Abstract:
A fan retention system for a blower/vacuum securely retains the fan and creates an insulating barrier to prevent the operator from touching the functionally insulated armature shaft. A nut having interlocking ramps for interlocking with interconnecting portions on an abutting fan surface is provided. The interconnecting portions of the fan may be either ramps or recesses. Furthermore, the nut has a closed end for insulating the armature shaft from the operator.

Description:
This application claims benefit to U.S. provisional application Ser. No. 60/075,310, filed Feb. 20, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an improved system for securing a fan to a drive shaft. In particular, the system is useful for securing fans in blower/vacuum systems used for vacuuming or blowing debris, such as leaves and grass clippings, from a lawn or other ground surface. 
     2. Background of Related Art 
     Although applicable in a variety of environments, the securing system of the invention is especially useful for securing a fan to an armature shaft in a blower or blower/vacuum. Various systems are known in the art for securing a fan to a drive shaft within the blower/vacuum environment. In such environments, a fan is mounted to a drive shaft for rotation. In the vacuum configuration, spaced fan blades allow a range of debris to pass through them to an outlet and generally to a collection apparatus. In the blower configuration, a discharge tube may be connected to the outlet to discharge exhaust air. 
     A known system is shown in FIG. 2. A centrally aligned mounting boss includes interior bores and which receive the end of a drive shaft to form an interference fit. An additional known configuration involves providing a standard nut at the end of the armature shaft. Difficulties encountered with these and other known configurations include the awkward shape of the fan creating balancing difficulties within the mold, slipping of the armature within the interior fan bores, and loosening of the standard nut. Additionally, the use of a standard nut requires relatively costly insulation between the armature and the armature shaft in order to double insulate the touchable parts. 
     Plastic parts tend to creep over time and as a result of moisture and temperature variations. Accordingly, prior art systems, which involve tightening an ordinary plastic nut are often inadequate because the nut tends to loosen. 
     SUMMARY OF THE INVENTION 
     Objects of the invention include the provision of a fan securing system that provides a securely mounted fan, an insulating barrier that prevents the operator from touching the armature shaft, and a fan shape that balances well within a mold. 
     These and other objects are achieved by providing a fan securing system for securing a fan onto an armature shaft. The securing system comprises a nut having a central aperture through a first surface. The first surface includes a series of ramps spaced around the central aperture. Internally molded threads within the central aperture engage the armature shaft. A first fan surface portion comprises a central aperture through which the armature shaft passes and a series of interruptions configured to interlock with the series of ramps on the nut. The interruptions may comprise recesses or mating ramps. 
     The objects are further achieved by providing a blower/vacuum for selective operation in blower mode and suction mode, the blower/vacuum comprising an armature shaft and a fan mounted on the armature shaft through a central aperture. The fan comprises a first fan surface portion having a series of interruptions. A nut having a central aperture through a first surface is provided. The aperture has internally molded threads that engage the armature shaft. A series of ramps is spaced around the central aperture. The ramps are configured to interlock with interruptions on the first fan surface portion. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     The foregoing aspects and specific embodiments of the invention are disclosed in the detailed description in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a sectional view of an embodiment of the fan securing system of the invention in its assembled form; 
     FIG. 2 is a sectional view of a typical blower/vacuum apparatus; 
     FIG. 3 is a cross-sectional view of the armature shaft of an embodiment of the invention; 
     FIG. 4 is a cross-sectional view of the washer of an embodiment of the invention; 
     FIG.  5 ( a ) is a top plan view of the insulating nut; 
     FIG.  5 ( b ) is a sectional view of an embodiment of the insulating nut; 
     FIG.  5 ( c ) is a detail of FIG.  5 ( b ); 
     FIG.  5 ( d ) is a bottom plan view of the insulating nut; 
     FIG.  6 ( a ) is a top plan view of a fan of the invention; 
     FIG.  6 ( b ) is a bottom plan view of the fan of FIG. 6 ( a ); 
     FIG.  6 ( c ) is a detail of the bottom plan view of FIG.  6 ( b ); 
     FIG.  7 ( a ) is a sectional view of an embodiment of the fan; 
     FIG.  7 ( b ) is a detail of FIG.  7 ( a ); 
     FIG.  8 ( a ) is a sectional view of an embodiment of the fan; 
     FIG.  8 ( b ) is a detail of FIG.  8 ( a ); 
     FIG.  9 ( a ) is a sectional view of the fan and nut of an embodiment of the invention; 
     FIG.  9 ( b ) is a sectional view of the fan and nut of an embodiment of the invention; and 
     FIG. 10 is a sectional view of an alternative embodiment. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 2 illustrates a typical blower/vac configuration. The configuration comprises motor unit  104  and vacuum volute  106 . The motor unit  104  comprises motor  110  that drives a shaft  112 . A fan  114  is mounted on the shaft so that it may be driven by motor  110 . The motor unit  104  further includes handle arrangement  120 . 
     Vacuum volute  106  comprises a suction duct  124  and expelling duct  122 . The vacuum volute  106  is shaped to accommodate fan  114 . In use, air is drawn in through suction duct  124  and expelled through expelling duct  122 . 
