VACUUM CLEANING DEVICE WITH AT LEAST TWO MOTORS

Abstract

 Summary
The invention refers to a vacuum cleaning device (2) comprising:
- a dust collecting chamber (6) with at least one inlet port (10) for dust-laden air (9) and at least one outlet port (12),
- at least one filter element (14) located between the at least one outlet port (12) and the rest of the dust collecting chamber (6),
- at least two motors (18, 20) each driving an air blower (22, 24) for drawing air from the dust collecting chamber (6) through an air outlet (26, 28) of the vacuum cleaning device (2), thereby creating a depression in the dust collecting chamber (6), and
- a control unit (32) for controlling the operation of the at least two motors (18, 20).
In order to provide for a high availability of the vacuum cleaning device (2) it is suggested that the control unit (32) is adapted to automatically operate only one of the motors (18, 20) upon activation of the vacuum cleaning device (2).

Description

[0001] The present invention refers to a vacuum cleaning device comprising:

• a dust collecting chamber with at least one inlet port for dust-laden air and at least one outlet port,
• at least one filter element located between the at least one outlet port and the rest of the dust collecting chamber,
• at least two motors each driving an air blower for drawing air from the dust collecting chamber through an outlet port and discarding the air into the environment through an air outlet of the vacuum cleaning device, thereby creating a depression in the dust collecting chamber, and
• a control unit for controlling the operation of the at least two motors.

[0002] Vacuum cleaning devices with two motors are well-known in the prior art. For example, EP 1 629 762 A2 describes a vacuum cleaning with two motors, which suck dust-laden air into the dust collecting chamber via a common inlet port. Each motor is fitted with its own filter element on the input side of the motor and with its own outlet valve on the output side of the motor. The known vacuum cleaning device can be operated in two different modes of operation, a normal suction mode and a filter cleaning mode. In the normal suction mode both motors are operated contemporarily. From time to time, the vacuum cleaning device is temporarily switched from the normal suction mode into the filter cleaning mode during which the filter elements are cleaned sequentially one after the other. In the filter cleaning mode, first one motor is turned off, the respective output valve is closed and the respective filter element is cleaned. During cleaning of the first filter element, the other motor is maintained in operation thereby maintaining the vacuum cleaning functionality. After cleaning of the first filter element, the first motor is turned on again and the respective output valve opened. The other motor is turned off, the respective output valve is closed and the respective filter element is cleaned. During cleaning of the second filter element, the first motor is in operation thereby realizing the vacuum cleaning functionality. When the known vacuum cleaning device is activated, it is in its normal suction mode and both motors are operated contemporarily.

[0003] The problem of the known vacuum cleaning device is that during normal vacuum cleaning functionality all motors are operated. Even though the motors may be operated at a reduced speed, they still operate more or less continuously whenever the vacuum cleaning device is activated. Even an operation of the motors at reduced power provokes wear and aging of the motors. On the long run, this may lead to an accelerated aging and fatigue of the motors resulting in a reduced availability of the vacuum cleaning device due to a motor failure.

[0004] Therefore, it is an object of the present invention to provide for a particularly robust and reliable vacuum cleaning device having a particularly high availability.

[0005] This object is solved by a vacuum cleaning device comprising the features of claim 1. In particular, a vacuum cleaning device of the above-mentioned kind is suggested, wherein the control unit is adapted to automatically operate only one of the at least two motors upon activation of the vacuum cleaning device.

[0006] After activation of the vacuum cleaning device, it is in its normal suction mode. The normal suction mode after activation of the vacuum cleaning device is realized by the operation of only one of the motors. The advantage of the invention is that with the vacuum cleaning device active and in its normal suction mode, only one motor is operated and the other motor(s) can rest. When the vacuum cleaning device is activated the next time, preferably another one of the motors, which was previously at rest, may be operated and the other motor(s) can rest. On the long term the aging and fatigue of the motors is significantly decelerated resulting in a far longer life cycle of the motors and a higher availability of the vacuum cleaning device. Preferably, the active motor is being operated in its ideal point of operation (nominal speed). However, it is also possible that the motor is operated at its maximum speed or any other speed between above zero and the maximum speed. A controller may be provided in order to set the speed of the active motor to a desired value.

[0007] It is noted that dust in the sense of the present invention comprises all sorts of small particles which may be sucked in by the vacuum cleaning device when in its activated mode. It may comprise dust particles consisting of organic materials (e.g. flower pollen, bacteria, fungal spores) or inorganic materials (e.g. rock dust, mineral fibres, dirt, sand). In particular, dust in the sense of the invention comprises small (e.g. abrasive) particles, in particular consisting of wood, metal, plastic, varnish, lacquer, filler, compound material, polishing agent, etc.

[0008] According to a preferred embodiment of the present invention it is suggested that the control unit is associated with a storage unit for storing a value indicative of the operational time of each of the motors, and wherein upon activation of the vacuum cleaning device, the control unit is adapted to read out the values from the storage unit, to compare the values and to select and operate that motor having the shortest operational time of all motors. This embodiment has the advantage that on the long run, the motors of the vacuum cleaning device, although they are operated successively one after the other, are operated for a similar amount of operational time. If one of the motors is operated only for a short period of time, it may be that it is operated one or more times consecutively as long as it still has the smallest overall operational time of all motors. Hence, the motors of the vacuum cleaning device are not necessarily operated in a strict order or sequence one after the other each time the vacuum cleaning device is activated.

