JP3338612B2 - Photoelectric smoke detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a photoelectric smoke detector,
In particular, the present invention relates to a photoelectric smoke detector in which a prism lens is used in a smoke sensing chamber and a light receiving element is surface-mounted on a circuit board, and a smoke detector having other structural features.

[0002]

2. Description of the Related Art In a smoke sensing room, an LED serving as a light emitting element and a prism lens are provided in a pair, and light scattered by smoke is received by the prism lens and collected on a light receiving element surface-mounted on a circuit board. The photoelectric smoke detector is LE
D and the prism lens are sandwiched and fixed between the optical base and the optical chamber holder, and light is projected through the hole of the fitting portion.
The structure is such that scattered light due to smoke entering the smoke sensing chamber is received by the prism lens and received by the light receiving element of the circuit board.

FIGS. 21 to 25 show an example of an optical base 103 and an optical chamber holder 102 provided in a smoke sensing chamber of such a smoke detector.
The ED 100 is housed in the recess 104 of the optical chamber 103, and the prism lens 101 is housed in the recess 105 formed opposite thereto. Scattered light due to the smoke received by the prism lens 101 in the smoke sensing chamber is transmitted to the optical chamber. Light is received by a light receiving element (not shown) such as a photodiode mounted on the circuit board 108 through the opening 106 of the holder 102.

Further, in the smoke detector having such a structure, a labyrinth cylinder having a labyrinth wall formed around it is attached to the optical chamber to form a smoke detection chamber. After being stored in the inner recess, the insect repellent net 302
At this time, the connection pin 109 protruding from the sensor head side is fitted into a hole provided in the circuit board 108 of the smoke sensing chamber to detect the circuit board 108. Connected to the head.

However, in such a structure, the smoke sensing chamber is disassembled and the LED 100 and the prism lens 10 are disassembled.
1 to clean or replace the optical base 103
In this case, there is a problem that the prism lens 101 comes off carelessly and is damaged, and the number of components constituting the optical chamber is large, and the light emitting element Also, since the optical axes of the prism lens and the optical axis of the prism lens face each other in an oblique direction in the optical holder 102, there is a problem that the thinning of the smoke detector is prevented.

Further, in this type of conventional smoke detector, the surface of the sensor head, which is connected to the sensor base, has a clip terminal 201 at an outer recess of the sensor head 200 as shown in FIG. Is provided with a pair of clip springs 203 connected by tapping screws 202.
1, a pair of cutting blades (not shown) provided on the outer recess side of the sensor base are twist-fitted and fixedly connected. Therefore, the sensor head 200 has the clip spring 2
03 and a space for providing the clip terminal 201 are required, and the sensor head 200 itself becomes bulky, so that it cannot be made thinner as a whole, and the structure becomes complicated.

[0007]

SUMMARY OF THE INVENTION The present invention has been proposed to solve the above-mentioned conventional problems.
It is an object of the present invention to provide a smoke detector that does not directly damage the prism lens when the optical chamber is disassembled and cleaned, does not easily fall off, and has a simple assembly structure.

A second object is to provide an inexpensive smoke detector which is small and thin. Furthermore, the third
It is an object of the present invention to provide a smoke detector which can effectively prevent disturbance light from entering a smoke detection room.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention has been proposed. The smoke detector proposed in claim 1 intrudes into a smoke detection chamber by intermittently driving a light emitting element. In a photoelectric smoke detector that detects scattered light due to smoke with a light receiving element and detects a fire, the smoke sensing room has a light emitting unit equipped with a light emitting element such as an LED and a light receiving element surface mounted on a circuit board. An optical base that opposes a light receiving unit that houses a prism lens that focuses scattered light due to smoke, and a labyrinth cylinder that has a labyrinth wall formed around it and has one open side ,
The light receiving part of the optical base forms a fitting hole that penetrates up and down,
In this fitting hole, a prism lens having a grip piece extended is accommodated so as to be insertable and removable, and if the grip lens is taken out with the finger, the prism lens can be replaced without damaging the prism lens. .

