Optical fire detector and a method for mounting an optical fire detector

Abstract

Optical fire detector (1) with a light emitter (8) and a light receiver (9) receiving scattered light from the light emitter (8), with a printed circuit board (3), wherein the light emitter (8) and the light receiver (9) are each arranged on a printed circuit board section (5) of the printed circuit board (3), wherein at least one of the two printed circuit board sections (5) is arranged in an angled position at an angle to a surface extent (F) of the printed circuit board (3), characterized by the fact that the at least one printed circuit board section (5) has a weakened printed circuit board area (7) for pivoting the at least one printed circuit board section (5), wherein the weakened printed circuit board area (7) integrally connects the at least one printed circuit board section (5) to the printed circuit board (3).

Description

State of the art

[0001] The invention relates to an optical fire detector having the features of the preamble of claim 1. The invention also relates to a method for mounting an optical fire detector.

[0002] Fire alarm systems are used for automatic early fire detection in order to alert people to a dangerous situation. Optical fire alarm systems that detect smoke using the scattered light principle are known. For example, WO 01 / 78 031 A1, which arguably represents the closest prior art, describes a fire alarm with a circuit board, an optical transmitter, and a receiver, with the optical transmitter and receiver mounted on the circuit board. The optical transmitter and receiver are arranged in such a way that the light emitted by the transmitter is scattered by smoke particles and thus guided to the receiver. DE 100 54 110 A1 discloses a photoelectric high-performance smoke detector. US 2002 / 0 089 426 A1 discloses a smoke detection chamber for use in a light-scattering smoke detector.DE 10 2010 026 562 A1 discloses a sensor arrangement for detecting ambient conditions, particularly for a motor vehicle. DE 10 2006 004 521 A1 discloses a method for setting up a connection area of ​​a flexible printed circuit provided with at least one electronic component. Disclosure of the invention

[0003] Within the scope of the invention, an optical smoke detector having the features of claim 1 and a method having the features of claim 8 are disclosed. Preferred or advantageous embodiments of the invention emerge from the subclaims, the following description and the attached figures.

[0004] The invention thus relates to an optical fire detector with at least one or exactly one light emitter and at least one or exactly one light receiver that receives the scattered light from the light emitter. The light emitter emits a measuring light into a measuring chamber. The measuring light is deflected by potential smoke particles in the measuring chamber and scattered as scattered light to the light receiver. The scattered light received by the light receiver can be used to determine whether a fire is present, and as a result, an alarm signal can be issued to report the fire.

[0005] The light emitter is preferably designed as an LED, in particular as an infrared diode. The light receiver is designed as a sensor, in particular as a photodiode, for measuring the scattered light. The light emitter and the light receiver are preferably arranged such that the measuring space is located in an optical chamber of the optical fire detector, in particular in a labyrinth, or the measuring space is arranged freely in the vicinity of the fire detector.

[0006] The optical fire detector comprises a circuit board, with the light emitter and the light receiver each arranged on a circuit board section of the circuit board. In particular, the circuit board sections are formed as a sub-region of the circuit board. The circuit board and the two circuit board sections are manufactured, in particular, from a common semi-finished circuit board. The circuit board, also known as a printed circuit board, has conductor tracks for electrically conductive connections for the direct or indirect coupling of the light emitter and the light receiver.

[0007] Within the scope of the invention, it is proposed that at least one of the two circuit board sections, or both, be arranged in an angled position relative to the surface of the circuit board. With at least one circuit board section in the angled position, the light emitter and the light receiver are arranged relative to each other in such a way that the measuring light of the light emitter is emitted into the measuring space, scattered by potential smoke particles, and impinges on the light receiver as scattered light, without the emitted measuring light reaching the light receiver directly.

[0008] The at least one angled circuit board section enables simple and precise positioning of the light emitter and light receiver relative to each other, reliably preventing the measurement light from being scattered by smoke particles and the scattered light from impinging on the light receiver. From a manufacturing perspective, the angled circuit board section eliminates the need for complex, additional holding elements that hold the light emitter and / or light receiver in the desired angular position.

[0009] Particularly preferably, the light emitter and / or the light receiver are each embodied as an SMD component. The SMD components are mounted on the circuit board sections using so-called surface-mounted technology. This takes advantage of the fact that the circuit board and, in particular, the circuit board sections lie in one plane during production and can be assembled automatically, and the at least one circuit board section is only transferred to the angled position after assembly. This realizes an automated assembly process, which leads to cost reduction and quality improvement in the manufacturing process.

