Dirt Separator

The present invention relates to a dirt separator for a vacuum cleaner and to a vacuum cleaner comprising the dirt separator.

Vacuum cleaners rely on a suction generator to generate an airflow, which is used to pick up dirt from a surface to be cleaned. The airflow is passed through one or more separation stages to separate dirt from the airflow before the airflow is ejected from the vacuum cleaner. Pressure losses can occur as the airflow passes through the separation stages, which can reduce performance of the vacuum cleaner and/or increase power consumption of the suction generator.

According to a first aspect of the present invention, there is provided a dirt separator for a vacuum cleaner, comprising a dirt separation chamber extending along a longitudinal axis from an opening to an outlet, and a filter assembly extending parallel to the longitudinal axis and dividing the dirt separation chamber into a dirt collection chamber upstream of the filter assembly, and an outlet chamber downstream of the filter assembly. The outlet chamber has a cross-sectional area that is substantially constant along a length of the filter assembly.

The dirt collection chamber may have a cross-sectional area that is substantially constant along the length of the filter assembly. The cross-sectional areas of the outlet chamber and dirt collection chamber are in the plane normal to the longitudinal axis.

During use of the dirt separator, suction is generated at the outlet of the dirt separation chamber, causing airflow to flow along an airflow pathway from the opening to the outlet. Since the cross-sectional area of the outlet chamber is substantially constant along its length, the suction is unbalanced along the length of the filter assembly. In particular, suction is greatest at the end of the filter assembly adjacent the outlet and is weakest at the end of the filter assembly adjacent the opening. This then has the advantage that dirt is encouraged to fill the dirt collection chamber in a direction from the outlet (where suction is greatest) to the opening (where suction is weakest). As a result, the dirt separator is able to store a greater quantity of dirt within the dirt collection chamber before emptying is required. This arrangement is by no means intuitive. One would normally ensure that the suction along the filter assembly is balanced to ensure that the filter assembly is loaded evenly with dirt. This would be achieved by ensuring that the cross-sectional area of the outlet chamber gradually decreases in a direction from the outlet to the opening. The cross-sectional area of the outlet chamber would therefore be greatest at the end adjacent the outlet, and smallest at the end adjacent the opening. Having balanced suction along the length of the filter assembly would ensure that dirt collects more evenly on the filter assembly. However, the net result of this is that the dirt collection chamber fills with dirt in a less efficient way. For example, dirt may accumulate more quickly at the end of the dirt collection chamber adjacent the opening, thereby preventing further dirt from being drawn into the dirt separator. Dirt would therefore clog the opening end of the dirt collection chamber even though the remainder of the dirt collection chamber may be relatively empty.

Owing to the location of the opening and the outlet, the airflow moves longitudinally over the surface of the filter assembly. The unbalanced suction encourages more of the airflow to pass through the filter assembly at that end adjacent the outlet. As a result, the airflow may act to scrub the surface of the filter assembly, i.e., dirt which has accumulated at the opening end of the filter assembly may be agitated and driven towards the outlet end by the moving airflow. This then helps keep more of the filter assembly clear of dirt, which improves the performance of the vacuum cleaner and allows the vacuum cleaner to be used for a longer period of time before emptying of the dirt collection chamber is required.

The dirt collection chamber and outlet chamber may be free from features, restrictions or obstructions that increase or decrease a cross-sectional area of the airflow pathway along the length of the filter assembly. This may then better encourage the behaviour described above, i.e., dirt collects within the dirt collection chamber from the end adjacent the outlet to the end adjacent the opening.

A ratio of the cross-sectional areas of the dirt collection chamber to the outlet chamber may be between 0.9 and 1.1 along the length of the filter assembly. As a result, a relatively compact arrangement may be achieved for the dirt separator without adversely impacting performance.

A ratio of the cross-sectional areas of the opening to the outlet may be between 0.9 and 1.1. As a result, a relatively compact arrangement may be achieved without adversely impacting performance. In other vacuum cleaners, the outlet is typically much larger than the opening. However, by ensuring that the ratio of the opening to the outlet is between 0.9 and 1.1, a relatively small outlet may be employed that does not adversely restrict the airflow moving through the dirt separator.

