WO2012168416A1

WO2012168416A1 - Method, apparatus and system for reducing vibration in a rotary system of a fan

Info

Publication number: WO2012168416A1
Application number: PCT/EP2012/060871
Authority: WO
Inventors: Prof. Dr.-Ing. Norbert SEITZ
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-06-10
Filing date: 2012-06-08
Publication date: 2012-12-13
Anticipated expiration: 2013-12-10

Abstract

A method of reducing vibration in a rotary system of a fan, comprising balancing said rotary system, characterized by providing a rotational element (200) comprising a chamber (210) having a fulcrum on a rotational axis (240) of said rotational element (200), comprising a circumferential balancing area (220) and being partially filled with an amount of a thixotropic balancing substance (230). A corresponding apparatus and system.

Description

Method, Apparatus and System for Reducing Vibration in a Rotary System of a Fan

Field of the Invention

Embodiments of the invention described herein relate generally to reducing vibration, and more particularly to a method, an apparatus and a system for reducing vibration in a rotary system of a fan.

Background of the Invention

A fan is a machine for creating flow within a fluid, for example a gas such as air, comprising a rotating arrangement of blades, for example vanes, acting on the fluid. The blades may rotate when exposed to a flow. Fans produce flows with high volume and low pressure, and compressors produce high pressures at a comparatively low volume.

The fan may be comprised within a housing, for example a case. The housing may direct the flow, increase safety by preventing objects from contacting the blades, or both. The fan may be comprised in a system, for example a ventilation system such as an air-conditioning system, or a working system, for example a vacuum cleaner.

Vibration is a major factor in a fan. Vibration negatively effects durability that is service interval and life time, safety and comfort. With regard to safety, vibration has a direct influence on stability and may cause material fatigue and damage. With regard to comfort, vibration has a direct influence on noise and may increase a level of noise. Moreover, vibration-induced noise may be amplified by the system comprising the fan. For example, ventilation systems often comprise voluminous ducts made of relatively thin sheet metal and, thus, amplify noise. A main source of vibration is a rotary system of the fan, comprising the blade or blades and a motor. The motor may comprise a shaft, a bearing, a rotor or a combination thereof. Vibrations may comprise rotation-speed-dependent vibrations generally originating from the rotary system. Vibrations may damage rolling-element bearings, for example ball bearings or roller bearings, used, for example, as bearings, or seals. In order to reduce vibration, the rotary system may initially be balanced during production of the rotary system by selectively removing material from a rotating element of the rotary system such that its centre of gravity (CofG) is moved to its centre of rotation (CofR), that is fulcrum. Removing material may comprise abrading, for example grinding, material from the rotating element, or drilling a hole into the rotating elements, or a combination thereof. However, the removing step is an additional step in production, requiring time and increasing cost, particularly in large-volume production.

Moreover, owing to wear and tear of the rotary system, or collection of particles, for example dirt, on the blades, vibration in the fan generally increases over time. In more detail, owing to wear and tear of a rotating element, its CofG moves away from the CofR over time causing an imbalance causing vibration.

JP 2005 121166 is directed to a balance weight for a rotating body. The balance weight comprises metallic powder and a one-component curable adhesive having thixotropic property. It appears that the rotating body is adjusted and the adhesive is cured once only.

DE 198 57 646 discloses a method of balancing tires by introducing a balancing substance inside the tire comprises placing a substance with definite properties, shape, geometry and weight inside the tire and moving to the point of imbalance by rotating the tire.

WO 2010/003988 discloses a method for reducing vibration in a rotary system of an aircraft, for example an aeroplane or a rotorcraft, such as a helicopter.

WO 2011/061228 discloses a method of reducing vibration in a rotary system of a watercraft, for example a cargo ship.

WO 2011/061227 discloses a method of reducing vibration in a rotary system of a motor vehicle, for example a car.

WO 2010/029112 discloses a method for reducing vibration in a rotary system of an article processing machine, for example a washing machine.

For these and other reasons, there is a need for the invention as set forth in the following in the embodiments. Summary of the Invention

The invention aims to provide a method, an apparatus and a system for reducing vibration in a rotary system of a fan.

An aspect of the invention is a method of reducing vibration in a rotary

system 120, 130, 140 of a fan 100, comprising balancing said rotary system 120, 130, 140, characterized by providing a rotational element 120, 130, 140, 150; 200 comprising a chamber 210 having a fulcrum on a rotational axis 240 of said rotational element 120, 130, 140, 150; 200, comprising a circumferential balancing area 220 and being partially filled with an amount of a thixotropic balancing substance 230.

An aspect of the invention is a method, further comprising rotating said rotational element 120, 130, 140, 150; 200 about the rotational axis 240, such that said thixotropic balancing substance 230 liquefies and distributes itself along the circumferential balancing area 220, and an imbalance of said rotational element 120, 130, 140, 150; 200 is reduced.

An aspect of the invention is a method, wherein said rotational axis 240 is oriented horizontally; or said rotational axis 240 is oriented vertically.

An aspect of the invention is a method, wherein said rotational element 120, 130, 140, 150; 200 is an original element of said rotary system 120, 130, 140, 150, a replacement element of said rotary system 120, 130, 140, or a supplemental element 150 to said rotary system 120, 130, 140; said rotational element 120 is a hollow shaft or tubular shaft; said rotational element 120 is an articulated shaft, for example a cardan shaft; or a combination thereof.

An aspect of the invention is a method, wherein the supplemental element 150 is disc-shaped; or the supplemental element 150 is ring-shaped.

An aspect of the invention is a method, wherein said rotational element 120, 130, 140, 150 is a shaft 130; said rotational element 120, 130, 140, 150 is a rotor of a motor 120; said rotational element 120, 130, 140, 150 is a blade 140; said rotational element 120, 130, 140, 150 is a bearing; said rotational element 120, 130, 140, 150 is a gear wheel; or a combination thereof.

