JPH01171099A - Moisture-proof structure for ionization type smoke sensor - Google Patents

Abstract

PURPOSE:To reduce the number of parts and assemble processes by pushing and fitting a ring shaped engaging flange part, which is integrally formed in the surrounding of an insulating board, to an engaging channel in a cover side. CONSTITUTION:In covers 1 and 2, an insulating board 14 is provided to mount an internal electrode 17, which equips a radiation source, an intermediate electrode 18 and an external electrode 19, which equips a smoke flowing-in port 3, and in the rear of the insulating board 14, a circuit substrate 25 is received. For the form of the insulating board 14, a ring shaped engaging flange part 15 is integrally formed in the surrounding for the ring shaped engaging flange part 15 of the insulating board 14, a tip is bent and a diameter is enlarged to an external side in a condition before the integration. Then, the ring shaped engaging flange part 15 is narrowed down and pressure-welded into the channel by the pushing to an engaging channel 16 in the covers 1 and 2 sides. Thus, a circuit receiving part can be closed from an external part and since a seal means such as a rubber packing, etc., is not needed, the device can be made compact.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a moisture-proof structure for an ionization type smoke detector that prevents moisture from entering a circuit housing portion.

[Prior Art] Conventionally, as this type of ionization type smoke detector, the one shown in FIG. 11, for example, is known.

In FIG. 11, 1 is a main body cover, 2 is an outer cover, and the outer cover 2 has a smoke inlet 3 formed therein.

Inside the sensor cover, which is composed of a main body cover 1 and an outer cover 2, is provided with an internal electrode 6 equipped with a radiation source 5, an intermediate electrode 8 equipped with a through hole 7, and smoke from the outside, supported by an insulating plate 4. An external electrode 9 into which smoke can flow is incorporated, forming an electrode structure for ionization smoke detection.

A printed circuit board 10 on which a sensor circuit is mounted is housed on the back side of the insulating plate 4, and the housing portion of the printed circuit board 10 is sealed by inserting a rubber packing 11 between the lower insulating plate 4 and a rubber packing 13 for the upper cover 12. It is installed with a seal to prevent moisture and corrosive gases from entering from the outside.

[Problems to be Solved by the Invention] However, in the moisture-proof structure of the circuit housing part in such a conventional ionization type smoke detector, the moisture-proof structure uses rubber gaskets, so the number of parts increases and The assembly work is complicated, and the size of the sensor in the height direction increases due to the inclusion of the gasket, which is a factor that prevents miniaturization of the sensor.

In addition, because relatively large circuit elements such as FETs and capacitors were mounted on the printed circuit board, the circuit storage area became large due to the use of rubber gaskets, which also hindered the miniaturization of the sensor. It had become.

[Means for Solving the Problems] The present invention has been made in view of the problems of the conventional art, and it is possible to make the circuit housing part moisture-proof with a simple structure without using a gasket, and also to reduce the size of the sensor. The purpose of the present invention is to provide a moisture-proof structure for an ionization type smoke detector that can improve the temperature of the smoke sensor.

In order to achieve this object, the present invention provides an insulating plate in the cover, which is equipped with an internal electrode with a small radiation source, an intermediate electrode, and an external electrode with a smoke inlet, and on the back side of the insulating plate. In an ionization type smoke detector having a structure in which a circuit board is housed, the insulating plate has a shape in which a ring-shaped fitting flange is integrally formed around the insulating plate, and the ring-shaped fitting flange of the insulating plate is formed before being assembled. The ring-shaped fitting flange is compressed by pressing into the fitting groove on the cover side, and is pressed into the groove.

[Function] In the moisture-proof structure of the present invention having such a configuration,
The circuit housing can be sealed from the outside by simply pushing the ring-shaped fitting flange formed integrally around the insulating plate into the fitting groove on the cover side, and no sealing means such as rubber gaskets is required. I don't.

[Example] FIG. 1 is a sectional view showing an embodiment of the present invention.

In FIG. 1, 1 is a main body cover, and 2 is an outer cover, each of which is made of synthetic resin, and a smoke inlet 3 is formed around the outer cover 2.

Inside the sensor cover consisting of the main body cover 1 and the outer cover 2 is an insulating plate 14 having a structure shown in FIGS. 2, 3 and 4.
is included. That is, the insulating plate 4 has a shape in which the ring-shaped fitting flange 15 is integrally formed on the outer periphery, and the insulating plate 14
The ring-shaped fitting flange 15 is assembled into the fitting groove 16 of the main body cover 1 under pressure from the outer cover 2 from below.

An internal electrode 17 containing a small amount of radiation source is fitted and fixed in the center of the front side (lower side) of the insulating plate 14 incorporated in the sensor cover, and an intermediate electrode 17 with an opening hole is provided at a position covering the outside of the internal electrode 17. An external electrode 19 is assembled with the electrode 18 and further covers the outside of the intermediate electrode 18 to allow smoke to flow in from the outside.
is attached.

Further, on the back side of the insulating plate 14, an F surrounded by a partition wall 21 is provided.
An ET storage section 22 is integrally formed, and an FET 23 used for a sensor circuit is incorporated in the FET storage section 22.
It is installed in a potting state by pouring hot melt synthetic resin or the like over the outside of the ET22 lead.

