Methods and apparatus for preventing moisture in fan motor housings

This application claims the benefit of U.S. Provisional Application No. 60/173,160, filed Dec. 27, 1999.

This application relates generally to fans and, more particularly, to fan shrouds for use with fans.

Fan assemblies typically include a fan, a motor, a fan control, and a motor housing. The fan motor and control are positioned within the motor housing and control the energization and rotation of the fan. Because the fan assemblies are often used in applications in which condensation and moisture accumulate, the fan control sometimes fails as a result of exposure to moisture.

To prevent such failures, typically the fan control is covered with a moisture resistant potting material and the motor housing is fabricated with drain holes. However, as air flows over such drain holes, a negative pressure develops within the motor housing that causes air and moisture to be drawn into the motor housing from the environment. Over time, continued exposure to the moisture and airflow causes the potting material to erode, allowing the moisture to contact the fan and motor control. As a result, frequent maintenance is scheduled to prevent such fan assemblies from failing.

In an exemplary embodiment, a fan assembly includes a shroud attached to a motor housing to prevent negative pressure from developing within the motor housing and thus, prevent moisture from being drawn into drain openings. The fan assembly includes a fan, a motor, a motor housing, and a fan control. The motor and fan control are disposed within the motor housing and the fan extends from an upstream portion of the motor housing. The motor housing includes a plurality of drain openings that permit moisture to drain to the environment from the motor housing. The shroud is attached downstream from the fan to the motor housing and is attached co-axially to the motor housing such that the drain openings remain open to the environment.

During operation, air exiting the fan passes over the shroud and is directed downstream. The shroud prevents negative pressure from developing within the motor housing and thus, prevents any moisture from being drawn into the motor housing through the motor housing openings. Additionally, any condensation that develops within the motor housing is permitted to drain through the motor housing drain openings. As a result, a fan assembly is provided that is reliable and cost-effective.

FIG. 1 is an exploded perspective view of a fan assembly including a shroud; and

FIG. 2 is a side elevational view of the assembled fan assembly shown in FIG. 1 .

FIG. 1 is an exploded perspective view of a fan assembly 10 and FIG. 2 is a side elevational view of assembled fan assembly 10 . Fan assembly 10 includes a motor (not shown), a fan 12 , a motor housing 14 , and a shroud 16 . The motor and fan control are disposed within motor housing 14 and control energization and rotation of fan 12 about an axis of rotation 20 .

Motor housing 14 includes a rotating first body 22 and a stationary second body 24 . Rotating first body 22 is substantially cylindrical and includes a top (not shown), a side wall 26 , and a bottom flange 28 . Side wall 26 extends substantially perpendicularly from the top to bottom flange 28 . Rotating first body 22 has a diameter (not shown) measured with respect to side wall 26 that is constant from the top to bottom flange 28 . Bottom flange 28 extends radially outward from side wall 26 and has a diameter (not shown) larger than the diameter of rotating first body 22 measured with respect to side wall 26 . Bottom flange 28 permits rotating first body 22 to be in sealable and rotating contact with stationary second body 24 .

Fan 12 extends from rotating first body 22 and includes a plurality of fan blades 40 extending outward from rotating first body 22 . Each fan blade 40 includes a root 42 attached to rotating first body 22 , a tip 44 , and a body 46 extending between fan root 42 and fan tip 44 .

Motor housing stationary second body 24 is substantially cylindrical and includes a bottom 50 , a side wall 52 , and a top flange 54 . Bottom 50 is substantially flat and side wall 52 extends substantially perpendicularly from bottom 50 to top flange 54 . Stationary second body 24 has a diameter 56 measured with respect to side wall 52 that is constant from bottom 50 to top flange 54 . Top flange 54 extends radially outward from side wall 52 and has a diameter (not shown) larger than stationary second body diameter 56 measured with respect to side wall 52 . Top flange 54 is sized to permit stationary second body 24 to rotatably attach to rotating first body 22 .

Stationary second body 24 includes a plurality of openings 60 extending through stationary second body bottom 50 and a snap fit (not shown). Openings 60 permit moisture to drain from motor housing 14 to the environment. The snap fit extends circumferentially around an inner surface (not shown) of stationary second body 24 and permits motor housing rotating first body 22 to snap-fit to motor housing stationary second body 24 . A connector interface opening 61 is also disposed within stationary second body 24 .

Shroud 16 has a height 70 between a top edge 72 of shroud 16 and a bottom 74 of shroud 16 . Shroud bottom 74 extends circumferentially and curves to top edge 72 . A diameter 76 of shroud 16 measured with respect to top edge 72 is approximately the same size as motor housing stationary second body diameter 56 . Accordingly, when shroud 16 is attached co-axially with motor housing 14 , a shroud outer surface 78 is substantially co-planar with an outer surface 80 of motor housing stationary second body 24 while shroud bottom 74 and top edge 72 are substantially perpendicular to motor housing stationary second body side wall 52 . Additionally, when shroud 16 is attached to motor housing 14 , openings 60 remain open to the environment to permit moisture and condensation to drain from motor housing 14 .

A fan orifice 90 extends from motor housing 14 and permits fan assembly 10 to mount within a component (not shown) without fan assembly 10 contacting the component. In one embodiment, the component is a refrigerator assembly. Fan orifice 90 includes a ring shroud portion 92 and a support portion 94 . Ring shroud portion 92 is generally circular and includes a cylindrical portion 96 and a flange 98 . Cylindrical portion 96 extends substantially perpendicularly from flange 98 and has a diameter 100 larger than a diameter 102 of fan 12 . Flange 98 is substantially flat and includes a plurality of slots 110 extending circumferentially inward from an outer edge 112 of flange 98 . Slots 110 provide openings for fasteners (not shown) to secure fan assembly 10 within the component.

Fan orifice support portion 94 includes a plurality of legs 120 extending between ring shroud portion flange 98 and motor housing stationary second body 24 . In one embodiment, fan orifice support portion 94 includes three legs 120 spaced circumferentially around ring shroud portion flange 98 and motor stationary second body 24 . Support legs 120 extend substantially perpendicularly from fan orifice support portion 94 and bend to attach substantially perpendicularly to motor housing stationary second body 24 . Support portion 94 secures fan orifice 90 to motor housing 14 .

In operation, shroud 16 is attached to motor housing bottom flange 28 such that shroud 16 is substantially co-axial with motor housing 14 . As fan 12 rotates, fan blades 40 rotate simultaneously with motor housing rotating first body 22 . Air is drawn into fan orifice 90 through fan 12 and expelled axially outward to pass over motor housing stationary second body 24 . Without shroud 16 attached to motor housing bottom flange 28 , a negative pressure develops within motor housing 14 and moisture and air are drawn through openings 60 and connector interface opening 61 into motor housing 14 . When shroud 16 is attached to motor housing bottom flange 28 , shroud 16 prevents negative pressure from developing within motor housing 14 . Instead, shroud 16 directs the air downstream and prevents air and moisture from being drawn through openings 60 and connector interface opening 61 .

The above described fan assembly is cost effective and reliable. The fan assembly includes a shroud attached to a motor housing downstream from the fan. The motor housing includes a plurality of openings that permit moisture to drain from the motor housing to the environment. The shroud attaches co-axially to the motor housing such that the openings are remain open to the environment. When attached, the shroud prevents negative pressure from developing within the motor housing as the fan operates and thus, moisture and air are not drawn into the motor housing. As a result, the fan assembly provided is more reliable and cost-effective than known fan assemblies.

While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.