BLOWER FILTER DEVICE FOR POTENTIALLY EXPLOSIVE AREAS AND PROCESS FOR OPERATING A BLOWER FILTER DEVICE

Abstract

A blower filter device (3) is connectable to a voltage supply unit (2) and includes a blower unit (5), a filter mount (14), an internal energy storage unit (7), an energy interface (9), a current limitation device (13), a sensor array (16, 17, 18) and a control device (6). The current limitation device is activated upon disconnecting the energy interface from the voltage supply unit. The activated current limitation device limits the intensity of a current from the energy interface to the internal energy storage device. Upon the voltage supply unit being connected to the energy storage device and a predefined deactivating event is detected, the control device deactivates the current limitation device. The deactivating event is based on a charging voltage of the internal energy storage unit and/or on a time period that has elapsed since the connection. A process is provided for operating such a blower filter device.

Claims

1. A blower filter device comprising: a blower unit for generating an air stream; a filter mount for accommodating a filter unit; an internal energy storage unit; an energy interface, wherein the internal energy storage unit is connected electrically to both the blower unit and the energy interface and is chargeable with electrical energy and is configured to release electrical energy, and wherein the energy interface is configured to be electrically connectable to a voltage supply unit and to be electrically disconnectable from same; an activatable and deactivatable current limitation device; a sensor array; and a control device, wherein the blower filter device is configured such that the current limitation device is activated when the energy interface is disconnected from the voltage supply unit, wherein the activated current limitation device is configured to maintain the intensity of a current from the energy interface to the internal energy storage unit below a predefined current intensity limit, wherein the sensor array is configured to detect a predefined deactivating event, wherein the deactivating event has occurred: if the state of charge of the internal energy storage unit has exceeded a predefined state of change limit and/or if a predefined time period has elapsed since the establishment of an electrical connection between the energy interface and the voltage supply unit, and wherein the control device is configured to deactivate the current limitation device after the detection of the deactivating event such that the internal energy storage unit is connected electrically to the energy interface after the deactivation without limitation to the current intensity limit.

2. A blower filter device in accordance with claim 1, wherein the sensor array comprises a voltage sensor configured to measure a variable, which is correlated with an electrical output voltage or a charging voltage of the internal energy storage unit.

3. A blower filter device in accordance with claim 1, wherein the sensor array comprises: a connection sensor; and a time period sensor, wherein the connection sensor is configured to detect that the voltage supply unit is connected electrically to the energy interface, and wherein the time period sensor is configured: to measure a time that has elapsed since establishing an electrical connection between the energy interface and the voltage supply unit, and to compare the elapsed time with a predefined threshold value.

4. A blower filter device in accordance with claim 1, wherein the current limitation device comprises: a current limitation unit; and a switchable electrical connection unit, wherein the connection unit is arranged in parallel to the current limitation unit, and wherein the switchable electrical connection unit connects the energy interface electrically to the internal energy storage unit in a conduction state and interrupts this connection in a blocked state and wherein the control device is configured to switch the electrical connection unit from the blocked state into the conduction state after the detection of the deactivating event.

5. A blower filter device in accordance with claim 4, wherein the switchable electrical connection unit has a bidirectional thyristor diode and/or a bidirectional diode and/or a transistor and/or a relay and/or a mechanical contact and/or a spark gap.

6. A blower filter device in accordance with claim 1, wherein the current limitation device has at least one electronic component with a variable electrical resistance value, and wherein the control device is configured to reduce the electrical resistance value of this component after the detection of the deactivating event.

7. A blower filter device in accordance with claim 6, wherein the electronic component comprises at least one transistor and/or a potentiometer.

8. A blower filter device in accordance with claim 7, wherein the control device is configured to reduce the electrical resistance value as a function of the state of charge of the internal energy storage unit.

9. A blower filter device in accordance with claim 7, wherein the electronic component comprises at least one transistor, which can be biased into conduction optionally partially or fully, and wherein the electrical resistance value of the transistor biased partially into conduction is higher than that of the transistor biased fully into conduction.

10. A blower filter device in accordance with claim 1, wherein the control device is configured to automatically activate the current limitation device in response to a disconnection of the energy interface from the voltage supply unit.

11. A blower filter device in accordance with claim 1, wherein the blower unit can be switched on and can be switched off, and the blower filter device is configured to automatically activate the current limitation device in response to the switching on and/or switching off of the blower unit.