Furthermore, in this embodiment, a capacitor storage portion 24 is integrally formed at a predetermined position on the back side of the insulating plate 14.

A printed circuit board 25 is mounted in close contact with the back surface of the insulating plate 14, which serves as a circuit housing section, and a capacitor 26 and FET stored in the capacitor housing section 24 are mounted on the printed circuit board 25.
FET 2 installed in the storage section 22 in a potting state
3 is connected.

Further, a shield plate 27 is incorporated in the upper part of the circuit housing section on the back side of the insulating plate 14 in which the printed circuit board 25 is incorporated.

FIG. 2 shows the insulating plate 14 shown in the embodiment shown in FIG. 1, and FIG. 3 shows a plan view of the back side of FIG.
Further, FIG. 4 shows a plan view of the front side of FIG. 2.

As is clear from FIG. 2, the insulating plate 14 is integrally formed with a ring-shaped fitting flange 15 extending toward the surface side on its outer periphery. It has a molded shape that is bent outward and expanded in diameter. Further, an electrode mounting hole 28 into which the internal electrode 17 is press-fitted is formed in the center of the insulating plate 14, and a concave-convex ring portion 29 is formed on the outside of the electrode mounting hole 28 to ensure creepage distance between the electrodes. A through hole 30 is formed in the concavo-convex ring portion 29 at a position where the electrode lead provided on the intermediate electrode 18 is to be fitted, into which the electrode lead is inserted in close contact with the back side.

Further, on the back side of the insulating member 14, an FET housing part 22 for housing the FET in a potted state is formed surrounded by a partition wall 21, and on the opposite side of the FET housing part 22, a capacitor housing part 24 is formed.

The shapes of the FET accommodating portion 22 and the capacitor accommodating portion 24 will become clearer from FIG. 3, which shows a plan view of the top side of the insulating plate 14.

In FIG. 3, the FET storage section 22 has a substantially oval shape surrounded by a partition wall 21, and an FET insertion hole 31 is provided at the bottom of the FET storage section 22.
A through hole 30 for the electrode lead of the intermediate electrode is opened inside. Of course, an electrode mounting hole 28 for mounting an internal electrode is opened in the center of the insulating plate 14.
A capacitor housing portion 24 is formed on the left side thereof. Furthermore,
A pair of slits 32 for fitting and supporting electrode leads of external electrodes are opened at two symmetrical positions with respect to the center.

On the other hand, the front side (lower side) of the insulating plate 14 shown in FIG. 2 becomes clear from the plan view of FIG. 4. That is, a concave-convex ring portion 29 is formed concentrically around the electrode mounting hole 28 into which the central internal electrode is attached in order to ensure creepage distance, and a position corresponding to the outer diameter of the intermediate electrode in the concave-convex ring portion 29 is formed in a concentric manner. Two fitting holes 33a and 33b, which are open only on the front side, are formed in which the support legs of the intermediate electrode are fitted, and a fitting hole 33C for fitting the electrode lead of the intermediate electrode on the back side is formed. A through hole 30 is opened therein.

The opening hole 34 on the left side of the protrusion corresponding to the capacitor housing 24 serves as a hole for mounting an LED as an alarm indicator from the inside, if necessary.

Next, with reference to FIGS. 5, 6, and 7, the moisture-proof structure of the circuit housing section using the insulating plate 14 will be described in detail.

FIG. 5 is a cross-sectional view of FIG. 1 showing how the insulating plate 14 is incorporated into the sensor cover made up of the main body cover 1 and the outer cover 2, and a part of the electrode structure is omitted.

That is, the insulating plate 14 is assembled by fitting the ring-shaped fitting flange 15 formed on its outer periphery into the fitting groove 16 formed on the main body cover 1 side. A shield case 27 is incorporated into the housing, and the outer cover 2 is attached from below with an external electrode 19 interposed therebetween.

As shown in FIG. 6 before the insulating plate 14 is assembled, the tip of the ring-shaped fitting flange 15 is bent outward and expanded in diameter. 15 into the fitting groove 16 on the main body cover 1 side as shown by the arrow, the ring-shaped fitting flange 15 is inserted as shown in FIG.
is assembled in a state in which it is squeezed inward by pushing into the fitting groove 16, and this ring-shaped fitting flange 1
The tip is pressed against the outer slope of the fitting groove 16 by the reaction force caused by the tightening in step 5, and it is possible to reliably prevent moisture and corrosive gas from entering the circuit housing section located on the back side without using rubber gaskets or the like. can.

FIG. 8 is an enlarged half-sectional view of the FET storage section 22 in the embodiment shown in FIG.

As is clear from FIG. 8, the FET was conventionally mounted on the printed circuit board 25 by potting
FE-1' 23 is incorporated in the FET storage section 22 partitioned by the formation of a partition wall 21 on the back side of the insulating plate 14.
One of the lead terminals is soldered to the electrode lead of the intermediate electrode 18, and another lead is soldered to the printed circuit board 25 provided in close contact with the back side of the insulating plate 18. Soldering of this lead will be done later. The FET housing section 22 is filled with a potting material such as synthetic resin hot melt to provide insulation sealing and to reliably prevent electrostatic damage when touched during assembly.

