WO2021136682A1

WO2021136682A1 - A pump for use in a vacuum cleaner

Info

Publication number: WO2021136682A1
Application number: PCT/EP2020/086926
Authority: WO
Inventors: Wessel Adolf OTTEN; Johannes Tseard Van Der Kooi
Original assignee: Koninklijke Philips N.V.
Priority date: 2019-12-30
Filing date: 2020-12-18
Publication date: 2021-07-08
Also published as: CN115297753A; EP4084664A1; EP4084664B1; EP3845106A1; US20230041102A1; JP2023508583A

Abstract

A pump is for generating a suction for application to a vacuum cleaner dirty air inlet. There is a motor inside a motor outer casing and a fan outside the motor outer casing having a main inlet and a main outlet. The fan generates a main suction flow between the main inlet and the main outlet and creates a region of under pressure. This under pressure is used to drive a secondary flow between a cooling air inlet to the motor outer casing and a cooling air outlet from the motor outer casing. The secondary air flow is induced by making use of an under pressure generated by the fan.

Description

A PUMP FOR USE IN A VACUUM CLEANER

FIELD OF THE INVENTION

This invention relates to a vacuum cleaner pump, and in particular relates to a pump suitable for use as part of a wet (or wet and dry) vacuum cleaner.

BACKGROUND OF THE INVENTION

For wet vacuum cleaners (or wet cleaning devices more generally) there is always a risk that an air flow still containing an amount of water or other dirt will reach the main fan motor, even though the air flow has already passed through a filter for separating the dirt and moisture content, such as a labyrinth filter or a cyclone.

In conventional dry vacuum cleaners, this main flow is used to cool the motor part, but this is not possible if the main air flow contains water or other dirt. Water and other dirt in the motor part gives rise to a high risk of failure of the motor part.

A common solution for this problem is to use a so-called bypass motor. In a bypass motor there are two separate air flows. The main air flow transports the dust, water and other dirt to the dirt management system, but it is guided and sealed in such a way that it is impossible for this main air flow to reach the motor part.

A secondary air flow is created to cool the motor part. Normally this secondary air flow is induced by adding a cooling fan to the motor part. A special set of channels is added in the appliance to guide this air flow from the outside of the appliance to, and through, the motor part and back again back to the outside of the appliance.

Figure 1 shows a typical configuration of a pump with a bypass motor and fan. The pump 10 comprises a motor 12 with a spindle a fan 14, a diffuser 15 and a fan casing 40. A main air flow enters the fan as an entrance flow 16 and exits as an exit flow 18 from a main outlet 19. The secondary flow comprises an inlet flow 20 and an outlet flow 21 which is generated between a cooling air inlet 22 and a cooling air outlet 24.

The motor 12 includes an additional cooling fan to generate the secondary flow. The cooling fan is typically an axial flow fan, which is not normally very efficient because it is designed for flow generation rather than pressure generation. As a result, the channels to bring the flow to the motor part have to be rather large in diameter. The additional cooling fan also takes up space, typically along the axial direction of the motor. This increase in axial length decreases the resonance frequency of the shaft which means a thicker shaft is required.

In the case of a brush motor, the outlet flow 21 may contain carbon brush particles. This can also have a negative impact on the dust emission of the complete appliance, or else an extra set of filters may have to be added in the bypass circuit.

There is therefore a need for an improved pump design to implement a secondary cooling flow. A vacuum cleaner with a means for cooling the motor is known from for instance EP0650690A1.

SUMMARY OF THE INVENTION

The invention is defined by the claims.

According to examples in accordance with an aspect of the invention, there is provided a pump for use in a vacuum cleaner for generating a suction for application to a vacuum cleaner dirty air inlet, comprising: a motor outer casing; a motor part in the motor outer casing; a fan outside the motor outer casing, driven by the motor part, having a main inlet and a main outlet, wherein the fan generates a main suction flow between the main inlet and the main outlet and creates a region of under pressure; a cooling air inlet to the motor outer casing; a cooling air outlet from the motor outer casing; and a fluid coupling between the cooling air outlet and the region of under pressure such that a secondary flow of air is sucked through the cooling air inlet resulting in a cooling of the motor, wherein the cooling air inlet (22) and the main suction flow (16,18) are separated from each other.

