Flame detector

Abstract

To provide a flame detector having high durability against an impact test and an overpressure test.SOLUTION: A flame detector includes: a housing constituting an explosion-proof structure incorporating a circuit board 223 in which a circuit having a flame detection function is formed; a plurality of photodetection elements 50A to 50C arranged so as to face an opening 220A provided on a front side of the housing for receiving predetermined wavelength light emitted from a flame; and a detection window 222 provided between the opening and the plurality of photodetection elements. A fixing member constituting an explosion-proof structure is threadably coupled to a wall surface on a front side of the housing thereby the whole edge part is clamped by the wall surface and the fixing member and the detection window is fixed to the housing.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a flame detector that detects flames, and in particular to a technology for improving the durability of protective glass covering a light-receiving window in front of a light-receiving element in a flame detector having a pressure-resistant explosion-proof structure that is installed in a location where flammable gas is likely to fill or accumulate. [Background technology]

[0002] Conventionally, there are pressure-resistant explosion-proof flame detectors that are installed in places where there is a risk of flammable gas filling or accumulating as fire detectors. Flame detectors are equipped with a light receiving element that receives infrared rays from a front opening of a housing to detect flames, and a light receiving window (sensor window) with transparent protective glass is provided in front of the light receiving element (for example, see Patent Document 1). As shown in FIG. 4(A), the flame detector of Patent Document 1 has a detection window (light-transmitting protective glass) 34 provided in the light-receiving window supported by a support member 39 with an L-shaped cross section, and has an adhesive 38 made of silicone rubber, resin, or the like interposed between the peripheral edge of the detection window 34 and the L-shaped support member 39 to provide pressure resistance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-358583 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a pressure-resistant explosion-proof flame detector, the protective glass installed in the light-receiving window is required to be durable against an impact test in which an impact force is applied from the outside to the inside, and an overpressure test in which pressure is applied from the inside to the outside. The flame detector in Patent Document 1 (Fig. 4(A)) has a structure in which the width of the support piece of the L-shaped support member that supports the peripheral part of the protective glass is short, so that the resistance to the impact force in the impact test and the pressure in the overpressure test is mainly dependent on the adhesive strength of the fixing agent. On the other hand, explosion-proof standards have become stricter than those at the time of filing the application for the invention of the above-mentioned Patent Document 1. As a result, it has become clear that there is a problem in that the adhesive strength of the adhesive alone is not enough to withstand the internal pressure in the overpressure test, and the protective glass may float, causing a loss of airtightness.

[0005] Furthermore, the flame detector described in Patent Document 1 discloses a waterproof structure that prevents water from entering the detector from the outside by interposing an O-ring 73 at the joint between a support member 72 that supports the peripheral portion of a detection window (light-transmitting protective glass) 70 and a main body cover 71, as shown in FIG. 4(B). However, the waterproof structure shown in FIG. 4(B) has a problem in that if the performance of the adhesive (such as silicone rubber or resin) 74 between the peripheral edge of the detection window 70 and the L-shaped support member 72 deteriorates, water may seep in through the gap between the window frame on the front side of the housing and the peripheral surface of the detection window (light-transmitting protective glass) 70.

[0006] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a flame detector which is highly durable against impact tests and overpressure tests. Another object of the present invention is to provide a highly airtight flame detector which is free from the risk of water entering through the gap between the window frame on the front side of the housing and the peripheral surface of the detection window (light-transmitting protective glass). [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides: A housing having an explosion-proof structure and a circuit board having a circuit having a flame detection function formed thereon; A plurality of detection light receiving elements are disposed so as to face an opening provided on the front side of the housing and receive light of a predetermined wavelength emitted by a flame; a detection window provided between the opening and the plurality of detection light receiving elements; A flame detector comprising: The detection window is fixed to the housing by a fixing member that constitutes an explosion-proof structure and is connected to the front wall of the housing by a screw, so that the entire edge of the detection window is sandwiched between the wall and the fixing member and fixed to the housing. 、 The fixing member has an inner peripheral surface formed with a flange, When the flange comes into contact with an edge portion of the detection window, the detection window is sandwiched between the wall surface and the fixing member, A rib is formed on the inner end of the flange toward the opening, and the rib is brought into contact with the edge of the detection window. The structure is as follows.

