US20020192075A1

US20020192075A1 - Fan

Info

Publication number: US20020192075A1
Application number: US09/880,613
Authority: US
Inventors: Volker Block
Original assignee: EGO Elektro Geratebau GmbH
Current assignee: EGO Elektro Geratebau GmbH
Priority date: 2001-06-13
Filing date: 2001-06-13
Publication date: 2002-12-19

Abstract

The invention relates to a fan for producing a fluid flow, particularly an air flow.

The problem of the invention is to provide a fan for a heatable fluid flow, in which the necessary energy consumption is reduced.

A fan according to the invention has an impeller, which has at least one blade for delivering the fluid. On at least part of the blades of the fan impeller is provided at least one heating element used for heating the fluid during the delivery operation of the fan.

Description

Fans for producing a fluid flow, particularly an air flow, are used in numerous different ways. Such fans have an impeller and at least one blade constructed or placed thereon for delivering the fluid. In principle, such fans are generally known in the form of radial-flow fans and axial-flow fans. In the case of radial-flow fans the blades produce an air flow, which is directed radially away from the rotation axis of the radial-flow fan and diverted in an outflow direction by the casing surrounding the fan and which is oriented at right angles to the rotation axis of the fan. In the case of axial-flow fans a fluid flow is produced in the direction of the fan rotation axis.

Such fans are more particularly used for the delivery of gaseous fluids, particularly air. Such fans are also able to deliver liquid media.

Applications arise where the delivered fluid is not only delivered, but also has to be heated. The heating of the delivered fluid conventionally takes place by means of one or more heating elements positioned behind the fan. For monitoring the temperature a temperature sensor is positioned in general behind the heating element and by means thereof the fan performance and/or heating capacity of the heating element are matched to one another in such a way that the conveyed fluid temperature can be controlled or regulated.

It is a disadvantage of such constructions that the heating element following the fan represents a flow resistance for the fluid flow. Thus, the delivery rate of the fan must be made higher than would be necessary for purely delivering the fluid. In addition, following heating elements suffer from the disadvantage that as a result of their function as a flow resistance and as a fixed, flowed-round component, impurities contained in the fluid can be deposited thereon. If the fluid is air, then frequently dust particles are deposited on the heating elements. Into said dust particles can be incorporated impurities of the air, such as e.g. grease and water vapours. This is undesired for reasons of the delivery rate, heating element efficiency and hygiene.

The problem of the invention is to provide a fan for a heatable fluid flow, where the necessary energy consumption is reduced.

On the basis of the prior art features, this problem is solved by a fan having the characterizing features of claim 1. A fan according to the invention has an impeller with at least one blade for delivering the fluid. At least one heating element is provided on at least one part of the fan impeller blades. The heating element is used for heating the fluid during the delivery operation of the fan.

According to a preferred development the heating elements are constructed as a electrical heating elements and they are preferably chosen from the group composed of thick films, strip heaters and electrically conductive ceramics.

Preference is given to constructions in which the heating elements are located on the surface of the blades. It is particularly advantageous for the heating elements to be placed in heating element channels constructed on the blade side. It is also advantageous for the heating elements to be constructed in such a way that they supplement the blades of a projection-free, smooth surface contour.

Preference is also given to constructions in which the heating elements are positioned roughly along and parallel to the leading blade edge in the rotor rotation direction. It is also advantageous if the heating elements extend over at least virtually the entire linear extension of the blades.

It is also advantageous if there is a temperature sensor at least on part of the blades. Preferably the temperature sensor controls or regulates the heating capacity of heating elements, so that the temperature of the delivered air is controlled or regulated. According to a preferred development the temperature sensor, considered in the blade rotation direction, is positioned behind an optionally present heating element. According to another advantageous development of the invention temperature sensors are placed on blades having at least one heating element.

According to a preferred development of the invention the heating conductors or heaters are combined into at least two groups, the heating capacity being controlled or regulated by the optionally also timed switching on or off of heater groups. According to a preferred development of the invention heaters of one blade are associated with the same group. According to a further extending, advantageous development of the invention it is possible for the heaters of one group to be arranged in a mutual parallel connection. In this and also other constructions of parallel-connected heaters, it is advantageous according to the invention if each of the heaters has a blow-out fuse associated therewith to prevent excessive heating.

According to alternative developments of the invention the fan can be both an axial-flow fan and a radial-flow fan. In the case of a radial-flow fan it is possible for electrical contacting to take place in that the blades with the heaters located thereon to produce the electrical connection between the two impellers of the radial-flow fan and are consequently supplemented to form circuits. It is in general terms possible for the blades of the fan, which have a heating element, to be formed from a basic structure, a thick film heating element enveloping said basic structure and the outer, laminar material film forms the blade surface.