This pump has a motor which drives a fan to generate a main suction flow.

The main suction flow for example carries dust and air, and optionally also water for a wet vacuum cleaner, through a dirt management system. The dirt management system is typically upstream of (i.e. before) the pump. A separate secondary air flow provides motor cooling, so that the main suction flow is not used for cooling. The secondary air flow is induced by making use of an under pressure generated by the fan. Thus, the secondary air flow does not need a separate fan. Instead, an under pressure generated by the fan is used to draw into and out of the motor outer casing. Air may be drawn in from the cooling air inlet (and displacement causes air to be expelled from the cooling air outlet) or it may be drawn out from the cooling air outlet (and displacement causes air to be drawn in from the cooling air inlet). The air delivered to the cooling air inlet is for example from the ambient surroundings.

The dirty air inlet may be a nozzle, tube, cleaning head or any other vacuum accessory.

The secondary flow results in a bypass motor design. The invention enables a standard dry pump assembly to be used with only minor adaptation. In particular, only the main flow fan is used.

The cooling air inlet and the main suction flow are separated from each other in the sense that there is no path in use from the main suction flow to the cooling air inlet. This may rely both on the physical passageways but also the pressure differentials that arise in use. The main suction flow is thus not used for cooling of the motor and it is prevented that the main suction flow enters the cooling air inlet and thereby forms the secondary flow.

The fan is preferably located inside a fan casing. The fan casing may be used to provide pressure differentials between different areas, and thus may have a role in defining the pressure levels to promote the secondary flow.

The region of under pressure created by the fan is preferably located at least partially inside the fan casing and outside the motor outer casing.

In a first example, the region of under pressure created by the fan couples to an inlet side of the fan.

In this case, the region of under pressure is fully outside the motor outer casing. The secondary flow then defines a passageway between an inner volume of the motor outer casing and the inside of the fan casing at the inlet side of the fan. Once the secondary flow reaches the inlet side of the fan, it combines with the main flow.

In a second example, the region of under pressure created by the fan is located adjacent the motor outer casing and couples to the inside of the motor outer casing.

In this case, the fan generates an under pressure which couples to the inside of the motor outer casing, but with separation provided between that area of under pressure and the main suction flow.

For this purpose, the fan may have a front side outside the motor outer casing and a back side which faces and couples to the inside of the motor outer casing, wherein the front side generates the main suction flow and the back side acts as a pump to generate said region of under pressure.

Thus, the fan is used to generate the region of under pressure for the secondary flow using a back of the fan. The fan has front and back functional parts. The back part of the fan functions as compressor to generate a pressure differential and this couples to the inside of the motor casing. The boundary between the front and back sides of the fan provides separation between the main suction flow (on the front part of the fan) and the secondary flow (on the back part of the fan).

However, the main flow and the secondary flow may combine downstream of the motor outer casing to create a combined air outlet.

The fluid coupling for example couples to a region of maximum under pressure at the front side of the fan or at the back side of the fan. This enables a greatest possible secondary flow to be generated.

The main inlet may be an axial inlet in front of the fan and the main outlet may be a radial outlet. The use of a radial fan in this way generates a large under pressure, and is therefore particularly suitable for generating the desired secondary flow. However, other fan types may be used such as a mixed flow or an axial fan.

The main outlet of a radial fan is for example directed around the outside of the motor outer casing. The flow may thus also provide a cooling function around the outside of the motor outer casing.

The cooling air inlet is for example coupled to the ambient surroundings.

Thus, ambient air is used for the secondary flow.

The motor is for example a brushless dc motor or a permanent magnet dc motor.

The invention also provides a pump and filter unit, comprising: the pump as defined above; and a filter section downstream of the pump.