[0008] In a flame detector having the above-mentioned configuration, the edge of the detection window is clamped between the wall surface of the upper case that constitutes the explosion-proof structure and the fixing member, and is fixed to the housing. Therefore, even if an impact force is applied to the detection window from the outside during an impact test, or if the inside of the housing is pressurized during an overpressure test, the detection window will not float, and a pressure-resistant explosion-proof structure that can withstand the force can be realized and durability can be improved. Furthermore, since the only parts of the fixing member that come into contact with the detection window are the ribs, the contact pressure, i.e., fixing force, can be freely set by changing the width of the ribs, making it easy to achieve an optimal fixing force depending on the strength, thickness, etc. of the material (glass) used for the detection window. Here, the "casing constituting the explosion-proof structure" and the "fixing members constituting the explosion-proof structure" are materials that meet the conditions specified in "Part 1 General Provisions" and "Part 2 Pressure-Resistant Explosion-Proof Structure "d"" of the "Guidelines for Explosion-Proof Electrical Equipment in Factory" published as technical guidelines by the National Institute of Occupational Safety and Health, an independent administrative institution. In the examples described below, metal, more specifically stainless steel cast steel, is used. As shown in the "Non-metallic containers and non-metallic parts of containers" of the above guidelines, if the material is not metallic, it may be, for example, sapphire glass, diamond, plastic, or the like, as long as it satisfies the above guidelines.

[0009] Here, preferably, Wall and the detection window, an annular seal material is disposed between the detection window and the detection member. According to this configuration, water that has entered through the detection window can be prevented from entering the housing. Preferably, a cylindrical wall body is provided on the front wall of the housing so as to protrude and surround the opening, and a female screw is formed on an inner peripheral surface of the wall body. The fixing member has an external thread formed on an outer circumferential surface thereof, The fixing member is connected to the wall by screwing the male thread into the female thread, and the flange contacts the edge of the detection window, so that the detection window is clamped between the wall surface and the fixing member. According to this configuration, the fixing member for fixing the detection window to the housing can be easily coupled to the housing, thereby fixing the detection window.

[0010] Furthermore, it is preferable that a rib be formed on the inner end of the flange toward the opening, and that the rib be configured to come into contact with the edge of the detection window. With this configuration, the only part of the fixing member that comes into contact with the detection window is the rib, so the contact pressure, i.e., fixing force, can be freely set by the width of the rib, and the optimal fixing force can be easily achieved depending on the strength, thickness, etc. of the material (glass) used for the detection window.

[0011] Also, preferably, an elastic support is interposed between the peripheral edge of the detection window and the inner peripheral surface of the fixing member and the flange. According to this configuration, since an elastic support is interposed, the elastic support can absorb impacts and prevent damage to the detection window (protective glass), and can also prevent water from entering through gaps in the peripheral surface of the detection window, thereby improving the airtightness of the flame detector.

[0012] moreover the housing is composed of an upper case having the opening on a front side thereof and a lower case coupled to a side of the upper case opposite to the opening, A test hole for applying pressure to the inside of the housing is formed on the rear side of the lower case. It's okay to . With this configuration, a test hole is formed on the rear side of the lower case, so that after assembling the detector, pressure can be applied to the inside of the housing through the test hole to easily perform tests to confirm the waterproof performance.

[0013] moreover ,beforeThe test hole is provided with a plug capable of closing the test hole in a removable manner. It's okay to . With this configuration, a pressure-resistant explosion-proof structure can be achieved by blocking the test hole with a blocking plug, and by removing the blocking plug from the test hole, compression and decompression of the air inside the housing consisting of the main body case (lower case) and the main body cover (upper case) can be avoided when assembling and disassembling the housing, making it easy to assemble and disassemble the housing. Effect of the Invention

[0014] The flame detector according to the present invention can improve durability against impact tests and overpressure tests. The present invention also provides a highly airtight flame detector that is free from the risk of water infiltration through a gap between the window frame of the main body cover and the peripheral surface of the detection window (translucent protective glass). Furthermore, the present invention has the effect of facilitating a test to confirm waterproof performance after assembling the product, and of avoiding compression and decompression of the air present in the housing during assembly and disassembly of the housing, thereby facilitating the assembly and disassembly of the housing. [Brief description of the drawings]

