EP4589561A1

EP4589561A1 - Self-cleaning linear beam smoke detectors and method for cleaning thereof

Info

Publication number: EP4589561A1
Application number: EP24152653.2A
Authority: EP
Inventors: Luis Marques; Filipe Barbosa; Luis Moutinho; Filipe Valente
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2024-01-18
Filing date: 2024-01-18
Publication date: 2025-07-23

Abstract

A self-cleaning linear beam smoke detector comprising: an optical component comprising an environmentally-exposed surface; a cantilever beam arranged to vibrate at a natural frequency and to transmit vibration to said surface; a protuberance arranged to hit the cantilever beam for causing said beam to vibrate; a motor arranged for providing a relative displacement between the beam and protuberance for causing the protuberance to hit the cantilever beam and method for cleaning thereof.

Description

TECHNICAL FIELD

The present disclosure belongs to the technical field of smoke detectors, and more particularly to a self-cleaning linear beam smoke detector.

BACKGROUND

Linear beam smoke detectors use an optical path to detect the presence of smoke or other particulate matter in the air. This optical path consists of a transmitter unit and a receiver unit. The transmitter unit emits a beam of light (e.g., infrared or blue light), which is collimated by a lens and directed towards a reflective element, which is mounted in the environment at a certain distance. The reflection is then detected by the receiver unit.
When smoke particles enter the optical path, they scatter the Infrared (IR) or blue beam and cause a change in the power that is detected by the receiver unit. If this change in power exceeds a base threshold value, an alarm signal is triggered.
The lens used in a linear beam smoke detector is typically a high-quality, precision lens made from glass or a transparent polymer material. It is designed and positioned to ensure that the IR beam's power that reaches the reflective element is maximized. The lens must also be able to withstand the harsh environmental conditions often encountered in industrial or commercial settings, such as high temperatures, light reflection, humidity, and airborne contaminants. The Lens are assembled onto a holding structure that can be moved manually or by a servomotor, so correct alignment with the reflective element is achieved.
To protect the lens and filter out ambient infrared interference, a filter cover is typically deployed. However, overtime dust and other particles accumulate on this filter, affecting the sensitivity of the detector, by blocking the infrared beam and creating unwanted light reflection, which could cause the triggering of false alarms. To keep the correct operational condition, these devices are subject to periodical maintenance and manual cleaning, a process that requires specialized personnel and is extremely time-consuming and costly.
Document EP3889579A1 providing an optical smoke detector comprises an ultrasonic transducer configured to cause oscillations in its housing so as to dislodge accumulated particulate matter from the walls of a sensor chamber or a labyrinth of the smoke detector. Additionally, or alternatively, the ultrasonic transducer may be configured to cause oscillations that dislodge accumulated particulate matter from a light source or a light receiver of the smoke detector.
Document GB2281619B providing an invention relates to a light scattering type smoke sensor has a plurality of labyrinth members for facilitating an inflow of smoke entering from the outside, and for cutting off light entering from the outside; a smoke detecting chamber which is formed in a center portion by the labyrinth members; light emitting device for radiating light toward the smoke detecting chamber; and light receiving device for detecting light which is scattered by the smoke in the smoke detecting chamber, the light receiving device having an optical axis which intersects the optical axis of the light emitting device at a scattering angle in the range of 60 to 80 DEG, wherein one of the labyrinth members intersects the optical axis of the light emitting device, and has a reflecting face for reflecting light radiated from the light emitting device, in a direction opposite to the light receiving device.; Preferably the member is at 45 DEG to the optical axis of the light emitting means and the projecting area of the emitting means is within a height of the member.
Document US20160146721A1 discloses an open path optical sensing system having an ultrasonic cleaner. The system includes at least one ultrasound transducer which is configured to propagate ultrasonic waves across exposed surfaces of optical components of the optical sensing system. The ultrasonic waves create tiny vibrations on the exposed surfaces of the optical components which clean the surfaces of environmental pollutants and prevent environmental pollutants from accumulating on the surface. The ultrasonic waves may have a frequency that is substantially different than the modulation frequency of a modulated laser light beam that is generated by a laser of the open path optical sensing system. The surfaces of a plurality of optical components may be cleaned by the ultrasonic waves of a single ultrasound transducer. A plurality of ultrasound transducers may propagate waves on a single optical component.
These facts are disclosed in order to illustrate the technical problem addressed by the present disclosure.