A preferred use of such a fan occurs in domestic appliances such as (hot air) baking ovens or spin/tumbler dryers. A use is also possible in other electrical appliances such as e.g. hair dryers, hand dryers, etc. Further applications can e.g. exist in blowers, particularly in motor vehicles, as well as in (vane) pumps. All that is important is that the fan delivers a fluid, which is simultaneously heatable.

The aforementioned and further features can be gathered from the claims, the description and the drawings and the individual features, both singly or in the form of subcombinations, can be implemented in an embodiment of the invention and in other fields and can represent advantageous, independently protectable constructions for which protection is hereby claimed.

The invention is further described relative to embodiments shown in the attached drawings, wherein represent: [0016]
FIG. 1 Diagrammatically an axial-flow fan according to the invention. [0017]
FIG. 2 Diagrammatically a radial-flow fan according to the invention.[0018]
FIG. 1 diagrammatically shows an axial-flow fan according to the invention. [0019]
It is possible to see a [0020] fan 11, which is constituted by a centrally positioned impeller 12 drivable by a not shown drive and four blades 13 arranged in rotationally symmetrical manner with respect to the centre of the impeller 12. The blades 13 can be convex or flat, e.g. sheet metal and in particular punched or stamped blades, which in connection with the delivery of the fluid have a surface set about a rotation axis 14 with respect to the rotation plane of the fan 11. Alternatively the blades 13 can have a complicated construction and which have been optimized with respect to their delivery rate at a specific speed. The laminar design of the blades is independent of the implementation of the invention.
On part or, as shown, on each of the blades can be located a heating element, e.g. a [0021] thick film heater 15. If the blade 13 comprises a punched or stamped metal plate, initially an insulating layer and then the thick film heater 15 is applied to the plate surface. It is possible to use conventional coating procedures used in this connection. The power supply is selected in such a way that there is a closed current path on a blade and in the vicinity of the mounting support of the blade 13 is contacted with the impeller 12. Contacting can be brought about by conventional means such as the soldering of the contacts, whilst it is also possible to provide clamping connections, which are automatically contacted on fixing the blades 13 to the impeller 12.
A [0022] temperature sensor 16 is also located in the centre of the blade 13 and is surrounded by the thick film heater loop 15 and is also contacted in the vicinity of the impeller 12. The signals and measured values of the temperature sensor 16 can be used for controlling and regulating the performance and speed of the fan.
The contacting of the impeller with fixed components located on the fan casing can e.g. take place by means of conventional brush contacts or via inductively operating couplings. [0023]
To ensure that the fluid flowing past the [0024] blades 13 has a good contact with the thick film heater 15, the latter is preferably located on the side of the blade 13 which is exposed to the more powerful fluid flow, i.e. the front side considered in the fan rotation direction.
To control or regulate the heating capacity, it can be advantageous to combine the heaters into groups. For example the two heaters can be associated with facing blades of a group, which are always switched on or off together. The heating capacity of the fan is then influenced through the number of switched on groups. It is possible within a single group to wire the [0025] heaters 15 in parallel. If then one of the heaters is damaged with a corresponding circuit interruption, the other heater in the group remains intact. Thus, in the present case two groups of heaters could be formed and in the case of the operation of only a single heater group, roughly half the maximum possible heating capacity would be available. Through a correspondingly timed operation of the heaters there can be a virtually continuous regulation of the power or capacity up to the maximum possible level.
FIG. 2 diagrammatically shows a radial-[0026] flow fan 11.
The [0027] fan 11 rotates about rotation axis 14 in the fan casing. In the vicinity of the rotation axis 14 can be provided corresponding contacts, particularly brush sliding contacts, for contacting electric lines and for closing circuits. The blades 13 extend parallel to the rotation axis 14 between the two impellers 12. The surfaces of the blades 13, which can once again be planar or convex, are inclined slightly with respect to the radial orientation, so that medium is conveyed.
The [0028] blades 13 can be manufactured from a structure, which is e.g. a plastic injection moulding. During the injection moulding of the structure it is possible to simultaneously injection mould round the heating element ends and/or metal punched grids, which are used for the electrical connection of the individual heating elements and for contacting with the power supply (insert technology). The heating element 15 extends over the entire length of a blade 13. The temperature sensor 16 extends parallel to the heating element 15 and is located behind it in the fluid flow direction.
The structure of the [0029] blade 13 can have recesses for the heater 15 and temperature sensor 16, so that following the introduction or application of the heater and the temperature sensor there is a closed, smooth blade surface. It is also possible for the structure to be chosen in such a way that the blades are first supplemented by the heaters 15 and optionally by the temperature sensor 16, which have the function and operation of a closed blade, i.e. the structure is wholly or zonally enveloped by heaters 15 and/or temperature sensors 16.
If the heater extends over the entire length of a blade, the simplest situation is if it is contacted on both sides with the [0030] impeller 12. If, with the exception of specific line portions intended for this purpose, the rotation axis or pivot 14 is non-conductively constructed and consequently the two impellers 12 are isolated, it is easiest for the contacting and power supply to take place from one side of the fan to the other and consequently the circuit is supplemented by the heating element 15 to form a closed circuit.
As shown in the drawings, it is not necessary for all the [0031] blades 13 to have a heater 15 and/or a temperature sensor 16. It is also not necessary for all the blades 13, which have a heater 15, to have a temperature sensor 16. It is also conceivable for a blade 13 to have a temperature sensor 16, although said blade 13 has no heater 15.
As explained relative to FIG. 1, it is possible to combine the [0032] heaters 15 into groups and within a group the heaters are preferably connected in parallel. As a result of the then possible stepwise switching on of individual groups, a stepped control/regulation of the fan heating capacity is possible.
The electrical contacting of the [0033] impeller 12 can e.g. take place by means of a slip ring 17 and casing-side carbon brushes running thereon. From the slip ring 17 the current is supplied by means of an electrical line 18, which is mainly radially directed and which simultaneously can incorporate a distributor ring for the power supply to several blades 13, is supplied to at least one blade 13, which has a heating element 15 extending over the entire width of a blade. On the other side of the blade 13 once again an electrical line 18 and a slip ring 17 returns the current to the other side of the casing and from there back to the power supply, so that a closed circuit is obtained.
Alternatively to the use of a thick film heater it is possible to use a strip heater or some other electrical heater on the surface of a blade. It is particularly easy to produce a strip heater positioned between the two [0034] impellers 12 of the radial-flow fan 11.
In the case of all the embodiments it is possible to so dimension the [0035] heater 15 in at least one heating area thereof in such a way that it burns out when there is an excess temperature at said point and consequently the circuit is interrupted. This reliably prevents an inadmissible overheating of the heater. If the other heaters are arranged in parallel and not in series to said heater, their function is not impaired as a result of this.