[0009] Preferably, the storage unit is adapted to maintain the stored values even when no electric power is applied to the storage unit, e.g. when the vacuum cleaning device is deactivated. In that case electric power may only be required for storing and reading out the values. The storage unit may be, for example, an EPROM or an EEPROM.

[0010] Preferably, the control unit is adapted to monitor the operational time of each of the motors during operation of the vacuum cleaning device and to store updated values for the operational times of the motors in the storage unit. Upon a new activation of the vacuum cleaning device, the control unit can read out the values for the operational times of the motors, which have been stored in the storage unit during or after previous activation(s) of the vacuum cleaning device, from the storage unit and compare them with each other. The motor having the shortest operational time is selected and put into operation by the control unit. The reading-out of the values from the storage unit, the comparison of the values, the selection of the motor to be operated and the putting-into-operation of the selected motor is effected almost in real-time. The user of the vacuum cleaning device will not recognize any delay between activation of the vacuum cleaning device and starting of one of the motors. The selection of the motor for operation is effected automatically in the background unnoticeable by the user. The automatic selection of the motor for operation has the advantage that no user-errors (selection of the wrong motor) may occur, which could be the case with a manual selection.

[0011] The updated values indicative of the operational times of the motors may be continuously (or regularly, e.g. every 5 seconds to 30 minutes), stored in the storage unit during operation of the vacuum cleaning device. Preferably, the control unit is adapted to store the updated values indicative of the operational times of the motors in the storage unit after deactivation of the vacuum cleaning device. During operation of the motor, the current operational time of this activation cycle is recorded and upon deactivation of the vacuum cleaning device added to the previously stored value and finally the updated value stored in the storage unit. Of course, in this case, after deactivation of the vacuum cleaning device the electric power should continue to be present at the control unit and the storage unit until the updated value(s) of the operational time(s) has (have) been stored in the storage unit.

[0012] It is further suggested that the control unit is adapted to monitor an electric operational value at least of the operating motor during operation of the vacuum cleaning device and to deduce from the monitored value whether the operating motor is properly functioning or not. The "operating motor" would be the motor previously selected by the control unit for operation upon activation of the vacuum cleaning device, even if the motor is actually not running due to a defect. For example, the control unit can monitor the electric current drawn by the operating motor. If an operating motor or a motor which should be operating is found not to draw the expected amount of electric current or far more electric current than expected, it is considered to have a defect. Monitoring of the electric current may be realized by defining a window for the expected amount of current to be drawn during normal operation of a properly functioning motor, e.g. between 5 A and 12 A. The control unit verifies whether the electric current currently drawn by the motor is within the defined window. If not, a malfunction or defect of the motor is diagnosed.

[0013] The control unit is adapted to turn off the defect motor and to operate another motor of the vacuum cleaning device if the operating motor is found not to operate properly. This significantly improves availability of the vacuum cleaning device. The vacuum cleaning device may be provided with at least one LED or the like for signalling to a user a malfunction and/or a proper functioning of the motors of the vacuum cleaning device. Preferably, a separate LED is provided for each of the motors. The LEDs may be multi-colour LEDs signalling a proper functioning of at least one of the motors with a light signal in a first colour (e.g. green) and a malfunction of the motor with a light signal in another colour (e.g. yellow or red). The signalling may also be effected by means of a continuous or flashing light signal or the like.

[0014] According to yet another preferred embodiment of the present invention, during operation of only one of the at least two motors upon activation of the vacuum cleaning device, the operating motor draws air from the dust collecting chamber through all filter elements and the air outlet of the vacuum cleaning device, thereby creating the depression in the dust collecting chamber. In this embodiment, the motor currently operating uses all available filter elements in the vacuum cleaning device, thereby filling the filter element(s) equally and uniformly with dust. Hence, even is only one motor is running, all filter elements and all air outlet of the vacuum cleaner are used by the one operating motor.

[0015] It is further suggested that the dust collecting chamber has a separate outlet port assigned to an input side of each of the motors and that an inlet valve is located in each of the outlet ports, each inlet valve being open during operation of the motor assigned to the inlet valve and being closed during rest of the motor assigned to the inlet valve. Preferably, the inlet valves are embodied as non-return valves automatically closing due to the depression in the dust collecting chamber when the respective motor is turned off. When a motor is turned on, it draws air from the dust collecting chamber through the or all filter element(s), the respective outlet port assigned to the motor in operation and the air outlet of the vacuum cleaning device. Due to the air flow the non-return valve assigned to the operating motor is automatically opened. All other inlet valves are closed, thereby closing the outlet ports assigned to the inactive motors and effectively sealing the dust collecting chamber, thereby allowing the air flow only through the outlet port assigned to the operating motor. This significantly enhances efficiency of the vacuum cleaning device.

[0016] According to another preferred embodiment of the invention, it is suggested that the control unit is adapted to control the speed of the motor turned on upon activation of the vacuum cleaning device and to reduce or increase the speed of the motor depending on an external request. Hence, the operating motor does not always have to run at its nominal or maximum speed but can be operated at a reduced speed if desired. This reduces the consumption of electric energy during operation of the vacuum cleaning device. If the vacuum cleaning device has to aspire only a small amount of dust or dust from only one or few external power tools attached thereto by means of a suction hose, the motor speed can be reduced. If the vacuum cleaning device has to aspire a larger amount of dust or dust from a plurality of power tools attached thereto, the motor speed can be increased.

[0017] Preferably, the external request for a reduced or increased speed of the motor operating upon activation of the vacuum cleaning device originates from

• a manually operable controller connected to the control unit and located at the outside of the vacuum cleaning device, and/or
• a receiving unit assigned to the vacuum cleaning device and adapted to receive an external signal indicative of the amount of dust to be aspired by the vacuum cleaning device.

