EP3106673B1 - Fan with at least one fan wheel and/or further fan parts and method for producing a fan part of a fan - Google Patents

Description

The invention relates to a fan according to the preamble of claim 1 and a method for producing a fan part of a fan according to the preamble of claim 11 or 14.

The load capacity of injection molded plastic fan parts is limited. In the case of fans in which such parts are used, this leads in particular to a limit speed above which the fan can no longer be operated. In injection molded plastic parts, so-called weld lines are often weak points. A weld line is a flat area within an injection molded part that is created when two separate partial streams of liquid plastic flow together in the mold cavity during the injection molding process. Since the temperature of these partial flows is usually too low, optimal merging of the partial flows is no longer possible, which results in the weld line. Reinforcing fibers contained in the liquid plastic are usually aligned along the weld line, which means that they do not bridge the weld line and consequently do not reinforce it. Weld lines occur in particular when the injection-molded part has a component volume that is not simply connected, for example as a result of bores or a plurality of fan blades which are integrally connected to a hub ring and a cover ring. In addition, weld lines can also occur if plastic is injected at several points in an injection molded part. In order to nevertheless achieve a high resilience in injection-moulded plastic parts with weld lines, various precautions are taken met. For example, more material is used, particularly in the weld line area, or high-strength materials, which, however, increases the manufacturing costs and/or the weight of the fan part, which means that fans can no longer be manufactured economically. In the case of fans, it is also customary to manufacture fan parts that are subjected to particularly high loads from metal. This also leads to additional costs and/or additional weight in the manufacture of the fans.

Fan parts made of plastic injection molding also have strength-critical areas in addition to weld lines. For example, transition points within a component, for example from fan blades to rings, such as hub rings or cover rings, are often critical in terms of strength. Furthermore, connection areas, such as holes for screws, bushings or other inserts or receptacles for shafts or the like, can be places where strength is critical. Fan parts with areas that are critical in terms of strength often cannot be realized in plastic injection moulding, or only by using expensive, high-strength injection molding material or large wall thicknesses.

Fan parts, in particular fan wheels, fan blades, suspensions or adapter hubs, are often also deformation-critical, i.e. a deformation permissible for the perfect operation of a fan is so small that a fan part cannot be realized in plastic injection molding, or only through the use of very expensive injection molding material or very large wall thicknesses.

A method for manufacturing a fan propeller blade is known ( EP 1 704 990 A1 ), in which the propeller blade consists of a lightweight core and a wing wall. The lightweight core is equipped with a ready-made fiber structure. The wing wall is made of fiber-reinforced plastic. The fiber structure is inserted into a tool in a suitable cut and then impregnated with resin by means of an injection process.

It is further known ( JP H05 87095 ) to produce the fan blades of a fan wheel from a base material and a fiber material that essentially consists of carbon fibers. The fiber material is applied to both sides of the base material in such a way that the base material is covered with the fiber material in the upper half on one side and in the lower half on the other side.

The DE 20 2011 052 411 U1 describes an impeller for fans, which has blades, a bottom disk and a cover disk, which are produced as a one-piece injection-molded part made of thermoplastic material. To reinforce the blades, a molding is used consisting of organic sheet, which is a fabric made as an orthotropic fabric or a unidirectional fabric.

Finally it's over EP 0 754 863 A1 known to wrap flow segments of a fan, which are joined to a hub, with a bandage so that the fan wheel is held together mechanically in addition to the adhesive or welded joints between the flow segments.

The invention is based on the object of designing the generic fan and the generic method in such a way that the fan can be manufactured easily, with low component weight and inexpensively with high resilience in terms of component failure and permissible component deformation.

In the case of the generic fan, this object is achieved according to the invention with the characterizing features of claim 1 and in the case of the generic method according to the invention with the characterizing features of claims 11 and 14, respectively.

When the fan according to the invention, reinforcement elements are used in the load-critical or deformation-critical areas are quasi-continuous fiber-reinforced tapes that can be unwound on a spool. The reinforcement tapes can be easily unwound from the spool and cut to the required length. This enables a simple, flexible and economical production method. The reinforcement bands are partially or completely embedded in the thermoplastic material from which a fan wheel, a fan blade or another fan part is made. One or more fan parts of the fan according to the invention can thus be manufactured inexpensively using the injection molding process. The reinforcement bands significantly increase the resilience of at least one fan part, which means that the limit speed at which the fan can be operated can also be greatly increased, or by which wall thickness and thus material use and weight can be saved when designing the fan part, or by which a fan part can be realized is only possible in plastic injection moulding. The high resilience of a fan has the advantage that small, compact fans can be used for a required amount of air, which can be operated at correspondingly higher speeds. The thermoplastic is preferably a fiber-reinforced plastic into which the reinforcing strips are additionally incorporated. The reinforcement strips can be introduced in a fan wheel, a fan blade or in other fan parts in a targeted manner with regard to the position and the direction of action. The reinforcement bands can be positioned and oriented in such a way that they absorb the main loads of the corresponding fan part or avoid or at least reduce deformations in critical directions.

In an advantageous embodiment, the reinforcement band surrounds an inflow opening of a fan wheel in a ring shape at a distance. The reinforcement band ensures that the critical edge area of this inflow opening is adequately reinforced.

In an advantageous embodiment, at least one reinforcement band runs transversely to at least one weld seam of a fan part. Weld lines form stress-critical areas of a fan part, which run through transverse Reinforcing tapes are advantageously reinforced. A reinforcement strip advantageously crosses weld seams, which can be located, for example, on the hub ring and/or cover ring of a fan wheel or on an adapter hub or a hub body.

Depending on the design of the load-critical areas, several reinforcement strips can be provided above and/or next to each other in the fan part. As a result, optimal positioning and thus reinforcement of the fan part in the area of its load-critical areas and/or its deformation-critical areas is easily possible.

A further load-critical area of a fan is, in the case of a fan wheel, the transition from the fan blades to at least one ring manufactured in one piece with the fan blades, such as a hub ring or a cover ring. It is therefore advantageously possible to provide at least one reinforcing band in the area of this transition in such a way that it crosses the transition. A fan wheel can be optimally reinforced in this critical area with the reinforcement band.

