TEMPERATURE SENSITIVE FAN
United States Patent 3764227
A temperature sensitive fan having memory material which assumes its memorized shape that corresponds to a pitched fan at or above a predetermined temperature.
US Patent References:
Variable camber balding
Fanti - July 1962 - 3042371
Fan structure
Rom - March 1968 - 3373930
FAN APPARATUS FOR COOLING ENGINE
Kobashi - May 1969 - 3443744
Variable camber balding
Fanti - July 1962 - 3042371
Fan structure
Rom - March 1968 - 3373930
FAN APPARATUS FOR COOLING ENGINE
Kobashi - May 1969 - 3443744
Application Number:
05/279925
Publication Date:
10/09/1973
Filing Date:
08/11/1972
View Patent Images:
Export Citation:
Assignee:
Hayes-Albion Corporation (Jackson, MI)
Primary Class:
Other Classes:
416/132R, 416/132A, 310/63, 416/240, 310/62, 415/12
International Classes:
F04D29/36; F04D29/32; F04D29/36; F04D29/58
Field of Search:
416/37-39,132,240 415/12
Primary Examiner:
Powell Jr., Everette A.
Claims:
What is claimed is
1. A fan including a plurality of blades comprising a temperature responsive memory material which is relatively rigid at or above a predetermined temperature and is relatively flexible below said predetermined temperature and which has a memorized shape corresponding to a pitched fan blade such that said blade is pitched when operated at or above said predetermined temperature and said blade is less pitched when operated below said predetermined temperature.
2. A fan including a plurality of fan blades comprising:
1. A fan including a plurality of blades comprising a temperature responsive memory material which is relatively rigid at or above a predetermined temperature and is relatively flexible below said predetermined temperature and which has a memorized shape corresponding to a pitched fan blade such that said blade is pitched when operated at or above said predetermined temperature and said blade is less pitched when operated below said predetermined temperature.
2. A fan including a plurality of fan blades comprising:
Description:
BACKGROUND OF THE INVENTION
This invention relates to fan blades and in particular to a fan blade in which the pitch is increased as the temperature increases.
In applications such as automobiles, it is unnecessary for the fan to move air until the temperature of the cooling system is high. For example, when an automobile is operating in a cold environment the fan may not be necessary at all. Thus, it is desirable to design a fan which does not become operative until the temperature reaches some predetermined level.
Prior attempts to produce such a fan have used materials of different coefficients of expansion to form a fan blade, for example, see U.S. Pat. No. 3,373,930. However, this type of fan has not been commercially successful because only a limited amount of pitch may be produced in the fan at high temperatures. Moreover, the change in pitch occurs over a wide range of temperatures and thus, of necessity, the fan is pitched at temperatures below the predetermined level. Also, the materials which have been used in such fans are not strong enough to overcome the straightening effect of the centripetal force acting on the blades. Other prior heat sensitive fans have utilized geared mechanisms which are cumbersome and expensive to produce.
SUMMARY OF THE INVENTION
This invention presents a heat sensitive fan in which the blade is cambered over a relatively narrow range of temperatures. The blade will not lose a significant amount of pitch when it is operated at high speed and high temperatures due to centripetal force. A strip of temperature responsive memory material is affixed to a flexible fan blade. The temperature sensitive strip is formed such that its memorized shape corresponds to that of a pitched fan blade. When the critical temperature is reached the memory material returns to its memorized position and forces the flexible fan blade into a pitched configuration. When the temperature is lowered to a point below the critical temperature, centripetal force and/or the resiliency of the blade returns the blade and the temperature sensitive strip to a position of little or no pitch.
BRIEF DESCRIPTION OF THE DRAWINGS
The features of this invention will become more apparent in the following detailed description of a preferred embodiment when read in conjunction with the figures in which:
FIG. 1 is a plan view of a fan blade constructed in accordance with the principles of this invention as seen in the cold or low pitch state.
FIG. 2 is a cross sectional view of FIG. 1 taken along lines 2--2 and looking in the direction of the arrows.
FIG. 3 is a cross sectional view taken along lines 2--2 of FIG. 1 and looking in the direction of the arrows when the fan is in its hot or high pitch state.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Referring now to the figures wherein like reference numerals indicate like parts a flexible fan blade 10 is mounted on an arm 12 by a plurality of rivets 14. The arm 12 extends from a central hub 15. As will become apparent later herein, any number of blades may be carried by the hub and any type of mounting assembly may be utilized. The mounting assembly depicted herein has been selected for the sake of simplicity as it does not form part of the invention.
A strip of temperature responsive memory material 16 is attached to the front of the blade 10. The memory material 16 is selected such that it will be flexible below a critical temperature and will become very strong and will return to a memorized configuration at or above its critical temperature. Several titanium alloys possess the desired characteristics of the memory material 16. Alloys which may be used are described in U.S. Pat. Nos. 3,403,238 and 3,558,369. As set out in more detail in the referenced patents, by altering the alloy constituents various critical temperatures and/or critical ranges of temperatures may be realized.
In this preferred embodiment the memory material 16 has a memorized shape of high pitch as shown in FIG. 3. When the memory material is at or above its critical temperature it will return from any configuration to the pitched configuration shown in FIG. 3. When the temperature of the memory material 16 is below the critical temperature the resilience of the blade 10 and/or centripetal force will straighten the blade to the shape shown in FIGS. 1 and 2.
