Patent Publication Number: US-6213715-B1

Title: Fan structure having a spherical four-bar mechanism

Description:
This application claims the benefit of U.S. Provisional Application 60/100,481 entitled “Infinity Fan” filed on Sep. 16, 1998, the content of which is hereby incorporated into the present specification by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a cooling fan and, more particularly, to a fan structure which has a spherical four-bar mechanism to permit the fan to move back-and-forth and up-and-down. 
     BACKGROUND OF THE INVENTION 
     A conventional cooling fan, either of the desktop or free standing type, oscillates in a generally horizontal plane to provide back-and-forth motion. This motion is achieved by a motor to drive the fan blades directly as well as to drive a gear train which causes rotation of an output shaft at a greatly reduced speed. The reduced speed output is typically used to drive a planar four-bar mechanism which generates the back-and forth motion of the fan head. Although this motion has some cooling benefit as compared to a non-oscillating fan, the motion can be improved. 
     Accordingly, there is a need to provide a fan structure which is capable of moving in three spatial planes to cause a fan head to move back-and-forth as well as up-and-down. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to fulfill the need referred to above. In accordance with the principles of the present invention, this objective is obtained by providing a fan structure including a fan head having a plurality of blades mounted for rotation. A mechanism is coupled to the fan head and is constructed and arranged to move the fan head along a surface of a sphere in a three dimensional pattern. At least one motor is constructed and arranged to cause rotation of the blades and movement of the mechanism. The mechanism thus provides both back-and-forth and up-and-down motion of the fan head. 
     In accordance with another aspect of the invention, a method provided to move an object in three spatial planes. The method includes defining a reference coordinate system having an origin at a center of a sphere. Four links are then pivotally coupled together at four joints such that axes of the joints intersect at the origin thereby defining a spherical four-bar mechanism. An object is coupled to one of the links. The mechanism is caused to move which causes movement of the object along a surface of the sphere in a three dimensional pattern. 
     Other objects, features and characteristics of the present invention, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 a  is a view of the intersection of four great circles and the resulting axes of rotation used to explained a spherical four-bar mechanism; 
     FIG. 1 b  shows a spherical four-bar linkage and link name notation as obtained from the great circles of FIG. 1 a;    
     FIG. 2 is a perspective view of a fan structure having a spherical four-bar mechanism, provided in accordance with the principles of the present invention; 
     FIG. 3 is a perspective view of a spherical four-bar mechanism of the invention as generated by computer aided design software, showing the shape of movement produced by the mechanism; 
     FIG. 4 is a plan view of the layout of links of the four-bar mechanism of FIG. 2; 
     FIG. 5 is a schematic illustration of the fan structure of the invention showing one embodiment of motor connection; and 
     FIG. 6 is a schematic illustration of the fan structure of the invention showing another embodiment of motor connection. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The fan structure of the invention employs a spherical four-bar mechanism which generates the unique ∞ “infinity” motion of the fan head. The symbol ∞ as used herein depicts the three-dimensional pattern of movement of the four-bar mechanism of the invention. A spherical four-bar mechanism consists of four links connected by four revolute joints (pin or hinge joints). A body undergoing spherical motion has three degrees of freedom. The degrees of freedom may be interpreted as rotation about three mutually perpendicular axes passing through the center of a sphere. This constrains spherical motion to be purely rotational. The rotations may be about a fixed axis or an instantaneous axis. In either case, the axis still must pass through the center of the sphere. Hence, the axes of the four revolute joints of spherical mechanisms must intersect in the sphere center. 
