JPH0462118B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an alarm for a fire or theft prevention device, which is equipped with means for preventing contamination of the projecting and receiving sections.

[Prior art]

Conventionally, in a radiation type fire detector installed in a road tunnel, for example, as shown in FIG. A plate 22' was provided. Floating dust collides with and falls on this dust-proof plate 22', thereby preventing the light-receiving window 21' from getting dirty, thereby reducing the number of times of cleaning.

[Problems with conventional technology]

However, in the case where a plate-shaped dustproof plate 22' is provided,
When the airflow 3 overcomes the dustproof plate 22', the downstream side becomes negative pressure and the airflow falls as shown by the arrow 31', so the main flow of the airflow becomes the flow shown by the arrow 32', and the dustproof plate 22' It is possible to prevent dust from adhering to the light receiving window 21' only up to a position slightly higher than the height of the light receiving window 21'. Therefore, in a detector having a wide field of view, the provision of a dustproof plate limits the field of view and sometimes reduces the functionality of the detector.

[Means for solving problems]

In view of the above points of the present invention, V
This is characterized by the provision of a change plate in the shape of an H-shape, an H-shape, or a U-shape.

[Effect]

Due to the above-mentioned characteristic configuration of the alarm device of the present invention, the airflow flowing inside the V-shaped, H-shaped, or U-shaped change plate collides at the tip and overcomes the change plate, and negative pressure is generated on the downstream side. The airflow flowing outside the change plate wraps around and lifts it up, generating an upward air current, so that the light emitting and light receiving parts are protected up to almost twice the height of the change plate.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. Reference numeral 1 is a side wall of a road tunnel, and 2 is a radiation type fire detector equipped with a solar cell, etc., and a light receiving window 21 serving as a light receiving portion thereof is provided so as to protrude from the side wall 1. Reference numeral 22 denotes a V-shaped change plate, and the open end side of the V-shape is arranged on the upstream side with respect to the flow of the light receiving window 21 and the airflow 3 so that an upward airflow is generated so that the airflow does not directly collide with the light receiving window 21. It is provided toward the upstream side of the airflow 3. The airflow 3 is
Wind speed flowing in a certain direction inside the tunnel is 2 to 8 m/s
ventilation flow.

Next, the operation of the change plate 22 will be explained. Ventilation flow 3 flowing from a certain direction along the tunnel side wall 1
In the changing plate 22 provided in the fire detector 2, the airflow is divided into airflows flowing inside and outside the plate wall. When the main airflow containing floating dust flowing inside the change plate 22 crosses over the change plate 22,
Negative pressure is generated on the next side, resulting in a flow as shown by the arrow 31, but the airflow flowing outside the changing plate 22 increases its speed and flows into the negative pressure area from the left and right as shown by the arrow 33, colliding and rising. , the main airflow indicated by the above-mentioned arrow 31 is lifted up, and an upward airflow as indicated by the arrow 32 is generated. In this case, the height is raised to approximately twice the height of the change plate 22.

In FIG. 3, the changing plate 22 is formed into an H-shape, and one U-shaped open end side is a light receiving window 2 as a light receiving part.
1, and the other open end side is provided toward the upstream side of the airflow 3.
The airflow 31 flowing inside the airflow 33 flowing outside
This is similar to the embodiments shown in FIGS. 1 and 2, and an upward air current as shown by the arrow 32 is generated. Further, such an effect similarly occurs when the change plate 22 is formed in a U-shape.

Furthermore, in the above embodiment, a case was described in which the radiation type fire detector is installed in a road tunnel, but other fire alarms equipped with a similar light-receiving part or light-emitting part such as a light-receiving window or a reflector can also be used. Alternatively, the present invention can be implemented in a detector for an anti-theft device, that is, an alarm equipped with an emitting and light-receiving section that is easily contaminated by airborne dust contained in the airflow.

〔effect〕

The alarm of this invention is configured and operates as described above, so when the airflow flowing inside the change plate overcomes the plate at its tip, it generates negative pressure and tries to descend, but the airflow flowing outside the plate Since it wraps around and generates an upward air current, it is possible to obtain an alarm device that protects the projection and light-receiving sections up to almost twice the height of the change plate, and has means for preventing staining of the light-receiving sections.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the alarm device of the present invention installed on the side wall of a road tunnel, FIG. 2 is a perspective view of the alarm device of FIG. 1, and FIG. 3 is a perspective view of another embodiment.
FIG. 4 is a perspective view of a conventional alarm device. 1...Tunnel side wall, 2...Fire detector, 21
...Light receiving window, 22...Change plate, 3...Airflow.

Claims (1)

[Claims] 1. In a radiation or optical alarm for a fire or theft prevention device in which a projecting or receiving part is provided on the ceiling or wall of a building through which airflow flows from a certain direction, A change plate is provided on the upstream side of the airflow of the projector to generate an upward airflow so that the airflow does not directly collide with the projector and receiver. alarm. 2. The changing plate is formed in a V-shape, and is provided with a means for preventing staining of the projecting and light-receiving sections as set forth in claim 1, with the open end thereof facing upstream with respect to the flow of airflow. alarm. 3. A patent in which the change plate is formed in an H-shape, with one U-shaped open end facing the projecting and light receiving sections, and the other U-shaped open end facing the upstream side of the airflow. An alarm device comprising means for preventing contamination of the emitting and light receiving portions as set forth in claim 1. 4. An alarm device equipped with means for preventing staining of the projecting and light receiving sections as set forth in claim 1, wherein the changing plate is formed in a U-shape.