An aspect of the invention is a method, wherein said chamber 210 is annular or ring-shaped, or cylindrical; said chamber 210 has a cross section being rectangular, square, semicircle-shaped, bell-shaped or circular; said chamber 210 has a diameter of between 0.005 m and 2 m, or between 0.01 m and 1 m, or between 0.02 m and 0.5 m, or between 0.05 m and 0.2 m, or 0.1 m; said chamber 210 has a length of between 0.01 m and 1 m, or between 0.02 m and 0.5 m, or between 0.05 m and 0.2 m, or 0.1 m; or a combination thereof.

An aspect of the invention is a method, wherein said amount of said thixotropic balancing substance 230 is between 0.001 kg and 1000 kg, or between 0.002 kg and 500 kg, or between 0.005 kg and 200 kg, or between 0.01 kg and 100 kg, or between 0.02 kg and 50 kg, or between 0.05 kg and 20 kg, or between 0.1 kg and 10 kg, or between 0.2 kg and 5 kg, or between 0.5 kg and 2 kg, or 1 kg; said chamber 210 is filled with the amount of said thixotropic balancing

substance 230 to between 1 % and 90 %, or between 10 % and 80 %, or between 25 % and 75 %, or 50 %; or a combination thereof.

Another aspect of the invention is an apparatus for reducing vibration in a rotary system 120, 130, 140 of a fan 100, characterized by a rotational element 120, 130, 140, 150; 200 comprising a chamber 210 having a fulcrum on a rotational axis 240 of said rotational element 120, 130, 140, 150; 200, comprising a circumferential balancing area 220 and being partially filled with an amount of a thixotropic balancing substance 230.

Yet another aspect of the invention is a rotary system 120, 130, 140 of a fan 100, for reducing vibration in said rotary system 120, 130, 140, characterized by a rotational element 120, 130, 140, 150; 200 comprising a chamber 210 having a fulcrum on a rotational axis 240 of said rotational element 120, 130, 140, 150; 200, comprising a circumferential balancing area 220 and being partially filled with an amount of a thixotropic balancing substance 230.

Brief Description of the Several Views of the Drawing

While the specification concludes with claims particularly pointing out and distinctly claiming that which is regarded as the invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which are depicted in the appended drawing, in order to illustrate the manner in which embodiments of the invention are obtained. Understanding that the drawing depicts only typical embodiments of the invention, that are not necessarily drawn to scale, and, therefore, are not to be considered limiting of its scope, embodiments will be described and explained with additional specificity and detail through use of the accompanying drawing in which :

Fig. 1 shows a schematic view of a fan, to which the invention may be applied;

Fig. 2 shows, for a preferred embodiment of the invention, a cross-sectional view of the cylindrical chamber at an initial point in time;

Fig. 3 shows, for the preferred embodiment of the invention, a cross-sectional view of the cylindrical chamber at a point in time, when the thixotropic balancing substance is distributed along the circumferential balancing area of the chamber;

Fig. 4 shows a cross-sectional view of a chamber in a rotational element according to yet another embodiment of the invention;

Fig. 5 shows a cross-sectional view of a chamber in a rotational element according to yet another embodiment of the invention;

Fig. 6 shows a cross-sectional view of a chamber in another rotational element according to yet another embodiment of the invention;

Fig. 7 shows a cross-sectional view of another chamber in a rotational element according to yet another embodiment of the invention;

Fig. 8 shows a cross-sectional view of another chamber in a rotational element according to yet another embodiment of the invention;

Fig. 9 shows a cross-sectional view of yet another chamber in a rotational element according to yet another embodiment of the invention;

Fig. 10 shows a cross-sectional view of another chamber in another rotational element according to yet another embodiment of the invention;

Fig. 11 shows a cross-sectional top view of a fan according to an embodiment of the invention under test;

Fig. 12 shows an exemplary representation of deflections of an original standalone fan over time;

Fig. 13 shows an exemplary representation of deflections of a modified standalone fan over time;

Fig. 14 shows a schematic view of a car radiator fan according to an embodiment of the invention under test; Fig. 15 shows a cross-sectional top view of the car radiator fan according to an embodiment of the invention under test;

Fig. 16 shows an exemplary representation of accelerations of the modified car radiator fan over time with supplemental rotational element;

Fig. 17 shows an exemplary representation of accelerations of the modified car radiator fan over time with supplemental rotational element and added imbalance; and

Fig. 18 shows an exemplary representation of accelerations together with a representation of corresponding revolutions of the modified car radiator fan over time with supplemental rotational element comprising an amount of the balancing substance and added imbalance.

Detailed Description of the Invention

In the detailed description of the embodiments, reference is made to the accompanying drawing which forms a part hereof and shows, by way of

illustration, specific embodiments in which the invention may be practiced. In order to show the structures of the embodiments most clearly, the drawing included herein is a diagrammatic representation of inventive articles. Thus, actual appearance of the fabricated structures may appear different while still incorporating essential structures of embodiments. Moreover, the drawing shows only the structures necessary to understand the embodiments. Additional structures known in the art have not been included to maintain clarity of the drawings. It is also to be understood, that features and/or elements depicted herein are illustrated with particular dimensions relative to one another for purposes of simplicity and ease of understanding, and that actual dimensions may differ substantially from that illustrated herein. In the drawing, like numerals describe substantially similar components throughout the several views. The embodiments are intended to describe aspects of the invention in sufficient detail to enable those of skill in the art to practice the invention. Other embodiments may be utilized and structural, logical or electrical changes or combinations thereof may be made without departing from the scope of the invention.