[0010] In particular, the at least one angled circuit board section is pivoted from a flat position into the angled position. In the flat position, a top side of the at least one circuit board section, on which the light emitter or the light receiver is arranged, and a top side of the circuit board as the surface extension preferably form a common flat top side. For pivoting the circuit board section into the angled position, the at least one circuit board section is preferably separated from the circuit board in some regions by means of recesses. The recesses form the contour of the at least one circuit board section in the circuit board and can be incorporated into the circuit board, for example, using a milling or etching process.

[0011] According to the invention, the at least one circuit board section has a weakened circuit board region. The weakened circuit board region forms a connecting link from the circuit board section to the circuit board. According to the invention, the circuit board section is integrally connected to the circuit board via the weakened circuit board region. Due to the weakened circuit board region, the at least one circuit board section can be easily pivoted from the flat to the angled position. For example, the weakened circuit board region is designed to be self-retaining, thus preventing unwanted angular adjustment of the circuit board section. Preferably, the weakened circuit board region forms a predetermined bending point around which the circuit board section can be pivoted into the angled position.From a structural perspective, it is preferred that the weakened circuit board region is thinner than the circuit board and / or the circuit board sections. Consequently, only a small amount of mechanical work needs to be performed to pivot the circuit board section into the angled position. For example, during the manufacturing process of the circuit board, the weakened circuit board region is made thinner than the circuit board and / or the circuit board sections. Alternatively, the weakened circuit board region can be subsequently tapered using an abrasive process. For example, the circuit board and the circuit board sections with the weakened circuit board regions are made, for example, from an FR4 material. Conductor tracks for electrically conductive connections for coupling the light emitter and / or the light receiver preferably run over or through the weakened circuit board region.

[0012] In an alternative embodiment, the optical fire detector has a flexible circuit board connection, wherein the flexible circuit board connection connects the circuit board and at least one of the two circuit board sections. The flexible circuit board connection is designed as a separate component from the circuit board and the two circuit board sections. The flexible circuit board connection is characterized by its flexibility, so that good mobility of the circuit board section to the circuit board is achieved. The flexible circuit board connection is designed as a flexible circuit board - also called flex PCB - and is arranged, for example, on the circuit board. This is preferably laminated onto the circuit board. However, it is particularly preferred that the flexible circuit board connection is arranged between the circuit board with the two circuit board sections and another continuous circuit board.In particular, the flexible printed circuit board connection is a polyimide film, e.g., a Kapton film. The flexible printed circuit board connection preferably extends over the entire surface area of ​​one or both printed circuit boards, with the one printed circuit board with the two printed circuit board sections having a recess in the pivoting area for pivoting the at least one printed circuit board section. Due to its mechanical flexibility, the flexible printed circuit board connection enables a reliable electrical connection from the printed circuit board section to the printed circuit board, even in the angled position.

[0013] In a further preferred embodiment, the optical fire detector has a housing section with at least one positioning device, wherein the at least one circuit board section rests positively on the positioning device. The housing section forms a support surface for the circuit board and can be arranged, for example, on a ceiling of a room. The positioning device is designed, for example, as a ramp for the circuit board section, wherein the ramp corresponds to the angle of the angled circuit board section. Thus, the positioning device limits the circuit board section in the angled position. The at least one positioning device can, for example, have locking hooks that engage around the circuit board section in the angled position. In this case, the at least one positioning device holds and secures the circuit board section precisely.

[0014] Particularly preferably, the housing section has a locking device in which the circuit board is fixed. The locking device can, for example, be designed as a plurality of latching hooks that engage around the circuit board and thus hold it securely in place. Preferably, when the circuit board is fixed to the housing section, the at least one circuit board section is transferred from the flat position to the angled position by the positioning device. When the circuit board is applied to the housing section, the positioning device moves the at least one circuit board section into the angled position. In this way, the circuit board section can be transferred into the angled position without the use of tools.

[0015] In principle, it is possible for the positioning device and the locking device to be designed as separate components. However, from a structural perspective, it is preferred for the at least one positioning device and the locking device to be integrally connected to the housing section. This one-piece design reduces the number of individual parts and thus reduces assembly effort. The housing section can, for example, be designed as an injection-molded part.

