The present invention relates to a telescopic device for inclusion in a suction line of a suction arrangement intended for the extraction of gases or other environ¬ mentally hazardous gases from at least one working or contaminated area, for instance from the exhaust pipe of a motor vehicle, a welding location or some other work place in which environmentally-harmful and/or health- hazardous gases may be generated in one form or another. The suction line is connected to a central suction gas extraction plant or to a gas extractor fan.

Gas extractors are used in car workshops, car inspection localities and car repair shops, which may be intended for other types of automotive vehicles than cars, lor¬ ries and buses, for instance such vehicles as tractors, forestry machines and agriculture machines, for extract¬ ing by suction exhaust gases from the vehicle engine while test-running the same and/or when bench-testing engines indoors. Extractors can also be used in work¬ shops and laboratories for removing by suction environ¬ mentally-harmful gases and vapours generated in work areas in such localities, for instance welding gases from welding shops and gases arising from cutting ma¬ chines. These extractors normally include a flexible suction hose having fitted to one end thereof a suction nozzle or device by means of which the hose can be connected to the exhaust pipe of a combustion engine vehicle or to a collecting box or the like mounted above a working place. In order to be able to connect the hose to the exhaust pipe of a vehicle, it is necessary for the hose extension that carries the hose connector to have a given length, the greater the length of the suction hose, the greater the range of the extractor arrangement. When the extractor is not in use, it must

be possible to remove the suction hose in some way or the other, so that the hose will not remain hanging with part of the hose possibly lying on the floor and consti¬ tuting an obstacle to some other activity in the work- shop or locality concerned.

It is known that this problem can be avoided by reeling the suction hose onto a ceiling-mounted or wall-mounted drum from which requisite lengths of hose can be reeled off and connected to the exhaust pipe of a vehicle. These drums are normally provided with a so-called spring return, i.e. are fitted with a powerful spring which when unreeling the hose from the drum is tension to such an extent that it is able to rotate the drum automatically in a direction in which the withdrawn length of hose is automatically reeled onto the drum after use. However, in order to enable a withdrawn length of hose to be reeled automatically back onto the drum after use, it is necessary to provide this type of extractor or suction arrangement with a very powerful spring, meaning that a very high force must be applied manually to the hose in order to unwind the hose from the drum, particularly if all of the hose is to be unwound. Furthermore, if the hose is not unreeled to its full extent, since it is seldom that the full hose length is required, the increased resistance to flow created by length of hose that remains coiled on the drum will impair the suction ability of the extractor arrangement.

Because of these drawbacks among other things, this type of exhaust-gas extractor has become less and less popu¬ lar and has, to a large extent, been replaced with extractor arrangements in which the, actual suction hose is extendable and retractable from within a tubular housing which is either hung from a main suction line or

is carried by a substantially horizontal, wall-mounted and pivotal carrier bar and is connected to a suction fan or to a main suction line that forms part of a central gas extraction system. The inner end of the suction hose located within the tubular housing is sealed with the aid of a piston-like sealing device so that when the connector device is closed and suction is applied, the hose will be subjected to a subpressure which effectively assists in retracting the withdrawn length of hose to a predetermined position within the tubular housing at which the hose will constitute no obstacle to any other activity. In order to achieve a requisite subpressure for drawing the hose into the tubular housing, it is necessary to provide the hose connector or hose nozzle with a sealing cap or a throt¬ tle means which will function to seal the hose connector when the connector is disconnected from an exhaust pipe, this hose-connector or nozzle covering creating the subpressure required to retract the suction hose into its tubular housing.

The aforesaid telescopic principle has been found both simple and reliable for removing the hose connector means or the suction nozzle from the actual work place, and has consequently been used to an ever-increasing extent within the field in question. Hitherto, there has normally been used a steel tube as an outer part and a flexible hose as an inner part of a telescopic device, and it is known to use a subpressure or a spring for returning the inner part of the telescopic device into its outer part. Despite various attempts, no success has been met with hitherto in producing a well-functioning telescopic suction extractor whose telescoping parts can all be made of tubing. The reason for this is primarily because of the lack of success in achieving satisfactory stability between the different components of the tele-

scopic device and in achieving self-locking of said components in a simple fashion, such that the telescopic device will remain stably in an extended and a collapsed state.

