It is to be understood that such dust and dirt separation may be achieved entirely by passage of dirty air tlu-ough one or more filter elements, or partly by passage of the air through other separation devices, such as a cyclone, and partly by passage through one or more filters, and the assembly in accordance with the present invention may be used alone or in combination with other filters or other separation devices.

Dust filter elements by their very nature tend to become clogged by the dust they are designed to collect and there have been various proposals for mechanisms intended to shake or otherwise agitate filter elements for the purpose of dislodging collected dust therefrom.

By way of example, EP-A-860554 discloses the use of an inteimittently powered actuator to operate an element which moves a filter in a self-propelled street sweeping machine to shake the filter and remove collected dust ; GB-A- 1471035 discloses a vacuum cleaner with a solenoid operated shakel-which is activated by a pressure switch in response to a drop in exhaust air pressure caused by partial blockage of the filter ; US-A-5090083 discloses a commercial carpet cleaner with filter tubes that are normally maintained in an extended state by means of springs which are compressible under the action of a manually operable depressor plate so as to enable the filter tubes to be shaken, thereby allowing the collected matter to fall into a hopper : and US-A-5681363 discloses a filter shaking arrangement in which a vacuum cleaner dust bag is held within an elastically deformable frame which is expanded by virtue of air pressure in the filter bag, so that when the airflow is intelTupted elastic contraction of the frame shakes the bag to dislodge dust from the filter material. lt is an object of the present invention to provide a simple and effective mechanism for dislodging dust from a filter element and into a dirt collection chamber, particularly in a vacuum cleaner.

According to a first aspect of the invention there is provided a dust and dirt separation assembly having a dirt collection chamber, a dirty air inlet and a clean air outlet with an airflow path therebetween, the air flow path passing through a first separation means for separating larger particles of dirt from the dirty air such that it is collected in the dirt collection chamber, and a second separation means for separating smaller particles of dust from the dirty air, wherein the second separation means is a filter element and the assembly further includes a striker member which is activatable to strike the filter element to dislodge the dust from the filter element and such that the dust is collected in the dirt collection chamber with the larger particles ofdiit.

Preferably the first separation means is a cyclonic separator.

The filter element may comprise a filter body made of a filter material which has non-stick propelties to facilitate separation of the dust from the surface thereof the filter element is struck. Conveniently the filter material has a coating of PTFE or the like.

Preferably the filter element further comprises an impact member on which the striker member impacts when striking the filter element.

Ideally, when the filter element is struck by the striker member, the dust falls down into the dirt collection chamber and mixes with the larger dirt already collected there.

The striker member may be disposed in said airflow path so as to be movable in response to airflow in said airflow path and to be held in spaced relation to said filter element, but allowed to impact on said filter element when said airflow ceases so as thereby to dislodge the dust from said filter element.

Further the striker member may be held in spaced relation above said impact member by the airflow and allowed to fall gravitationally onto said impact member when airflow ceases.

The assembly may funther comprise a guide tube which forms part of the airflow path downstream of said filter element within which said striker member is located. The guide tube preferably includes a constriction through which said striker member can pass with a clearance such that the striker member is held in a substantially stable position relative to said constriction for a wide range of airflows.

In such embodiments the striker member is preferably of generally spherical form and the guide tube is of generally cylindrical form.

In an alternative embodiment the striker member comprises a resilient element arranged in an over-centre mechanism.

The resilient element may be spaced from the impact member until actuated, when it passes through an over-centre condition and strikes the impact member before returning to its original position.

Conveniently the assembly funther comprises an actuation member which is manually operated to engage the resilient element and cause it to be displaced through the over-centre condition.

The dilt collecting chamber may be releasably secured by catch means to enable removal for emptying, and the activation member may be activated when the catch means re released.

According to a second aspect of the invention there is provided a filter assembly comprising a filter element and a striker member which is arranged to be movable so as to strike the filter element to dislodge the dust from the filter element.

According to a third aspect of the invention there is provided a filter assembly comprising a housing having an air inlet and an air outlet, a filter element disposed in an airflow path between said air inlet and said air outlet, a striker member disposed in said airflow path so as to be movable in response to airflow in said airflow path and to be held in spaced relation to said filter element, but allowed to impact on said filter element when said airflow ceases to dislodge dust from said filter element.

