IMPROVED AIR TREATMENT SYSTEM AND FAN UNIT

Description

Field of technology:

[0001] The invention relates to an air treatment system for a vehicle, comprising at least one fan unit having, at least as its components, at least one fan motor, at least one fan wheel driven by a fan motor, and at least one fan housing, wherein at least one surface area of ​​the system is intended to form an outer surface area of ​​the vehicle. The air treatment can be the heating of air, the cooling of air, or merely the conveying of air. In particular, such systems are used as ventilation, air conditioning, and / or heating systems for positioning on or partially integrated into a vehicle roof of a ground-based vehicle, such as a bus or rail vehicle. However, use as a cooling system in a ground-based refrigerated vehicle, such as a refrigerated truck, is also widespread. The invention further relates to a fan unit for such an air treatment system for a vehicle. State of the art:

[0002] A variety of systems for air treatment for a vehicle are known, comprising at least one fan unit with at least one fan motor, at least one fan wheel driven by a fan motor, and at least one fan housing as its components, wherein at least one surface area of ​​the system is intended to form an outer surface area of ​​the vehicle. For example, DE102006055411A1 discloses such a system as a ventilation, air conditioning, and / or heating system for vehicles. There, the fan unit forms one or more fan modules joined together, each with a fan motor, a fan wheel designed as a rotor, and a fan module housing. The fan module housing there has a conductor track with control and power lines, with line connectors to possibly directly adjacent fan modules. The control and power lines serve to supply power to and control the at least one fan motor.However, the vehicle air treatment systems disclosed in DE102006055411A1 and previously known systems have the problem that in winter, at ambient temperatures below 0°C, there is a risk of the fan wheel freezing and / or blocking the fan housing due to ice or snow. In particular, the outer ends of the fan wheel's rotor blades can freeze to the wall ring around the fan wheel. If the fan wheel is frozen and / or blocked by ice or snow, the fan and thus the desired air treatment fails. This can even lead to damage to the fan motor. In persistent cold weather, rectifying such a failure in previous vehicle air treatment systems, and in particular in the fan unit of previous systems, is normally only possible with the use of suitable external equipment.

[0003] The air treatment system disclosed in CH94630A has electrically operated heaters with heating coils arranged around the blade ring of the fan as a guide vane ring. DE102012108449A1 shows a wall ring of a fan unit with a fan wheel, with an electrically operated heating element positioned on the inside of the wall ring. The fan unit disclosed in CN105737475B has an electrically operated heating device whose heating elements, designed as heating wires, are arranged on the surface of the rotor blades of the fan wheel.

[0004] Document EP1363383 A2 discloses an axial fan with a heating grid downstream of the fan wheel.

[0005] The invention defined in claim 1 is therefore based on the problem that the winter suitability of existing systems for air treatment for vehicles is inadequate or in need of improvement with regard to the fan unit.

[0006] A corresponding problem is underlying a fan unit of an air treatment system according to the invention. Summary of the invention:

[0007] The problem underlying the invention specified in claim 1 is solved by the features listed in claim 1. The problem is solved in that the air treatment system for a vehicle comprises at least one fan unit with at least one fan motor, at least one fan wheel driven by a fan motor and at least one fan housing as its components, wherein at least one surface region of the system is provided to form an outer surface region of the vehicle, and wherein the at least one fan unit has at least one electrically operated heating device designed such that at least one heating element of the electrically operated heating device is arranged in a respective finger guard arranged above the respective fan wheel or is arranged on the surface of the respective finger guard. A fan wheel has rotor blades.In particular, the fan impeller of an axial fan usually has wing-like rotor blades. A fan impeller of the fan unit can be driven to rotate by its associated fan motor. One component of the fan unit is a finger guard above the fan impeller. Because at least one finger guard of the fan unit comprises at least one heating element of at least one electrically operated heating device, the fan unit can be heated, so that at outside temperatures below 0 °C the risk of the fan impeller freezing to the fan housing, in particular to the wall ring, or blocking can be counteracted. If the fan impeller is frozen solid and / or blocked by ice or snow, the fan impeller can be quickly and easily started to rotate freely again by switching on the electrically operated heating device. The use of external equipment to free the fan impeller is therefore unnecessary.

[0008] Due to the arrangement of the heating device in the finger guard located above the respective fan wheel, it can be used particularly effectively to prevent the fan wheel from freezing to the fan housing, especially to the wall ring.