[0018] The manually operable controller may be embodied as one or more switches for reducing or increasing the speed of the operating motor to a pre-set value or as a rotary control for gradually reducing or increasing the speed of the operating motor. Preferably, the motor set into operation upon activation of the vacuum cleaning device is operated at the speed, corresponding to the current setting of the switch(es) or the rotary controller, right from the beginning immediately after activation of the vacuum cleaning device.

[0019] The receiving unit is adapted to receive an external signal from a remote control or from an external power tool which generates dust during its operation and which is connected to an inlet port of the dust collecting chamber by means of a suction hose, the external signal indicative of the amount of dust generated by the tool during its operation. The remote control may be part of a smart phone, tablet PC or the like operated by the user of the vacuum cleaning device. In that case, the remote control may be realized as an application (so-called App) running on the smart phone. The power tool may be provided with transmission means for transmitting the external signal to the receiving unit. The receiving unit may be an integral part of the vacuum cleaning device or an external receiving unit, electrically connected to the control unit of the vacuum cleaning device. The external signal is preferably transmitted wirelessly from the remote control or the external power tool, respectively, to the receiving unit according to a desired protocol for wireless signal transmission, e.g. regular BlueTooth, BlueTooth LE (low energy), ZigBee, WiFi or the like.

[0020] Preferably, the control unit is adapted to select one of the motors for operation also depending on the speed with which the motors where previously operated. For example, it is possible that the nominal or the maximum speed of the motors is assigned the factor 1.0, half the nominal or maximum speed may be assigned the factor 0.5. The factor may be calculated based on the average speed of the operating motor during an activation cycle of the vacuum cleaning device. Before storing the value indicative of the operational time of the operated motor in the storage unit, the value may be multiplied with the factor calculated in dependence on the average speed. Then, the product of the time-dependent value and the speed-dependent factor is stored in the storage unit. Upon a new activation of the vacuum cleaning device the motor is selected and set into operation which has the smallest product assigned thereto.

[0021] According to yet another preferred embodiment of the invention, it is suggested that the vacuum cleaning device has a manually operable turbo switch connected to the control unit and located at the outside of the vacuum cleaning device, and wherein the control unit is adapted to operate at least one additional motor upon activation of the turbo switch. The turbo switch allows a short-term activation of more than one motor, preferably of all motors available in the vacuum cleaning device. This may temporarily increase the throughput rate of the vacuum cleaning device, for example in order to aspire larger amounts of dust within a short period of time. To begin with, each time the vacuum cleaning device is activated the turbo switch is deactivated. Hence, the vacuum cleaning device always starts with only one of the motors operating even if during a previous activation of the vacuum cleaning device the turbo switch was activated.

[0022] According to a preferred embodiment, the vacuum cleaning device is a mobile vacuum cleaner with wheels attached thereto or located on a trolley with wheels, in order to freely move the vacuum cleaning device to its work place. Usually, the work place is in a factory, a construction site, a vehicle body repair shop, a paint shop, a shipyard or similar. Hence, in these cases the vacuum cleaning device should have a high availability because it cannot be easily repaired at its work place. Therefore, the present invention is particularly advantageous when realized in mobile vacuum cleaners. It is particularly preferred that the vacuum cleaning device is attached to an external hand guided power tool (e.g. a drill, a polisher, a sander or a grinder) by means of a suction hose. The power tool generates dust in a working area during its operation. The suction hose connects a tool internal dust extraction system (active or passive) with an inlet port of the dust collecting chamber of the vacuum cleaning device. By aspiring the dust from the working area of the power tool, environmental requirements can be fulfilled (only a limited amount of dust in the air is allowed) and the working area can be kept free of dust (a free view of the user on the working area is possible).

[0023] The motors of the vacuum cleaning device are preferably electric motors, although they could also be pneumatic motors. It is suggested that the dust collecting chamber of the vacuum cleaning device has a top cover comprising the motors, the blowers and the control unit. The top cover may comprise all electric and electronic components of the vacuum cleaning device. Any switches, controllers etc. present in the vacuum cleaning device are preferably also attached to the top cover. A power cable for connecting the vacuum cleaning device to a mains power supply is preferably also attached to the top cover. Additionally, the at least one filter element may also be attached to the top cover, in particular to the bottom side of the top cover, below the outlet port(s) of the dust collecting chamber. The top cover can be detached from the rest of the dust collecting chamber in one piece. When attached to the rest of the dust collecting chamber, the connection between the top cover and the rest of the dust collecting chamber is preferably airtight in order to maintain the depression in the chamber and to an allow air flow into the chamber only through the inlet port(s).

[0024] It is further suggested that the dust collecting chamber of the vacuum cleaning device has a front opening closed by a removable front cover, the front opening permitting easy access to the dust collecting chamber without having to open the top cover, in order to replace a vacuum cleaner bag located in the dust collecting chamber and/or to replace the at least one filter element. The front opening may be provided for replacement of the at least one filter element or for removal of the at least one filter element for cleaning and/or for reinsertion of the at least one filter element after cleaning.

[0025] Finally, it is noted that the vacuum cleaning device according to the present invention preferably has no filter cleaning mode. Hence, upon activation of the vacuum cleaning device, it is always operated in the normal suction mode. However, if desired the vacuum cleaning device may be provided with a filter cleaning mode in which the at least one filter element is released from at least some of the dust particles attached to an input side (facing towards the dust collecting chamber, facing away from the outlet port(s)) of the filter element(s). Filter cleaning may be performed for each filter element subsequently or contemporarily for all filter elements. Filter cleaning may be performed by any known filter cleaning method including reverse flushing of the filter element(s) with an air flow directed from the blowers into the dust collecting chamber and vibration of the filter element(s).

