FIELD OF THE INVENTION

The invention generally relates to labour that has to be done in a protected environment. By way of example, but not exclusively, the invention relates to decontamination work in residential houses or other buildings, where asbestos is to be removed.

BACKGROUND OF THE INVENTION

As known, removing asbestos is a dangerous job, in which asbestos particles can be releases which form a health risk when inhaled. However, it not always possible to completely vacate a building while the work is being done. For this type of situations, it is known to create a sealed working space with the use of screening elements, which working space is sealed off from the remainder of the room. Figure 1 is a schematic perspective view, showing such shielding box. The shielding box 1 , which may be assembled from multiple shielding panels in a modular way, is for instance arranged around a windowsill or a part of a wall to be decontaminated. Care is being taken that the box always joins the wall in an airtight manner. The box is provided with multiple passage holes 3, which may for instance be provided with work gloves, wherein always the collar of such work glove is attached to the edge of such passage hole 3 in a sealing manner. Also there are lids provided for completely closing such passage hole. An advantage of such approach is that the workers can reside outside the box in a clean room, and can perform the work in the working space shielded by the shielding box by extending their arms through a passage hole, while their hands will reach into a glove mentioned. In such manner, they can operate the tools present in the working space. In fact, residents or other users of the room concerned may simply stay present, outside the shielded working space, which is a big advantage for the residents; it is true that they experience the usual nuisance of work in progress, but they are protected against possibly released harmful dust particles, particularly asbestos.

A system separating a potentially contaminated working space from the remainder of a room in a building in such manner, so that it is possible to work in a safe manner within the shielded space without there being any danger in the remainder of the room of being exposed to the potentially harmful dust particles, is indicated by the phrase "containment" system and the shielding wall used for that purpose is indicated by the phrase "containment" wall.

For a well-functioning "containment" system, two other functional components are important. In the first place, it is important that the pressure within the working space is kept lower than the pressure outside. Thus, in the case of possibly occurring leakage, no contaminated air can escape to the outside. In order to achieve this, a so-called lowpressure machine is connected, which machine is no subject of the present invention and is therefore not shown for sake of simplicity. Suffice it to note that this is a very specialistic, professional apparatus.

In the case of removing asbestos and comparable work, typically dust is released, which must be removed by suction. A second important component therefore is a dust suction device. Up to now, for this purpose an "ordinary" vacuum cleaner is used, as illustrated in figure 1. The vacuum cleaner 10 has its suction entrance connected to one of the passage holes 3 by means of a hose 11. Typically, the hose extends through the passage hole, and at its end within the working space the hose is provided with a nozzle to be able to locally suck up the generated dust. Then, this dust is sucked via the hose 11 to the vacuum cleaner 10, where it is collected in a dust bag in the usual manner.

SUMMARY OF THE INVENTION

It is a big problem that dust bags are indeed intended to collect and hold domestic dust, and do this well up to a certain extent, but they are not suitable to hold asbestos dust with the certainty needed. Furthermore, the entire design of an ordinary vacuum cleaner is not suitable for the purpose of sucking up asbestos in a safe manner. All in all, it boils down to the fact that the ordinary vacuum cleaner which is used in the above-described manner will blow a substantial amount of dust into the "clean" room, including a part asbestos dust. Since the other users of the "clean" room believe that the room stays clean, they will not take protective measures such as mouth masks, so that in fact they are exposed to asbestos dust without protection. Furthermore, after performing the work, the so-called "clean" room should actually be considered as "contaminated room", and should be decontaminated in its entirety.

Further, the usual vacuum cleaner has a problem in the area of disposal of the removed dust. At a certain moment, the dust bag is full and must be removed. To that end, in the case of the usual vacuum cleaner the housing of the vacuum cleaner is opened to take out the dust bag. In doing so, it will be inevitable that the bag is pinched, causing this bag to blow out an amount of air with a high concentration of asbestos particles into the clean room.

An objective of the invention is to provide a solution to the above-described problems.

According to an important aspect, the present invention provides a dust suction device which blows the sucked air back into the sealed "containment" space.

It is true that the entire pathway of suction and blowing back takes place outside the "containment" walls, but it is completely separated form the clean room. Absolutely nothing is blown out to the outside. In fact, the dust suction device can be considered to be an extension of the "containment" space.

This can in principle be achieved with hoses, and in principle suction and blowing back of the air can take place through separated passage holes 3. In a preferred embodiment, the housing of the dust suction device is coupled directly to a passage hole 3, and suction and blowing back of the air takes place through the same hole.