     An axis of rotation is defined by a unit vector whose origin is at the center of the sphere. The unit vector defines the direction of the line about which the spherical link rotates. In spherical kinematics, a link is characterized by the great circle arc subtended by it&#39;s two joints at the center of the sphere and the angular length of this arc is defined as the link&#39;s length. A great circle is any circle lying on the surface of a sphere whose radius is the same as the radius of the sphere. Two great circles intersect at two points on the sphere and define a line in space. This line passes through the center of the sphere. Unit vectors originating from the sphere center along the line in either direction define the axis of rotation. FIG. 1 a  shows the intersection of four great circles and the resulting axes of rotation and FIG. 1 b  shows a spherical four-bar linkage axes and link name notation. 
     Referring to FIG. 2, a fan structure is shown, generally indicated  10 , provided in accordance with the principles of the present invention. Using the link name notation of FIG. 1 b , the fan structure comprises a fixed link  12  which may be fixed to a base or the like. A driving link  14  is pivotally coupled at end  15  to the fixed link  12  via a pin connection  16 . The pin connection  16  is achieved by a rod or pin  17  rotatably coupled between the fixed link  12  and the driving link  14 . In the illustrated embodiment, the pin  17  is about 0.5 inches in length. End  18  of the driving link  14  is pivotally coupled to a coupler link  20  at end  22  thereof via pin connection  24 . The pin connection  24  is achieved by a rod or pin  26  rotatably coupled between the driving link  14  and the coupler link  20 . In the embodiment, the pin  26  is preferably about 1.5 inches in length. End  28  of the coupler link  20  is pivotally coupled to end  30  of a driven link  32  via a pin connection  34 . The pin connection  34  is achieved by a rod or pin  36  rotatably coupled between the coupler link  20  and the driven link  32 . In the embodiment, the pin  36  is preferably about 0.5 inches in length. End  38  of the driven link  32  is pivotally connected to the end  40  of the fixed link  12  via a pin connection  42 . The pin connection  42  is achieved by a rod or pin  44  rotatably coupled between the driven link  32  and the fixed link  12 . In the embodiment, the pin  36  is preferably about 1.5 inches in length. Thus, the fixed link  12 , the driving link  14 , the coupler link  20  and the driven link  32  define the four links of a spherical four-bar mechanism of the invention. A motor  49  is coupled to the driving link  14  and to the fan head  48  to provide movement to the four-bar mechanism and to rotate the fan head  48 , as will be explained more fully below. Each pin connection of the mechanism may include bearings (not shown). 
     Attaching the moving body (for example, a fan head) to the coupler link  20  usually requires additional parts: a coupler extension and/or a coupler attachment. As shown in FIG. 2, a coupler attachment  46  attaches the fan head  48  to the coupler link  20 . In FIG. 2, since the coupler attachment  46  is mounted on a length of the coupler link  20 , there is no need for a coupler extension to extend the coupler link  20 . 
     The coupler extension is an arc length that lies in the same plane and has the same radius as the coupler link  20 . The coupler extension either lengthens the coupler link  20  or the coupler extension lies within the coupler link  20 . This is possible because any point along the coupler link “great circle” could be the location of the moving body. The coupler attachment  46  has the same radius as the coupler link  20  and coupler extension. The coupler attachment  46  is connected normal to the coupler link  20 , but still at the same spherical radius. The coupler link  20 , coupler extension, and the coupler attachment  46  all have the same radius and lie on the surface of the same sphere. The result is a one degree of freedom mechanism which generates purely rotational motion. The exact motion generated by the mechanism is determined by the length of the four links  12 , 14 ,  20  and  32  and where the body to be moved (e.g., fan head) is attached to the mechanism. It is a unique and novel spherical four-bar mechanism of the invention (i.e., a set of four link lengths and a specific place to attach the moving body) which generates the ∞ “infinity” motion of the fan head  48 . 
     The fan structure  10  was modeled using computer-aided design software entitled “Sphinx-1.2”. The display of the mechanism of the invention using “Sphinx-1.2” is shown in FIG.  3 . Note that the ∞ “infinity” path  60  is shown in FIG.  3  and represents the movement of the four-bar mechanism and thus the fan head (not shown in FIG. 3) which would be attached to point  52  (an origin of the coordinate frame on the ∞ “infinity” path). It is this specific attachment point  52  to the mechanism that traces out the ∞ “infinity” motion. Notice also the coupler attachment  46  and coupler extension  50  which connect the coordinate frame to the mechanism. 
     The numerical data which includes the four link lengths and the coupler extension and coupler attachment lengths, are listed below in the Table. 
     