Moreover, it is to be understood, that the various embodiments of the invention, although different, are not necessarily mutually exclusive. For example, a particular element, feature, structure, characteristic, integer or step, or group of elements, features, structures, characteristics, integers or steps described in one embodiment may be included within other embodiments. Furthermore, it is to be understood, that embodiments of the invention may be implemented using different technologies. Also, the term "exemplary" is merely meant as an example, rather than the best or optimal. The detailed description is, therefore, not to be taken in a limiting sense.

Throughout this specification the word„comprise" or variations such as

"comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

In the description and claims, the terms "include", "have", "with" or other variants thereof may be used. It is to be understood, that such terms are intended to be inclusive in a manner similar to the term "comprise".

In the description and claims, the terms "coupled" and "connected", along with derivatives such as "communicatively coupled" may be used. It is to be understood, that these terms are not intended as synonyms for each other.

Rather, in particular embodiments, "connected" may be used to indicate, that two or more elements are in direct physical or electrical contact with each other.

However, "coupled" may also mean that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other.

In the description and claims, terms, such as "upper", "lower", "first", "second", etc., may be only used for descriptive purposes and are not to be construed as limiting. The embodiments of a device or article described herein can be manufactured, used, or shipped in a number of positions and orientations.

Fig. 1 shows a schematic view of a fan 100, to which the invention may be applied. The fan 100 may comprise a housing 110. As indicated in Fig. 1, the housing 110 may be a cage for allowing flow of a fluid, such as air, through the fan 100. The fan 100 comprises a motor 120 for providing rotary energy at a shaft 130. The motor 120 may comprise a stator (not shown) and a rotor (not shown). The motor 120 may typically be powered by electrical energy. However, the motor 120 may be powered by other sources of power, comprising, for example, hydraulic or pneumatic power. The motor 120 may be an internal combustion engine powered by, for example, gas, such as natural gas or bio gas, gasoline or diesel. The fan 100 further comprises a blade 140 or a plurality of blades 140 coupled to the motor 120 for receiving the rotary energy, and aerodynamically formed for creating flow within the fluid. As shown in Fig. 1, three blades 140 form a fan wheel connected to the shaft 130. The blades 130 may be forward-curved or backward-curved blades. The fan wheel may comprise a hub 135. Rotating elements of the fan 100 such as rotor, shaft 130, blades 140 and fan wheel form a rotary system of the fan 100. The rotary system of the fan 100 may further comprise a gear box. The gear box may be an indexing gear box, that is a shift gear box.

As shown in Fig. 1, the fan 100 may be an axial fan. However, the fan 100 may, for example, be a radial fan, tangential fan, centrifugal fan or cross-flow fan.

The fan 100 may be used for supplying or removing the fluid. The fan 100 may be oriented horizontally, vertically, or at any suitable angle.

The fan 100 may be stationary.

Thus, it may be employed in a building, for example in a house, such as a residential home or a multi-storey house. In more detail, the fan 100 may be wall-mounted, built into a wall or ceiling-suspended. For example, the fan 100 may be a whole-house fan for pulling hot air out of a building into its attic, an attic fan for regulating a heat level of the building's attic by exhausting hot air, or an evaporative cooler, that is swamp cooler, desert cooler or wet-air cooler, for cooling air by evaporating water. The fan 100 may be employed as a blower motor or blower module in a Heating, Ventilating, and Air Conditioning (HVAC) system. The fan 100 may be employed as a blower, that is compressor, in a fuel, for example gas or oil, burner of a central heating, self-contained central heating, or combined heat and power unit (CHP), that is total energy unit.

Further, the fan 100 may be portable.

Thus, it may be employed at home, in an office, a business, a shop or a

workshop. In more detail, the fan 100 may be a table-top fan, that is desk-top fan, or a stand-alone fan.

The fan 100 may be employed in a hair dryer or heat gun for supplying heated air. The fan 100 may be employed in a fume extractor such as a fume extraction hood, for removing exhaust gas such as exhaust fumes or waste air, for example in a laboratory, or kitchen at home or in a restaurant. The fan 100 may be employed in a fan oven, that is circulating-air oven or convection oven, for circulating hot air, for example in a laboratory, or kitchen at home or in a restaurant. The fan 100 may be employed in an air freshener for distributing a fragrance into surrounding air of a room. The fan may be employed in a computer system for cooling its components such as a processor. The fan 100 may be employed in a vacuum cleaner for removing particles such as dirt by compelling air comprising the particles through a filter.

Furthermore, the fan 100 may be employed mobile.

The fan 100 may be employed in a vehicle, for example a land vehicle such as a wheeled vehicle, in particular a car, lorry, truck or motorcycle, a tracked vehicle, or a railed vehicle, in particular a train; an aircraft such as an airplane; a spacecraft; or a watercraft, such as a ship. The fan 100 may be a radiator fan such as a car radiator fan for cooling an engine of a vehicle such as a car. The fan 100 may form part of a cooling fan module such as an electronically controlled cooling fan module having, for example, a power between 80 W and 1000 W. With regard to passenger comfort, the fan 100 may be an HVAC blower for ventilating a passenger compartment of a vehicle such as a car, defrosting windows and regulating internal temperatures by regulating an amount of air entering into the passenger compartment. The fan 100 may be employed as a blower, in a fuel burner of an independent vehicle heating system, that is auxiliary heating system.

The fan 100 may be an industrial fan or blower, that is a fan operating primarily against a resistance to flow being on a downstream side of the fan, for providing a large flow of gas such as air in industry. The fan 100 may be situated within a pipeline such as a gas pipeline.

Thus, the fan 100 may, among other things, be employed in heating, cooling, air- conditioning, that is controlling, heating or cooling, cleaning and humidifying or dehumidifying, and performing work.

