GB2341117A

GB2341117A - Dust sampling device

Info

Publication number: GB2341117A
Application number: GB9916892A
Authority: GB
Inventors: Da Costa Maria Da Co Cerqueira; Ralf Ernst Loeser; Rainer Polzius; Uwe Wortmann; Thomas Wuske
Original assignee: Draeger Sicherheitstechnik GmbH
Current assignee: Draeger Safety AG and Co KGaA
Priority date: 1998-09-01
Filing date: 1999-07-19
Publication date: 2000-03-08
Also published as: GB9916892D0

Abstract

To collect a sample of dust from household or workplace for allergy testing, a filter disc 4, Fig 2, is arranged across a tube 1 which carries a sample container 62 and can be connected to a vacuum cleaner (not shown). The dust sample is deposited on the filter disc 4 and then falls by gravity into the sample container 62 which can be removed for testing of the contents. Alternatively, Fig 4, the tube 1 has a tapering flow channel 121 and a sampling element 132 which is inserted through an access aperture (141) and held in guide members 142. Air drawn in by the vacuum cleaner is accelerated in the flow channel 121 and then deflected around the sampling element 132. Dust is thus deposited by inertia on a filter fabric or medium in cavity 62.

Description

2341117 Device for dust sampling The invention relates to a device for

dust sampling.

A device of the type in question is described in EP 0 765 627 A2. Operation of this device is complicated and inconvenient, especially when system components become clogged due to the dust collection procedure.

Because of the increase in dust-related illnesses in people who are exposed to dust in domestic or work surroundings, dust samples from the area in question are examined analytically, increasingly also by those affected, for instance by using test kits which are easy to use. An analysis procedure which is particularly suitable for examinations of this kind is described in DE 198 08 598.2-52, which thus adds to the present dust-sampling device of the invention as regards the chronologically following dust analysis.

In this connection there is a need for a suitable device for obtaining dust samples using a vacuum cleaner generally present in every household or every work place.

Accordingly embodiments of the invention aim to provide an improved device for dust sampling which on the one hand is easy to operate, and on the other hand makes specific and reproducible sampling possible.

According to one aspect of the invention, there is provided a device for sampling dust from an air flow, in a tube having a cavity for receiving the dust sample, characterised in that a filter disc not permeable to the dust sample is arranged transversely to the air flow, and the cavity is removably secured over an aperture on the tube wall and is arranged in the air flow direction in front of the filter disc so that the cavity receives the dust sample deposited on the filter disc by means of gravity.

The invention also provides, in another aspect, a device for sampling dust from an air flow, in a tube having a cavity for receiving the dust sample, characterised in that in an inflow region of the tube there is a flow channel which tapers in the air flow direction, and a subsequent sampling element having the cavity and a filter medium contained in it, the sampling element with the cavity being removably arranged transversely in the tube at a distance from the outlet-side end of the flow channel, and taking in only a part of the cross-sectional surface of the tube, so that the sampling is effected by deposition of the dust sample in the cavity due to the deflection of the air flow around the sampling element.

An essential advantage of embodiments of the invention is that the cavity used and its arrangement provides controlled collection conditions both with regard to the dimensional fraction and the total amount of the dust sample taken.

Further, preferred features may be found in the dependent claims, to which reference should now be made.

Embodiments of the invention will now be described by way of example only, with reference to the accompanying diagrammatic drawings, in which:

Figures 1, 2, 3 are different views and a section of a first exemplary embodiment of the invention, and Figures 4, 5 are, respectively, a section and a side view of a second exemplary embodiment of the invention.

-Like references have been used for like components.

The first exemplary embodiment (Fig. 1, 2, 3) relates to a first device of the invention in which the air flow with the conveyed dust strikes a filter medium. The air passes through the filter medium, and the desired dust fraction is separated at the filter medium.

The second exemplary embodiment (Fig. 4, 5) relates to a second device of the invention in which the air flow is deflected through a flow obstacle, and the dust particles are deflected not to the same degree so that they are deposited at the flow obstacle.

A first solution according to the invention for a device for dust sampling comprises a tube 1 in the form of a special vacuum cleaner nozzle at the inlet end 11 of which there is an (optional) coarse filter 2 (mesh width 0.2 to 5 mm), whilst the outlet end 12 is.

conically stepped in order to fit onto suction tube ends of different diameters. To improve the suction properties the inlet end 11 of the tube 1 may extend conically, or be bevelled or flattened. A flow channel 16 is thus produced through which there is a flow from the inlet end 11 to the outlet end 12.

