Patent Description:
Fans are used in a vast number of different applications such as within the area of air heat exchangers. An air heat exchanger typically comprises a casing enclosing a great number of fins arranged in an aligned manner, one after the other, in a fin stock. The fins are each provided with a matrix of holes through which a plurality of tubes extend. The tubes extend back and forth through the fin stock, essentially perpendicularly to an extension plane of the fins. At one end the tubes are connected to a fluid inlet, and at the other end the tubes are connected to a fluid outlet, for feeding a fluid through the air heat exchanger. The air heat exchanger further comprises one or more fans arranged to draw air through the fin stock, i.e. through the parallel flow channels between the fins, to transfer heat between the fluid in the pipes and the air. The air enters the air heat exchanger through and air inlet with a temperature T<NUM> and leaves the air heat exchanger through an air outlet with a temperature T<NUM> which may be higher or lower than T<NUM> depending on whether the air heat exchanger is used for cooling or heating the fluid in the pipes.

To optimize the performance of the air heat exchanger, recirculation of air through the air heat exchanger should be avoided. To prevent, or at least reduce, such air recirculation, the air heat exchanger may be provided with an air guide for each fan. The air guide typically looks like a static propeller mounted in a rim and it is arranged after the fan as seen in an air flow direction. The air guide comprises blades or vanes extending from the rim to a hub inside the rim. These vanes increase the air throwing distance of the fan which in turn decreases air recirculation through the air heat exchanger.

The separate components of the air guide must be precisely manufactured, i.e. with small tolerances, to enable subsequent assembly of the air guide. Also, different types of fans require different types of air guides. As an example, to enable provision of air guides of different sizes, a specific set-up of components for each size is required. The previous factors contribute to a higher air guide cost.

Fan air guides with twisted vanes are known from for example <CIT> and <CIT>. Neither one of these have vanes which are twisted during the manufacturing in order to adjust their lengths and the vanes are also not configured therefore.

An object of the present invention is to provide and manufacture a rigid fan air guide which is less expensive than known fan air guides. This object is achieved by the invention set out in the appended set of claims.

The invention will now be described in more detail with reference to the appended schematic drawings, in which.

With reference to <FIG> an air heat exchanger <NUM> is illustrated. The air heat exchanger <NUM> comprises a fan (not visible), a fan guard <NUM> and a fan air guide <NUM>. The fan guard <NUM> is connected to the fan air guide <NUM> at connection tabs <NUM> thereof (visible especially in <FIG>). Further, the fan air guide <NUM> is at connection recesses <NUM> connected to a body <NUM> of air heat exchanger <NUM> by means of screws, nuts and washers (see <FIG> & <FIG>). The connection between the fan air guide and the other components of the air heat exchanger will not be further discussed herein.

The fan is arranged to draw outside air through the air heat exchanger <NUM>, as is illustrated by the arrows in <FIG>. A brief description of an air heat exchanger was given by way of introduction, and since the present invention is not focused on the air heat exchanger <NUM> itself, it will not be described in further detail herein.

The fan air guide <NUM> is further illustrated in <FIG>. It comprises a circular stainless steel frame <NUM> and a hub in the form of a circular stainless steel plate <NUM> arranged inside the frame <NUM> and concentrically therewith. The fan air guide <NUM> further comprises a plurality of similar vanes <NUM> extending radially from the frame <NUM> to the plate <NUM>. A first one of these vanes <NUM>, denoted <NUM>', is illustrated in further detail in <FIG> and further described below. However, the description of the first vane <NUM>' is valid for all the vanes <NUM>.