[0009] Advantageous embodiments, further developments and improvements of the respective subject matter of the invention are specified in the subclaims.

[0010] Preferably, at least one heating element of at least one of the at least one electrically operable heating device is arranged in the rotor blades of the fan wheel of the fan unit and / or in a respective wall ring arranged around the respective fan wheel.

[0011] According to an advantageous embodiment, the air treatment system is designed as a ventilation, air conditioning, and / or heating system for positioning on or partially integrated into the roof of a ground-based vehicle. Especially with the fan unit mounted on top of such systems, the influence of weather conditions, such as snow and ice, is particularly high, so the invention is particularly advantageous in preventing a fan wheel from freezing to the fan housing and / or blocking the fan wheel due to ice or snow.

[0012] According to a further advantageous embodiment, the air treatment system is designed as a cooling system for a ground-based refrigerated vehicle. Refrigerated vehicles are also used in winter, and the cooling system, with its fan unit, is directly exposed to external weather influences, making the invention well-suited for this purpose.

[0013] The air treatment system preferably includes a control system configured to regulate the heating output of the at least one electrically operated heating device. This allows the heating output to be automatically adjusted as needed, adapted to the external weather conditions, to ensure free running of the fan impeller. This saves electrical energy.

[0014] A particularly advantageous embodiment of the air treatment system is one in which the at least one electrically operable heating device is designed such that it can be operated with low-voltage current with a voltage of no more than 48 volts. Thus, the heating device can be operated with the usual power supply available on board a road vehicle.

[0015] According to an advantageous embodiment of the air treatment system, the at least one electrically operated heating device comprises at least one heating foil. Heating foil can be easily adapted to the shape of objects. It is effective, relatively inexpensive, and easy to handle. In particular, when arranged on the surface of and / or in the rotor blade(s) of the fan wheel, it is particularly effective in preventing the fan wheel from freezing to the fan housing. Likewise effective is the arrangement of at least one of the at least one heating foil on the surface of or in a respective wall ring around the respective fan wheel and / or on the surface of or in the finger guard(s) arranged above the respective fan wheel.

[0016] In axial-flow fans, a wall ring is often arranged outside the tips of the fan blades. The fan wheel rotates within the area surrounded by the wall ring during operation. The surface of a wall ring also includes the inside of the fan wheel, which faces the fan wheel.

[0017] According to a further advantageous embodiment of the air treatment system, the at least one electrically operable heating device comprises at least one integrated heating element in the form of a heating wire. This is an effective and simple embodiment in which the component of the fan unit comprising the heating device can be heated directly.

[0018] The heating wire is integrated into the component.

[0019] It is advantageous to arrange at least one of the at least one integrated heating element in the fan housing.

[0020] According to a further preferred embodiment of the invention, at least one component of the ventilation unit comprising an electrically operable heating device consists at least partially of an electrically heatable material, wherein the electrically heatable material is the electrically operable heating device or a component of the electrically operable heating device. For example, an intrinsically conductive polymer is conceivable as an additive to a low-melting polymer. With a heating device that can be electrically operated using an electrically heatable material, at least one component, such as the fan wheel and / or the fan housing, can advantageously be heated directly using electrical current, so that freezing of the fan wheel to the fan housing can be counteracted.

[0021] According to a preferred development of the invention, the fan unit comprises one or more assembled fan modules, each comprising a fan motor, a fan wheel driven by a fan motor, and a fan module housing, wherein the one or more assembled fan module housings form the fan housing. Such a fan unit, with its modular design, can be easily adapted to the size and performance of the respective air treatment system. According to one possible embodiment, the power supply for the electrically operated heating device associated with the at least one component of the fan unit is possible via lines from a conductor track embedded in the respective fan module housing from fan module to fan module with corresponding line connectors.The principle of fan modules combined to form a fan unit with conductor tracks embedded in the fan module housing is disclosed in DE102006055411A1, but there for the power supply and control of the fan motor.

[0022] Finally, the features of the subclaims to claim 1 can be combined essentially freely with each other and not determined by the order in the claims, provided that they are independent of each other.

