Vacuum cleaner with air bleed

A vacuum cleaner comprises a cyclonic separator (116) for separating dirt and dust from an incoming airflow. A tool (300) and a suction conduit (114) connect the tool (300) to the separator (116). The tool (300) comprises a main air inlet aperture for engaging with a surface to be cleaned and a bleed air inlet (310) for allowing air to bleed into the suction path. The bleed air inlet (310) is located such that it is separate from the main inlet. The cross-sectional area of the bleed air inlet (310) is sufficiently large that, in use, the bleed air inlet (310) admits a sufficient quantity of air to maintain adequate separation efficiency in the separator of the cleaner even when the main air inlet is fully blocked.

FIELD OF THE INVENTION

This invention relates to a vacuum cleaner.

BACKGROUND OF THE INVENTION

Vacuum cleaners are usually supplied with a range of tools for use with various cleaning situations that a user may encounter. An upright vacuum cleaner has a wide, floor-engaging cleaner head at the base of the cleaner which is used for general floor cleaning. A range of smaller tools may also be supplied with the machine. These are usually attached to the end of a flexible hose of the cleaner. The tools often include a crevice tool for use in narrow, confined spaces, a stair tool and an upholstery tool with a brush head. A cylinder or canister vacuum cleaner has a wide floor tool which is attached to the end of a cleaning wand for general floor cleaning and a similar range of smaller tools for use in other cleaning situations.

For any vacuum cleaner, it is important to maintain a good flow rate of air into the floor tool and along the suction path of the cleaner to maintain good cleaning performance. This is particularly important with a cleaner that relies on cyclonic or centrifugal separation as the flow rate of dust-laden air within the cyclonic separating chamber is an important factor in determining the efficiency of the dust separation. It is known for tools to include one or more bleed air inlets. As shown inFIG. 1, the air inlet of a crevice tool10has a flat portion12, a notched portion14and an opening15. The notched portion14ensures that some air flows into the tool10even when the flat portion12is sealed against a surface.

FIG. 2schematically shows a known type of cyclonic vacuum cleaner. The vacuum cleaner100incorporates a floor tool10which is attached directly to a hose114. The hose114is directly connected to dust-separating apparatus116. The dust-separating apparatus116is a cyclonic separating apparatus using one or more cyclonic separation stages. Downstream of the dust-separating apparatus116is a pre-motor filter120, followed by a fan122which is driven by a motor124. A further filter126is located after the motor124. A bleed valve118is located on the dust-separating apparatus. The bleed valve118is arranged to admit air into the separating apparatus when the flow of air along the airflow path is significantly reduced. The bleed valve can respond to the pressure along the airflow path reducing to a predetermined absolute value, or to the difference in pressure between two parts of the airflow path reaching a predetermined value.

In use, the motor124operates to activate the fan122which causes a flow of air to pass from the floor tool10to the dust-separating apparatus116via the hose114. After separation has taken place, the airflow passes through the pre-motor filter120, past the fan122, past the motor124providing a cooling effect, and through the post-motor filter126before being expelled to the atmosphere. A bleed valve118is arranged such that, if the pressure within the dust-separating apparatus116, and particularly at the location within the dust-separating apparatus116at which the bleed valve118is placed, drops below a pre-determined value, the bleed valve118opens so as to allow air from the atmosphere to enter the cyclonic dust-separating apparatus in order to maintain an adequate airflow to effect separation. The prevention of the airflow from falling below a predetermined level helps to ensure that the motor124is adequately cooled so as to prevent any risk of overheating in the event of a blockage occurring in the airflow path upstream of the bleed valve118.

However, the provision of a bleed valve, particularly a pressure differential bleed valve, adds considerable cost to the cleaner. Also, since the bleed valve has movable parts it is prone to wear and degradation over a period of use.

SUMMARY OF THE INVENTION

The present invention seeks to obviate the need for a bleed valve along the airflow path to the separator.