According to embodiments of the invention, one, two, three or more rotational elements 120, 130, 140, 150 of the fan 100 comprise one, two, three or more chambers 210 having a fulcrum on a rotational axis 240, comprising a

circumferential balancing area 220 and being partially filled with an amount of a thixotropic balancing substance 230. The one, two, three or more rotational elements 120, 130, 140, 150 comprising one, two, three or more chambers 210 may comprise metal, for example steel, titanium, copper or aluminium, or composite material, for example glass-fibre-reinforced material or carbon-fibre- reinforced material, or synthetic material, for example plastics or plexiglas. The one, two, three or more rotational elements 120, 130, 140, 150 comprising one, two, three or more chambers 210 may replace original rotational elements 120, 130, 140 of the rotational system. The one, two, three or more rotational elements 120, 130, 140, 150 comprising one, two, three or more chambers 210 may be supplemental elements 150 to the rotational system.

The chamber 210 may be caved into the rotational element such as motor 120, blades 140, fan wheel or gear wheel. The chamber 210 may be situated in a shaft 130, such as a hollow shaft or tubular shaft, and extend partially or fully, such as substantially fully, along the hollow shaft or tubular shaft.

The circumferential balancing area 220 may comprise a nanostructure for improving movability and flow of the thixotropic balancing substance 230, said nanostructure being, for example, formed by a material, such as a varnish, comprising nanoparticles, or imprinted on said circumferential balancing area 220.

The thixotropic balancing substance 230 operates in the chamber 210. Owing to vibration, the thixotropic balancing substance 230 distributes itself along the circumferential balancing area 220, such that a CofG 250 moves towards the rotational axis 240, that is CofR, of the rotational element 130, 140; 200, such as the shaft 130, and the vibration is reduced or minimized or eliminated.

Fig. 2 shows, for a preferred embodiment of the invention, a cross-sectional view of the cylindrical chamber 210 at an initial point in time, when the thixotropic balancing substance 230 partially fills the chamber 210. The thixotropic balancing substance 230 may be evenly distributed along the circumferential balancing area 220 as shown in Fig. 2. For a vertical rotational axis 240, the thixotropic balancing substance 230 may partially fill the chamber 210 to an even level perpendicular to the rotational axis 240. For a horizontal rotational axis 240, the thixotropic balancing substance 230 may partially fill the chamber 210 to an even level along the rotational axis 240. However, the thixotropic balancing

substance 230 may partially fill the chamber 210 in any other manner. Owing to an imbalance of the rotational element 200 or the rotary system, a CofG 250 is offset from the rotational axis 240, that is CofR.

Fig. 3 shows, for the preferred embodiment of the invention, a cross-sectional view of the cylindrical chamber 210 at a point in time, when the thixotropic balancing substance 230 is distributed along the circumferential balancing area 220 of the chamber 210, such that the vibration is reduced. As the rotational element 200 rotates about the rotational axis 240, the thixotropic balancing substance 230 liquefies owing to vibration in the rotary system and distributes itself along the circumferential balancing area 220 of the chamber 210, such that an imbalance of the rotational element 200 is reduced, and, thus, the vibration is reduced. The CofG 250 moves towards the rotational axis 240, that is CofR. When the vibration is reduced, the thixotropic balancing substance 230 may solidify and maintain its position and distribution on the circumferential balancing area 220. Thus, during operation of the rotary system, its balance is constantly adjusted.

The amount of the thixotropic balancing substance 230 may be between approximately 0.001 kg and approximately 1000 kg, or between approximately 0.002 kg and approximately 500 kg, or between approximately 0.005 kg and approximately 200 kg, or between approximately 0.01 kg and approximately 100 kg, or between approximately 0.02 kg and approximately 50 kg, or between approximately 0.05 kg and approximately 20 kg, or between approximately 0.1 kg and approximately 10 kg, or between approximately 0.2 kg and approximately 5 kg, or between approximately 0.5 kg and approximately 2 kg, or approximately 1 kg. The chamber 210 may be filled with the amount of said thixotropic balancing substance 230 to between approximately 1 % and approximately 90 %, or between approximately 10 % and approximately 80 %, or between

approximately 25 % and approximately 75 %, or approximately 50 %.

Fig. 4 shows a cross-sectional view of a chamber 210 in a rotational element 200, 204 according to yet another embodiment of the invention. The chamber 210 is caved into the rotational element 200, 204, such as a fan wheel, a gear wheel or an additional element, for example a container or vessel. The chamber 210 is annular or ring-shaped. The chamber 210 may have a cross section being rectangular, square (not shown), semicircle-shaped (not shown), bell-shaped (not shown), circular (not shown) or the like. Fig. 5 shows a cross-sectional view of a chamber 210 in a rotational element 200, 204 according to yet another embodiment of the invention. With reference to Fig. 4, the rotational element 200, 204 comprises a centre hole 260. The centre hole 260 may be circular, square (not shown), hexagonal (not shown) or the like. The centre hole 260 of the rotational element 200, 204 may receive a shaft for coupling the rotational element 200, 204 to the rotational system.

The rotational element 200, 204 may comprise a hub of a car radiator fan wheel with blades (not shown), and the centre hole 260 houses a motor (not shown). In a preferred embodiment, the rotational element 200, 204 may be injection- moulded in one, two, three or more parts, and the chamber 210 may be sealed by a sealing element. The sealing element may be a snap-in or snap-on sealing element. The sealing element may be welded to the rotational element, for example using friction-welding, laser-welding or ultrasonic-welding.

Fig. 6 shows a cross-sectional view of a chamber 210 in another rotational element 200, 206 according to yet another embodiment of the invention. The chamber 210 is caved into the other rotational element 200, 206, such as a fan wheel, a gearing wheel or an additional element, for example a container or vessel. The chamber 210 is cylindrical. The chamber 210 may have a cross section being rectangular, square (not shown), semicircle-shaped (not shown), bell-shaped (not shown), circular (not shown) or the like.