The sum of the cross-sectional areas of the dirt collection chamber and the outlet chamber may be at a minimum along the length of the filter assembly. This increases a velocity of airflow passing through the filter assembly from the dirt collection chamber to the outlet chamber, which may improve filtration performance of the filter assembly. This may also increase the velocity of the airflow moving parallel to the filter assembly to better scrub the filter assembly and encourage dirt to move towards the outlet end of the dirt collection chamber.

A ratio of a length of the dirt separation chamber to a width of the dirt separation chamber may be at least 5. This allows for the filter assembly to be substantially longer than it is wide, which helps to increase an area of a filtration surface of the filter assembly without increasing an overall diameter of the dirt separator. Having a larger filtration surface area can lead to a smaller pressure drop and thus improved suction at the opening, and can also increase a time between necessary replacement or cleaning of the filter assembly.

The dirt separation chamber may have a length no less than 150 mm. As a result, a relatively good dirt capacity may be achieved in a dirt separation chamber having a relatively small width or diameter. Additionally, a relatively long filter assembly having a good surface area may be employed, which in turn can improve performance and increase the time between replacement or cleaning.

The dirt separation chamber may have a width, or diameter, no greater than 60 mm. That is, a maximum dimension of the dirt separation chamber in a plane normal to the longitudinal axis may be no greater than 60 mm. More specifically, the dirt separation chamber may have a width in the region of 35-40 mm. This can help to decrease an overall diameter of the vacuum cleaner in which the dirt separator is employed. This could be particularly advantageous in a handheld vacuum cleaner in which size and weight are significant considerations. This may be particularly ergonomic, allowing an outer perimeter of the dirt separator to form a handle for a user to hold the vacuum cleaner during use.

The dirt separation chamber may be substantially cylindrical. This may help to provide smooth, curved walls of the dirt collection chamber and outlet chamber that are substantially free of sudden changes in direction. This may contribute to smoother airflow through the dirt separation chamber.

The filter assembly may comprise a mesh screen and a removable filter medium located downstream of the mesh screen. The mesh screen separates larger dirt and debris entrained in the airflow entering the dirt collection chamber via the opening, and the filter medium filters smaller particles of dirt and dust from the airflow.

The filter medium may be comprised in a removable cartridge having a frame supporting at least one filter medium. This may facilitate removal, cleaning and/or replacement of the filter medium when the filter medium becomes clogged with the dirt and dust so that performance of the dirt separator is reduced.

The removable cartridge may comprise more than one type of filter media. For example, a fleece upstream of an electrostatic medium. This may help to increase the filtration performance of the filter assembly.

The mesh screen may be formed from a metal or metal alloy. This may provide a robust surface to protect the filter medium from the larger dirt and debris and that is easy to clean. The mesh screen may have a substantially smooth surface facing the dirt collection chamber, which may help to prevent dirt from catching on the surface.

The filter assembly may be substantially v-shaped or u-shaped in cross-section. The cross-section is in a plane normal to the longitudinal axis. A lowermost portion of the v or u may extend into the outlet chamber. Both shapes provide a greater surface area of the filter assembly for the same length compared to a substantially planar filter assembly. This may improve performance and/or increase the time between replacement or cleaning of the filter assembly. A v-shaped cross-section provides a slightly greater cross-sectional area than a u-shaped cross-section. A u-shaped cross-section provides a smoother shape than a v-shaped cross-section, which may help to prevent dirt from getting caught in the acute angle of the v.

The dirt separator may comprise a valve positioned at the opening, and the valve may be movable between a closed position, in which airflow is prevented from entering the dirt collection chamber via the opening, and a first open position, in which airflow is permitted to enter the dirt collection chamber via the opening. The valve may be moveable to the first open position in response to suction within the dirt separation chamber, and may be moveable to the closed position in response to removal of the suction within the dirt separation chamber. Accordingly, the valve prevents dirt collected in the dirt collection chamber from escaping via the opening when the suction is removed.