By having a filter section downstream of the pump, the secondary air flow, namely the cooling air flow, may also be subjected to filtering before it is expelled back to the ambient surroundings, in the same way as the main air flow. If using a brushed motor, the cooled air can include entrained carbon particles. Thus, a post motor filter will also filter these carbon particles.

The invention also provides a vacuum cleaner, comprising: a main body including the pump as defined above; a vacuum cleaner dirty air inlet coupled to the main body for receiving a suction generated by the pump; and a dirt separation unit upstream of the pump.

The use of a bypass motor (with a separate secondary cooling air flow) is particularly desirable for a flow which contains water, since the water content is prevented from being used a part of the cooling process. The design is thus suitable for a wet vacuum cleaner.

There is for example also a filter section through which the flow generated by the pump is passed, the filter section being downstream of the pump. This downstream filter processes both the main suction flow and the secondary flow, downstream of the pump.

The vacuum cleaner may further comprise control electronics, wherein the control electronics is cooled by the secondary flow of air. Thus, in this way, the cooling circuit not only cools the motor but also cools the electronics.

The vacuum cleaner may further comprise control electronics, wherein the control electronics is cooled by the secondary flow of air, after the secondary flow of air has cooled the motor.

The vacuum cleaner may further comprise control electronics, wherein the control electronics is cooled by the secondary flow of air, before the secondary flow of air enters the motor outer casing. Thus, the control electronics can also be cooled by a dry air stream.

The invention also provides a method of cooling a motor of a vacuum cleaner pump which is for driving a fan to generate a main suction flow and a region of under pressure, the main suction flow being for application to a vacuum cleaner dirty air inlet, and the motor being contained within a motor outer casing, the method comprising: providing a fluid coupling between a cooling air outlet of the motor outer casing and the region of under pressure, such that a secondary flow of air is sucked through the cooling air inlet resulting in a cooling of the motor.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment s) described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

Figure 1 shows a typical configuration of a pump with a bypass motor and fan; Figure 2 shows in schematic form an arrangement in accordance with the invention;

Figure 3 shows a perspective view of one example embodiment of the pump; Figure 4 shows a cross section through the pump of Figure 3.

Figure 5 shows another cross section for the same design as Figure 4;

Figure 6 shows a cross section through a second example embodiment of the pump.

Figure 7 shows one example of a vacuum cleaner to which the pump has been applied.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The invention will be described with reference to the Figures.

It shall be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

The invention provides a pump for generating a suction for application to a vacuum cleaner dirty air inlet, for example for connection to a suction head, nozzle, brush or any other suitable accessory. There is a motor inside a motor outer casing and a fan outside the motor outer casing having a main inlet and a main outlet. The fan generates a main suction flow between the main inlet and the main outlet and creates a region of under pressure. This under pressure is used to drive a secondary flow between a cooling air inlet to the motor outer casing and a cooling air outlet from the motor outer casing. The secondary air flow is induced by making use of an under pressure generated by the fan.

The invention thus makes use of the main fan for creating a secondary cooling air flow. The main fan can be designed to be very efficient. As a result, the cooling for the motor part is achieved with lower losses.

The main fan is for example a radial fan, providing high pressure compared to an axial fan as normally used for cooling fans. The cooling circuit can therefore tolerate higher pressure drops, and can therefore use fluid connections which are smaller in diameter.

Since no fan is added to the motor part for the secondary air flow, the pump, can be optimal in size with no need for additional space to accommodate a cooling fan.

Figure 2 shows in schematic form an arrangement in accordance with one example of the invention. Figure 2 shows a cross section through the pump of Figure 1 with a modification of the invention explained in general terms.

The entrance flow 16 is received at a main inlet 17 and the exit flow is delivered from a main outlet 19.

