WO2009109912A1

WO2009109912A1 - Fan

Info

Publication number: WO2009109912A1
Application number: PCT/IB2009/050853
Authority: WO
Inventors: George Sjoerd Mazereeuw
Original assignee: Donald, Heather June
Priority date: 2008-03-03
Filing date: 2009-03-03
Publication date: 2009-09-11

Abstract

The present invention concerns a fan (10) which has pitch-adjustable fan blades (12). The fan is driven by a drive shaft (14) connected to an electric motor. The fan also includes an actuator (22) connected to the fan blades to cause adjustment of the pitch of the blades. An adjustor (24) is connected to the actuator, with the adjustor being movable between a first adjustor position and a second adjustor position. Movement of the adjustor causes movement of the actuator which causes adjustment of the blade pitch. The adjustor is connected to a stepper motor (28) which causes the adjustor to be moved axially from its first position to its second position. In one preferred application, the fan may be used in association with the evaporator and/or condenser of a refrigerator or cooler.

Description

"FAN"

BACKGROUND TO THE INVENTION

THIS invention relates to a fan. In particular the invention concerns a fan comprising a number of pitch-adjustable fan blades.

Many refrigerators make use of a cooling system which comprises an evaporator, a condenser and a compressor. In use, a refrigerant is vapourised inside the evaporator, thereby causing heat to be absorbed from the cooling chamber of the refrigerator. By having the refrigerant absorbing heat from the cooling chamber, the temperature inside the cooling chamber will drop. From the evaporator the refrigerant is fed to the condenser where heat is extracted and the gas is condensed to a liquid, whereafter it is fed to the compressor and then back to the evaporator. By running this process continuously, the temperature inside the cooling chamber can be reduced to a desired level.

A commercial refrigerator will normally have two locations where air is forced to undergo movement. These locations are namely at the condenser and at the evaporator. Such movement is typically induced by way of fans. In the case of the condenser fan motor, communication is provided with the compressor such that when the compressor is active, the condenser fan motor will also be active. Correspondingly, when the compressor is inactive, the condenser fan motor will also be inactive. A number of problems are, however, associated with such an operating arrangement. These problems include that when the condenser is operative, air together with dust and other unwanted particles will typically be drawn through the condenser. Over a prolonged period of use dust and other unwanted particles will block the condenser causing a drop in heat exchange and a consequential loss in performance efficiency. Ultimately the compressor will be damaged due to the fact that it will overheat as a result of a decrease in the viscosity of the lubrication oil used in the compressor.

Furthermore, when the refrigerator operates in high ambient temperature conditions, the refrigeration system may under-condense and, in addition to which, the cooling operation of the compressor may become inefficient. Also, when the refrigerator operates in low ambient temperature conditions, the refrigeration system may over-condense resulting in inefficiency or, in severe instances, non-performance of the refrigeration system.

In order to address the problem of over condensing, persons have in the past, as a temporary measure, partly blocked the air-flow through the condenser. Further, to avoid blockage in the condenser resulting from dust and other undesirable particles, certain refrigerator manufacturers have made use of fan motors which cause the condenser fan blades to switch the direction of rotation periodically, such that dust which could cause blockage can be blown from the condenser.

No remedies are currently known for addressing overheating and under- condensing in refrigeration systems.

The evaporator fan in turn serves to ensure proper heat exchange in the refrigerator and, therefore, normally runs continuously. Without an evaporator fan, the evaporator will become "iced-up" as no heat will be extracted from the cooling chamber of the refrigerator, with the result that the refrigerator will no longer function.

A typical evaporating temperature for a commercial refrigerator which has a required set point of, say 3°C, is in the region of approximately -10°C to - 12⁰C. As the evaporating temperature will decrease when the temperature inside the appliance is caused to decrease, it would be beneficial to have a variable air flow through the evaporator to ensure optimum heat exchange and energy savings and consequently optimum performance of the refrigerator. Care should, however, be taken to ensure that the velocity of the air flow is not too low in magnitude as this would result in the evaporator becoming iced-up. Furthermore, a velocity of too high a magnitude will result in inefficient heat exchange with a consequential drop in cooling performance.

