Bearing bore construction for fan end bracket

A motor fan bracket is molded of a fiber reinforced thermoset polyester. The motor/fan bracket has an annular frame and an annular bearing housing concentric with the frame and supported by inwardly extending arms. The annular bearing housing has a bearing-receiving cavity configured in cross section as an equilateral polygon such that each face of that cavity is tangential to a bearing received therein.

TECHNICAL FIELD 
The invention herein resides in the art of fan and motor assemblies. More 
particularly, the invention relates to a bearing bore within a fan end 
bracket for a motor/fan assembly. Specifically, the invention relates to 
such a bearing bore for use in molded reinforced thermoset brackets. 
BACKGROUND ART 
It is well known that in motor/fan assemblies, a motor/fan shaft is 
typically maintained within a bearing received within a bore in the fan 
end bracket. In the past, such fan end brackets have typically been of 
metal construction, formed by a stamping or metal die casting process. 
Similarly, the cup adapted for receiving the bearing has typically been 
pressed or stamped into a support member that traverses an end of the fan 
end bracket. Bearing-receiving cups or receptacles have typically been 
accurately formed by the press or stamping process. Accordingly, the 
bearing can be easily placed into its receptacle during the manufacturing 
and motor assembly process. 
Recently, it has become desirable to form many of the structural components 
of motors from molded plastics. It has particularly become known to employ 
thermoset plastics for that purposes. However, shrinkage and the like 
which is experienced when a molded piece cools or is cured often results 
in distortion of various features on the molded part. Specifically, when 
using fiberglass reinforced thermoset polyester, it has been found that 
the bearing cup at the end of the fan end bracket is given to distortion 
during the cooling/curing process of the thermoset material unless great 
care is given in the manufacturing process. When the bore is made as a 
complete cylindrical bore, defined by a cylindrical wall, the bore often 
deforms to an elliptical or egg shape in cross section, rather than a 
circular configuration as is necessary for receiving the bearing. As a 
consequence, there is a high rejection rate of such molded fan end 
brackets, while even those which might be acceptable require significant 
reworking. Simply stated, the rejection rate or the rework rate of such 
molded fan end brackets has been found to be undesirably high. Moreover, 
with the wall of the bearing bore being designed to make total 
circumferential contact with the bearing, the necessary rework to attain 
that constant receipt is significant. 
While the molding of fan end brackets and other motor/fan assembly parts 
from thermoset materials is highly desirable, the rejection or rework rate 
for such parts often negates the benefits achieved over the prior art 
metal stamped or die castparts. Notably, the primary area of concern with 
respect to the fan end bracket is that the bearing bore be sufficiently 
configured to nestingly receive the bearing during the manufacturing 
process. The other problems inherent with the plastic molding process have 
been less egregious. 
In view of the foregoing, it is most desirable that a molded thermoplastic 
fan end bracket be devised that has either a uniformly formed bearing 
receptacle, or one which has minimal distortions which are easily 
reworked. 
DISCLOSURE OF INVENTION 
In light of the foregoing, it is a first aspect of the invention to present 
a bearing bore construction for a fan end bracket in which the fan end 
bracket is molded of fiberglass reinforced thermoset polyester. 
Another aspect of the invention is the provision of a bearing bore 
construction for a fan end bracket which has a significantly reduced 
likelihood of distortion during the molding process as compared to prior 
art techniques and structures. 
Still a further aspect of the invention is the provision of a bearing bore 
construction for a fan end bracket in which any distortions which might 
arise within the bore as a consequence of the molding process may be 
readily corrected. 
Still a further aspect of the invention is the provision of a bearing bore 
construction for a fan end bracket in which the bore is shaped in the form 
of an equilateral polygon in cross section, rather than a circle. 
Yet an additional aspect of the invention is the provision of a bearing 
bore construction for a fan end bracket which is reliable and durable in 
operation, increases production efficiencies, and is readily capable of 
implementation with state of the art apparatus and techniques. 
The foregoing an other aspects of the invention which will become apparent 
as the detailed description proceeds are achieved by a motor/fan end 
bracket having a bearing cup, comprising: an annular frame; and an annular 
bearing housing maintained centrally of said annular frame, said annular 
bearing housing having a cup-shaped cavity defined by a multifaceted wall 
having an aperture at an end thereof. 
Still further aspects of the invention which will become apparent herein 
are attained by a motor/fan bracket, comprising: an annular frame; an 
annular bearing housing concentric with said annular frame; support arms 
extending inwardly from said annular frame and securedly maintaining said 
annular bearing housing, said annular frame, annular bearing housing and 
support arms being molded of a thermoset plastic; and wherein said annular 
bearing housing has a bearing-receiving cavity configured in cross section 
as an equilateral polygon, each face of said equilateral polygon being 
tangential to a common cylinder.

