuit is molded integrally with a condenser lens. Alternatively, a separate condenser lens is attached to a package of the integrated circuit.
Preferably, a pair of pi
Hochiki Corporation
Lefkowitz Edward
Sughrue Mion Zinn Macpeak & Seas, PLLC
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