12. A blower filter device in accordance with claim 11, wherein the blower filter device comprises an actuating element for switching on and switching off the blower unit, and wherein the actuating element is connected to an electrical connection between the current limitation device and the energy interface such that an actuation of the actuating element for switching on the blower unit connects the current limitation device electrically to the energy interface and an actuation of the actuating element for switching off the blower unit disconnects the current limitation device electrically from the energy interface.

13. A blower filter device in accordance with claim 1, wherein the blower filter device comprises a storage unit for accommodating a mobile voltage supply unit, especially a battery pack, and wherein the storage unit is configured such that a mobile voltage supply unit accommodated by the storage unit is connected electrically detachably to the energy interface.

14. A blower filter system comprising: a voltage supply unit; and a blower filter device comprising: a blower unit for generating an air stream; a filter mount for accommodating a filter unit; an internal energy storage unit; an energy interface, wherein the internal energy storage unit is connected electrically to both the blower unit and the energy interface and is chargeable with electrical energy and is configured to release electrical energy, and wherein the energy interface is configured to be electrically connectable to the voltage supply unit and to be electrically disconnectable from same; an activatable and deactivatable current limitation device; a sensor array; and a control device, wherein the blower filter device is configured such that the current limitation device is activated when the energy interface is disconnected from the voltage supply unit, wherein the activated current limitation device is configured to maintain the intensity of a current from the energy interface to the internal energy storage unit below a predefined current intensity limit, wherein the sensor array is configured to detect a predefined deactivating event, wherein the deactivating event has occurred: if the state of charge of the internal energy storage unit has exceeded a predefined state of change limit; and/or if a predefined time period has elapsed since the establishment of an electrical connection between the energy interface and the voltage supply unit; and wherein the control device is configured to deactivate the current limitation device after the detection of the deactivating event such that the internal energy storage unit is connected electrically to the energy interface after the deactivation without limitation to the current intensity limit.

15. A breathing air supply system comprising: a blower filter device comprising: a blower unit for generating an air stream; a filter mount for accommodating a filter unit; an internal energy storage unit; an energy interface, wherein the internal energy storage unit is connected electrically to both the blower unit and the energy interface and is chargeable with electrical energy and is configured to release electrical energy, and wherein the energy interface is configured to be electrically connectable to a voltage supply unit and to be electrically disconnectable from same; an activatable and deactivatable current limitation device; a sensor array; and a control device, wherein the blower filter device is configured such that the current limitation device is activated when the energy interface is disconnected from the voltage supply unit, wherein the activated current limitation device is configured to maintain the intensity of a current from the energy interface to the internal energy storage unit below a predefined current intensity limit, wherein the sensor array is configured to detect a predefined deactivating event, wherein the deactivating event has occurred: if the state of charge of the internal energy storage unit has exceeded a predefined state of change limit; and/or if a predefined time period has elapsed since the establishment of an electrical connection between the energy interface and the voltage supply unit; and wherein the control device is configured to deactivate the current limitation device after the detection of the deactivating event such that the internal energy storage unit is connected electrically to the energy interface after the deactivation without limitation to the current intensity limit; a face masks; and a connection unit, which establishes a fluid connection between the blower filter device and the face mask at least from time to time.

16. A process for operating a blower filter device, wherein the blower filter device comprises a blower unit for generating an air stream, a filter mount for accommodating a filter unit, an internal energy storage unit and an energy interface, wherein the internal energy storage unit is connected electrically to the energy interface the process comprising the steps of: electrically connecting the energy interface to a voltage supply unit at least once; providing the blower filter device so that the blower filter device further comprises a current limitation device, a control device and a sensor array; activating the current limitation device before the step of electrically connecting; wherein the following steps are carried out after the connection: maintaining, with the activated current limitation device, an intensity of a current from the energy interface to the internal energy storage unit below a predefined current intensity limit, detecting, with the sensor array, a predefined deactivating event, wherein the deactivating event will have occurred when the state of charge of the internal energy storage unit has exceeded a predefined state of charge limit and/or when a predefined time period has elapsed since the establishment of an electrical connection between the energy interface and the voltage supply unit; and deactivating, with the control device the current limitation device after the detection of the deactivating event such that the intensity of a current from the energy interface to the internal energy storage unit is not limited to the current intensity threshold after the detection of the deactivating event.