Fig. 7 shows a cross-sectional view of another chamber 210 in a rotational element 200, 204 according to yet another embodiment of the invention. With reference to Fig. 4, the rotational element 200, 204 comprises an opening 270 providing access to the chamber 210. The opening 270 may be circumferential. The opening is situated, such that the balancing substance 230 is and remains contained in the chamber 210.

Fig. 8 shows a cross-sectional view of another chamber 210 in a rotational element 200, 204 according to yet another embodiment of the invention. With reference to Fig. 5, the rotational element 200, 204 comprises an opening 270 providing access to the chamber 210 as discussed with reference to Fig. 7.

The rotational element 200, 204 may comprise a hub of a car radiator fan wheel as described with reference to Fig. 5. Fig. 9 shows a cross-sectional view of yet another chamber 210 in a rotational element 200, 204 according to yet another embodiment of the invention. With reference to Fig. 5, the rotational element 200, 204 comprises an opening 270 providing access to the chamber 210 as discussed with reference to Figs 7 and 8. The rotational element 200, 204 may comprise a hub of a car radiator fan wheel as described with reference to Fig. 5.

Fig. 10 shows a cross-sectional view of another chamber 210 in a rotational element 200, 206 according to yet another embodiment of the invention. With reference to Fig. 6, the rotational element 200, 206 comprises an opening 270 providing access to the chamber 210 as discussed with reference to Fig. 7.

The thixotropic balancing substance 230 may be a thixotropic tyre balancing composition disclosed in EP patent application no. 0 281 252 and corresponding US patent no. 4,867,792, which are hereby incorporated by reference in their entirety, having a yield stress value between 1 Pa and 260 Pa being capable of balancing tyres by being able to flow under the influence of the vibrations induced when a heavy spot on the tyre hits the road surface.

The thixotropic balancing substance 230 may be a tyre gel balancing composition disclosed in European patent no. 0 557 365 and US corresponding patent no. 5,431,726, which are hereby incorporated by reference in their entirety, having a storage modulus of between 3000 and 15000 Pa and the specific gravity less than 1000 kg/m^ in the temperature range between -20 and +90 °C, preferably its storage modulus is about 9000 Pa, being capable of balancing tyres by being able to flow under the vibrations caused by imbalance in a wheel assembly. The composition preferably comprises a mixture of: 1) paraffinic oils, polybutene oils, polyolesters or polyol ethers; 2) hydrophobic or hydrophilic fumed silica; 3) polyalkyl-methacrylates, styrene-ethylene-propylene block copolymers or polyhydroxycarboxylic acid derivatives; and optionally corrosion inhibitors and antioxidants.

The thixotropic balancing substance 230 may be one of the tyre balancing compositions disclosed in European patent no. 1 196 299 Bl and corresponding US publication nos US-2005-0159534-A1 and US-2010-0252174-A1, which are hereby incorporated by reference in their entirety, having improved balancing properties and comprise a visco-plastic gel and solid bodies having an average smallest dimension in the range of 0.5-5 mm; preferably 1-4 mm, more preferably around 3 mm. When applied in a layer to the inside of a motor vehicle tyre, the compositions act by allowing the solid bodies move through the gel and to concentrate in areas to counteract imbalances. The solid bodies preferably have an average ratio alpha between their smallest and their largest dimension of alpha < = 2, more preferably alpha < = 1.5, especially around 1. The visco-plastic gel preferably has a storage modulus (G') between 1000 Pa and 25000 Pa at 22 °C, a loss modulus (G") smaller than the storage modulus, and a critical yield stress above 3 Pa at 22 °C. The bodies may be shaped as prolate or oblate ellipsoids, cylinders, rectangular parallelipipeds, or spheres, or mixtures of such bodies; they may have an apparent specific gravity in the range of 500- 3000 kg/m³, preferably 600-2000 kg/m³, in particular 700-1000 kg/m³, especially 800-900 kg/m³; they may be made from polyolefins, polystyrene, polyvinyl chloride, polyamide, rubber or glass. The weight ratio between the solid bodies and the gel is from 10: 1 to 1 : 10, preferably from 5: 1 to 1 : 5, in particular from 2: 1 to 3: 1, such as from 1 : 1 to 1 : 2.

The thixotropic balancing substance 230 may be one of the visco-elastic tyre balancing compositions disclosed in international patent application

WO 2010/055097, which is hereby incorporated by reference in its entirety, comprising 1) 85 to 97 % by weight of a glycol ether component comprising one or more ethylene/propylene glycol copolymer ethers of the general formula (I) or the general (II) or mixtures thereof R-0 {[CH(Ci.i3)CH₂-0-]_m [CH₂-CH₂-0-]„}H (I) R,-(0- {[CH(CHOCH₂-0-]_m [CH₂-CH₂-0-]_n}H)₂ (II) wherein R is hydrogen or an alkyl group of 2-8 carbon atoms; R i is an alkylene moiety of 2-8 carbon atoms in which the two substituents are not carried on the same carbon atom; m is the mole percentage of propylene glycol in the ethylene/propylene glycol copolymer moiety or moieties; and n is the mole percentage of ethylene glycol in the ethylene/propylene glycol copolymer moiety or moieties, wherein the ratio n: m is in the range from 35:65 to 80: 20; each glycol copolymer compound having a number average molecular weight in the range of 2000-10000; and 2) 3 to 15 % by weight of a fumed silica gel former; said balancing compositions being visco- elastic and having a Storage Modulus (G') between 1500 Pa and 5000 Pa at 22 °C, a Loss Modulus (G") smaller than the Storage Modulus up to a Cross Over

Frequency of 10-40 Hz, and a Critical Yield Stress exceeding 2 Pa. The thixotropic balancing substance 230 may be a composition for balancing a rotary system disclosed in international patent application no. WO 2011/042549, which is hereby incorporated by reference in its entirety, comprising an amount of a thixotropic balancing substance; characterized by an amount of hydrophobic particles or nanoparticles distributed in said amount of said thixotropic balancing substance.