In the case of fan wheels, the fan wheels, fan blades or other fan parts are often critical in terms of deformation, ie their deformation, for example their deflection, during operation often reaches critical values for the functioning. This is particularly the case when fan blades, as is often the case, have thin trailing edges that are aimed at with regard to low noise development. If, in a preferred embodiment, the reinforcement band is positioned in the area of the front and/or rear edge of the fan blades, the fan blades can retain the thin rear edge, which is advantageous for acoustic reasons, or can be designed with thin front edges, without excessive deflection or deflection when the impeller is in use To achieve deformations for the fan blades. This training also leads to a considerable saving in material in the production of a fan wheel.

The reinforcement band can extend in the fan blade along the front and/or the rear edge of the fan blade, with the extension length being selected such that the fan blades are optimally reinforced in their critical edge area. The reinforcing band can therefore extend over the entire length in the direction of the span, but also only over part of the length of a fan blade.

In a particularly advantageous embodiment, a plurality of reinforcement strips are distributed over the width of the fan blade, ie in the region between the front and rear edges, which extends from the front edge to the rear edge. This makes it possible to provide the fan blades with a very strong crescent shape. If the reinforcement strips are not used, there is a risk in the case of strongly crescent fan blades, such as those used in axial fan impellers in particular, that they will become severely deformed during use and rub against the wall ring surrounding the impeller. Through the use of the reinforcement strips, a very strong sickling of the fan blade can be used, even with a thin wall thickness of the fan blade and high speeds, without fearing an impermissible deformation of the fan blade. Since the sickle shape is aimed at with regard to optimal acoustic values, the desired low noise level of the fan can be achieved in a very simple and cost-effective manner by using the reinforcement strips.

A fan wheel can be manufactured in one piece as an injection molded part. However, fan wheels are also possible that are made up of individual blades, which each consist of a one-piece fan blade and connection element, which are connected to a hub ring. In this case, the fan blades are each provided with a connecting element, preferably in the form of a blade foot, with which the fan blades are held on the hub ring. Blade feet are advantageously designed in the shape of a spherical cap, so that there is the possibility of rotating the individual blades relative to the hub, at least during assembly, so that the fan blades can be adjusted to the optimum angle of attack.

So that the individual blade in the area of the connection element ensures a high load-bearing capacity, reinforcement strips are advantageously accommodated in the connection element in such a way that they extend over the transition area from the connection element into the fan blade. The critical transition area between the connection element and the fan blade is thus optimally reinforced.

If the fan wheel has a hub ring, then advantageously at least one reinforcing band runs in the hub ring, preferably helically, over the circumference of the hub ring. The hub ring is a highly stressed component because it has to guarantee the power transmission from the fan blades to the motor. In some cases, a hub ring is pressed onto a shaft or other mount, causing significant stress. By using a reinforcement band extending over the circumference, these stresses are absorbed in such a way that the function of the fan impeller is prevented from being impaired. The reinforcement band can be arranged very easily in the injection mold. A helical shape ensures a high load capacity over the entire circumference of the hub ring in a simple manner. Since the reinforcement tape is unwound from the spool, hub rings of different heights can be very easily provided with the helically running reinforcement tape. It is also advantageous to arrange several layers of reinforcing tapes in a helical manner in such a way that the tapes cross one another. As a result, for example, a high torsional rigidity or flexural rigidity of a hub ring can be achieved, depending on the selection of the pitch angle of the helical course.

The helical reinforcing band preferably runs over the entire height of the hub ring.

In an advantageous embodiment with individual wings, the hub ring consists of at least two hub bodies clamped against each other, at least one of which is approximately annular. Such hub bodies are used in particular when individual wings are to be fastened to the hub ring with their connection element designed as a wing root. For this purpose, at least one hub body is provided with recesses on the end face facing another hub body, into which the blade root engages in the assembled state.

So that the hub ring or the hub body has a sufficiently high stability, at least one reinforcement band is advantageously provided near the end face of the approximately ring-shaped hub body, which reinforcement band advantageously extends over the circumference of the hub body. As a result, the hub bodies can be tightly braced against one another with the wing roots of the individual wings being interposed. For example, if the hub is pressed onto a shaft and very high stresses occur, these can be absorbed by using the reinforcement strips, even though the hub or the hub bodies are made of injection-molded plastic. The high operating forces that are introduced into the hub ring via the wing roots and must be absorbed by the hub ring can also be absorbed by using the reinforcement strips. The use of metallic hubs is therefore no longer necessary.

In this case, the reinforcement strips are advantageously provided in the hub bodies in such a way that they also run underneath the depressions in the end face of the hub body, into which the wing roots of the individual wings engage in the assembled state.

Fan wheels, particularly in the area of the hub ring, frequently have fastening openings for the passage of fastening screws, with which the fan wheel can be fastened to a motor or to an adapter. In the area of the fastening holes, weld seams often occur during injection molding, the disadvantageous effects of which are eliminated or significantly reduced by the reinforcing strips. In this case, each fastening opening is advantageously surrounded by at least one reinforcement band.

The use of the reinforcement band allows bushings and the like to be pressed into the fastening holes. The resulting clamping forces are absorbed by the reinforcement band.

In a method according to the invention, a fan wheel, a fan blade or another fan part is produced in one piece by injection molding using a thermoplastic material. For this purpose, the reinforcement strip is inserted and positioned in the injection mold. It is previously unwound from a spool and cut to the correct length. A special pre-shaping or a special cutting of the reinforcing tape is not required. In particular, no preforming tools are required. There is no waste, as is often unavoidable when using flat semi-finished products based on fiber fabric. The reinforcement band is positioned and held in the injection mold using appropriate devices. For example, a reinforcement band can be fixed in the tool with special pins. Then the thermoplastic material is injected into the injection mold, which partially or completely surrounds the pre-positioned reinforcement band. Shortly before the end of the injection process, the pins can be pulled back using hydraulics or pneumatics so that the cavities created by the pins themselves are filled with plastic material.

A particularly advantageous method of positioning the reinforcement bands is to stick them to the mold surface in the cavity of the injection mold using a special adhesive. For example, a thermal adhesive can be used, with which the tapes are already coated on one side on the spool and which develops its adhesive effect only at a specific temperature, as is the case on the injection molding tool. With this method, the reinforcement bands appear visibly on the component surface of a finished fan part, i.e. they are not completely embedded in the surrounding plastic.

In another procedure, an injection molding blank is prefabricated and the reinforcement band or bands are attached to it, for example by gluing or welding. The injection molding blank is then overmoulded with the other thermoplastic material to form the finished injection molded part in such a way that the reinforcement band(s) is (are) completely enclosed.