17. A process in accordance with claim 16, wherein the blower filter device comprises a storage unit for accommodating a mobile voltage supply unit, especially a battery pack, and the step of connecting the energy interface electrically to the voltage supply unit is carried out with a mobile voltage supply unit and it comprises the step of inserting the mobile voltage supply unit into the storage unit such that the mobile voltage supply unit is electrically connected to the energy interface after the insertion.

18. A process in accordance with claim 16, wherein at least one of the steps of connecting the energy interface to the voltage supply unit or disconnecting the energy interface from the voltage supply unit is detected automatically and it triggers the step of the control device automatically activating the current limitation device.

19. A process in accordance with claim 16, wherein the blower unit can be switched on and switched off again, wherein the current limitation device is activated with the blower unit switched off, wherein the step of switching off the blower unit triggers the step in which the control device activates the current limitation device, and wherein the step of switching on the blower unit triggers the step in which the control device deactivates the current limitation device after the detection of the deactivating event.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0074] In the drawings:

[0075] FIG. 1 is a schematic view showing the configuration of an embodiment of a blower filter device according to the present invention;

[0076] FIG. 2 is a circuit view showing an exemplary embodiment of a circuitry for current limitation;

[0077] FIG. 3 is a flow chart showing steps of an exemplary process, which is carried out during the operation of the blower filter device;

[0078] FIG. 4 is a flow chart showing a first possible embodiment of when the deactivating event is detected; and

[0079] FIG. 5 is a flow chart showing a possible alternative embodiment of when the deactivating event is detected.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0080] Referring to the drawings, FIG. 1 shows by way of an example how a blower filter device 3 according to the present invention may be configured. The following components are arranged in a housing 4: [0081] a blower unit 5, which comprises a fan impeller, an electric motor and a DC/AC converter, not shown, for the electric motor, [0082] an actuating element 19, with which a user can switch the blower unit 5 on and off, [0083] a filter mount 14, which is capable of accommodating a filter cartridge 15; [0084] an internal energy storage unit 7, which comprises two capacitors in the exemplary embodiment, [0085] a storage unit 8, which is capable of accommodating a mobile voltage supply unit in the form of a battery pack 2, [0086] an energy interface 9 with two electrical contact points 9.1, 9.2, [0087] a voltage sensor 16, which is capable of measuring the current charging voltage of the internal energy storage unit 7, [0088] a connection sensor 17, which is capable of determining whether a battery pack 2 is inserted into the storage unit 8 or not and which is likewise configured in the exemplary embodiment as a voltage sensor, [0089] a time period sensor in the form of a system clock 18, which is capable of measuring the time period that has elapsed since an event, e.g., since the insertion of a battery pack 2 into the storage unit 8, [0090] a current limitation device (circuit) 13, which will be described below, and [0091] a control device 6, which receives signals from the voltage sensor 16, from the connection sensor 17 and from a sensor, not shown, for determining whether the blower unit 5 is switched on or is switched off, and is capable of actuating the current limitation device 13.

[0092] The blower unit 5 is capable of drawing in air from the environment by means of the fan impeller and of generating an air stream thereby. This air stream flows through the inserted filter cartridge 15 and is purified in the process. The purified air stream is available for a user, not shown, of the blower filter device 3. The air stream is preferably sent through a breathing air tube to a face mask. The user can switch on the blower unit 5 and switch it off again, doing so by means of the actuating element 19.

[0093] The battery pack 2 comprises two electrical contact points (terminals) 10.1 and 10.2. The battery pack 2 is shown in FIG. 1 once outside the storage unit 8 with solid lines and once with broken lines in a position in which the battery pack 2 is inserted into the storage unit 8. In this inserted position, the contact points 10.1 and 10.2 of the battery pack 2 contact the corresponding contact points 9.1 and 9.2 of the energy interface 9. The filter cartridge 15 is shown once with solid lines in a position outside the filter mount 14 and once with broken lines in a position in which the filter cartridge 15 is inserted into the filter mount 14.

[0094] The blower unit 5 is preferably not supplied directly from the battery pack 2. The battery pack 2 rather charges the internal energy storage unit 7 via the energy interface 9, and the internal energy storage unit 7 supplies the blower unit 5.