[0023] The problem underlying the invention specified in claim 14 is solved by the features listed in claim 14. The problem is solved by the fan unit for an air treatment system according to the invention comprising at least one fan motor, at least one fan wheel driven by a fan motor, and at least one fan housing as components, wherein the fan unit has at least one electrically operated heating device designed such that at least one heating element of the electrically operated heating device is arranged in a respective finger guard arranged above the respective fan wheel or is arranged on the surface of the respective finger guard. Such a fan unit has the corresponding advantages as the air treatment system according to the invention.The advantageous embodiments and further developments of the fan unit and their advantages are analogous to those of the advantageous embodiments and further developments of the air treatment system according to the invention.

[0024] Brief description of the drawings: Embodiments of the invention are explained with reference to the drawings. It shows

[0025] Fig. 1a a representation of the underside of a non-inventive embodiment of a fan unit for an air treatment system for a vehicle, Fig. 1b a vertical section through a rotor blade of a fan wheel of the Fig. 1a shown fan unit, Fig. 2 a representation of the underside of a further embodiment not according to the invention of a fan unit for an air treatment system for a vehicle, Fig. 3aa representation of the top side of another embodiment of a fan unit for an air treatment system for a vehicle, Fig. 3b a vertical section through a finger guard of the Fig. 3a shown fan unit, Fig. 4 an embodiment of an inventive system for air treatment on a vehicle roof of a ground-based vehicle, and Fig. 5 an embodiment of an air treatment system according to the invention designed as a cooling system for a ground-based refrigerated vehicle,

[0026] Detailed description of the invention: All drawings are schematic. Scale drawings have been omitted for the sake of clarity.

[0027] In Figure 1aThe underside of an exemplary embodiment of a fan unit 1 for an air treatment system for a vehicle is shown. The fan unit 1 is designed as a fan module. The fan unit 1 has, in particular, a fan housing 3 designed as a fan module housing, an electrically operated fan motor 5, and a fan wheel 7. The fan wheel 7 has, without being limited to the number, five rotor blades 9. The fan unit 1 is designed as an axial fan unit for a ventilation, air conditioning, and / or heating system for positioning on or partially integrated into a vehicle roof of a ground-based vehicle. Thus, at least one surface area of ​​the ventilation, air conditioning, and / or heating system is intended to form an outer surface area of ​​the vehicle. The fan wheel 7 is surrounded by a wall ring 11. During operation, the fan wheel 7, driven by the fan motor 5, rotates within the non-rotating wall ring 11.Above the fan wheel 7 is the finger guard 13 with its radially extending and concentrically circular struts. The fan wheel 7 comprises an electrically operated heating device 15 for each rotor blade 9. A heating wire is integrated into each rotor blade 9 as a heating element 17, which runs in serpentine lines embedded in the respective rotor blade 9. An arrangement in which the heating wire runs in an insulated manner on the surface of the respective rotor blade 9 is also conceivable. Other suitable electrically operated heating devices 15 in or on the rotor blades 9, such as a heating foil, are also conceivable.Furthermore, a variant of the fan unit 1 is conceivable in which each rotor blade 9 of the fan wheel 7 consists at least partially of an electrically heatable material, such as a polymer mixed with an intrinsically conductive polymer as an additive, wherein the electrically heatable material is the electrically operable heating device 15 or a component thereof. An example of this would be polyaniline as an additive in polypropylene.

[0028] The heating device 15 in the fan wheel 7 is designed to be operated with low-voltage electrical current of no more than 48 volts, such as 12 volts, 24 volts, or 48 volts. Power is supplied via power lines in the conductor strip 19, further to the fan motor area of ​​the fan unit 1, and from there via, for example, conventional sliding contacts, such as brush contacts, to the heating device 15 in the fan wheel 7. The conductor track 19 has cable connectors 20 at its ends. The fan unit 1, designed as a fan module, can be used individually or in any number assembled on the sides of its fan housing 3, designed as a fan module housing, for a correspondingly dimensioned system for air treatment in vehicles. Instead of a conductor track 19, other suitable types of power lines to the electrically operated heating device 15 are also conceivable.

[0029] In Figure 1bis a vertical section through a rotor blade 9 of a fan wheel of the Fig. 1a shown fan unit. Therein, a heating wire is integrated into the electrically insulating plastic material of the rotor blade 9 as an integrated heating element 17 of the electrically operated heating device. The rotor blade 9 can thus be heated electrically via the heating element 17. In this case, the heating element 17 designed as a heating wire runs in the rotor blade 9, but is not limited to this, in serpentine lines from the starting area to the rotor blade tip area and back again several times. As a variant, for example, a heating foil embedded in the plastic of the rotor blade 9 like a sandwich is conceivable as an integrated heating element 17. A rotor blade 9 in which, for example, the upper half consists of an electrically heatable material, wherein the electrically heatable material forms a component of the electrically operated heating device, is also conceivable.