Depending on the design of the fan part, the corresponding reinforcement strips can be positioned in several positions in the injection mold or on the incomplete injection molding blank. The reinforcement bands are designed to absorb the main loads or prevent deformations in critical directions. The production-related weak points, such as the weld seams mentioned, are also reinforced by an appropriate arrangement of the reinforcement strips. Unnecessary use of relatively heavy, expensive and energy-intensive fibers to produce with an orientation in which no fiber reinforcement is necessary can be avoided in a targeted manner.

In order to determine the correct position and alignment of the reinforcement bands in the injection mold, the positioning of the reinforcement bands in the injection mold is advantageously determined by mold filling simulation and/or stress-deformation simulation. With stress-deformation simulations, expected stresses and deformations can be predicted with the help of a computer program. With mold filling simulations, production-specific properties such as fiber orientation and flow lines can also be predicted with the help of a computer program. Computer programs for stress-strain simulations or mold filling simulations are known and available on the market.

It is also possible to experimentally determine critical areas where reinforcement with reinforcing tapes is necessary. This can be done, for example, by analyzing the fracture behavior of unreinforced or insufficiently reinforced components. A big advantage of The method described here is that, if insufficient reinforcement is identified in an already existing fan part, it is comparatively easy to provide otherwise structurally identical fan parts with additional reinforcement strips. No changes or adjustments to injection molding tools, semi-finished products, stamping tools or preform tools are necessary.

Further features of the invention emerge from the further claims, the description and the drawings.

Fig. 1

in Axialansicht eine erste Ausführungsform eines erfindungsgemäßen Radiallüfterrades,

Fig. 2

in einer Darstellung entsprechend Fig. 1 eine zweite Ausführungsform eines erfindungsgemäßen Radiallüfterrades,

Fig. 3

in perspektivischer Darstellung einen Teil eines erfindungsgemäßen Radiallüfterrades,

Fig. 4

in perspektivischer Darstellung ein erfindungsgemäßes Axiallüfterrad,

Fig. 5

in perspektivischer Darstellung eine weitere Ausführungsform eines erfindungsgemäßen Radiallüfterrades,

Fig. 6

in Axialansicht eine weitere Ausführungsform eines erfindungsgemäßen Axiallüfterrades,

Fig. 7 in

schematischer Darstellung einen Flügel eines Axiallüfterrades mit gesichelten Lüfterflügeln,

Fig. 8

einen Einzelflügel eines erfindungsgemäßen Axiallüfterrades,

Fig. 9 in

Axialansicht eine weitere Ausführungsform eines erfindungsgemäßen Axiallüfterrades,

Fig. 10

das Axiallüfterrad gemäß Fig. 9 in perspektivischer Darstellung,

Fig. 11 in

perspektivischer Darstellung einen Nabenkörper eines erfindungsgemäßen Axiallüfterrads,

Fig. 12

einen Ausschnitt aus einem erfindungsgemäßen Lüfterrad,

Fig. 13 in

Ansicht eine Adapternabe eines erfindungsgemäßen Lüfters,

Fig. 14

in vergrößerter Darstellung einen Schnitt durch ein mit Endlosfasern verstärktes Lüfterteil eines erfindungsgemäßen Lüfters,

Fig. 15

einen Schnitt durch einen Lüfterflügel eines erfindungsgemäßen Lüfters in einer Ausbildung beispielsweise entsprechend den Fig. 5 oder 6,

Fig. 16

in einer Darstellung entsprechend Fig. 13 eine weitere Ausbildung einer Adapternabe eines erfindungsgemäßen Lüfters,

Fig. 17

in perspektivischer Darstellung ein weiteres Lüfterrad eines erfindungsgemäßen Lüfters, welches ein Nachleitrad ist.

The invention is explained in more detail with reference to some embodiments shown in the drawings. Show it

1

in an axial view a first embodiment of a radial fan wheel according to the invention,

2

in a representation accordingly 1 a second embodiment of a radial fan wheel according to the invention,

3

a perspective view of part of a radial fan wheel according to the invention,

4

a perspective view of an axial fan wheel according to the invention,

figure 5

a perspective view of a further embodiment of a radial fan wheel according to the invention,

6

in an axial view a further embodiment of an axial fan wheel according to the invention,

7 in

schematic representation of a blade of an axial fan wheel with sickled fan blades,

8

an individual blade of an axial fan wheel according to the invention,

9 in

Axial view of a further embodiment of an axial fan wheel according to the invention,

10

the axial fan according to 9 in perspective view,

11 in

perspective view of a hub body of an axial fan wheel according to the invention,

12

a section of a fan wheel according to the invention,

13 in

View of an adapter hub of a fan according to the invention,

14

in an enlarged representation a section through a fan part of a fan according to the invention reinforced with endless fibers,

15

a section through a fan blade of a fan according to the invention in a training example according to the figure 5 or 6 ,

16

in a representation accordingly 13 a further embodiment of an adapter hub of a fan according to the invention,

17

a perspective view of another fan wheel of a fan according to the invention, which is a guide wheel.

In the following, various parts of fans made of plastic using the injection molding process are described, which are provided with continuous fiber-reinforced thermoplastic strips in critical areas. Such fan parts can be in particular fan wheels or fan blades, but also other loaded fan parts such as suspensions, wall rings, adapter hubs or hub bodies. Fan wheels can be axial, radial or diagonal fan wheels that rotate during operation, or upstream or downstream guide wheels that are stationary during operation.

The thermoplastic strips are embedded in the injection molding material of the fan parts in a targeted manner with regard to the installation point and the direction of action, so that these thermoplastic strips absorb the main loads on the component or ensure that deformation of these components in critical directions is avoided in a targeted manner. The injection molding material preferably consists of a thermoplastic polymer such as polyamide (PA6, PA66, PA66/6, PAPA, PPA, PA 4.6, PA12), polyester (PBT, PET), polypropylene (PP), PPS, PES, PESU, PEEK , ABS, PC, ASA or the like, which is preferably reinforced with short or long fibers such as glass, carbon, aramid or natural fibers. The placement and alignment of the thermoplastic strips can, for example, be based on stress-deformation simulations of the expected stresses and deformations and/or based on mold filling simulations, with which production-specific properties such as fiber orientation and weld line courses can be simulated.