[0095] A blower filter system 1 can be worn by a user, e.g., on a belt or as a backpack, and it comprises [0096] the blower filter device 3, [0097] the battery pack 2 in the storage unit 8 and [0098] the filter cartridge 15 in the filter mount 14.

[0099] The current limitation device 13 is permanently connected electrically to the internal energy storage unit 7. The current limitation device 13 can be actuated by the control device 6 and be brought optionally into an activated state and into a deactivated state. The current limitation device 13 limits in the activated state the current intensity from the energy interface 9 to the internal energy storage unit 7 to a predefined current intensity limit. When the current limitation device 13 is deactivated, the current intensity may be above this current intensity limit.

[0100] The internal energy storage unit 7 is connected electrically permanently to the blower unit 5. If the battery pack 2 is inserted into the storage unit 8 and the contact points 10.1 and 10.2 contact the corresponding contact points 9.1 and 9.2, the battery pack 2 is connected electrically to the internal energy storage unit 7 via the circuit 13. The battery pack electrically charges the internal energy storage unit 7.

[0101] The internal energy storage unit 7 is capable of supplying the blower unit 5 with electricity for a certain time period even if the battery pack 2 has been depleted or is not inserted into the storage unit 8. It is possible hereby to replace the battery pack 2 with the blower unit 5 operating, even during the ongoing operation. It is not necessary to leave a hazardous environment for the replacement.

[0102] In the exemplary embodiment, the connection sensor 17 is capable of measuring the voltage between the two contact points 9.1 and 9.2. The control device 6 is capable of analyzing the signals and of automatically distinguishing between the following three situations: [0103] No battery pack 2 has been inserted into the storage unit 8. [0104] The battery pack 2 inserted into the storage unit 8 is discharged and must be replaced. [0105] The battery pack 2 inserted into the storage unit 8 supplies sufficient voltage.

[0106] FIG. 2 shows as an example the current limitation device 13. This circuit 13 comprises a current limitation unit 11 and a switchable electrical connection unit 12, which is arranged in parallel to the current limitation unit 11. The connection unit 12 can be actuated and be brought optionally into a conduction state or into a blocked state. The current limitation unit 11 comprises in the exemplary embodiment an actuatable potentiometer, i.e., it has a variable electrical resistance value. The lowest possible electrical resistance value of the current imitation unit 11 is higher than the electrical resistance value of the switchable electrical connection unit 12 in the conduction state. In the blocked state, the electrical resistance value of the connection unit 12 is several times higher than the resistance value or than the maximum resistance value of the current limitation unit 11, for example, it is practically infinite. The control device 6 is capable of actuating both the current limitation unit 11 and the connection unit 12. If the connection unit 12 is in the blocked state, the current intensity, which flows through the current limitation device 3, is limited to a predefined current intensity limit. It is also possible that the current limitation unit 11 has a fixed resistance value and cannot be actuated.

[0107] It is also possible that the current limitation unit 11 is not bypassed by a switchable electrical connection unit 12. The current limitation device 13 is preferably deactivated in this embodiment by its electrical resistance value being reduced.

[0108] FIG. 3 shows as an example a flow chart of how the blower filter device 3 is operated. The blower filter device 3 is in the following state prior to the use: [0109] The energy interface 9 is not connected to a battery pack 2 (state 2:Z1). [0110] The current limitation device 13 is in the activated state (state 13:Z1). [0111] The blower unit 5 is switched off (state 5:Z1).

