EP1977837B1 - Laboratory fume hood - Google Patents

Description

The present invention relates to a laboratory fume cupboard, meeting all the safety and performance requirements of French and European standards in the field.

A fume cupboard, an example of which is shown in figure 1 , is a laboratory device for receiving chemicals used by operators. This device is intended to ensure the protection of operators by limiting the spread of air pollutants in the laboratory.
A fume cupboard comprises a ventilated enclosure 10, closed by two side walls 11, a horizontal work surface 13, as well as a front face and a rear face. The front face is provided with a vertically movable facade 12, to allow access to chemicals by the operators.
There are different types of fume cupboards, among which we can mention the constant air flow fume cupboards and fume cupboards with variable air flow according to the opening of the mobile facade.
Fume cupboards, like all laboratory equipment, are subject to very strict requirements codified by safety standards, particularly at European and French levels. Since the publication of the first standards, the design of the fume cupboards has been adapted according to these safety and performance requirements.

The level of protection of the operators, when handling chemicals in the fume cupboard, can be evaluated using many criteria, among which we can mention the maximum opening height of the mobile front panel, the speed of air entering the fume cupboard or the level of containment. These last two criteria must be measured in the plane of the mobile front facade of the fume cupboard, since this is where the users are.

The latest standards in force in Europe and France have eliminated the requirement for minimum air velocity entering the fume cupboard, keeping only the level of containment requirement, and that of opening height of the mobile facade. For example, the French standard requires that the value of the confinement, measured at nine points on the frontal surface, be less than 0.1 parts per million (ppm).

This suppression has had a relatively significant impact on the design of fume cupboards, since it has allowed manufacturers to greatly reduce the air velocity, and thus to design fume cupboards that are more energy efficient for their operation.
Indeed, to achieve the incoming air speeds recommended by the above standards, it was necessary to implement a relatively large air extraction, for example of the order of 800 to 1000 cubic meters per hour. This extraction had, moreover, to be compensated by an injection of air in the room or the laboratory in which was installed the fume cupboard, this injection requiring a large supply of energy.
Manufacturers, having the possibility of reducing the flow of extracted air, were then able to manufacture fume cupboards that consume less energy.
However, on a "classic" fume cupboard, the fact of decreasing the speed of incoming air results in a reduction of the confinement to reach a level lower than the level required by the standard.

To remedy this drawback, one solution is to create an air curtain at the front of the enclosure, thus avoiding an output of pollutants, and to meet the level of confinement required.

Several systems have been proposed to create an air curtain that is efficient enough to provide the enclosure with the required containment. These known systems have the common feature of using electrical or hydraulic means for blowing air at low speed in the enclosure of the fume cupboard.
In some systems, the air is sent into the chamber via holes in the work plane supporting the enclosure, or in the walls or the amounts closing the enclosure. In other systems, the air comes from a blower directly installed in the top of the enclosure.

• une enceinte soumise à une pression inférieure à la pression extérieure, et fermée par des parois latérales, une paroi arrière et une paroi avant munie d'une façade mobile, et
• des moyens pour créer un rideau d'air dans le plan de la façade mobile.

Une sorbonne selon l'invention est caractérisée en ce que les moyens pour créer le rideau d'air comportent des ajours pratiqués dans l'encadrement de la zone d'ouverture de la sorbonne, ces ajours autorisant un écoulement d'air dans une direction orientée de façon telle que l'air extérieur passant par ces ajours forme le rideau d'air.
Ainsi, dans une telle sorbonne, le rideau d'air est créé sans apport d'énergie extérieure, ce qui permet de répondre aux exigences de faible coût et de facilité de fabrication susmentionnés.These systems, although effective, have the disadvantage of being relatively expensive.
On the one hand, the manufacturers have to modify the configuration of the existing fume cupboards to integrate the air injection system, which implies greater development and manufacturing costs and, on the other hand, the elements injection system are relatively expensive compared to the price of a fume cupboard.
The invention therefore aims to overcome this disadvantage by providing a laboratory fume hood cheaper and easier to manufacture, all in compliance with current safety standards.
Thus, the invention relates to a laboratory fume cupboard comprising:

• an enclosure subjected to a pressure lower than the external pressure, and closed by side walls, a rear wall and a front wall provided with a movable facade, and
• means for creating an air curtain in the plane of the moving facade.

