BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a prior art fan assembly of the type used for automotive applications.
FIG. 2 is a perspective view of a variable pitch fan blade mechanism according to the present invention.
FIG. 3 is a partly sectional side view of the variable pitch fan blade mechanism according to the present invention, wherein the fan blades have a neutral pitch.
FIG. 3A is a partly sectional side view of a fan blade and its respective push rod, seen along line 3A-3A of FIG. 3.
FIG. 4 is a partly sectional side view of the variable pitch fan blade mechanism according to the present invention, wherein the fan blades have a positive pitch.
FIG. 4A is a partly sectional side view of a fan blade and its respective push rod, seen along line 4A-4A of FIG. 4.
FIG. 5 is a partly sectional side view of the variable pitch fan blade mechanism according to the present invention, wherein the fan blades have a negative pitch.
FIG. 5A is a partly sectional side view of a fan blade and its respective push rod, seen along line 5A-5A of FIG. 5.
FIG. 6 is a perspective view of a fan assembly of the type used for automotive applications, wherein a pair of fans are equipped with the variable pitch fan blade mechanism according to the present invention
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the Drawing, FIGS. 2 through 6 depict a preferred embodiment of the variable pitch fan blade mechanism 100 according to the present invention.
With initial reference to FIGS. 2 through 3A, the variable pitch fan blade mechanism 100 includes a fan shaft 102 which is connected distally (not shown) to a conventional bearing and is driven conventionally, as discussed hereinabove. A proximal end portion 102p of the fan shaft 102 is configured to provide an axially aligned motor receptacle 104 and a communicating follower receptacle 106 having a sidewall 108 provided with a plurality of axially aligned splines 110. A drive component 112, composed, by way of example, of an electric motor 114 having a threaded motor shaft 116, is seated in the motor receptacle 104, wherein the electric motor is prevented from rotating in the motor receptacle, as for example by a non-circular mutual engagement or by a key-slot interference 118. The electric motor 114 may be preferably a stepper motor having conventional circuitry associated therewith which remembers the absolute rotational position of the threaded motor shaft 116. Wiring 120 from the electric motor 114 exits the fan shaft 102 in the form of external rings 122 which are affixed to the fan shaft. Conventional brush contacts 122b slide on the slip ring to thereby electrically connect the electric motor to a conventional external electric power circuit (not shown).
The drive component 112 is drivingly engaged with respect to a follower component 130. The follower component 130 includes a pedestal 132 having axially aligned splines 134 on its periphery. The follower component 130 further has an axially aligned threaded bore 136. The pedestal 132 is received in the follower receptacle 106, wherein the two sets of splines 110, 134 mutually mesh, allowing mutual axial sliding without rotation as the threaded motor shaft 116 is threadingly engaged with respect to the threaded bore 136. In this regard, actuation of the electric motor 114 in one direction results in the follower component 130 moving axially away from the electric motor, while rotation of the electric motor in the opposite direction results in the follower component moving toward the electric motor.
The follower component 130 further includes a head 138. A plurality of fan blades 140 are resiliently attached to the head 138. The preferred attachment is via a torsion bar 142 non-rotatingly anchored at one end in radial or, more preferably, tangential (as shown), disposition of the head 138 and non-rotatingly anchored at the other end in, preferably, bisecting disposition to an inside end 140i of its respective fan blade 140 so that a torque moment is established between the torsion bar and the push rod. The torsion bars 142 each have a pre-loaded torsional bias, as will be described momentarily.
The drive component 112 in combination with the follower component 130 provide, collectively, a linear actuator 148.
A push assembly 150 is connected to the proximal end 102e of the fan shaft 102 (i.e., at the end of the proximal end portion 102p), being composed of a push plate 152 and a plurality of upstanding (axially aligned) push rods 154, there being one push rod, respectively, for each fan blade 140. Each push rod 154 engages its respective fan blade adjacent a contact edge 140e thereof, all engaging at either the leading edge 140el or following edge 140ef. The aforementioned torsional biasing TB of the torsion bars 142 (see FIG. 3A) is such that the contact edge 140e of each fan blade is resiliently biased into abutment with the rod end 154e of its respective push rod such that axial movement of the push rods (via the above described linear actuator 148) results in resiliently compliant changes of pitch of the blades.