[0010] The smoke detector proposed in claim 2 comprises:
The fitting hole of the light receiving portion of the optical base has a structure in which a pair of locking claws for elastically locking a pair of protrusions protruding from the prism lens are provided, and the prism lens is housed from the fitting hole. In the event that it does, there is no backlash and it can be firmly fixed. In the smoke detector proposed in claim 3, the optical base includes a light-emitting unit cover that covers a light-emitting element such as an LED, and a prism accommodating unit that changes a light path to a light-receiving element, and each optical axis is on the same horizontal plane. In addition, they are installed opposite each other at a predetermined angle and have a structure in which a disturbance light shielding column is protruded between the light emitting unit cover and the prism accommodating unit, thereby reducing the height of the smoke detector room and making it thinner. Is being planned.

The smoke detector proposed in claim 4 has an internal connection end protruding from the inner recess of the sensor head and an external connection end protruding from the outer recess of the sensor head. A press-fitting terminal having a press-fitting terminal for connecting the external connection end of the press-fitting terminal to the sensor base, and an outer recess of the sensor head and the sensor base. The inner recess has a structure in which a fitting connection portion is provided, and when the sensor head is connected to the sensor base, the electrical connection can be made separately from the mechanical connection, and further, the sensor head, The sensor base has been made smaller and thinner.

The smoke detector proposed in claim 5 is a bottomed smoke detector without a protective cap, formed by accommodating a labyrinth cylindrical body having a labyrinth peripheral wall constituting a smoke detection chamber together with an insect repellent net. The structure is such that the room protection cage is detachably mounted below the sensor head, thereby reducing the number of parts and providing a smoke detector which is inexpensive to manufacture.

In the smoke detector proposed in claims 6 and 7, a light emitting unit cover covering the light emitting element and a light scattered light by the smoke are focused on the light receiving element on a circuit board having the light emitting element and the light receiving element opposed to each other. Attach an optical base opposite the prism housing part that houses the prism lens to be made, and on this optical base,
In a photoelectric smoke detector having a smoke detection chamber formed by further covering a labyrinth cylinder body with a labyrinth wall formed around the projection, a protrusion is continuously formed in a ring shape around the bottom surface of the optical base. However, by making this protrusion coincide with the notch groove formed in the lower end of the labyrinth wall and fitting it into the groove, even when the smoke sensing chamber is formed, no gap is generated, Is effectively prevented.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a smoke detector A according to the present invention, in which a light emitting unit 51 provided with a light emitting element 1 is mounted on a circuit board 4 on which a light emitting element 1 and a surface-mounted light receiving element 2 are mounted.
The optical chamber 12 constituted by covering the optical base 5 provided with the prism housing 52 is housed in the inner recess 10a of the sensor head 10, and the protective cage 6 housing the labyrinth cylinder 3 is mounted thereon. The state is shown.

In this figure, the smoke sensing chamber S houses a light emitting section 51 provided with an LED 1 and a prism lens 8 for condensing light scattered by smoke toward the light receiving element 2 surface-mounted on the circuit board 4. The optical base 5 opposed to the prism accommodating portion 52 and a plurality of labyrinth wall pieces for allowing the invasion of smoke and preventing the invasion of external light are kept at appropriate intervals. The prism accommodating portion 52 of the optical base 5 is formed with a fitting hole 52c which penetrates up and down, and a grasping piece is formed in the hole 52c. The prism lens 8 having the extension 81 can be inserted and removed.

FIGS. 2 and 3 are explanatory views showing a case where the prism lens 8 is inserted into and removed from the fitting hole 52c of the prism housing portion 52 of the optical base 5. FIG. A fitting hole 52c formed with a pair of engaging claws 52a is formed in the prism housing 52,
Since the prism lens 8 has a pair of projections 82 projecting therefrom, as shown in FIG.
When the user grips 1 with his / her finger and fits it into the fitting hole 52c, as shown in FIG. 3, the prism lens 8 is elastically held without looseness by the pair of engaging claws 52a, so that the smoke sensing chamber is disassembled and cleaned. At times, the prism lens 8 does not accidentally come off the optical base 5 and is not damaged.

FIG. 4 shows a circuit board 4 on which an LED 1 and a light receiving element 2 constituting a light emitting element are mounted.
1 is a lead 2a housed in an LED holder 7 to be described later.
The light receiving element 2 is surface-mounted on the circuit board 4 so as to receive the light collected by the prism lens 8. The optical base 5 is, as shown in FIG.
The light-emitting unit cover 51 is placed on the circuit board 4 on which the above-mentioned LED holder 7 is mounted.
A prism accommodating portion 52 accommodating the prism lens 8;
The respective optical axes are opposed to each other on the same horizontal plane and at a predetermined angle, and a light emitting hole 71 of the LED holder 7 is provided between the light emitting section cover 51 and the prism accommodating section 52.
Further, a disturbance light shielding column 53 that projects light that directly enters the prism accommodating portion 52 is protrudingly provided.