A fume cupboard according to the invention is characterized in that the means for creating the air curtain comprise openings made in the frame of the opening zone of the fume cupboard, these openings allowing an air flow in a direction oriented in such a way that the outside air passing through these openings forms the air curtain.
Thus, in such a fume cupboard, the air curtain is created without external energy supply, which meets the requirements of low cost and ease of manufacture mentioned above.

The enclosure of the fume cupboard is in depression, that is to say that it is subjected to a pressure lower than the pressure of the room in which it is installed. Thus, during the opening, an air movement is formed from the outside of the enclosure inward, to restore the pressure balance. However, a fume cupboard according to the invention comprises openings in the frame of the opening area, openings that allow to establish a direct communication between the inside and outside of the enclosure, and to channel the movement of air that occurs.
It is specified here that, by framing the opening area, we mean the ends of the vertical side walls supporting the movable facade, the end of the work plan located above the facade or recessed, for example 50 mm, with respect to this plumb, the bottom of the movable facade, or any integral part of one of these elements. This frame is thus entirely in the plane of the mobile facade.

• une poignée, installée sur la façade mobile, et destinée à faciliter son ouverture, ou
• un rail, encastré dans une paroi latérale, et permettant le coulissement et/ou roulement de la façade mobile.

The integral parts of an element, referred to in the preceding paragraph, are for example:

• a handle, installed on the mobile facade, and intended to facilitate its opening, or
• a rail, recessed in a side wall, and allowing the sliding and / or rolling of the movable facade.

• une enceinte soumise à une pression inférieure à la pression extérieure et fermée par des parois latérales, une paroi arrière et une paroi avant munie d'une façade mobile, et
• des moyens pour créer un rideau d'air dans le plan de la façade mobile,

caractérisée en ce que ces moyens comportent des ajours pratiqués dans une poignée creuse installée au bas de la façade mobile de la sorbonne, ces ajours autorisant un écoulement d'air dans une direction orientée de façon telle que l'air extérieur passant par ces ajours forme le rideau d'air les ajours comprenant des ajours intérieurs, pratiqués entre l'intérieur de la poignée et l'intérieur de l'enceinte, sur un angle inférieur de la poignée.Thus, preferably, the invention relates to a laboratory fume hood comprising:

• an enclosure subjected to a pressure lower than the external pressure and closed by side walls, a rear wall and a front wall provided with a movable facade, and
• means for creating an air curtain in the plane of the mobile facade,

characterized in that these means comprise openings in a hollow handle installed at the bottom of the movable facade of the fume cupboard, these openings allowing an air flow in a direction oriented so that the outside air passing through these openings forms the air curtain the openings comprising interior openings, made between the inside of the handle and the inside of the enclosure, on a lower angle of the handle.

The fume cupboard standards require the front of the fume cupboards to be translucent. Thus, a transparent material, such as glass, is preferably chosen for the manufacture of the mobile facade.

The openings are oriented so that the air is channeled to form a curtain of air in the plane of the movable facade, or in a plane substantially oblique with respect to the plane of the front facade.
Therefore, in a fume cupboard according to the invention, no additional electrical means is required since only the configuration of the openings is used to create the air curtain that allows to meet the requirements in terms of confinement.

Different configurations of the openings will now be considered. The realization of these variants will be detailed later with the support of figures.

A first embodiment is based on the observation already made that changes in the design of a fume cupboard involve many costs in terms of development and manufacturing, since it is appropriate, for example, to modify the manufacturing processes. Thus, in the first embodiment, the openings are made in a handle installed at the bottom of the mobile facade. In fact, this solution makes it possible to modify in no way the main frame of the existing fume cupboards, but to intervene only at the level of the handle, which is an additional element, integral with the mobile facade.
This handle is designed to meet the requirements in this regard, since, for example, the standard requires that the size and position of the movable facade handles do not pose a risk to the operator by reducing his field of vision or workspace.

• des ajours extérieurs, pratiqués entre l'extérieur de la sorbonne et l'intérieur de la poignée, et
• des ajours intérieurs, pratiqués entre l'intérieur de la poignée et l'intérieur de l'enceinte.

In an advantageous embodiment of the invention, the handle is hollow and the openings include:

• external openings, made between the outside of the fume cupboard and the inside of the handle, and
• interior openings, made between the inside of the handle and the inside of the enclosure.