The motor comprises a motor outer casing 30 and an internal motor part 32 inside the motor outer casing 30. The fan 14 comprises a fan casing 40 as mentioned above and a fan unit 42 (i.e. a fan blade arrangement). The motor drives an output shaft 34 at one end of which is mounted the fan unit 42. Between the fan and the motor casing 30 is a diffuser 15. A motor spindle passes through the diffuser 15 to couple with the fan. The diffuser comprises a set of blades for controlling flow characteristics to create desired flow and pressure conditions.

A diffuser is a standard part of a vacuum pump design, for controlling the flow characteristics of the fan 40 . Different designs are possible for the diffuser.

The fan unit 42 generates an under pressure which is used to draw cooling air into the motor outer casing 30.

Arrow 44 shows that, in accordance with one example, an under pressure at the fan inlet can be coupled to the cooling air outlet 24 so that air is sucked from the outlet 24 and this is replenished by air drawn in from the cooling air inlet 22.

An alternative (not shown) is that an under pressure generated by the fan is used to draw air in from the cooling air inlet 22 into the inside of motor casing 30 as the inlet flow 20.

The expelled outlet flow 48 rejoins the main suction flow. Figure 2 thus shows in schematic form the concept of the invention as applied to conventional pump single fan pump, in particular by coupling a cooling flow outlet to a low pressure region of the fan.

The operation of the fan results in a region 49a of under pressure. Inside the fan casing 40 of a centrifugal radial fan, the pressure is always lowest at the center and it gradually increases and changes to an over pressure towards the outside of the casing. Thus, there is a radially outer region 49b of over pressure. The kinetic energy of the fan blades create a centrifugal force acting on the air and thus accelerate the air towards the radial outside of the casing. Air enters the fan casing in an axial direction and leaves in a radial direction.

There is a fluid coupling between the cooling air outlet 24 and the region of under pressure (in this example at the fan inlet side) such that the secondary flow of air is sucked through the cooling air inlet 22 resulting in a cooling of the internal motor part 32.

By combining the cooling air with the main suction flow, the cooling air flow is cleaned of carbon particles (in the case of a brush based motor) by the same filter set (downstream of the pump) as is used to clean the main suction air flow. This allows low emissions without the need to add additional filters for the cooling air flow.

Figure 3 shows a perspective view of one implementation of the pump.

Figure 3 shows that cooling outlet flow 21 and main exit flow 18 combine and mix to form the overall air flow path which proceeds downstream.

An isolating ring 50 is provided around the pump for isolating the inlet flow 20 from the outlet flow 21 and main exit flow 18. The isolating ring 50 together with an overall casing can prevent interaction between the outlet flow 21, main exit flow 18 and the inlet 22 or inlet flow 20. The outlet flow 21 and main exit flow 18 are for example routed to an outlet tube while the back of the pump, at which the cooling air inlet 22 is formed, is isolated from the main flow 16, 18. The cooling air inlet couples to the ambient surroundings.

Figure 4 shows a cross section through one implementation of the pump of Figure 3. This is for an example in which an under pressure generated by the fan is used to draw air in from the cooling air inlet 22 into the inside of motor casing 30 as the inlet flow 20

The fan unit 42 has a front side 42a outside the motor outer casing 30 and facing outwardly, and a back side 42b facing inwardly. The back side 42b couples fluidly to the inside of the motor outer casing 30. The front side 42a generates the main suction flow, and in the example shown is a radial fan. Between the fan unit 42 and the motor outer casing 30 is the diffuser 15.

The back of the fan is separate from the front of the fan because it has a structure of a solid plate which carries the fan blades. Thus, the passage of moisture from front to back is prevented.

The back side 42b of the fan unit 42 also acts as a pump to generate the region of under pressure. There are fluid passageways 60 in a front wall (i.e. the axial end proximal the fan) of the motor outer casing 30, and fluid passageways 61 in the wall of the diffuser 15. These passageways fluidly couple the inside of the motor outer casing 30 to the back side 42b of the fan unit 42.

