JPH04108293U - photoelectric smoke detector - Google Patents

Abstract

(57) [Summary] [Purpose] To improve the radio noise resistance performance of photoelectric smoke detectors for light reception detection. [Configuration] A light emitting element 10A and a light receiving element 7A are arranged opposite to each other in a smoke monitoring area S formed in the housing.
This is a photoelectric smoke detector in which a light receiving element detects light scattered by smoke particles emitted from a light receiving element 7A, and the light receiving element 7A is attached to a metal shield frame 24 excluding its light receiving surface 7c.
The structure is such that the metal shield frame 24 is grounded to a circuit board 6A on which the electric circuit of the smoke detector is mounted.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention receives scattered light from smoke particles of light projected from a light emitting element to a smoke monitoring area. The present invention relates to a photoelectric smoke detector that detects fire using an optical element and issues a fire alarm.

0002

[Conventional technology]

In general, this type of photoelectric smoke detector uses a light-receiving element that receives scattered light from smoke particles. Since the output is a weak signal, it is easily affected by external radio noise, and has low radio noise resistance. We need to improve our abilities. Therefore, conventionally, as shown in FIG. The optical system holder 21a holding the 0A and the light receiving element 7A is made of carbon-mixed material. The optical system substrate holder 22a made of shaped material is held, and the substrate holder 22a is rotated. There is one that is connected to the ground of the circuit board 6A and is shielded.

0003

[Problem that the idea aims to solve]

However, in such a smoke detector, the optical system board holder 22a is connected to the circuit board. Since it is only grounded to 6A, it is not a smoke detector as a normal product. The electrical resistance of this entire board holder 22a to the ground is approximately several tens of kilohms. Therefore, it has a sufficient shielding effect against radio noise in the tens of KHz band. This caused problems with light reception and detection. This invention was proposed to solve the above problems, and it is a simple method to receive light. The purpose is to improve radio noise resistance during detection.

0004

[Means to solve the problem]

The photoelectric smoke detector of the present invention proposed to achieve the above purpose has a housing A light-emitting element and a light-receiving element are installed oppositely in the smoke monitoring area formed inside the smoke monitoring area, and the light is projected from the light-emitting element. A photoelectric smoke sensor that uses a light receiving element to detect the scattered light caused by smoke particles. The detector includes a metal shield frame covering the light-receiving element except for the light-receiving surface; The metal shield frame has a structure that is grounded to the circuit board on which the electric circuit of the sensor is mounted. It is built. Further, in the smoke detector proposed in claim 2, a metal seal covering the light receiving element is provided. The frame is made of iron-based material.

[0005]

[Effect]

According to the photoelectric smoke detector of the present invention, the entire portion of the light-receiving element except the light-receiving surface is grounded. Since the shield is covered with a metal shield frame connected to the Can protect from radio noise. Further, according to the photoelectric smoke detector of the present invention proposed in claim 2, the metal Since the field frame is made of iron-based material, it can also block the effects of magnetic fields.

[0006]

【Example】

An embodiment of the present invention will be described below with reference to the accompanying drawings. 1 to 4 show an example of a photoelectric smoke detector. The smoke detector includes an optical system first holder 21 as an optical base and an optical system inside the housing 1A. The system second holder 22 is installed, and the smoke monitoring room 4A is located below it in a labyrinth structure. 1a and cover 1b. Also, on the top side of the first holder 21, there is a circuit board mounted with various circuits necessary for smoke detection. A plate 6A is provided via a metal shield cover 23, and is connected to the light emitting element 10A and the receiver. The optical element 7A is mounted with each lead wire 10b, 7b wired to the circuit board 6A. However, these are held in the first holder 21 as shown in FIG. They are placed opposite each other so that their optical axes intersect with each other and face toward the smoke monitoring room 4A. . Of these, the light receiving element 7A is housed in a metal shield frame 24 as shown in FIG. Then, the other side parts except the light-receiving surface 7c are covered by the metal shield frame 24. has been done. Such a metal shielding frame 24 is designed to handle electric field components in the several tens of KHz band, for example. Iron-based materials are preferably used to simultaneously prevent the effects of magnetic field components, and if necessary, Anti-corrosion treatment such as painting, solder plating, or hole sealing treatment is then applied.

[0007] Further, such a metal shield frame 24 has a shoulder portion 24 that overlaps the first holder 21. a, a ribbon extending from the gap between the first holder 21 and the second holder 22 to the circuit board 6A; The tip portion 24 is soldered to the ground portion 24b and the circuit ground portion of the circuit board 6A. It is equipped with c.

[0008] To assemble the light emitting element 10A and the light receiving element 7A into the smoke detector housing 1A. In this case, first, the metal shield frame 24 is attached to the second optical system holder 22 in advance. the first holder 21 to which the light receiving element 7A and the light emitting element 10A were attached. window holes 21a and 21b formed corresponding to the second holder 22 by fitting the , the light emitting element 10A and the light receiving element 7A are made to protrude, and both are formed in the smoke detection chamber 4A. They are placed in a positional relationship facing each other in the smoke monitoring area S.

[0009] According to such a photoelectric smoke detector, when smoke particles enter the smoke detection chamber 4A, Light emitted from the light emitting element 10A is scattered by smoke particles, and the scattered light is transmitted to the light receiving element 7. By receiving the light at A, a smoke detection signal is output from the circuit board 6A. In addition, in such a smoke detector, the light receiving element 7A is grounded to the circuit board 6A. For example, since the optical system is covered by the iron metal shield frame 24, It also protects against radio noise in the tens of KHz band that cannot be shielded by the holders 21 and 22. It can be expected to have a shielding effect, so it is effective against radio noise in almost the entire frequency band. It can be equipped with a shielding function. In addition, when the metal shield frame 24 is made of iron-based material, the shield is resistant to magnetic field components. There is a cold effect.

0010

[Effect of the idea]

According to the photoelectric smoke detector according to the present invention, a metal shield frame that covers the light receiving element can shield external radio wave noise, which cannot be shielded by other shielding methods. It can demonstrate a shielding effect against radio noise in a high frequency band. In addition, if the metal shield frame is made of iron-based material, it will not be able to withstand magnetic field components. It can exert a considerable shielding effect. The present invention with such a structure can achieve a shielding effect in a simple manner and is easy to assemble. be.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view of a photoelectric smoke detector according to the present invention.

FIG. 2 is a perspective view showing a metal shield frame for a light receiving element shield.

FIG. 3 is a vertical cross-sectional structural diagram showing the photoelectric smoke detector according to the present invention.

FIG. 4 is a sectional view of a main part taken along line XX in FIG. 3;

FIG. 5 is an exploded perspective view showing mounting means for a light receiving element and a light emitting element in a conventional smoke detector.

[Explanation of symbols]

1A...Housing S...Smoke monitoring area 10A...Light emitting element 7A... Light receiving element 7c...its light-receiving surface 24...Metal shield frame

Claims (2)

[Scope of utility model registration request] 1. A photoelectric smoke device in which a light-emitting element and a light-receiving element are arranged opposite to each other in a smoke monitoring area formed in a housing, and the light-receiving element detects light scattered by smoke particles of light projected from the light-emitting element. In the sensor, the light-receiving element is covered with a metal shield frame except for the light-receiving surface, and the metal shield frame is grounded to a circuit board on which the electric circuit of the sensor is mounted. A photoelectric smoke detector characterized by: 2. The photoelectric smoke detector according to claim 1, wherein the metal shield frame is made of an iron-based metal material.