[0026] The present invention also refers to a method for controlling a vacuum cleaning device comprising at least two motors according to the above specification. In particular, according to the control method, upon activation (turning on) of the vacuum cleaning device, only one of the motors is operated while the other motor(s) remain turned off and are in a rest mode. The method may be realized in the form of a computer program which may be executed on a central processing unit of a control unit of the vacuum cleaning device.

[0027] Further features and advantages of the present invention are described hereinafter with reference to the accompanying drawings. The various features of the invention, described hereinafter and shown in the drawings can be realized in any combination with each other even though they are described and shown, respectively, in other combinations. The drawings show:

Figure 1

a vacuum cleaning device according to a preferred embodiment of the present invention;

Figure 2

a longitudinal section through a vacuum cleaning device according to the present invention in a schematic view;

Figure 3

a longitudinal section through a top cover of a vacuum cleaning device according to the present invention in a schematic view with a first motor operating;

Figure 4

a longitudinal section through part of a top cover of a vacuum cleaning device according to the present invention in a schematic view with a second motor operating; and

Figure 5

a longitudinal section through part of a top cover of a vacuum cleaning device according to the present invention in a schematic view with both motors operating.

[0028] In Figure 1 a vacuum cleaning device according to the present invention is shown in a preferred embodiment and designated with reference sign 2. The vacuum cleaning device 2 is embodied as a mobile vacuum cleaner with wheels 4 attached thereto. Of course, the invention could also be realized as a static, permanently installed vacuum cleaning device as part of a dust extraction system.

[0029] Vacuum cleaner 2 comprises a dust collecting chamber 6 formed by a dust collecting container 8 of the vacuum cleaner 2. The container 8 forms the bottom part of a vacuum cleaner housing. In the shown embodiment, the container 8 also constitutes a support structure for the entire vacuum cleaning device 2 and for accessories attached thereto. The wheels 4 are attached to the container 8. The chamber 6 has an inlet port 10 for dust-laden air 9 and two outlet ports 12 (see Figure 2). Of course, the dust collecting chamber 6 could also comprise more than one inlet port 10 (the inlet ports not in use must be closed). One end of a suction hose (not shown) may be attached to the inlet port 10. The opposite end of the suction hose may be attached to a nozzle or an external power tool (not shown), e.g. in the form of a drill, a polisher, a sander or a grinder. The power tool generates dust 42 during its operation, which is sucked in by the vacuum cleaner 2 through the suction hose and deposited in the dust collecting chamber 6.

[0030] The vacuum cleaner 2 further comprises a single filter element 14 (see Figure 2) located between the outlet ports 12 and the interior space of the dust collecting chamber 6. Of course, the filter element 14 could also be constituted by at least two filter parts resulting in a single multi-part filter element. In an alternative embodiment, it would also be conceivable that a separate filter element 14 is provided for each of the outlet ports 12. In that case, a single chamber 16 between the filter elements 14 and the outlet ports 12 is preferably hermetically divided into separate sub-chambers by a partition wall 16a (drawn with dashed lines), one sub-chamber assigned to each outlet port 12 and corresponding filter element 14. In the shown embodiment, the single filter element 14 is fitted in front of the outlet ports 12 in an air-tight fashion by means of a gasket 15 or the like. Therefore, all air flowing through the outlet ports 12 must flow through the filter element 14.

[0031] Furthermore, two motors 18, 20 (see Figure 2) are provided in the vacuum cleaner 2, each driving an air blower 22, 24 for drawing air from the dust collecting chamber 6 through an air outlet 26, 28 of the vacuum cleaner 2, thereby creating a depression in the dust collecting chamber 6. The motors 18, 20 are preferably electric motors. Of course, the vacuum cleaner 2 could also be provided with more than two motors. One outlet port 12 is assigned to each of the motors 18, 20. Although a plurality of air outlets 26, 28 are shown, a single air outlet could also suffice. If two separate outlets 26, 28 are provided, a single chamber 30 between the air blowers 22, 24 and the air outlets 26, 28 could be hermetically divided into two sub-chambers by a partition wall 30a, one sub-chamber assigned to each air blower 22, 24 and corresponding air outlet 26, 28. Although not shown, outlet valves for selectively closing/ opening the air outlets 26, 28 could also be provided.

[0032] The vacuum cleaner 2 further comprises a control unit 32 for controlling the operation of the motors 18, 20. The control unit 32 may comprise a printed circuit board (PCB) with a central processing unit (CPU) and other electric and electronic components mounted thereon. A computer program may be executed on the CPU in order to realize the control function of the control unit 32. Signal lines 34 for transmitting control signals from the control unit 32 to the motors 18, 20 are also provided. Instead of the signal lines 34 a data bus system could be used for transmitting the control signals. By locating the control unit 32 in a chamber 36 separate from the chambers 16, 30, through which (filtered) air from the dust collecting chamber 6 flows, dust is prevented from damaging the control unit 32. The chamber 36 is preferably hermetically closed in respect to the environment. The chamber 36 may also comprise an electronic transformer (for transforming mains power (e.g. 230V or 110V) into a lower voltage (e.g. 12V, 24V, 36V, 48V), a wireless communication device for effecting wireless data communication (e.g. to the external power tool connected to the vacuum cleaner 2 by means of the suction hose), and other electric or electronic components or assemblies.