       
         
           
               
               
             
               
                   
                 TABLE 
               
               
                   
                   
               
             
            
               
                   
                 Linkage Name: ./inf_fan 
               
               
                   
                 Linkage type:   Crank-Rocker 
               
               
                   
                 Comment: This mechanism does not fold 
               
               
                   
                 Link lengths: 
               
               
                   
                    Driving: 47.350216 Driven: 53.806160 
               
               
                   
                    Coupler: 88.283920   Fixed: 87.894295 
               
               
                   
                 Link radii: 
               
               
                   
                    Driving: 1.150000 Driven: 1.300000 
               
               
                   
                    Coupler: 1.450000 Fixed: 1.000000 
               
               
                   
                 Driving fixed axis-o (in [F]): 
               
               
                   
                    X: 0.732747 Longitude: +132.88 
               
               
                   
                    Y: 0.000000 Latitude: +0.00 
               
               
                   
                    Z: −0.680501 
               
               
                   
                 Driving moving axis-a (in [M]): 
               
               
                   
                    X: 0.926299 Longitude: +87.30 
               
               
                   
                    Y: 0.374249 Latitude: +21.98 
               
               
                   
                    Z: 0.043682 
               
               
                   
                 Driven fixed axis-c (in [F]): 
               
               
                   
                    X: 0.703250 Longitude: +45.00 
               
               
                   
                    Y: −0.104311  Latitude: −5.99 
               
               
                   
                    Z: 0.703249 
               
               
                   
                 Driven moving axis-b (in [M]): 
               
               
                   
                    X: 0.272720 Longitude: +21.69 
               
               
                   
                    Y: −0.675005  Latitude: −42.45 
               
               
                   
                    Z: 0.685560 
               
               
                   
                 Theta-1 joint limits: 
               
               
                   
                    Min: −180.00   Max: +180.00 
               
               
                   
                 Sphinx kit angles: 
               
               
                   
                    Fixed link center longitude: +89.09 
               
               
                   
                    Fixed link center latitude: −4.15 
               
               
                   
                    Fixed link center roll: +4.32 
               
               
                   
                    Coupler extension length: −86.35 
               
               
                   
                    Coupler attachment length: −46.69 
               
               
                   
                 Position-1:     Position-2: 
               
               
                   
                 Longitude: +10.00  +80.00 
               
               
                   
                 Latitude: +20.00     +20.00 
               
               
                   
                 Roll: −45.00     +1.00 
               
               
                   
                 Position-3:     Position-4: 
               
               
                   
                 Longitude: +80.00  +10.00 
               
               
                   
                 Latitude: −20.00     −20.00 
               
               
                   
                 Roll: −45.00     +1.00 
               
               
                   
                   
               
            
           
         
       