Approximately in the middle of the tube 1 there is a separating point 3. The two tube portions 13, 17 are connected by means of a film hinge 31. After releasing two securing elements 32 the parts can be opened out (Figure 2). In the vacuum-cleaner-side tube portion 13 there is a retaining grid 14 and a filter-receiving groove 15 extending about the circumference of the separating point (Figure 3). In the suction-side tube portion 1.7 there is an edge 18 encircling complementary to the filter-receiving groove 15.

A filter disc 4, made, for instance, of paper, is inserted into the opened-out tube arrangement, and when the tube arrangement is folded together and fixedly closed it is retained at its outer edge by means of the securing elements 32. During a suction procedure the filter disc 4 can be supported on the retaining grid 14 whilst the dust which passes through the coarse filter 2 is deposited on its nozzle-side surface.

on the side of the tube portion 17 opposite the film hinge 31 there is a plug or screw connection 61 which is used for securing and receiving a cavity 62 for dust. The connection 61 is provided with an aperture 63 which opens directly in front of the filter disc 4 into the flow channel 16. During the suction procedure or occasional breaks the dust deposited on the filter disc 4 falls through the aperture 63 into the cavity 62, possibly aided by a simple tap by the user. The depositing of dust is made easier by rounding of the edges and a flowing shape at the outlet point of the aperture 63 into the flow channel 16. The preferably transparent wall of the cavity 62 makes it is possible to control the already collected amount of dust.

An improvement in dust separation into the cavity 62 can be achieved by inclining the filter disc 4 transversely to the air flow direction in the range of from 900 (i.e. perpendicular to the air flow direction) up to about 300, with corresponding positioning also of the separating point 3 and the associated securing elements 32 and the retaining.grid 14. This inclining has to be designed so that the aperture 63 is located on the side of the filter disc 4 lying furthest in the direction of the outlet end 12. As a result of the inclining, during the suction procedure the air flow already produces forces on the dust particles which act tangentially to the filter surface and thus convey the dust in the direction of the cavity 62.

If there is a sufficient amount of dust in the preferably transparent cavity 62 (recognisable by marking), then the user can remove or unscrew it in order to convey the contents for further analysis, in particular biochemical analysis.

one variant provides for the cavity 62 to be located in a sampling unit, which is inserted, for instance, into the tube portion 17 from the side so that the cavity 62 is positioned at the point where the aperture 63 opens in the tube 1. When the sampling unit is removed, excess dust is wiped off so that the same amount of dust is always conveyed for analysis.

If there is too little dust in the cavity 62 then the sampling unit can be re-inserted and the necessary amount be achieved by further suction.

By varying the material used for the filter disc 4, the composition of the collected dust can also be affected to a certain extent; the finer the pores of the filter material, the smaller also are the collected dust particles (which otherwise would pass through the filter disc 4 in the direction of the vacuum cleaner).

on the other hand, an open-pored, soft surface may lead to smaller dust particles not being released from the filter disc 4 even when the vacuum cleaner is stationary, and with tapping.

A further variant provides for the aperture 63 of the cavity 62 not to be arranged exactly at the point which is next in the direction of flow towards the vacuum cleaner, but at the furthest point. This can be advantageously achieved by the incline of the filter disc 4 being appropriately varied. It is true that on the one hand this leads to no dust falling into the cavity 62 during the suction operation, but on the other hand when the vacuum is at a standstill and possibly with a gentle tapping, the collected dust along the filter disc 4 falls into the cavity 62.

In the same way as the first solution, a second solution of the invention (Fig. 4, 5) for an impacting dust sample collector consists of a special vacuum nozzle with an inlet end 11 having a coarse filter 2 and a conical outlet end 12 which fits onto conventional vacuum cleaner tubes (30 to 45 mm.

diameter) Here also the inlet end 11 can be of pointed, inclined and/or conical design to improve operation and suction properties.

In the embodiment of dust sample collector described here, the drawn-off, dust-containing air is conveyed through a flow channel 121, whose cross section tapers in the course of its length (1 = 10 to mm) in the ratio a/b (a/b = 1 to 4). On the outlet side end of the flow channel 121 there is the cavity 62 of a sampling element 132 having a filter medium or filter fabric contained in it for receiving the dust sample at a distance d from the channel end of the flow channel 121 (d = 1 to 25 mm). The diameter of the cavity 62 and the cross-section b of the flow channel 121 are in the ratio 0.5 to 2.

The sampling element 132 is inserted through an access aperture 141 in the tube 1, and is received and positioned on the opposite side of the tube 1 in guide members 142. Through its position it forms the flow obstacle necessary for impaction.