Accordingly, the present invention provides a vacuum cleaner comprising a cyclonic separator for separating dirt and dust from an incoming airflow, a tool and a suction conduit for connecting the tool to the separator, wherein the tool comprises a housing or body defining a suction path, the body having a main air inlet aperture for engaging with a surface to be cleaned and for allowing dirty air to enter the suction path, and a bleed air inlet for allowing air to bleed into the suction path, the bleed air inlet being located such that it is separate from the main air inlet aperture and wherein the bleed air inlet is permanently open and the bleed air inlet has a cross-sectional area such that, in use, it admits a sufficient quantity of air to maintain adequate separation efficiency in the separator of the cleaner when the main air inlet aperture is fully blocked.

The bleed air inlet admits a sufficient quantity of air to maintain adequate separation efficiency in the vacuum cleaner, even when the main air inlet aperture to the tool is fully blocked. This is particularly important in a vacuum cleaner which uses a set of small, parallel cyclonic separators where there is a risk that the separators could become blocked if the flow rate reduces below a critical value since the vortex cannot form. Also, the provision of a continuous flow of bled air through the tool into the suction path reduces or avoids sudden changes in airflow through the separation apparatus, which minimises the risk of dirt becoming re-entrained in the airflow through the separator. This extends the life of filters placed after the separation apparatus. The provision of the bleed air inlet can also avoid the need for a bleed air valve located further downstream along the suction path, which reduces the overall cost of the cleaner. The continuous provision of bled air also reduces the force that is required by a user to push the tool along a surface.

Preferably the bleed air inlet of the tool is located such that it is spaced from the main air inlet aperture and directs air into the suction channel towards the main aperture. In an embodiment, the tool includes an upper face, such as a portion of the tool body that faces generally away from the surface to be cleaned when the main inlet aperture is engaged on the surface. The bleed air inlet can be located on the upper face of the tool. This position of the bleed air inlet ensures that the bled air helps to agitate the surface that is being cleaned and thus results in more dirt, fluff and other debris being removed from the surface. Thus, it can be seen that the provision of the bleed air inlet improves the cleaning performance of the tool at all times, whether the main air inlet aperture is blocked or not.

Preferably the bleed air inlet is a plurality of apertures. These can be spaced across the tool. Each of the apertures of the bleed air inlet includes an inlet. In an embodiment, the tool is configured such that when the main air inlet aperture is engaged on the surface to be cleaned, the inlets to the apertures are disposed at relatively different heights with respect to the surface.

Preferably the bleed air inlet or inlets has a guide channel for guiding the flow of air.

In an embodiment, the main air inlet aperture generally occupies a plane, and it has been found that providing the bleed air inlet in a direction which is substantially perpendicular to the plane of the main air inlet aperture provides a particularly effective cleaning effect. The tool body has an outlet to allow flow to exit the tool from the suction path. It has also been found that the angle of the bleed air inlet with respect to the longitudinal axis of the air outlet of the tool body has an effect on the cleaning performance of the tool. By aligning the bleed air inlet such that it points away from the longitudinal axis of the outlet, a greater proportion of the bled air is likely to strike or to pass through the floor surface beneath the main air inlet. It has been found particularly beneficial to cause the bled air to flow through an obtuse angle, and preferably an angle approaching 180°.

In an embodiment, the tool also includes an agitator mounted within the body for agitating the surface to be cleaned. For example, the agitator may be a comb or brush. The bleed air inlet is preferably located such that it directs bled air towards a distal end of the agitator, where the agitator meets the surface.

In an embodiment, the body includes an outlet to allow flow to exit the tool from the suction path, and the bleed air inlet is directed at an angle with respect to the air outlet that is greater than 90°. Preferably, the cross-sectional area of the bleed air inlet is sufficient to allow, in use, a flow rate of at least 20 liters per second through the tool. For use in a vacuum wherein the cyclonic separator comprises a set of parallel cyclonic separators, the cross-sectional area of the bleed air inlet is sufficient to allow, in use, a flow rate above that at which the separators would become blocked.

