Background of the Invention

The present invention relates to cyclonic chambers for vacuum cleaners. The invention more particularly, although not exclusively, relates to a first stage cyclonic chamber having improved efficiency , whereby fine particles are recirculated into the air stream for more efficient particle separation .

Known primary cyclonic vacuum chambers have a cylindrical chamber with a tangential inlet port. A disc is placed below the inlet port to block the upward flow of lighter particles and direct them around the disc through perforations or a filter medium. The latter become blocked with fine particles thereby reducing the suction efficiency of the vacuum cleaner .

Object of the Invention

It is an object of the present invention to overcome or substantially ameliorate the above disadvantage and/or more generally to provide a first stage cyclonic chamber having improved particle separation efficiency .

Disclosure of the Invention

There is disclosed herein a vacuum cleaner cyclone , comprising:

a chamber having a substantially cylindrical outer wall;

an entry port extending substantially tangentially of the outer wall into the chamber so that air entering the chamber via the entry port induces a cyclonic airflow within the chamber;

an exit passage at an upper portion of the chamber and spaced radially inward of the outer wall ;

a first disc situated below the exit passage and including a filter screen; and

a second disc concentric with and spaced above the first disc to define an annular space between the first and second discs , which annular space has a circumferential return passage via which fine particles having passed into the annular space via the filter screen can return to the chamber .

Preferably, the annular space between the first and second discs converges toward the circumferential return passage . Preferably, the first disc has a downwardly depending first peripheral lip .

Preferably, the second disc has a downwardly depending second peripheral lip.

Preferably, the circumferential return passage is situated substantially between the first and second peripheral lips .

Preferably, the exit passage includes a filter screen.

Definition

As used herein the term "filter screen" is intended to encompass filtration elements such as but not limited to mesh, filter paper, gauze, or perforated sheet such as plastics or metal for example. A "fine filter screen" is a filter screen with smaller apertures or interstices . Brief Description of the Drawings

A preferred form of the present invention will now be described by way of example with reference to Fig. 1 which is a schematic cross-sectional elevation of a vacuum cleaner cyclone .

Description of the Preferred Embodiment

In the accompanying drawing there is depicted schematically a vacuum cleaner cyclone 10. The cyclone 10 comprises a primary chamber defined predominantly by a substantially cylindrical wall 11. Positioned radially inward of the cylindrical wall 11 is another wall having an exit passage 14 across which a filter screen is situated. This filter screen stops the passage of larger dust particles so that they fall therefrom back into the chamber. An annulus 13 is defined between the exit passage 14 and the cylindrical wall 11.

A tangential inlet or entry port 12 extends to the cylindrical wall 11 so that air entering the annulus 13 instigates a cyclonic flow therein. A vacuum pump would be connected downstream of a main exit port 23 to induce this airflow.

Downstream/internally of the exit passage 14 are secondary cleaning stages 16 which are not important to the present invention and will not be described.

A first (lower) disc 17 is positioned below the exit passage 14 and includes a fine filter screen. Outboard of the fine filter screen is a downwardly depending peripheral lip 18.

A second (upper) disc 19 is positioned above the first disc 17 and has a conical shape which together with the first disc defines a tapered annular space 21. The outer circumference of the second disc 19 is also provided with a downwardly depending peripheral lip 20. Moreover, the annular space 21 takes the form of an outwardly converging venturi having a narrow circumferential return passage defined between the peripheral lips 18 and 20.

Dirt-laden air enters the annulus 13 via the entry port 12 and spins along the inner side of the cylindrical wall 11. Heavier particles fall to a containment area 15 at the bottom of the chamber . The lighter particles in the air flow at the bottom part of the chamber consisting of hair, carpet fibres and dust follow a path which tends to converge toward the centre and migrate vertically upward.

The particle-laden air that moves vertically upward meets the first disc 17. Here the fine filter screen holds the majority of the larger particles as well as fibres, hair and such like . Finer particles pass upwardly through the fine filter screen into the annular space 21 whereupon they encounter the bottom surface of the upper disc 19. Downward airflow past the return passage 22 induces outward migration of the fine particles by suction from the annular space 21. Due to the outwardly convergent nature of the annular space 21 which is somewhat like a venturi , the particles accelerate outwardly toward the return passage 22 whereupon they are returned to the chamber. The lighter portion of this particulate material is drawn upward to the exit passage 14, but the heavier portion is returned to the bottom of the chamber due to the downward airflow. These are particles which in the prior art would be drawn directly into the secondary cleaning stages . It should be appreciated that modifications and alterations obvious to those skilled in the art are not to be considered as beyond the scope of the present invention. For example, the inlet port 12 might be situated below the exit passage 14.