An axial fan and methods of manufacturing axial fan blades and assembling the fan
Patent Information
- Application Number
- EP2023793852
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-10-21
- Filing Date
- 2023-10-20
- Publication Date
- 2025-08-27
AI Technical Summary
Existing axial fan designs face inefficiencies due to large base parts required for strong connections between impeller blade elements and hubs, leading to increased weight, reduced aerodynamic performance, and costly quality control measures such as non-destructive testing to ensure proper alignment and connection strength.
The axial fan features a fan blade with an integrally formed impeller blade element and base, including a single threaded bolt for secure attachment to the hub, and a shaped profile for form locking orientation, potentially manufactured through additive manufacturing or investment casting, ensuring a strong and aerodynamically efficient connection without the need for extensive base material.
This design minimizes the base size, enhances aerodynamic performance, reduces production costs by eliminating the need for extensive testing, and ensures accurate blade orientation and secure attachment, thereby improving efficiency and reducing assembly time and costs.
Smart Images
Figure 1.1
Abstract
Description
[0001] An axial fan and methods of manufacturing axial fan blades and assembling the fan
[0002] The present invention relates to axial fans and methods of manufacturing the individual fan blades and assembling the blades onto a fan hub. An axial fan has a rotatable hub adapted to be connected to a drive source such as an electric motor and a plurality of fan blades disposed about the axis of the hub and extending in a generally radial direction from the hub. Blades typically consist of an impeller blade element mounted on a base which is connected to the hub.
[0003] In the interests of improving the efficiency of the fan blade and its cost, it is desirable to keep the base part of the fan blade as small as possible so as not to impede the airflow. It is known for the impeller blade elements to be bolted on a base which is itself connected to the hub. An alternative form of connection is known, for example, as shown in US 2011 / 031 1365 A1 , formed of two parts in which the blade impeller elements are formed of a cast metal and a fastening device is cast in with the impeller element. A threaded part of the fastening device extends from the radially inner end of the impeller element so as to be bolted to the hub directly or indirectly. In order to ensure a good connection between the impeller element and the fastening device it is necessary for the part of the fastening device cast into the impeller element to have a varied shape to provide a large surface area to ensure a good strong connection in the casting between the fastening device and the impeller blade element. This arrangement has the disadvantage that the base of the blade impeller element must be substantially larger than the main part of the impeller blade to provide the necessary strength to the connection. A further disadvantage is that for each blade in a fan the quality of the connection between the two parts must be checked, preferably by a non-destructive test, such as X-rays. Any which do not meet an acceptable standard have to be scrapped and replaced. This slows down production and increases cost.
[0004] The present invention seeks to provide an axial fan which overcomes the shortcomings of the known devices.
[0005] According to the present invention there is provided a fan blade for an axial fan, the blade having an impeller blade element and, formed integrally therewith a blade base adapted to be secured onto a fan hub, the fan hub being adapted to be connected to a fan drive motor, wherein the blade base has formed integrally therewith a single threaded bolt by which the fan blade is securable by a single nut to the fan hub,, and wherein the blade base has a shaped profile adapted to interengage in a form locking manner with a shaped profile on the fan hub to ensure that the fan blade is located in the correct orientation relative to the fan hub
[0006] In a preferred embodiment of a fan blade according to the invention, the shaped profile on the blade base comprises a projection adapted to interengage with a correspondingly shaped profile formed in a recess in the fan hub. In another form, the shaped profile on the blade comprises a recess adapted to interengage with a correspondingly shaped profile formed on a projection on the fan hub.
[0007] Preferably, the fan blade is formed by an additive manufacturing process, or by an investment casting process.
[0008] The fan blade may be formed of steel, a metal alloy or a plastics material.
[0009] Preferred embodiments of the present invention will now be described by way of example with reference to the accompanying drawings in which
[0010] Figure 1 shows a cross-section through a fan blade according to the present invention,
[0011] Figure 2 shows a cross-section through an alternative construction of fan blade not in accordance with the present invention,
[0012] Figure 3 shows a fan blade according to the present invention,
[0013] Referring to Figure 2 there is shown schematically an example similar to the construction shown in US 2011 / 0311365 and not in accordance with the claimed invention, in which a fan blade 20 has a substantial base 22 containing a threaded bore 24 in which a threaded stud 26 is screwed, which then extends through the fan hub 28. A nut 30 engages the stud 26 and is tightened to secure the fan blade to the fan hub 28. This design has the disadvantage that the base 22 must be substantial to give sufficient strength to the connection between the stud and the fan blade which increases the weight of the blade and reduces the aerodynamic area of the fan blade.