The back side 42b of the fan unit 42 has a pressure gradient, with a lowest pressure near the axis of rotation and a maximum pressure at the radially outermost extremity. The cooling air outlet from the motor casing is formed by the internal fluid passageways 60, 61 which connect to the radially inner area. Preferably, they connect to the region of greatest under pressure (i.e. the lowest absolute pressure) at the back side 42b.

The back side 42b of the fan unit 42 may be a planar disc which is spaced from a front wall of the diffuser 15. The friction between the back side 42b of the fan arrangement and the air trapped in the spacing generates a flow and pressure gradient, and thus functions as a pump.

While a planar back side 42b of the fan unit 42 is sufficient, fan blades may be added to the back side so that the flow can be increased. Radial blades for example can also be used.

Thus, the fan is used to generate the region of under pressure for the secondary flow using a back of the fan. The fan thus has front and back functional parts. The back functional part functions as compressor to generate a pressure differential and this couples to the inside of the motor casing. The boundary 62 between the front and back sides 42a, 42b of the fan unit provides some separation between the main suction flow (between the entrance flow 16 and the exit flow 18) and the secondary flow (between the inlet flow 20 and the outlet flow 21) so that these two flows do not (or only minimally) interact with each other.

However, the main flow and the secondary flow in this example combine downstream of the motor outer casing to create a combined air outlet. The cooling air outlet from the motor casing is at the internal passageways 60 and 61, whereas the eventually output air flow is delivered from the main outlet 19. The outlet flow 21 couples to the region of under pressure created by the fan. There is a fluid coupling between this region of under pressure and the inside of the motor outer casing.

The direction of the secondary flow is for example constrained by the fan rotation. Thus, a region of under pressure is created adjacent the passageways, and the flow direction means the air must be drawn from the motor outer casing (rather than being drawn from the radially outer part of the fan into the motor outer casing).

The fluid coupling has to be located in an area where the under pressure created by the fan can be localized and transferred. For this purpose, a resistance is present around the fan unit. The casing also acts as a resistance since otherwise the fan is exposed to the atmospheric pressure.

There may also be a pre-motor filter in front of the fan, which is a part of the dirt management system. This filter provides a resistance and thus the areas surrounding the fan will have a negative pressure relative to the atmospheric pressure.

For the example of Figure 6, if the upstream resistance i.e. in front of the fan is not present then the under pressure at the area where the cooling outlet is coupled might be lost. If the pressure at the region to which the cooling outlet is coupled is at atmospheric pressure, the differential pressure is lost and the cooling flow will be lost. Thus, the flow resistance may pay a role in establishing the required pressure gradients in the system.

The pressure generated by the fan is dependent on the flow. However, even if the main suction flow is totally blocked, the secondary cooling flow will still be available to prevent overheating as it is generated based on a pressure differential separate from the main suction flow. Indeed, if the main suction flow is blocked, the motor runs without any flow resistance, and this means the motor and fan perform at peak efficiency, thereby creating a highest negative pressure. A maximum volume of cooling air will then be drawn in.

In this way, the system does not need conventional safety sensors for opening a safety valve when a main inlet is blocked. In conventional systems, the main suction flow is the cooling flow, so an interruption to the main suction flow will result in overheating of the motor.

The back of the fan unit is also the most consistent area for generating the required under pressure, as it acts as an independent pump. The back of the fan unit does not need to be shaped as an impeller but can simply be a solid disc. This solid disc will induce pressure variations which are predictable and repeatable. Fan blades may however be added. The pressure differences caused by the various flows are designed to avoid flow in the undesired directions. For example, since the outlet flow 21 and the exit flow 18 combine, there is a physical (static) connection between the entrance flow 16 and the inlet flow 20 (since they both couple to the exit flow 18). However, the flow conditions prevent the entrance flow 16 coupling back to the inlet flow 20 and thereby contaminating the secondary air flow.

Figure 5 shows another cross section for the same design as Figure 4, with an additional outer casing 70 around the pump. The casing has a casing inlet (not shown) which is fluidly coupled to the cooling air inlets 22 in chamber 70a. It has a casing outlet which is isolated from the cooling air inlets 22 by the isolating ring 50 and couples to chamber 70b.