The thermoplastic strips form reinforcement strips which, in the unprocessed state, advantageously consist of quasi-endless fibers which are embedded in a matrix material. The fibers can in particular be glass, carbon, aramid or natural fibers. The matrix material can in particular be a thermoplastic such as polyamide (PA6, PA66, PA66/6, PAPA, PPA, PA 4.6, PA12), polyester (PBT, PET), polypropylene (PP), PPS, PES, PESU, PEEK, ABS, PC, ASA and the like. A polyamide, a polypropylene or a polyester is preferably used as the material for the tapes. Preferably, the matrix material of the ribbons is the same as or similar to the polymer of the injection molding material. The orientation of the quasi-continuous fibers in such tapes is parallel to the extension of the thermoplastic tapes and unidirectional. This enables the fiber reinforcement to be introduced in a very targeted manner, precisely in an orientation in which the reinforcing fibers can absorb critical component stresses and/or reduce critical component deformations. In the initial state, the thermoplastic strips are flexible transversely to their longitudinal extent, so that they can be wound up and unwound from a spool and placed flexibly in relation to the fan part to be manufactured, for example in an injection molding tool or an injection molding blank. Such thermoplastic tapes can be purchased inexpensively on the market in large lengths rolled up on spools by the meter.

1 shows a radial fan wheel with a cover ring 1, which is connected in a known manner by fan blades 2 to a hub ring 3. The shroud 1, the fan blades 2 and the hub ring 3 are integrally formed with each other by injection molding.

In injection molding, weld lines that are sometimes visible occur when two different partial streams of liquid plastic material flow together in the mold cavity during the injection molding process. Such weld lines in cover ring 1 are in 1 indicated by thin dashed lines 4. You affect the strength of the cover ring 1 and ultimately also the fan wheel. The short or long fibers embedded in the material of the cover ring 1 are essentially aligned along the weld lines 4 . Thus, the weld seams 4 often form the weak points of a cover ring 1 or other fan parts.

In the exemplary embodiment, therefore, the reinforcing strips 5, 6 are embedded in the cover ring 1, the positions of which are indicated by thick dashed lines. They extend over the circumference of the cover ring 1 and are approximately parallel to each other. The reinforcement strips 5, 6 are each at a distance from the outer edge 7 and from the inner edge 8 of the cover ring 1. The reinforcement strips 5, 6 are wholly or partially embedded in the material of the cover ring 1, ie they are in the injection molding process an area within the cavity of the associated injection mold and are firmly and inextricably connected to the surrounding plastic after the injection molding process, but can be visible on the surface of the finished fan part depending on the placement in the component. The reinforcement strips 5, 6 run transversely to the weld seams 4, which they, according to the axial direction 1 seen, cross. Since the reinforcement bands 5, 6 run over the circumference of the cover ring 1, it is ensured that the reinforcement bands 5, 6 cross the weld seams 4 independently of the number and/or position of the weld seams 4.

In the unprocessed state, the reinforcing strips 5, 6 advantageously consist of quasi-endless fibers that are embedded in a matrix material. In the course of the injection molding process, these reinforcement bands are fully or partially embedded in the injection molded part.

Due to the reinforcement strips 5, 6, the cover ring 1 has a high level of strength despite the weld seams 4 that are present. The radial fan wheel can therefore also be used at very high speeds, even with relatively small wall thicknesses of the cover ring 1.

While in the embodiment according to 1 the position of the weld seams 4 over the circumference of the cover ring 1 does not have to be known, because the reinforcement strips 5, 6 run over the entire circumference of the cover ring 1, in the embodiment according to FIG 2 intended to provide the reinforcement strips 5, 6 only in the areas where the weld seams 4 are located. It is generally known to the person skilled in the art where the weld lines are formed in the cover ring 1 when the fan wheel is cast. In addition, the course of the injection molding of the impeller can be simulated by means of a mold filling simulation, with the resultant weld lines 4 being able to be specified with regard to their position on the cover ring 1. The course of weld lines can also be determined using sample fan wheels, which are manufactured without reinforcement strips. It is then possible to place the short reinforcement bands 5, 6 in the injection mold in a targeted manner to be arranged where the weld lines 4 occur on the cover ring 1. The length of the short reinforcement strips 5, 6 is matched to the weld seams 4 in such a way that the desired reinforcement is achieved.

3 shows another critical point on a fan wheel on a section of a radial fan wheel. This is the transition between tween a fan blade 2 and a cover ring 1 of a radial fan wheel. Such transitions 9 can be strength-critical points. For this reason, this transitional area 9 is reinforced by the reinforcement strips 5 . They extend transversely to the transition area 9 and are partly or completely embedded in the fan blades 2 or the cover ring 1 . The reinforcement bands 5 can be located on the surface of the fan blades 2 or the cover ring 1 . With the help of stress-deformation simulations or fracture patterns of non-reinforced fan wheels, the locations and with stress-deformation simulations the length of the reinforcement strips 5 can be determined so that they sufficiently reinforce these transition areas 9, which are critical in terms of strength. The reinforcement strips 5 are placed over the length of the transition areas 9 in such a way that the critical transition area 9 is reliably reinforced over its length.

A transition area 9 that is critical in terms of strength can also exist between the fan blades 2 and the other hub ring 3 . This applies to fan wheels of radial, diagonal or axial design as well as to inlet and outlet guide wheels of fans (stators). For this reason, the reinforcement strips 5 are also provided at the required locations in these transition areas.

Correspondingly for axial fans 4 these transitions 9, which are critical for strength, are provided at the transition from the fan blades 2 to a hub ring 3. The fan blades 2 protrude here approximately radially from the outer wall of the hub ring 3, which is cylindrical and has inwardly projecting eyes 11 on its inside, which have at least one passage opening 12 for fastening screws. The transition point 9 runs on the outside of the hub ring 10 with a gradient. The reinforcement strips 5 in turn extend transversely, preferably perpendicularly, to the transition point 9. The placement of the reinforcement strips 5 and also their length are perfectly determined by a stress-deformation simulation, so that the axial fan wheel has the desired strength in use.