Here, the disturbance light shielding column 53 is used to directly project light from the light emitting section 51 to the prism accommodating section 52 in the smoke sensing chamber S or to form a prism accommodating section for reflected light on the labyrinth wall 31 in the smoke sensing chamber S. 52 is effectively prevented from entering the light. Generally, when the light emitting unit and the light receiving unit are arranged in the smoke sensing chamber S such that the respective optical axes are located on the same horizontal plane, direct projection from the light emitting unit to the light receiving unit is performed by the labyrinth wall. However, when the disturbance light shielding column 53 is provided, it is possible to effectively prevent such disturbance light from entering the light receiving portion. A pair of locking claws 55 are provided on the bottom surface of the optical base 5.
Is fitted into the hole 42 formed corresponding to the circuit board 4, and the optical base 5 is attached to the circuit board 4. In addition,
Numeral 54 denotes an optical trap formed on the bottom surface of the optical base 5 and formed with a plurality of irregularities.

6 to 8 show the structure of the LED holder. This LED holder 7 accommodates and holds the LED 1 mounted as a light emitting element on the circuit board 4 to constitute a detection circuit unit for detecting smoke density together with the light receiving element 2 mounted on the surface and other electronic components 41 and the like. The LED 1 is provided with an insertion opening 7 on the rear surface of the holder body 70.
The LED 2 is inserted from the rear surface into the LED insertion hole portion 70 in which the LED 2 is formed, and emits light from the light emission hole 71 on the front surface.
a is connected to the circuit board 4. Since the holder main body 7 is provided with a leg 74 having a hook-shaped portion 74 and a supporting leg 75, the circuit board 4 is formed by these legs 74, 75.
Easy mounting with support on top.

In the illustrated example, the LED holder 7 has a support leg 75 provided on the holder body 70 inserted into a hole 43 formed on the circuit board 4 and a support leg 73 having a hook-shaped portion 74 formed thereon. By locking to the edge of the circuit board 4,
It is correctly supported and mounted on the circuit board 4. According to such an LED holder 7, there is no need to provide an aperture or a lens in order to make the amount of projection light constant, and the structure is simple.

Further, the LED 1 is not inserted and held between the optical base and the optical chamber holder as in the prior art, but is inserted into an LED insertion hole 70 formed in the holder body 7 to be housed and held, and the LED 1 is mounted on the front surface thereof. Light emission hole 7 formed
Since the structure projects light from the position 1, the projected light does not leak from the fitting portion, the amount of light projected from the light emitting portion does not vary, and disassembly, cleaning, and assembling are simplified. Also, the light emission holes 7
Since 1 is produced with high accuracy at the time of manufacture, there is almost no variation.

In such a smoke detector, when the optical chamber 12 is constructed, as shown in FIG. 5, it is only necessary to cover the optical base 5 on the circuit board 4 on which the LED holder 7 is mounted. The optical chamber holder that has been required conventionally becomes unnecessary. Further, the optical chamber 6 having such a structure is provided with a labyrinth cylindrical body 3 having a plurality of labyrinth walls 31 formed therearound, as shown in FIG.
10 and the smoke sensing chamber S is formed only by covering as shown in FIG. 10, so that the number of parts can be further reduced.

The smoke sensing chamber S thus formed is:
As shown in FIGS. 11 and 12, a connection hole (not shown) of the circuit board 4 housed in the inner recess 10a of the sensor head 10 and attached to the bottom surface of the smoke sensing chamber S at this time, Connection pin 9a formed in inner recess 10a of sensor head 10
And an electrical connection is made. Also, the insect net 62
The protection cage 6 provided with the projection 61 has a projection 61 formed on the periphery thereof.
Over the smoke sensing room S, and the detector head 10
Is fitted to the inner concave portion 10a of the first embodiment.

