JPS6334520B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a photoelectric smoke detector that detects the presence of smoke by receiving light scattered by smoke particles from a light emitting element by a light receiving element. It is something.

[Background technology]

Conventionally, an optical chamber was formed separately from the electrical circuit storage section, and a shielding box was housed inside the electrical circuit storage section, and the electrical circuit was installed in the shielding box. For this reason, in such conventional technology, it is necessary to provide a space within the housing to accommodate the shield box.
In addition to the problem of inevitably requiring a large amount of space, since the optical chamber is formed separately from the electric circuit section, partition walls and other space are required.
There was also a problem in that the size of the cover surrounding the optical chamber was increased.

[Object of the Invention] It is an object of the present invention to make it possible to reduce the overall size, and in addition, in the second invention, it is possible to obtain good shielding properties in a thinner and smaller product, and prevent malfunctions caused by external noise. It is an object of the present invention to provide a photoelectric smoke detector that does not cause smoke.

[Disclosure of the invention]

An embodiment of the present invention is shown in FIGS. 1 to 3, and 2 in the figures is a casing composed of a body 13 and a cover 14, which are respectively formed of molded products. A printed circuit board 15 with an electric circuit 1 formed therein is installed, and an optical chamber stand 4 made of a black-colored metal plate is disposed within the upper opening 3 of the housing 2. Platform 4 is L
The lower end of the bent leg 4a is fixed to the printed circuit board 15 by soldering. Also, this optical room stand 4
On the upper surface of the holder, the front light plates 11, 11 made of plywood are erected by caulking or other means, and the front light plates 11, 11 are also colored black. In this way, the light emitting element 5 such as an LED and the light receiving element 6 such as an SPD are fixed on the optical chamber stand 4, with the light plates 11 and 11 preventing direct light from entering each other. Input/output lead wires of these light emitting/receiving elements 5, 6 are connected to the aforementioned printed circuit board 15. In the figure, reference numeral 7 denotes a cover with a labyrinth that constitutes a top plate with a labyrinth, and the cross section of the cover with a labyrinth 7 is shown in FIG. The optical chamber 12 shown as the cross-hatched area in FIG. Light emitting/receiving elements 5, 6
The palms and light plates 11, 11 will be stored.
In the figure, reference numeral 8 denotes an insect repellent net formed of a punching board or the like, and the insect repellent net 8 is sandwiched between the lower surface of the upper edge 16 of the labyrinth cover 7 and the upper surface of the peripheral edge 17 of the upper surface opening 3. The insect repellent net 8 is placed around the outer periphery of the labyrinth cover 7, and the lower end of the labyrinth cover 7 is adhesively fixed to the periphery 17 of the upper opening 3 of the casing 2. Further, the labyrinth cover 7 is formed as a two-color molded product, with its upper surface painted in white or another decorative color, and its lower part black. The inner surface of the optical chamber 12 surrounded by the table 4 is entirely black to prevent diffuse reflection of light on the interior wall surface as much as possible. 9 and 10 are shield plates, respectively;
The shield plate 9 is arranged and fixed along the inner surface of the cover 14 of the housing 2, and the shield plate 10 is arranged and fixed along the inner surface of the cover 14 of the housing 2.
The electric circuit 1 on the printed circuit board 15 is surrounded by the shield plates 9 and 10 and the optical chamber stand 4 made of a metal plate. Further, as described above, the optical chamber stand 4 is connected to the ground potential of the electric circuit 1 by soldering the lower end of the L-shaped bent leg 4a to the printed circuit board 15. Similarly, the shield plate 10 on the bottom surface of the body 13 is connected to the ground potential of the electric circuit 1 by soldering its upper bent piece 18 to the printed circuit board 15.
is maintained at ground potential by pressing the lower end of the shield plate 9 against the cut and raised piece 19 of the shield plate 10, and the contact pressure of the shield plate 9 against the cut and raised piece 19 is the same as that of the body. This is obtained by the downward pressing force of the shield plate 9 by the cover 14 when the cover 14 is attached to the cover 13 . Thus, the electric circuit 1 on the printed circuit board 15
The shield plates 9 and 10 surrounding the electrical circuit 1 and the optical chamber stand 4 are all kept at the ground potential of the electrical circuit 1.
This shielding effect can be obtained. In addition, the input and output ends of this electric circuit 1 are electrically connected to a terminal 20 on the lower surface of the body 13 via a feedthrough capacitor 21.
It absorbs the noise superimposed on the wiring from the receiver to the sensor to prevent malfunctions.

