EP2971789B1

EP2971789B1 - Axial fan comprising a detachably attached fan wheel

Info

Publication number: EP2971789B1
Application number: EP13708816.7A
Authority: EP
Inventors: Hans HONETH
Original assignee: Fresh AB
Current assignee: Fresh AB
Priority date: 2013-03-11
Filing date: 2013-03-11
Publication date: 2017-11-01
Anticipated expiration: 2033-03-11
Also published as: EP2971789A1; WO2014139555A1

Description

Technical Field

The present invention concerns an axial fan comprising a casing, that defines a circular through opening, an electric motor, that is arranged in a center of said through opening and has a rotation axis aligned with a central axis of said through opening, and a detachably attached fan wheel, that has a central hub pushed into engagement over a rotatable part of said motor.

Prior Art

An axial fan with a detachably attached fan wheel according to the preamble is revealed in the prior art document JP 2005797 A . According to that document the purpose of making the fan wheel detachable is to render cleaning of the fan easier, which is achieved by disposal of a detached, used fan wheel and replacing it with an all new one, wherein the fan wheel as such is said to be of a combustible material, e.g. as cardboard.
An advantage of the known detachable fan wheel is that it renders access to other parts of a fan that can need cleaning, such as its casing, its through opening or its motor, easier, and that there besides hygiene problems are other problems too, caused by an not appropriately cleaned fan wheel, such as reduced efficiency, leading to a waist of energy, or imbalance, shortening life of fan bearings. There is, however, the disadvantage that one obviously first has to purchase a spare fan wheel before one initiates a cleaning operation, since the fan wheel appears to be designed as a one way product. This requires some planning and logistics and can cause severe time delay if a spare fan wheel is not easy available, e.g. because it belongs to a series of fans no longer marketed. Further, the known detachable fan wheel does not seem to have any particular means relieving the fan motor and its bearings from stress when the fan wheel is detached. This can, if one is incautious, lead to malfunction and the need to replace the whole fan instead.

Object of the Invention

Against that background an object of the present invention is to improve the axial fan according to the preamble by making the fan wheel easier detachable as well as reusable and hence more environmental friendly.

Summary of the Invention

According to the present invention in an axial fan comprising a casing, that defines a circular through opening, an electric motor, that is arranged in a center of said through opening and has a rotation axis aligned with a central axis of said through opening, and a detachably attached fan wheel, that has a central hub pushed into engagement over a rotatable part of said motor, this is achieved in that said hub has at least one front access aperture arranged to render application of pressure possible on said rotatable part in a first direction in parallel with said central axis and towards said motor when detaching said fan wheel by pulling it in a direction opposite to said first direction, wherein said at least one access aperture is sized to render said application of pressure possible by means of a human finger, and wherein said fan wheel is made of a waterproof and hence rinsable material.
By providing at least one adequately sized front access aperture the axial fan according to the present invention enables a user wishing to clean the fan to grab the fan wheel with just one hand and to detach it by a slight push of a finger via said access aperture against the rotatable part of said motor without imparting any forces risking the integrity of the motor or the fan wheel itself. Then the detached fan wheel can be thoroughly cleaned, preferably by rinsing it under water, and attached anew.
Preferably there is just one access aperture centrally arranged in the hub of said fan wheel. Out of balance reasons as well as ergonomic ones, this is currently seen as the optimum solution.
Preferably a hub cap is provided on said rotatable part closing the access aperture from behind, such that said application of pressure is rendered possible via the hub cap. A hub cap can enhance the appearance of the axial fan in many ways. Primarily by making the access aperture part become flush with the remainder of the central hub of the fan wheel, but also by an adequate choice of colour in relation to the fan wheel, such as the exact same colour or a contrasting one, or e.g. by showing a manufacturer's logo-type.
According to one embodiment a resilient diaphragm covering the access aperture is provided on the hub of the fan wheel, wherein said diaphragm preferably is formed integrally with said hub by two-shot injection moulding. A solution like that is not quite as simple as the one with an open access aperture or one filled from behind by a hub cap, but if the diaphragm is made of an appropriate resilient material, it works quite well and is easy manufacturable as well, especially if injection moulded in a two-shot plastic moulding process.
Preferably said hub is adapted to engage the rotatable part of said motor by means of a snap fit, the major advantage of a snap fit solution being that it provides a distinct indication when the fan wheel while being attached has reached its intended place.
According to the invention the snap fit is preferably created in that said hub has a number of resilient tongues adapted to engage with a circular undercut boss about said rotation axis of the rotatable part of said motor in that beads of said tongues snap into a circumferential groove formed by the undercut of said boss. This is advantageous because it makes it possible to snap the fan wheel in place irrespective of the rotation angle of the rotatable part of said motor.
Preferably the hub of said fan wheel is cup shaped in order to encompass the rotatable part of said motor, said at least one access aperture being arranged in a bottom portion of the cup shape. This solution does serve to enhance the overall appearance of the axial fan but it also provides a good fit for the fan wheel.
This fit can be improved even more if the hub of said fan wheel is circular cylindrical, a first internal bevel being formed peripherally at a junction between said bottom portion and a circumferential side wall of the cup shaped hub and a second internal bevel being formed peripherally at a brim portion of the cup shaped hub, wherein, when the hub of said fan wheel engages the rotatable part of said motor, said first internal bevel is arranged to centeringly cooperate with a corresponding first external bevel on said rotatable part and said second internal bevel is arranged to centeringly cooperate with a corresponding second external bevel of a rim surrounding said rotatable part.
The rotatable part of said motor is preferably a substantially cup shaped rotor housing of a brushless DC electric motor, having an internal stator that is held in the center of said through opening by means of a number of spokes. All the maintenance a solution like that requires is cleaning from time to time, which is rendered extremely easy also when it comes to the motor and spokes once the fan wheel has been detached.