In addition, the conventional FET potting process was performed on the FET alone as a pre-assembly process, but the insulating plate
By forming the FET accommodating portion 22 in the insulating plate 14, potting can be performed through assembly to the insulating plate 14, and the number of assembly steps can be reduced in this respect as well.

FIG. 9 shows the intermediate electrode 18 shown in the embodiment of FIG. 1, with a plan view shown in the figure (a) and a side view shown in the figure (b).

That is, the intermediate electrode 18 has a ring-shaped electrode shape, and has an electrode piece 18a extending inward to approximately the center, and further has support legs 36a, 36b, and 36c at three locations on the outer periphery of the ring.
are integrally formed in a bent state. Among these support legs 368 to 36c, for example, the support leg 36c has an electrode lead 37 integrally extending therethrough, as is clear from FIG. 9(b). It is pushed out to the back side in order to fit through the through hole 30 of the insulating plate 14 shown and connect to the FET 23. In addition, the support leg portions 36a~
As is clear from FIG. 9(b), sawtooth-like unevenness is formed on the side surface of 36c, so that when it is fitted into insulating plate 14, it is fixed in the center.

FIG. 10 shows the state in which the intermediate electrode 18 is assembled to the insulating plate 14 shown in FIG. Open fitting holes 33a and 33b are formed at two locations, and
A fitting hole 33c with a through hole 3o is formed, and as shown in FIG. The intermediate electrode 18 can be supported on the insulating plate 14 by fitting the fitting leg portion 36c provided with the electrode lead 37 into the through hole 3o of the hole 33c. Incidentally, FIG. 10 is a view taken along the line XX in FIG. 4.

[Effects of the Invention] As explained above, according to the present invention, the insulating plate can be assembled by simply pushing the ring-shaped fitting flange integrally formed around the insulating plate into the fitting groove on the cover side. The circuit storage area formed on the back side can be sealed from the outside, and there is no need for a separate sealing means such as a rubber gasket, which reduces the number of parts and assembly man-hours.Also, the amount of circuit storage that does not use the gasket can be reduced. The dimensions of the section can be reduced.

In addition, since the FET storage section that stores the FETs mounted on the circuit board in a potting state is integrally formed on the back side of the insulating board, the FETs mounted on the circuit board side are
There is no need to secure space to store the ET,
As a result, the circuit board can be mounted in close contact with the back surface of the insulating plate, thereby reducing the height of the circuit housing section.

Furthermore, the insulating plate has a through hole for inserting the electrode lead of the intermediate electrode on the back side and an iK matching hole for supporting the intermediate electrode, making it extremely easy to assemble the intermediate electrode to the insulating plate, making it easy to connect the electrode lead to the insulating plate. Even if it is inserted into the back side, the electrode lead is sealed by potting, so the airtightness of the circuit housing part is not compromised.

By employing these moisture-proof structures, the height dimension of the internal structure of the ionization type smoke detector can be shortened, and the overall size of the sensor can be significantly reduced.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing one embodiment of the present invention; Fig. 2 is a cross-sectional view of the insulating plate shown in Fig. 1; Figures: Figure 4 is a plan view of the front side (bottom side) of Figure 2; Figure 5 is a sectional view showing the insulating plate installed in Figure 1; Figure 6 is the insulating plate installed in Figure 5. Figure 7 is an explanatory diagram showing the previous state; Figure 7 is an explanatory diagram when the insulation board is removed; Figure 8 is an enlarged half-sectional view showing the f=ET storage structure of Figure 1 taken out; Figure 9 1 is an explanatory diagram showing the intermediate electrode taken out from FIG. 1; FIG. 10 is a sectional view showing the structure of the intermediate electrode assembled to an insulating plate; FIG. 11 is an explanatory diagram of a conventional structure. 1: Main body cover 2: Outer cover 3: Smoke inlet 14: Insulating plate 15: Ring-shaped fitting flange 16: Fitting groove 17: Internal electrode 18: Intermediate electrode 19: External electrode 21: Partition wall 22: FET housing section 23: FET 24: Capacitor housing 25 Niblint board 26: Capacitor 27: Shield case 28: Electrode mounting hole 29: Uneven ring part 30: Through hole 32 Nislit 33a to 33C: Fitting hole 34: Through hole (alarm indicator light) ) 368-36C: Support leg 37: Electrode lead

Claims (1)

[Claims] A structure in which an insulating plate is provided inside the cover, and an insulating plate is provided with an internal electrode provided with a radiation source, an intermediate electrode, and an external electrode provided with a smoke inlet, and a circuit board is housed on the back side of the insulating plate. In the ionization type smoke detector, the insulating plate has a shape in which a ring-shaped fitting flange is integrally formed around the insulating plate, and the ring-shaped fitting flange of the insulating plate has its tip facing outward before being assembled. A moisture-proof structure for an ionization type smoke detector, characterized in that the ring-shaped fitting flange is pressed into a fitting groove on the cover side and is pressed into the groove. .