JPH0449749Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a differential spot type fire detector, in particular, a surface heating element is mounted in surface contact with the outer upper surface of the outer periphery of the upper plate of the air chamber. The present invention relates to a differential spot type fire detector configured to heat the air inside the air chamber from the outside of the air chamber.

Fire detector operation tests are conducted periodically to confirm whether the fire detector is always operating normally.

When testing the operation of a differential spot type fire detector that generates an alarm signal when the rate of increase in temperature of the air due to a fire exceeds a certain value, conventionally, for example, a miniature light bulb installed in the air chamber is lit, There is something that heats the air inside the air chamber. However, in this conventional technology, since the heating source is a point, the heating area is small, so it takes time to heat the air in the air chamber, the operation test is also long, and the heating source is connected to the air chamber through an electric circuit. There were problems such as the air chamber being incompletely sealed and errors in the sensitivity set due to leak resistance.

This invention was made by focusing on the problems of the prior art, and it solves the above problems by attaching a surface heating element in surface contact with the outer upper surface of the outer peripheral part of the upper plate of the air chamber. It aims to solve the problem.

This invention will be explained below based on the drawings.

FIG. 1, FIG. 2, and FIG. 3 are diagrams showing an embodiment of this invention.

The air chamber 1 is formed by an air chamber upper plate 3 provided with a leak resistance 2, an air chamber lower plate 4, and a diaphragm 6 attached to the central opening 3A of the air chamber upper plate 3. It is joined to the base 5 and communicates with the outside air through the leak resistance 2. Also, the base 5
A switch 8 is provided corresponding to the center of the diaphragm 6 and connected to terminals 7 at both ends. The expansion of the air in the air chamber 1 pushes up the diaphragm 6, which turns on the switch 8.

A surface heating element 9 is mounted on the upper surface of the outer circumferential portion 3B of the air chamber upper plate 3, which is the outer surface with respect to the air chamber 1. The surface heating element 9 is composed of a heating wire 9A and insulators 9B and 9B' sandwiching the heating wire 9A. An insulator 9 that contacts the outer upper surface of the outer peripheral portion 3B
It is preferable to use a material with good thermal conductivity for B', and to use a material with poor thermal conductivity for the insulator 9B on the opposite side. A lead wire 9C of the surface heating element 9 is connected to a terminal 10 of the base 5.

When a voltage is applied to the heating wire 9A, the surface heating element 9 generates heat and heats the air in the air chamber 1 via the air chamber upper plate 3. The surface heating element 9 has a large heating area because it is a surface as opposed to a point in a conventional miniature light bulb, and therefore the heating time for the air in the air chamber 1 can be shortened. In addition, compared to mounting a light bulb or the like, mounting the surface heating element 9 is easier because it can be done outside the air chamber 1, and it is convenient for inspection and repair of malfunctions. Furthermore, since there is no need to extend the lead wire 9C into the air chamber 1, there is no need for a through hole for the lead wire 9C to be inserted, and the air chamber 1 is sealed better, thereby eliminating errors in sensitivity. .

The surface heating element 9 heats the air chamber 1 from the outside as described above, but since the space between the air chamber 1 and the base 5 is sandwiched between both 1 and 5 and is almost isolated from the outside air, To effectively heat an air chamber 1 without heat escaping.

As explained above, in this invention, a surface heating element is mounted in surface contact with the outer upper surface of the outer periphery of the upper plate of the air chamber, and the air inside the air chamber is drawn from the outside of the air chamber by the surface heating element. By configuring it to heat, the heating area becomes larger, and the heating time for the air in the air chamber can be shortened, as well as the operation test time.The air chamber 1 is also sealed better, reducing errors in sensitivity. The effect is that this will no longer occur.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of this invention, FIG. 2 is a plan view of FIG. 1, and FIG. 3 is a plan view of FIG. 1 with the base removed. 3... Air chamber upper plate, 5... Base, 6... Diaphragm, 8... Switch, 9... Surface heating element.

Claims (1)

[Scope of utility model registration request] In a differential spot type fire detector, a diaphragm attached to the central opening of the upper plate of the air chamber is pushed up by the expansion of the air in the air chamber to turn on a switch attached to the base. A surface heating element is attached to the outer upper surface of the outer periphery of the upper plate in surface contact, and the air within the air chamber is heated from the outside of the air chamber by the surface heating element. Differential spot type fire detector.