Several or also a large number of reinforcing strips 5 can be provided per transition 9, depending on the desired requirements for the respective fan wheel. In the 3 and 4 a gain band 5 is shown only schematically for each transition 9 .

figure 5 shows a radial fan wheel with the two rings 1, 3, between which the fan blades 2 extend, which are formed in one piece with the two rings 1, 3. In the case of fan blades, the leading and trailing edges 13, 14 are often critical for deformation. In use, their deflection can often reach critical values for the functionality of the fan wheel. However, for acoustic reasons, the trailing edges 14 in particular should be as thin as possible. With the help of the reinforcement strips, this requirement can be met without the deflection of the fan blades reaching critical values when the fan wheel is in operation. At least the trailing edges 14 of the fan blades 2 are reinforced by the reinforcing strips 5 . They advantageously extend over the entire length of the trailing edge 14. As in the previous embodiments, the reinforcement strips 5 are partially or completely embedded in the material of the fan blade 2. The reinforcing bands 5 are provided along the trailing edge 14 such that they are slightly spaced from the trailing edge.

A reinforcement band 5 can also be provided on the front edge 13 . In this case too, the reinforcing strip 5 is partly or completely embedded in the material of the fan blade 2 . The reinforcement band 5 advantageously extends over the entire length of the front edge 13.

It is also possible to provide the reinforcement strips 5 on the front edge 13 and on the rear edge 14 of the fan blade 2 if this should be necessary for reasons of strength or loading. It is also conceivable to provide strips in central areas over the entire width of a fan blade between its leading edge 13 and trailing edge 14, which extend in the direction of the span, i.e. transversely to the hub or cover ring, in order to reduce the deflection of the fan blades.

The length and/or the width of the area in which the reinforcement strips 5 are provided, as well as their orientation, are calculated and determined in advance by stress-deformation simulations. The use of the reinforcement strips 5 makes it possible to design the fan blades 2 to be relatively thin, as a result of which a considerable saving in material is possible. Due to the reinforcement strips 5, the fan blades 2 can be made thinner than the conventional fan blades, which are only provided with the injection-molded short or long fibers. Under certain circumstances, a cheaper and/or lighter plastic can also be used for the injection molding process, for example with a lower fiber content, since the reinforcing strips can relieve the surrounding plastic.

6 shows an axial fan wheel with the hub ring 3 and the fan blades 2 projecting transversely from it. They have the leading edge 13 and the trailing edge 14. The leading edge 13 and the trailing edge 14 have a sickle-shaped course. Such sickled axial fan blades are often very severely deformed in the radial direction during operation. There is a risk that the fan blades 2 touch the wall ring surrounding them. For this reason, the crescent shape is reduced with the conventional fan blades made of injection-moulded plastic, which, however, leads to the fact that the acoustic values are higher.

By using the reinforcement strips 5, it is possible to provide the fan blades 2 with an optimal crescent shape, so that the acoustic values are in the optimal range without the risk of the axial fan blades 2 becoming severely deformed. In particular, the use of the reinforcement strips 5 prevents the fan blades 2 from touching the surrounding wall ring.

The reinforcement bands 5 are positioned inside the fan blades 2 so that the deformation of the fan blades 2 is minimized. In the exemplary embodiment shown, the reinforcement strips 5 extend over the largest part of the spanwise length of the fan blades 2. With the aid of stress-deformation simulations, the position and the number of the reinforcement strips 5 can be determined.

The fan blades 2 can be designed to be wound or have any other shape required for the application. The reinforcement bands 5 ensure that the fan blades cannot become unacceptably deformed during operation. The reinforcement bands 5 are in turn partially or completely embedded in the injection molding material of the fan blades 2 . The length of the individual reinforcement bands 5 within a fan blade 2 and their distance from one another can be determined by stress-deformation simulations.

Based on 7 , which schematically shows an axial view of an axial fan blade, the term sickling of an axial fan blade is to be defined. Through the fan blade 2 15 coaxial cylinder sections are placed to the fan wheel axis. Incomplete cylindrical sections of fan blades should not be considered. A complete cylinder section includes as one continuous surface fan blade portions from leading edge 13 to trailing edge 14. The centerlines 18 of these cylinder sections each have their longitudinal center 19. The particular centerline 18a of the radially outermost complete cylinder section has center 19a. Each center point 19 defines a plane 16 with the fan wheel axis 15, specifically, the center 19a forms the plane 16a with the fan wheel axis. The angle α between the associated plane 16 and the plane 16a is now defined for each radial position. The curve of the angle α defines the crescent shape of an axial fan blade. A wing is said to be strongly sickened when the maximum value of α is greater than 10°, and a very strongly sickened wing when this maximum value is greater than 20°. It is known that a strong crescent is advantageous in particular for low noise emissions from an axial fan.

Based on 8 another critical area of an axial fan wheel is described. It consists of individual wings 2a, which are attached to a hub ring 3. Each individual blade 2a consists of a fan blade 2 and a connection element 20, which is designed as a blade root in the exemplary embodiment, with which it is attached to the hub ring 3 in a known manner. In such individual blades 2a, a critical point is the transition from the connection element 20 to the fan blade 2. This is where the force is introduced from the connection element 20 to the fan blade 2. This area is reinforced with the reinforcement strips 5, as illustrated by the dashed lines.

A connection element 20 designed as a wing root advantageously has a circular outline and is designed approximately in the shape of a mushroom. The reinforcement strips 5 extend from the connection element 20 into the fan blade 2. They run transversely to the transition area 9 between the connection element 20 and the fan blade 2. The distribution and the length of the reinforcement strips 5 can in turn be determined by stress-deformation simulations. The reinforcement strips 5 ensure that high forces can be absorbed in the critical area 9 without having to fear that the individual wing 2a will break off at the transition point 9 . The reinforcement bands 5 are advantageously distributed over the circumference of the connection element 20 designed as a wing root and partially or completely embedded in the material of the individual wing 2a.

Connection elements 20 of an individual wing 2a can also have a different embodiment than that of a wing root. For example, a single wing 2a can be fastened to a correspondingly designed hub ring 3 with a screw. The connection elements 20 then accordingly consist of a corresponding bearing surface on the side of the individual wing 2a, on which the individual wing 2a rests in the assembled state on a counterpart of the hub ring 3, and a through hole for a screw. Such connection elements 20 or their transition 9 to the fan blade 2 are also highly stressed areas and can advantageously be reinforced with reinforcing strips 5, 6. In the case of a connecting element 20 with a through hole, in particular a reinforcement band which surrounds the through hole in the injection molding material can advantageously reinforce the individual wing 2a.