[0112] The following steps are then carried out: [0113] The user inserts the battery pack 2 into the storage unit 8 (step S1). An electrically connection is established thereby between the battery pack 2 and the energy interface 9. The battery pack 2 is connected thereby electrically to the internal energy storage unit and charges same. [0114] The connection sensor 17 sends a signal indicating that the battery pack 2 is electrically connected to the energy interface 9 (event 17:E1). [0115] The control device 6 checks whether the first deactivating event has occurred (checking dE1?). [0116] As soon as this has happened (branch Yes), the control device 6 deactivates the current limitation device 13 (step S2). The current limitation device 13 is in the deactivated state (13:Z2) now. [0117] The user actuates the actuating element 19 for the blower unit 5 and switches the blower unit 5 on thereby (step S3). The blower unit 5 is in the switched-on state now (state 5:Z2). [0118] A sensor, not shown, detects the actuation of the actuating element 19 or it detects in another manner that the blower unit 5 is switched on now (event E3). [0119] As a response to the switching on of the blower unit 5, the control device 6 activates the current limitation device 13 (step S4). The current limitation device 13 is again in the activated state now (state 13:Z1). [0120] The control device 6 checks whether the second deactivating event has occurred (checking dE2?). The second deactivating event may be set in exactly the same manner as the first deactivating event or it may be different from it. [0121] As soon as the second deactivating event is detected (branch Yes), the control device 6 deactivates the current limitation device 13 again (step S2). The current limitation device 13 is in the deactivated state now (state 13:Z2). Current can flow from the battery pack 2 via the energy interface 9 to the internal energy storage unit 7 and farther to the switched-on blower unit 5 without the current limitation device 13 limiting the current intensity. [0122] The connection sensor 17 detects after some time that the battery pack 2 has been depleted and must be replaced (step 17:E3). [0123] The user removes the battery pack 2 from the storage unit 8. The electrical connection is interrupted thereby between the battery pack 2 and the energy interface 9 (step S5). The blower unit 5 remains switched on. [0124] The connection sensor 17 detects that no battery back 2 is present any more in the storage unit 8 (step 17:E2).

[0125] The control device 6 activates in response to this the current limitation device 13 (step S4). [0126] The current limitation device 13 is in the activated state again (state 13:Z1). [0127] The user inserts a new battery back 2 (step S1). [0128] The connection sensor 17 sends a signal that the battery pack 2 is electrically connected to the energy interface 9 (event 17:E1). The state 2:Z2 is detected. [0129] The control device 6 checks whether the first deactivating event has occurred (checking dE1?). [0130] As soon as this has happened (branch Yes), the control device 6 deactivates the current limitation device 13 (step S2). The current limitation device 13 is in the deactivated state now (state 13:Z2).

[0131] FIG. 4 shows a possible embodiment of how the first deactivating event is detected (checking dE1? in FIG. 3). [0132] The connection sensor 17 detects that a battery pack 2 is inserted into the storage unit 8 (event 17:E1). [0133] The time period sensor 18 checks whether the predefined time period T has elapsed since the insertion of the battery pack 2 into the storage unit 8. This time period T is preferably shorter than 1 sec, especially preferably shorter than half a second. [0134] As soon as this has happened, the voltage sensor 16 checks whether the charging voltage U of the internal energy storage unit 7 is above a predefined charging voltage limit U0. [0135] As soon as this has happened, the result Erg shows that the deactivating event has occurred.

[0136] Both events must have consequently occurred, namely, the predefined time period T must have elapsed since the connection and the charging voltage U must be above the predefined charging voltage limit U0 in this embodiment. The checking may, of course, also be carried out in the reverse order or simultaneously.

[0137] FIG. 5 shows an alternative embodiment of how the first deactivating event is detected. The two checks are carried out simultaneously in this alternative embodiment. The deactivating event has occurred as soon as the time limit T has elapsed or the charging voltage U is above the charging voltage limit U0. Consequently, if the charging voltage U is above the charging voltage limit U0 already before the end of the time period T, the control device 6 deactivates the current limitation device 13 already before the end of this time period.

[0138] It is possible that the user switches the blower unit 5 off (state 5:Z1), for example, during a pause. This triggers the following procedure: [0139] The sensor, not shown, detects the actuation of the actuating element 19 and that the blower unit 5 has now been switched off. [0140] In response to this, the control device 6 activates the current limitation device 13, so that this is in the activated state (state 13:Z1). [0141] The current limitation device 13 remains in the activated state. [0142] As soon as the sensor detects that the actuating element 19 was again actuated and the blower unit 5 is switched on, the control device 6 checks whether the second deactivating event has occurred (checking dE2?). [0143] As soon as this has happened, the control device 6 deactivates the current limitation device 13 again. Current can flow now without limitation to the blower unit 5.

[0144] In the embodiment just described, the control device 6 activates the current limitation device 13 in response to the fact that a user has actuated the actuating element 19 for the blower unit 5. In an embodiment different from this, the control device 6 is not used to activate the current limitation device 13 after the blower unit 5 has been switched on, but to deactivate it again after the detection of the deactivating event. The actuating element 19 is connected mechanically to a switch, for example, to a pin, in this different embodiment. This switch optionally connects the current limitation device 13 to the energy interface 9 or disconnects these from one another. As long as the blower unit 5 is switched off, the current limitation device 13 and hence also the internal energy storage unit 7 are disconnected electrically from the energy interface 9. As soon as the user switches the blower unit 5 on by means of the actuating element 19, the switch establishes the electrical connection between the energy interface 9 and the current limitation device 13. The internal energy storage unit 7 is charged, and the current limitation device 13 limits the current intensity.