[0015] [Figure 1] 1A and 1B show an embodiment of a flame detector according to the present invention, in which FIG. 1A is a perspective view of the flame detector seen obliquely from above, and FIG. 1B is a perspective view of the flame detector seen obliquely from below. [Diagram 2] FIG. 2 is a cross-sectional view showing an internal structure of the flame detector according to the embodiment. [Diagram 3] FIG. 2 is an enlarged cross-sectional view showing the internal structure of an upper case of the flame detector according to the embodiment. [Figure 4] 1(A) and 1(B) are cross-sectional views showing a support structure for a protective glass provided on a light-receiving window in a conventional flame detector (Patent Document 1). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of a flame detector according to the present invention will be described with reference to the drawings. Fig. 1 is a perspective view of a flame detector 10 according to the present embodiment, and Fig. 2 is a cross-sectional view showing the internal structure thereof. Flame detectors are generally fixedly installed on the wall of a building, either directly or using an angle adjuster as a base, with the back side facing the mounting surface, and detect flames in the area in front of them. Such flame detectors are connected by wiring to a receiver (not shown) that centrally manages multiple flame detectors in the detection area, and when they detect a flame, they send a detection signal to the receiver.

[0017] In the following description, for convenience of explanation, the side that is in front of the flame detector when it is installed on a building is referred to as the upper side, and the rear side is referred to as the lower side. In addition, in the flame detector 10 of this embodiment, as shown in FIG. 2, the detection light receiving elements 50A, 50B, 50C, each of which is composed of three infrared sensors (e.g., pyroelectric elements) having different detection wavelengths, are arranged side by side on the circuit board 223 in the housing 20, and in some cases, the direction in which the detection light receiving elements 50A, 50B, 50C of the flame detector 10 face is referred to as the front side, and the opposite side is referred to as the rear side. In addition to the detection light receiving elements, elements and ICs that constitute a circuit for amplifying signals from these elements and a circuit for determining the presence or absence of a flame are mounted on the circuit board 223.

[0018] As shown in Fig. 1(B), the flame detector 10 of this embodiment includes a housing 20 including a cylindrical upper case 220, a disk-shaped cover plate 210 covering the front side of the upper case 220, and a cylindrical lower case 230 joined to the rear side of the upper case 220 and fixed to an installation location. The upper case 220 and the lower case 230 are made of stainless steel castings, and the cover plate 210 is an aluminum casting that has been anodized so that its surface is black. As shown in Fig. 1(A), the cover plate 210 is joined to the top surface of the upper case 220 by screws 219 inserted through screw insertion holes provided at four locations.

[0019] 1(A), elliptical light receiving windows 210A and 220A are formed in the cover plate 210 and the upper wall 221 of the upper case 220, respectively, and a protective cover 222 made of a light-transmitting material such as sapphire glass is disposed in the light receiving window 220A so as to cover the upper parts of the detection light receiving elements 50A, 50B, and 50C. Note that in this specification, the light-transmitting protective cover 222 disposed in the light receiving window 210A and 220A is referred to as a detection window.

[0020] The lower part of upper case 220 is a dome-shaped cylinder with an outer diameter slightly larger than that of lower case 230, and the upper end part of lower case 230 is inserted into an opening part at the lower part of upper case 220, and the upper end part of lower case 230 is fitted inside upper case 220. As shown in Fig. 1(B), lower case 230 and upper case 220 are connected by a screw 241 inserted into a fixing piece 233a formed so as to protrude laterally from a bottom wall part 233 of lower case 230. In addition, a wing-shaped flange-like mounting base 231 is formed on the underside of the lower case 230, and screw insertion holes 232 are formed in the four corners of the mounting base 231 so that it is configured to be fixed to the installation surface by screws inserted into the screw insertion holes 232.

[0021] FIG. 2 shows a cross-sectional structure of the flame detector 10. As shown in FIG. 2, an oval annular light-emitting member 211 constituting a light-emitting display unit made of transparent resin is disposed between the cover plate 210 and the upper wall 221 of the upper case 220, and the light-emitting member 211 is sandwiched between the lower surface of the inner edge of the cover plate 210 having the light-receiving window portion 210A and the upper surface of the upper wall 221 of the upper case 220. Light emitting member 211 is formed so that the cross section of the annular (ring-shaped) main body is trapezoidal, and a tapered portion located inside the ring is configured to be exposed as a light emitting surface to the inside of light receiving window 210A of cover plate 210. Furthermore, a tapered portion is also formed on the inner edge of light receiving window 220A of upper wall 221 of upper case 220 so as to be continuous with the tapered portion formed on the inside of light emitting member 211.