The valve may be movable, in response to a user input, from the closed position to a second open position to evacuate dirt collected in the dirt collection chamber. Accordingly, the dirt collection chamber can be emptied via the opening, which negates a need for an additional opening in the dirt separator. This provides a space-efficient construction in which the dirt is evacuated along the air pathway through which it entered the dirt collection chamber. The substantially constant cross-section of the dirt collection chamber can help to ensure that no obstructions impede the evacuation of the dirt from the dirt collection chamber. The first and second open positions may be the same position.

The valve may be biased to the closed position, for example by a biasing assembly or due to a property of a material from which the valve is formed. This may ensure that the valve returns to the closed position when the suction within the dirt separation chamber is removed so that the dirt cannot escape the dirt separation chamber inadvertently via the opening.

The valve may be formed from an elastically deformable material biased to the closed position. This may negate a need for an additional biasing assembly, which may reduce cost and/or simplify the assembly.

The dirt collection chamber may be located on one side of the dirt separator, and the outlet chamber may be located on an opposite side of the dirt separator. The dirt separation chamber may be defined by an outer wall. For example, the outer wall may be substantially cylindrical. The dirt collection chamber may extend between an upstream surface of the filter assembly and a first side of the outer wall, and the outlet chamber may extend between a downstream side of the filter assembly and a second, opposite side of the outer wall. This may provide a space-efficient arrangement, enabling a relatively small outer equivalent diameter of the dirt separator.

According to a second aspect of the present invention, there is provided a vacuum cleaner comprising a main body comprising a dirt separator according to the first aspect and a suction generator for generating an airflow. The suction generator is positioned downstream of the dirt separator and has a rotational axis co-axial with the longitudinal axis of the dirt separator. This provides a space-efficient and ergonomic arrangement, and may enable the vacuum cleaner to have a substantially constant outer cross-sectional profile.

The main body may have a substantially constant cross-section along the longitudinal axis, for example the main body may be substantially cylindrical. This provides a space-efficient and ergonomic arrangement. The main body may have an outer diameter no greater than 60 mm, for example in the region of 35-40 mm. This may be an ergonomic size to allow the main body to form a handle for a user to grip during use of the vacuum cleaner.

The main body may comprise a battery assembly, which may enable to vacuum cleaner to be used as a cord-free device. The battery assembly may be co-axial with the dirt separator and the suction generator.

The example vacuum cleanerofcomprises a main body, an attachmentand a cleaner head. The cleaner head has an inlet aperturearranged to face a surface to be cleaned by the vacuum cleaner, and an outletfluidly connected to the inlet aperture. The attachmentin this example is a tool, but in other examples may be a wand or other suitable attachment type. In any event, the attachmentcomprises a ductbetween a first endand a second, opposite endof the attachment. When assembled, as shown in, the cleaner headis removably attached to a first endof the attachment, and a second endof the attachmentis removably attached to the main bodysuch that an airflow pathway is formed from the cleaner head, through the attachment, to the main body.

When attached to the main body, the attachmentis arranged co-axially with a central longitudinal axisof the main body. In this example, the main bodyand the attachmentare generally cylindrical in shape, with each having an outer housing,of a substantially constant outer diameter. The outer housingof the main bodysurrounds a suction generatorto generate an airflow along the airflow pathway, and a battery assemblyto power the suction generator. It will be appreciated that in other examples, the main bodymay be provided with a power supply unit, to replace or supplement the battery assembly, for connection to a mains power outlet.

The main bodycomprises a dirt separatorupstream of the suction generator. The dirt separatoris shown in more detail and in various configurations in. As with the outer housing, the dirt separatoris also cylindrical in shape and has a substantially constant outer diameter.

The dirt separatorcomprises an openingat an interface between the main bodyand the attachment. The openingserves as both an air inlet and a dirt outlet of the dirt separator. When serving as an air inlet, the openingpermits the airflow generated by the suction generatorto pass into the dirt separatorfrom the ductin a direction parallel to the longitudinal axisof the main body(which is co-axial with a longitudinal axis of the dirt separator). The dirt separatoralso comprises an air outletfluidly connected to the suction generator, to permit airflow to exit the dirt separator. In this example, when assembled, a ratio of the cross-sectional areas of the openingand the outletis substantially 1.