It is an object of the present invention to address the above problems.

SUMMARY OF THE INVENTION

According to the present invention there is provided a fan including:

at least one fan blade to be driven by a drive shaft, the at least one fan blade being movable between a first position and a second position;

an actuator for connection to the at least one fan blade and for causing the at least one fan blade to be moved from its first position to its second position, the actuator being mounted about the drive shaft; and

an adjustor for connection to the actuator, the adjustor being movable between a first adjustor position and a second adjustor position, wherein movement of the adjustor from its first adjustor position to its second adjustor position will lead to the actuator causing the at least one fan blade to be moved from its first position to its second position.

Further in accordance with the invention, the pitch angle of the at least one fan blade changes when the fan blade is moved from its first position to its second position.

Typically the arrangement is such that the adjustor moves axially relative to the drive shaft when it is moved from its first adjustor position to its second adjustor position. For this purpose the fan blade includes an actuator engagement formation and the actuator includes a fan blade engagement formation for complemental engagement with the actuator engagement formation. Conveniently the actuator engagement formation of the fan blade comprises a connecting member and the fan blade engagement formation comprises a complementally sized connecting member cavity in which the connecting member is held. The arrangement is advantageously such that the actuator moves axially along the drive shaft when the adjustor is moves from its first adjustor position to its second adjustor position.

In a preferred embodiment, the adjustor comprises an adjustor shaft which is slidably beatable inside the drive shaft. The drive shaft may have a cavity formation therein through which actuator connectors can pass in order to secure the actuator to the adjustor shaft. The adjustor shaft may be connected to a stepper motor by means of a spindle. Preferably the adjustor shaft is connected to the actuator and an adjustor member which is beatable inside the adjustor shaft and which is connectable to a stepper motor is provided, with the adjustor shaft and adjustor member being connected to one another by at least one bearing.

Other aspects of the invention provide a refrigerator including an evaporator and a fan as summarised and/or a condenser and a fan as summarised, the fan(s) being arranged to cause air to flow over the evaporator and/or the condenser. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, wherein:

Figure 1 shows a diagrammatic exploded perspective view of a fan in accordance with a first embodiment of the invention;

Figure 2 shows a diagrammatic partial cross-sectional view of the assembled fan of Figure 1;

Figure 3 shows a diagrammatic perspective view of a fan blade for use in the fan of Figure 1 ;

Figure 4 shows a diagrammatic perspective view of a fan blade and fan blade actuator;

Figure 5 shows a diagrammatic exploded perspective view of a fan in accordance with a second embodiment of the invention; and

Figure 6 shows a diagrammatic representation of an adjustor of the fan of Figure 5.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Figure 1 and Figure 2 show a fan in accordance with the present invention, generally indicated with the reference numeral 10. In this embodiment of the invention the fan 10 is used as an evaporator fan in a refrigerator, not illustrated in the drawings. The fan 10 comprises a plurality of fan blades 12 which are secured about a drive shaft 14 which is to be driven by an electric motor, not shown. The drive shaft 14 in turn is supported by two bearings 16 and 18 held inside housing members 17 and 19. As shown in Figure 2 the fan blades 12 are pivotatiy secured inside a fan blade support 20 such that they can be moved between first and second positions.

The fan 10 further includes an actuator 22 which is mounted about the drive shaft 14 and is connected to the fan blades 12. In use the actuator 22 will serve to cause the fan blades 12 to be moved between their respective first and second positions in a manner that will be described below. The fan 10 also includes an adjustor 24 which is connected to the actuator 22 with the use of a number of actuator connectors 26. The adjustor 24 of this embodiment is connected to a stepper motor 28. The stepper motor 28 in turn is in communication with an environment assessment system 30 which can monitor environmental conditions and in particular the temperature of the air coming off the evaporator of the refrigerator. The environment assessment system 30 in this embodiment of the invention comprises a thermometer together with suitable electronics equipment for activating the stepper motor 28 in response to measurements taken by the thermometer.