[0022] Furthermore, light introduction sections are provided on the underside of light emitting member 211 at locations (two locations) facing, for example, red-emitting LEDs mounted on circuit board 223 housed in upper case 220. This allows light introduced from the light introduction sections to be guided while being reflected along annular light emitting member 211 and emitted from the inside of the window, so that light emitting member 211 can be made to shine in a ring shape. At this time, since light emitting member 211 is surrounded by light receiving window section 210A of black cover plate 210, the brightness difference is increased, and the light emitting state of the light emitting display section can be more clearly visually recognized.

[0023] 3, a cylindrical hanging wall 224 that protrudes downward so as to surround light receiving window 220A is formed on the underside of top wall 221 of upper case 220. A female thread is formed on the inner wall surface of hanging wall 224, and cylindrical stainless steel window fixing member 225 with a male thread formed on the outer periphery is screwed into this female thread, whereby window fixing member 225 is attached to the inside of hanging wall 224. Furthermore, the window fixing member 225 has an inner flange 225a formed at the middle position of its inner circumferential surface, and a rib that protrudes slightly upward is provided around the entire periphery of the inner end of the inner flange 225a. An elastic support 226 made of silicone rubber and having an L-shaped cross section is disposed inside this rib so as to contact the upper surface of the inner flange 225a and the inner circumferential surface of the window fixing member 225.

[0024] In addition, a circular detection window 222 is arranged so that its outer peripheral surface is in contact with this elastic support body 226, and the detection window 222 is clamped between the upper wall 221 of the upper case 220 and the window fixing member 225 with the edge of its lower surface in contact with the rib at the end of the inner flange 225a and the edge of its upper surface in contact with the lower surface of the tapered portion of the inner edge of the light receiving window portion 220A of the upper case 220. It should be noted that light receiving window 220A is elliptical, whereas detection window 222 is circular. Therefore, detection window 222 is formed to have a diameter slightly larger than the major axis of elliptical light receiving window 220A of upper case 220. Fig. 3 shows a cross section along the minor axis of light receiving window 220A. In the cross section along the major axis (Fig. 2), the amount of overlap between the edge of light receiving window 220A and the edge of detection window 222 is smaller than in Fig. 3.

[0025] As described above, the detection window 222 is sandwiched between the end of the inner flange 225a of the stainless steel window fixing member 225 and the underside of the upper wall 221 of the upper case 220, which is also made of stainless steel, resulting in a structure that does not rely solely on the adhesive strength of the adhesive (including silicone rubber) for mechanical strength. As a result, the structure can firmly withstand the impact force during impact testing and the pressure during overpressure testing, improving durability. Furthermore, elastic support 226 made of silicone rubber is attached to the periphery of detection window 222, ensuring airtightness inside the housing of the detector. Furthermore, a waterproof O-ring 227 is arranged between the upper edge of the detection window 222 and the lower surface of the upper wall 221 of the upper case 220, so as to prevent water that has entered through the light receiving window portion 220A from entering the housing.

[0026] 2, a cylindrical cable connection part 234 is provided at the bottom of the lower case 230 to which a coupler (connector) 32 at the end of a cable 30 for electrically connecting with a circuit board 223 housed inside the upper case 220 is coupled. Also, on the opposite side of the cable connection part 234, a test hole 235 for introducing compressed air into the inside of the housing 20 when performing an overpressure test, and a blocking plug 236 for blocking the test hole 235 are provided. The blocking plug 236 has a cylindrical part 236a of approximately the same diameter that can be inserted into the test hole 235, and a flange part 236b provided at the end of the cylindrical part 236a, and is fixed to the edge of the test hole 235 by two bolts 237 inserted into screw insertion holes formed in the flange part 236b.

[0027] Furthermore, an O-ring 238 for maintaining airtightness is disposed on the outer periphery of cylindrical portion 236a of blocking plug 236. Also, since blocking plug 236 for blocking test hole 235 is provided, a pressure-resistant explosion-proof structure can be realized by attaching blocking plug 236 to block test hole 235 after testing. Furthermore, by removing the block plug 236 when assembling the upper case 220 and the lower case 230 or disassembling them for inspection, compression and decompression of the air inside the housing can be avoided, making it easier to assemble and disassemble the housing.