[0016] In an advantageous structural embodiment of the invention, both circuit board sections are arranged in angled positions at an angle to the surface area of ​​the circuit board. Preferably, two positioning devices are provided which delimit the circuit board sections in the angled position. The two angled circuit board sections enable a compact design of the optical fire detector. Particularly preferably, the circuit board sections are arranged at the same angle to the surface area of ​​the circuit board. The angle is arranged between the top side of the at least one circuit board section, on which the light emitter or light receiver is arranged, and the top side of the circuit board and is preferably between 100 and 120°. The angle between 100 and 120° forms a scattered light angle of between 30 and 50°.This scattered light angle range ensures reliable scattering of the measuring light from the light emitter over the potential smoke particles and further as scattered light to the light receiver.

[0017] In a preferred embodiment, the optical fire detector comprises at least one optical element, which is connected upstream of the light emitter and / or the light receiver. The optical element is preferably designed as a lens or prism, which focuses the light in a preferred direction.

[0018] Another subject of the invention relates to a method for assembling the optical fire detector according to the preceding description, wherein the circuit board sections are first populated with the light emitter and the light receiver, wherein the circuit board sections are arranged in a flat position in a common plane with the circuit board. The assembly is carried out, for example, using surface-mounted technology. In a subsequent step, the at least one circuit board section is transferred to the angled position.

[0019] The transfer takes place simultaneously with the application of the circuit board to the housing section. In particular, the housing section has at least one positioning device, which transfers the at least one circuit board section from the flat to the angled position during the application of the circuit board to the housing section.

[0020] Preferably, the at least one circuit board section is secured in the flat position to the circuit board via at least one fixing section. The at least one fixing section is designed, for example, as a fixing bridge that extends from the circuit board section to the circuit board via the recesses that form the circuit board section in the circuit board. The at least one fixing section is designed such that it is separated during or for transferring the at least one circuit board section from the flat to the angled position.

[0021] Further features, advantages, and effects of the invention will become apparent from the following description of preferred embodiments of the invention. These show: Fig. 1 shows a two-dimensional representation of an optical fire detector as a first embodiment of the invention; Fig. 2 in three-dimensional representation a circuit board made of Fig. 1 with a circuit board section in a flat position; Fig. 3 in three-dimensional representation the circuit board from Fig. 1 with the circuit board section in an angled position.

[0022] Fig. Figure 1 shows an optical fire detector 1 for automatically detecting a fire in a building or similar facility. The optical fire detector 1 comprises a housing section 2 and a circuit board 3, with the circuit board 3 being arranged on the housing section 2. The housing section 2 has a locking device 4, which is designed as a latching hook. The latching hooks engage around the circuit board 3, so that the circuit board 3 is held captively in the housing section 2.

[0023] The printed circuit board 3 has two printed circuit board sections 5, which are arranged at an angle to a surface extension F of the printed circuit board 3. The two printed circuit board sections 5 are each separated by recesses 6, which are Fig. 2 are formed from the circuit board 3. The two circuit board sections 5 each have a weakened circuit board area 7, which integrally connects the respective circuit board section 5 to the circuit board 3. The weakened circuit board area 7 serves to pivot the circuit board sections 5 from a flat position, as in Fig. 2, into an angled position as shown in Fig. 3. The weakened circuit board area 7 is tapered toward the circuit board 3 and the two circuit board sections 5, with the tapering being achieved, for example, by means of an abrasive process. The weakened circuit board area 7 comprises electrically conductive connections from the circuit board 3 to the circuit board sections 5 and allows bending without the need for significant force.

[0024] The optical fire detector 1 has a light emitter 8 and a light receiver 9, which are designed as SMD components. The light emitter 8 and the light receiver 9 are arranged on one of the two circuit board sections 5. Due to the angled circuit board sections 5, the light emitter 8 and the light receiver 9 are directed towards each other such that an optical axis A of the light emitter 8 and an optical axis A of the light receiver 9 form a scattered light angle α. The optical axis A of the light emitter 8 is defined by the emitted measuring light, and the optical axis A of the light receiver 9 is defined by the reception characteristics of the light receiver 9. The emitted measuring light is possibly scattered by smoke particles and thus transmitted as scattered light to the light receiver 9.

[0025] The circuit board sections 5 are positively connected to two positioning devices 10. The two positioning devices 10 are designed as ramps and define the angle β, which extends between the top side of the angled circuit board section 5, on which the light emitter 8 or the light receiver 9 is arranged, and the surface extension F of the circuit board 3. When the circuit board 3 is arranged on the housing section 2, the positioning devices 10 adjust the circuit board sections 5 from the flat position to the desired angled position with the angle β. The positioning devices 10 precisely align the circuit board sections 5 with one another.