The thixotropic balancing substance 230 may comprise a plurality of balls. The balls may comprise metal, such as steel, titanium, copper or aluminium, composite material, such as aluminiumoxide or ceramics, or plastics. The balls may be polished or coated, for example polytetrafluoroethylene- (PTFE)- coated. The balls may have a diameter between approximately 1 mm and approximately 50 mm, for example approximately 15 mm.

Fig. 11 shows a cross-sectional top view of a fan according to an embodiment of the invention under test. In the test, a rotary system comprising motor 120, shaft 130 and blades 140 on fan wheel of a fan 102 has been modified according to the preferred embodiment of the invention. The conventional fan 102 is a make TechnoStar, model FS40-8JBY three-bladed stand-alone fan having a fan wheel diameter of 400 mm, and running at approximately 1412 revolutions per minute (rpm). As shown in Fig. 11, the modified fan 102 comprises a

supplemental rotational element 150, that is adapter, attached to the shaft 130 behind the fan wheel and before the cage 110. The supplemental rotational element 150 corresponds with the open rotational element 200, 204 shown in Fig. 8 and has been made from transparent polymethyl methacrylate (PMMA, poly methyl 2-methylpropenoate, acrylic glass, for example Plexiglas). The

supplemental rotational element 150 has a diameter of 160 mm and a weight of 326 g. Its chamber 210 has been filled with 10 g of a thixotropic balancing substance 230 comprising 93 % by weight glycol polyethers, 4 % by weight fumed silica former and 3 % by weight polytetrafluoroethylene (PTFE)

nanoparticles in accordance with the above-mentioned international patent application nos PCT/EP2009/065058 and PCT/EP2010/065125. Experimental data has been taken with a make Crossbow (www.xbow.com), model CAL10HF3 triaxial acceleration sensor module 190 attached on top of the motor 120 as shown in Fig. 11, such that its y-axis is oriented along the shaft 130, its x-axis is horizontally oriented perpendicularly to the shaft 130, that is in rad ial d irection, and its z-axis is vertically oriented .

With reference to Fig . 11, Fig . 12 shows an exemplary representation of deflections (d_x, d_y and d_z) in x-axis, y-axis and z-axis, respectively, in

millimeter (mm) of the original stand-alone fan 102 over time (t) in seconds (s), that is without supplemental rotational element 150 and thixotropic balancing substance 230. The representation derives from experimental data taken at a rate of about 2 1/s and covers a period of about 60 s. After the orig inal fan 102 has been switched on, with a time delay of about 4 s, the deflections d_y in the y- axis increase to about 2.3 mm, the deflections d_z in the z-axis increase to about 1.3 mm, and the deflections d_x in the x-axis increase to about 0.4 mm . After the original fan 102 has been switched off, the deflections decrease and tail off.

With reference to Fig . 11, Fig . 13 shows an exemplary representation of deflections (d_x, d_y and d_z) in x-axis, y-axis and z-axis, respectively, in

millimeter (mm) of the modified stand-alone fan 102 over time (t) in seconds (s), that is with supplemental rotational element 150 and thixotropic balancing substance 230. The representation derives from experimental data taken at a rate of about 2 1/s and covers a period of about 60 s. After the modified fan 102 has been switched on, with a time delay of about 7 s, the deflections d_y in the y- axis increase only to about 0.9 mm, the deflections d_z in the z-axis increase only to about 0.4 mm, and the deflections d_x in the x-axis increase only to about 0.3 mm . After the orig inal fan 102 has been switched off, the deflections decrease and tail off.

A comparison of Figs 12 and 13 shows, that the supplemental rotational element 150 with the thixotropic balancing substance 230 substantially reduces the deflections in x-axis, y-axis and z-axis. Owing to initial vibration, the thixotropic balancing substance 230 liquefies and, owing to centrifugal force, distributes itself in the supplemental rotational element 150 such that the vibration, appearing as deflections, is greatly reduced . Inspection of the supplemental rotational element 150 with the thixotropic balancing substance 230 after the test shows a d istribution of the thixotropic balancing substance 230 similar to the distribution shown in Fig . 3.

Fig . 14 shows a schematic view of a car rad iator fan accord ing to an embod iment of the invention under test. In the test, a rotary system comprising motor (not shown), shaft 130 and blades 140 on fan wheel of a car radiator fan has been modified according to the preferred embodiment of the invention. The

conventional car radiator fan is a make Brose Fahrzeugteile GmbH & Co. KG (www. brose.com), model A55219-110 145-60098-01 nine-bladed car radiator fan having a fan wheel diameter of 518 mm and weight of 757 g (without shaft). As shown in Fig. 1, the modified fan comprises a supplemental rotational

element 150, that is adapter, attached to the fan wheel 140 with 63 cable binders 175. However, the supplemental rotational element 150 could be situated in a hub of the fan wheel, for example a hub comprising the rotational

element 200, 204 as described with reference to Fig. 5. The supplemental rotational element 150 corresponds with the closed ring-shaped rotational element 200, 204 shown in Fig. 5 and has been made from a metal -re info reed plastic tube. The supplemental rotational element 150 has a diameter of about 518 mm. Its chamber 210 has then been filled with 90 g of a thixotropic balancing substance 230 comprising 97 % by weight of a balancing substance in accordance with the composition number 6 in Table 1 of the above-mentioned international patent application no. PCT/EP2009/065058, and 3 % by weight polytetrafluoroethylene (PTFE) nanoparticles in accordance with the above- mentioned international patent application no. PCT/EP2010/065125.

