Patent Publication Number: US-2004052641-A1

Title: Fan unit having blades manufactured by blow molding and made from thermoplastic elastomer

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] This invention relates to a fan unit, more particularly to a fan unit having blade bodies that are manufactured by a blow molding process and that are made from a thermoplastic elastomer.  
       [0003] 2. Description of the Related Art  
       [0004] Referring to FIG. 1, a conventional fan unit is shown to include a fan casing  1  and a plurality of blades  2  extending radially and outwardly from the fan casing  1 .  
       [0005] The aforesaid conventional fan unit is disadvantageous in that the blades  2  are made from stiff plastics or metal so that a protective frame or a ventilation frame must be mounted to surround the fan unit in order to prevent injury to a person who accidentally touches the blades  2 .  
       SUMMARY OF THE INVENTION  
       [0006] The object of this invention is to provide a fan unit having blade bodies that are manufactured by a blow molding process and and that are made from a thermoplastic elastomer so as to minimize injury to a person in case he or she accidentally touches the blades during operation of the fan unit.  
       [0007] Accordingly, a fan unit of the present invention includes a motor having an output shaft, a fan casing, a plurality of blades, and a fastener unit. The fan casing is mounted non-rotatably on the output shaft of the motor, and includes an annular rear casing half having a plurality of angularly spaced-apart groove units, and an annular front casing half disposed in front of the rear casing half and having a plurality of angularly spaced-apart groove units. The blades are mounted on and extend radially and outwardly from the front and rear casing halves. Each of the blades includes a hollow blade body that is made from a thermoplastic elastomer, that is manufactured by a blow molding process, and that is exposed outwardly from the front and rear casing halves, and a coupler element that is fixed to the blade body, that is clamped between the front and rear casing halves and that has a rearwardly-extending tongue unit received snugly in a respective one of the groove units in the rear casing half, and a frontwardly-extending tongue unit received snugly in a respective one of the groove units in the front casing half. The fastener unit fastens the front and rear casing halves securely so as to prevent removal of the blades from the front and rear casing halves. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0008] These and other features and advantages of this invention will become apparent in the following detailed description of a preferred embodiment of this invention, with reference to the accompanying drawings, of which:  
     [0009]FIG. 1 is a perspective view of a conventional  
     [0010]FIG. 2 is an exploded view of a preferred embodiment of a fan unit according to the present invention;  
     [0011]FIG. 3 is a perspective view of the preferred embodiment;  
     [0012]FIG. 4 is a partly sectional view of the preferred embodiment; and  
     [0013]FIG. 5 is a sectional view of a blade taken along lines V-V of FIG. 4. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0014] Referring to FIGS. 2, 3 and  4 , the preferred embodiment of a fan unit according to the present invention is shown to include a motor  100 , a fan casing  10 , a plurality of blades  20 , and a fastener unit  50 .  
     [0015] As illustrated, the fan casing  10  is mounted non-rotatably on an output shaft  110  of the motor  100 , and includes an annular rear casing half  30  and an annular front casing half  40 . The rear casing half  30  has a plurality of angularly spaced-apart groove units  34  that are defined by a plurality of groove-defining wall portions  332 . The front casing half  40  is disposed in front of the rear casing half  30 , and has a plurality of angularly spaced-apart groove units  44  that are defined by a plurality of groove-defining wall portions  432 .  
     [0016] The blades  20  are mounted on and extend radially and outwardly from the front and rear casing halves  40 ,  30 . Each of the blades  20  includes a hollow blade body  21  (see FIG. 5) that is made from a thermoplastic elastomer, that has a cross-section shaped as a teardrop, that is manufactured by a blow molding process, and that is exposed outwardly from the front and rear casing halves  40 ,  30 , and a coupler element  22  that is fixed to the blade body  21 , that is clamped between the front and rear casing halves  40 ,  30 , and that has a rearwardly-extending tongue unit  223  which is received snugly in a respective one of the groove units  34  in the rear casing half  30 , and a frontwardly-extending tongue unit  222  which is  44  in the front casing half  40 .  
     [0017] The fastener unit  50  fastens the front and rear casing halves  40 ,  30  securely so as to prevent removal of the blades  20  from the front and rear casing halves  40 ,  30 .  
     [0018] In this embodiment, the rear casing half  30  includes an annular outer wall  32  with a front end, an annular inner wall  31  that is disposed coaxially in the outer wall  32  to define a shaft hole  351  which permits extension of the output shaft  110  of the motor  100  therethrough and that has a front end flush with the front end of the outer wall  32 , and a plurality of angularly spaced-apart rods  33  that extend radially and outwardly from the front end of the inner wall  31  to the front end of the outer wall  32  to form a plurality of parallel grooves  331  which constitute a respective one of the groove units  34  in the rear casing half  30 . The front casing half  40  includes an outer wall  42  that is aligned with the outer wall  32  of the rear casing half  30  and that has a rear end, an inner wall  41  that is disposed coaxially in the outer wall  42 , and that has a rear end flush with the rear end of the outer wall  42 , and a plurality of angularly spaced-apart rods  43  that extend radially and outwardly from the rear end of the inner wall  41  of the front casing half  40  to the rear end of the outer wall  42  of the front casing half  40  to form a plurality of parallel grooves  431  which constitute a respective one of the groove units  44  in the front casing half  40 .  
     [0019] The rear casing half  30  further includes a coupling tube  35  that extends coaxially and frontwardly from the front end of the inner wall  31  of the rear casing half  30  through the inner wall  41  of the front casing half  40 , and that has an external thread portion  353  and an inner wall surface formed with a planar portion  352  engaging a planar portion  130  of an outer wall surface of the output shaft  110  to prevent relative rotation therebetween. The fastener unit  50  is threadedly mounted on the external thread portion  353  of the coupling tube  35  so as to press the front casing half  40  against the rear casing half  30 , thereby preventing relative rotation between the front and rear casing halves  40 ,  30 . The fastener unit  50  includes an internally threaded sleeve  51  and a plurality of actuator elements  53  extending radially and outwardly from the sleeve  51  to facilitate turning of the sleeve  51  on the coupling tube  35 . A locking knob  120  is mounted threadedly on an outer end of the output shaft  110  of the motor  100  to prevent undesired removal of the sleeve  51  from the motor  100 .  
     [0020] Note that the coupler element  22  of each of the blades  20  has a tongue-mounting strip  224  which extends in a radial direction of the fan casing  10  and which is formed with two opposite side faces. Each of the rearwardly and frontwardly extending tongue units  223 ,  222  includes a plurality of tongues  223 ″,  222 ″ that are formed integrally with a corresponding one of the opposite side faces of the tongue-mounting strips  224 . The tongues  223 ″ of the rearwardly-extending tongue units  223  are aligned respectively with the tongues  222 ″ of the frontwardly-extending tongue units  222 . Preferably, the tongues  223 ″,  222 ″ are constructed as ribs.  
     [0021] Since the blade bodies  21  are hollow, and are made from a thermoplastic elastomer, in case a person accidentally touches the same during rotation of the fan unit, only minor injury will be caused to the person. The object of the present invent is thus achieved.  
     [0022] With this invention thus explained, it is apparent that numerous modifications and variations can be made without departing from the scope and spirit of this invention. It is therefore intended that this invention be limited only as indicated by the appended claims.