[0028] The present invention has been described above based on the embodiment, but the present invention is not limited to the above embodiment and can be modified as appropriate within the scope of the present invention. For example, in the above embodiment, a cylindrical hanging wall 224 is provided on the lower surface of the upper wall 221 of the upper case 220 so as to surround the light receiving window 220A and has a female thread formed on its inner wall surface, and the detection window 222 is sandwiched between the upper wall 221 of the upper case 220 and the flange of the window fixing member 225 by screwing the female thread of the hanging wall 224 to the window fixing member 225 having a male thread formed on the outer periphery and an inner flange. However, the hanging wall 224 may be omitted, and a plurality of screw insertion holes may be provided on the edge of the window fixing member 225, and screw holes may be formed in the corresponding parts of the upper wall 221 of the upper case 220, and the window fixing member 225 may be fixed by screws to sandwich the detection window 222.

[0029] In addition, in the above embodiment, it has been described that sapphire glass is used as the light-transmitting material constituting the detection window 222. However, the light-transmitting material is not limited to sapphire glass, and any material that easily transmits light in the wavelength band of the detection light-receiving element to be used may be used. Furthermore, in the above embodiment, the present invention is described as being applied to a flame detector, but flames may also be detected using ultraviolet light instead of infrared light, and the present invention can also be used in detectors other than flame detectors and in the housings of surveillance cameras. [Explanation of symbols]

[0030] 10 Flame detector 20. Cabinet 30 Cable 32 Coupler 50A, 50B, 50C Light receiving element for detection 210 Cover plate 211 Light emitting member 220 Upper Case 220A Light receiving window (opening) 221 Upper Wall 222 Detection window (protective cover) 223 Circuit Board 224 Hanging wall 225 Window fixing members 226 Elastic support (silicon rubber) 227 O-ring (sealing material) 230 Lower Case 231 Mounting base 232 Screw insertion hole 233 Bottom wall 234 Cable connection part 235 Test hole 236 Obstructive plug

Claims

1. A housing having an explosion-proof structure and a circuit board having a circuit having a flame detection function formed thereon; A plurality of detection light receiving elements are disposed so as to face an opening provided on the front side of the housing and receive light of a predetermined wavelength emitted by a flame; a detection window provided between the opening and the plurality of detection light receiving elements; A flame detector comprising: A fixing member constituting an explosion-proof structure is connected to a front wall surface of the housing by a screw, so that the entire edge of the detection window is sandwiched between the wall surface and the fixing member and fixed to the housing, The fixing member has an inner peripheral surface formed with a flange, When the flange comes into contact with an edge portion of the detection window, the detection window is sandwiched between the wall surface and the fixing member, A flame detector characterized in that a rib is formed on the inner end of the flange toward the opening, and the rib is configured to contact the edge of the detection window.

2. A housing having an explosion-proof structure and a circuit board having a circuit having a flame detection function formed thereon; A plurality of detection light receiving elements are disposed so as to face an opening provided on the front side of the housing and receive light of a predetermined wavelength emitted by a flame; a detection window provided between the opening and the plurality of detection light receiving elements; A flame detector comprising: A fixing member constituting an explosion-proof structure is connected to a front wall surface of the housing by a screw, so that the entire edge of the detection window is sandwiched between the wall surface and the fixing member and fixed to the housing, The fixing member has an inner peripheral surface formed with a flange, When the flange comes into contact with an edge portion of the detection window, the detection window is sandwiched between the wall surface and the fixing member, A flame detector comprising: a ring-shaped seal member disposed between the wall surface and the detection window.

3. 2. The flame detector according to claim 1, further comprising an annular seal member disposed between said wall surface and said detection window.

4. A cylindrical wall body is provided on a front wall surface of the housing so as to protrude and surround the opening, and a female screw is formed on an inner peripheral surface of the wall body, The fixing member has an external thread formed on an outer circumferential surface thereof, The flame detector according to any one of claims 1 to 3, wherein the fixing member is connected to the wall body by screwing the male thread into the female thread.

5. 5. A flame detector as claimed in claim 1, further comprising an elastic support interposed between the peripheral edge of the detection window and the inner peripheral surface of the fixing member and the flange.

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