The first vane <NUM>' is elongated and it extends along a longitudinal axis A. The first vane <NUM>' is made of sheet stainless steel and it comprises a first end part <NUM>, a second end part <NUM> and a tapered intermediate part <NUM> extending between the first and second end parts <NUM> and <NUM>. The transitions between these parts are illustrated by the dashed lines B1 and B2. In turn, the first end part <NUM> comprises a first portion <NUM> and a second portion <NUM> and the second end part <NUM> comprises a first portion <NUM> and a second portion <NUM>. The transition between these portions are illustrated by the point-dashed lines B3 and B4. The second portion <NUM> of the first end part <NUM> is provided with a mounting hole <NUM> arranged centrered with respect to the longitudinal axis A. The second portion <NUM> of the second end part <NUM> is provided with two mounting holes <NUM> and <NUM> symmetrically arranged at opposite sides of the longitudinal axis A. Further, the intermediate part <NUM> of the first vane <NUM>' is provided with a deformation hole <NUM> arranged close to the transition to the first end part <NUM> and centrered with respect to the longitudinal axis A. Similarly, the intermediate part <NUM> is provided with a deformation hole <NUM> arranged close to the transition to the second end part <NUM> and centrered with respect to the longitudinal axis A. The mounting and deformation holes will be further discussed below.

With reference to the figures, the frame <NUM> is at an underside thereof provided with an outwards extending brim <NUM>, which in turn is provided with a mounting hole <NUM> (<FIG>) for each of the vanes <NUM>. Further, an edge portion of the plate <NUM> is provided with a corresponding pair of mounting holes <NUM> and <NUM> (<FIG>) for each of the vanes <NUM>. The first vane <NUM>' (<FIG>) is mounted inside the frame <NUM> such that the second portion <NUM> of the first end part <NUM> engages with an underside of the brim <NUM> by means of a rivet <NUM> (<FIG>, <FIG> & <FIG>) extending through the mounting hole <NUM> of the first vane <NUM>' and one of the mounting holes <NUM> of the brim <NUM>. Further, the second portion <NUM> of the second end part <NUM> engages with an underside of the plate <NUM> by means of two rivets <NUM> and <NUM> (<FIG> & <FIG>) extending through the mounting holes <NUM> and <NUM>, respectively, of the first vane <NUM>' (<FIG>) and the corresponding ones of the mounting holes <NUM> and <NUM> (<FIG>), respectively, of the plate <NUM>. <FIG> illustrates what the first vane <NUM>' looks like in an undeformed state. The first vane' <NUM> is mounted inside the frame <NUM> in this undeformed state.

Thus, when the fan air guide <NUM> is to be manufactured, the frame <NUM> is first provided, Step A, and then the plate <NUM> is provided inside the frame <NUM>, Step B. Each of the vanes <NUM> is then attached to the frame <NUM> (Step C) and the plate <NUM> (Step D) in the above described manner. <FIG> illustrate what the fan air guide <NUM> looks like after Steps A-D have been performed. Thereafter, each of the vanes <NUM> is twisted, as seen from the upperside of the plate <NUM>, clock-wise around its longitudinal axis A. This twisting results in deformation of the vanes <NUM>, i.e. twisting of their respective first portions <NUM> of the first end parts <NUM> (Step E), and simultaneous twisting of their respective first portions <NUM> of the second end parts <NUM> (Step F). After this twisting of the vanes <NUM>, they will each comprise two first portions <NUM> and <NUM> which are twisted, in relation to the intermediate part <NUM> between the first portions <NUM> and <NUM>, around the respective longitudinal axis A of the vanes. In other words, after the twisting, the first portions <NUM> and <NUM> of the vanes will each be, at least partly, essentially helix shaped, the first portions <NUM> and the first portions <NUM> having opposite twisting directions as seen from the intermediate parts <NUM>. <FIG>, <FIG> and <FIG> illustrate the finished fan air guide <NUM>, i.e. what the fan air guide looks like after Steps A-F have been performed.

With reference to <FIG>, the above mentioned deformation holes <NUM> and <NUM> in the intermediate part <NUM> of the vanes <NUM> are provided to guide vane material towards the deformation zones, i.e. the first portions <NUM> and <NUM> of the vanes <NUM>, in connection with vane twisting, such that the vane material required for "proper" (see below for explanation) deformation is available. Thereby, breakage of the vanes in connection with vane twisting may be avoided. The deformation holes <NUM> and <NUM> may also be of use in connection with twisting of the vanes. As an example, a screwdriver may be inserted in any of the deformation holes and rotated for vane twisting.