When the fan blade 10 is being operated below the critical temperature, or in a cold environment, the blade 10 will be substantially flat as shown in FIGS. 1 and 2. Consequently, the fan blade 10 will not be pumping air and will be drawing a minimum amount of power from the automotive engine. When the temperature of the environment reaches the critical temperature, the memory material 16 will revert to the shape shown in FIG. 3 and cause the fan blade to assume a configuration of maximum pitch. Thus, when the engine is hot, the fan is pumping the maximum amount of air and when the engine is cold the fan is pumping a minimum amount of air.
Selecting a proper critical temperature for the memory material 16 will depend upon the particular cooling equipment and the environment surrounding the engine. It must be selected such that the memorized shape is realized prior to the cooling equipment reaching its boiling point. Each application will have different requirements as may be determined by a simple testing procedure.
Although specific critical temperatures have been referred to herein, most of the known memory materials will return to the memorized shape over a range of temperatures. For example, the memory material may begin a transition at 170°F. and complete it at 185°F. Thus, the fan will become of increased pitch over a relatively narrow range of temperatures.
Although the memory material 16 has been illustrated as being in strip form it is obvious that many different configurations are suitable and if desired that a blade could be made solely from a sheet of memory material.
This invention relates to fan blades and in particular to a fan blade in which the pitch is increased as the temperature increases.
In applications such as automobiles, it is unnecessary for the fan to move air until the temperature of the cooling system is high. For example, when an automobile is operating in a cold environment the fan may not be necessary at all. Thus, it is desirable to design a fan which does not become operative until the temperature reaches some predetermined level.
Prior attempts to produce such a fan have used materials of different coefficients of expansion to form a fan blade, for example, see U.S. Pat. No. 3,373,930. However, this type of fan has not been commercially successful because only a limited amount of pitch may be produced in the fan at high temperatures. Moreover, the change in pitch occurs over a wide range of temperatures and thus, of necessity, the fan is pitched at temperatures below the predetermined level. Also, the materials which have been used in such fans are not strong enough to overcome the straightening effect of the centripetal force acting on the blades. Other prior heat sensitive fans have utilized geared mechanisms which are cumbersome and expensive to produce.
SUMMARY OF THE INVENTION
This invention presents a heat sensitive fan in which the blade is cambered over a relatively narrow range of temperatures. The blade will not lose a significant amount of pitch when it is operated at high speed and high temperatures due to centripetal force. A strip of temperature responsive memory material is affixed to a flexible fan blade. The temperature sensitive strip is formed such that its memorized shape corresponds to that of a pitched fan blade. When the critical temperature is reached the memory material returns to its memorized position and forces the flexible fan blade into a pitched configuration. When the temperature is lowered to a point below the critical temperature, centripetal force and/or the resiliency of the blade returns the blade and the temperature sensitive strip to a position of little or no pitch.
BRIEF DESCRIPTION OF THE DRAWINGS
The features of this invention will become more apparent in the following detailed description of a preferred embodiment when read in conjunction with the figures in which:
FIG. 1 is a plan view of a fan blade constructed in accordance with the principles of this invention as seen in the cold or low pitch state.
FIG. 2 is a cross sectional view of FIG. 1 taken along lines 2--2 and looking in the direction of the arrows.
FIG. 3 is a cross sectional view taken along lines 2--2 of FIG. 1 and looking in the direction of the arrows when the fan is in its hot or high pitch state.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Referring now to the figures wherein like reference numerals indicate like parts a flexible fan blade 10 is mounted on an arm 12 by a plurality of rivets 14. The arm 12 extends from a central hub 15. As will become apparent later herein, any number of blades may be carried by the hub and any type of mounting assembly may be utilized. The mounting assembly depicted herein has been selected for the sake of simplicity as it does not form part of the invention.
A strip of temperature responsive memory material 16 is attached to the front of the blade 10. The memory material 16 is selected such that it will be flexible below a critical temperature and will become very strong and will return to a memorized configuration at or above its critical temperature. Several titanium alloys possess the desired characteristics of the memory material 16. Alloys which may be used are described in U.S. Pat. Nos. 3,403,238 and 3,558,369. As set out in more detail in the referenced patents, by altering the alloy constituents various critical temperatures and/or critical ranges of temperatures may be realized.
In this preferred embodiment the memory material 16 has a memorized shape of high pitch as shown in FIG. 3. When the memory material is at or above its critical temperature it will return from any configuration to the pitched configuration shown in FIG. 3. When the temperature of the memory material 16 is below the critical temperature the resilience of the blade 10 and/or centripetal force will straighten the blade to the shape shown in FIGS. 1 and 2.
When the fan blade 10 is being operated below the critical temperature, or in a cold environment, the blade 10 will be substantially flat as shown in FIGS. 1 and 2. Consequently, the fan blade 10 will not be pumping air and will be drawing a minimum amount of power from the automotive engine. When the temperature of the environment reaches the critical temperature, the memory material 16 will revert to the shape shown in FIG. 3 and cause the fan blade to assume a configuration of maximum pitch. Thus, when the engine is hot, the fan is pumping the maximum amount of air and when the engine is cold the fan is pumping a minimum amount of air.
Selecting a proper critical temperature for the memory material 16 will depend upon the particular cooling equipment and the environment surrounding the engine. It must be selected such that the memorized shape is realized prior to the cooling equipment reaching its boiling point. Each application will have different requirements as may be determined by a simple testing procedure.
Although specific critical temperatures have been referred to herein, most of the known memory materials will return to the memorized shape over a range of temperatures. For example, the memory material may begin a transition at 170°F. and complete it at 185°F. Thus, the fan will become of increased pitch over a relatively narrow range of temperatures.
Although the memory material 16 has been illustrated as being in strip form it is obvious that many different configurations are suitable and if desired that a blade could be made solely from a sheet of memory material.