[0014] Referring now to Figures 1 and 3, there is shown schematically in Figure 1 a cross-section through a fan blade 1 of an axial fan, the fan blade 1 being secured to a fan hub 2 which is adapted to be rotated by a fan motor (not shown) and is rotatable about a fan axis 3. The fan blade 1 consists of an elongate impeller element 4 which is formed integrally with a base 5 by which the impeller element 4 is connected to the fan hub 2 so as to extend outwardly radially on an axis normal to the fan axis 3. At its radially innermost end the impeller element 4 merges into an enlarged zone 6 which comprises part of the base 5. The enlarged zone 6 is located in a recess 7 in the fan hub 2. The base 5 has a spigot 8 which consists of a cylindrical part 9 by which the fan blade 1 is located in a bore 2a in the fan hub 2. The cylindrical part 9 terminates in a screw thread 10 through which the fan blade 1 is secured to the fan hub 2 by a bolt 11 with an intermediary washer 12. The spigot 8, the cylindrical part 9 and the screw thread 10 are substantially aligned with the axis of the impeller element 4.
[0015] The fan blade 1 including the impeller element 4, the base 5, spigot 8, cylindrical part 9 and the screw thread 10 are formed integrally in one component formed by an additive manufacturing technique or by investment casting. The material in which the fan blade 1 is formed may be steel, a metal alloy or a plastics material.
[0016] It is necessary for the impeller elements 4 to be accurately located about their axes relative to the fan hub 2 to ensure that the aerodynamic performance of all the impeller elements in the fan is equal. One solution to this problem is to physically check the position of each element 4 as the fan is being assembled, but this is time-consuming and hence expensive. In an alternative solution, according to the invention, the blade base 5 has a shaped profile non-uniform about the blade axis 3 adapted to interengage in a form locking manner with a correspondingly shaped profile in the recess 7 in the fan hub to ensure that the fan blade is located in the correct orientation about its axis relative to the fan hub 2 on assembly. In one alternative form, the shaped profile on the blade base comprises a recess adapted to interengage with a correspondingly shaped projection formed on the fan hub 2.
[0017] In another form, it has been proposed to use a collet or cotter pin arrangement to fasten the fan impeller element to the blade base. Although such arrangements can ensure the correct angular location of the impeller element they do not provide a reliable connection with sufficient axial loading to guarantee overcoming the centrifugal forces generated during operation. Also such a connection has to be tested in the final assembly of the fan, which can increase production and assembly costs.
[0018] RECTIFIED SHEET (RULE 91 ) ISA / EP
Claims
CLAIMS1 . A fan blade for an axial fan, the blade having an impeller blade element and, formed integrally therewith, a blade base adapted to be secured onto a fan hub, the fan hub being adapted to be connected to a fan drive motor, wherein the blade base has formed integrally therewith a single threaded bolt by which the fan blade is securable by a single nut to the fan hub wherein the blade base has a shaped profile adapted to interengage in a form locking manner with a shaped profile on the fan hub to ensure that the fan blade is located in the correct orientation relative to the fan hub.2 A fan blade according to claim 1 , wherein the shaped profile on the blade base comprises a projection adapted to interengage with a correspondingly shaped profile formed in a recess in the fan hub.
3. A fan blade according to claim 1 , wherein the shaped profile on the blade comprises a recess adapted to interengage with a correspondingly shaped profile formed on a projection on the fan hub.
4. A fan blade according to any one of claims 1 to 3, wherein the fan blade is formed by an additive manufacturing process..
5. A fan blade according to any one of claims 1 to 3, wherein the blade is formed by an investment casting process.
6. A fan blade according to any one of claims 1 to 5, wherein the blade is formed of steel, a metal alloy or a plastics material.
7. An axial fan having a plurality of fan blades according to any one of claims 1 to 6, the fan blades being secured to the fan hub equi-distantly about the periphery of the fan hub.