With reference to <FIG>, the undeformed first vane <NUM>' has a total length L, the first end part <NUM> has a length L1, the second end part <NUM> has a length L2 and the intermediate part <NUM> has a length L3. Clearly, L3 >> L1, L2 so as to optimize the capacity of the fan air guide since the intermediate part, much more than the first and second end part, is behind the desired function of the fan air guide, which is to increase the air throwing distance of the fan. When the first portions <NUM> and <NUM> of the first vane <NUM>' are twisted, they get shorter which means that L1 and L2 vary with vane twisting. The intermediate part <NUM> of the first vane <NUM>' is not twisted and its length L3 does not vary with vane twisting but is constant. In this specific example, before deformation of the first vane <NUM>', L = <NUM>,<NUM>, L3 = <NUM>,<NUM>, L2 = <NUM>,<NUM> and L1 = <NUM>,<NUM>. These values can, however, be varied in an endless number of ways.

Thus, when the vanes <NUM> are "properly" deformed in the above described way, their length is reduced and adjustment of the vane length to a distance d (<FIG>) between the frame <NUM> and the plate <NUM> is enabled. In this specific example, d = <NUM>,<NUM>, a diameter of the plate <NUM> is <NUM>, a maximum outer diameter (at the brim <NUM>) of the frame <NUM> is <NUM>,<NUM> and an inner diameter of the frame is <NUM>,<NUM>. Thess values can, however, be varied in an endless number of ways. By twisting of the vanes, the vanes are firmly spanned between the frame and the plate which makes the resulting fan air guide rigid and strong, despite of the fact that the vanes are made of sheet metal, here sheet stainless steel. Typically, the more the vanes are twisted, the shorter, and thus more tensioned, they get. Naturally, this is true for "proper" deformation, i.e. up to a certain point beyond which further vane twisting causes the vane to "collapse". Then, further twisting will not result in increased vane tension but perhaps instead decreased vane tension and/or even vane breakage.

From the above follows that the degree of twisting of the vanes of the finished fan air guide is dependent upon the measures of the different components of the fan air guide and the desired final rigidity of the fan air guide. Thus, for example, the first and/or second portions of the vanes may be twisted between a tenth of a revolution and a quarter of a revolution, or less or more than that.

By a suitable twisting of the vanes, a desired vane orientation adapted to the specific application of the fan air guide may also be obtained, which is another advantage of the present invention.

With reference again to <FIG>, different sections of the first vane <NUM>' have different widths, the widths being measured transverse to the longitudinal axis A of the first vane. More particularly, the first portion <NUM> of the first end part <NUM> of the first vane <NUM>' has a smallest width W1 that is smaller than a smallest width W2 of the second portion <NUM> of the first end part of the first vane, i.e. W1 < W2. Similarly, the first portion <NUM> of the second end part <NUM> of the first vane <NUM>' has a smallest width W3 that is smaller than a smallest width W4 of the second portion <NUM> of the second end part of the first vane, i.e. W3 < W4. Thus, the first vane <NUM>' is locally wider where it is arranged be attached to the frame <NUM> and the plate <NUM> which provides for a more safe engagement between the first vane and the frame and the plate, respectively. Further, the intermediate part <NUM> of the first vane <NUM>' has a smallest width W5 (which in this specific non-limiting example happens to be approximately equal to W4) that is larger than the smallest widths of the first and second end parts, respectively, of the first vane, i.e. W5 > W1, W3. A more narrow vane section is more prone to twisting than a wider section. Thus, the twisting of the first vane <NUM>' in connection with vane twisting will occur within the first portions <NUM> and <NUM> of the vane, as is desired. In this specific example, before deformation of the first vane <NUM>', W1 & W3 = <NUM>,<NUM> and W2 & W4 & W5 = <NUM>,<NUM>. These values can, however, be varied in an endless number of ways.

As an example, the frame and/or plate need not be circular but may have other forms, for example an oval or polygonal form. Further, the hub need not be centred within the frame. In connection with such alternative embodiments, fan air guide design adjustments are required. As an example, vanes of different lengths and/or shapes are required.