BEST MODE FOR CARRYING OUT THE INVENTION 
Referring now to the drawing and more particularly to FIG. 1, it can be 
seen that a fan end bracket made in accordance with the invention is 
designated generally by the numeral 10. It will be appreciated that the 
fan end bracket 10 as viewed from the bottom thereof is shown in FIG. 1. 
Those skilled in the art will readily appreciate that the fan end bracket 
10 is adapted to mate with a motor housing and receive a fan shroud 
enclosing an appropriate fan of any desired structure. In accordance with 
the present invention, the fan end bracket 10 is molded of fiberglass 
reinforced thermoset polyester. However, the concept of the invention is 
intended to extend to any of a broad range of thermoset plastics. 
As shown in FIG. 1, the fan end bracket 10 consists of an annular frame 12 
having a pair of diametrically aligned support arms 14 extending therefrom 
and maintaining an annular bearing housing 16 concentric with the annular 
frame 12. Those skilled in the art will readily appreciate that the 
annular bearing housing 16 is intended to maintain a bearing which 
receives a fan and/or motor shaft. For this reason, the annular bearing 
housing 16 and the annular frame 12 are typically coaxially aligned. 
As best shown in FIG. 2, an aperture 18 is provided in an end wall of the 
annular bearing housing 16 for purposes of receiving a fan and/or motor 
shaft. 
As best shown in FIGS. 2 and 3, the annular bearing housing 16 includes a 
cup-shaped cavity 20 defined by multifaceted wall 22. The facets 24 of the 
wall 22 are molded to be of identical shape and configuration. In the 
preferred embodiment of the invention, the wall 22 is defined by 12 such 
facets, such that the wall or cavity 20, taken in cross section, defines a 
twelve sided equilateral polygon. With the polygon being equilateral, the 
axial centerline of each of the facets 24 lies on a common cylinder such 
than when a cylindrical bearing is placed within the cup-shaped cavity 20, 
it preferably tangentially engages each of the facets 24 at that 
centerline. Accordingly, there are twelve lines of tangential contact with 
the cylindrical bearing. 
With reference now to FIGS. 2 and 3, it can be seen that a tapered or 
funnel shaped mouth 26 feeds into the cup-shaped cavity 20 at the major 
opening thereof. This tapered or funnel shaped mouth accommodates 
insertion of the cylindrical shaped bearing into the cavity 20. Moreover, 
with there being only twelve lines of contact between the bearing and the 
twelve facets 24, any irregularities within the facets may be somewhat 
easily accommodated as a bearing is pressed thereinto. Moreover, if the 
distortion of any of the facets 24 is such that the cavity 20 will not 
receive the bearing, only the distorted facets need to be reworked at the 
point of assembly. In other words, the cavity itself does not elongate or 
assume an elliptical or egg-shaped configuration, but remains 
substantially cylindrical in form, requiring only minor rework of selected 
facets. 
With further reference to FIG. 2, it can be seen the bearing is adapted to 
rest upon an inner annular flange 28 and a recessed outer annular flange 
30. These flanges, in conjunction with multifaceted wall 22, provide for 
nesting engagement of the bearing within the cavity so defined. 
It will also be noted that the aperture 18, defined by the outer annular 
flange 30, also has a tapered funnel shaped mouth 32, sloped inwardly 
toward the aperture 18 for guidance and ease of placement of motor and/or 
fan shaft. 
Those skilled in the art will readily appreciate that tuning and/or 
reworking of the cavity wall is greatly facilitated by the presence of a 
wall which is multifaceted, rather than one which is intended to be of a 
totally circular or cylindrical nature. Moreover, it has been found that 
any distortions resulting from the molding process are greatly reduced by 
employing the multifaceted wall feature. Those which do occur are easily 
reworked or otherwise corrected as a result of that same structure. 
Those skilled in the art will readily appreciate that the number of facets 
24 in the wall 22 may vary with design. In accordance with the preferred 
embodiment of the invention, at least eight such facets are desired for a 
typical motor/fan assemblies as used in vacuum devices and the like. 
For the particular adaptation shown in the drawing, twelve such facets are 
employed. In general, the greater the number of facets, the smaller each 
facet is and, as a consequence, the more isolated any distortion will be 
and the easier it will be to correct. 
Thus it can be seen that the objects of the invention have been satisfied 
by the structure presented above. While in accordance with the patent 
statutes only the best mode and preferred embodiment of the invention has 
been presented and described in detail, it will be understood that the 
invention is not limited thereto or thereby. Accordingly, for an 
appreciation of the true scope and breadth of the invention reference 
should be made to the following claims.