In the photoelectric smoke detector having such a structure, the light-receiving element 2 receives the scattered light due to the smoke that has entered the smoke detection chamber 9 by simply driving the LED 2 in the smoke detection chamber 9. Although it detects a fire, the optical base 5 has a structure in which the optical axes of the light emitting unit cover 51 and the prism accommodating unit 52 are arranged at a predetermined angle θ on the same horizontal plane. The height of the smoke sensing chamber can be made smaller than that of the above structure, and the sensing head 10 can be made thinner accordingly.

FIGS. 12-13 show the structural features of the electrical connections employed to make the sensor head 10 thinner. FIG. 13 shows the outer recess 10 of the sensor head 10.
FIG. 14 shows the press-fit terminal 9, and FIG. 15 shows the inner recess 11 d of the sensor base 11. From the outer recess 10a of the sensor head 10, an L-shaped section 9b as shown in FIG. 14 is formed at one end, and a small piece 91 formed at the other end with a sawtooth side surface 92 having a small projection 9a; A press-fit terminal 9 having two small press-fit pieces 91, 91 having no protruding piece 9a and a small piece 91 having a sawtooth side surface 92 formed thereon is attached to the small protruding piece 9a.
Is pressed down, the small projection 9a projects from the inner recess of the sensor head 10, and the outer recess 10a of the sensor head
Since the L-shaped bent portion 9b projects from the small protrusion 9a,
The inner connection terminal is directly inserted into the connection hole of the circuit board 4 housed in the inner recess 10a of the sensor head 10, and L
Since the mold bent portion 9b is an external connection terminal connected to the connector 11b of the sensor base 11, when the sensor head 10 is rotated with respect to the sensor base 11, electrical connection is made. . In addition, 11a is a quick connection terminal for connecting a power supply line.

A plurality of projections 10c and 10d are formed in the outer recess 10b of the sensor head 10, and the
A plurality of projections 10c, 1 of the sensor head 10
Since the recesses 11c and 11d corresponding to 0d and recessed grooves (not shown) are formed, the sensor head 10 is
1 and a plurality of protrusions 10c and 10d are fitted into the corresponding recesses, and when twisted, the protrusions 10c and 10d are fitted into the grooves, and the sensor head 10 is attached to the sensing base 11
Is combined with

In such a structure, the electrical connection between the sensor head 10 and the sensor base 11 is made by the press-fit terminal 9 on the sensor head 10 side and the pinch connector 1 on the sensor base 11 side.
1b, the detector head 10 and the sensing base 1
The mechanical coupling with the sensor 1 is performed by the convex portions 10c and 10d provided on the sensor head 10 side and the concave portion 1 provided on the sensor base 11 side.
Since it is formed by the concave grooves 1c and 11d, the weight and thickness can be reduced as compared with the conventional structure in which electrical connection and mechanical coupling are performed by the clip terminal and the cutting blade.

Further, as shown in FIG. 16, a labyrinth cylinder 3 having a labyrinth wall 31 constituting a smoke sensing chamber S.
The bottomed smoke sensing room protection cage 22 without a protection cap, which accommodates together with the insect net 62, is detachably attached below the sensor head 10. Also,
As shown in FIG. 9, the optical base 5 has a ridge 5a continuously formed in a ring shape on the periphery of the bottom surface thereof.
Is inserted into a cut groove 31a provided around the lower end of the labyrinth wall 31. In this combination, as shown in FIG. 17, the cut groove 31a and the ridge 5a are formed in a wedge shape, and as shown in FIG. 18, the cut groove 31b and the ridge 5b are formed in a square shape, and You may make it fit. Due to such a combination of the cut groove and the ridge, no gap is formed on the bottom surface of the smoke sensing chamber S,
There is an advantage that the invasion of light from the outside is prevented and the inflow of smoke is less affected.

FIG. 19 shows the plane arrangement of the light emitting unit and the light receiving unit in the smoke sensing room S.
A light emitting unit cover 51 that houses the light emitting element L and a prism housing unit 52 that houses the prism lens 8 are provided in a pair, and the light emitting unit cover 51 and the prism housing unit 52 have optical axes L1 and L2, respectively. They cross at an angle θ of 130 degrees on the same horizontal plane.