     
     The fixed axes of the spherical four-bar mechanism are located with respect to a reference coordinate frame whose X-Z plane is horizontal and whose Y axis is oriented positive upwards. In other words, using a cartographers convention, the reference coordinate frame is located such that its is origin is at the center of the earth, that the equator lies in its X-Z plane, and the Y axis points up to the north pole. 
     With respect to this reference frame the directions of the fixed axes are given in the Table. Note that the Table alternatively locates the fixed axes with longitude and latitude angles expressed in degrees. Longitude is defined as a positive rotation about the Y axis and latitude is defined as a subsequent negative rotation about the X axis. The coupler extension  50  and coupler attachment  46  lengths are also listed in the Table in degrees. 
     The manufacturing layout of the four links  12 ,  14 ,  20 , and  32  and the coupler attachment  46  and coupler extension is shown in FIG.  4 . The links are oriented at the relative radii specified in the Table, i.e., the fixed link  12  is at the smallest radius. Note that the coupler attachment  46  is oriented above and to the left of the four links. The joint axes are located by the dashed lines a, b, c, d, and e and the long dashed line f indicates the end of the coupler extension, i.e., where to connect the coupler attachment  46  to the coupler link  20 . The coupler extension is shown in FIG. 3 with reference to lines e and f of FIG.  4 . The coupler extension  50  length is measured from the line a to line f in FIG. 4 with positive sense being clockwise. Similarly, the coupler attachment length is measure for the line h to the line g in FIG.  4 . 
     The manufacturing instructions for providing the spherical four-bar mechanism of the invention are as follows. First, the desired fan base, links and attachment are manufactured per the layout shown in FIG.  4 . Next, axis holes are made in the links  12 ,  14 ,  20  and  32  as indicated by the dashed lines a, b, c, d, and e, in FIG.  4 . To assemble the mechanism, the links are connected to the base to form a spherical closed chain as follows. A reference coordinate frame is located on a fan base  62  (FIG.  3 ). Recall that the fan structure  10  will move the fan head  48  on the surface of a sphere whose center is at the origin of the reference frame. Once this frame has been assigned, the axes of the fixed link  12  are located using either the longitude and latitude angles or the unit vectors listed in the Table. The fixed link  12  is then attached to the base  62 . Next, the driving link  14  is attached to the fixed link  12  at the driving fixed axis d using a pin and bearings as appropriate. The driven link  32  is then similarly attached to the fixed link  12  at axis c. The coupler attachment  46  is then rigidly connected to the coupler link  20  at the location indicated by the long dashed line f in FIG.  4 . The coupler link  20  is connected using pins and bearings as appropriate to the two free ends of the driving and driven links as shown in FIGS. 2 and 3. Finally, the fan head  48  (FIG. 2) is rigidly attached to the end of the coupler attachment  46  such that the axis of rotation of the fan blades passes through the origin of the reference coordinate frame. When the links are properly assembled, lines f and g of the coupler attachment  46  and coupler link  20 , respectively, are coincident. With reference to FIG. 4, the coupler attachment  46  is rotated 90 degrees with respect to the plane of the page and line f coincides with line g. 
     In the preferred embodiment, a single motor is used to rotate the fan blades and to move the four-bar mechanism of the invention. It can be appreciated, however, that one motor may be provided to rotate the fan blades and a separate motor may be provided to cause movement of the mechanism. 
     FIG. 5 is a schematic illustration of a preferred motor  49  connection of the fan structure  10 . The motor  49  includes a gearbox associated therewith to define a motor/gearbox  64  which is carried by the base  62 . The motor/gearbox  64  has a first, relatively slow rotating output shaft  66  coupled to the spherical four-bar mechanism  68  to drive mechanism  68  and thus move the fan head  48  in the ∞ pattern. The motor/gearbox  64  has a second, fast (relative to the first output shaft) rotating output shaft  70  preferably coupled to the fan blades  51  by a conventional, flexible rotating coupler  72  to cause rotation of the fan blades  51 . The flexible coupler  72  includes a flexible shaft carried within a protective flexible outer covering. Accordingly, both the spherical four-bar mechanism  68  and the fan blades  51  may be concurrently driven at different rotational speeds using a single motor  49 . 
     FIG. 6 shows another embodiment of the fan structure  10 ′ wherein the motor/gearbox  64 ′ is carried by a housing  74  of fan head  48 . The four-bar mechanism  68  is carried by the base  62  and the housing  74  is carried by the other end of the mechanism  68 . The motor/gearbox gear  64 ′ has a slow rotating output shaft  66 ′ coupled to drive the mechanism  68 , and a faster output shaft  70 ′ is coupled to drive the fan blades  51 . Of course, in yet another embodiment, the motor  49  may directly drive the fan blades  51  and gearing may be used to drive the spherical four-bar mechanism  68  more slowly such that the fan head  48  moves in the ∞ “infinity′ motion. 
     When the motor  49  is activated to cause motion of the four-bar mechanism  68  of the invention, the fan head  48  is moved by the mechanism such that the fan head spans about 80 degrees in the horizontal plane and about 40 degrees in the vertical plane. Traditional desktop and free standing fans generate a planar back-and-forth (i.e. horizontal plane) motion and no up-and-down (i.e. vertical) motion. 
     An advantage of the fan structure  10  of the invention is that the fan head moves in a three dimensional ∞ “infinity” pattern rather than the conventional back-and-forth motion of existing fan designs. Moreover, this new three dimensional motion is generated by a spherical four-bar mechanism. The use of the novel spherical mechanism means that the fan structure can generate both the rotation of the fan blades and the ∞ “infinity” motion of the fan head with one motor. The ∞ “infinity′” motion of the fan head is a significant improvement over existing oscillating fan designs yet no additional motors are required. The result is that the fan structure of the invention is comparable in price to current fan designs yet it provides improved cooling and comfort to the consumer. 
     The spherical four-bar mechanism of the invention may be used to drive other objects besides a fan head in the ∞ “infinity” pattern. For example, other applications include (but not limited to) the following: 
     Stirring/Mixing Applications-turn the mechanism “up-side-down” and attach a mixing blade in place of the fan head. 
     Security Camera—attach a security camera in place of the fan head. 
     Indoor Ceiling Fan—turn the fan structure “up-side-down′” and suspend it from a ceiling. 
     Motorized Target—attach a target in place of the fan head for shooting practice, pinball machines, etc. 
     The foregoing preferred embodiments have been shown and described for the purposes of illustrating the structural and functional principles of the present invention, as well as illustrating the methods of employing the preferred embodiments and are subject to change without departing from such principles. Therefore, this invention includes all modifications encompassed within the spirit of the following claims.