Brief Description of the Drawings

In the following a preferred embodiment of the axial fan according to the present invention is described in more detail with reference being had to the enclosed drawings, in which

Fig. 1 is an exploded view in perspective showing a fan wheel detached from a fan casing illustrated behind;
Fig. 2 is an exploded view in perspective showing the fan wheel and parts belonging to a rotor of a fan motor;
Fig. 3 is a plan view showing the fan wheel and said parts belonging to said rotor from behind;
Fig. 4 is a cross-sectional view along section line IV-IV of fig. 3; and
Fig. 5 is a cross-sectional view of area V of fig. 4.

Description of a Preferred Embodiment

Axial fans are known in a great variety and for many purposes, such as wall or ceiling mounted fans for ventilating rooms or computer chassis mounted fans for cooling electronics. In any case, axial fans require cleaning from time to time, especially their fan wheels, on which dust tends to adhere and lessen efficiency. Traditionally cleaning is performed by means of a vacuum cleaner or purely manual by means of a dust brush. Regardless of the cleaning method chosen, it is easy to miss some dust, which besides hygiene problems can lead to fan wheel imbalance, causing noise and shortening life of fan bearings.
The axial fan 1 shown in the drawings is intended to be used as a wall or ceiling mounted ventilating fan, e.g. in a bathroom. In other words, it is usually mounted at a height that requires a user to climb onto a stool or ladder in order to reach the fan 1 for cleaning or maintenance purposes. It is obvious that handling cleaning equipment in a position like that bears some risk for the user falling down. In the light of this, the axial fan 1 shown in the drawings is designed such that its fan wheel 5 is easy detachable and hence cleanable in a safe position, preferably by rinsing under water in a sink. Below there is a detailed description of how this is made possible in a convenient way, wherein like reference numbers in the different drawing figures denote the same parts throughout.
The axial fan 1 comprises a casing 2, that defines a circular through opening 3, an electric motor 4, that is arranged in a center of said through opening 3 and has a rotation axis r (c.f. fig. 4) aligned with a central axis of said through opening 3, and a detachably attached fan wheel 5, that has a central hub 6 pushed into engagement over a rotatable part 7 of said motor 4. The rotatable part 7 of the motor 4 is a substantially cup shaped rotor housing of a brushless DC electric motor, having an internal stator that is held in the center of said circular through opening 3 by means of a number of spokes 18.
In the preferred embodiment said hub 6 has a centrally arranged front access aperture 8 sized to render application of pressure possible by means of a human finger on said rotatable part 7 in a first direction in parallel with said central axis and towards said motor 4 when detaching said fan wheel 5 by pulling it in a direction opposite to said first direction. This is illustrated by the exploded views in figs. 1 and 2, where a hub cap 9 is shown provided on said rotatable part 7, said hub cap 9 closing the access aperture 8 from behind and serving as a finger rest, such that said application of pressure is rendered possible on the rotatable part 7. The hub cap 9 is attached to the rotatable part 7 by means of three tongues 19 adapted to engage corresponding orifices 20 in the rotatable part 7, said tongues 19 having beads 21 protruding from said tongues 19 in a direction pointing away from said rotation axis r and being slightly rounded (c.f. fig. 5) such that detachment is possible without harming the tongues 19 or their beads 21.
As can be seen especially in figs. 4 and 5, the hub 6 of the fan wheel 5 is adapted to engage the rotatable part 7 of said motor 4 by means of a snap fit. To this purpose the hub 6 has a number of resilient tongues 10 (c.f. fig. 2) adapted to engage with a circular undercut boss 11 about said rotation axis r of the rotatable part 7 of said motor 4 by means of beads (not shown) protruding from said tongues 10 towards the center of the fan wheel 5. Said beads are to snap into a circumferential groove 12 formed by the undercut of said boss 11 and are detachable therefrom by being shaped in a way resembling the beads 21 on the tongues 19 of the hub cap 9 described above.
The fan wheel 5 as such is preferably made of plastics. Hence it is waterproof and rinsable under water. Its hub 6 is cup shaped and made to encompass the rotatable part 7 of said motor 4, wherein said access aperture 8, as clearly shown in the viewing angle of fig. 2, is arranged in a bottom portion of the cup shape.
In order to provide an optimum fit free from play or imbalance of the fan wheel 5 on the rotatable part 7 of said motor 4, the hub 6 of said fan wheel 5 is circular cylindrical. It has a first internal bevel 13 formed peripherally at a junction between said bottom portion and a circumferential side wall of the cup shaped hub 6 and a second internal bevel 14 formed peripherally at a brim portion of the cup shaped hub 6. Of these bevels 13, 14, when the hub 6 of said fan wheel 5 engages the rotatable part 7 of said motor 4, said first internal bevel 13 is arranged to centeringly cooperate with a corresponding first external bevel 15 on said rotatable part 7 and said second internal bevel 14 is arranged to centeringly cooperate with a corresponding second external bevel 16 of a rim 17 surrounding said rotatable part 7.
The person skilled in the art is aware that the preferred embodiment described above can be varied in many ways within the scope of the appendant claims, e.g. by altering the shape of the fan wheel or the kind of motor used to rotate it.