Reference numeral 53 denotes a first disturbance light shielding column, which does not directly enter the light receiving section 2 from the light emitting section 1, but directly reflects the light reflected by the labyrinth wall 31 to the light receiving section 2. The length and the position are defined so as not to make the light enter. FIG. 20 shows the detailed structure of the disturbance light shielding column 3, in which a plurality of thin vertical grooves 53a are formed on the side surface facing the prism housing portion 52 to form an optical trapping surface.
The light hitting the vertical groove 53a has a structure in which reflection is suppressed and absorbed. Such a light trapping surface may be a rough surface having fine uneven surfaces instead of the vertical grooves.

[0031]

According to the photoelectric smoke detector of the present invention, the following effects can be obtained. According to the photoelectric smoke detector of the first aspect, the optical base has a structure in which the prism lens having the extended grip is accommodated in the light receiving portion so as to be insertable and removable, so that the grip is held by a finger. If the prism lens is taken out, it can be replaced without damaging the prism lens.

[0032] The smoke detector proposed in claim 2 comprises:
Since the prism lens inserted into the light receiving portion of the optical base has a structure that is elastically locked by a pair of engaging claws,
The prism lens can be firmly fixed and held without inadvertent falling off and backlash. In the smoke detector proposed in claim 3, the optical base includes a light emitting unit cover for housing a light emitting element such as an LED, and a prism housing for changing the optical path to the light receiving element, and each optical axis is on the same horizontal plane. It has a structure in which a light-shielding column is projected between the light-emitting section cover and the prism accommodating section, and the height of the smoke detector room is reduced to reduce the thickness. I'm trying.

Further, the smoke detector proposed in claim 4 has a structure in which the sensor head and the sensor base are connected by using a press-fit terminal, so that the size of the sensor head and the sensor base can be reduced. And thinning. Further, the sensor head is fixed with a clip terminal, a clip spring, and a tapping screw, and has no structure in which a sensor blade is provided on the sensor base. Therefore, the structure is simple, smart, and the whole can be miniaturized.

[0034] The smoke detector proposed in claim 5 comprises:
The protective cage for accommodating the labyrinth cylindrical body with the labyrinth peripheral wall constituting the smoke sensing chamber together with the insect repellent net is formed in a bottomed cylindrical body without a protective cap, so it can be integrally formed of synthetic resin, and the number of parts can be reduced. It is possible to provide a smoke detector which is reduced in manufacturing cost and inexpensive. In the smoke detector proposed in claims 6 and 7, a ridge is continuously formed in a ring shape around the bottom surface of the optical base, and the ridge is formed at the lower end of the labyrinth wall. Since the structure is such that the smoke sensing chamber is formed, it is possible to effectively prevent intrusion other than disturbance light without forming a gap even when the smoke sensing chamber is formed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional structural view of a photoelectric smoke sensor according to the present invention with a protection cage removed from a sensor head.

FIG. 2 is a longitudinal sectional structural view of a light receiving unit formed on an optical base (showing a state before accommodating a prism lens).

FIG. 3 is a longitudinal sectional structural view (showing a state in which a prism lens is housed) of a light receiving unit formed on an optical base.

FIG. 4 is a perspective view of a circuit board to which an LED holder is attached.

FIG. 5 is an exploded perspective view of the optical chamber.

FIG. 6 is a side view of the LED holder.

FIG. 7 is a front view of the LED holder.

FIG. 8 is a vertical sectional structural view of an LED holder.

FIG. 9 is an exploded perspective view of the smoke sensing chamber.

FIG. 10 is an exploded perspective view of the photoelectric smoke detector of the present invention (the smoke detection chamber is disassembled).

FIG. 11 is an exploded perspective view of the photoelectric smoke detector of the present invention (the smoke detection chamber is not disassembled).

FIG. 12 is a longitudinal sectional structural view of a sensor head of the photoelectric smoke sensor.

FIG. 13 is a structural explanatory view of an outer recess of the sensor head.

FIG. 14 is a diagram illustrating the structure of a press-fit terminal.

FIG. 15 is a structural explanatory view of the inner recess of the sensor base.

FIG. 16 is an explanatory view of a bottomed protection cage integrally formed with a protection cap.

FIG. 17 is an explanatory view of a fitting part for preventing a gap in a labyrinth wall of the smoke sensing chamber.

FIG. 18 is an explanatory view of a gap preventing fitting portion (another example) of a labyrinth wall of a smoke sensing chamber.

FIG. 19 is an explanatory view showing an example of a disturbance light shielding column provided on the optical base.