Experimental data has been taken with two make Metra Mess- und

Frequenztechnik in Radebeul e. K. (www. mmf.de), model KS943B-100 triaxial acceleration sensor modules 190, 195 attached on top of a test rig 180 supporting the shaft 130 and being made of steel blocks as shown in Fig . 14, such that, their x-axes are horizontally oriented perpendicularly to the shaft 130, that is in radial direction, and their z-axes are vertically oriented perpendicularly to the shaft 130, that is in radial direction. Their y-axes are switched off. Signals are filtered at 43 Hz. Further, in order to add an imbalance, make Brose metal clamps having a weight of 8 g have been fixed on the fifth blade.

Fig. 15 shows a cross-sectional top view of the car radiator fan according to an embodiment of the invention under test. The supplemental rotational

element 150 comprises a chamber 210 having a circumferential balancing area 220 and the thixotropic balancing substance 230.

With reference to Figs 14 and 15, Fig. 16 shows an exemplary representation of accelerations (a_xi, a_zl, a_x2 and a_z2) in x-axes and z-axes, respectively, in accelerations of gravity (g) of the modified car radiator fan over time (t) in seconds (s) with supplemental rotational element 150, and without thixotropic balancing substance 230 and without added imbalance. The representation derives from experimental data taken at a rate of about 1 1/s and covers a period of about 60 s. After the modified car radiator fan initially without thixotropic balancing substance 230 has been switched on, the accelerations a_xi and a_x2 in the x-axes peak to about 0.45 g and about 0.55 g, respectively, and decrease to about 0.12 g and about 0.17 g, respectively; and the accelerations a_zl and a_z2 in the z-axes peak to about 0.26 g, and decrease to about 0.05 g and about 0.07 g, respectively. After the modified car radiator fan has been switched off, the accelerations a_xi and a_x2 in the x-axes peak again to about 0.45 g and about 0.55 g, respectively; and the accelerations a_zi and a_z2 in the z-axes peak again to about 0.27 g. The accelerations decrease and tail off. The peaks are caused by resonances of the test rig 180 during speeding up and speeding down.

With reference to Figs 14 and 15, Fig. 17 shows an exemplary representation of accelerations (a_xi, a_zi, a_x2 and a_z2) in x-axes and z-axes, respectively, in accelerations of gravity (g) of the modified car radiator fan over time (t) in seconds (s) with supplemental rotational element 150 and added imbalance, and without thixotropic balancing substance 230. The representation derives from experimental data taken at a rate of about 1 1/s and covers a period of about 60 s. After the modified car radiator fan with the added imbalance has been switched on, the accelerations a_xi and a_x2 in the x-axes peak to about 0.55 g and about 0.62 g, respectively, and decrease to about 0.14 g and about 0.20 g, respectively; and the accelerations a_zi and a_z2 in the z-axes peak to about 0.32 g, and decrease to about 0.06 g and about 0.08 g, respectively. After the modified car radiator fan with added imbalance has been switched off, the accelerations a_xi and a_x2 in the x-axes peak again to about 0.55 g and about 0.62 g, respectively; and the accelerations a_zi and a_z2 in the z-axes peak again to about 0.32 g. The accelerations decrease and tail off. The peaks are caused by resonances of the test rig 180 during speeding up and speeding down.

A comparison of Figs 16 and 17 shows, that the added imbalance increase vibration as could be expected .

With reference to Figs 14 and 15, Fig. 18 shows an exemplary representation of accelerations (a_xi, a_zi, a_x2 and a_z2) in x-axes and z-axes, respectively, in accelerations of gravity (g) together with a representation of corresponding revolutions (R) in revolutions per minute (1/min) of the modified car radiator fan over time (t) in seconds (s) with supplemental rotational element 150 comprising an amount of the balancing substance and the added imbalance. The

representation derives from experimental data taken at a rate of about 1 1/s and covers a period of about 120 s. After the modified car radiator fan with

supplemental rotational element 150 comprising an amount of the balancing substance and the added imbalance has been switched on for a first cycle, the number of revolutions increases from 0 to and remain at about 2600 1/min; the accelerations a_xi and a_x2 in the x-axes peak to about 0.21 g and about 0.25 g, respectively, and decrease to about 0.05 g and about 0.08 g, respectively; and the accelerations a_zi and a_z2 in the z-axes peak to about 0.12 g, and decrease to about 0.04 g. After this modified car radiator fan has been switched off for a first time, the number of revolutions decreases from about 2600 1/min to 0; the accelerations a_xi and a_x2 in the x-axes peak again to about 0.20 g and about