[0033] According to the present invention, the control unit 32 is adapted to automatically operate only one of the motors 18, 20 upon activation of the vacuum cleaning device 2. After activation of the vacuum cleaner 2, it is in its normal suction mode. The normal suction mode is realized by the operation of only one of the motors 18, 20. In Figure 2 shows a situation after activation of the vacuum cleaner 2, in which motor 18 is operated and motor 20 is turned off. Of course, in another situation motor 20 may be operated after activation of the vacuum cleaner 2 and motor 18 will remain turned off. The active motor 18 may be operated in its ideal point of operation (nominal speed). However, it is also possible that the active motor 18 is operated at its maximum speed or any other speed between above zero and the maximum speed. A controller 38 (see Figure 1) may be provided in order to set the speed of the active motor 18 to a desired value. The controller 38 may also be used to activate and deactivate the vacuum cleaner 2. Alternatively, a separate switch may be provided for activating and deactivating the vacuum cleaner 2.

[0034] The control unit 32 may be associated with a storage unit 40 for storing a value indicative of the operational time of each of the motors 18, 20. The storage unit 40 is adapted to maintain the stored values even when no electric power is applied to the storage unit 40, e.g. when the vacuum cleaner 2 is deactivated. In that case electric power may only be required for storing and reading out the values. The storage unit 40 may be, for example, an EPROM or an EEPROM.

[0035] In the embodiment of Figure 2, the storage unit 40 is an integral part of the control unit 32. Alternatively, it would also be possible that the storage unit 40 is provided separate from the control unit 32 and connected thereto electrically.

[0036] Upon activation of the vacuum cleaner 2, the control unit 32 reads out from the storage unit 40 the values of the motors 18, 20 and compares them with each other. The control unit 32 is adapted to select and operate that motor 18; 20 which has the shortest operational time of all motors 18, 20.

[0037] The control unit 32 may be adapted to monitor the operational time of each of the motors 18, 20 during operation of the vacuum cleaner 2, to calculate updated values for the operational times of the motors 18, 20 and to store the updated values in the storage unit 40. Upon each new activation of the vacuum cleaner 2, the control unit 32 can read out from the storage unit 40 the values indicative of the operational times of the motors 18, 20, which have been stored in the storage unit 40 during or after previous activation(s) of the vacuum cleaner 2. Then the control unit 32 can compare the values with each other and select the motor 18, 20 having the shortest operational time and put the selected motor 18, 20 into operation. The reading-out of the values from the storage unit 40, the comparison of the values, the selection of the motor 18, 20 to be operated and the putting-into-operation of the selected motor 18, 20 is effected almost in real-time. The user of the vacuum cleaner 2 will not recognize a delay between activation of the vacuum cleaner 2 and starting of one of the motors 18, 20. The selection of the motor 18, 20 for operation is effected automatically in the background unnoticeable by the user.

[0038] The updated values indicative of the operational times of the motors 18, 20 may be continuously (or regularly, e.g. every 5 seconds to 30 minutes), stored in the storage unit 40 during operation of the vacuum cleaner 2. It is preferred that the control unit 32 stores the updated values indicative of the operational times of the motors 18, 20 in the storage unit 40 after deactivation of the vacuum cleaner 2. During operation of the motor 18; 20, the current operational time of this activation cycle is recorded and upon deactivation of the vacuum cleaner 2 added to the previously stored value and finally the updated value is stored in the storage unit 40. Of course, in this case, after deactivation of the vacuum cleaner 2 the electric power should continue to be present at (applied to) the control unit 32 and the storage unit 40 until the updated value(s) of the operational time(s) has (have) been stored in the storage unit 40.

[0039] It is suggested that the control unit 32 is adapted to monitor an electric operational value at least of the operating motor 18; 20 during operation of the vacuum cleaner 2 and to deduce from the monitored value whether the operating motor 18; 20 is properly functioning or not. The "operating motor" would be the motor 18; 20 previously selected by the control unit 32 for operation upon activation of the vacuum cleaner 2, even if the motor 18; 20 is actually not running due to a malfunction or defect. For example, the control unit 32 can monitor the electric current drawn by the operating motor 18; 20. If an operating motor 18; 20 or a motor 18; 20 which should be operating is found not to draw the expected amount of electric current or far more electric current than expected, it is considered to have a defect. Monitoring of the electric current may be realized by defining a window for the expected amount of current to be drawn during normal operation of a properly functioning motor 18; 20, e.g. between 5 A and 12 A. The control unit 32 verifies whether the electric current currently drawn by the motor 18; 20 is within the defined window. If not, a malfunction or defect of the motor 18; 20 is diagnosed.

[0040] The control unit 32 may further be adapted to turn off the defect motor 18; 20 and to operate another motor 20; 18 of the vacuum cleaner 2 if the operating motor 18; 20 is found not to operate properly. This significantly improves availability of the vacuum cleaner 2. The vacuum cleaner 2 may be provided with at least one LED or the like on the outside of the housing 8, 56 of the vacuum cleaner 2 for signalling to the user a malfunction and/or a proper functioning of the motors 18, 20. Preferably, a separate LED is provided for each of the motors 18, 20. The LEDs may be multi-colour LEDs signalling a proper functioning of at least one of the motors 18, 20 with a light signal in a first colour (e.g. green) and a malfunction of the motor with a light signal in another colour (e.g. yellow or red). The signalling may also be effected by means of a continuous or flashing light signal or the like.