[0030] In Figure 2 1 shows an underside of another exemplary embodiment of a fan unit 1 for an air treatment system for a vehicle. The fan unit 1 is designed as a fan module. The fan unit 1 comprises, in particular, a fan housing 3 designed as a fan module housing, an electrically operable fan motor 5, and a fan wheel 7. The fan wheel 7 has rotor blades 9. The fan unit 1 is designed as an axial fan unit for a ventilation, air conditioning, and / or heating system for positioning on or partially integrated into a vehicle roof of a ground-based vehicle. Thus, at least one surface area of ​​the ventilation, air conditioning, and / or heating system is intended to form an outer vehicle surface area. For example, such a fan unit 1 is also conceivable for a cooling system of a ground-based refrigerated vehicle. The finger guard 13 is located above the fan wheel 7. .The fan wheel 7 is surrounded by a wall ring 11. During operation, the fan wheel 7, driven by the fan motor 5, rotates within the non-rotating wall ring 11. On the surface of the wall ring 11, on its inner side facing the rotor blades 9, there is a heating foil 21 as an electrically operated heating device 15. The wall ring 11, which is otherwise made of plastic, is a component of the fan unit 1. It is firmly connected to the fan housing 3. As a variant, it is also conceivable, for example, to embed the heating foil 21 in the plastic of the wall ring 11 like a sandwich. Instead of the heating foil 21, other suitable types of heating elements are also conceivable, such as a heating wire integrated in the wall ring 11.Furthermore, a further variant is conceivable, a wall ring 11 consisting of an electrically heatable material, such as a polymer mixed with an intrinsically conductive polymer as an additive, wherein the electrically heatable material represents the electrically operated heating device 15. The heating device 15 with the heating foil 21 is designed to be operated with electrical current at a low voltage of not more than 48 volts, such as 24 volts. The power supply is possible via power lines in the conductor strip 19 of the fan unit 1 and further to the wall ring 11 to the heating foil 21 there. The conductor strip 19 has cable connectors 20 at its ends. The fan unit 1, designed as a fan module, can be used individually or in any number assembled on the sides of its fan housing 3, designed as a fan module housing, for an appropriately dimensioned system for air treatment for vehicles.For example, it is arranged there as a fan unit 1 for dissipating heat from a condenser or gas cooler of a vehicle air conditioning system to the ambient air. Instead of a conductor track 19, other suitable types of power lines to the electrically operated heating device 15 are also conceivable.

[0031] In Figure 3a is a top view of an embodiment of a fan unit 1 according to the invention for an air treatment system for a vehicle, such as a vehicle roof-mounted system. This fan unit 1 is composed of four fan modules joined together. The fan module housings joined together laterally form the fan housing 3. Each of the four fan modules designed as axial fans comprises, as components of the fan unit 1, in particular Figure 3aEach covers a fan motor and a fan wheel driven by the respective fan motor. Above each of the four fan wheels is a finger guard 13 with radially extending and annularly concentrically extending struts 23. The design of the finger guards 13 is not limited to this, but can also have other suitable shapes, such as a grid of longitudinal and transverse struts. Each of the four finger guards 13 comprises an electrically operated heating device 15 with heating wires as heating elements 17. The heating wires are integrated into the struts 23 of the respective finger guard 13, for example, cast into the plastic of the struts 23. It is also conceivable, for example, to wrap individual struts 23 of the finger guard 13 with heating wire or heating foil as an electrically operated heating device 15.Furthermore, a sandwich-like embedding of heating foil in the plastic of the struts 23 of the respective finger guard 13 is conceivable.

[0032] As a further variant, the construction of the finger guard 13 from injection-molded plastic in the upper half and an electrically heatable material in the lower half, such as a polymer mixed with an intrinsically conductive polymer as an additive, is also conceivable, wherein the electrically heatable material is then a component of the electrically operated heating device 15.