According to an important aspect, the present invention provides a dust suction device with a filter placed close the "containment" wall. If the filter is full, it can be taken out of the housing of the dust suction device from the inside of the

"containment" space, and in the same manner a new filter can be placed. The full filter thus remains in the "containment" space. Thus, also the step of exchanging the filter can take place in a safe manner.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, features and advantages of the present invention will be further clarified by the following description of one or more exemplary embodiments while referring to the drawings, in which same reference numerals indicate same or similar parts, in which indications "below/above", "higher/lower", "left/right" etcetera exclusively relate to the orientation shown in the figures, and in which:

Figure 1 is a schematic perspective view showing a shielding box;

Figure 2 is a schematic longitudinal cross section of a suction device according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Figure 2 schematically shows the design of an embodiment of a suction device 100 according to the present invention. The suction device has a housing 101 , comprising a tubular connection mouthpiece 110 with a free end 111 and an opposite inner end 112. The connection mouthpiece 110 typically is circular cylindrical, and has an outer diameter fitting to the diameter of a passage hole 3. Within the connection mouthpiece 110, preferably coaxially therewith, a for instance circular cylindrical separation wall 140 is arranged, with a free end 141 that may be recessed with respect to the free end 111 of the connection mouthpiece 110, and an opposite inner end 142, that may be arranged at the same axial position of the inner end 112 of the connection mouthpiece 110, and that may be connected thereto in an airtight manner, for instance by means of a sealing ring 143. The free end 141 of the separation wall 140 may be connected to the connection mouthpiece 1 10 by means of a ring 144 provided with passage openings.

The housing 101 has an outer mantle 120, with a diameter larger than the connection mouthpiece 110. The outer mantle 120 has a rear end 121 and an opposite front end 122, that partially overlaps the inner end 112 of the connection mouthpiece 110. At the rear end 121 , the outer mantle 120 is closed by an end plate 123. At some distance of the end plate 123, a partition 124 is arranged, extending over the entire diameter of the outer mantle 120. A motor space 125 is defined between the end plate 123 and the partition 124, having a motor 126 arranged therein.

Between the partition 124 and the inner end 112 of the connection mouthpiece 110, a cylindrical inner wall 130 is arranged, of which a rear end 131 connects to the partition 124, and of which a front end is connected to the inner end 112 of the connection mouthpiece 110 in an airtight manner. At some distance of the rear end 131 of the inner wall 130, a filter seat 150 is positioned. A pump space 155 is defined between the filter seat 150 and the partition 124, having arranged therein an air pump 156 driven by the motor 126, for instance a centrifugal pump.

A first filter space 145 is defined within the separation wall 140, in which a first basket filter 146 is arranged, which is in principle intended for holding all dust particles.

A second filter space 135 is defined within the inner wall 130, in which a second filter 136 is placed, which serves as additional certainty for catching possible particles which have passed the first filter 146. Preferably the second filter 136 is a HEPA-filter.

Between the inner wall 130 and the outer mantle 120, a first ring-shaped return channel 161 is defined, that communicates to the pump space 155 through openings in the rear end 131 of the inner wall 130. Between the separation wall 140 and the outer mantle 120, a second ring-shaped return channel 162 is defined, which communicates to the first ring-shaped return channel 161 through openings in the rear end 112 of the connection mouthpiece 110.

Operation is as follows. The connection mouthpiece 110 is introduced into a passage hole 3, while sealing means such as for instance an O-ring provide an airtight connection between the connection mouthpiece 110 and the containment wall concerned. The motor 126 is actuated to drive the pump 156. Air is sucked in by the pump 156 through the connection mouthpiece 110, more particularly through the separation wall 140, and reaches the pump space 155 through the first filter space

145 and the second filter space 135. In doing so, the sucked air passes the first filter

146 and the second filter 136 sequentially. From the pump space 155, the filtered air is forced out by the pump 156, through the first ring-shaped return channel 161 and the second ring-shaped return channel 162 between the separation wall 140 and the connection mouthpiece 110, and is thus blown out into the containment space.

When the first filter 146 is full, or needs to be exchanged for other reasons, from the containment space one places a lid on the entrance end of the first filter.

The first filter 146 can easily be taken out through the free end 111 of the connection mouthpiece 110, and is then placed in the containment space. In the same manner, a new filter is arranged in its place, and the suction device 100 is again ready for use. At no time at all has the inner space of the housing 101 been brought in

communication with the clean room outside the containment space.

It should be clear to a person skilled in the art that the present invention is not limited to the exemplary embodiments discussed above, but that several variations and modifications are possible within the protective scope of the invention as defined in the attached claims. For instance, the separation wall 140 does not have to be circular cylindrical, and the return channel 161 , 162 does not have to be arranged around the suction channel in a ring-shaped manner.

Even if certain features are mentioned in different dependent claims, the present invention also relates to an embodiment that has these features in common. Even if certain features are described in combination with each other, the present invention also relates to an embodiment in which one or more of these features are omitted. Features which have not explicitly been described as being essential may also be omitted. Possible reference numerals used in a claim should not be explained as being limiting to the scope of such claim.