[0041] During operation of the motor 18 (see Figure 2) upon activation of the vacuum cleaner 2, the operating motor 18 draws air from the dust collecting chamber 6 through the or all filter elements 14, respectively, and through the air outlet 26, 28 of the vacuum cleaner 2, thereby creating the depression in the dust collecting chamber 6. In this embodiment, the motor 18 currently operating uses all available filter elements 14 in the vacuum cleaner 2, thereby filling the filter element(s) 14 equally and uniformly with dust 42.

[0042] As can be seen from Figure 2, the dust collecting chamber 6 has two separate outlet ports 12, each of which assigned to an input side of one of the motors 18, 20. An inlet valve 44 is located in each of the outlet ports 12 of the dust collecting chamber 6. Each inlet valve 44 is open during operation of the motor 18; 20 assigned to the inlet valve 44 and closed during rest of the motor 20; 18 assigned to the inlet valve 44.

[0043] It is suggested that the inlet valves 44 are embodied as non-return valves automatically closing in the direction of arrow 46 due to the depression in the dust collecting chamber 6 when the respective motor 20; 18 is turned off. When a motor 18; 20 is turned on, it draws air from the dust collecting chamber 6 through the or all filter element(s) 14, the respective outlet port 12 assigned to the motor 18; 20 in operation and an air outlet 26, 28 of the vacuum cleaner 2. Due to the air flow 48 the non-return valve assigned to the operating motor 18; 20 is automatically opened. All other inlet valves 44 are closed, thereby closing the outlet ports 12 assigned to the inactive motors 20; 18 and effectively sealing the dust collecting chamber 6, thereby allowing the air flow 48 only through the outlet port 12 assigned to the operating motor 18; 20. This significantly enhances efficiency of the vacuum cleaner 2. Alternatively, the inlet valves 44 may also be embodied as electromagnetically actuated valves which are actively controlled by the control unit 32.

[0044] The control unit 32 may further be adapted to control the speed of the motor 18, 20 turned on upon activation of the vacuum cleaner 2 and to reduce or increase the speed of the motor 18, 20 depending on an external request. Hence, the operating motor 18, 20 does not always have to run at its nominal or maximum speed but can be operated at a reduced speed if desired. This reduces the consumption of electric energy during operation of the vacuum cleaner 2. If the vacuum cleaner 2 has to aspire only a small amount of dust 42 or dust 42 from only one or few external power tools attached thereto by means of a suction hose, the motor speed can be reduced. If the vacuum cleaner 2 has to aspire a larger amount of dust 42 or dust 42 from a plurality of power tools attached thereto, the motor speed can be increased.

[0045] The external request for a reduced or increased speed of the motor 18, 20 operating upon activation of the vacuum cleaner 2 may originate from

• a manually operable controller, like controller 38, connected to the control unit 32 and located at the outside of the vacuum cleaner 2, and/or
• a receiving unit 50 assigned to the vacuum cleaner 2 and adapted to receive an external signal 52 indicative of the amount of dust 40 to be aspired by the vacuum cleaner 2.

[0046] The manually operable controller 38 may be embodied as a rotary control for gradually reducing or increasing the speed of the operating motor 18, 20. Alternatively, the controller 38 may be embodied as one or more switches (not shown) for reducing or increasing the speed of the operating motor 18, 20 to a pre-set value. Preferably, the motor 18, 20 set into operation upon activation of the vacuum cleaner 2 is operated at the speed, corresponding to the current setting of the controller 38, right from the beginning immediately after activation of the vacuum cleaner 2 Alternatively, it is also possible that the motor 18, 20 set into operation upon activation of the vacuum cleaner 2 is initially always operated at a pre-set speed, e.g. at the nominal or maximal speed, independent of the setting of the controller 38 during the previous activation cycle.

[0047] The receiving unit 50 may be adapted to receive the external signal 52 from a remote control or from an external power tool which generates dust during its operation and which is connected to an inlet port 10 of the dust collecting chamber 6 by means of a suction hose. The external signal 52 may be indicative of the amount of dust 42 generated by the tool during its operation. The remote control (not shown) may be part of a smart phone, tablet PC or the like operated by the user of the vacuum cleaner 2. In that case, the remote control may be realized as an application (so-called App) running on the smart phone. The power tool (not shown) may be provided with transmission means for transmitting the external signal 52 to the receiving unit 50. The receiving unit 50 is preferably an integral part of the vacuum cleaner 2. Alternatively, it may be an external receiving unit, electrically connected to the control unit 32. The external signal 52 is preferably transmitted wirelessly from the remote control or the external power tool, respectively, to the receiving unit 50 according to a desired protocol for wireless signal transmission, e.g. regular BlueTooth, BlueTooth LE (low energy), ZigBee, WiFi or the like.

[0048] The control unit 32 may be adapted to select one of the motors 18, 20 for operation also depending on the speed with which the motors 18, 20 where previously operated during previous activation cycles of the vacuum cleaner 2. For example, it is possible that the nominal or the maximum speed of the motors 18, 20 is assigned the factor 1.0, half the nominal or maximum speed may be assigned the factor 0.5. The factor may be calculated based on the average speed of the operating motor 18, 20 during an activation cycle of the vacuum cleaner 2. Before storing the value indicative of the operational time of the operated motor 18, 20 in the storage unit 40, the value may be multiplied with the factor calculated in dependence on the average speed. A weighting factor (between >0 and 1.0) may also be considered when calculating the product. Then, the product of the time-dependent value and the speed-dependent factor (and possibly also the weighting factor) is stored in the storage unit 40. Upon a new activation of the vacuum cleaner 2 the motor 18, 20 is selected and set into operation which has the smallest product assigned thereto.