     A porous collecting bag (not shown) may be releasably attachable to the end of expelling duct  122  distant from fan  114 . Vacuum volute  106  is releasably attachable to motor unit  104 . An extension tube (not shown) may be releasably attachable to the end of the suction duct  124  remote from fan  114 . In this particular prior art arrangement the fan is pressed onto the shaft. 
     The present invention relates to an improved assembly that secures the fan to the armature shaft. FIG. 1 is a sectional view of an embodiment of the fan securing system of the invention in its assembled form. Armature shaft  16  extends outwardly from motor  12  and through a central bore  15  in fan  14 . The central bore  15  may be a double “D” shaped bore, as is more clearly shown in FIG.  6 ( b ). A washer  18  is provided at the juncture of fan  14  and armature shaft  16 . Insulated nut  40  secures fan  14  to armature shaft  16 . Surface  41  of insulating nut  40  abuts surface  43  of fan  14  to create interface  42 , which is described in more detail with reference to FIGS. 5-8. 
     As shown in FIG. 4, washer  18  is provided with flats  18   a  and  18   b  to provide a thrust surface that gives axial location to the fan. FIG. 3 illustrates a corresponding part of armature shaft  16 , having flats  16   a  and  16   b.  These flats are located on the portion of the armature where it passes through the fan in order to locate the fan rotationally. 
     FIG. 10 illustrates an additional preferred embodiment of the invention in which washer  18  is replaced with a combination of spacer  19 , ball bearing  20  and retaining ring  21 . When washer  18  is used, the shaft  16  requires a flattened portion through the length of the fan hub. The alternative arrangement shown in FIG. 10 eliminates this necessity. The fan and nut configurations shown in FIGS. 3 through 9 can be utilized with both the arrangement shown in FIG.  1  and the arrangement shown in FIG.  10 . 
     FIGS.  5 ( a )- 5 ( d ) show the nut of the invention. The nut is preferably made of plastic and serves the function of insulating the armature shaft. FIG.  5 ( a ) is a top plan view of the insulating nut. In this instance “top” refers to the top of the nut as viewed from its position in FIG.  2 . The nut includes a plurality of interlocking ramps  44  spaced around central bore  45  of the nut. In the embodiment illustrated in FIG.  5 ( a ), six interlocking ramps are evenly spaced within the perimeter of nut  40 . 
     FIG.  5 ( b ) is a sectional view that shows internal threads  46  within bore hole  45  of the nut. Bottom surface  48  of the nut insulates the armature shaft. Interlocking ramps  44  are clearly shown in FIG.  5 ( c ). In an embodiment of the invention, angle ‘a’ of the interlocking ramps is between about 2 and 15 degrees. In a preferred embodiment, the angle a is about 8 degrees. Distance b is the distance of the furthest point of ramps  44  from nut surface  41 . 
     While the periphery of surface  41  may be circular in shape, the surface portion  48  extending downwardly from portion  41  may include multiple flat surfaces. As shown in the bottom plan view of FIG.  5 ( d ), surface  48  may be a six sided polygonal shape. 
     FIGS.  6 ( a )- 6 ( c ) illustrate an embodiment of the fan of the invention. FIG.  6 ( a ) is a top plan view of fan  14  showing ten equally spaced cooling blades  51 . FIG.  6 ( b ) is a bottom plan view of fan  14  showing five equally spaced mulching blades  52 . Fan interface  43  includes central bore  15  and locking portions  54 . Locking portions  54  are shown in more detail in FIG.  6 ( c ). In one preferred embodiment the locking portions are equally spaced at approximately twenty-eight degrees apart on fan interface  43 . 
     FIGS.  7 ( a ) and  7 ( b ) further illustrate a preferred fan configuration. Interlocking portions  54  are recesses having a depth c as shown in FIG.  7 ( b ) that is approximately equal to the height b of the nut interlocking portions as shown in FIG.  5 ( c ). This configuration enables the nut to interlock with the fan to create a secure connection. FIG.  7 ( b ) is a sectional view illustrating interlocking portions  54  along surface  43  of fan  14 . 
     An alternative preferred configuration is shown in FIGS.  8 ( a ) and  8 ( b ). FIGS.  8 ( a ) and  8 ( b ) show interlocking portions  54  of the fan as ramps rather than recesses. 
     FIG.  9 ( a ) is a sectional view showing the interlocking configuration of FIGS.  8 ( a ) and  8 ( b ). Interlocking ramps  44  of nut  40  securely connect with interconnecting portions  154  of fan  14 . Interconnecting portions  154  are in the form of interlocking ramps. 
     FIG.  9 ( b ) is a sectional view showing the interlocking configuration of FIGS.  7 ( a ) and  7 ( b ). Interlocking ramps  44  of nut  40  securely connect with interconnecting portions  54  of fan  14 . Interconnecting portions  54  are in the form of recesses. 
     It should be understood that the foregoing description is merely illustrative and is not intended to be limiting. Various alternatives and modifications may be apparent to those skilled in the art. Accordingly, the invention is intended to encompass all such alternatives, modification, and variations which fall within the scope of the appended claims.