The tool may be a configured as any one of a variety of types of vacuum tools. For example, the tool may be crevice tool or a stair tool.

DETAILED DESCRIPTION OF THE DRAWINGS

FIGS. 3 to 5show a stair tool300which is used for cleaning stairs and areas which cannot readily be reached by a full-sized tool.FIG. 5shows a cross-section along A-A ofFIG. 4. The tool has a body with a neck301for connecting a suction hose or wand of a vacuum cleaner. The body defines a suction path or suction passageway350. The lower face of the tool as shown inFIG. 4has a main air inlet aperture305, depicted inFIG. 5as main suction opening330, which allows air to enter the suction passageway350. The main inlet aperture305or main suction opening330is intended to be pressed against a surface which is to be cleaned. In the embodiment ofFIG. 5, the tool300includes an agitator, such as comb320, which is positioned within the suction passageway350and extends downwardly towards the main suction opening330. The comb has a formation of alternate fingers and openings when viewed in the direction X ofFIG. 4, the fingers extending towards the inlet aperture305or suction opening330. The cross-section ofFIG. 5shows the lowermost, distal end of one of the fingers of the comb. The comb serves to agitate the floor surface when it is pushed forwards and backwards across the surface. A set of bleed air inlets310is located across the width of the tool300. The tool has an upper face that faces generally away from the surface to be cleaned when the main suction opening330is engaged thereon. Each of these inlets extends from the upper face towards the main suction opening330. The inlets310in this tool are perpendicular to the plane of the main suction opening330. A pathway exists between the lowermost part of the bleed air inlets and the main passageway350, through the comb320. This pathway exists even when the tool is pressed fully against a surface. Eight inlets are shown, spaced across the full width of the tool, but other numbers of inlets are possible. The inlets could be confined to only part of the width of the tool, but we have found best results are achieved when the inlets are spaced across the full width of the tool.

In use, air is drawn through the main suction opening330. This airflow passes through the pile of a carpeted surface, carrying dirt and dust with it, and then flows along passageway350towards the cleaner. A secondary flow of air enters the tool via inlets310. This secondary air or bled air is directed towards the surface which is pressed against the main suction opening330. Some of the air will be drawn through the pile of the carpeted surface before flowing along passageway350. Other air may flow directly from inlet310to passageway350, bypassing the carpeted surface. The combination of air being drawn through the surface from the sides and above helps to increase the agitation of the floor surface. Also, air will still be able to freely flow into the tool via inlets310when the surface is very thickly piled and when there is little or no flow in direction360.

FIGS. 6 to 8show a crevice tool, withFIG. 8showing a cross-section along B-B ofFIG. 6. A crevice tool is typically sued to clean confined areas. The tool has a body with a neck601for connecting to a suction hose or wand of a vacuum cleaner. The lower face of the tool has a main suction opening630which is intended to be pressed against a surface which is to be cleaned. A set of bleed air inlets610separated by vanes611is located on the lowermost part of the upper surface of the tool600, the inlets being positioned one behind the other. Each of these inlets610extends from the upper face towards the main suction opening630. The inlets610in this tool are set at an angle of around 70° to the plane of the main suction opening630although this angle could be perpendicular, as with the tool ofFIG. 3, or some other angle. The inlets610are directed away from the longitudinal axis of the main passageway650, thus ensuring that air which flows into the tool via inlets610is forced to make a ‘u-turn’ of 155° in order to flow out of the tool along the passageway650. This is shown more clearly inFIG. 10. A pathway exists between the lowermost part of the bleed air inlets and the main passageway650. This pathway exists even when the tool is pressed fully against a surface. Four inlets are shown, but other numbers of inlets are possible.