According to a funther aspect of the invention there is provided a filter assembly comprising a housing having an air inlet and an air outlet, a filter element disposed in an airflow path between said air inlet and said air outlet, a striker member arranged to be held normally in spaced relation to said filter element, and being movable into contact with the filter element and, an actuating member to cause said striker member to move into contact with, and impact on, said filter element so as to dislodge dust from said filter element.

According to a still funther aspect of the invention there is provided a vacuum cleaner including a dust and dirt separation assembly or a filter assembly according to the any of the previous aspects of the invention.

The invention will now be described by way of example only with reference to the accompanying drawings in which : Figure 1 diagramatically illustrates a first embodiment of dirt and dust separation assembly in transverse section ; Figure 2 diagramatically illustrates a second embodiment of dirt and dust assembly in transverse section ; Figure 3 is a top pln view cowesponding to Fiure 2, and Figures 4 and 5 illustrate the action of a fitter cleaning mechanism of the second embodiment.

Refewing to Figure l, a din and dust separating assembly 10 as illustrated is formed as a unit for incorporation in a vacuum cleaner apparatus in the air-flow path between a suction head, which is adapted to pick up dirt and dust from a surface being cleaned, and a source of suction, such as a motor-driven impeller disposed within the apparatus or externally thereof. The assembly 10 comprises an outer housing 11 with a tangentially arranged air inlet 12 at the upper end thereof and an axially located air outlet 13 formed in a top wall 14. At its lower end the housing I 1 affords a downwardly directed discharge outlet 15 leading to a dirt collection chamber 16, which for emptying may be removable from the outer housing 11, or have a bottom closure flap which can be opened or removed.

The outer housing 11, with the tangential air inlet 12, acts as a first separator having a cyclonic action such that larger particles of dirt or other debris in the air entering through the inlet 12, as shown by arrow A, are separated from the airflow and fall into the dirt collecting chamber 16 through the discharge outlet 15.

A second separator in the form of a filter element 20 is disposed centrally within the outer housing 10, and may be located in an inner housing (not shown) generally in the manner of the Figure 2 embodiment described below. The filter element comprises a generally frusto-conical (or cylindrical) filter body 21 formed from pleated filter material which has secured thereto at its lower end a bottom closure plate 22 whereby dirty air, after entering through air inlet 12 and circulating around the outer housing H, is constrained to flow through the filter body 21 and to the air outlet 13, through an opening 23 formed in a top closure plate 24 also secured to the filter body. Thus smaller particles of dust still contained within the airflow after the first stage of separation by the cyclone are entrapped on the filter body 2].

In accordance with the invention a striker mechanism 30 is provided to produce an impact on the filter element in such a manner as to shake the body 21 of filter material briefly and thereby dislodge the collected dirt. In the embodiment shown in Figure I, this is arranged to occur automatically when airflow through the assembly 10 ceases. For this punpose, a striker member 31 is provided. Adjacent to the air outlet opening 23 in the top plate 24 and depending therefrom there is a short tubular body 32 with an annular end plate 33 spaced downwardly fi-om the air outlet opening 23. The annular end plate 33 defines a central opening 34 of a diameter such as to allow the striker member 31, which in the illustrated embodiment is of hollow spherical form, to pass through with limited clearance.

A guide tube 35 extends downwardly from the end plate 33 and terminates at a position spaced above the bottom closure plate 22 of the filter element 20. As can be seen, the internal diameter of the guide tube 35 is substantially greater than that of the central opening 34. The arrangement is such that airflow passing into the interior of the filter element 20 through the filter body 21 is constrained to flow around the lower end of the guide tube 35 towards the air outlet 13. Initially, the spherical striker member 31 will rest on the bottom closure plate 22, but the airflow through the guide tube 35 is such as to lift the striker member 31 towards and tlu-ough the opening 34 and into the tubular body 32, as illustrated. Because the clearance between the striker member 31 and the opening 34 is limite, the striker member 31 will be held in substantially the same position over a wide range of airflow rates while the assembly 10 is in operation.