With particular reference to FIGS. 3 through 5A, operation of the variable pitch fan blade mechanism 100 will now be detailed.
It is seen in FIGS. 3 and 3A, merely by exemplary reference, that the linear actuator 148 has provided a neutral pitch to the fan blades 140, wherein by “neutral pitch” is meant that the fan blades have a blade pitch BP which is oriented parallel to the plane of rotation P (which is, itself, axially normal to the fan shaft axis SA) whereby rotation of the fan shaft results in no axial forced air movement. At this orientation, the center of each of the torsion bars 142 is spaced a distance X1 from the push plate 152.
Referring next to FIGS. 4 and 4A, the electric motor 114 has been actuated, whereby the threaded motor shaft 116 has threaded in the threaded bore 136 so as to thereby move the follower component 130 with respect to the push plate 152 from the position shown at FIG. 3 to that shown at FIG. 4. Electric power to the electric motor 114 through the rings 122 is only provided during the time the threaded motor shaft threads in the threaded bore. As a consequence of this axial movement of the follower component (and its push plate), the push rods have caused increased resilient tilting of the fan blades as compared to that of FIG. 3 so as to thereby compliantly change the blade pitch.
In this regard, the linear actuator 148 has been actuated so as to cause the push rods 154 to impart a positive pitch to the fan blades, wherein by “positive pitch” is meant that the blade pitch is acutely angled with respect to the plane of rotation P and direction of rotation (see arrow DR), whereby rotation of the fan shaft results in forced air movement axially toward the distal end of the fan shaft (see arrow FA). At this orientation, the center of each of the torsion bars 142 is spaced a distance X2 from the push plate 152. This movement of the push plate relative to the fan blades causes an increase in the torsional biasing of the torsion bars.
Referring next to FIGS. 5 and 5A, the electric motor 114 has been actuated, whereby the threaded motor shaft 116 has threaded in the threaded bore 136 (in the opposite rotational direction for that used to go from FIG. 3 to FIG. 4 as recounted immediately above) so as to thereby move the follower component 130 with respect to the push plate from the position shown at FIG. 3 to that shown at FIG. 5. Again, electric power to the electric motor through the rings 122 is only provided during the time the threaded motor shaft threads in the threaded bore. As a consequence of this axial movement of the follower component (and its push plate), the push rods cause decreased resilient tilting of the fan blades as compared to that of FIG. 3 so as to thereby compliantly change the blade pitch.
In this regard, the linear actuator 148 has been actuated so as to cause the push rods 154 to impart a negative pitch to the fan blades, where by “negative pitch” is meant that the blade pitch is acutely angled with respect to the plane of rotation P and direction of rotation (see arrow DR), whereby rotation of the fan shaft results in forced air movement axially away from the distal end of the fan shaft (see arrow FA′). At this orientation, the center of each of the torsion bars 142 is spaced a distance X3 from the push plate 152. This movement of the push plate relative to the fan blades causes a decrease in the resilient torsional biasing of the torsion bars, yet the torsional biasing is still strongly biasing the fan blade edge toward the always abutting push rod end.
From the foregoing description, it is clear that the fan blades may be made to compliantly change blade pitch to any amount of increasing/decreasing positive pitch and/or increasing/decreasing negative pitch, and that electric power is only needed during pitch change (and this is the case whether the fan shaft rotates clockwise or counter-clockwise).
FIG. 6 depicts an automotive application of the variable pitch fan blade mechanism 100, implemented as a fan assembly 200 analogous to that shown at FIG. 1. In an automotive application, the variable pitch fan blade mechanism 100 according to the present invention increases fuel economy by eliminating the losses inherent in variable speed electric fans or in viscous-clutch engine driven fans, and by allowing for decreased fan work at high vehicles speeds when air flows are inherently higher. Fan work can essentially be adjusted to the powertrain cooling needs, thus optimizing fan work and preventing parasitic energy loss.
To those skilled in the art to which this invention appertains, the above described preferred embodiment may be subject to change or modification. Such change or modification can be carried out without departing from the scope of the invention, which is intended to be limited only by the scope of the appended claims.
Patent Application
20080095627