In the design of Figures 4 and 5, it is possible that some drops of moisture from the moisture laden air that is transferred by the fan can end up or accumulate at the ends of the diffuser 15 where the flow leaves the fan and enters the diffuser blades. There is a chance that when the appliance is in various orientations the water that is accumulated on the diffuser 15 can ingress or creep into the gap between the fan unit 42 and the diffuser 15 and then enter the motor compartment.

In order to counter this situation the fan may be made as wide as or wider than the diffuser 15 so that moisture does not accumulate at the ends of the diffuser. Also, a back part of the diffuser that faces the motor housing can have legs that can isolate the central part of the top casing of the motor.

Figure 6 shows a second example. It also shows some of the additional parts around the pump.

The example of Figure 6 also makes use of a region of under pressure created by the fan, but it couples to an inlet side of the fan, in the manner schematically shown in Figure 2. The fluid coupling for example couples to a region of maximum under pressure at the inlet side of the fan.

There is again an outer casing 70 with a casing inlet 71. The casing couples to a post motor filter 72. The casing volume is fluidly coupled to the post motor filter 72 by an opening 74 in the casing. This opening 74 lets moist air and circulated cooling air out to the filter 72.

The fan also has a pre motor filter 76 in front of the fan. This functions as a resistance element to create a desired pressure drop so that the pressure at the main inlet is below atmospheric pressure. The pre-motor filter is a part of the dirt management system. The cooling air inlet 22 is again formed by the openings in the back of the motor casing. The cooling air outlet from the motor casing is formed by an internal passageway 80 which is connected to the region of under pressure. For example, a chamber 82 is formed which in this example is coupled to the front of the fan, such that the region of under pressure is transferred to the chamber 82.

The chamber 82 is then used to draw the secondary air flow from the motor outer casing 30 via the internal passageway 80.

This example shows that the front of the fan may be used as the source of under pressure, and the secondary air flow does not need to pass the back of the fan.

Figure 6 also shows pressure levels PI to P6 along the cooling air flow path. The pressure level P4 at the region of under pressure is below 1 Atm (100 kPa) because of the filter 76, and after that the cooling flow is entrained with the main flow.

By way of example, PI = P6 = 1 Atm (100 kPa).

P4 is the region of maximum under pressure around the fan inlet, such as 20 kPa below atmospheric pressure.

P3 is at an under pressure is marginally less than P4.

P2 is at an under pressure marginally less than P3.

P5 is at a maximum overpressure, such as 2 kPa above atmospheric pressure.

These are examples of the pressures in a normal working condition.

There is again a diffuser 15 but it has no major role in controlling the cooling flow.

The main flow enters as 16 and exits as 18 from the casing through the opening 74 and is not connected to the internal passageway 80 and chamber 82. The connection of the internal passageway 80 to an area of under pressure means it can draw air from the inlet 71 and then out through the chamber 82.

The internal structure of the pump arrangement ensures the cooling air does not short circuit to the outlet. This makes sure the drawn in air does pass through the motor casing and then to the outlet. A ring 84 for example ensures there is a defined path through the pump arrangement which passes through the motor casing.

Thus, the underlying concept between these approaches is to use the fan, in particular an under pressure region created by the fan, to draw a stream of cooling air as a secondary flow from the ambient surroundings into the motor casing.

In the first example, the back of the fan is used to create the under pressure. In this case, use is made of a set of holes 60, 61 in the motor outer casing and diffuser facing the back of the fan. These function as the cooling air outlet. The diffuser and the back side of the fan provide the required pressure gradients. Holes on the outer wall of the motor casing will act as the outlet.

In a second example, the front of the fan is used to create the under pressure. The front of the fan is connected to a cooling air outlet 80 of the motor casing through a chamber 82 that also receives the under pressure. A filter or other structure provides the required pressure gradients.