In use, this tool works in a similar manner to the tool ofFIGS. 3-5.FIG. 9shows the main directions of airflow andFIG. 10shows a more detailed plot of airflow. Air is drawn through the main suction opening630. This airflow passes through the pile of a carpeted surface, carrying dirt and dust with it, and then flows along passageway650towards the cleaner. A secondary flow of air enters the tool via inlets610. This secondary air or bled air is directed towards the surface which is pressed against the main suction opening630. Some of the air will be drawn through the pile of the carpeted surface before flowing along passageway650. Other air may flow directly from inlet610to passageway650, bypassing the carpeted surface. The combination of air being drawn through the surface from the sides and above helps to increase the agitation of the floor surface. Also, air will still be able to freely flow into the tool via inlets610when the surface is very thickly piled and when there is little or no flow in direction660. The plot ofFIG. 10clearly shows that air is directed towards and, in part, through the surface to be cleaned rather than simply flowing directly from the inlet610to the passageway650and bypassing the surface.

FIG. 11schematically shows a cyclonic vacuum cleaner800which uses the tools described above.

The principle of cyclonic separation in domestic vacuum cleaners is described in a number of publications including EP 0 042 723. In general, an airflow in which dirt and dust is entrained enters a first cyclonic separator via a tangential inlet which causes the airflow to follow a spiral or helical path within a collection chamber so that the dirt and dust is separated from the airflow. Relatively clean air passes out of the chamber whilst the separated dirt and dust is collected therein. In some applications, and as described in EP 0 042 723, the airflow is then passed to a second cyclone separation stage which is capable of separating finer dirt and dust than the upstream cyclone. The airflow is thereby cleaned to a greater degree so that, by the time the airflow exits the cyclonic separating apparatus, the airflow is almost completely free of dirt and dust particles.

InFIG. 11, most of the parts of the cleaner are the same as shown inFIG. 1and have the same reference numbers. However, the tool10has been replaced by one of the tools300,600which have bleed air inlets. Since air can now flow along the airflow path even when the main inlet of the tool is blocked, effective separation can be maintained in separation apparatus116without the need for the bleed valve118. A bleed valve810can be fitted downstream of the separator and pre-motor filter120to ensure that the motor will not overheat when the filter120becomes blocked. The cross-sectional area of the bleed air inlets310,610is chosen such that, even when the main air inlet is fully sealed against a surface, the flow rate of air through the tool will be sufficient to maintain adequate separation efficiency in the dust-separating apparatus of the cleaner. It has been found that dimensioning the inlets310,610to ensure a minimum flow rate of 20 liters per second through the tool provides good separation.

As an alternative to what is shown inFIG. 11, the bleed valve118ofFIG. 1could be used in its original position along with the tools300,600. The increased cleaning performance of the tools provides a beneficial effect, and the bleed valve118opens in the event that a blockage occurs somewhere between the tools300,600and the dust-separating apparatus.

FIG. 12shows a cross-section through a further embodiment of a tool. The tool has a body705with a neck701for connecting to a suction hose or wand of a vacuum cleaner. The body defines a suction path therethrough. The lower face of the tool has a main air inlet aperture or main suction opening730which is intended to be pressed against a surface which is to be cleaned, the main suction opening allowing air to enter the suction path. A set of bleed air inlets710are located on the lowermost part of the upper surface of the tool700. Each of these inlets710extend from the upper face towards the main suction opening730. This embodiment differs from those previously described in that a brush740is positioned within the housing and extends towards the plane of the suction opening730. The bleed air inlets710are configured such that bled air is generally directed toward a distal end of the agitator. For example, in the embodiment illustrated inFIG. 12, the bled air will strike the carpet at the base of the brush, where the distal end of the brush meets the surface to be cleaned, thus subjecting the surface to agitation by both the brush and the bled air. The inlets710in this tool are set at an angle of around 45-60° to the plane of the main suction opening730, although this angle could be varied. A pathway exists between the bleed air inlets and the main passageway750, through the brush740. This pathway exists even when the tool is pressed fully against a surface. Rollers720are mounted to the lower surface of the tool700to minimise the ‘push force’ which a user must exert to move the tool. Other parts of the lower surface of the tool which may come into contact with the surface can be coated with a low-friction material such as PTFE to further reduce resistance.