The present invention relates to an arrangement for illumination according to the introductory portions of the independent claim.

In particular it relates to such an arrangement for illumination intended for illuminating particles in the air.

Background of the invention

The particle concentration in the air varies significantly and in many contexts it has to be controlled. Elevated particle concentrations may be unsuitable or directly dangerous. Substances in particle form may at sufficient concentrations be poisonous, give rise to allergies or even be flammable or explosive, so a simple visual indication of particle density would be desirable. Costly particle density meters are available, but a simpler solution would be advantageous.

An object of the invention is therefore to provide an arrangement for illumination which gives a visual indication of particle density in the air.

These and other objects are attained by an arrangement for illumination according to the characterising portion of the independent claim.

Summary of the invention

The invention relates to an arrangement 7a-b for illumination of particles in the air, comprising at least a line laser 7b that emit light in a narrow light sheet. The light sheet extends essentially parallel to and immediately next to a surface provided with at least one opening 5 for evacuation of air. This advantageously efficiently illuminates particles in the air near the opening where particle flow is elevated while minimizing the risk of dazzling an observer by direct light from the laser, making the contrast effect optimal.

In an advantageous embodiment the light in the narrow sheet is directed downwards at angle or straight downwards, further lowering the risk of an observer being dazzled by the light. In yet another advantageous embodiment the light in the narrow sheet has a wavelength shorter than that of yellow light or shorter than that of green light.

In yet another embodiment the light in the narrow sheet has a colour that is complementary to the ambient illumination.

The invention further relates to such an arrangement that is arranged in a fume room. Brief description of the drawings

Fig. 1 shows a fume room with particle illumination according to a first embodiment

Fig. 2 shows part of the first embodiment in greater detail

Fig. 3 shows a second embodiment of the particle illumination

Fig. 4 shows a third embodiment of the particle illumination

Fig. 5 shows a fourth embodiment of the particle illumination

Fig. 6 shows a fifth embodiment of the particle illumination

Description of preferred embodiments

A fume room is an arrangement similar to a fiime hood or a fume cabinet, but so large that an operator may work inside the fume room. Fume rooms are used when handling dangerous, infectious or irritable substances that emit gases or particles that have to be removed from the operator. A current of air is constantly moving through the fume room that is intended to remove particles and gases. In order to clearly indicate to an operator that particles really are being removed, and allowing the operator to take action if the particle concentration exceeds an acceptable level, it may be advantageous to illuminate the particles in the particle flow. Even what under normal conditions would be considered air that is seemingly completely devoid of particles, such air does contain particles and suitably illuminated these may be visible to the naked eye.

Fig. 1 shows a fume room 1 with particle illumination 7a according to a first embodiment. The fume room is constituted by a rectilinear volume divided into two sections by an inner wall 8. The larger section constitutes an operator space 2 and the smaller section is a fan and filter space 3. Inside the fan and filter space 3, a fan and a filter are typically arranged, that draws air through perforations 5 in the inner wall, through a filter and the purified air is then emitted through a rear wall 9 that is provided with perforations too.

Air is drawn through a perforated front wall 10 into the operator space, and the air then moves through the operator space towards the inner wall, such that a steady exchange of air and continuous air movement always takes place in the space. The purpose of this is that potentially contaminated air rapidly is replaced and sucked away from the operator.

A set of lamps 7a with reflectors are arranged inside the fan and filter space, and the light from these is directed towards the inner wall. The portion of the light from the lamps that reach the perforations 5 in the inner wall illuminates particles inside the perforations and also illuminates particles in the operator space in the immediate vicinity of the perforations. The lamps are directed angled downwards, such that the particles are heavily illuminated, while the operator is not reached by any significant portion of the light. This makes the particles stand out with a high degree of contrast. The flow of particles through the perforations is much higher than in the rest of the fume room, so illumination with beams of light that extend through the perforations gives a particularly visually clear illustration of the particle flow.

Fig. 2 shows part of the first embodiment in greater detail, and here only one lamp 7a with reflector is illustrated, with parts of the inner wall and the perforations that the light from the lamp reaches. In the figure, particles in the air in the operator space and within the perforations are illustrated as dots. The concentration of particles is normally not higher in the interior of the perforations or inside the light beam, but as the particles in the light beam are being lit, particles that would otherwise not been visible to the naked eye are seen. The figure clearly illustrates how the area around the perforations is perceived by the naked eye, with a seemingly heightened concentration of particles inside the perforation and along the light beam that extends out of the perforation. If these, what to the operator seem to be, clouds of particles shaped the way the beam through the perforation extends, vanishes, this is a clear warning that the air flow has been reduced or has ceased. This may indicated that a fan has stopped or that a filter has been clogged. If the beam shaped particle clouds instead become denser, it is an indication that particles have whirled up from some source and this may indicate that handling may need to be performed in a more gentle fashion.