In this example, the dirt separatorcomprises a framethat extends parallel to the longitudinal axisof the main body. The frameis fixed at a first end to the outer housingof the main body. A second opposite endof the framepartially defines the openingof the dirt separator.

The framesupports electrical terminalsand electrical wires. The electrical terminalsare located at the second endof the frame, and the electrical wiresextend along the length of the framefrom the main bodyto the electrical terminals. The electrical terminalsmate with corresponding terminals (not shown) of the attachmentto transfer electrical power from the main bodyto the cleaner head.

A filter assemblyis attached to the frame. The filter assemblyis configured to separate dirt D from dirt-laden airflow received via the opening, and comprises two filtration layers,for doing so, as best shown in. It will be appreciated that in other examples, the filter assemblymay comprise a different number of filtration layers.

The filter assemblycomprises a mesh or screenfixedly attached to the frameand a filter cartridge removable attached to the frame. In this example, the mesh or screenis the uppermost filtration layershown in, and is formed of a metal.

The filter cartridge is located downstream of the meshand comprises a filter frame and filter mediaheld by the frame. The meshprotects the filter mediafrom impacts by debris in the dirt separator. The filter mediais the lowermost layershown in. Being removable allows the filtration mediato be replaced and/or washed to restore filtration performance of the filter assembly. Although not shown in, in some examples the filter mediahas a plurality of filtration layers of differing filtration properties. For example, the filter mediamay comprise a layer formed from fleece upon a layer formed from an electrostatic medium.

The meshis substantially curved, as viewed in a plane normal to the longitudinal axis(), and the filter mediais substantially planar. It will be appreciated that in other examples, the meshmay be, for example, v-shaped or planar.

shows an example of an alternative filter assemblyin the dirt separator. The alternative filter assemblyis very similar to the filter assemblyexcept that in this example the filter mediais substantially curved. Providing a substantially planar filter media, as shown in, allows a thicker lower-most filtration layerto be employed within the same overall diameter of the dirt separatorcompared to a curved filter media, as shown in, which can increase the filtration performance of the filter assembly. Conversely, providing a curved filter mediaincreases the surface area of the filter mediacompared to the surface area of the filter media, which may also provide filtration benefits such as increasing a time between required replacement or cleaning of the filter media. References herein to the filter assemblymay equally apply to the alternative filter assembly

The filter assemblyis elongate in a direction parallel to the longitudinal axis. Accordingly, airflow enters the dirt separatorin a direction parallel to the filter assemblyso that the airflow scrubs the meshof the filter assemblyto help attenuate accumulation of dirt D on the filter assembly.

The filter assemblyforms a wall of a dirt collection chamber. The dirt collection chamberreceives dirt-laden airflow via the openingduring vacuum cleaning and fills up with dirt D separated from the dirt-laden airflow by the filter assembly. The dirt collection chamberis elongate in shape and extends between the openingat one end, and the outer housingof the main bodyat an opposite end. The dirt collection chamberextends alongside the filter assemblyand has a substantially constant cross-sectional profile along the length of the filter assembly, as viewed in a plane normal to the longitudinal axis. The elongate shape of the dirt collection chamberallows for a larger volume for a given diameter of the dirt separator.

The filter assemblyseparates the dirt collection chamberfrom an outlet chamberdownstream of the filter assembly. The outlet chamber fluidly connects the filter assemblyto the air outlet. The dirt separator therefore comprises an upper longitudinal portion comprising the dirt collection chamberand a lower longitudinal portion comprising the outlet chamber.