The 9 and 10 show an axial fan wheel in which the hub ring 3 is reinforced with reinforcing strips 5 on the inside of the material. The hub rings 3 are often highly stressed parts during operation because they have to ensure the transmission of power from the motor to the wings 2 . In some cases, the hub rings 3 are also pressed onto a shaft or other mounts, which leads to additional stresses in the hub ring 3 .

These high loads on the hub ring 3 are absorbed in that the reinforcing strip 5 is embedded in the hub ring 3 . In the exemplary embodiment, it runs helically over almost the entire axial height of the hub ring 3. The gradient of the reinforcement band 5 and the height range in which the reinforcement band is located depend on the critical areas within the hub ring 3. The position and course of the helical reinforcement band 5 can in turn be determined by stress-strain simulations. The reinforcement band 5 is partly or completely embedded in the material of the hub ring 3 .

Depending on the load on the hub ring 3, more than just one reinforcement band 5 can also be provided, with these multiple reinforcement bands being arranged in the hub ring 3 in each case running helically. Several layers of helically running reinforcement strips can also be attached in such a way that the reinforcement strips of adjacent layers cross one another. Reinforcing bands 5 can also be placed in the hub ring 3 in an approximately circular manner.

11 shows a hub body 22 of an axial fan wheel made up of individual blades 2a with a connecting element 20 designed as a blade root. Two such hub bodies 22 are firmly connected to one another in mirror images of one another, the individual fan blades 2a according to FIG 7 are braced with their connecting element 20 designed as a wing root. The hub body 22 has depressions 23 distributed over its circumference, each of which accommodates a connecting element 20 of the individual wing 2a.

The hub body 22 has a bottom 24 in which an opening 25 is located centrally. In the mounted state, a shaft protrudes through the opening 25, on which the hub body 22 is fastened. The opening 25 is surrounded by a peripheral ring wall 26 . Along the outer edge of the base 24 runs a peripheral edge 27 which is higher than the annular wall 26 in the axial direction of the hub body 22. In the end face of the annular raised edge 27 the depressions 23 are arranged. In the area between the adjacent depressions 23 are receiving openings 28 for screws, with which the two hub bodies 22 are screwed together with the interposition of the connecting elements 20 designed as wing roots. Very high stresses arise in the hub body 22 as a result of the stressing processes. For this reason, hub bodies made of metallic material are often used. By using the reinforcement strips 5, it is possible to produce the hub body 22 from plastic injection molding despite the high stress. The reinforcement bands 5, 6 run over the circumference of the hub body 22 and are provided in the rim 27 . The two reinforcement strips 5, 6 run near the end face 29 of the edge 27 and are guided around the depressions 23 in such a way that they run at a small distance from the base 30 of the depressions 23. The reinforcement strips 5, 6 are positioned in such a way that they do not come into the area of the receiving openings 28. As in the previous exemplary embodiments, the reinforcing strips 5, 6 are partially or completely embedded in the material of the hub body 22.

In the exemplary embodiment, two reinforcing strips 5, 6 lying approximately parallel to one another are provided. Depending on the loads occurring in the hub body 22, further reinforcement strips can be embedded in the material of the hub body 22 in the required areas. The reinforcement strips 5, 6 are provided in such a way that they can absorb the stresses that occur in the area of the depressions 23. Therefore, if the individual wings 2a are braced with their connection element 20 designed as a wing root in the depressions 23 of the two hub bodies 22, the tensions can be reliably absorbed with the aid of the reinforcement strips 5, 6. The consequence of this is that the hub bodies 22 can no longer be manufactured from a metallic material, but rather as injection-molded plastic parts.

in 11 illustrated embodiment, two identical hub bodies 22 are screwed in mirror image to form a hub ring 3 against each other. In similar embodiments, two or more different hub bodies can also be connected to one another to form a hub ring 3 , so that the connection elements 20 designed as wing roots are clamped in the hub ring 3 . The high component stresses associated with the jamming of the wing roots in one or more of the hub bodies can be absorbed with embedded reinforcement strips.

in 11 illustrated embodiment, the hub ring is mounted on a shaft. Other embodiments can be designed in such a way that they can be attached to the flange of an external rotor motor, for example. With such hub rings, the parts 24, 26 can be completely missing.

12 shows another critical point on a fan wheel. Shown is a section of the area in which the fan wheel is attached to a motor or an adapter, similar to that in 1 Inner area to be seen for fastening the hub ring 3 to a motor or an adapter. For this purpose, fastening holes 31 are provided, which are distributed over the circumference of a central opening 32 in the hub ring 3 . Between the fastening holes 31 and the edge 33 of the opening 32, which in particular assumes the function of centering a motor or an adapter hub, there are narrow areas 34 which represent weak points of the hub ring 3. In addition, weld lines 4 often occur in these narrow areas 34, which lead to a further weakening of the area 34, which is already weak in strength.

For this reason, the fastening holes 31 are reinforced by a reinforcing strip 5 over their circumference. The reinforcement strips 5 are at a distance from the edge of the fastening holes 31 and from the edge 33 of the central opening 32 and, as in the previous exemplary embodiments, are partially or completely embedded in the material of the hub ring 3 . Because of the reinforcement strips 5, bushings or the like can be pressed into the fastening holes 31 without this measure having a negative effect on the strength in the narrow areas 34.

13 shows an adapter hub 35 of a fan, which is also made of plastic injection molding. The adapter hub 35 has the central, central opening 36, which is surrounded by two spaced-apart reinforcement strips 5, 6 in the exemplary embodiment. The reinforcement bands 5, 6 and the edge 37 of the opening 36 are approximately coaxial or concentric with one another. Because of this design, the very high stresses that arise when the adapter hub 35 is pressed onto a shaft or a cone can be absorbed. The reinforcement bands are partially or completely embedded in the adapter hub 35 material. The number and course of the reinforcement bands 5, 6 around the central opening 36 can be optimized by a stress-deformation simulation, so that the reinforcement bands 5, 6 can be arranged in such a way that maximum reinforcement of the adapter hub 35 in the area of the opening 36 is reached.