Consequently, the object of the present invention is to provide a solution to this problem and therewith provide telescopic exhaust-gas extractors which include two or more telescoping tubes. This object is achieved with the inventive device having the characteristic features set forth in the following Claims.

The present invention will now be described in more detail with reference to an exemplifying embodiment thereof and also with reference to the accompanying drawings, in which Figure 1 illustrates an inventive telescopic device in perspective; Figure 2 illustrates in perspective and partly in section a slide bearing for mounting one telescopic part in its outer part; and Figure 3 illustrates a further application of the inven¬ tive telescopic device.

Figure 1 illustrates an inventive telescopic device, identified generally by reference l, which may be incor- porated in or form a part of or form the actual suction line of an extractor arrangement for extracting by suction exhaust gases or other environmentally-harmful gases from at least one work place, wherein the extrac¬ tor suction line is connected, in a known manner, to a central extractor plant or to a suction fan, although not shown in the drawings. Only a part 2 of an extractor suction line connected to a central extractor plant or to a suction fan is shown in the drawings.

The illustrated embodiments of the inventive telescopic device include an outer tube 3 which is shown to be a

continuation of the suction line 2, and an inner tube 4 which is mounted for movement in the outer tube 3 and which has a connector means 5 or suction nozzle mounted on its outer end. The outer tube 3 and the inner tube 4 may both be made of steel tubing, sheet-metal tubing or plastic tubing.

In order to enable the inner tube to be moved axially in relation to the outer tube 3, the outer orifice or outer end 6 of the outer tube 3 is provided internally with a slide-bearing bushing 7 which is made of a low-friction material, such as a plastic or metal. The bushing 7 is slotted along the whole of its length and is anchored in relation to the outer tube 3 in some appropriate manner.

That part of the telescopic device which can be moved axially in relation to the tube 3, i.e. the inner tube 4 in the case of the illustrated embodiment, is supported for both axial movement, as shown by the double arrow 8, and rotary movement, as shown by a double arrow 9, of said bushing 7, and will preferably therefore have an axial extension such as to ensure that the tube will not stick or jam when the inner tube is fully extended. So that desired friction can be obtained between the inner tube 4 and its bushing 7, the bushing can be adjusted with the aid of a number of screws 10, since greater parts of the bushing 7 are loosely disposed in relation to the outer tube 3. Thus, when screwing-in the adjuster screws 10, those parts of the bushing which are loose in relation to the outer tube 3 can be urged by screws 10 inwards against the inner tube 4, therewith also chang¬ ing, i.e. increasing, the frictional forces that act between the bushing 7 and the inner tube 4. This enables the friction forces acting between the bushing 7 and the inner tube 4 to be adapted so that the inner tube 4 will remain stable in a fully or partially extended position,

even when the telescopic device extends vertically in use. The inner tube 4 is provided at its inner end with a stop flange 14 which will prevent the inner tube 4 from being withdrawn through the bushing 7.

The bushing 7 may have the form of a sleeve and may be a one-piece structure, as illustrated with the exemplify¬ ing embodiment of the present invention. Those parts of the bushing which face away from the screws 10 may be affixed to the outer tube 3 as by gluing or in some other known way. Alternatively, the bushing 7 may com¬ prise two halves of which one is connected to the outer tube 3 and the other is connected solely by the adjuster screws 10.

Figure 3 illustrates an embodiment in which the suction hose includes a swivel 11 by means of which the inven¬ tive telescopic suction device can be swung through 360° in the horizontal plane, as indicated by an arrow 12, and with which the inventive telescopic device is provided with a moveable or fixed hose connector or nozzle 13.

It will be understood that the present invention is not restricted to the aforedescribed and illustrated embodi¬ ments and that changes and modifications can be made within the scope of the inventive concept defined in the following Claims.