The outlet chamberalso has a constant cross-sectional area along the length of the filter assembly. In this example, the ratio of the cross-sectional areas of the dirt collection chamberto the outlet chamberis substantially 1. Since the cross-sectional area of the outlet chamberis substantially constant along its length, suction is unbalanced along the length of the filter assembly. In particular, suction is greatest at the end of the filter assemblyadjacent the outletand is weakest at the end of the filter assemblyadjacent the opening. Dirt D is therefore encouraged to fill the dirt collection chamberin a direction from the outlet(where suction is greatest) to the opening(where suction is weakest). As a result, the dirt collection chamberis able to store a greater quantity of dirt D within the dirt collection chamberbefore emptying is required.

The dirt separatorcomprises a tubular outer wall, or bin,extending along a length of the dirt separatorand surrounding the frame, the filter assemblyand the valve. The outer walldefines a cylindrical dirt separation chamberof the dirt separator, the chambercomprising the dirt collection chamberand the outlet chamber. In this example, the dirt separation chamberis around 8 times longer than it is wide. The dirt collection chamberis therefore defined along one side by the outer walland along an opposite side by the frameand the filter assembly.

A valveis connected to the second endof the framesuch that the valveis positioned at the opening. The valveis movable between a closed position (as shown in), a first open position (as shown in) in response to suction within the dirt separatorgenerated by the suction generator, and a second open position (as shown in). The valveis movable between the different positions about a pivot axisthat is normal to the longitudinal axis. In the present example, the valve is formed of an elastically deformable material, such as rubber, and is configured to pivot about a hinge at the base of the valve.

In the closed position, the valveobstructs the openingsuch that dirt D is prevented from escaping the dirt collection chambervia the opening. The valveabuts a lipof the outer wallwhen in the closed position, as best shown in. The lipacts to help maintain the valvein the closed position, particularly when dirt D in the dirt collection chamberrests against the valve, as shown in. In the closed position, an outer perimeter of the valveforms a seal with the frameand the outer wallat the opening. This seal prevents dirt D from inadvertently escaping the dirt collection chamber.

The valvemoves from the closed position to the first open position in response to suction within the dirt collection chamber. In the first open position, the openingis unobstructed by the valve, thereby enabling dirt-laden airflow to be drawn from the inlet apertureof the attachment, through the ductand into the dirt separatorvia the opening. In moving to the first open position, the valvepivots about the pivot axisin a first direction towards the interior of the dirt collection chamber. The valvethen provides a smooth surface for the airflow, which can help to prevent dirt within the airflow from catching on the valveas it passes into the dirt collection chamber.

As described below in more detail, the valvemoves from the closed position to the second open position during emptying of the dirt separator. In the second open position, the openingis unobstructed by the valve, thereby enabling dirt D in the dirt collection chamberto exit the dirt separator, for example under gravity, via the opening. In moving to the second position, the valvepivots about the pivot axisin a second opposite direction to that of the first open position. The valvethen provides a smooth surface to help prevent the dirt D from catching on the valveas it passes out of the dirt collection chamber

The valveis biased to the closed position such that, in the absence of force acting on the valve, the valveremains or returns to the closed position.

The dirt separatorcomprises a welllocated downstream of the opening, between the valveand the dirt collection chamber. The wellhas a greater cross-sectional area than the dirt collection chamber. When the dirt separatoris not in use, dirt D collected in the dirt collection chambermay fall under gravity and come to rest against the valve, as shown in. In examples of a dirt separator that do not have a well, the accumulation of dirt D on one side of the valvemay hinder movement of the valveto the first open position. Accordingly, a relatively large force may be required to move the valveagainst the weight of the dirt D to the first open position. If there is too much dirt D in the dirt collection chamber, the dirt D may cause the valveto become stuck in the closed position, or at least prevent the valvefrom moving fully to the first open position under the suction generated by the suction generator. The wellprovides a larger space behind the valveto accommodate dirt D that falls under gravity. This can reduce the force required to move the valveto the first open position, and therefore help to prevent the valvefrom getting stuck in the closed position.

Build-up of dirt D in the dirt collection chambercan negatively impact the pick-up performance of the vacuum cleaner. Performance can be at least partially restored by emptying the dirt D from the dirt collection chamber. Accordingly, the dirt separatoris arranged to allow a user to perform a simple dirt emptying sequence to empty dirt D from the dirt collection chamber, as will now be described.