〔Effect of the invention〕

As described above, the first aspect of the present invention provides a photoelectric smoke detector that detects smoke by using a light receiving element to receive light scattered by smoke particles of light emitted from a light emitting element. A printed circuit board having an electric circuit is disposed on the bottom of the body, and the housing has an opening on the top surface, and a casing with at least a black top surface is placed in the opening. An optical room stand is arranged, and a light emitting element such as an LED and a light receiving element such as an SPD are placed on this optical room stand so that the optical axis is approximately parallel to the optical room stand, and at least the inner surface of the lower side is A black top plate with a labyrinth is passed through the top opening of the housing to cover the optical chamber stand, and the outer periphery of the top plate with a labyrinth is covered with an insect screen, so that the electrical circuit storage area and the optical Compared to the conventional example where the chamber is partitioned with a partition wall spanning the entire diameter and formed by a molded product,
This has the effect of significantly reducing the external dimensions of the vessel and making it thinner. Furthermore, in the second aspect of the invention, the shield for the electric circuit is provided by a shield plate disposed and fixed along the bottom surface of the body, together with the shield of the black optical chamber part, and a shield plate arranged and fixed along the inner peripheral surface of the cover. Although the provided shield board provides a good shielding effect on the electric circuit and can accurately prevent malfunctions caused by external noise, it is not possible to use a separate shield box inside the housing. Unlike conventional technology in which electrical circuits are formed within this shielded box, the container does not require a large internal space and becomes larger, making it possible to make the container smaller and thinner. have an effect.

[Brief explanation of the drawing]

FIG. 1 is an external front view of an embodiment of the present invention, FIG. 2 is a sectional view of the same, and FIG. 3 is a reduced sectional view taken along line X-X of the same. Top opening, 4 is an optical room table, 5 is a light emitting element, 6 is a light receiving element, 7 is a cover with a labyrinth, 8 is an insect screen, 9,
10 is a shield plate, 11 is a light plate, and 12 is an optical chamber.

Claims (1)

[Scope of Claims] 1. In a photoelectric smoke detector that detects smoke by receiving light scattered by smoke particles of light emitted from a light emitting element with a light receiving element, a housing is formed by fitting a body and a cover. And on the bottom of this body,
In addition to arranging a printed circuit board having an electric circuit, the housing has an opening on the top surface, and an optical room table whose top surface is at least black is placed in this opening, and an LED or the like is mounted on the optical room table. A light emitting element or
A light-receiving element such as an SPD is arranged so that its optical axis is approximately parallel to the optical room stand, and a top plate with a labyrinth whose inner surface on the lower side is black is passed through the upper opening of the housing and covers the optical room stand. A photoelectric smoke detector is characterized in that the outer periphery of the top plate with a labyrinth is covered with an insect repellent net. 2. In a photoelectric smoke detector that detects smoke by receiving scattered light from smoke particles emitted from a light emitting element with a light receiving element, a housing is formed by fitting a body and a cover, and the bottom surface of this body In the department,
In addition to arranging a printed circuit board having an electric circuit, the housing has an opening on the top surface, and an optical room table whose top surface is at least black is placed in this opening, and an LED or the like is mounted on the optical room table. A light emitting element or
A light-receiving element such as an SPD is arranged so that its optical axis is approximately parallel to the optical room stand, and a top plate with a labyrinth whose inner surface on the lower side is black is passed through the upper opening of the housing and covers the optical room stand. The outer periphery of the top plate with a labyrinth is covered with an insect screen, and the shield for the electric circuit is a shield plate arranged and fixed along the bottom surface of the body, together with the shield of the black optical room stand. A photoelectric smoke detector, comprising: and a shield plate disposed along the inner peripheral surface of the cover.