The operation of the fan 10 can be summarised by way of an example. In use, when the environment assessment system 30 determines that the temperature of the air coming off the evaporator of the refrigerator necessitates that the volume of air which is displaced by the fan blades 12 is to be adjusted, the environment assessment system 30 will activate the stepper motor 28 causing the adjustor 24 to move axially, relative to the drive shaft 14, from a first adjustor position to a second adjustor position. Such movement of the adjustor 24 will in turn cause the actuator connectors 26 to move the actuator 22 axially relative to the drive shaft 14, as a consequence causing the fan blades 12 to move from their first positions to their respective second positions.

By moving the fan blades 12 between their respective first and second positions the pitch of the fan blades 12 will be adjusted and as a result the volume of air which is displaced by them adjusted accordingly. The effect of this is that a predetermined environmental condition can be maintained accurately inside the cooling chamber of the refrigerator, and efficient heat exchange can be performed throughout the refrigeration process.

It will be understood that in moving between the first and second positions, the fan blades effectively rotate about axes which are generally radial with respect to the shaft 14.

Specific components of the fan 10 will now be discussed individually commencing with Figure 3 which shows a perspective view of one of the fan blades 12. The fan blade 12 includes a fan blade member 32 having an attachment formation 34. The attachment formation 34 in turn defines a groove 36 which in use will allow the fan blade 32 to pivot relative to the fan blade support 20, shown in Figure 2. The fan blade 12 includes an actuator engagement formation 38, here provided in the form of a connecting member 40, shaped as shown, which is attached to a lever 42. The lever 42 is slidably receivable inside a slot 44 in the attachment formation 34. As shown, the connecting member 40 is off-set relative to a longitudinal axis of the fan blade member 32.

Although not shown in the drawings, it is envisaged that the attachment formation 34 and the actuator engagement formation 38 could be of unitary construction.

Figure 4 shows the fan blade 12 pivotally connected to the actuator 22. The actuator 22 has a fan blade engagement formation 46 in the form of a hole. The connecting member 40 of the fan blade 12 fits into the hole 46 of the actuator 22.

Returning to Figure 1 and Figure 2 of the drawings it is pointed out that the fan blade support 20 comprises two fan blade support members 20.1 and 20.2 which are shaped as shown and which are secured to the drive shaft 14 with the use of locking brackets 48 that engage locking bracket cavities 50 on the drive shaft 14. As shown, the actuator 22 is mounted about the drive shaft 14 and is connected to the adjuster 24 with the use of the actuator connectors 26 which can pass through a slot 52 provided in the drive shaft 14. The actuator connectors 26 include connector prongs 54 which are sized for being located in connector cavities 56 of the adjustor 24.

In this embodiment the adjustor 24, provided in the form of an adjustor shaft, is sized for slidable location inside the drive shaft 14. The adjustor 24 is connected to an adjusting system 58 which in turn comprises miniature bearings 60, a snap ring 62 and an adjustor shaft connector 64 which supports a threaded spindle 66 in communication with the stepper motor 28.

In use activation of the stepper motor 28 will cause the spindle to rotate, in turn causing the adjustor 24 to move axially along the drive shaft 14. Movement of the adjustor 24 will impart axial movement to the actuator 22 via the connector prongs 54 of the actuator connectors 26. Axial movement of the actuator 22 in turn will induce pivotal or rotational movement of the fan blades 12 via their respective actuator engagement formations 38 and about generally radial axes, thereby changing the pitch of the fan blades and as a consequence the volume of air which can be displaced by the fan 10.

It is also envisaged that an alternative stepper motor can be used wherein the rotor of the stepper motor rotates instead of the spindle. The spindle will move axially due to conversion of rotary movement of the rotor to axial movement of the spindle within the stepper motor. With the use of the alternative stepper motor there is also provided a switch which can be used as a limit switch to ensure that the stepper motor will not move the adjustor 24 further than the fan blades 12 allow. The switch can also be used to set a datum or reference point of the stepper motor. The stepper motor will reset to the datum or reference point once the limit switch is activated.