[0145] Just like in the preceding embodiment, the control device 6 preferably activates the current limitation device 13 as soon as the second deactivating event is detected. As soon as the user switches the blower unit 5 off again by means of the actuating element 19, the control device 6 activates the current limitation device 13, for example, by the control device 6 interrupting the electrical bypass. In addition, the current limitation device 13 is disconnected electrically from the energy interface 9 because the switch for the corresponding electrical connection is moved. It is sufficient that the actuating element 19 is connected to this one switch for the electrical connection between the energy interface 9 and the current limitation device 13.

[0146] While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

LIST OF REFERENCE CHARACTERS

[0147] 1 Blower filter system, comprises the blower filter device 3, the battery pack 2 in the storage unit 8 and the filter cartridge 15 in the filter mount 14 [0148] 2 Mobile voltage supply unit in the form of a battery pack, can be pushed into the storage unit 8 [0149] 3 Blower filter device [0150] 4 Housing of the blower filter device 3 [0151] 5 Blower unit, comprises a fan impeller, a motor and a converter [0152] 6 Control device; receives measured values from the sensor array 16, 17, 18, detects the first and second deactivating events and deactivates the current limitation device 11 [0153] 7 Internal energy storage unit, comprises two capacitors in the exemplary embodiment [0154] 8 Storage unit for accommodating the battery pack 2 [0155] 9 Energy interface, connected electrically permanently to the internal energy storage unit 7, comprises the contact points 9.1, 9.2 [0156] 9.1, 9.2 Contact points of the energy interface 9 [0157] 10.1, 10.2 Contact points (terminals) of the battery pack 2 [0158] 11 Current limitation device [0159] 12 Switchable electrical connection unit [0160] 13 Current limitation device, comprises the current limitation device 11 and the connection unit 12 [0161] 14 Filter mount, accommodates the filter cartridge 15 [0162] 15 Filter cartridge, accommodated in the filter mount 14 [0163] 16 Voltage sensor for the charging voltage of the internal energy storage unit 7 [0164] 17 Connection sensor, sends a signal, which indicates whether a battery pack 2 is connected electrically to the energy interface 9 or not [0165] 18 System clock in the control device 6; measures the time period that has elapsed since the insertion of a battery pack 2 into the storage unit 8 [0166] 19 Actuating element for the blower unit 5 [0167] 2:Z1 State: Battery pack 2 disconnected from the energy interface 9 [0168] 2:Z2 State: Battery pack 2 connected to the energy interface 9 [0169] 5:Z1 State: Blower unit 5 switched off [0170] 5:Z2 State: Blower unit 5 switched on [0171] 13:Z1 State: Current limitation device 13 in the activated state [0172] 17:E1 Event: Connection sensor 17 sends signal: Battery pack 2 electrically connected to the energy interface 9 [0173] 17: E2 Event: Connection sensor 17 sends signal: Battery pack 2 electrically disconnected from the energy interface 9 [0174] 17:E3 Step: Connection sensor 17 generates the signal that the battery pack 2 does not supply sufficient current any more (voltage too low) [0175] dE1? Checking: Has the first deactivating event occurred? [0176] dE2? Checking: Has the second deactivating event occurred? [0177] E3 Event: Actuation of the actuating element 19 has been determined [0178] Erg Result: Deactivating event detected [0179] S1 Step: Insert battery pack 2 into storage unit 8, establish electrical connection to the energy interface 9 [0180] S2 Step: Deactivate current limitation device 13 [0181] S3 Step: Switch actuating element 19 for the blower unit 5 on [0182] S4 Step: Activate current limitation device 13 [0183] S5 Step: Remove battery pack 2 from storage unit 8, interrupt electrical connection to the energy interface 9 [0184] T>T? Checking: Has the predefined time period T elapsed since the connection? [0185] U>U0? Checking: Is the charging voltage U of the internal energy storage unit 7 above the predefined charging voltage limit U0?