Thus, the outside air, attracted by the depression created in the enclosure, enters the interior of the handle via the external openings, and is transmitted inside the enclosure via the interior openings.

The position of the various openings is essential for a good efficiency of this device for creating air curtain. Thus, in one embodiment, the outer openings are made on a horizontal face of the handle. These openings are made perpendicularly to this face, thus creating a vertical airflow entering the handle.
As regards the interior openings, they are, in one embodiment, practiced on a lower angle of the handle. This positioning of the interior openings allows the creation, at the outlet of the handle, of a flow of air in a slightly oblique direction relative to the vertical plane located at the base of the movable facade. The oblique direction makes it possible to create an air curtain whose effectiveness is reinforced.

Another important aspect for the creation of the curtain is the shape and number of openings in the handle. Thus, in one embodiment, the outer openings are circular in shape and, in another embodiment, usable in combination, the inner openings are rectangular in shape.

In the case where the openings are made in a hollow handle, it is necessary to ensure the tightness of the handle so that no air flow passes through other openings that the openings provided for the creation of the curtain. Indeed, these parasitic air flows would have the effect of dispersing the flow of outside air, thus preventing a good formation of the air curtain.
For this purpose, in one embodiment, the handle comprises a plug at each of its ends, to ensure its sealing.

In a second embodiment, distinct from that using a handle, it is chosen not to practice the openings in an integral element of the movable facade, but directly in the lateral amounts of framing of the opening area.
Thus, in one embodiment, the openings are made in a groove installed on a side wall of the enclosure, and intended to receive the movable facade.

These openings make it possible to establish a direct communication channel between the outside of the fume cupboard and the inside of the enclosure. In one example, the openings are made inside the grooves, horizontally, or in a direction parallel to normal to the side faces of the enclosure. This orientation of the openings makes it possible to direct the air so as to form a curtain of air in the plane of the movable facade.
The positioning of the openings in a groove, intended to receive the movable facade, makes it very easy to open these openings when it is necessary to create a curtain of air.
When opening the enclosure, the movable facade is raised, thus allowing air flow from the outside of the fume hood inwards, via the openings thus discovered.

The main difference between this embodiment and that implementing a handle lies in the permanent appearance and / or temporary creation of the air curtain.
In an embodiment using a handle, the air curtain is retained regardless of the position of the mobile facade, since this facade is such that it does not achieve complete sealing of the fume cupboard, even in the closed position, this which results in the preservation of an air flow permanently.
On the other hand, in an embodiment using openings made in a lateral groove, no air flow is created when the facade is in the lower position, since all the openings are closed.

This second embodiment has, among others, the advantage of allowing the creation of a variable air curtain depending on the opening level.
Indeed, the more the movable facade is raised, the greater the number of unclosed openings is important, which has the effect of increasing the amount of air introduced. In order to be able to control this variation, it is useful, in one embodiment, for the openings to be evenly distributed over the groove, between the bottom of this groove and a maximum opening position of the mobile facade.
The maximum opening position of the movable facade corresponds to the movable bottom of the facade when it is in a high abutment position for conventional use. Indeed, the standards in force require that, during a use of the fume cupboard by an operator, the mobile facade can not be raised in such a way the opening zone has a height greater than a predetermined value, for example fixed at 40 or 50 centimeters according to the standards and / or the requirements of the users.

In a conventional embodiment of fume cupboard, the movable facade slides inside two machined grooves or recessed rails in each of the side walls of the fume cupboard. In this case, as an alternative of the invention, it is possible to make openings in each of the grooves.

In the state of the art existing, as previously described, it is known to inject air through holes in the work plane, that is to say the lower horizontal plane of the fume cupboard. However, these holes are not intended to establish a direct communication between the inside and outside of the fume cupboard, but only a communication between an air injection device and the interior of the fume cupboard.
In the invention described here, on the other hand, direct communication is established. The configuration in which openings are made in the worktop does not appear as a preferential solution for the claimed invention, because the quality of the air curtain obtained and its impact in improving the confinement is relatively low.

• la figure 1 représente une sorbonne classique,
• la figure 2 représente une vue en trois dimensions d'une poignée utilisable dans une sorbonne conforme à l'invention,
• les figures 3a, 3b et 3c représentent respectivement une vue de face, une vue de dessus et une vue latérale d'une poignée utilisable dans une sorbonne conforme à l'invention.
• la figure 4 montre une vue en coupe d'une poignée installée sur la façade mobile d'une sorbonne conforme à l'invention.