Fig. 3 shows a second embodiment of the particle illumination, where the light sources 7b behind each perforation is constituted by lasers. The lasers are symbolically illustrated as electronic components and potentially necessary optics is not shown, all in order to simplify the

understanding. The lasers are in reality components on a circuit board and the circuit board extends over the right side of the inner wall. The circuit board has openings where the

perforations sits and the lasers are preferably positioned on thin tongues that extend a distance into these opening. The light from each laser is directed downwards at an angle, so as to achieve an optimal contrast effect for the particles in the air, as in the first embodiment.

Light impinging onto small particles is scattered and the scattering effect tends to be larger for short wavelength light than for long wavelength light. Blue and green light does therefore give a better contrast effect than orange and red light. The particle cloud therefore stands out more clearly with blue or green light and this is easier to achieve with lasers than with incandescent lamps.

Fig. 4 shows a third embodiment of the particle illumination, where the light source is constituted solely by a single laser 7b per row of perforations, where the laser light is split into beams with beam splitters 11. A beam splitter is arranged behind each perforation. The laser is symbolically illustrated as an electrical component and the beam splitters using symbols for optical

components. In reality, the light may be conducted using optical fibres across a flat disc corresponding to the electrical circuit board in the second embodiment, and the beam splitters may be designed in a much more cost effective way than the glass cubes the symbols illustrate.

Fig. 5 shows a fourth embodiment of the particle illumination, where the illumination elements in the same way as in the second embodiment are constituted by a set of lasers 7b. The lasers in the fourth embodiment are though arranged on the front side of the inner wall 8, which is the side that faces the operator space. The lasers sit just above each perforation and are directed downwards at an angle. This means that the laser beam extends downwards at an angle through part of the extension of each perforation, while the interior of the perforations is unilluminated.

In reality, the lasers are preferably arranged on a circuit board that covers the same area as the inner wall and is provided with openings that match the perforations. The circuit board may then cast into the inner wall such that the lasers end up in respective perforation and the perforations themselves then act as glare blockers, such that no stray light from the lasers dazzles the operator, and the contrast remains high.

Fig. 6 shows a fifth embodiment of the particle illumination, where the illumination element in the same way as in the third embodiment is constituted by a single laser 7b per row of perforations. Alternatively, the illumination element may be constituted by a single line laser 7b. The laser is arranged on the front side of the inner wall 8 and is directed straight down and immediately in front of the inner wall, such that the area in front of a whole row of perforations is being illuminated. The figure illustrates how the cloud of particles extends from the laser in an elongated space parallel to the inner wall.

In the fifth embodiment, a photo detector 12 is also arranged, directed in such a way that it primarily detects light that is scattered from particles in the light beam from the laser 7b. The photo detector therefore gives a measurement value for the particle density in the light beam. The flow of particles sucked into the perforations that then are replaced by new particles on their way out gives a fluctuating signal from the photo detector that reflects the particle flow per unit of time. The light from the laser may be visible to give an immediate visual indication to the operator, but using the photo detector the light may also be invisible and only be detected by the photo detector. This eliminates the dazzling effect that the operator otherwise could be exposed to, but in particular with a light beam directed straight down, this effect is small. Measurement values from the photo detector may then give a signal that acts as a complement to the visual effect.

The systems for illumination of particles in the air are in the disclosed embodiments used in a fume room, but quite obviously the particle illumination may be used in many other contexts. Examples of applications are cleanrooms, where the particle concentration is to be held low and it is of importance that an operator receives a visual indication that the particle concentration has been elevated, this with an otherwise completely passive system without sensors or software for evaluation of measurement values from particle sensors. Yet further examples of applications are smoke rooms, units for storage and handling of powdered foodstuffs such as flour, icing sugar and the like, that may become explosive at a too high concentrations, in the vicinity of combustion facilities where the combustion should take place in a sooting free fashion, while an elevated concentration of soot particles in the air indicates a sub optimal combustion.

The visual contrast effect gets greater if the light beam is directed such that is does not reach the operator and if the beam extends over an area that otherwise is not illuminated or at least is not heavily illuminated. The light from the particle illumination gives a larger degree of scattering from particles using short wavelength light, but if the other illumination happens to be colored, it may be suitable if the light from the particle illumination is complementary to the other illumination, even if this means that the particle illumination has a long wavelength. Typically it is suitable that the particle illumination extends through volumes of air where the particle concentration is elevated, or where the flow of particles is higher than in the surroundings.

Typical examples are smoke exhausts or openings for transfer of coal, flour or other dusty substances.

In the described embodiments, the particle illumination is exemplified with lamps and lasers, but obviously any type of lighting element may be used, such as light emitting diodes.