In such apparatus a fluid with material, particularly particulate material, entrained therein is constrained to flow along a path along which the entrained particulate material becomes separated from the fluid, and the fluid passes to exhaust.

In addition, to vacuum conveyors for materials, examples of conveyor apparatus of this type includes so-called"cyclone separators", vacuum cleaners, insect collecting apparatus, spore separators, dust collectors such as those used in saw mills, flour mills, chimneys, paintshops, in "clean-rooms"for producing electronics equipment and in motor vehicles for removal of particulates in the exhaust gases or for air filters in air inlets such as for the removal of pollen from air entering into the passenger compartment.

It is not intended that the invention be limited to the above list; the invention finds equal utility in use with all vacuum conveyors and cyclone separators and in all apparatus where material entrained in a fluid is to be removed, separated and collected. Similarly, the fluid employed in such apparatus is generally air, but the present invention may be used equally well with other fluids. For convenience, in this specification such apparatus will be referred to as"conveyor apparatus"or"apparatus of the type described".

The present invention is particularly suited for use with vacuum cleaners, especially vacuum cleaners of the type which separate entrained particulate material from the airstream upstream of the collection vessel and may operate on the cyclone principle or be as described in International patent application No. W096/11047, or may have an inlet which is tangential or normal to the exhaust.

It is an object of the present invention to provide apparatus of the type described in which a non-porous, preferably disposable, bag may be used to line the collection vessel and accumulate the material previously separated from the fluidstream.

Accordingly, the present invention provides apparatus for conveying material entrained within a fluid, the apparatus comprising an inlet for material-laden fluid, separation means for separating material from the fluid, fluid exhaust means, means to apply a reduced pressure within the apparatus and a collection vessel for the material, in which the material collection vessel contains a non-porous flexible-walled bag and the apparatus includes means for applying a differential pressure between the inside and the outside of the bag to maintain the bag substantially in the open condition as separation progresses.

Such an arrangement is advantageous in that it permits the use of bags which are relatively less expensive than conventional collection vessels.

Preferably, the means for applying a differential pressure comprises a conduit in communication with the outside of the bag. The conduit may take the form of a fluid bleed line communicating between the outside of the bag and a low pressure section of the apparatus, thereby applying a lower pressure to the outside of the bag than the inside.

Alternatively, the means to apply a differential pressure may comprise an electric motor in driving engagement with fluid impeller. In such an embodiment, the electric motor/impeller arrangement is preferably in communication with the outside of the bag via a conduit.

Preferably, the conduit is flexible. However, the electric motor/impeller arrangement may be within the collection vessel and thereby act directly on the bag.

It will be understood that, with apparatus of the type described and in the absence of a blockage to the inlet, the differential pressure will generally be a reduced pressure which will be substantially compensated by an inflow of fluid through the inlet although the interior of the apparatus will generally be subject to a residual reduced pressure during operation. Hence, the differential pressure between the inside and the outside of the bag will generally be achieved by maintaining a lower pressure on the outside of the bag. Preferably, a variable low pressure is applied to the outside of the flexible-walled bag to prevent it from collapsing inwardly under the influence of the variable reduced pressure acting within the bag. Such residual pressure may act through the fluid bleed line.

The apparatus may be contained within a housing. Where the apparatus is contained within a housing, the conduit is preferably disposed externally of the main housing of the apparatus although an internal disposition is possible, suitable provision being made for passing the conduit from the interior to the exterior of the bag with fluid sealing. Alternatively, part of the conduit may be routed internally of the housing and passed to the outside for final connection through the wall of the collection vessel, suitable sealing means being provided.

Preferably, the conduit is operatively connected to the base of the collection vessel, that is, opposite to the mouth thereof. A fluid distribution means such as a mesh or grill is preferably disposed between the inlet of the conduit and the bag, to distribute the reduced pressure over the base or other substantial area of the bag and to prevent the conduit from becoming blocked by the bag. Preferably, the inlet end of the conduit is removably attached to the collection vessel to assist in cleaning. Removable attachment means may comprise a bayonet or a broken-thread connector with suitable resilient sealing means.

Optionally, an obturator means is provided in the exhaust means upstream of the motor to increase the overall pressure drop across the apparatus and to enhance the fluidstream speed through the apparatus.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawing, which is a sectional view in diagrammatic form of an embodiment of the invention employing a fluid bleed line.

With reference to the drawing, a vacuum cleaner apparatus of the type described in W096/11047 consists essentially of an inlet 11 for a fluid with material entrained therein and an outlet 12 for exhaust fluid. A motor (not shown) with an impeller draws fluid through the apparatus in the direction of the arrows and vanes 13 disposed within the inlet passage 11 impart a swirling or vortical motion to the fluid. An expansion chamber 14 is located downstream of the vanes 13; the material entrained in the inlet fluid is urged under the vortical flow towards the periphery of an expansion chamber 14 where the material loses energy and is deposited in collection vessel 15 through duct 16. An optional flow restrictor 20 may be provided as part of the outlet.

The collection vessel 15 is detachable from duct 16 and contains a flexible bag 17 made, for example, from polyethylene. The bag 17 is removable from the collection vessel 15 on removal of the latter from the duct 16 and the bag 17 may then be removed and replaced with a fresh one.

The mouth of the bag is sealingly trapped against the rim of the collection vessel 15 on engaging the latter on the end of the duct 16. A suction tube 18 connects the outlet 12 with the base of the collection vessel 15; the base of the vessel 15 carries a gauze 19 which separates the bag 17 from the end of the suction tube 18.

In use, the interior of the collection vessel 15 is subject to reduced pressure from the outlet 12 of the apparatus through the suction tube 18 and the bag 17 is thereby drawn towards and preferably into contact with the inside wall surface of the collection vessel 15. When the bag becomes filled with material, it may readily be removed.