[0049] The vacuum cleaner 2 may also have a manually operable turbo switch 54 connected to the control unit 32 and located at the outside of the vacuum cleaner 2. The control unit 32 is adapted to operate at least one additional motor 18, 20 upon activation of the turbo switch 54. The turbo switch 54 allows a short-term activation of more than one motor 18, 20, preferably of all motors 18, 20 available in the vacuum cleaner 2. This may temporarily increase the throughput rate of the vacuum cleaner 2, for example in order to aspire larger amounts of dust 42 within a short period of time. It is suggested, that to begin with, each time the vacuum cleaner 2 is activated, the turbo switch 54 is deactivated. Hence, the vacuum cleaner 2 always starts with only one of the motors 18, 20 operating even if during a previous activation cycle of the vacuum cleaner 2 the turbo switch 54 was activated.

[0050] As can be seen from Figure 1, the vacuum cleaner 2 is preferably a mobile vacuum cleaner with wheels 4 attached thereto, in order to freely move the vacuum cleaner 2 to its work place. Alternatively, the vacuum cleaning device could also be located on a trolley with wheels. It is preferred that the vacuum cleaner 2 is attached to an external hand guided power tool (e.g. a drill, a polisher, a sander or a grinder) by means of a suction hose (not shown). The power tool generates dust 42 in a working area during its operation. The suction hose connects a tool internal dust extraction system (active or passive) with an inlet port 10 of the dust collecting chamber 6 of the vacuum cleaner 2. By aspiring the dust 40 from the working area of the power tool, environmental requirements can be fulfilled (only a limited amount of dust in the air is allowed) and the working area can be kept free of dust (a free view of the user on the working area is possible).

[0051] The dust collecting container 8 comprising the dust collecting chamber 6 of the vacuum cleaner 2 has a top cover 56 comprising the motors 18, 20, the blowers 22, 24 and the control unit 32. The top cover 56 constitutes a top part of the vacuum cleaner housing. The top cover 56 preferably comprise all electric and electronic components of the vacuum cleaner 2, which may include switches, like switch 54, controllers, like controller 38, a power cable 58 for connecting the vacuum cleaner 2 to a mains power supply, and a power socket for connecting a power cable of an external power tool, like power sockets 60. Additionally, the at filter element 14 may also be attached to the top cover 56, in particular to the bottom side of the top cover 56, below the outlet ports 12 of the dust collecting chamber 6. The top cover 56 is detachably attached to the container 8 by means of releasable clamping elements 62. When attached to the container 8, the connection between the top cover 56 and the container 8 is preferably airtight in order to maintain the depression in the dust collecting chamber 6 and to allow an airflow into the chamber 6 only through the inlet port 10. Airtightness may be achieved by a gasket 64 provided between the container 8 and the top cover 56.

[0052] It is further suggested that the dust collecting container 8 comprising the dust collecting chamber 6 of the vacuum cleaner 2 has a front opening 65 which may be closed by a removable front cover 66. The front opening 65 permits easy access to the dust collecting chamber 6 without having to open the top cover 56, in order to replace a vacuum cleaner bag possibly located in the dust collecting chamber 6 and/or to replace the filter element 14. The front cover 66 shown in the embodiment of Figure 1 can be unlocked and then pivoted about a rotational axis 68.

[0053] In Figures 2 and 3 an operation mode of the vacuum cleaner 2 is shown in which the first motor 18 is operated upon activation of the vacuum cleaner 2. The inlet valve 44 assigned to that motor 18 is open and gives way to an air flow 48 from the dust collecting chamber 6, through the filter element 14, the outlet port 12 assigned to that motor 18, the blower 22 and an air outlet 26, 28. Figure 4 shows an operation mode of the vacuum cleaner 2 in which the second motor 20 is operated upon activation of the vacuum cleaner 2. The inlet valve 44 assigned to the second motor 20 is closed. The inlet valve 44 assigned to that motor 20 is open and gives way to an air flow 48 from the dust collecting chamber 6, through the filter element 14, the outlet port 12 assigned to that motor 20, the blower 24 and an air outlet 26, 28. The inlet valve 44 assigned to the first motor 18 is closed. Finally, Figure 5 shows the turbo-mode in which both motors 18, 20 are temporarily operated. Both inlet valves 44 are open and allow an airflow 48 from the dust collecting chamber 6, through the filter element 14, both outlet ports 12, both blowers 22, 24 and an air outlet 26, 28.

[0054] The vacuum cleaner 2 shown in Figure 1 comprises additional accessories transforming it into a so-called mobile vacuum workstation similar to the one described in co-pending EP application 19 156 138.0. The workstation may comprise

• lateral supporting feet 70 which may be pivoted from their rest position shown in Figure 1 into an active position in which the stick out radially from the vacuum cleaner 2,
• a height-adjustable handle 72 for comfortably moving the workstation to its work place,
• a rear container 74 attached to the handle 72, for receiving accessories of the vacuum cleaner 2 or of the external power tool connected to the vacuum cleaner 2 by means of a suction hose,
• a front tray 76 attached to the handle 72, for receiving accessories of the vacuum cleaner 2 or of the external power tool,
• a support bracket 78 with fastening means 80 for attaching and supporting the suction hose with which the external power tool is connected to the vacuum cleaner 2,
• a mounting panel 82 releasably attached to the handle 72 in its rest position and located in a position 84 on a top surface 86 of the top cover 56 in its active position,
• two receptacles 88 for receiving accessories of the vacuum cleaner 2 or of the external power tool connected to the vacuum cleaner 2, each receptacle 88 being pivotable about a horizontal rotational axis 90,
• a removable lid 94 for closing the receptacles 88 in order to avoid the accessories from falling out of the receptacles 88 when they are pivoted upwards about the axis 90, and
• a tool holder 92 attached to the handle 72 for receiving and holding an external power tool connected to the vacuum cleaner 2.