[0033] The heating devices 15, with their respective heating elements 17 configured as heating wires, are designed to be operated with low-voltage electrical current of no more than 48 volts, such as 24 volts. However, designs for higher voltages are also conceivable. Power is supplied via power lines in the conductor tracks 19 of the fan unit 1 and further to the respective finger guard 13 to the heating element 17 configured as a heating wire. Each conductor track 19 has corresponding cable connectors 20 at its ends for this purpose. Instead of conductor tracks 19, other suitable types of power lines to the electrically operated heating devices 15 in the finger guards 13 are also conceivable. The number of fan wheels per fan unit 1 is not limited to four; more or fewer fan wheels, such as just a single one, are possible depending on the size of the vehicle air treatment system.A non-inventive embodiment is also conceivable in which the electrically operated heating device 15 is not located in the finger guard 13 but in or on other areas of the fan housing 3 or in or on the housing of the fan motor. Furthermore, combinations of the embodiments described in the . Figure 1a , 2 and 3a illustrated embodiments such as electrically operated heating devices in the respective wall ring and finger protection can be realized.

[0034] In Figure 3b is a vertical section across a finger guard 13 of the Fig. 3aThe fan unit shown is shown. The integrated heating element 17 of the electrically operated heating device 15, designed as a heating wire, runs in the concentrically arranged annular struts 23 of the finger guard 13. The heating wire is embedded in the plastic of the struts 23 of the finger guard 13. This allows the finger guard 13 to be electrically heated as a component of the fan unit.

[0035] In Figure 4An embodiment of an air treatment system 30 according to the invention is shown on a vehicle roof 34 of a ground-based vehicle 36. A variant of the air treatment system 30 designed to be partially integrated in the vehicle roof 34 for positioning is also possible. The air treatment system 30 is in this case an air conditioning and heating system. Accordingly, a design as a pure air conditioning, heating, or ventilation system is also conceivable. Centrally located on the top side of the air treatment system 30 is a fan unit 1 of the system 30. In this embodiment, this serves to cool the air of the condenser or gas cooler of the air treatment system 30 designed as an air conditioning and heating system. The fan unit 1 has five axial fans inserted into the fan housing 3 and arranged longitudinally in series, with finger guards 13 underneath the five Figure 4Five concealed fan wheels, each of which is assigned to and driven by an electric fan motor. The number of fan wheels and fan motors varies depending on the size of the air treatment system, so that one embodiment may, for example, have only one fan wheel.

[0036] Each of the five finger guards 13 is a component of the fan unit 1 and includes an electrically operated heating device. The respective electrically operated heating device in the finger guard 13 corresponds to the Figure 3a and 3b Furthermore, each of the Figure 4 concealed wall rings around the respective fan wheel via an electrically operated heating device such as Figure 2described. The power supply for the electrically operated heating devices of the finger guards 13 and wall rings is provided by the vehicle's own low-voltage power source, with a voltage of, for example, 48 volts, through lines of the conductor track 19 in the fan housing 3. The air treatment system 30 contains a control system 32 designed to regulate the heating output of the electrically operated heating devices in the finger guards 13 and the wall rings. The control system 32 receives signals from an outside temperature sensor 33 and from the respective fan motor, so that at outside temperatures below 0 °C and a blockage of the respective fan wheel, the respective electrically operated heating devices are supplied with power for heating, thereby enabling the fan wheel, which has frozen to the wall ring, for example, to rotate freely again during operation.Versions of the air treatment system are also conceivable that, for example, contain electrically operated heating devices only in the finger guards 13 of the fan unit 1. The ground-based vehicle 36 in this case is a bus. Other ground-based vehicles 36 with an air treatment system according to the invention are also conceivable, such as a rail vehicle.

[0037] In Figure 5 An embodiment of an air treatment system 30 according to the invention is shown, designed as a cooling system for a ground-based refrigerated vehicle. The fan unit 1 of the system 30 is arranged on its upper side. As shown in Figure 5 As can be seen, a surface area, such as in particular the finger guard 13 of the fan unit 1, is intended to form an outer surface area of ​​the vehicle. The fan unit 1 has as components in particular a Figure 5concealed fan motor, a fan wheel driven by the fan motor and a fan housing 3. In the fan housing 3 there is a finger guard 13 above the Figure 5 The fan wheel includes an electrically operated heating device in its rotor blades as Figure 1a and 1bdescribed. The control system 32 for controlling the heating output of the heating device receives signals from an outside temperature sensor 33 and from the respective fan motor, so that at outside temperatures below 0 °C and if the fan wheel is blocked, the electrically operated heating device in the fan wheel is supplied with power for heating, and as a result, the fan wheel, which has frozen to the fan housing 3, for example, can rotate freely again during operation. Embodiments of air treatment systems 30 designed as cooling systems for refrigerated vehicles, comprising a fan unit 1 with two or more fan wheels, each of which comprises an electrically operated heating device and driven by a respective fan motor, are also conceivable.