14 shows an example in cross section of three reinforcement strips 5, 6 arranged one above the other, which are introduced into a component made of plastic of a fan (fan part). They are of the same design in the exemplary embodiment, but can also have a different design depending on the application. The reinforcement bands 5 are completely embedded in the material of the fan part 38 . The reinforcing strips 6 of the same design are only partially embedded in the material of the fan part 38 and are visible on the surface of the finished fan part 38 . The reinforcement strips 5, 6 have the quasi endless fibers 39 which are embedded in the matrix 40. The fibers 39 are aligned unidirectionally and run parallel to one another. The fibers 39 can, in particular, absorb high tensile stresses perpendicular to the plane of the drawing. That is why the reinforcement strips 5, 6 are arranged in the injection-molded component in such a way that the fibers 39 can absorb the corresponding stresses. The exact placement of the reinforcement strips 5, 6 and the position of the fibers 39 can be optimized, for example, by stress-deformation simulations.

15 shows a section through a fan blade 2, as is the case, for example, in the embodiments according to FIGS figure 5 , 6 or 17 can represent. It has the profile of a hydrofoil in cross section and has in the area of the leading edge 13 and in the area of the thin trailing edge 14 respectively a reinforcement band 5 on. In particular, the reinforcement strip 5 in the area of the thin trailing edge 14 leads to a very high load capacity of the fan blade 2.

Depending on the resilience of the fan blade 2 , further reinforcement strips can be embedded in the fan blade 2 in the area between the front edge 13 and the rear edge 14 .

The profile of the fan blade 2 is advantageously designed in such a way that its thickness d increases steadily both from the front edge 13 and from its rear edge 14 . The fan blade 2 has the maximum thickness dmax in a region which is closer to the front edge 13 than to the rear edge 14 .

In order to achieve low acoustic values, the trailing edge 14 of the fan blade 2 according to FIG 15 particularly thin. In order to achieve this, the wing thickness of the already thin wing profile again decreases sharply over the relatively short area shk near the trailing edge. For example, the wing thickness in a region shk, which is less than 10% of the total chord length, can decrease again by 30%-70% towards the trailing edge 14 . With trailing edges tapering in this way, the introduction of one or more reinforcing strips 5 in the direction of the span (transverse to the drawing area) prevents excessive deformation during operation.

16 12 shows the adapter hub 35 with the mounting holes 31 provided near the outer rim 41. FIG. The fastening holes 31 and the central opening 36 are each surrounded by reinforcement bands 5 . The fastening holes 31 are each surrounded by a reinforcement strip 5 and the central opening 36 is surrounded by two reinforcement strips 5, 6, for example. The arrangement and course of the reinforcement bands 5, 6 corresponds to that shown in FIG 13 described embodiment. The reinforcement bands 5 surrounding the attachment openings 31 are corresponding 12 provided and arranged.

The example according to 16 shows that a wide variety of parts of the fan can be reinforced by the reinforcement strips 5, 6 on the fan at the same time.

17 finally shows a fan wheel made of injection-molded plastic reinforced with reinforcement strips, which is an after-guide wheel. For the purposes of the present invention, in addition to impellers of an axial, diagonal or radial design, upstream guide or downstream guide wheels also represent fan wheels. The downstream guide wheel according to FIG 17 consists essentially of fan blades 2, a hub ring 3 and a cover ring 1. In the exemplary embodiment, in addition to aerodynamic functions, the guide vane also has the function of suspending a motor (not shown) with a rotating axial fan wheel (not shown), which, when installed, is supported by the cover ring 1 of the Nachleitrads are surrounded. To fasten the motor, a flange 43 is provided on the hub ring 3, in which bores 31 are also provided for fixing a motor. A further fastening flange 44 with bores 42 is provided on the cover ring 1 for fastening the guide vane to a device wall or the like. The guide wheel must now hold a motor fan wheel in a secure position relative to the device wall and in particular also relative to the cover ring 1 during transport, storage and operation. The blades of a motor fan wheel must not touch the inside wall 45 of the cover ring 1 of the guide wheel. For this reason, only a very small deformation of the flange 43 of the hub ring 3 relative to the cover ring 1 is permissible even under high loads. Thus, the vanes 2 of the guide wheel are only allowed to deform to an extremely small extent. In order to make this possible with a reasonable use of material in a plastic injection molded part, one or more reinforcement strips 5, 6 are introduced in the areas of the front edge 13 and rear edge 14 of the fan blades 2, which are completely or partially embedded in the surrounding plastic. Such reinforcing tapes are advantageously provided on all fan blades 2 of the guide vane. In the exemplary embodiment, these bands also reinforce the transitions 9 between the fan blades 2 and the hub or cover ring 3, 1.

In the embodiment according to 17 the bores 42 are also reinforced with reinforcement strips, similar to the bores 31 in the exemplary embodiment according to FIG 12 . Also in the embodiment according to 17 weld lines and high loads in the areas of the bores 42 are to be expected. In this exemplary embodiment, however, the reinforcing strips 5 are located in the bores 42 on the workpiece surface, ie they are not completely embedded in the surrounding plastic. Before the injection molding process, the reinforcement strips were wound directly onto the pins in the injection mold, which represent the negative parts of the bores, and then overmoulded. Advantageously, the bands are also fixed on the pins, for example with a special adhesive, for example a thermal adhesive.

The various examples show that fan wheels and other fan parts, such as hub bodies, wall rings or suspensions, can be made of injection-moulded, fiber-reinforced plastic with a high level of strength, by additionally embedding the quasi-endless fiber-reinforced strips 5, 6 in whole or in part in the injection-moulded part are. These reinforcement strips 5, 6 are introduced into the component in a targeted manner with regard to their position and in their direction of action in such a way that the desired reinforcement is achieved. The reinforcement bands 5, 6 can be placed in the injection mold itself using appropriate devices before the injection molding process and held in place with suitable devices. If the plastic is introduced into the injection mold, the reinforcing strips are completely or partially encapsulated by the liquid plastic mass.

For example, the reinforcement strips can be held in the injection mold by special pins that are pulled back before the end of the injection molding process in such a way that the areas that were still occupied by the pins at the beginning of the injection molding process are still filled with plastic melt.

Another very advantageous method of placing the reinforcement bands in the injection mold is to attach them to the inner walls of the injection mold in the area of the mold cavity. This can preferably be achieved by gluing, for example with a thermal adhesive, which develops its adhesive effect only at the elevated temperature of the injection mold. With this technique, a reinforcement band may be at least partially visible on the finished workpiece surface.

However, it is also possible to prefabricate an injection molding blank, which does not yet have the entire volume of the finished component, and to attach the reinforcing strip 5, 6 to it, which can be carried out in a simple manner by welding or gluing, for example. This injection molding blank with the attached reinforcement strip is then cast around again in a further injection molding process, so that the injection molding blank is brought to the finished contour.