An advantage of making use of a stepper motor is that the fan blades can be rotated with very small angle increments, typically less than 0.1 °. Figure 5 shows an exploded perspective view of a fan 100 in accordance with a second embodiment of the invention. Similarly to the fan 10 described above the fan 100 includes a plurality of fan blades 12 which are secured about a drive shaft 14. The fan blades 12 are further also pivotally secured inside a fan blade support 20 such that they can be pivoted between first and second positions about generally radial axes.

The fan 100 also includes an actuator 22 which is mounted about the drive shaft 14 and is connected to the fan blades 12. Similar to the operation of the fan 10, in use the actuator 22 of the fan 100 will serve to cause the fan blades 12 to be moved between their respective first and second positions when an adjustor 24 is caused to move axially, relative to the drive shaft 14, from a first adjustor position to a second adjustor position. The structure of the adjustor 24 differs from that of the fan 10 as will be described below.

It is pointed out that the fan blade actuator 22 of the fan 100 is five sided and not round as the actuator 22 of the fan 10. It is envisaged that the multi-sided configuration of the actuator which will enable it to withstand the applied torque in an effective manner. It will be understood that the multiple side faces of the actuator will cooperate with corresponding faces within the support members 20.1 and 20.2.

Components which are shown in Figure 5 and which have not been discussed above include an electric motor 102 for driving the drive shaft 14 as well as an outer housing 104 in which the fan blade support 20 can be enclosed. The outer housing 104 has a bearing cavity 106 in which a drive shaft bearing 108 for the drive shaft 14 can be held. The outer housing 104 can be secured to a cradle 110 with the use of pins 112. Although not shown in the drawings, the cradle will typically include a finger guard. Also, although not shown, the cradle 110 will support a bearing for holding an end portion of the drive shaft 14. The stepper motor 28 of the fan 100 is secured inside a stepper motor housing 114. It is envisaged that retaining rings (not shown in the drawings) could be used to prevent the stepper motor 28 from causing the drive shaft 14 to move axially as the adjustor 24 is moved. In an embodiment not shown in the drawings, the retaining rings are located adjacent the drive shaft bearing 108. The drive shaft 14 is further secured in position by means of a shoulder located on the drive shaft 14, with the shoulder being in contact with the drive shaft bearing 108 to prevent axial movement of the drive shaft.

Figure 6 provides a diagrammatic representation of the adjustor 24 of the fan 100. The adjustor 24 comprises an adjustor shaft 116 which is secured to the actuator 22 via a number of connectors 118 which are held in place with the use of connector rings 120, shown in Figure 5. The connector rings 120 slot into suitable cavities 121 in the side walls of the actuator 22. In another embodiment not shown in the accompanying drawings, the connectors 118 are covered by the connector rings 120.

The adjustor 24 further includes an adjustor member 124 which is beatable inside the adjustor shaft 116 and is connectable to a shaft 126 of the stepper motor 28. The adjustor shaft 116 includes a shoulder 128 with two miniature bearings 130 located on either side thereof. The bearings 130 provide a connection between the adjustor shaft 116 and the adjustor member 124 as shown. In another embodiment not shown in the accompanying drawings two thrust bearings in addition to the two bearings 130 are used to connect the adjustor shaft 116 and the adjustor member 124. The thrust bearings are used to ensure that the axial loads due to the axial movement of the adjustor 24 can be withstood. The thrust bearings are mounted about the adjustor shaft 116 on opposite sides of the bearings 130.

In order to secure the adjustor member 124 in position inside the adjustor shaft 116, a spacer 132, a bolt 134 and a washer 136 are provided as shown. The adjustor member 124 includes an inner threaded portion 125 whereby the bolt 134 and the washer 136 cooperate with the spacer 132 to secure the adjustor member 124 in position inside the adjustor shaft 116.

Referring to Figure 5 of the drawings it is pointed out that the adjustor member 124 includes a gripping formation 138 provided in the form of four prongs shaped as shown. The gripping formation 138 is sized to be held by a holding formation 140 on a holder member 142. The holder member 142 is in turn is sized such that in can be held securely in position by the cradle 110 with the use of two shoulders 144.