However, when the airflow ceases the striker member 31 is allowed to fall gravitationally and impact on the bottom closure plate 22 so as to apply a brief shaking movement to the filter body 2l, theleby dislodging dust from the exterior surface thereof to fall through the discharge outlet 15 into the dirt collection chamber 16 which already contains the larger particles of dirt. The fine dust falls into the larger particles of dirt and to some extent mixes with them, rather than lying as a separate layer. This provides a veiy significant and practical avantage when the dirt collection chamber 16 is emptied, as the fine dust is less likely to fly up as a cloud to engulf the person emptying the chamber making the process cleaner and more pleasant than previously.

It will be understood that airflow through the assembly 10 is normally generated by a motor-driven impeller which is arranged downstream of the air outlet 13 (either withil the body of the apparatus Ol externally thereto for connection to the apparatus in any convenient manner) to draw air from a suction cleaning head (not shown) when the assembly 10 is incorporated in a vacuum cleaner apparatus, and that normally a cleaning operation is terminated by de-energising the motor which drives the impeller. However, the impeller does not stop instantaneously, but slows down over a period of several seconds, during which the airflow it creates gradually falls away. The throttling effect of the opening 34 relative to the striker member 31 is such that the striker member 31 remains suspended substantially in the position as illustrated until the airflow falls to such a low rate that the ball is allowed to drop through the opening 34. Having passed though the opening 34, because the guide tube 35 is wider than the opening, the striker member 31 encounters reduced resistance and is therefore allowed to fall substantially freely, with a minimum of air resistance, until it contacts the bottom closure plate 22 so as to apply a sharp impact thereto. By contrast, if the opening in the end plate 33 of the tubular body 32 were of the same diametel as the"uide tube 35, the striker member 31 would descend relatively slowly down the length of the guide tube 35 as the airflow decreased, and accordingly it would strike the bottom closure plate 22 with a much reduced impact.

In practice, it has been found that a spherical striker member weighing 120 grams and falling through a drop of 20 centimetres is sufficient to dislodge dust from the surface of filter material coated with PTFE, whilst absorbing only about 0. 5 air-watt of power whilst being held within the tubular body 32.

Whilst it is particularly convenient for the striker member 3 I to be in the form of a hollow sphere, other forms could be used. Moreover, whilst it is particularly convenient for the striker member to be held up by vit-tue of the airflow alone, it would alternatively be possible to provide some form of mechanical support, such as a light leaf spring, which would serve positively to hold the striker member in the raised position and to provide a manually, or automatically, operable release mechanism to drop the striker member when required.-One example of a manually operable release mechanism is utilise in the second embodiment as now described.

Referring to Figures 2 to 4, a second embodiment of a dirt and dust separating assembly 50 is illustrated. The assembly 50 comprises an outer housing 51 with a tangential air inlet 52 and an axial air outlet 53 in a top wall 54. An upper pan 55 of the outer housing 51 acts as a cyclonic separator and a widened, lower part 56 of the outer housing 51 acts as a dirt and dust collection container, which for emptying may be removable from the upper part 55 of the outer housing 51, or have a bottom closure flap which can be opened or removed.

An inner filter housing 60 is located below and around the outlet 53.

The filter housing includes an upper cylindl-ical palt 61, which comprises a solid wall, and a lower cylindrical part 62, which comprises a mesh wall through which air can flow from the outer housing 51. The bottom of the filter housing is closed by a bottom plate G3. but below the mesh wall part 62 there are openings 64, and around the bottom plate there is a frusto-conical baffle 65.

Located within the filter housing 60 is a filter member 66 which comprises a generally cylindrical filter body 67 formed of colTugated filter material having non-stick properties, such as may be provided by a coating of PTFE or other similar material. At its upper end, the filter body 67 is attached to an annular top plate 68, which defines a central opening 69 in register with the outlet 53.

Dirt'air is drawn into the outer housing 51 through the inlet 52, and in the appel palot 55 the larger particles of dirt and other debris, such as hairs and fibres, are separated due to cyclonic separation, and fall down into the lower part 56 which acts as a dirt collection chamber similar to that of the Figure 1 embodiment previously described. The air then passes through the mesh wall part 62 of the filter housing 60 and through the filter body 67 in which the fine dust in the air becomes entrapped. The clean air then passes out of the housing 50 via the outlet 53.