As explained with reference to the various examples, one or more reinforcement bands can be incorporated in the injection molded part. They are positioned and aligned in such a way that they absorb the main loads of the respective component or specifically avoid deformations in critical directions. Production-related weak points, in particular the weld seams 4, can also be reinforced in a targeted manner by using the reinforcing strips 5.

The positioning and alignment of the reinforcement bands within the injection molded part can be simulated and optimized using stress-deformation simulations with regard to the stresses and deformations to be expected. With mold filling simulations, production-specific properties can be simulated, such as fiber orientation and flow lines.

Mold filling simulation software and stress-strain simulation software are well known and commercially available.

Fan wheels, fan blades, adapter hubs, suspensions or other fan parts can be made entirely of plastic. The impellers can be operated at high limit speeds. Due to the reinforcement bands 5, 6, no expensive material, such as metallic material, has to be used, but the inexpensive plastic can be used for production. Despite the cheaper material, the same or even higher limiting speeds can be achieved than when using metallic material. The deformations in the operating state, for example in the case of strongly sickled axial fans, are significantly reduced. Wall thicknesses and thus the use of injection molding material in the manufacture of fan parts can be reduced.

Claims (15)

1. Fan with at least one fan wheel with fan blades (2), which are connected to one another using at least one ring (1, 3), at least one fan wheel, one fan blade (2) and/or a different fan part (1, 2, 3, 20, 22, 35, 38) having at least one load-critical region, which is reinforced with at least one reinforcing element (5, 6) which is constructed as tape,
   characterized in that the reinforcing element (5, 6) is a tape which can be unwound from a reel and which consists of a thermoplastic matrix, which encloses unidirectional virtually endless fibres, which run parallel to the length of the reinforcing tape, and in that the fan part (1, 2, 3, 20, 22, 35, 38) is a part produced from thermoplastic in an injection moulding method, into which the reinforcing element (5, 6) is partially or completely embedded in the thermoplastic.
2. Fan according to Claim 1,
   characterized in that the reinforcing tape (5, 6) annularly surrounds an inflow or outflow opening of a ring (1, 3) of the fan wheel in a spaced manner, and in that the reinforcing tape (5, 6) preferably runs transversely to at least one weld line (4) of a fan part (1, 2, 3, 20, 22, 35, 38) and crosses the same.
3. Fan according to Claim 1 or 2,
   characterized in that a plurality of reinforcing tapes (5, 6) are arranged above and/or next to one another and/or transversely to one another in the fan part (1, 2, 3, 20, 22, 35, 38).
4. Fan according to one of Claims 1 to 3,
   characterized in that the reinforcing tapes (5, 6) are provided close to the front and/or rear edge (13, 14) of fan blades (2) and preferably extend along the front and/or the rear edge (13, 14) of the fan blades (2).
5. Fan according to one of Claims 1 to 4,
   characterized in that the reinforcing tapes (5, 6) are arranged in a distributed manner in the region of fan blades (2) over the width thereof between front edge (13) and rear edge (14) and in each case extend approximately in the span width direction of the fan blades (2).
6. Fan according to one of Claims 1 to 5,
   characterized in that in the hub ring (3) and/or covering ring (1), at least one reinforcing tape (5) runs preferably helically over the circumference of the hub ring (3) or the covering ring (1).
7. Fan according to one of Claims 1 to 6,
   characterized in that the reinforcing tapes (5, 6) are provided at the transition (9) from a fan blade (2) to at least one ring (1, 3) in such a manner that they cross the transition (9).
8. Fan according to one of Claims 1 to 6,
   characterized in that the fan wheel has individual blades (2a), which in each case consist in one piece of a fan blade (2) and a connecting element (20), which is preferably constructed as a blade base, using which the individual blades (2a) are connected to a hub ring (3), and in that reinforcing tapes (5, 6) are advantageously accommodated in the connecting element (20), which reinforcing tapes preferably extend transversely beyond the transition region (9) between connecting element (20) and fan blade (2) into the fan blade (2).
9. Fan according to Claim 8,
   characterized in that the hub ring (3) consists of at least two hub shells (22) which are clamped against one another, and in that at least one reinforcing tape (5, 6), which extends over the circumference of the hub shell (22), is advantageously provided close to the end face (29) of an annular hub shell (22).
10. Fan according to one of Claims 1 to 9,
    characterized in that at least one reinforcing tape (5, 6) surrounds at least one fastening opening (31, 42) of a fan part (1, 2, 3, 20, 22, 35, 38).
11. Method for producing a fan containing a fan part according to one of Claims 1 to 10, in which a fan wheel, a fan blade (2) or a different fan part (1, 2, 3, 20, 22, 35, 38) is produced in an injection mould,
    characterized in that at least one reinforcing tape (5, 6) is inserted into and positioned in the injection mould, which reinforcing tape has previously been unwound from a reel and cut to the correct length, and in that subsequently the plastic is injected, which partially or completely encloses the reinforcing tape (5, 6).
12. Method according to Claim 11,
    characterized in that, prior to the actual injection moulding process, at least one reinforcing element (5, 6) was fixed securely in place on the internal wall of the mould in the region of the mould cavity of the injection mould, preferably using a thermoplastic adhesive, and is therefore only partially embedded into the enclosing plastic.
13. Method according to Claim 11 or 12,
    characterized in that at least one reinforcing element (5, 6) is fixed securely in place in the cavity of the injection mould by pins, which are withdrawn from the mould cavity prior to the end of the injection moulding process in such a manner that a region, in which they were still located at the start of the injection moulding process, is closed with plastic melt.
14. Method for producing a fan according to one of Claims 1 to 10, in which a fan wheel, a fan blade (2) or a different fan part (1, 2, 3, 20, 22, 35, 38) is produced in an injection mould,
    characterized in that an injection moulding preform is precast and at least one reinforcing tape (5, 6) is fastened to it, preferably by welding or adhesive bonding, which reinforcing band has previously been unwound from a reel and cut, and in that the injection moulding preform is subsequently overmoulded with further thermoplastic in such a manner that the reinforcing tape (5, 6) is partially or completely enclosed.
15. Method according to one of Claims 11 to 14,
    characterized in that the positioning of a reinforcing tape (5, 6) in the injection mould or on the injection moulding preform is undertaken based on a stress-strain simulation and/or a mould filling simulation.

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