0.24 g, respectively; and the accelerations a_zi and a_z2 in the z-axes peak again to about 0.11 g. The accelerations decrease and tail off. After this modified car radiator fan has been switched on for a second cycle after a short pause, the number of revolutions increases again from 0 to and remain at about 2600 1/min; the accelerations a_xi and a_x2 in the x-axes peak again to about 0.19 g and about 0.23 g, respectively, and decrease to about 0.05 g and about 0.07 g, respectively; and the accelerations a_zi and a_z2 in the z-axes peak again to about 0.11 g, and decrease to about 0.03 g. After this modified car radiator fan has been switched off for a second time, the number of revolutions decreases again from about 2600 1/min to 0; the accelerations a_xi and a_x2 in the x-axes peak again to about 0.18 g and about 0.22 g, respectively; and the accelerations a_zi and a_z2 in the z- axes peak again to about 0.11 g. The accelerations decrease and tail off. The peaks are caused by resonances of the test rig 180 during speeding up and speeding down. Owing to initial vibration, the thixotropic balancing substance 230 liquefies and, owing to centrifugal force, distributes itself in the supplemental rotational element 150 such that the vibration, appearing as accelerations, is greatly reduced over time. A comparison of the first cycle and the second cycle shows, that the accelerations are lower during the second cycle. The process continues into the second cycle, until the distribution saturates. A comparison of Figs 17 and 18 shows, that the supplemental rotational element 150 with the thixotropic balancing substance 230 substantially reduces the accelerations caused by the added imbalance in x-axes and z-axes. For example, for the modified car radiator fan with the added imbalance the acceleration a_x2 settles to about 0.20 g, and for the modified car radiator fan with supplemental rotational element 150 comprising an amount of the balancing substance and the added imbalance, the acceleration a_x2 settles to only about 0.07 g in the second cycle, that is to only about 35 % of the original value. Owing to initial vibration, the thixotropic balancing substance 230 liquefies and, owing to centrifugal force, distributes itself in the supplemental rotational element 150 such that the vibration, appearing as deflections, is greatly reduced.

Embodiments of the inventions comprise a corresponding apparatus that may carry out the method.

Embodiments of the inventions comprise a corresponding system that may carry out the method, possibly across a number of devices.

Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art, that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiments shown. It is to be understood, that the above description is intended to be illustrative and not restrictive. This application is intended to cover any adaptations or variations of the invention. Combinations of the above embodiments and many other embodiments will be apparent to those of skill in the art upon reading and understanding the above description. The scope of the invention includes any other embodiments and applications in which the above structures and methods may be used. The scope of the invention is, therefore, defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

1. A method of reducing vibration in a rotary system (120, 130, 140) of a fan (100), comprising :

balancing said rotary system (120, 130, 140),

characterized by

providing a rotational element (120, 130, 140, 150; 200) comprising a chamber (210) having a fulcrum on a rotational axis (240) of said rotational element (120, 130, 140, 150; 200), comprising a circumferential balancing area (220) and being partially filled with an amount of a thixotropic balancing substance (230).

2. The method of claim 1, further comprising :

rotating said rotational element (120, 130, 140, 150; 200) about the rotational axis (240), such that said thixotropic balancing substance (230) liquefies and distributes itself along the circumferential balancing area (220), and an imbalance of said rotational element (120, 130, 140, 150; 200) is reduced.

3. The method of claim 1 or 2, wherein :

said rotational axis (240) is oriented horizontally; or

- said rotational axis (240) is oriented vertically.

4. The method of claim 1 or 2, wherein :

said rotational element (120, 130, 140, 150; 200) is an original element of said rotary system (120, 130, 140, 150), a replacement element of said rotary system (120, 130, 140), or a supplemental element (150) to said rotary system (120, 130, 140);

said rotational element (130) is a hollow shaft or tubular shaft;

said rotational element (130) is an articulated shaft, for example a cardan shaft; or

- a combination thereof.

5. The method of claim 4, wherein:

the supplemental element (150) is disc-shaped; or

the supplemental element (150) is ring-shaped.

6. The method of claim 1 or 2, wherein :

said rotational element (120, 130, 140, 150) is a shaft (130);

said rotational element (120, 130, 140, 150) is a rotor of a motor (120); said rotational element (120, 130, 140, 150) is a blade (140);

- said rotational element (120, 130, 140, 150) is a bearing;

said rotational element (120, 130, 140, 150) is a gear wheel; or a combination thereof.

7. The method of claim 1 or 2, wherein :

- said chamber (210) is annular or ring-shaped, or cylindrical;

said chamber (210) has a cross section being rectangular, square, semicircle-shaped, bell-shaped or circular;

said chamber (210) has a diameter of between 0.005 m and 2 m, or between 0.01 m and 1 m, or between 0.02 m and 0.5 m, or between 0.05 m and 0.2 m, or 0.1 m;

said chamber (210) has a length of between 0.01 m and 1 m, or between 0.02 m and 0.5 m, or between 0.05 m and 0.2 m, or 0.1 m; or

a combination thereof.

8. The method of claim 1 or 2, wherein :

said amount of said thixotropic balancing substance (230) is between 0.001 kg and 1000 kg, or between 0.002 kg and 500 kg, or between 0.005 kg and 200 kg, or between 0.01 kg and 100 kg, or between 0.02 kg and 50 kg, or between 0.05 kg and 20 kg, or between 0.1 kg and 10 kg, or between 0.2 kg and 5 kg, or between 0.5 kg and 2 kg, or 1 kg;

said chamber (210) is filled with the amount of said thixotropic balancing substance (230) to between 1 % and 90 %, or between 10 % and 80 %, or between 25 % and 75 %, or 50 %; or

a combination thereof.

9. An apparatus for reducing vibration in a rotary system (120, 130, 140) of a fan (100), characterized by:

a rotational element (120, 130, 140, 150; 200) comprising a

chamber (210) having a fulcrum on a rotational axis (240) of said rotational element (120, 130, 140, 150; 200), comprising a circumferential balancing area (220) and being partially filled with an amount of a thixotropic balancing substance (230).

10. A rotary system (120, 130, 140) of a fan (100), for reducing vibration in said rotary system (120, 130, 140), characterized by:

a rotational element (120, 130, 140, 150; 200) comprising a

11. The rotary system of claim 10, wherein

a combination thereof.

12. The rotary system of claim 10, wherein

said chamber (210) is annular or ring-shaped, or cylindrical;

- said chamber (210) has a cross section being rectangular, square, semicircle-shaped, bell-shaped or circular;

- said chamber (210) has a length of between 0.01 m and 1 m, or between 0.02 m and 0.5 m, or between 0.05 m and 0.2 m, or 0.1 m; or

a combination thereof.