We will now proceed to the description, made without limitation, of the preferred embodiment of the invention, which implements a handle installed at the bottom of the mobile facade.
This description, which will make it possible to show other advantages of the invention, is carried out using figures in which:

• the figure 1 represents a classic fume cupboard,
• the figure 2 represents a three-dimensional view of a handle that can be used in a fume cupboard according to the invention,
• the Figures 3a, 3b and 3c represent respectively a front view, a top view and a side view of a handle used in a fume cupboard according to the invention.
• the figure 4 shows a sectional view of a handle installed on the movable facade of a fume cupboard according to the invention.

The different numerical values cited in the remainder of the description serve to illustrate a particular embodiment, but are in no way intended to limit the scope of the invention to these precise values.

Description of the handle:

• Une première partie est composée de trois surfaces planes verticales, reliées entre elles par deux surfaces planes horizontales, de manière à former un escalier. La première surface verticale 21 est prolongée de manière à créer, avec la première surface horizontale 31 et la deuxième face verticale 22, une rainure parallélépipédique 20 destinée à recevoir la base de la façade mobile d'une sorbonne conforme à l'invention.
• Dans un exemple de réalisation, la configuration de cette première partie est la suivante :
  • la première surface verticale 21 a une hauteur de 45 millimètres en tout,
  • la première surface horizontale 31, placée à 20 millimètres du bas de la première surface verticale, a une longueur de 8 millimètres,
  • la deuxième surface verticale 22, placée à l'extrémité de la première surface horizontale 31, a une hauteur de 16 millimètres,
  • la deuxième surface horizontale 32, placée au niveau du haut de l'extrémité supérieure de la deuxième surface verticale 32, a une longueur de 5 millimètres, et
  • la troisième surface verticale 23 a une hauteur de 11 millimètres.
• Une seconde partie de la paroi périphérique est composée de 2 arcs de cercles 41 et 42 de rayons différents, destinés à fermer l'ouverture formée sous la première partie de la paroi.
• Le premier arc de cercle 41, de rayon supérieur, part de l'extrémité supérieure de la troisième surface verticale 23 précédemment décrite.
• Il rejoint le second arc de cercle 42, partant de l'extrémité inférieure de la première surface verticale 21.

The handle, shown on figures 2 , 3a and 3b , is a hollow profile whose peripheral wall has a thickness of the order of a few millimeters. This wall is, for example, made of a plastic material such as polypropylene or PVC.
The total length of the handle depends on the type and size of fume cupboard manufactured. This length is, for example, included in the group comprising: 948 millimeters, 1248 millimeters and 1548 millimeters.
The peripheral wall of the cylinder can be broken down into several parts:

• A first part is composed of three vertical flat surfaces, interconnected by two horizontal flat surfaces, so as to form a staircase. The first vertical surface 21 is extended so as to create, with the first horizontal surface 31 and the second vertical face 22, a parallelepipedal groove 20 intended to receive the base of the movable facade of a fume cupboard according to the invention.
• In an exemplary embodiment, the configuration of this first part is as follows:
  • the first vertical surface 21 has a height of 45 millimeters in all,
  • the first horizontal surface 31, placed 20 millimeters from the bottom of the first vertical surface, has a length of 8 millimeters,
  • the second vertical surface 22, placed at the end of the first horizontal surface 31, has a height of 16 millimeters,
  • the second horizontal surface 32, located at the top of the upper end of the second vertical surface 32, has a length of 5 millimeters, and
  • the third vertical surface 23 has a height of 11 millimeters.
• A second portion of the peripheral wall is composed of 2 arcs of circles 41 and 42 of different radii, intended to close the opening formed under the first part of the wall.
• The first arc of circle 41, of greater radius, starts from the upper end of the third vertical surface 23 previously described.
• It joins the second arc 42, starting from the lower end of the first vertical surface 21.

In this preferred embodiment, the outer openings 51 are made in the second horizontal surface 32. These openings are in the form of circular holes. They are, in some embodiments, practiced regularly over the entire length of the handle. In one example, the openings 51 have a diameter of 5 millimeters, and, as shown in FIG. figure 3b they are distributed along the length with a step of 20 millimeters.
He appears on this figure 3b whereas, seen from above, the handle has a width of 44.9 millimeters.
When a movable facade is placed in the groove 20, the second horizontal surface 31 is framed by two vertical surfaces, namely the vertical surface 23 and the outer wall of the movable facade. This configuration has the effect of creating a nozzle for the acceleration of the air before entering the handle via the outer openings 51.