[0026] The circuit board sections 5 are arranged at the same angle β, which is, for example, between 100 and 120°, to achieve a scattered light angle α between 30 and 50°. It is also possible to arrange the circuit board sections 5 at different angles β, such that the scattered light angle α lies between 30 and 50°. The scattered light angle range of 30 to 50° ensures the scattering of the measuring light to the light receiver 9.

[0027] The circuit board sections 5 are arranged mirror-symmetrically to one another. However, it is also possible for the circuit board sections 5 to be arranged asymmetrically, with the same angle β or unequal angles β to one another.

[0028] Fig. 2 shows the circuit board 3 with one of the circuit board sections 5 in the flat position. The circuit board 3 is provided with the recesses 6, which form the contour of the circuit board section 5. The circuit board section 5 is integrally connected to the circuit board 3 via a weakened circuit board area 7. Fixing sections 11 fix the circuit board section 5 to the circuit board 3. The fixing sections 11 are each designed as a fixing bridge, so that in the flat position, reliable and precise assembly of the circuit board section 5 with the light emitter 8 or the light receiver 9 is ensured. When the circuit board section 5 is transferred from the flat to the angled position, the fixing sections 11 are separated and the circuit board section 5 is connected to the circuit board 3 only via the weakened circuit board area 7.

[0029] Fig.Figure 3 shows the circuit board 3 with one of the circuit board sections 5 in the angled position. The circuit board section 5 is pivoted into the angled position via a pivot axis S. This is made possible by the weakened circuit board area 7, which is thinner than the circuit board 3 and the wider area of ​​the circuit board section 5, thus forming a predetermined bending point.

Claims

[1] Optical fire detector (1) with a light emitter (8) and a light receiver (9) receiving a scattered light from the light emitter (8), with a printed circuit board (3), wherein the light emitter (8) and the light receiver (9) are each arranged on a printed circuit board section (5) of the printed circuit board (3), wherein at least one of the two circuit board sections (5) is arranged in an angled position angled to a surface extension (F) of the circuit board (3), characterized by , that the at least one circuit board section (5) has a weakened circuit board region (7) for pivoting the at least one circuit board section (5), wherein the weakened circuit board region (7) integrally connects the at least one circuit board section (5) to the circuit board (3). [2] Optical fire detector (1) according to claim 1, characterized bythat the optical fire detector (1) has a housing section (2) with at least one positioning device (10), wherein the at least one circuit board section (5) rests positively on the positioning device (10). [3] Optical fire detector (1) according to claim 2, characterized by that the housing section (2) has a locking device (4) in which the printed circuit board (3) is fixed, wherein when the printed circuit board (3) is fixed, the at least one printed circuit board section (5) is transferred from a flat position into the angled position by the positioning device (10). [4] Optical fire detector (1) according to claim 3, characterized by that the at least one positioning device (10) and / or the locking device (4) are integrally connected to the housing section (2). [5] Optical fire detector (1) according to one of the preceding claims, characterized bythat both circuit board sections (5) are arranged in angled positions angled to the surface extension (F) of the circuit board (3). [6] Optical fire detector (1) according to claim 5, characterized by that the circuit board sections (5) are arranged at an angle between 100° and 120° to the surface extension (F) of the circuit board (3), wherein the angle is arranged between an upper side of the at least one circuit board section (5), on which the light emitter (8) or the light receiver (9) is arranged, and the upper side of the circuit board (3). [7] Optical fire detector (1) according to one of the preceding claims, characterized by that the optical fire detector (1) comprises at least one optical element which is connected upstream of the light emitter (8) and / or the light receiver (9). [8] Method for mounting an optical fire detector (1), in particular an optical fire detector (1) according to one of the preceding claims, characterized by following steps: - Equipping each circuit board section (5) with a light emitter (8) and a light receiver (9), wherein the circuit board sections (5) are arranged in a planar position in a plane to a circuit board (3); - transferring at least one of the two circuit board sections (5) into an angled position; - wherein the at least one circuit board section (5) is transferred from the flat to the angled position when the circuit board (3) is applied to a housing section (2). [9] Method for mounting the optical fire detector (1) according to claim 8, characterized bythat the at least one circuit board section (5) is fixed in the flat position to the circuit board (3) via at least one fixing section (11), wherein when the at least one circuit board section (5) is transferred from the flat to the angled position, the at least one fixing section (11) between the at least one circuit board section (5) and the circuit board (3) is separated.

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