The arrangement of Figures 4 and 5 above is based on a fluid coupling to the back of the fan unit whereas Figure 6 is based on a fluid coupling to the front of the fan. Either approach may be used. However, when the air cooling outlet is coupled to the front of the fan it will have variations in the under pressure level because this under pressure level will depend on the resistance that is connected in front of the fan (e.g. the fan) or around it (e.g. the fan casing design). This flow resistance is for example introduced by the dirt management system or by the type (or state of blockage) of the vacuum nozzle. If the resistance changes, the under pressure level will differ and thus the cooling flow that is generated will also vary.

The use of the back of the fan as the pressure generating mechanism is thus more consistent.

The back of the fan also does not generate noise and as long as the fan is rotating with a suitable revolution speed, the generation of under pressure will be effective. Typically, the motor will rotate at a known and consistent speed, so the back of the fan will generate a region of consistent under pressure.

In all examples, electronic components such as the main PCB and controller can be located upstream (in the sense of the flow of cooling air) of the motor, so that the inlet flow 20 passes and cools the electronics before entering the cooling air inlet 22 and eventually cooling the motor part 32. In this way, the cooling circuit not only cools the motor but also cools the electronics. The air can be cold enough that it can still cool the motor after it has passed through the electronics. The electronics can thus be cooled by the secondary airflow and isolated from the main flow as the moisture laden main flow can adversely affect the electronics by destroying or corroding them.

Similarly in all examples, electronic components such as the main PCB and controller can be located downstream (in the sense of the flow of cooling air) of the motor, so that the inlet flow 20 enters the cooling air inlet 22 and cools the motor part 32 and thereafter eventually passes and cools the electronics. The sequence of first cooling the electronics and then cooling the motor is generally preferred in case of a permanent magnet DC motor as that avoids pollution of the electronics. To further elaborate, the air that is exhausted from the permanent magnet DC motor may carry carbon particles and hence is not suitable that it is then fed as air for cooling the electronics.

However, in case of a brushless DC motor, the sequence of first cooling the motor and then the electronics or the other way around is considered to be generally equally effective. This is because the air that is exhausted from a brushless DC motor is typically not contaminated by such particles due to the absence of carbon brushes in the motor, and thus is suitable for cooling the electronics even after passing the motor. Therefore, the cooling sequence can be adapted, in whichever way as mentioned above depending on the type of motor, to not only to cool the motor but also the electronics.

Figure 7 shows a wet vacuum cleaner 100, comprising a vacuum cleaner head 112, and a pump (motor 114 and fan 116) for delivering suction to the vacuum cleaner head. The vacuum cleaner head connects to a dirty air inlet of the main body of the vacuum cleaner.

A cyclone unit 118 is provided for separating liquid and particles from a flow generated by the suction of the motor and fan.

The motor comprises the bypass motor as described above, with a secondary flow of air for cooling. This type of motor can tolerate water content in the air flow, because the drawn in air flow is not used for motor cooling and is isolated from the motor parts. Instead, ambient air is drawn in to the motor for cooling purposes as described above.

The cyclone unit 118 is part of a wet dirt management system upstream of the pump. It has a collection chamber 128 for collecting the separated moisture and dirt (i.e. a waste water collection reservoir). A filter section 120 is provided between the outlet flow of the cyclone and the motor and fan, and an outlet filter section 121 is provided downstream of the pump for filtering the combined main flow and secondary flow before it is expelled to the ambient surroundings.

Figure 7 also schematically shows control electronics 122, wherein the control electronics is cooled by the secondary flow of air, before the secondary flow of air enters the motor outer casing.

The cyclone has a cyclone axis of rotation 124. This axis may be parallel to the inlet flow direction (as shown) or it may be perpendicular, depending on the configuration. The collection chamber 128 is for example below the cyclone chamber (when the vacuum cleaner is upright) so that water is collected under gravity. There is a handle 130 at the opposite end to the head 112.

The vacuum cleaner shown is a stick vacuum cleaner. Of course, it may be an upright vacuum cleaner or a drum vacuum cleaner. The invention relates to design features of the motor and fan, and may be applied to any wet vacuum cleaner.