The external openings 52 are, in turn, made at the angular edge formed by the lower end of the vertical surface 21 and the lower end of the arc 42.
These openings 52 have an aperture of 5 millimeters in the vertical surface 21, and 1 millimeter in the circular arc 42.
As shown on the figure 3c , the outer openings 52 have a rectangular shape, and are evenly distributed over the entire length. In one example, they each have a length of 111 millimeters, and the solid space between two openings has a length of 40 millimeters.

Inside the handle, the angle formed by the surface 31 and the surface 22 contributes to creating, with the bottom of the arc 42, a second nozzle allowing a good channeling of the air passing through the handle, at the time of exit by the external openings 52.

The position of these openings at the lower angular edge of the handle is essential for the creation of an air curtain to meet the containment standards.
Indeed, in the case where these openings are made only in the vertical surface 21, the air flow exiting the handle flows in a direction close to the horizontal direction at the bottom of the handle. Thus, when the mobile facade is in the maximum opening position, the confinement at the bottom of the opening zone may not be sufficient.
Furthermore, in the case where these openings are made only on the end of the arc 42, the air flow exiting the handle flows in a direction close to the vertical in line with the surface mobile. In this situation, a large part of the air may escape to the outside of the fume cupboard, thus no longer being able to be used for the creation of a correct air curtain.

In another conceivable embodiment, the right angle formed by the intersection of the horizontal surface 31 and the vertical surface 22 is replaced by a quarter circle. This configuration allows, in some cases, to improve the circulation of air inside the handle, and thus the efficiency of the creation of the air curtain.

The handle being hollow, it is necessary to close at each end, to prevent the air entering through the outer openings is dispersed by these ends.
For this purpose, plugs are integrally installed at each end. These plugs are elements, for example made of plastic material, which are glued to the outer edges of the peripheral wall of the handle.

Installing the handle on the mobile front:

The figure 4 shows a sectional view of a detail of a fume cupboard according to the invention. In this figure we see a handle 1 installed on the bottom This movable facade is intended to close a chamber 3 in depression. It should be noted that, even when the mobile facade is in the closed position, it does not achieve complete sealing of the fume cupboard, as this would lead to a suppression of the airflow necessary for the creation of the air curtain in the plane of the mobile facade, and prevent the evacuation of toxic vapors.
The handle is deployed on the lower horizontal part of the movable front 2.

Under the effect of the pressure difference between the inside of the chamber 3 and the outside, a flow of air rushes through the outer openings, through the handle and out through the interior openings, creating a curtain of air in a slightly oblique direction relative to the vertical plane of the movable facade.

Claims (6)

1. A laboratory fume hood comprising:

   - an enclosure (3; 10) subjected to pressure below the outside pressure and closed by side walls (11), a rear wall and a front wall with a mobile front (2; 12), and

   - means to create an air curtain in the plane of the mobile front,
   characterized in that these means comprise cut-outs (51, 52) made in a hollow handle installed at the bottom of the mobile front (2) of the fume hood, wherein said cut-outs (51, 52) allow air to flow in a direction turned in such a way that the outside air flowing through the cut-outs forms an air curtain, wherein the cut-outs (51, 52) comprise inner cut-outs (52) made between the inside of the handle and the inside of the enclosure, on a lower corner of the handle in order to create a flow of air in a direction that is slightly slanted in relation to the vertical plane located directly below the mobile front (2).
2. A laboratory fume hood according to claim 1, characterized in that the cut-outs further comprise outer cut-outs (51) made between the outside of the fume hood and the inside of the handle (1).
3. A laboratory fume hood according to claim 2, characterized in that the outer cut-outs (51) are made on a horizontal side (32) of the handle, perpendicular to that side.
4. A laboratory fume hood according to claim 2 or 3, characterized in that the outer cut-outs (51) are circular in shape
5. A laboratory fume hood according to any of the preceding claims, characterized in that the outer cut-outs (52) are rectangular cut-outs.
6. A laboratory fume hood according to any of the preceding claims, characterized in that the handle comprises a plug at each of its ends in order to seal it.

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