Claims

1. Vacuum cleaning device (2) comprising:

- a dust collecting chamber (6) with at least one inlet port (10) for dust-laden air (9) and at least one outlet port (12),

- at least one filter element (14) located between the at least one outlet port (12) and the rest of the dust collecting chamber (6),

- at least two motors (18, 20) each driving an air blower (22, 24) for drawing air from the dust collecting chamber (6) through an air outlet (26, 28) of the vacuum cleaning device (2), thereby creating a depression in the dust collecting chamber (6), and

- a control unit (32) for controlling the operation of the at least two motors (18, 20), characterized in that
the control unit (32) is adapted to automatically operate only one of the motors (18, 20) upon activation of the vacuum cleaning device (2).

2. Vacuum cleaning device (2) according to claim 1, wherein
the control unit (32) is associated with a storage unit (40) for storing a value indicative of the operational time of each of the motors (18, 20), and wherein the control unit (32) is adapted to select and operate the motor (18; 20) having the shortest operational time of all motors (18, 20), upon activation of the vacuum cleaning device (2).

3. Vacuum cleaning device (2) according to claim 2, wherein
the control unit (32) is adapted to monitor the operational time of each of the motors (18, 20) during operation of the vacuum cleaning device (2) and to store updated values for the operational times of the motors (18, 20) in the storage unit (40).

4. Vacuum cleaning device (2) according to claim 3, wherein
the control unit (32) is adapted to store the updated values for the operational times of the motors (18, 20) in the storage unit (40) after deactivation of the vacuum cleaning device (2).

5. Vacuum cleaning device (2) according to one of the preceding claims, wherein
the control unit (32) is adapted to monitor an electric operational value of at least the motor (18; 20) operating upon activation of the vacuum cleaning device (2) and to deduce from the monitored value a defect or a proper functioning of the operating motor (18; 20).

6. Vacuum cleaning device (2) according to claim 5, wherein
the control unit (32) is adapted to turn off the defect motor (18; 20) and to operate another motor (20; 18) of the vacuum cleaning device (2) if the operating motor (18; 20) is found to have a defect.

7. Vacuum cleaning device (2) according to one of the preceding claims, wherein
the vacuum cleaning device (2) is designed such that during operation of only one of the motors (18, 20) upon activation of the vacuum cleaning device (2), the operating motor (18; 20) draws air from the dust collecting chamber (6) through all of the at least one filter element (14) and through the air outlet (26, 28) of the vacuum cleaning device (2), thereby creating the depression in the dust collecting chamber (6).

8. Vacuum cleaning device (2) according to one of the preceding claims, wherein
the dust collecting chamber (6) has a separate outlet port (12) assigned to an input side of each of the motors (18, 20) and that an inlet valve (44) is located in each of the outlet ports (12), the inlet valve (44) being open during operation of the respective motor (18, 20) and closed during rest of the respective motor (18, 20).

9. Vacuum cleaning device (2) according to claim 8, wherein
the inlet valves (44) are embodied as non-return valves automatically closing due to the depression in the dust collecting chamber (6) when the respective motor (18, 20) is turned off.

10. Vacuum cleaning device (2) according to one of the preceding claims, wherein
the control unit (32) is adapted to control the speed of the motor (18, 20) operating upon activation of the vacuum cleaning device (2) and to reduce or increase the speed of the motor (18, 20) depending on an external request.

11. Vacuum cleaning device (2) according to claim 10, wherein
the external request for a reduced or increased speed of the motor (18, 20) operating upon activation of the vacuum cleaning device (2) originates from

- a manually operable controller (38) connected to the control unit (32) and located at the outside of the vacuum cleaning device (2), and/or

- a receiving unit (50) assigned to the vacuum cleaning device (2) and adapted to receive an external signal (52) indicative of the amount of dust (40) to be aspired by the vacuum cleaning device (2).

12. Vacuum cleaning device (2) according to claim 11, wherein
the receiving unit (50) is adapted to receive an external signal (52) from a remote control or from an external power tool which generates dust during its operation and which is connected to an inlet port (10) of the dust collecting chamber (6) by means of a suction hose, the signal (52) indicative of the amount of dust (40) generated by the power tool during its operation.

13. Vacuum cleaning device (2) according to one of the claims 10 to 12, wherein
the control unit (32) is adapted to select one of the motors (18, 20) for operation also depending on the speed with which the motors (18, 20) where previously operated.

14. Vacuum cleaning device (2) according to one of the preceding claims, wherein
the vacuum cleaning device (2) has a manually operable turbo switch (54) connected to the control unit (32) and located at the outside of the vacuum cleaning device (2), and wherein the control unit (32) is adapted to operate at least one additional motor (18, 20) upon activation of the turbo switch (54).

15. Vacuum cleaning device (2) according to one of the preceding claims, wherein
the vacuum cleaning device (2) is a mobile vacuum cleaner with wheels (4) attached thereto or located on a trolley with wheels, in order to freely move the vacuum cleaning device (2) to its work place.

Drawing