In the fan air guide above, the hub consists of an element in the form of a plate. Differently designed hubs are naturally possible. As an example, <FIG> illustrates an alternative fan air guide <NUM> according to the present invention. Largely, the construction of the fan air guide <NUM> is similar to the construction of the fan air guide <NUM>. However, the fan air guide <NUM> does not comprise a hub in the form of a plate <NUM>. Further, the fan air guide <NUM> comprises vanes <NUM> meeting in a center of the frame. The vanes <NUM> are connected by a bolt, nut and washer, jointly denoted <NUM>. Naturally, other means for connecting the vanes are possible. Also, embodiments according to which the vanes themselves provides for their mutual connection, i.e. according to which no separate means for connecting vanes is necessary, are conceivable.

The vanes of the fan air guide above all have deformed, i.e. helix shaped, first end parts and second end parts. According to an alternative embodiment, all or some of the vanes could have deformed first end parts only, or deformed second end parts only.

The vanes of the fan air guide above are twisted clock-wise, as seen from the upperside of the plate <NUM>, to cause deformation of the first and second end parts of the vanes. Naturally, the vanes could instead be twisted counterclockwise to cause the deformation.

In the above described embodiment, the first and second end parts of the vanes are firmly attached to the frame and the plate, respectively, before the vanes are twisted. Moreover, the first portions <NUM> and the first portions <NUM> of the vanes need not have opposite twisting directions, as seen from the intermediate parts <NUM>, like above, but may instead have the same twisting direction. The first portions <NUM> and/or the first portions <NUM> of the vanes may be twisted along their complete, or just a part of their, extension.

The vanes need not be made of sheet stainless steel but may be made of other sheet metals or even non-metals. Further, the vanes need not have the shape illustrated in <FIG>. Rather, the shape of the vanes may be varied in numerous ways. Not all vanes need to be similar.

The vanes need not engage with the underside of a brim of the frame and the underside of the plate, like above. In particular, the vanes engage with an inside of the frame and periphery of the plate. As another example, the vanes could extend through apertures in the frame so as to engage with an outside of the frame. Thus, the vanes need not be provided with mounting holes for engagement with the frame and the plate but could be provided with other engagement means.

Other components than rivets could be used to secure the engagement between the vanes and the frame, and the vanes and the plate, e.g. screws and nuts, pins, hooks, etc..

For the above described vanes, the longitudinal axes for the first and second portions of the first and second end parts and the intermediate part coincide and equals the longitudinal axis A. Naturally, the longitudinal axes of the different parts and portions of the vanes need not coincide.

The above described fan air guide comprises an even number of vanes and the vanes are arranged in pairs. The vanes of each pair extend in parallel in opposite directions from the plate, i.e. diametrically across the frame. The fan air guide need not be constructed like this. For example, it may comprise an uneven number of vanes.

It should be stressed that the attributes first, second, etc. is used herein just to distinguish between species of the same kind and not to express any kind of mutual order between the species.

Claim 1:
A method for manufacturing a fan air guide (<NUM>, <NUM>) comprising:
(Steps A, B) providing a frame (<NUM>), a hub (<NUM>, <NUM>) and a plurality of vanes (<NUM>, <NUM>),
(Steps C, D) attaching the plurality of vanes (<NUM>, <NUM>) to the frame and/or the hub such that each of the vanes extends from the hub (<NUM>) inside the frame to the frame, each of the vanes comprising a first end part (<NUM>), a second end part (<NUM>) and an intermediate part (<NUM>) extending between the first and second end parts,
(Steps E, F) twisting a first portion (<NUM>) of the first end part (<NUM>) of at least a first vane (<NUM>') of the vanes around its longitudinal axis (A) in relation to the intermediate part (<NUM>) of the first vane and/or twisting a first portion (<NUM>) of the second end part (<NUM>) of the first vane (<NUM>') around said longitudinal axis (A) in relation to the intermediate part (<NUM>) so as to adjust a length (L) of the first vane to the dimensions of the other components of the fan air guide and to a distance (d) between the frame and the hub in particular, and if not yet done, attaching the plurality of vanes (<NUM>, <NUM>) to the frame and the hub.