GENERAL DESCRIPTION

The present disclosure discloses a self-cleaning linear beam smoke detector comprising: an optical component comprising an environmentally-exposed surface; a cantilever beam arranged to vibrate at a frequency, especially a natural frequency, and to transmit vibration to said surface; a protuberance arranged to hit the cantilever beam for causing said beam to vibrate; a motor arranged for providing a relative displacement between the beam and protuberance for causing the protuberance to hit the cantilever beam.
In an embodiment, the motor is further arranged for adjusting and aligning the optical component within the detector.
In an embodiment, the motor can be a lens-alignment motor for adjusting and aligning the optical component or optical components within the detector.
In an embodiment, the cantilever beam and protuberance can be arranged for rotative relative displacement or linear relative displacement.
In an embodiment, said protuberance is mounted on the optical component which is displaceable relative to said beam for causing the protuberance to hit the cantilever beam.
In an embodiment, the optical component comprises a light source for emitting a beam of light and a light detector for detecting an absence of reflection of said beam of light.
In an embodiment, a self-cleaning linear beam smoke detector further comprises an optical chamber with one or more openings for allowing the passage of light emitted by the light source and reflected light for the light detector, wherein the optical component is comprised in said optical chamber.
In an embodiment, the cantilever beam and the environmentally-exposed surface are mounted on said optical chamber.
In an embodiment, the optical component is displaceable relative to said optical chamber for causing the protuberance to hit the cantilever beam.
In an embodiment, a self-cleaning linear beam smoke detector further comprises an electronic data processor arranged to control the motor to providing relative displacement between the beam and protuberance for causing the protuberance to hit the cantilever beam.
In an embodiment, the motor can be a servomotor or a stepper motor.
In an embodiment, the cantilever beam can be arranged to vibrate at a natural frequency of 10 - 100 Hz, preferably 30 - 50 Hz, more preferably approximately 30 Hz.
In an embodiment, said protuberance can be arranged as cantilever beam.
In an embodiment, said environmentally-exposed surface can be an infra-red filter.
It also disclosed a method for cleaning an environmentally-exposed surface of a self-cleaning linear beam smoke detector characterized by the smoke detector being according described in any of the previous embodiments, the method comprising: providing by the motor a relative displacement between the beam and protuberance for causing the protuberance to hit the cantilever beam; vibrating at a frequency, especially a natural frequency, the cantilever beam and to transmit vibration to said surface.
Here, we propose a method that exploits the existence of a servomotor to perform the lens alignment with the reflective element, which can also be used to produce mechanical vibrations into the filter cover, in order to release undesired particles and keep the filter clean.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures provide preferred embodiments for illustrating the disclosure and should not be seen as limiting the scope of invention.
Figure 1 : Schematic representation of an embodiment of the present disclosure.

DETAILED DESCRIPTION

The present disclosure relates to a self-cleaning linear beam smoke detector comprising: an optical component comprising an environmentally-exposed surface 1; a cantilever beam 2 arranged to vibrate at a natural frequency and to transmit vibration to said surface 1; a protuberance 3 arranged to hit the cantilever beam 2 for causing said beam to vibrate; a motor arranged for providing a relative displacement between the beam and protuberance for causing the protuberance 3 to hit the cantilever beam 2.
Ultrasonic ^[1] and vibration actuation ^[2] techniques can be used to prevent dust accumulation and/or perform cleaning of dust-contaminated structures. In particular, dust and other particles can be dislodged by inducing vibrations on the affected surface at certain patterns and frequencies.
Vibrations can be typically created by using electromechanical devices such eccentric rotating mass vibration motors (as found in haptic systems for smartphones) to piezoelectric vibrators. Here, the present disclosure proposes to exploit the lens-alignment servomotors in linear beam smoke detectors to induce such vibrations on the filter cover via a mechanical actuation of elements akin to cantilever beams or even chords. Figure 1 shows the main components of the proposed method.
One of the main concepts is to place one or more cantilever beam like elements 2 embedded into the filter cover 1 that can oscillate at a certain natural frequency from an initial displacement applied at the free end. These elements can be placed perpendicular to the filter's front face or at the bottom/top of the filter enclosure. The generated natural vibration frequency can be adjusted as desired by altering the material and/or geometric parameters of the embedded element such as, length, width or thickness.
During alignment with reflective element, the lens holding structure is moved by the action of a servomotor 4, within a normal working range. When the servomotor operates beyond the nominal working range, rigid elements, which are also part of the lens holding structure 3 will collide with the cantilever beam like elements 2 and generate a load at their free end, causing them to oscillate at their natural frequency dictated by the combination of material and geometric parameters of the cantilever beam.
Vibrations will then be propagated through the filter cover and dislodge accumulated particles. Multiple cantilever beam-like elements with different properties can be embedded into the filter cover to generate different vibration frequencies.
Finally, a similar procedure can be used to excite chords attached to the filter cover for the same purpose. Attaching chords to the cover would be more complex manufacturing-wise but would provide further options to generate different ranges of frequencies.
It is important to note that to oscillate at a certain natural frequency means that a system or an object is vibrating or oscillating at a specific frequency determined by its physical properties. In the context of physics and engineering, natural frequency refers to the frequency at which a system vibrates when it is disturbed or set into motion and then left to oscillate freely. Some key points regarding oscillation at a certain natural frequency include, for example:

System Resonance: When a system or object is subjected to an external force that matches its natural frequency, resonance occurs. Resonance leads to an increase in the amplitude of the oscillations, which can have significant effects on the system.
Dependence on Physical Properties: The natural frequency of a system is determined by its physical characteristics such as mass, stiffness, and damping. These properties influence how the system responds to external forces and how it vibrates over time.

Controlling or adjusting the natural frequency of a system is important in many applications, as it can help prevent unwanted resonance and ensure the stable and efficient operation of mechanical and structural systems.
The term "comprising" whenever used in this document is intended to indicate the presence of stated features, integers, steps, components, but not to preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.
The disclosure should not be seen in any way restricted to the embodiments described and a person with ordinary skill in the art will foresee many possibilities to modifications thereof. The above-described embodiments are combinable. The following claims further set out particular embodiments of the disclosure.

Claims

Self-cleaning linear beam smoke detector comprising:
an optical component comprising an environmentally-exposed surface (1);

a cantilever beam (2) arranged to vibrate at a frequency, especially a natural frequency, and to transmit vibration to said surface (1);

a protuberance (3) arranged to hit the cantilever beam (2) for causing said beam to vibrate;

a motor arranged for providing a relative displacement between the cantilever beam (2) and protuberance (3) for causing the protuberance (3) to hit the cantilever beam (2).
Self-cleaning linear beam smoke detector according to the previous claim wherein the motor is further arranged for adjusting and aligning the optical component within the detector.
Self-cleaning linear beam smoke detector according to any of the previous claims wherein the motor is a lens-alignment motor for adjusting and aligning the optical component or optical components within the detector.
Self-cleaning linear beam smoke detector according to any of the previous claims wherein the cantilever beam and protuberance are arranged for rotative relative displacement or linear relative displacement.
Self-cleaning linear beam smoke detector according to any of the previous claims wherein said protuberance (3) is mounted on the optical component (4) which is displaceable relative to said beam (2) for causing the protuberance (3) to hit the cantilever beam (2).
Self-cleaning linear beam smoke detector according to any of the previous claims wherein the optical component comprises a light source for emitting a beam of light and a light detector for detecting an absence of reflection of said beam of light.
Self-cleaning linear beam smoke detector according to the previous claim further comprising an optical chamber with one or more openings for allowing the passage of light emitted by the light source and reflected light for the light detector, wherein the optical component is comprised in said optical chamber.
Self-cleaning linear beam smoke detector according to claim 6 or 7, wherein the cantilever beam (2) and the environmentally-exposed surface (1) are mounted on said optical chamber.
Self-cleaning linear beam smoke detector according to any of the claims 6 - 8, wherein the optical component is displaceable relative to said optical chamber for causing the protuberance (3) to hit the cantilever beam (2).
Self-cleaning linear beam smoke detector according to any of the previous claims comprising an electronic data processor arranged to control the motor to providing relative displacement between the beam and protuberance for causing the protuberance (3) to hit the cantilever beam (2).
Self-cleaning linear beam smoke detector according to any of the previous claims wherein the motor is a servomotor or a stepper motor.
Self-cleaning linear beam smoke detector according to any of the previous claims wherein the cantilever beam (2) is arranged to vibrate at a natural frequency of 10 - 100 Hz, preferably 30 - 50 Hz, more preferably approximately 30 Hz.
Self-cleaning linear beam smoke detector according to any of the previous claims wherein said protuberance (3) is arranged as cantilever beam.
Self-cleaning linear beam smoke detector according to any of the previous claims wherein said environmentally-exposed surface (1) is an infra-red filter.
Method for cleaning an environmentally-exposed surface of a self-cleaning linear beam smoke detector, especially characterized by the smoke detector being according to any of the claims 1-14, the method comprising:
providing by a motor a relative displacement between a cantilever beam (2) and a protuberance (3) for causing the protuberance (3) to hit the cantilever beam (2);

vibrating at a frequency, especially a natural frequency, the cantilever beam (2) and to transmit vibration to said surface (1).