The operation of the fan 100 is similar to that of the fan 10 with the difference that the stepper motor 28, via its shaft 126, will cause the adjustor member 124 and in turn the adjustor shaft 116, connectors 118 and the actuator 22 to undergo axial movement relative to the drive shaft 14. In this regard it is pointed out that the holding formation 140 of the holder member 142 will guide movement of the adjustor member 124 via its interaction with the gripping formation 138. It will accordingly be appreciated that while the actuator 22 will undergo axial movement while also being driven rotationally by the drive shaft 14, the adjustor member 124 will not undergo any rotational movement, as a result of the interaction between its gripping formation 138 and the holding formation 140 of the holder member 142.

The majority of the components of the fan 10 operate purely mechanically and it is belived that this will contribute to reliable operation. Another important feature of the invention is the compactness of the mechanical components, for example the drive shaft 14, actuator 22 and adjustor 24. The effective miniaturization of the mechanical components makes the fan eminently suitable for use in a refrigerator to force air to move through an evaporator or a condenser. It is further envisaged that the fan 10 could be used to force air to move through both the evaporator and the condenser of the refrigerator. By using the fan 10 in a refrigerator, variable air flow through the evaporator and/or the condenser can be achieved, by adjustment of the pitch angle of the fan blades 12. The air flow can also be reversed by either reversing the rotational direction of the motor or by changing the pitch angle of the fan blades 12 by the desired amount.

As indicated above an important application of the fan of the invention is in a refrigerator or cooler. This application is described in detail in the specification of a copending international patent application entitled "Refrigeration System", filed simultaneously with the present application by the present applicant and claiming priority from ZA2008/01996. The disclosure of the copending application is incorporated herein in entirety by way of reference.

In initial testwork it has been shown that use of an evaporator fan as described in a commercial refrigerator can lead to substantial energy savings as a result of more efficient heat exchange, and to less temperature variation across the refrigerated space.

In a refrigerator condenser duty it would be possible, by reversing the direction of the air flow across the condenser of a refrigerator, to dislodge and blow away unwanted dust and other particles which may settle on the condenser surfaces.

Although specific mention has been made of the fan being used in refrigeration duties, it is envisaged that it could also be used in other applications, for example in ventilation and air conditioning systems or in the automotive industry.

Claims

1.

A fan including:

2.

A fan according to claim 1 , wherein the pitch angle of the at least one fan blade changes when the fan blade is moved from its first position to its second position.

3.

A fan according to either claim 1 or 2, wherein the adjustor moves axially relative to the drive shaft when it is moved from its first adjustor position to its second adjustor position.

4.

A fan according to any one of the preceding claims, wherein the fan blade includes an actuator engagement formation.

5.

A fan according to claim 4, wherein the actuator includes a fan blade engagement formation for complemental engagement with the actuator engagement formation.

6.

A fan according to claim 5, wherein the actuator engagement formation of the fan blade comprises a connecting member and the fan blade engagement formation comprises a complementally sized connecting member cavity in which the connecting member is held.

7.

A fan according to any of the preceding claims, wherein the actuator moves axially along the drive shaft when the adjuster is moves from its first adjuster position to its second adjuster position.

8.

A fan according to any one of the preceding claims, wherein the adjuster comprises an adjuster shaft which is slidably locatable inside the drive shaft.

9.

A fan according to claim 8, wherein the drive shaft has a cavity formation therein through which actuator connectors can pass in order to secure the actuator to the adjuster shaft.

10.

A fan according to claim 9, wherein the adjuster shaft is connected to a stepper motor by means of a spindle.

11.

A fan according to claim 10, wherein the adjustor shaft is connected to the actuator and an adjustor member which is beatable inside the adjustor shaft and which is connectable to a stepper motor is provided, with the adjustor shaft and adjustor member being connected to one another by at least one bearing.

12.

A fan according to any one of the preceding claims, wherein the at least one fan blade is pivotally secured to a fan blade support.

13.

A refrigerator including an evaporator and a fan according to any one of claims 1 to 13, the fan being arranged to cause air to flow over the evaporator.

14.

A refrigerator including a condenser and a fan according to any one of claims 1 to 13, the being arranged to cause air to flow over the condenser.