The contours of the access aperture 141 and the cross-section of the sampling element 132 are designed such that sampling element 132 can be introduced only in one specific way so that the cavity 62 in the provided position is positioned with reference to the end of the flow channel 121.

In operation of the dust sample collector the air drawn in by the vacuum cleaner is accelerated in the flow channel 121 in order then to be sharply deflected at the outlet-side sampling element 132 and to flow round it. A portion of the dust particles present in the air collects due to mass inertia in the cavity 62, and is deposited with a filter medium or filter fabric for receiving the dust sample in the sampling element 132. Coarse dust components have already been retained by the coarse filter 2. To ensure a minimum air flow, either the coarse filter 2 is cur-ved outwardly or the front end of the tube 1 is provided with recesses so that the intake aperture cannot be completely closed.

When the sampling element 132 is withdrawn from the access aperture 141 excess dust possibly present in the cavity 62 is wiped off the contour 143, so that in this way conditioning of the dust content can take place on the one hand and provided that there is a minimum collecting period control of the collected amount of dust by the user can be eliminated on the other hand.

A variant of the second solution of the invention for an impacting dust sample collector provides for one or more air outlet apertures in the region of or near the cavity 62 to be located on the rear of the sampling is element 132, i.e. opposite the cavity 62: the differential pressure occurring through the air flow in the tube 1 on the sampling element 132 produces a small throughflow of the filter medium or filter fabric located in the sampling element 132, thus improving separation of the desired size fraction of the dust particles. The air outlet apertures in the sampling element 132 can either be constructed so that they are located directly opposite the cavity 62, or laterally offset, possibly on the other side of the filter medium or filter fabric, so that the air flow in the filter medium or filter fabric is deflected, additionally to the outer deflection of the air flow round the sampling element 132. The essential advantage of the last described dust sample collector variants is that the collected dust is directly deposited on the filter medium or filter fabric in the cavity 62 where it is required for the subsequent analysis.

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Claims

1. Device for sampling dust from an air flow, in a tube having a cavity for receiving the dust sample, characterised in that a filter disc not permeable to the dust sample is arranged transversely to the air flow, and the cavity is removably secured over an aperture on the tube wall and is arranged in the air flow direction in front of the filter disc so that the cavity receives the dust sample deposited on the filter disc by means of gravity.

2. Device for sampling dust from an air flow, in a tube having a cavity for receiving the dust sample, is characterised in that in an inflow region of the tube there is a flow channel which tapers in the air flow direction, and a subsequent sampling element having the cavity and a filter medium contained in it, the sampling element with the cavity being removably arranged transversely in the tube at a distance from the outlet-side end of the flow channel, and taking in only a part of the cross-sectional surface of the tube, so that the sampling is effected by deposition of the dust sample in the cavity due to the deflection of the air flow around the sampling element.

3. Device according to claim 1 or 2, characterised in that on the input side in the air flow direction the tube has a decreasing inner diameter, and/or on the output side in the air flow direction an increasing inner diameter and/or a decreasing outer diameter.

4. Device according to claim 3, characterised in that the tube is constructed to be stepped on the outlet side.

-g-

5. Device according to any of claims 1 to 4, characterised in that the inlet end of the tube is provided with a coarse filter permeable to the dust sample.

6. Device according to any of claims 1 to 5, characterised in that the wall of the cavity is made of a transparent material and/or has one or more markings to indicate the filling state of the dust sample.

7. Device according to any of claims 1 to 6, characterised in that the tube in the region of the filter disc or in the region of the sampling element has a separating point with removable securing is elements.

8. Device according to any of claims 1 to 7, characterised in that the filter disc is arranged in a range of from 90 degrees to 30 degrees with respect to the air flow.

9. Device according to any of claims 1 to 8, characterised in that the filter disc is retained with a retaining mesh. 25

10. Device according to any of claims 1 to 8, characterised in that the cavity is connected to the tube by means of a plug or screw connection.

11. Device according to any of claims 1 to 8, characterised in that the cavity in the form of a slide element is pushed from the side into a holding means on the tube and is connected to the aperture. 35

12. Device according to claim 2, characterised in that the sampling element is constructed with the cavity in the form of a slide element and is positioned in guideways in the tube.

13. Device according to claim 2 or 12, characterised in that on the.rear side opposite the cavity and turned away from the air flow the sampling element has one or more air outlet apertures, so that there is a small amount of air throughflow of the filter medium in the sampling element, and so deposition of the desired dimensional fraction of dust particles is increased.

14. Use of a device according to at least one of the preceding claims as a slip-on portion for a vacuum cleaner. is

15. A device for sampling dust from an airflow, the device being substantially as herein described with reference to the accompanying drawings.