FIG. 20 is an explanatory diagram showing details of a disturbance light shielding column.

FIG. 21 is an exploded perspective view of an optical chamber in a conventional photoelectric smoke detector.

FIG. 22 is a longitudinal sectional structural view of the same.

FIG. 23 is a plan view of an optical chamber of a conventional photoelectric smoke detector as viewed from a circuit board side.

FIG. 24 is a partially cutaway longitudinal sectional view of an optical chamber in a conventional photoelectric smoke detector.

FIG. 25 is a bottom view thereof.

FIG. 26 is a plan view of a sensor head of a conventional photoelectric smoke sensor.

FIG. 27 is an explanatory view of a conventional photoelectric smoke detector in a state where a detector head and a protection cage are removed.

[Explanation of symbols]

 A photoelectric smoke detector 1 light emitting element (L) 2 light receiving element (PD) 3 labyrinth cylinder 31 labyrinth wall 31a cut groove 4 circuit board 5 optical base 5a ridge 51 light emitting section 52 light receiving section 52a a pair of locking claws 52b locking projection 52c fitting hole 53 disturbance light shielding column 6 protection cage 62 insect repelling net 7 LED holder 8 prism lens 81 gripping piece 82 pair of convex parts 9 press-fit terminal 9a internal connection part 9b external connection part 10 sensor head 11 Detector base 12 Optical room S Smoke detection room

Continuing on the front page (72) Inventor Takeshi Wada 1048 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Works, Ltd. (72) Inventor Hirotaka Hamaguchi 2856 Shiratsuka-cho, Tsu-shi, Mie Prefecture Asahi Denki Kogyo Co., Ltd. (56) Reference Document JP-A-7-121785 (JP, A) JP-A-6-52469 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G08B 17/107

Claims (7)

(57) [Claims] 1. An intermittent driving of a light emitting element,
In a photoelectric smoke detector for detecting a fire by receiving light scattered by smoke entering a smoke sensing chamber with a light receiving element, the smoke sensing chamber includes a light emitting unit provided with a light emitting element such as an LED, and a light emitting surface provided on a circuit board. An optical base that opposes a light receiving unit that houses a prism lens that focuses smoke scattered light toward the mounted light receiving element, and a labyrinth cylinder with a labyrinth wall formed around and an opening on one side In the light receiving portion of the optical base, a photoelectric hole is formed in which a vertically penetrating fitting hole is formed, and a prism lens having a grip is extended in this fitting hole. Smoke detectors. 2. A structure in which a pair of locking claws for elastically locking a pair of projections projecting from the prism lens are formed in a fitting hole of a light receiving section of the optical base. 3. The photoelectric smoke detector according to claim 1. 3. The optical base comprises: a light-emitting unit cover for covering a light-emitting element such as an LED; and an optical prism housing for housing a prism lens for changing a light path in a light-receiving element. And a structure in which a light-shielding column is further provided between the light-emitting portion cover and the optical prism housing portion.
Or the photoelectric smoke detector according to 2. 4. The sensor head has a press-fit terminal having an internal connection end protruding from the inner recess side of the sensor head and an external connection end protruding from the outer recess of the sensor head. A connector for connecting the external connection end of the press-fit terminal to the sensor base, and a fitting connection portion provided in an outer recess of the sensor head and an inner recess of the sensor base. Photoelectric smoke detector with an open structure. 5. A bottomed smoke sensing chamber-protected cage without a protective cap, formed by housing a labyrinth cylindrical body having a labyrinth peripheral wall constituting a smoke sensing chamber together with an insect repellent net,
A photoelectric smoke detector that is detachably mounted in the inner recess of the detector head. 6. A circuit board on which a light emitting element and a light receiving element are mounted, a light emitting unit cover for covering the light emitting element and a prism housing part for housing a prism lens for condensing light scattered by smoke to the light receiving element. In a photoelectric smoke detector having a smoke detection chamber formed by further mounting an optical base and further covering a labyrinth cylinder having a labyrinth wall formed around the optical base, the optical base may be provided around a bottom surface of the optical base. The photoelectric smoke detector has a structure in which a ridge is continuously formed in a ring shape, and the ridge is fitted to a notch groove provided at a lower end of the labyrinth wall and fitted. 7. The photoelectric smoke detector according to claim 6, wherein the cut groove and the ridge are formed in a wedge shape.