[0038] In addition, electrically operated heating devices are installed, for example in the wall ring around the fan wheel, such as Figure 2 described can be realized.

Claims

1. Facility for air treatment (30) for a vehicle, comprising at least one fan unit (1) having at least as its components at least one fan motor (5), at least one fan wheel (7) that can be driven by a fan motor (5), and at least one fan housing (3), wherein at least one surface region of the facility (30) is provided to form a vehicle outer surface region, characterised in that the at least one fan unit (1) comprises at least one electrically operable heating device (15) configured such that at least one heating element (17) of the electrically operable heating device (15) is arranged in a respective finger guard (13) arranged above the respective fan wheel (7) or is arranged on the surface of the respective finger guard (13).

2. Facility for air treatment (30) according to claim 1, characterised in that at least one heating element (17) of at least one of the at least one electrically operable heating device (15) is arranged in the rotor blads of the fan wheel (7) of the fan unit (1) and / or in a respective wall ring (11) arranged around the respective fan wheel (7).

3. Facility for air treatment (30) according to either claim 1 or claim 2, characterised in that it is configured as a ventilation, air-conditioning and / or heating facility for positioning on or partially integrated in a vehicle roof (34) of a ground-based vehicle (36).

4. Facility for air treatment (30) according to either claim 1 or claim 2, characterised in that it is configured as a cooling facility for a ground-based refrigerated vehicle.

5. Facility for air treatment (30) according to any of claims 1 to 4, characterised in that it comprises a controller (32) configured for controlling the heating power of the at least one electrically operable heating device (15).

6. Facility for air treatment (30) according to any of claims 1 to 5, characterised in that the at least one electrically operable heating device (15) is configured such that it is operable with low-voltage power of a voltage of no more than 48 volts.

7. Facility for air treatment (30) according to any of claims 1 to 6, characterised in that the at least one electrically operable heating device (15) comprises at least one heating film (21) as the heating element (17).

8. Facility for air treatment (30) according to claim 7, characterised in that at least one of the at least one heating film (21) is / are arranged in the rotor blades (9) of the fan when (7).

9. Facility for air treatment (30) according to either claim 7 or claim 8, characterised in that at least one of the at least one heating film (21) is / are arranged in the fan housing (3).

10. Facility for air treatment (30) according to any of claims 7 to 9, characterised in that at least one of the at least one heating film (21) is arranged in a respective wall ring (11) around the respective fan wheel (7).

11. Facility for air treatment (30) according to any of claims 1 to 10, characterised in that the at least one heating element (17) of the at least one electrically operable heating device (15), which element is integrated in the finger guard (13), comprises a heating wire.

12. Facility for air treatment (30) according to any of claims 1 to 11, characterised in that at least one component of the ventilation unit (1) comprising an electrically operable heating device (15) consists at least in part of an electrically heatable material, wherein the electrically heatable material is the or part of the electrically operable heating device (15).

13. Facility for air treatment (30) according to any of claims 1 to 12, characterised in that the fan unit (1) comprises one or more assembled fan module(s) each comprising, as components, a fan motor (5), a fan wheel (7) that can be driven by a fan motor (5), and a fan module housing, wherein the one or the plurality of assembled fan module housings form the fan housing (3).

14. Fan unit (1) for a facility for air treatment (30) according to any of claims 1 to 13 comprising, at least as components, at least one fan motor (5), at least one fan wheel (7) that can be driven by a fan motor (5), and at least one fan housing (3), characterised in that the fan unit (1) comprises at least one electrically operable heating device (15) configured such that at least one heating element (17) of the electrically operable heating device (15) is arranged in a respective finger guard (13) arranged above the respective fan wheel (7) or is arranged on the surface of the respective finger guard (13).

15. Fan unit (1) according to claim 14, characterised in that at least one heating element (17) of at least one of the at least one electrically operable heating device (15) is arranged in the rotor blades of the fan wheel (7) of the fan unit (1) and / or in a respective wall ring (11) arranged around the respective fan wheel (7).