The user may be required to deliver water to the surface being vacuumed independently of the vacuum cleaner. However, the wet dirt management system may instead also include a clean water reservoir for delivering water to the vacuum nozzle. The vacuum cleaner head for example has a rotary brush to which water is delivered from the clean water reservoir.

Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

If the term "adapted to" is used in the claims or description, it is noted the term "adapted to" is intended to be equivalent to the term "configured to". Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. A pump for use in a vacuum cleaner for generating a suction for application to a vacuum cleaner dirty air inlet, comprising: a motor outer casing (30); a motor part (32) in the motor outer casing; a fan (14) outside the motor outer casing (30), driven by the motor part (32), having a main inlet (17) and a main outlet (19), wherein the fan (14) generates a main suction flow (16, 18) between the main inlet and the main outlet and creates a region (49a) of under pressure; a cooling air inlet (22) to the motor outer casing; a cooling air outlet (60,61; 80) from the motor outer casing; and a fluid coupling between the cooling air outlet and the region of under pressure (49a) such that a secondary flow of air (20) is sucked through the cooling air inlet (22) resulting in a cooling of the motor, wherein the cooling air inlet (22) and the main suction flow (16,18) are separated from each other.

2. The pump as claimed in claim 1 , wherein the fan (14) is located inside a fan casing (40) and wherein the region of under pressure created by the fan is located at least partially inside the fan casing (40) and outside the motor outer casing (30).

3. The pump as claimed in any one of claims 1 or 2 , wherein the region of under pressure created by the fan couples to an inlet side of the fan.

4. The pump as claimed in claim 3 , wherein the fluid coupling couples to a region of maximum under pressure at the inlet side of the fan.

5. The pump as claimed in any one of claims 1 to 4 , wherein the region of under pressure created by the fan is located adjacent the motor outer casing couples to the inside of the motor outer casing.

6. The pump as claimed in claim 5 , wherein the fan has a front side (42a) outside the motor outer casing and a back side (42b) which faces and couples to the inside of the motor outer casing, wherein the back side acts as a pump to generate said region (49a) of under pressure.

7. The pump as claimed in claim 6 , wherein the fluid coupling couples to a region of maximum under pressure within the front side of the fan or the back side of the fan.

8. The pump as claimed in any one of claims 1 to 7 , wherein the main outlet (19) is directed around the outside of the motor outer casing.

9. The pump as claimed in any one of claims 1 to 8 , wherein the motor part (32) comprising: a brushless dc motor; or a permanent magnet dc motor.

10. A pump and filter unit, comprising: the pump as claimed in any one of claims 1 to 9 ; and a filter section downstream of the pump.

11. A vacuum cleaner, comprising: a main body including the pump as claimed in any one of claims 1 to 9 ; a vacuum cleaner dirty air inlet coupled to the main body for receiving a suction generated by the pump; and a dirt separation unit upstream of the pump.

12. A vacuum cleaner as claimed in claim 11 , further comprising a filter section through which the flow generated by the pump is passed, wherein the filter section is downstream of the pump.

13. A vacuum cleaner as claimed in claim 11 or 12, further comprising control electronics, wherein the control electronics is cooled by the secondary flow of air.

14. A vacuum cleaner as claimed in claim 11 or 12 , further comprising control electronics, wherein the control electronics is cooled by the secondary flow of air, before the secondary flow of air enters the motor outer casing.

15. A method of cooling a motor of a vacuum cleaner pump which is for driving a fan to generate a main suction flow and a region of under pressure, the main suction flow being for application to a vacuum cleaner dirty air inlet, and the motor being contained within a motor outer casing, the method comprising: providing a fluid coupling between a cooling air outlet of the motor outer casing and the region of under pressure, such that a secondary flow of air is sucked through the cooling air inlet resulting in a cooling of the motor , wherein the cooling air inlet and the main suction flow are separated from each other.