Claims

An axial fan (1) comprising a casing (2), that defines a circular through opening (3), an electric motor (4), that is arranged in a center of said through opening (3) and has a rotation axis (r) aligned with a central axis of said through opening (3), and a detachably attached fan wheel (5), that has a central hub (6) pushed into engagement over a rotatable part (7) of said motor (4),
characterised in
that said hub (6) has at least one front access aperture (8) arranged to render application of pressure possible on said rotatable part (7) in a first direction in parallel with said central axis and towards said motor (4) for detaching said fan wheel (5) and pulling it in a direction opposite to said first direction, wherein said at least one access aperture (8) is sized to render said application of pressure possible by means of a human finger, and wherein said fan wheel (5) is made of a waterproof and hence rinsable material.
The fan (1) according to claim 1, wherein there is just one access aperture (8) centrally arranged in the hub (6) of said fan wheel (5).
The fan (1) according to claim 2, wherein a hub cap (9) is provided on said rotatable part (7) closing the access aperture (8) from behind, such that said application of pressure is rendered possible via the hub cap (9).
The fan (1) according to claim 2 or 3, wherein a resilient diaphragm covering the access aperture (8) is provided on the hub (6) of the fan wheel (5).
The fan (1) according to claim 4, wherein said diaphragm is formed integrally with said hub (6) by two-shot injection moulding.
The fan (1) according to any one of claims 1-5, wherein said hub (6) is adapted to engage the rotatable part (7) of said motor (4) by means of a snap fit.
The fan (1) according to claim 6, wherein said hub (6) has a number of resilient tongues (10) adapted to engage with a circular undercut boss (11) about said rotation axis (r) of the rotatable part (7) of said motor (4) in that beads of said tongues (10) snap into a circumferential groove (12) formed by the undercut of said boss (11).
The fan (1) according to any one of claims 1-7, wherein the hub (6) of said fan wheel (5) is cup shaped in order to encompass the rotatable part (7) of said motor (4), said at least one access aperture (8) being arranged in a bottom portion of the cup shape.
The fan (1) according to claim 8, wherein the hub (6) of said fan wheel (5) is circular cylindrical, a first internal bevel (13) being formed peripherally at a junction between said bottom portion and a circumferential side wall of the cup shaped hub (6) and a second internal bevel (14) being formed peripherally at a brim portion of the cup shaped hub (6), wherein, when the hub (6) of said fan wheel (5) engages the rotatable part (7) of said motor (4), said first internal bevel (13) is arranged to centeringly cooperate with a corresponding first external bevel (15) on said rotatable part (7) and said second internal bevel (14) is arranged to centeringly cooperate with a corresponding second external bevel (16) of a rim (17) surrounding said rotatable part (7).
The fan (1) according to any one of claims 1-9, wherein the rotatable part (7) of said motor (4) is a substantially cup shaped rotor housing of a brushless DC electric motor, having an internal stator that is held in the center of said circular through opening (3) by means of a number of spokes (18).