In time the filter body 67 may become clogged with the dust entrapped within it, and require cleaning, but in any event it is desirable to ensure that it is cleaned whenever the container 56 is to be emptied. For this purpose a striker assembly 70 is mounted on the top wall 54 of the outer housing 51, as shown in greater detail in Figures 3 and 4.

The top plate 68 of the filter body 67 is formed or provided with an upwardly extending protrusion 71 which, as will become clear below, acts as an impact member for the transmission of a striking force to the filter body 67.

The top wall 54 of the outer housing 51 has a rectangular recess 57 with a central opening 58 through which the upwardly extending protrusion 71 protrudes. The recess 57 has stepped end walls which define shoulders 59 which provide location means for a resilient member in the form of a leaf spring 72. As can be seen from Figure 4, the ends of the leaf spring 72 are located in the comers at the junction between the shoulders 59 and the end walls of the recess 57, and the length of the leaf spring is such that it is held in a stressed condition in which it is bent convexly upwards as shown in Figure 4 so as to be spaced away form the protrusion 7).

The striker assembly 70 further includes an actuation member 73 which is manually operable by a user of the apparatus as and when required, preferably at least prior to emptying of the container 56. The actuation member 73 comprises a lever 74 mounted at one end on a pivot pin 75 which extends between a pair of raised lugs 76 adjacent to the longitudinal edges of the recess 57. At its other end, the lever 74 is formed with an upwardly directed finger- piece 77 and a downwardly extending nose 7S.

When the actuation member 73 is operated by downward pressure applied to the finger-piece 77 there is initial resistance to movement due to the contact of the nose 78 with the leaf spring 72, but when sufficient pressure is applied to overcome that resistance to leaf spring snaps through an over-centre condition and the central region moves sharply down, as shown in Figure 5, into a downwardly convex configuration in which it impacts on the protrusion 71 carried by the top plate 68 of the filter element 66. This results in the filter body 67 being shaken briefly to dislodge the dust entrapped. The dislodged dust is then allowed to fall within the filter housing 60 and out through the openings 64 so as to be delivered over the baffle 65 into the container 56. The dust shaken from the filter body 61 falls to the bottom of the filter support 53 and then through the opening 54 and down into the dirt collection chamber 57.

There it falls into the dirt and debris previously collected and at least to some extent mixes into it. In any event when the vacuum cleaner of which the assembly forms a part is used again before the container is emptied further larger dirt will be collected on top of the fine dust. This means that, as before for the previously described embodiment, the fine dust is less likely to puff up in a cloud when the collection container 56 is emptied.

The leaf spring 72 is not stable with the central region in the downwardly convex configuration as shown in Figure 4, and thus it returns to its original upwardly convex configuration, as shown in Figure 3, when the finger-piece 77 is released, thereby returning the actuation member 73 to its original position, as shown in Figure 4. While only the central region of the leaf spring 72 is deflected downwardly into an unstable configuration, it would be possible for the whole leaf spring to adopt a downwardly convex configuration after passing through an over-centre condition but without reaching a stable condition by arranging for contact with the protrusion 71 to occur before a stable configuration is reached. Altematively or additionally, the actuation member may have a separate return spring.

It will be appreciated that other forms of striker mechanism may be employed, such as a plunger that is spring biased away from the protrusion 71 and held in spaced relation thereto by detent means or the like to provide additional resistance to downward movement of the striker which yields suddenly, or a plunger that is biased into contact with the protrusion 71 and arranged to be lifted away from the protrusion by an actuation member and released, either automatically of voluntarily, so as to strike the protrusion.

While, as described above, the actuation member 73 is provided at the top of the dirt and dust separating assembly 50 (which is removable from the vacuum cleaner apparatus for emptying) and is preferably arranged so as to be accessible for operation at any time by the user, and especially when the assembly is removed for emptying, the arrangement may be such that the actuation member can be operated altematively or additionally by means of a button provided for that purpose on the exterior of the apparatus. Alternatively it may conveniently be incorporated into a mechanism by which the assembly 50 is released from a body construction of the vacuum cleaner apparatus when it is desired to empty the collection container 56. This means that the filter 67 is always cleaned before the container 56 is emptied, and does not require the user to remember to do so.

In the present specification"comprise"means"includes or consists of' and "comprising" means "including or consisting of".

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result. as appropriate, may, separately, or in any combination of such features. be utilise for realising the invention in diverse fonts thereof.