Claims

1. Fan, with an impeller and at least one blade for delivering a fluid, wherein at least one heating element (15) for heating the delivered fluid is provided on at least one part of the blades (13).

2. Fan according to claim 1, wherein heating elements (15) are constructed as electrical heating elements and are chosen from the group of thick film heaters, strip heaters and electrically conductive ceramics.

3. Fan according to claim 1, wherein heaters (15) are placed on the surface of the blades (13).

4. Fan according to claim 3, wherein the heating elements (15) are located in heating element channels constructed on the blade side.

5. Fan according to claim 1, wherein the heating elements (15) are constructed in such a way that they supplement the blades (13) so that a projection-free, smooth surface contour is formed.

6. Fan according to claim 1, wherein the heating elements (15) are placed roughly along and parallel to the leading edge of the blades (13) in the rotor rotation direction.

7. Fan according to claim 1, wherein a temperature sensor (16) is placed on at least part of the blades (13).

8. Fan according to claim 7, wherein, considered in the blade rotation direction, the temperature sensor (16) is placed behind a heating element (15).

9. Fan according to claim 7, wherein the temperature sensors (16) are placed on blades (13) having at least one heating element (15).

10. Fan according to claim 1, wherein the heaters are combined into at least two groups, the heating capacity preferably being controlled or regulated by switching on or off groups of heaters (15).

11. Fan according to claim 10, wherein the heaters (15) of a blade (13) are associated within the same group.

12. Fan according to claim 1, wherein it is part of an axial-flow fan.

13. Fan according to one of the claim 1, wherein it is part of a radial-flow fan.

14. Fan according to claim 13, wherein the electrical contacting of the heaters (15) takes place in that blades (13) with heaters (15) located thereon produce an electrical connection between two impellers (12) of the radial-flow fan and consequently are supplemented to form circuits.

15. Fan according to claims 13, wherein blades (13) comprise a base structure, which at least zonally is coated with a thick film heating element.

16. Use of a fan according to claim 1 in a domestic appliance.

17. Use of a fan according to claims 1 in a device of the group composed of baking ofen, particularly a hot air baking oven, spin/tumbler dryer, hand dryer.

18. Use of a fan according to claim 1 in vane pumps and blowers in motor vehicles.